This manual is last updated 27 April 2013 for version 3.0.31 of GnuTLS.
Copyright © 2001-2012 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
Next: Introduction to GnuTLS, Previous: Top, Up: Top [Contents][Index]
This document demonstrates and explains the GnuTLS library API. A brief introduction to the protocols and the technology involved is also included so that an application programmer can better understand the GnuTLS purpose and actual offerings. Even if GnuTLS is a typical library software, it operates over several security and cryptographic protocols which require the programmer to make careful and correct usage of them. Otherwise it is likely to only obtain a false sense of security. The term of security is very broad even if restricted to computer software, and cannot be confined to a single cryptographic library. For that reason, do not consider any program secure just because it uses GnuTLS; there are several ways to compromise a program or a communication line and GnuTLS only helps with some of them.
Although this document tries to be self contained, basic network programming and public key infrastructure (PKI) knowledge is assumed in most of it. A good introduction to networking can be found in [STEVENS], to public key infrastructure in [GUTPKI] and to security engineering in [ANDERSON].
Updated versions of the GnuTLS software and this document will be available from http://www.gnutls.org/ and http://www.gnu.org/software/gnutls/.
Next: Introduction to TLS, Previous: Preface, Up: Top [Contents][Index]
In brief GnuTLS can be described as a library which offers an API to access secure communication protocols. These protocols provide privacy over insecure lines, and were designed to prevent eavesdropping, tampering, or message forgery.
Technically GnuTLS is a portable ANSI C based library which implements the protocols ranging from SSL 3.0 to TLS 1.2 (see Introduction to TLS, for a detailed description of the protocols), accompanied with the required framework for authentication and public key infrastructure. Important features of the GnuTLS library include:
The GnuTLS library consists of three independent parts, namely the “TLS protocol part”, the “Certificate part”, and the “Cryptographic back-end” part. The “TLS protocol part” is the actual protocol implementation, and is entirely implemented within the GnuTLS library. The “Certificate part” consists of the certificate parsing, and verification functions and it uses functionality from the libtasn11 library. The “Cryptographic back-end” is provided by the nettle2 library.
• Downloading and installing: | ||
• Document overview: |
Next: Document overview, Up: Introduction to GnuTLS [Contents][Index]
GnuTLS is available for download at: http://www.gnutls.org/download.html
GnuTLS uses a development cycle where even minor version numbers indicate a stable release and a odd minor version number indicate a development release. For example, GnuTLS 1.6.3 denote a stable release since 6 is even, and GnuTLS 1.7.11 denote a development release since 7 is odd.
GnuTLS depends on Libnettle, and you will need to install it before installing GnuTLS. Libnettle is available from http://www.lysator.liu.se/~nisse/nettle/. Don’t forget to verify the cryptographic signature after downloading source code packages.
The package is then extracted, configured and built like many other
packages that use Autoconf. For detailed information on configuring
and building it, refer to the INSTALL file that is part of the
distribution archive. Typically you invoke ./configure
and
then make check install
. There are a number of compile-time
parameters, as discussed below.
The compression library, libz, as well as p11-kit are a optional dependencies. You can get libz from http://www.zlib.net/ and p11-kit from http://p11-glue.freedesktop.org/.
The X.509 part of GnuTLS needs ASN.1 functionality, from a library called libtasn1. A copy of libtasn1 is included in GnuTLS. If you want to install it separately (e.g., to make it possibly to use libtasn1 in other programs), you can get it from http://www.gnu.org/software/gnutls/download.html.
A few configure
options may be relevant, summarized below.
They disable or enable particular features,
to create a smaller library with only the required features.
Note however, that although a smaller library is generated, the
included programs are not guarranteed to compile if some of these
options are given.
--disable-srp-authentication --disable-psk-authentication --disable-anon-authentication --disable-extra-pki --disable-openpgp-authentication --disable-openssl-compatibility --without-p11-kit
For the complete list, refer to the output from configure --help
.
Previous: Downloading and installing, Up: Introduction to GnuTLS [Contents][Index]
In this document we present an overview of the supported security protocols in Introduction to TLS, and continue by providing more information on the certificate authentication in Certificate authentication, and shared-key as well anonymous authentication in Shared-key and anonymous authentication. We elaborate on certificate authentication by demonstrating advanced usage of the API in More on certificate authentication. The core of the TLS library is presented in How to use GnuTLS in applications and example applications are listed in GnuTLS application examples. In Other included programs the usage of few included programs that may assist debugging is presented. The last chapter is Internal architecture of GnuTLS that provides a short introduction to GnuTLS’ internal architecture.
Next: Certificate authentication, Previous: Introduction to GnuTLS, Up: Top [Contents][Index]
TLS stands for “Transport Layer Security” and is the successor of SSL, the Secure Sockets Layer protocol [SSL3] designed by Netscape. TLS is an Internet protocol, defined by IETF3, described in [RFC5246]. The protocol provides confidentiality, and authentication layers over any reliable transport layer. The description, above, refers to TLS 1.0 but applies to all other TLS versions as the differences between the protocols are not major.
The DTLS protocol, or “Datagram TLS” [RFC4347] is a protocol with identical goals as TLS, but can operate under unreliable transport layers such as UDP. The discussions below apply to this protocol as well, except when noted otherwise.
Next: The transport layer, Up: Introduction to TLS [Contents][Index]
TLS is a layered protocol, and consists of the record protocol, the handshake protocol and the alert protocol. The record protocol is to serve all other protocols and is above the transport layer. The record protocol offers symmetric encryption, data authenticity, and optionally compression. The alert protocol offers some signaling to the other protocols. It can help informing the peer for the cause of failures and other error conditions. See The Alert Protocol, for more information. The alert protocol is above the record protocol.
The handshake protocol is responsible for the security parameters’ negotiation, the initial key exchange and authentication. See The Handshake Protocol, for more information about the handshake protocol. The protocol layering in TLS is shown in Figure 3.1.
Next: The TLS record protocol, Previous: TLS layers, Up: Introduction to TLS [Contents][Index]
TLS is not limited to any transport layer and can be used above any transport layer, as long as it is a reliable one. DTLS can be used over reliable and unreliable transport layers. GnuTLS supports TCP and UDP layers transparently using the Berkeley sockets API. However, any transport layer can be used by providing callbacks for GnuTLS to access the transport layer (for details see Setting up the transport layer).
Next: The TLS Alert Protocol, Previous: The transport layer, Up: Introduction to TLS [Contents][Index]
The record protocol is the secure communications provider. Its purpose is to encrypt, authenticate and —optionally— compress packets. The record layer functions can be called at any time after the handshake process is finished, when there is need to receive or send data. In DTLS however, due to re-transmission timers used in the handshake out-of-order handshake data might be received for some time (maximum 60 seconds) after the handshake process is finished.
The functions to access the record protocol are limited to send and receive functions, which might, given the importance of this protocol in TLS, seem awkward. This is because the record protocol’s parameters are all set by the handshake protocol. The record protocol initially starts with NULL parameters, which means no encryption, and no MAC is used. Encryption and authentication begin just after the handshake protocol has finished.
• Encryption algorithms used in the record layer: | ||
• Compression algorithms used in the record layer: | ||
• Weaknesses and countermeasures: | ||
• On Record Padding: |
Next: Compression algorithms used in the record layer, Up: The TLS record protocol [Contents][Index]
Confidentiality in the record layer is achieved by using symmetric
block encryption algorithms like 3DES
, AES
or stream algorithms like ARCFOUR_128
.
Ciphers are encryption algorithms that use a single, secret,
key to encrypt and decrypt data. Block algorithms in CBC mode also provide
protection against statistical analysis of the data. Thus, if you’re
using the TLS protocol, a random number of blocks will be
appended to data, to prevent eavesdroppers from guessing the actual
data size.
The supported in GnuTLS ciphers and MAC algorithms are shown in Table 3.1 and Table 3.2.
Algorithm | Description |
---|---|
3DES_CBC | This is the DES block cipher algorithm used with triple encryption (EDE). Has 64 bits block size and is used in CBC mode. |
ARCFOUR_128 | ARCFOUR_128 is a compatible algorithm with RSA’s RC4 algorithm, which is considered to be a trade secret. It is a fast cipher but considered weak today. |
ARCFOUR_40 | This is the ARCFOUR cipher fed with a 40 bit key, which is considered weak. |
AES_CBC | AES or RIJNDAEL is the block cipher algorithm that replaces the old DES algorithm. Has 128 bits block size and is used in CBC mode. |
AES_GCM | This is the AES algorithm in the authenticated encryption GCM mode. This mode combines message authentication and encryption and can be extremely fast on CPUs that support hardware acceleration. |
CAMELLIA_CBC | This is an 128-bit block cipher developed by Mitsubishi and NTT. It is one of the approved ciphers of the European NESSIE and Japanese CRYPTREC projects. |
Table 3.1: Supported ciphers.
Algorithm | Description |
---|---|
MAC_MD5 | This is an HMAC based on MD5 a cryptographic hash algorithm designed by Ron Rivest. Outputs 128 bits of data. |
MAC_SHA1 | An HMAC based on the SHA1 cryptographic hash algorithm designed by NSA. Outputs 160 bits of data. |
MAC_SHA256 | An HMAC based on SHA256. Outputs 256 bits of data. |
MAC_AEAD | This indicates that an authenticated encryption algorithm, such as GCM, is in use. |
Table 3.2: Supported MAC algorithms.
Next: Weaknesses and countermeasures, Previous: Encryption algorithms used in the record layer, Up: The TLS record protocol [Contents][Index]
The TLS record layer also supports compression. The algorithms implemented in GnuTLS can be found in the table below. The included algorithms perform really good when text, or other compressible data are to be transferred, but offer nothing on already compressed data, such as compressed images, zipped archives etc. These compression algorithms, may be useful in high bandwidth TLS tunnels, and in cases where network usage has to be minimized. It should be noted however that compression increases latency.
The record layer compression in GnuTLS is implemented based on [RFC3749]. The supported algorithms are shown below.
GNUTLS_COMP_UNKNOWN
Unknown compression method.
GNUTLS_COMP_NULL
The NULL compression method (no compression).
GNUTLS_COMP_DEFLATE
The DEFLATE compression method from zlib.
GNUTLS_COMP_ZLIB
Same as GNUTLS_COMP_DEFLATE
.
Figure 3.2: Supported compression algorithms
Note that compression enables attacks such as traffic analysis, or even plaintext recovery under certain circumstances. To avoid some of these attacks GnuTLS allows each record to be compressed independently (i.e., stateless compression), by using the "%STATELESS_COMPRESSION" priority string.
Next: On Record Padding, Previous: Compression algorithms used in the record layer, Up: The TLS record protocol [Contents][Index]
Some weaknesses that may affect the security of the record layer have been found in TLS 1.0 protocol. These weaknesses can be exploited by active attackers, and exploit the facts that
Those weaknesses were solved in TLS 1.1 [RFC4346] which is implemented in GnuTLS. For this reason we suggest to always negotiate the highest supported TLS version with the peer4. For a detailed discussion of the issues see the archives of the TLS Working Group mailing list and [CBCATT].
Previous: Weaknesses and countermeasures, Up: The TLS record protocol [Contents][Index]
The TLS protocol allows for random padding of records in CBC ciphers, to prevent statistical analysis based on the length of exchanged messages (see [RFC5246] section 6.2.3.2). GnuTLS appears to be one of few implementation that take advantage of this text, and pad records by a random length.
The TLS implementation in the Symbian operating system, frequently
used by Nokia and Sony-Ericsson mobile phones, cannot handle
non-minimal record padding. What happens when one of these clients
handshake with a GnuTLS server is that the client will fail to compute
the correct MAC for the record. The client sends a TLS alert
(bad_record_mac
) and disconnects. Typically this will result
in error messages such as ’A TLS fatal alert has been received’, ’Bad
record MAC’, or both, on the GnuTLS server side.
GnuTLS implements a work around for this problem. However, it has to
be enabled specifically. It can be enabled by using
gnutls_record_disable_padding, or gnutls_priority_set with
the %COMPAT
priority string (see Priority Strings).
If you implement an application that have a configuration file, we recommend that you make it possible for users or administrators to specify a GnuTLS protocol priority string, which is used by your application via gnutls_priority_set. To allow the best flexibility, make it possible to have a different priority string for different incoming IP addresses.
Next: The TLS Handshake Protocol, Previous: The TLS record protocol, Up: Introduction to TLS [Contents][Index]
The alert protocol is there to allow signals to be sent between peers.
These signals are mostly used to inform the peer about the cause of a
protocol failure. Some of these signals are used internally by the
protocol and the application protocol does not have to cope with them
(e.g. GNUTLS_A_CLOSE_NOTIFY
), and others refer to the
application protocol solely (e.g. GNUTLS_A_USER_CANCELLED
). An
alert signal includes a level indication which may be either fatal or
warning. Fatal alerts always terminate the current connection, and
prevent future re-negotiations using the current session ID. All alert
messages are summarized in the table below.
The alert messages are protected by the record protocol, thus the information that is included does not leak. You must take extreme care for the alert information not to leak to a possible attacker, via public log files etc.
Next: TLS Extensions, Previous: The TLS Alert Protocol, Up: Introduction to TLS [Contents][Index]
The handshake protocol is responsible for the ciphersuite negotiation, the initial key exchange, and the authentication of the two peers. This is fully controlled by the application layer, thus your program has to set up the required parameters. The main handshake function is gnutls_handshake. In the next paragraphs we elaborate on the handshake protocol, i.e., the ciphersuite negotiation.
• TLS Cipher Suites: | TLS session parameters. | |
• Authentication: | TLS authentication. | |
• Client Authentication: | Requesting a certificate from the client. | |
• Resuming Sessions: | Reusing previously established keys. |
Next: Authentication, Up: The TLS Handshake Protocol [Contents][Index]
The handshake protocol of TLS negotiates cipher suites of
a special form illustrated by the TLS_DHE_RSA_WITH_3DES_CBC_SHA
cipher suite name. A typical cipher
suite contains these parameters:
DHE_RSA
in the example.
3DES_CBC
in this example.
MAC_SHA
is used in the above example.
The cipher suite negotiated in the handshake protocol will affect the record protocol, by enabling encryption and data authentication. Note that you should not over rely on TLS to negotiate the strongest available cipher suite. Do not enable ciphers and algorithms that you consider weak.
All the supported ciphersuites are listed in ciphersuites.
Next: Client Authentication, Previous: TLS Cipher Suites, Up: The TLS Handshake Protocol [Contents][Index]
The key exchange algorithms of the TLS protocol offer authentication, which is a prerequisite for a secure connection. The available authentication methods in GnuTLS follow.
Next: Resuming Sessions, Previous: Authentication, Up: The TLS Handshake Protocol [Contents][Index]
In the case of ciphersuites that use certificate authentication, the authentication of the client is optional in TLS. A server may request a certificate from the client using the gnutls_certificate_server_set_request function. We elaborate in Certificate credentials.
Previous: Client Authentication, Up: The TLS Handshake Protocol [Contents][Index]
The TLS handshake process performs expensive calculations and a busy server might easily be put under load. To reduce the load, session resumption may be used. This is a feature of the TLS protocol which allows a client to connect to a server after a successful handshake, without the expensive calculations. This is achieved by re-using the previously established keys, meaning the server needs to store the state of established connections (unless session tickets are used – Session tickets).
Session resumption is an integral part of GnuTLS, and Session resumption and ex:resume-client illustrate typical uses of it.
Next: How to use TLS in application protocols, Previous: The TLS Handshake Protocol, Up: Introduction to TLS [Contents][Index]
A number of extensions to the TLS protocol have been proposed mainly in [TLSEXT]. The extensions supported in GnuTLS are:
and they will be discussed in the subsections that follow.
• Maximum fragment length negotiation: | ||
• Server name indication: | ||
• Session tickets: | ||
• Safe renegotiation: |
Next: Server name indication, Up: TLS Extensions [Contents][Index]
This extension allows a TLS implementation to negotiate a smaller value for record packet maximum length. This extension may be useful to clients with constrained capabilities. The functions shown below can be used to control this extension.
size_t gnutls_record_get_max_size (gnutls_session_t session)
ssize_t gnutls_record_set_max_size (gnutls_session_t session, size_t size)
Next: Session tickets, Previous: Maximum fragment length negotiation, Up: TLS Extensions [Contents][Index]
A common problem in HTTPS servers is the fact that the TLS protocol is not aware of the hostname that a client connects to, when the handshake procedure begins. For that reason the TLS server has no way to know which certificate to send.
This extension solves that problem within the TLS protocol, and allows a client to send the HTTP hostname before the handshake begins within the first handshake packet. The functions gnutls_server_name_set and gnutls_server_name_get can be used to enable this extension, or to retrieve the name sent by a client.
int gnutls_server_name_set (gnutls_session_t session, gnutls_server_name_type_t type, const void * name, size_t name_length)
int gnutls_server_name_get (gnutls_session_t session, void * data, size_t * data_length, unsigned int * type, unsigned int indx)
Next: Safe renegotiation, Previous: Server name indication, Up: TLS Extensions [Contents][Index]
To resume a TLS session the server normally store session parameters. This complicates deployment, and could be avoiding by delegating the storage to the client. Because session parameters are sensitive they are encrypted and authenticated with a key only known to the server and then sent to the client. The Session Tickets in RFC 5077 [TLSTKT], describe this idea, which is implemented in GnuTLS.
Previous: Session tickets, Up: TLS Extensions [Contents][Index]
TLS gives the option to two communicating parties to renegotiate and update their security parameters. One useful example of this feature was for a client to initially connect using anonymous negotiation to a server, and the renegotiate using some authenticated ciphersuite. This occurred to avoid having the client sending its credentials in the clear.
However this renegotiation, as initially designed would not ensure that the party one is renegotiating is the same as the one in the initial negotiation. For example one server could forward all renegotiation traffic to an other server who will see this traffic as an initial negotiation attempt.
This might be seen as a valid design decision, but it seems it was not widely known or understood, thus today some application protocols the TLS renegotiation feature in a manner that enables a malicious server to insert content of his choice in the beginning of a TLS session.
The most prominent vulnerability was with HTTPS. There servers request a renegotiation to enforce an anonymous user to use a certificate in order to access certain parts of a web site. The attack works by having the attacker simulate a client and connect to a server, with server-only authentication, and send some data intended to cause harm. The server will then require renegotiation from him in order to perform the request. When the proper client attempts to contact the server, the attacker hijacks that connection and forwards traffic to the initial server that requested renegotiation. The attacker will not be able to read the data exchanged between the client and the server. However, the server will (incorrectly) assume that the initial request sent by the attacker was sent by the now authenticated client. The result is a prefix plain-text injection attack.
The above is just one example. Other vulnerabilities exists that do not rely on the TLS renegotiation to change the client’s authenticated status (either TLS or application layer).
While fixing these application protocols and implementations would be one natural reaction, an extension to TLS has been designed that cryptographically binds together any renegotiated handshakes with the initial negotiation. When the extension is used, the attack is detected and the session can be terminated. The extension is specified in [RFC5746].
GnuTLS supports the safe renegotiation extension. The default behavior is as follows. Clients will attempt to negotiate the safe renegotiation extension when talking to servers. Servers will accept the extension when presented by clients. Clients and servers will permit an initial handshake to complete even when the other side does not support the safe renegotiation extension. Clients and servers will refuse renegotiation attempts when the extension has not been negotiated.
Note that permitting clients to connect to servers when the safe renegotiation extension is not enabled, is open up for attacks. Changing this default behavior would prevent interoperability against the majority of deployed servers out there. We will reconsider this default behavior in the future when more servers have been upgraded. Note that it is easy to configure clients to always require the safe renegotiation extension from servers.
To modify the default behavior, we have introduced some new priority
strings (see Priority Strings).
The %UNSAFE_RENEGOTIATION
priority string permits
(re-)handshakes even when the safe renegotiation extension was not
negotiated. The default behavior is %PARTIAL_RENEGOTIATION
that will
prevent renegotiation with clients and servers not supporting the
extension. This is secure for servers but leaves clients vulnerable
to some attacks, but this is a trade-off between security and compatibility
with old servers. The %SAFE_RENEGOTIATION
priority string makes
clients and servers require the extension for every handshake. The latter
is the most secure option for clients, at the cost of not being able
to connect to legacy servers. Servers will also deny clients that
do not support the extension from connecting.
It is possible to disable use of the extension completely, in both
clients and servers, by using the %DISABLE_SAFE_RENEGOTIATION
priority string however we strongly recommend you to only do this for
debugging and test purposes.
The default values if the flags above are not specified are:
Server:
%PARTIAL_RENEGOTIATION
Client:
%PARTIAL_RENEGOTIATION
For applications we have introduced a new API related to safe renegotiation. The gnutls_safe_renegotiation_status function is used to check if the extension has been negotiated on a session, and can be used both by clients and servers.
Next: On SSL 2 and older protocols, Previous: TLS Extensions, Up: Introduction to TLS [Contents][Index]
This chapter is intended to provide some hints on how to use the TLS over simple custom made application protocols. The discussion below mainly refers to the TCP/IP transport layer but may be extended to other ones too.
• Separate ports: | ||
• Upward negotiation: |
Traditionally SSL was used in application protocols by assigning a new port number for the secure services. That way two separate ports were assigned, one for the non secure sessions, and one for the secured ones. This has the benefit that if a user requests a secure session then the client will try to connect to the secure port and fail otherwise. The only possible attack with this method is a denial of service one. The most famous example of this method is the famous “HTTP over TLS” or HTTPS protocol [RFC2818].
Despite its wide use, this method is not as good as it seems. This approach starts the TLS Handshake procedure just after the client connects on the —so called— secure port. That way the TLS protocol does not know anything about the client, and popular methods like the host advertising in HTTP do not work6. There is no way for the client to say “I connected to YYY server” before the Handshake starts, so the server cannot possibly know which certificate to use.
Other than that it requires two separate ports to run a single service, which is unnecessary complication. Due to the fact that there is a limitation on the available privileged ports, this approach was soon obsoleted.
Previous: Separate ports, Up: How to use TLS in application protocols [Contents][Index]
Other application protocols7 use a different approach to enable the secure layer. They use something often called as the “TLS upgrade” method. This method is quite tricky but it is more flexible. The idea is to extend the application protocol to have a “STARTTLS” request, whose purpose it to start the TLS protocols just after the client requests it. This approach does not require any extra port to be reserved. There is even an extension to HTTP protocol to support that method [RFC2817].
The tricky part, in this method, is that the “STARTTLS” request is sent in the clear, thus is vulnerable to modifications. A typical attack is to modify the messages in a way that the client is fooled and thinks that the server does not have the “STARTTLS” capability. See a typical conversation of a hypothetical protocol:
(client connects to the server)
CLIENT: HELLO I’M MR. XXX
SERVER: NICE TO MEET YOU XXX
CLIENT: PLEASE START TLS
SERVER: OK
*** TLS STARTS
CLIENT: HERE ARE SOME CONFIDENTIAL DATA
And see an example of a conversation where someone is acting in between:
(client connects to the server)
CLIENT: HELLO I’M MR. XXX
SERVER: NICE TO MEET YOU XXX
CLIENT: PLEASE START TLS
(here someone inserts this message)
SERVER: SORRY I DON’T HAVE THIS CAPABILITY
CLIENT: HERE ARE SOME CONFIDENTIAL DATA
As you can see above the client was fooled, and was dummy enough to send the confidential data in the clear.
How to avoid the above attack? As you may have already noticed this one is easy to avoid. The client has to ask the user before it connects whether the user requests TLS or not. If the user answered that he certainly wants the secure layer the last conversation should be:
(client connects to the server)
CLIENT: HELLO I’M MR. XXX
SERVER: NICE TO MEET YOU XXX
CLIENT: PLEASE START TLS
(here someone inserts this message)
SERVER: SORRY I DON’T HAVE THIS CAPABILITY
CLIENT: BYE
(the client notifies the user that the secure connection was not possible)
This method, if implemented properly, is far better than the traditional method, and the security properties remain the same, since only denial of service is possible. The benefit is that the server may request additional data before the TLS Handshake protocol starts, in order to send the correct certificate, use the correct password file, or anything else!
Previous: How to use TLS in application protocols, Up: Introduction to TLS [Contents][Index]
One of the initial decisions in the GnuTLS development was to implement the known security protocols for the transport layer. Initially TLS 1.0 was implemented since it was the latest at that time, and was considered to be the most advanced in security properties. Later the SSL 3.0 protocol was implemented since it is still the only protocol supported by several servers and there are no serious security vulnerabilities known.
One question that may arise is why we didn’t implement SSL 2.0 in the library. There are several reasons, most important being that it has serious security flaws, unacceptable for a modern security library. Other than that, this protocol is barely used by anyone these days since it has been deprecated since 1996. The security problems in SSL 2.0 include:
Other protocols such as Microsoft’s PCT 1 and PCT 2 were not implemented because they were also abandoned and deprecated by SSL 3.0 and later TLS 1.0.
Next: Shared-key and anonymous authentication, Previous: Introduction to TLS, Up: Top [Contents][Index]
The most known authentication method of TLS are certificates. The PKIX [PKIX] public key infrastructure is daily used by anyone using a browser today. GnuTLS supports both X.509 certificates [PKIX] and OpenPGP certificates using a common API.
The key exchange algorithms supported by certificate authentication are shown in Table 4.1.
Key exchange | Description |
---|---|
RSA | The RSA algorithm is used to encrypt a key and send it to the peer. The certificate must allow the key to be used for encryption. |
RSA_EXPORT | The RSA algorithm is used to encrypt a key and send it to the peer. In the EXPORT algorithm, the server signs temporary RSA parameters of 512 bits — which are considered weak — and sends them to the client. |
DHE_RSA | The RSA algorithm is used to sign ephemeral Diffie-Hellman parameters which are sent to the peer. The key in the certificate must allow the key to be used for signing. Note that key exchange algorithms which use ephemeral Diffie-Hellman parameters, offer perfect forward secrecy. That means that even if the private key used for signing is compromised, it cannot be used to reveal past session data. |
ECDHE_RSA | The RSA algorithm is used to sign ephemeral elliptic curve Diffie-Hellman parameters which are sent to the peer. The key in the certificate must allow the key to be used for signing. It also offers perfect forward secrecy. That means that even if the private key used for signing is compromised, it cannot be used to reveal past session data. |
DHE_DSS | The DSA algorithm is used to sign ephemeral Diffie-Hellman parameters which are sent to the peer. The certificate must contain DSA parameters to use this key exchange algorithm. DSA is the algorithm of the Digital Signature Standard (DSS). |
ECDHE_ECDSA | The Elliptic curve DSA algorithm is used to sign ephemeral elliptic curve Diffie-Hellman parameters which are sent to the peer. The certificate must contain ECDSA parameters to use this key exchange algorithm. |
Table 4.1: Supported key exchange algorithms.
• X.509 certificates: | ||
• OpenPGP certificates: | ||
• Digital signatures: |
Next: OpenPGP certificates, Up: Certificate authentication [Contents][Index]
The X.509 protocols rely on a hierarchical trust model. In this trust model Certification Authorities (CAs) are used to certify entities. Usually more than one certification authorities exist, and certification authorities may certify other authorities to issue certificates as well, following a hierarchical model.
One needs to trust one or more CAs for his secure communications. In that case only the certificates issued by the trusted authorities are acceptable. The framework is illustrated on Figure 4.1.
Next: Importing an X.509 certificate, Up: X.509 certificates [Contents][Index]
An X.509 certificate usually contains information about the certificate holder, the signer, a unique serial number, expiration dates and some other fields [PKIX] as shown in Table 4.2.
Field | Description |
---|---|
version | The field that indicates the version of the certificate. |
serialNumber | This field holds a unique serial number per certificate. |
signature | The issuing authority’s signature. |
issuer | Holds the issuer’s distinguished name. |
validity | The activation and expiration dates. |
subject | The subject’s distinguished name of the certificate. |
extensions | The extensions are fields only present in version 3 certificates. |
Table 4.2: X.509 certificate fields.
The certificate’s subject or issuer name is not just a single string. It is a Distinguished name and in the ASN.1 notation is a sequence of several object identifiers with their corresponding values. Some of available OIDs to be used in an X.509 distinguished name are defined in gnutls/x509.h.
The Version field in a certificate has values either 1 or 3 for version 3 certificates. Version 1 certificates do not support the extensions field so it is not possible to distinguish a CA from a person, thus their usage should be avoided.
The validity dates are there to indicate the date that the specific certificate was activated and the date the certificate’s key would be considered invalid.
Certificate extensions are there to include information about the certificate’s subject that did not fit in the typical certificate fields. Those may be e-mail addresses, flags that indicate whether the belongs to a CA etc. All the supported X.509 version 3 extensions are shown in Table 4.3.
Extension | OID | Description |
---|---|---|
Subject key id | 2.5.29.14 | An identifier of the key of the subject. |
Authority key id | 2.5.29.35 | An identifier of the authority’s key used to sign the certificate. |
Subject alternative name | 2.5.29.17 | Alternative names to subject’s distinguished name. |
Key usage | 2.5.29.15 | Constraints the key’s usage of the certificate. |
Extended key usage | 2.5.29.37 | Constraints the purpose of the certificate. |
Basic constraints | 2.5.29.19 | Indicates whether this is a CA certificate or not, and specify the maximum path lengths of certificate chains. |
CRL distribution points | 2.5.29.31 | This extension is set by the CA, in order to inform about the issued CRLs. |
Proxy Certification Information | 1.3.6.1.5.5.7.1.14 | Proxy Certificates includes this extension that contains the OID of the proxy policy language used, and can specify limits on the maximum lengths of proxy chains. Proxy Certificates are specified in [RFC3820]. |
Table 4.3: X.509 certificate extensions.
In GnuTLS the X.509 certificate structures are
handled using the gnutls_x509_crt_t
type and the corresponding
private keys with the gnutls_x509_privkey_t
type. All the
available functions for X.509 certificate handling have
their prototypes in gnutls/x509.h. An example program to
demonstrate the X.509 parsing capabilities can be found at
ex:x509-info.
Next: X.509 distinguished names, Previous: X.509 certificate structure, Up: X.509 certificates [Contents][Index]
The certificate structure should be initialized using gnutls_x509_crt_init, and a certificate structure can be imported using gnutls_x509_crt_import.
int gnutls_x509_crt_init (gnutls_x509_crt_t * cert)
int gnutls_x509_crt_import (gnutls_x509_crt_t cert, const gnutls_datum_t * data, gnutls_x509_crt_fmt_t format)
void gnutls_x509_crt_deinit (gnutls_x509_crt_t cert)
In several functions an array of certificates is required. To assist in initialization and import the following two functions are provided.
int gnutls_x509_crt_list_import (gnutls_x509_crt_t * certs, unsigned int * cert_max, const gnutls_datum_t * data, gnutls_x509_crt_fmt_t format, unsigned int flags)
int gnutls_x509_crt_list_import2 (gnutls_x509_crt_t ** certs, unsigned int * size, const gnutls_datum_t * data, gnutls_x509_crt_fmt_t format, unsigned int flags)
In all cases after use a certificate must be deinitialized using gnutls_x509_crt_deinit.
Note that although the functions above apply to gnutls_x509_crt_t
structure, similar functions
exist for the CRL structure gnutls_x509_crl_t
.
Next: Verifying X.509 certificate paths, Previous: Importing an X.509 certificate, Up: X.509 certificates [Contents][Index]
The “subject” of an X.509 certificate is not described by a single name, but rather with a distinguished name. This in X.509 terminology is a list of strings each associated an object identifier. To make things simple GnuTLS provides gnutls_x509_crt_get_dn which follows the rules in [RFC4514] and returns a single string. Access to each string by individual object identifiers can be accessed using gnutls_x509_crt_get_dn_by_oid.
cert: should contain a gnutls_x509_crt_t
structure
buf: a pointer to a structure to hold the name (may be null)
buf_size: initially holds the size of buf
This function will copy the name of the Certificate in the provided buffer. The name will be in the form "C=xxxx,O=yyyy,CN=zzzz" as described in RFC4514. The output string will be ASCII or UTF-8 encoded, depending on the certificate data.
If buf
is null then only the size will be filled.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is not
long enough, and in that case the buf_size
will be updated
with the required size. On success 0 is returned.
cert: should contain a gnutls_x509_crt_t
structure
oid: holds an Object Identified in null terminated string
indx: In case multiple same OIDs exist in the RDN, this specifies which to send. Use (0) to get the first one.
raw_flag: If non (0) returns the raw DER data of the DN part.
buf: a pointer where the DN part will be copied (may be null).
buf_size: initially holds the size of buf
This function will extract the part of the name of the Certificate subject specified by the given OID. The output, if the raw flag is not used, will be encoded as described in RFC4514. Thus a string that is ASCII or UTF-8 encoded, depending on the certificate data.
Some helper macros with popular OIDs can be found in gnutls/x509.h
If raw flag is (0), this function will only return known OIDs as
text. Other OIDs will be DER encoded, as described in RFC4514 –
in hex format with a ’#’ prefix. You can check about known OIDs
using gnutls_x509_dn_oid_known()
.
If buf
is null then only the size will be filled. If the raw_flag
is not specified the output is always null terminated, although the
buf_size
will not include the null character.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the *buf_size will be updated
with the required size. On success 0 is returned.
cert: should contain a gnutls_x509_crt_t
structure
indx: This specifies which OID to return. Use (0) to get the first one.
oid: a pointer to a buffer to hold the OID (may be null)
oid_size: initially holds the size of oid
This function will extract the OIDs of the name of the Certificate subject specified by the given index.
If oid
is null then only the size will be filled. The oid
returned will be null terminated, although oid_size
will not
account for the trailing null.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the oid_size
will be updated
with the required size. On success 0 is returned.
The more powerful gnutls_x509_crt_get_subject and gnutls_x509_dn_get_rdn_ava provide efficient access to the contents of the distinguished name structure.
cert: should contain a gnutls_x509_crt_t
structure
dn: output variable with pointer to uint8_t DN.
Return the Certificate’s Subject DN as an uint8_t data type. You
may use gnutls_x509_dn_get_rdn_ava()
to decode the DN.
Note that dn
should be treated as constant. Because points
into the cert
object, you may not deallocate cert
and continue to access dn
.
Returns: Returns 0 on success, or an error code.
dn: input variable with uint8_t DN pointer
irdn: index of RDN
iava: index of AVA.
ava: Pointer to structure which will hold output information.
Get pointers to data within the DN.
Note that ava
will contain pointers into the dn
structure, so you
should not modify any data or deallocate it. Note also that the DN
in turn points into the original certificate structure, and thus
you may not deallocate the certificate and continue to access dn
.
Returns: Returns 0 on success, or an error code.
Similar functions exist to access the distinguished name of the issuer of the certificate.
int gnutls_x509_crt_get_issuer_dn (gnutls_x509_crt_t cert, char * buf, size_t * buf_size)
int gnutls_x509_crt_get_issuer_dn_by_oid (gnutls_x509_crt_t cert, const char * oid, int indx, unsigned int raw_flag, void * buf, size_t * buf_size)
int gnutls_x509_crt_get_issuer_dn_oid (gnutls_x509_crt_t cert, int indx, void * oid, size_t * oid_size)
int gnutls_x509_crt_get_issuer (gnutls_x509_crt_t cert, gnutls_x509_dn_t * dn)
Next: Verifying a certificate in the context of TLS session, Previous: X.509 distinguished names, Up: X.509 certificates [Contents][Index]
Verifying certificate paths is important in X.509 authentication. For this purpose the following functions are provided.
list: The structure of the list
clist: A list of CAs
clist_size: The length of the CA list
flags: should be 0.
This function will add the given certificate authorities to the trusted list. The list of CAs must not be deinitialized during this structure’s lifetime.
Returns: The number of added elements is returned.
Since: 3.0
list: The structure of the list
cert: A certificate
name: An identifier for the certificate
name_size: The size of the identifier
flags: should be 0.
This function will add the given certificate to the trusted
list and associate it with a name. The certificate will not be
be used for verification with gnutls_x509_trust_list_verify_crt()
but only with gnutls_x509_trust_list_verify_named_crt()
.
In principle this function can be used to set individual "server" certificates that are trusted by the user for that specific server but for no other purposes.
The certificate must not be deinitialized during the lifetime of the trusted list.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
list: The structure of the list
crl_list: A list of CRLs
crl_size: The length of the CRL list
flags: if GNUTLS_TL_VERIFY_CRL is given the CRLs will be verified before being added.
verification_flags: gnutls_certificate_verify_flags if flags specifies GNUTLS_TL_VERIFY_CRL
This function will add the given certificate revocation lists to the trusted list. The list of CRLs must not be deinitialized during this structure’s lifetime.
This function must be called after gnutls_x509_trust_list_add_cas()
to allow verifying the CRLs for validity.
Returns: The number of added elements is returned.
Since: 3.0
list: The structure of the list
cert_list: is the certificate list to be verified
cert_list_size: is the certificate list size
flags: Flags that may be used to change the verification algorithm. Use OR of the gnutls_certificate_verify_flags enumerations.
verify: will hold the certificate verification output.
func: If non-null will be called on each chain element verification with the output.
This function will try to verify the given certificate and return its status.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
list: The structure of the list
cert: is the certificate to be verified
name: is the certificate’s name
name_size: is the certificate’s name size
flags: Flags that may be used to change the verification algorithm. Use OR of the gnutls_certificate_verify_flags enumerations.
verify: will hold the certificate verification output.
func: If non-null will be called on each chain element verification with the output.
This function will try to find a matching named certificate. If a match is found the certificate is considered valid. In addition to that this function will also check CRLs.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
The verification function will verify a given certificate chain against a list of certificate
authorities and certificate revocation lists, and output
a bit-wise OR of elements of the gnutls_certificate_status_t
enumeration shown in Figure 4.2. The GNUTLS_CERT_INVALID
flag
is always set on a verification error and more detailed flags will also be set when appropriate.
GNUTLS_CERT_INVALID
The certificate is not signed by one of the known authorities or the signature is invalid.
GNUTLS_CERT_REVOKED
Certificate is revoked by its authority. In X.509 this will be set only if CRLs are checked.
GNUTLS_CERT_SIGNER_NOT_FOUND
The certificate’s issuer is not known. This is the case if the issuer is not included in the trusted certificate list.
GNUTLS_CERT_SIGNER_NOT_CA
The certificate’s signer was not a CA. This may happen if this was a version 1 certificate, which is common with some CAs, or a version 3 certificate without the basic constrains extension.
GNUTLS_CERT_INSECURE_ALGORITHM
The certificate was signed using an insecure algorithm such as MD2 or MD5. These algorithms have been broken and should not be trusted.
GNUTLS_CERT_NOT_ACTIVATED
The certificate is not yet activated.
GNUTLS_CERT_EXPIRED
The certificate has expired.
GNUTLS_CERT_SIGNATURE_FAILURE
– undescribed –
GNUTLS_CERT_REVOCATION_DATA_SUPERSEDED
The revocation data are old and have been superseded.
GNUTLS_CERT_REVOCATION_DATA_ISSUED_IN_FUTURE
The revocation data have a future issue date.
Figure 4.2: The gnutls_certificate_status_t
enumeration.
An example of certificate verification is shown in ex:verify2. It is also possible to have a set of certificates that are trusted for a particular server but not to authorize other certificates. This purpose is served by the functions gnutls_x509_trust_list_add_named_crt and gnutls_x509_trust_list_verify_named_crt.
Next: Verifying a certificate using trust on first use authentication, Previous: Verifying X.509 certificate paths, Up: X.509 certificates [Contents][Index]
When operating in the context of a TLS session, the trusted certificate authority list may also be set using:
int gnutls_certificate_set_x509_trust_file (gnutls_certificate_credentials_t cred, const char * cafile, gnutls_x509_crt_fmt_t type)
int gnutls_certificate_set_x509_crl_file (gnutls_certificate_credentials_t res, const char * crlfile, gnutls_x509_crt_fmt_t type)
int gnutls_certificate_set_x509_system_trust (gnutls_certificate_credentials_t cred)
Then it is not required to setup a trusted list as above. The function gnutls_certificate_verify_peers2 may then be used to verify the peer’s certificate chain. The flags are set similarly to the verification functions in the previous section.
There is also the possibility to pass some input to the verification
functions in the form of flags. For gnutls_x509_trust_list_verify_crt the
flags are passed straightforward, but
gnutls_certificate_verify_peers2 depends on the flags set by
calling gnutls_certificate_set_verify_flags. All the available
flags are part of the enumeration
gnutls_certificate_verify_flags
shown in Figure 4.3.
GNUTLS_VERIFY_DISABLE_CA_SIGN
If set a signer does not have to be a certificate authority. This flag should normaly be disabled, unless you know what this means.
GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT
Allow trusted CA certiï¬cates
with version 1. This is safer than GNUTLS_VERIFY_ALLOW_ANY_X509_V1_CA_CRT
,
and should be used instead. That way only signers in your trusted list
will be allowed to have certiï¬cates of version 1. This is the default.
GNUTLS_VERIFY_DO_NOT_ALLOW_SAME
If a certificate is not signed by anyone trusted but exists in the trusted CA list do not treat it as trusted.
GNUTLS_VERIFY_ALLOW_ANY_X509_V1_CA_CRT
Allow CA certificates that
have version 1 (both root and intermediate). This might be
dangerous since those haven’t the basicConstraints
extension. Must be used in combination with
GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT
.
GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD2
Allow certificates to be signed using the broken MD2 algorithm.
GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5
Allow certificates to be signed using the broken MD5 algorithm.
GNUTLS_VERIFY_DISABLE_TIME_CHECKS
Disable checking of activation and expiration validity periods of certificate chains. Don’t set this unless you understand the security implications.
GNUTLS_VERIFY_DISABLE_TRUSTED_TIME_CHECKS
If set a signer in the trusted list is never checked for expiration or activation.
GNUTLS_VERIFY_DO_NOT_ALLOW_X509_V1_CA_CRT
Do not allow trusted CA certificates that have version 1. This option is to be used to deprecate all certificates of version 1.
GNUTLS_VERIFY_DISABLE_CRL_CHECKS
Disable checking for validity using certificate revocation lists.
GNUTLS_VERIFY_ALLOW_UNSORTED_CHAIN
A certificate chain is tolerated if unsorted (the case with many TLS servers out there).
Figure 4.3: The gnutls_certificate_verify_flags
enumeration.
Although the verification of a certificate path indicates that the certificate is signed by trusted authority, does not reveal anything about the peer’s identity. It is required to verify if the certificate’s owner is the one you expect. For more information consult [RFC2818] and section ex:verify for an example.
Previous: Verifying a certificate in the context of TLS session, Up: X.509 certificates [Contents][Index]
It is possible to use a trust on first use (similar to SSH) authentication method in GnuTLS. That is the concept used by the SSH programs, where the public key of the peer is not verified, or verified in an out-of-bound way, but subsequent connections to the same peer require the public key to remain the same. Such a system in combination with the typical CA verification of a certificate, and OCSP revocation checks, can help to provide multiple factor verification, where a single point of failure is not enough to compromise the system. For example a server compromise may be detected using OCSP, and a CA compromise can be detected using the trust on first use method. Such a hybrid system with X.509 and trust on first use authentication is shown in Simple client example with SSH-style certificate verification.
db_name: A file specifying the stored keys (use NULL for the default)
tdb: A storage structure or NULL to use the default
host: The peer’s name
service: non-NULL if this key is specific to a service (e.g. http)
cert_type: The type of the certificate
cert: The raw (der) data of the certificate
flags: should be 0.
This function will try to verify the provided certificate using
a list of stored public keys. The service
field if non-NULL should
be a port number.
The retrieve
variable if non-null specifies a custom backend for
the retrieval of entries. If it is NULL then the
default file backend will be used. In POSIX-like systems the
file backend uses the $HOME/.gnutls/known_hosts file.
Note that if the custom storage backend is provided the
retrieval function should return GNUTLS_E_CERTIFICATE_KEY_MISMATCH
if the host/service pair is found but key doesn’t match,
GNUTLS_E_NO_CERTIFICATE_FOUND
if no such host/service with
the given key is found, and 0 if it was found. The storage
function should return 0 on success.
Returns: If no associated public key is found
then GNUTLS_E_NO_CERTIFICATE_FOUND
will be returned. If a key
is found but does not match GNUTLS_E_CERTIFICATE_KEY_MISMATCH
is returned. On success, GNUTLS_E_SUCCESS
(0) is returned,
or a negative error value on other errors.
Since: 3.0
db_name: A file specifying the stored keys (use NULL for the default)
tdb: A storage structure or NULL to use the default
host: The peer’s name
service: non-NULL if this key is specific to a service (e.g. http)
cert_type: The type of the certificate
cert: The data of the certificate
expiration: The expiration time (use 0 to disable expiration)
flags: should be 0.
This function will store the provided certificate to the list of stored public keys. The key will be considered valid until the provided expiration time.
The store
variable if non-null specifies a custom backend for
the storage of entries. If it is NULL then the
default file backend will be used.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
In addition to the above the gnutls_store_commitment can be used to implement a key-pinning architecture as in [KEYPIN]. This provides a way for web server to commit on a public key that is not yet active.
db_name: A file specifying the stored keys (use NULL for the default)
tdb: A storage structure or NULL to use the default
host: The peer’s name
service: non-NULL if this key is specific to a service (e.g. http)
hash_algo: The hash algorithm type
hash: The raw hash
expiration: The expiration time (use 0 to disable expiration)
flags: should be 0.
This function will store the provided hash commitment to the list of stored public keys. The key with the given hash will be considered valid until the provided expiration time.
The store
variable if non-null specifies a custom backend for
the storage of entries. If it is NULL then the
default file backend will be used.
Note that this function is not thread safe with the default backend.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
The storage and verification functions may be used with the default text file based back-end, or another back-end may be specified. That should contain storage and retrieval functions and specified as below.
int gnutls_tdb_init (gnutls_tdb_t* tdb)
void gnutls_tdb_deinit (gnutls_tdb_t tdb)
void gnutls_tdb_set_verify_func (gnutls_tdb_t tdb, gnutls_tdb_verify_func verify)
void gnutls_tdb_set_store_func (gnutls_tdb_t tdb, gnutls_tdb_store_func store)
void gnutls_tdb_set_store_commitment_func (gnutls_tdb_t tdb, gnutls_tdb_store_commitment_func cstore)
Next: Digital signatures, Previous: X.509 certificates, Up: Certificate authentication [Contents][Index]
The OpenPGP key authentication relies on a distributed trust model, called the “web of trust”. The “web of trust” uses a decentralized system of trusted introducers, which are the same as a CA. OpenPGP allows anyone to sign anyone else’s public key. When Alice signs Bob’s key, she is introducing Bob’s key to anyone who trusts Alice. If someone trusts Alice to introduce keys, then Alice is a trusted introducer in the mind of that observer. For example in Figure 4.4, David trusts Alice to be an introducer and Alice signed Bob’s key thus Dave trusts Bob’s key to be the real one.
There are some key points that are important in that model. In the example Alice has to sign Bob’s key, only if she is sure that the key belongs to Bob. Otherwise she may also make Dave falsely believe that this is Bob’s key. Dave has also the responsibility to know who to trust. This model is similar to real life relations.
Just see how Charlie behaves in the previous example. Although he has signed Bob’s key - because he knows, somehow, that it belongs to Bob - he does not trust Bob to be an introducer. Charlie decided to trust only Kevin, for some reason. A reason could be that Bob is lazy enough, and signs other people’s keys without being sure that they belong to the actual owner.
In GnuTLS the OpenPGP key structures
[RFC2440] are handled using the gnutls_openpgp_crt_t
type
and the corresponding private keys with the
gnutls_openpgp_privkey_t
type. All the prototypes for the key
handling functions can be found at gnutls/openpgp.h.
The verification functions of OpenPGP keys, included in GnuTLS, are simple ones, and do not use the features of the “web of trust”. For that reason, if the verification needs are complex, the assistance of external tools like GnuPG and GPGME8 is recommended.
In GnuTLS there is a verification function for OpenPGP certificates, the gnutls_openpgp_crt_verify_ring. This checks an OpenPGP key against a given set of public keys (keyring) and returns the key status. The key verification status is the same as in X.509 certificates, although the meaning and interpretation are different. For example an OpenPGP key may be valid, if the self signature is ok, even if no signers were found. The meaning of verification status flags is the same as in the X.509 certificates (see Figure 4.3).
key: the structure that holds the key.
keyring: holds the keyring to check against
flags: unused (should be 0)
verify: will hold the certificate verification output.
Verify all signatures in the key, using the given set of keys (keyring).
The key verification output will be put in verify
and will be one
or more of the gnutls_certificate_status_t
enumerated elements
bitwise or’d.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: the structure that holds the key.
flags: unused (should be 0)
verify: will hold the key verification output.
Verifies the self signature in the key. The key verification
output will be put in verify
and will be one or more of the
gnutls_certificate_status_t enumerated elements bitwise or’d.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
Similarly with X.509 certificates, one needs to specify the OpenPGP keyring file in the credentials structure. The certificates in this file will be used by gnutls_certificate_verify_peers2 to verify the signatures in the certificate sent by the peer.
c: A certificate credentials structure
file: filename of the keyring.
format: format of keyring.
The function is used to set keyrings that will be used internally by various OpenPGP functions. For example to find a key when it is needed for an operations. The keyring will also be used at the verification functions.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Previous: OpenPGP certificates, Up: Certificate authentication [Contents][Index]
In this section we will provide some information about digital signatures, how they work, and give the rationale for disabling some of the algorithms used.
Digital signatures work by using somebody’s secret key to sign some arbitrary data. Then anybody else could use the public key of that person to verify the signature. Since the data may be arbitrary it is not suitable input to a cryptographic digital signature algorithm. For this reason and also for performance cryptographic hash algorithms are used to preprocess the input to the signature algorithm. This works as long as it is difficult enough to generate two different messages with the same hash algorithm output. In that case the same signature could be used as a proof for both messages. Nobody wants to sign an innocent message of donating 1 euro to Greenpeace and find out that he donated 1.000.000 euros to Bad Inc.
For a hash algorithm to be called cryptographic the following three requirements must hold:
The last two requirements in the list are the most important in digital signatures. These protect against somebody who would like to generate two messages with the same hash output. When an algorithm is considered broken usually it means that the Collision resistance of the algorithm is less than brute force. Using the birthday paradox the brute force attack takes 2^{((hash size) / 2)} operations. Today colliding certificates using the MD5 hash algorithm have been generated as shown in [WEGER].
There has been cryptographic results for the SHA-1 hash algorithms as well, although they are not yet critical. Before 2004, MD5 had a presumed collision strength of 2^{64}, but it has been showed to have a collision strength well under 2^{50}. As of November 2005, it is believed that SHA-1’s collision strength is around 2^{63}. We consider this sufficiently hard so that we still support SHA-1. We anticipate that SHA-256/386/512 will be used in publicly-distributed certificates in the future. When 2^{63} can be considered too weak compared to the computer power available sometime in the future, SHA-1 will be disabled as well. The collision attacks on SHA-1 may also get better, given the new interest in tools for creating them.
If you connect to a server and use GnuTLS’ functions to verify the
certificate chain, and get a GNUTLS_CERT_INSECURE_ALGORITHM
validation error (see Verifying X.509 certificate paths), it means
that somewhere in the certificate chain there is a certificate signed
using RSA-MD2
or RSA-MD5
. These two digital signature
algorithms are considered broken, so GnuTLS fails verifying
the certificate. In some situations, it may be useful to be
able to verify the certificate chain anyway, assuming an attacker did
not utilize the fact that these signatures algorithms are broken.
This section will give help on how to achieve that.
It is important to know that you do not have to enable any of
the flags discussed here to be able to use trusted root CA
certificates self-signed using RSA-MD2
or RSA-MD5
. The
certificates in the trusted list are considered trusted irrespective
of the signature.
If you are using gnutls_certificate_verify_peers2 to verify the certificate chain, you can call gnutls_certificate_set_verify_flags with the flags:
GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD2
GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5
as in the following example:
gnutls_certificate_set_verify_flags (x509cred, GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5);
This will tell the verifier algorithm to enable RSA-MD5
when
verifying the certificates.
If you are using gnutls_x509_crt_verify or
gnutls_x509_crt_list_verify, you can pass the
GNUTLS_VERIFY_ALLOW_SIGN_RSA_MD5
parameter directly in the
flags
parameter.
If you are using these flags, it may also be a good idea to warn the
user when verification failure occur for this reason. The simplest is
to not use the flags by default, and only fall back to using them
after warning the user. If you wish to inspect the certificate chain
yourself, you can use gnutls_certificate_get_peers to extract
the raw server’s certificate chain, gnutls_x509_crt_list_import to parse each of the certificates, and
then gnutls_x509_crt_get_signature_algorithm to find out the
signing algorithm used for each certificate. If any of the
intermediary certificates are using GNUTLS_SIGN_RSA_MD2
or
GNUTLS_SIGN_RSA_MD5
, you could present a warning.
Next: More on certificate authentication, Previous: Certificate authentication, Up: Top [Contents][Index]
In addition to certificate authentication, the TLS protocol may be used with password, shared-key and anonymous authentication methods. The rest of this chapter discusses details of these methods.
• SRP authentication: | ||
• PSK authentication: | ||
• Anonymous authentication: |
• Authentication using SRP: | ||
• srptool Invocation: | Invoking srptool |
Next: srptool Invocation, Up: SRP authentication [Contents][Index]
GnuTLS supports authentication via the Secure Remote Password or SRP protocol (see [RFC2945,TOMSRP] for a description). The SRP key exchange is an extension to the TLS protocol, and it provides an authenticated with a password key exchange. The peers can be identified using a single password, or there can be combinations where the client is authenticated using SRP and the server using a certificate.
The advantage of SRP authentication, over other proposed secure password authentication schemes, is that SRP is not susceptible to off-line dictionary attacks. Moreover, SRP does not require the server to hold the user’s password. This kind of protection is similar to the one used traditionally in the UNIX /etc/passwd file, where the contents of this file did not cause harm to the system security if they were revealed. The SRP needs instead of the plain password something called a verifier, which is calculated using the user’s password, and if stolen cannot be used to impersonate the user.
Typical conventions in SRP are a password file, called tpasswd that holds the SRP verifiers (encoded passwords) and another file, tpasswd.conf, which holds the allowed SRP parameters. The included in GnuTLS helper follow those conventions. The srptool program, discussed in the next section is a tool to manipulate the SRP parameters.
The implementation in GnuTLS is based on [TLSSRP]. The supported key exchange methods are shown below.
SRP:
Authentication using the SRP protocol.
SRP_DSS:
Client authentication using the SRP protocol. Server is authenticated using a certificate with DSA parameters.
SRP_RSA:
Client authentication using the SRP protocol. Server is authenticated using a certificate with RSA parameters.
username: is the user’s name
password: is the user’s password
salt: should be some randomly generated bytes
generator: is the generator of the group
prime: is the group’s prime
res: where the verifier will be stored.
This function will create an SRP verifier, as specified in
RFC2945. The prime
and generator
should be one of the static
parameters defined in gnutls/gnutls.h or may be generated.
The verifier will be allocated with gnutls_malloc
() and will be stored in
res
using binary format.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
int gnutls_srp_base64_encode (const gnutls_datum_t * data, char * result, size_t * result_size)
int gnutls_srp_base64_decode (const gnutls_datum_t * b64_data, char * result, size_t * result_size)
Previous: Authentication using SRP, Up: SRP authentication [Contents][Index]
Simple program that emulates the programs in the Stanford SRP (Secure Remote Password) libraries using GnuTLS. It is intended for use in places where you don’t expect SRP authentication to be the used for system users.
In brief, to use SRP you need to create two files. These are the password file that holds the users and the verifiers associated with them and the configuration file to hold the group parameters (called tpasswd.conf).
This section was generated by AutoGen,
using the agtexi-cmd
template and the option descriptions for the srptool
program.
This software is released under the GNU General Public License, version 3 or later.
This is the automatically generated usage text for srptool.
The text printed is the same whether selected with the help
option
(--help) or the more-help
option (--more-help). more-help
will print
the usage text by passing it through a pager program.
more-help
is disabled on platforms without a working
fork(2)
function. The PAGER
environment variable is
used to select the program, defaulting to more. Both will exit
with a status code of 0.
srptool - GnuTLS SRP tool Usage: srptool [ -<flag> [<val>] | --<name>[{=| }<val>] ]... -d, --debug=num Enable debugging. - it must be in the range: 0 to 9999 -i, --index specify the index of the group parameters in tpasswd.conf to use. -u, --username=str specify a username -p, --passwd=str specify a password file. -s, --salt=num specify salt size. --verify just verify the password. -v, --passwd-conf=str specify a password conf file. --create-conf=str Generate a password configuration file. -v, --version[=arg] output version information and exit -h, --help display extended usage information and exit -!, --more-help extended usage information passed thru pager Options are specified by doubled hyphens and their name or by a single hyphen and the flag character. Simple program that emulates the programs in the Stanford SRP (Secure Remote Password) libraries using GnuTLS. It is intended for use in places where you don't expect SRP authentication to be the used for system users. In brief, to use SRP you need to create two files. These are the password file that holds the users and the verifiers associated with them and the configuration file to hold the group parameters (called tpasswd.conf). Please send bug reports to: <bug-gnutls@gnu.org>
This is the “enable debugging.” option. This option takes an argument number. Specifies the debug level.
This is the “just verify the password.” option. Verifies the password provided against the password file.
This is the “specify a password conf file.” option. This option takes an argument string. Specify a filename or a PKCS #11 URL to read the CAs from.
This is the “generate a password configuration file.” option. This option takes an argument string. This generates a password configuration file (tpasswd.conf) containing the required for TLS parameters.
One of the following exit values will be returned:
Successful program execution.
The operation failed or the command syntax was not valid.
gnutls-cli-debug (1), gnutls-serv (1), srptool (1), psktool (1), certtool (1)
To create tpasswd.conf which holds the g and n values for SRP protocol (generator and a large prime), run:
$ srptool --create-conf /etc/tpasswd.conf
This command will create /etc/tpasswd and will add user ’test’ (you will also be prompted for a password). Verifiers are stored by default in the way libsrp expects.
$ srptool --passwd /etc/tpasswd --passwd-conf /etc/tpasswd.conf -u test
This command will check against a password. If the password matches the one in /etc/tpasswd you will get an ok.
$ srptool --passwd /etc/tpasswd --passwd\-conf /etc/tpasswd.conf --verify -u test
Next: Anonymous authentication, Previous: SRP authentication, Up: Shared-key and anonymous authentication [Contents][Index]
• Authentication using PSK: | ||
• psktool Invocation: | Invoking psktool |
Next: psktool Invocation, Up: PSK authentication [Contents][Index]
Authentication using Pre-shared keys is a method to authenticate using usernames and binary keys. This protocol avoids making use of public key infrastructure and expensive calculations, thus it is suitable for constraint clients.
The implementation in GnuTLS is based on [TLSPSK]. The supported PSK key exchange methods are:
PSK:
Authentication using the PSK protocol.
DHE-PSK:
Authentication using the PSK protocol and Diffie-Hellman key exchange. This method offers perfect forward secrecy.
ECDHE-PSK:
Authentication using the PSK protocol and Elliptic curve Diffie-Hellman key exchange. This method offers perfect forward secrecy.
Helper functions to generate and maintain PSK keys are also included in GnuTLS.
int gnutls_key_generate (gnutls_datum_t * key, unsigned int key_size)
int gnutls_hex_encode (const gnutls_datum_t * data, char * result, size_t * result_size)
int gnutls_hex_decode (const gnutls_datum_t * hex_data, void * result, size_t * result_size)
Previous: Authentication using PSK, Up: PSK authentication [Contents][Index]
Program that generates random keys for use with TLS-PSK. The keys are stored in hexadecimal format in a key file.
This section was generated by AutoGen,
using the agtexi-cmd
template and the option descriptions for the psktool
program.
This software is released under the GNU General Public License, version 3 or later.
This is the automatically generated usage text for psktool.
The text printed is the same whether selected with the help
option
(--help) or the more-help
option (--more-help). more-help
will print
the usage text by passing it through a pager program.
more-help
is disabled on platforms without a working
fork(2)
function. The PAGER
environment variable is
used to select the program, defaulting to more. Both will exit
with a status code of 0.
psktool - GnuTLS PSK tool Usage: psktool [ -<flag> [<val>] | --<name>[{=| }<val>] ]... -d, --debug=num Enable debugging. - it must be in the range: 0 to 9999 -s, --keysize=num specify the key size in bytes - it must be in the range: 0 to 512 -u, --username=str specify a username -p, --passwd=str specify a password file. -v, --version[=arg] output version information and exit -h, --help display extended usage information and exit -!, --more-help extended usage information passed thru pager Options are specified by doubled hyphens and their name or by a single hyphen and the flag character. Program that generates random keys for use with TLS-PSK. The keys are stored in hexadecimal format in a key file. Please send bug reports to: <bug-gnutls@gnu.org>
This is the “enable debugging.” option. This option takes an argument number. Specifies the debug level.
One of the following exit values will be returned:
Successful program execution.
The operation failed or the command syntax was not valid.
gnutls-cli-debug (1), gnutls-serv (1), srptool (1), certtool (1)
To add a user ’psk_identity’ in passwd.psk for use with GnuTLS run:
$ ./psktool -u psk_identity -p passwd.psk Generating a random key for user 'psk_identity' Key stored to passwd.psk $ cat psks.txt psk_identity:88f3824b3e5659f52d00e959bacab954b6540344 $
This command will create passwd.psk if it does not exist and will add user ’psk_identity’ (you will also be prompted for a password).
Previous: PSK authentication, Up: Shared-key and anonymous authentication [Contents][Index]
The anonymous key exchange offers encryption without any indication of the peer’s identity. This kind of authentication is vulnerable to a man in the middle attack, but can be used even if there is no prior communication or shared trusted parties with the peer. Moreover it is useful when complete anonymity is required. Unless in one of the above cases, do not use anonymous authentication.
The available key exchange algorithms for anonymous authentication are shown below, but note that few public servers support them. They typically have to be explicitly enabled.
ANON_DH:
This algorithm exchanges Diffie-Hellman parameters.
ANON_ECDH:
This algorithm exchanges elliptic curve Diffie-Hellman parameters. It is more efficient than ANON_DH on equivalent security levels.
Next: How to use GnuTLS in applications, Previous: Shared-key and anonymous authentication, Up: Top [Contents][Index]
Certificates are not the only structures involved in a public key infrastructure. Several other structures that are used for certificate requests, encrypted private keys, revocation lists, GnuTLS abstract key structures, etc., are discussed in this chapter.
• PKCS 10 certificate requests: | ||
• PKIX certificate revocation lists: | ||
• OCSP certificate status checking: | ||
• Managing encrypted keys: | ||
• certtool Invocation: | Invoking certtool | |
• ocsptool Invocation: | Invoking ocsptool | |
• Smart cards and HSMs: | ||
• Abstract key types: |
A certificate request is a structure, which contain information about an applicant of a certificate service. It usually contains a private key, a distinguished name and secondary data such as a challenge password. GnuTLS supports the requests defined in PKCS #10 [RFC2986]. Other formats of certificate requests are not currently supported.
A certificate request can be generated by associating it with a private key, setting the subject’s information and finally self signing it. The last step ensures that the requester is in possession of the private key.
int gnutls_x509_crq_set_version (gnutls_x509_crq_t crq, unsigned int version)
int gnutls_x509_crq_set_dn_by_oid (gnutls_x509_crq_t crq, const char * oid, unsigned int raw_flag, const void * data, unsigned int sizeof_data)
int gnutls_x509_crq_set_key_usage (gnutls_x509_crq_t crq, unsigned int usage)
int gnutls_x509_crq_set_key_purpose_oid (gnutls_x509_crq_t crq, const void * oid, unsigned int critical)
int gnutls_x509_crq_set_basic_constraints (gnutls_x509_crq_t crq, unsigned int ca, int pathLenConstraint)
The gnutls_x509_crq_set_key and gnutls_x509_crq_sign2 functions associate the request with a private key and sign it. If a request is to be signed with a key residing in a PKCS #11 token it is recommended to use the signing functions shown in Abstract key types.
crq: should contain a gnutls_x509_crq_t
structure
key: holds a private key
This function will set the public parameters from the given private key to the request.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: should contain a gnutls_x509_crq_t
structure
key: holds a private key
dig: The message digest to use, i.e., GNUTLS_DIG_SHA1
flags: must be 0
This function will sign the certificate request with a private key.
This must be the same key as the one used in
gnutls_x509_crt_set_key()
since a certificate request is self
signed.
This must be the last step in a certificate request generation since all the previously set parameters are now signed.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
GNUTLS_E_ASN1_VALUE_NOT_FOUND
is returned if you didn’t set all
information in the certificate request (e.g., the version using
gnutls_x509_crq_set_version()
).
The following example is about generating a certificate request, and a private key. A certificate request can be later be processed by a CA which should return a signed certificate.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <gnutls/gnutls.h> #include <gnutls/x509.h> #include <gnutls/abstract.h> #include <time.h> /* This example will generate a private key and a certificate * request. */ int main (void) { gnutls_x509_crq_t crq; gnutls_x509_privkey_t key; unsigned char buffer[10 * 1024]; size_t buffer_size = sizeof (buffer); unsigned int bits; gnutls_global_init (); /* Initialize an empty certificate request, and * an empty private key. */ gnutls_x509_crq_init (&crq); gnutls_x509_privkey_init (&key); /* Generate an RSA key of moderate security. */ bits = gnutls_sec_param_to_pk_bits (GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_NORMAL); gnutls_x509_privkey_generate (key, GNUTLS_PK_RSA, bits, 0); /* Add stuff to the distinguished name */ gnutls_x509_crq_set_dn_by_oid (crq, GNUTLS_OID_X520_COUNTRY_NAME, 0, "GR", 2); gnutls_x509_crq_set_dn_by_oid (crq, GNUTLS_OID_X520_COMMON_NAME, 0, "Nikos", strlen ("Nikos")); /* Set the request version. */ gnutls_x509_crq_set_version (crq, 1); /* Set a challenge password. */ gnutls_x509_crq_set_challenge_password (crq, "something to remember here"); /* Associate the request with the private key */ gnutls_x509_crq_set_key (crq, key); /* Self sign the certificate request. */ gnutls_x509_crq_sign2 (crq, key, GNUTLS_DIG_SHA1, 0); /* Export the PEM encoded certificate request, and * display it. */ gnutls_x509_crq_export (crq, GNUTLS_X509_FMT_PEM, buffer, &buffer_size); printf ("Certificate Request: \n%s", buffer); /* Export the PEM encoded private key, and * display it. */ buffer_size = sizeof (buffer); gnutls_x509_privkey_export (key, GNUTLS_X509_FMT_PEM, buffer, &buffer_size); printf ("\n\nPrivate key: \n%s", buffer); gnutls_x509_crq_deinit (crq); gnutls_x509_privkey_deinit (key); return 0; }
Next: OCSP certificate status checking, Previous: PKCS 10 certificate requests, Up: More on certificate authentication [Contents][Index]
A certificate revocation list (CRL) is a structure issued by an authority periodically containing a list of revoked certificates serial numbers. The CRL structure is signed with the issuing authorities’ keys. A typical CRL contains the fields as shown in Table 6.1. Certificate revocation lists are used to complement the expiration date of a certificate, in order to account for other reasons of revocation, such as compromised keys, etc.
A certificate request can be generated by associating it with a private key, setting the subject’s information and finally self signing it. The last step ensures that the requester is in possession of the private key. Each CRL is valid for limited amount of time and is required to provide, except for the current issuing time, also the issuing time of the next update.
Field | Description |
---|---|
version | The field that indicates the version of the CRL structure. |
signature | A signature by the issuing authority. |
issuer | Holds the issuer’s distinguished name. |
thisUpdate | The issuing time of the revocation list. |
nextUpdate | The issuing time of the revocation list that will update that one. |
revokedCertificates | List of revoked certificates serial numbers. |
extensions | Optional CRL structure extensions. |
Table 6.1: Certificate revocation list fields.
int gnutls_x509_crl_set_version (gnutls_x509_crl_t crl, unsigned int version)
int gnutls_x509_crl_set_crt_serial (gnutls_x509_crl_t crl, const void * serial, size_t serial_size, time_t revocation_time)
int gnutls_x509_crl_set_crt (gnutls_x509_crl_t crl, gnutls_x509_crt_t crt, time_t revocation_time)
int gnutls_x509_crl_set_next_update (gnutls_x509_crl_t crl, time_t exp_time)
int gnutls_x509_crl_set_this_update (gnutls_x509_crl_t crl, time_t act_time)
The gnutls_x509_crl_sign2 and gnutls_x509_crl_privkey_sign functions sign the revocation list with a private key. The latter function can be used to sign with a key residing in a PKCS #11 token.
crl: should contain a gnutls_x509_crl_t structure
issuer: is the certificate of the certificate issuer
issuer_key: holds the issuer’s private key
dig: The message digest to use. GNUTLS_DIG_SHA1 is the safe choice unless you know what you’re doing.
flags: must be 0
This function will sign the CRL with the issuer’s private key, and will copy the issuer’s information into the CRL.
This must be the last step in a certificate CRL since all the previously set parameters are now signed.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: should contain a gnutls_x509_crl_t structure
issuer: is the certificate of the certificate issuer
issuer_key: holds the issuer’s private key
dig: The message digest to use. GNUTLS_DIG_SHA1 is the safe choice unless you know what you’re doing.
flags: must be 0
This function will sign the CRL with the issuer’s private key, and will copy the issuer’s information into the CRL.
This must be the last step in a certificate CRL since all the previously set parameters are now signed.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since 2.12.0
Few extensions on the CRL structure are supported, including the CRL number extension and the authority key identifier.
int gnutls_x509_crl_set_number (gnutls_x509_crl_t crl, const void * nr, size_t nr_size)
int gnutls_x509_crl_set_authority_key_id (gnutls_x509_crl_t crl, const void * id, size_t id_size)
Next: Managing encrypted keys, Previous: PKIX certificate revocation lists, Up: More on certificate authentication [Contents][Index]
Certificates may be revoked before their expiration time has been reached. There are several reasons for revoking certificates, but a typical situation is when the private key associated with a certificate has been compromised. Traditionally, Certificate Revocation Lists (CRLs) have been used by application to implement revocation checking, however, several problems with CRLs have been identified [RIVESTCRL].
The Online Certificate Status Protocol, or OCSP [RFC2560], is a widely implemented protocol to perform certificate revocation status checking. An application that wish to verify the identity of a peer will verify the certificate against a set of trusted certificates and then check whether the certificate is listed in a CRL and/or perform an OCSP check for the certificate.
Before performing the OCSP query, the application will need to figure
out the address of the OCSP server. The OCSP server address can be
provided by the local user in manual configuration or may be stored
in the certificate that is being checked. The latter is due to
an extension field called the Authority Information Access (AIA) which
may hold the location of the OCSP responder in
the access method called id-ad-ocsp
. The following function
extracts this information from a certificate.
int gnutls_x509_crt_get_authority_info_access (gnutls_x509_crt_t crt, unsigned int seq, int what, gnutls_datum_t * data, unsigned int * critical)
There are several functions in GnuTLS for creating and manipulating OCSP requests and responses. The general idea is that a client application create an OCSP request object, store some information about the certificate to check in the request, and then export the request in DER format. The request will then need to be sent to the OCSP responder, which needs to be done by the application (GnuTLS does not send and receive OCSP packets). Normally an OCSP response is received that the application will need to import into an OCSP response object. The digital signature in the OCSP response needs to be verified against a set of trust anchors before the information in the response can be trusted.
The ASN.1 structure of OCSP requests are briefly as follows. It is useful to review the structures to get an understanding of which fields are modified by GnuTLS functions.
OCSPRequest ::= SEQUENCE { tbsRequest TBSRequest, optionalSignature [0] EXPLICIT Signature OPTIONAL } TBSRequest ::= SEQUENCE { version [0] EXPLICIT Version DEFAULT v1, requestorName [1] EXPLICIT GeneralName OPTIONAL, requestList SEQUENCE OF Request, requestExtensions [2] EXPLICIT Extensions OPTIONAL } Request ::= SEQUENCE { reqCert CertID, singleRequestExtensions [0] EXPLICIT Extensions OPTIONAL } CertID ::= SEQUENCE { hashAlgorithm AlgorithmIdentifier, issuerNameHash OCTET STRING, -- Hash of Issuer's DN issuerKeyHash OCTET STRING, -- Hash of Issuers public key serialNumber CertificateSerialNumber }
The basic functions to initialize, import, export and deallocate OCSP requests are the following.
int gnutls_ocsp_req_init (gnutls_ocsp_req_t * req)
void gnutls_ocsp_req_deinit (gnutls_ocsp_req_t req)
int gnutls_ocsp_req_import (gnutls_ocsp_req_t req, const gnutls_datum_t * data)
int gnutls_ocsp_req_export (gnutls_ocsp_req_t req, gnutls_datum_t * data)
int gnutls_ocsp_req_print (gnutls_ocsp_req_t req, gnutls_ocsp_print_formats_t format, gnutls_datum_t * out)
There are two interfaces for setting the identity of a certificate in
a OCSP request, the first being a low-level function when you have the
issuer name hash, issuer key hash, and certificate serial number in
binary form. The second is usually more useful if you have the
certificate (and its issuer) in a gnutls_x509_crt_t
type.
There is also a function to extract this information from an OCSP
request.
int gnutls_ocsp_req_add_cert_id (gnutls_ocsp_req_t req, gnutls_digest_algorithm_t digest, const gnutls_datum_t * issuer_name_hash, const gnutls_datum_t * issuer_key_hash, const gnutls_datum_t * serial_number)
int gnutls_ocsp_req_add_cert (gnutls_ocsp_req_t req, gnutls_digest_algorithm_t digest, gnutls_x509_crt_t issuer, gnutls_x509_crt_t cert)
int gnutls_ocsp_req_get_cert_id (gnutls_ocsp_req_t req, unsigned indx, gnutls_digest_algorithm_t * digest, gnutls_datum_t * issuer_name_hash, gnutls_datum_t * issuer_key_hash, gnutls_datum_t * serial_number)
Each OCSP request may contain a number of extensions. Extensions are identified by an Object Identifier (OID) and an opaque data buffer whose syntax and semantics is implied by the OID.
int gnutls_ocsp_req_get_extension (gnutls_ocsp_req_t req, unsigned indx, gnutls_datum_t * oid, unsigned int * critical, gnutls_datum_t * data)
int gnutls_ocsp_req_set_extension (gnutls_ocsp_req_t req, const char * oid, unsigned int critical, const gnutls_datum_t * data)
A common OCSP Request extension is the nonce extension (OID 1.3.6.1.5.5.7.48.1.2), which is used to avoid replay attacks of earlier recorded OCSP responses. The nonce extension carries a value that is intended to be sufficiently random and unique so that an attacker will not be able to give a stale response for the same nonce.
int gnutls_ocsp_req_get_nonce (gnutls_ocsp_req_t req, unsigned int * critical, gnutls_datum_t * nonce)
int gnutls_ocsp_req_set_nonce (gnutls_ocsp_req_t req, unsigned int critical, const gnutls_datum_t * nonce)
int gnutls_ocsp_req_randomize_nonce (gnutls_ocsp_req_t req)
The OCSP response structures is a bit more complex than the request. The important ASN.1 structure is as follows. In practice, all OCSP responses contain a Basic OCSP response sub-structure.
OCSPResponse ::= SEQUENCE { responseStatus OCSPResponseStatus, responseBytes [0] EXPLICIT ResponseBytes OPTIONAL } OCSPResponseStatus ::= ENUMERATED { successful (0), --Response has valid confirmations malformedRequest (1), --Illegal confirmation request internalError (2), --Internal error in issuer tryLater (3), --Try again later --(4) is not used sigRequired (5), --Must sign the request unauthorized (6) --Request unauthorized } ResponseBytes ::= SEQUENCE { responseType OBJECT IDENTIFIER, response OCTET STRING } id-pkix-ocsp-basic OBJECT IDENTIFIER ::= { id-pkix-ocsp 1 } BasicOCSPResponse ::= SEQUENCE { tbsResponseData ResponseData, signatureAlgorithm AlgorithmIdentifier, signature BIT STRING, certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL } ResponseData ::= SEQUENCE { version [0] EXPLICIT Version DEFAULT v1, responderID ResponderID, producedAt GeneralizedTime, responses SEQUENCE OF SingleResponse, responseExtensions [1] EXPLICIT Extensions OPTIONAL } ResponderID ::= CHOICE { byName [1] Name, byKey [2] KeyHash } KeyHash ::= OCTET STRING -- SHA-1 hash of responder's public key (excluding the tag and length fields) SingleResponse ::= SEQUENCE { certID CertID, certStatus CertStatus, thisUpdate GeneralizedTime, nextUpdate [0] EXPLICIT GeneralizedTime OPTIONAL, singleExtensions [1] EXPLICIT Extensions OPTIONAL } CertStatus ::= CHOICE { good [0] IMPLICIT NULL, revoked [1] IMPLICIT RevokedInfo, unknown [2] IMPLICIT UnknownInfo } RevokedInfo ::= SEQUENCE { revocationTime GeneralizedTime, revocationReason [0] EXPLICIT CRLReason OPTIONAL }
We provide basic functions for initialization, importing, exporting and deallocating OCSP responses. The Basic OCSP Response structure is automatically parsed when an OCSP Response is imported.
int gnutls_ocsp_resp_init (gnutls_ocsp_resp_t * resp)
void gnutls_ocsp_resp_deinit (gnutls_ocsp_resp_t resp)
int gnutls_ocsp_resp_import (gnutls_ocsp_resp_t resp, const gnutls_datum_t * data)
int gnutls_ocsp_resp_export (gnutls_ocsp_resp_t resp, gnutls_datum_t * data)
int gnutls_ocsp_resp_print (gnutls_ocsp_resp_t resp, gnutls_ocsp_print_formats_t format, gnutls_datum_t * out)
The OCSP response needs to be verified against some set of trust anchors before it can be relied upon.
int gnutls_ocsp_resp_verify (gnutls_ocsp_resp_t resp, gnutls_x509_trust_list_t trustlist, unsigned int * verify, unsigned int flags)
int gnutls_ocsp_resp_verify_direct (gnutls_ocsp_resp_t resp, gnutls_x509_crt_t issuer, unsigned int * verify, unsigned int flags)
Next: certtool Invocation, Previous: OCSP certificate status checking, Up: More on certificate authentication [Contents][Index]
Transferring or storing private keys in plain might not be a good idea. Any access on the keys becomes a fatal compromise. Storing the keys in hardware security modules (see Smart cards and HSMs) could solve the storage problem but it is not always practical or efficient enough. This section describes alternative ways that involve encryption of the private keys to store and transfer.
There are two alternatives to use for key encryption, PKCS #8 and #12 methods of private key encryption. The PKCS #8 method only allows encryption of the private key, whilst the PKCS #12 method allows in addition the bundling of other data into the structure. That could be bundling together the certificate as well as the trusted CA certificate.
PKCS #8 keys can be imported and exported as normal private keys using
the functions below. An addition to the normal import functions, are
a password and a flags argument. The flags can be any element of the gnutls_pkcs_encrypt_flags_t
enumeration. Note however, that GnuTLS only supports the PKCS #5 PBES2
encryption scheme. Keys encrypted with the obsolete PBES1 scheme cannot
be decrypted.
int gnutls_x509_privkey_import_pkcs8 (gnutls_x509_privkey_t key, const gnutls_datum_t * data, gnutls_x509_crt_fmt_t format, const char * password, unsigned int flags)
int gnutls_x509_privkey_export_pkcs8 (gnutls_x509_privkey_t key, gnutls_x509_crt_fmt_t format, const char * password, unsigned int flags, void * output_data, size_t * output_data_size)
GNUTLS_PKCS_PLAIN
Unencrypted private key.
GNUTLS_PKCS8_PLAIN
Same as GNUTLS_PKCS_PLAIN
.
GNUTLS_PKCS_USE_PKCS12_3DES
PKCS-12 3DES.
GNUTLS_PKCS8_USE_PKCS12_3DES
Same as GNUTLS_PKCS_USE_PKCS12_3DES
.
GNUTLS_PKCS_USE_PKCS12_ARCFOUR
PKCS-12 ARCFOUR.
GNUTLS_PKCS8_USE_PKCS12_ARCFOUR
Same as GNUTLS_PKCS_USE_PKCS12_ARCFOUR
.
GNUTLS_PKCS_USE_PKCS12_RC2_40
PKCS-12 RC2-40.
GNUTLS_PKCS8_USE_PKCS12_RC2_40
Same as GNUTLS_PKCS_USE_PKCS12_RC2_40
.
GNUTLS_PKCS_USE_PBES2_3DES
PBES2 3DES.
GNUTLS_PKCS_USE_PBES2_AES_128
PBES2 AES-128.
GNUTLS_PKCS_USE_PBES2_AES_192
PBES2 AES-192.
GNUTLS_PKCS_USE_PBES2_AES_256
PBES2 AES-256.
Figure 6.1: Encryption flags
A PKCS #12 structure [PKCS12] usually contains a user’s private keys and certificates. It is commonly used in browsers to export and import the user’s identities.
In GnuTLS the PKCS #12 structures are handled
using the gnutls_pkcs12_t
type. This is an abstract type that
may hold several gnutls_pkcs12_bag_t
types. The bag types are
the holders of the actual data, which may be certificates, private
keys or encrypted data. A bag of type encrypted should be decrypted
in order for its data to be accessed.
int gnutls_pkcs12_get_bag (gnutls_pkcs12_t pkcs12, int indx, gnutls_pkcs12_bag_t bag)
int gnutls_pkcs12_verify_mac (gnutls_pkcs12_t pkcs12, const char * pass)
int gnutls_pkcs12_bag_decrypt (gnutls_pkcs12_bag_t bag, const char * pass)
int gnutls_pkcs12_bag_get_count (gnutls_pkcs12_bag_t bag)
int gnutls_pkcs12_bag_get_data (gnutls_pkcs12_bag_t bag, int indx, gnutls_datum_t * data)
int gnutls_pkcs12_bag_get_key_id (gnutls_pkcs12_bag_t bag, int indx, gnutls_datum_t * id)
int gnutls_pkcs12_bag_get_friendly_name (gnutls_pkcs12_bag_t bag, int indx, char ** name)
The functions below are used to generate a PKCS #12 structure. An example of their usage is also shown.
int gnutls_pkcs12_set_bag (gnutls_pkcs12_t pkcs12, gnutls_pkcs12_bag_t bag)
int gnutls_pkcs12_bag_encrypt (gnutls_pkcs12_bag_t bag, const char * pass, unsigned int flags)
int gnutls_pkcs12_generate_mac (gnutls_pkcs12_t pkcs12, const char * pass)
int gnutls_pkcs12_bag_set_data (gnutls_pkcs12_bag_t bag, gnutls_pkcs12_bag_type_t type, const gnutls_datum_t * data)
int gnutls_pkcs12_bag_set_crl (gnutls_pkcs12_bag_t bag, gnutls_x509_crl_t crl)
int gnutls_pkcs12_bag_set_crt (gnutls_pkcs12_bag_t bag, gnutls_x509_crt_t crt)
int gnutls_pkcs12_bag_set_key_id (gnutls_pkcs12_bag_t bag, int indx, const gnutls_datum_t * id)
int gnutls_pkcs12_bag_set_friendly_name (gnutls_pkcs12_bag_t bag, int indx, const char * name)
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <gnutls/gnutls.h> #include <gnutls/pkcs12.h> #include "examples.h" #define OUTFILE "out.p12" /* This function will write a pkcs12 structure into a file. * cert: is a DER encoded certificate * pkcs8_key: is a PKCS #8 encrypted key (note that this must be * encrypted using a PKCS #12 cipher, or some browsers will crash) * password: is the password used to encrypt the PKCS #12 packet. */ int write_pkcs12 (const gnutls_datum_t * cert, const gnutls_datum_t * pkcs8_key, const char *password) { gnutls_pkcs12_t pkcs12; int ret, bag_index; gnutls_pkcs12_bag_t bag, key_bag; char pkcs12_struct[10 * 1024]; size_t pkcs12_struct_size; FILE *fd; /* A good idea might be to use gnutls_x509_privkey_get_key_id() * to obtain a unique ID. */ gnutls_datum_t key_id = { (void *) "\x00\x00\x07", 3 }; gnutls_global_init (); /* Firstly we create two helper bags, which hold the certificate, * and the (encrypted) key. */ gnutls_pkcs12_bag_init (&bag); gnutls_pkcs12_bag_init (&key_bag); ret = gnutls_pkcs12_bag_set_data (bag, GNUTLS_BAG_CERTIFICATE, cert); if (ret < 0) { fprintf (stderr, "ret: %s\n", gnutls_strerror (ret)); return 1; } /* ret now holds the bag's index. */ bag_index = ret; /* Associate a friendly name with the given certificate. Used * by browsers. */ gnutls_pkcs12_bag_set_friendly_name (bag, bag_index, "My name"); /* Associate the certificate with the key using a unique key * ID. */ gnutls_pkcs12_bag_set_key_id (bag, bag_index, &key_id); /* use weak encryption for the certificate. */ gnutls_pkcs12_bag_encrypt (bag, password, GNUTLS_PKCS_USE_PKCS12_RC2_40); /* Now the key. */ ret = gnutls_pkcs12_bag_set_data (key_bag, GNUTLS_BAG_PKCS8_ENCRYPTED_KEY, pkcs8_key); if (ret < 0) { fprintf (stderr, "ret: %s\n", gnutls_strerror (ret)); return 1; } /* Note that since the PKCS #8 key is already encrypted we don't * bother encrypting that bag. */ bag_index = ret; gnutls_pkcs12_bag_set_friendly_name (key_bag, bag_index, "My name"); gnutls_pkcs12_bag_set_key_id (key_bag, bag_index, &key_id); /* The bags were filled. Now create the PKCS #12 structure. */ gnutls_pkcs12_init (&pkcs12); /* Insert the two bags in the PKCS #12 structure. */ gnutls_pkcs12_set_bag (pkcs12, bag); gnutls_pkcs12_set_bag (pkcs12, key_bag); /* Generate a message authentication code for the PKCS #12 * structure. */ gnutls_pkcs12_generate_mac (pkcs12, password); pkcs12_struct_size = sizeof (pkcs12_struct); ret = gnutls_pkcs12_export (pkcs12, GNUTLS_X509_FMT_DER, pkcs12_struct, &pkcs12_struct_size); if (ret < 0) { fprintf (stderr, "ret: %s\n", gnutls_strerror (ret)); return 1; } fd = fopen (OUTFILE, "w"); if (fd == NULL) { fprintf (stderr, "cannot open file\n"); return 1; } fwrite (pkcs12_struct, 1, pkcs12_struct_size, fd); fclose (fd); gnutls_pkcs12_bag_deinit (bag); gnutls_pkcs12_bag_deinit (key_bag); gnutls_pkcs12_deinit (pkcs12); return 0; }
Next: ocsptool Invocation, Previous: Managing encrypted keys, Up: More on certificate authentication [Contents][Index]
Tool to parse and generate X.509 certificates, requests and private keys. It can be used interactively or non interactively by specifying the template command line option.
This section was generated by AutoGen,
using the agtexi-cmd
template and the option descriptions for the certtool
program.
This software is released under the GNU General Public License, version 3 or later.
This is the automatically generated usage text for certtool.
The text printed is the same whether selected with the help
option
(--help) or the more-help
option (--more-help). more-help
will print
the usage text by passing it through a pager program.
more-help
is disabled on platforms without a working
fork(2)
function. The PAGER
environment variable is
used to select the program, defaulting to more. Both will exit
with a status code of 0.
certtool - GnuTLS certificate tool Usage: certtool [ -<flag> [<val>] | --<name>[{=| }<val>] ]... -d, --debug=num Enable debugging. - it must be in the range: 0 to 9999 -V, --verbose More verbose output - may appear multiple times --infile=file Input file - file must pre-exist --outfile=str Output file -s, --generate-self-signed Generate a self-signed certificate -c, --generate-certificate Generate a signed certificate --generate-proxy Generates a proxy certificate --generate-crl Generate a CRL -u, --update-certificate Update a signed certificate -p, --generate-privkey Generate a private key -q, --generate-request Generate a PKCS #10 certificate request - prohibits the option 'infile' -e, --verify-chain Verify a PEM encoded certificate chain. --verify Verify a PEM encoded certificate chain using a trusted list. - requires the option 'load-ca-certificate' --verify-crl Verify a CRL using a trusted list. - requires the option 'load-ca-certificate' --generate-dh-params Generate PKCS #3 encoded Diffie-Hellman parameters. --get-dh-params Get the included PKCS #3 encoded Diffie-Hellman parameters. --dh-info Print information PKCS #3 encoded Diffie-Hellman parameters --load-privkey=str Loads a private key file --load-pubkey=str Loads a public key file --load-request=file Loads a certificate request file - file must pre-exist --load-certificate=str Loads a certificate file --load-ca-privkey=str Loads the certificate authority's private key file --load-ca-certificate=str Loads the certificate authority's certificate file --password=str Password to use --hex-numbers Print big number in an easier format to parse --cprint In certain operations it prints the information is C-friendly format --null-password Enforce a NULL password -i, --certificate-info Print information on the given certificate --certificate-pubkey Print certificate's public key --pgp-certificate-info Print information on the given OpenPGP certificate --pgp-ring-info Print information on the given OpenPGP keyring structure -l, --crl-info Print information on the given CRL structure --crq-info Print information on the given certificate request --no-crq-extensions Do not use extensions in certificate requests --p12-info Print information on a PKCS #12 structure --p7-info Print information on a PKCS #7 structure --smime-to-p7 Convert S/MIME to PKCS #7 structure -k, --key-info Print information on a private key --pgp-key-info Print information on an OpenPGP private key --pubkey-info Print information on a public key --v1 Generate an X.509 version 1 certificate (with no extensions) --to-p12 Generate a PKCS #12 structure - requires the option 'load-certificate' --to-p8 Generate a PKCS #8 structure -8, --pkcs8 Use PKCS #8 format for private keys --rsa Generate RSA key --dsa Generate DSA key --ecc Generate ECC (ECDSA) key --ecdsa an alias for the 'ecc' option --hash=str Hash algorithm to use for signing. --inder Use DER format for input certificates and private keys. - disabled as '--no-inder' --inraw an alias for the 'inder' option --outder Use DER format for output certificates and private keys - disabled as '--no-outder' --outraw an alias for the 'outder' option --bits=num Specify the number of bits for key generate --sec-param=str Specify the security level [low, legacy, normal, high, ultra]. --disable-quick-random No effect --template=file Template file to use for non-interactive operation - file must pre-exist --pkcs-cipher=str Cipher to use for PKCS #8 and #12 operations -v, --version[=arg] output version information and exit -h, --help display extended usage information and exit -!, --more-help extended usage information passed thru pager Options are specified by doubled hyphens and their name or by a single hyphen and the flag character. Tool to parse and generate X.509 certificates, requests and private keys. It can be used interactively or non interactively by specifying the template command line option. Please send bug reports to: <bug-gnutls@gnu.org>
This is the “enable debugging.” option. This option takes an argument number. Specifies the debug level.
This is the “verify a pem encoded certificate chain.” option. The last certificate in the chain must be a self signed one.
This is the “verify a pem encoded certificate chain using a trusted list.” option.
This option has some usage constraints. It:
The trusted certificate list must be loaded with –load-ca-certificate.
This is the “verify a crl using a trusted list.” option.
This option has some usage constraints. It:
The trusted certificate list must be loaded with –load-ca-certificate.
This is the “get the included pkcs #3 encoded diffie-hellman parameters.” option. Returns stored DH parameters in GnuTLS. Those parameters are used in the SRP protocol. The parameters returned by fresh generation are more efficient since GnuTLS 3.0.9.
This is the “loads a private key file” option. This option takes an argument string. This can be either a file or a PKCS #11 URL
This is the “loads a public key file” option. This option takes an argument string. This can be either a file or a PKCS #11 URL
This is the “loads a certificate file” option. This option takes an argument string. This can be either a file or a PKCS #11 URL
This is the “loads the certificate authority’s private key file” option. This option takes an argument string. This can be either a file or a PKCS #11 URL
This is the “loads the certificate authority’s certificate file” option. This option takes an argument string. This can be either a file or a PKCS #11 URL
This is the “generate a pkcs #12 structure” option.
This option has some usage constraints. It:
It requires a certificate, a private key and possibly a CA certificate to be specified.
This is the “hash algorithm to use for signing.” option. This option takes an argument string. Available hash functions are SHA1, RMD160, SHA256, SHA384, SHA512.
This is the “use der format for input certificates and private keys.” option. The input files will be assumed to be in DER or RAW format. Unlike options that in PEM input would allow multiple input data (e.g. multiple certificates), when reading in DER format a single data structure is read.
This is an alias for the inder
option,
see the inder option documentation.
This is the “use der format for output certificates and private keys” option. The output will be in DER or RAW format.
This is an alias for the outder
option,
see the outder option documentation.
This is the “specify the security level [low, legacy, normal, high, ultra].” option. This option takes an argument string Security parameter. This is alternative to the bits option.
This is the “cipher to use for pkcs #8 and #12 operations” option. This option takes an argument string Cipher. Cipher may be one of 3des, 3des-pkcs12, aes-128, aes-192, aes-256, rc2-40, arcfour.
One of the following exit values will be returned:
Successful program execution.
The operation failed or the command syntax was not valid.
To create an RSA private key, run:
$ certtool --generate-privkey --outfile key.pem --rsa
To create a DSA or elliptic curves (ECDSA) private key use the above command combined with ’dsa’ or ’ecc’ options.
To create a certificate request (needed when the certificate is issued by another party), run:
certtool --generate-request --load-privkey key.pem \ --outfile request.pem
If the private key is stored in a smart card you can generate a request by specifying the private key object URL.
$ ./certtool --generate-request --load-privkey "pkcs11:..." \ --load-pubkey "pkcs11:..." --outfile request.pem
To create a self signed certificate, use the command:
$ certtool --generate-privkey --outfile ca-key.pem $ certtool --generate-self-signed --load-privkey ca-key.pem \ --outfile ca-cert.pem
Note that a self-signed certificate usually belongs to a certificate authority, that signs other certificates.
To generate a certificate using the previous request, use the command:
$ certtool --generate-certificate --load-request request.pem \ --outfile cert.pem --load-ca-certificate ca-cert.pem \ --load-ca-privkey ca-key.pem
To generate a certificate using the private key only, use the command:
$ certtool --generate-certificate --load-privkey key.pem \ --outfile cert.pem --load-ca-certificate ca-cert.pem \ --load-ca-privkey ca-key.pem
To view the certificate information, use:
$ certtool --certificate-info --infile cert.pem
To generate a PKCS #12 structure using the previous key and certificate, use the command:
$ certtool --load-certificate cert.pem --load-privkey key.pem \ --to-p12 --outder --outfile key.p12
Some tools (reportedly web browsers) have problems with that file because it does not contain the CA certificate for the certificate. To work around that problem in the tool, you can use the –load-ca-certificate parameter as follows:
$ certtool --load-ca-certificate ca.pem \ --load-certificate cert.pem --load-privkey key.pem \ --to-p12 --outder --outfile key.p12
To generate parameters for Diffie-Hellman key exchange, use the command:
$ certtool --generate-dh-params --outfile dh.pem --sec-param normal
Proxy certificate can be used to delegate your credential to a temporary, typically short-lived, certificate. To create one from the previously created certificate, first create a temporary key and then generate a proxy certificate for it, using the commands:
$ certtool --generate-privkey > proxy-key.pem $ certtool --generate-proxy --load-ca-privkey key.pem \ --load-privkey proxy-key.pem --load-certificate cert.pem \ --outfile proxy-cert.pem
To create an empty Certificate Revocation List (CRL) do:
$ certtool --generate-crl --load-ca-privkey x509-ca-key.pem \ --load-ca-certificate x509-ca.pem
To create a CRL that contains some revoked certificates, place the
certificates in a file and use --load-certificate
as follows:
$ certtool --generate-crl --load-ca-privkey x509-ca-key.pem \ --load-ca-certificate x509-ca.pem --load-certificate revoked-certs.pem
To verify a Certificate Revocation List (CRL) do:
$ certtool --verify-crl --load-ca-certificate x509-ca.pem < crl.pem
A template file can be used to avoid the interactive questions of certtool. Initially create a file named ’cert.cfg’ that contains the information about the certificate. The template can be used as below:
$ certtool --generate-certificate cert.pem --load-privkey key.pem \ --template cert.cfg \ --load-ca-certificate ca-cert.pem --load-ca-privkey ca-key.pem
An example certtool template file that can be used to generate a certificate request or a self signed certificate follows.
# X.509 Certificate options # # DN options # The organization of the subject. organization = "Koko inc." # The organizational unit of the subject. unit = "sleeping dept." # The locality of the subject. # locality = # The state of the certificate owner. state = "Attiki" # The country of the subject. Two letter code. country = GR # The common name of the certificate owner. cn = "Cindy Lauper" # A user id of the certificate owner. #uid = "clauper" # Set domain components #dc = "name" #dc = "domain" # If the supported DN OIDs are not adequate you can set # any OID here. # For example set the X.520 Title and the X.520 Pseudonym # by using OID and string pairs. #dn_oid = 2.5.4.12 Dr. #dn_oid = 2.5.4.65 jackal # This is deprecated and should not be used in new # certificates. # pkcs9_email = "none@none.org" # The serial number of the certificate serial = 007 # In how many days, counting from today, this certificate will expire. expiration_days = 700 # X.509 v3 extensions # A dnsname in case of a WWW server. #dns_name = "www.none.org" #dns_name = "www.morethanone.org" # A subject alternative name URI #uri = "http://www.example.com" # An IP address in case of a server. #ip_address = "192.168.1.1" # An email in case of a person email = "none@none.org" # Challenge password used in certificate requests challenge_passwd = 123456 # An URL that has CRLs (certificate revocation lists) # available. Needed in CA certificates. #crl_dist_points = "http://www.getcrl.crl/getcrl/" # Whether this is a CA certificate or not #ca # for microsoft smart card logon # key_purpose_oid = 1.3.6.1.4.1.311.20.2.2 ### Other predefined key purpose OIDs # Whether this certificate will be used for a TLS client #tls_www_client # Whether this certificate will be used for a TLS server #tls_www_server # Whether this certificate will be used to sign data (needed # in TLS DHE ciphersuites). signing_key # Whether this certificate will be used to encrypt data (needed # in TLS RSA ciphersuites). Note that it is preferred to use different # keys for encryption and signing. #encryption_key # Whether this key will be used to sign other certificates. #cert_signing_key # Whether this key will be used to sign CRLs. #crl_signing_key # Whether this key will be used to sign code. #code_signing_key # Whether this key will be used to sign OCSP data. #ocsp_signing_key # Whether this key will be used for time stamping. #time_stamping_key # Whether this key will be used for IPsec IKE operations. #ipsec_ike_key ### end of key purpose OIDs # When generating a certificate from a certificate # request, then honor the extensions stored in the request # and store them in the real certificate. #honor_crq_extensions # Path length contraint. Sets the maximum number of # certificates that can be used to certify this certificate. # (i.e. the certificate chain length) #path_len = -1 #path_len = 2 # OCSP URI # ocsp_uri = http://my.ocsp.server/ocsp # CA issuers URI # ca_issuers_uri = http://my.ca.issuer # Options for proxy certificates # proxy_policy_language = 1.3.6.1.5.5.7.21.1 # Options for generating a CRL # next CRL update will be in 43 days (wow) #crl_next_update = 43 # this is the 5th CRL by this CA #crl_number = 5
Next: Smart cards and HSMs, Previous: certtool Invocation, Up: More on certificate authentication [Contents][Index]
Ocsptool is a program that can parse and print information about OCSP requests/responses, generate requests and verify responses.
This section was generated by AutoGen,
using the agtexi-cmd
template and the option descriptions for the ocsptool
program.
This software is released under the GNU General Public License, version 3 or later.
This is the automatically generated usage text for ocsptool.
The text printed is the same whether selected with the help
option
(--help) or the more-help
option (--more-help). more-help
will print
the usage text by passing it through a pager program.
more-help
is disabled on platforms without a working
fork(2)
function. The PAGER
environment variable is
used to select the program, defaulting to more. Both will exit
with a status code of 0.
ocsptool - GnuTLS OCSP tool Usage: ocsptool [ -<flag> [<val>] | --<name>[{=| }<val>] ]... -d, --debug=num Enable debugging. - it must be in the range: 0 to 9999 -V, --verbose More verbose output - may appear multiple times --infile=file Input file - file must pre-exist --outfile=str Output file --ask[=arg] Ask an OCSP/HTTP server on a certificate validity - requires these options: load-cert load-issuer -e, --verify-response Verify response -i, --request-info Print information on a OCSP request -j, --response-info Print information on a OCSP response -q, --generate-request Generate an OCSP request --nonce Don't add nonce to OCSP request - disabled as '--no-nonce' --load-issuer=file Read issuer certificate from file - file must pre-exist --load-cert=file Read certificate to check from file - file must pre-exist --load-trust=file Read OCSP trust anchors from file - prohibits the option 'load-signer' - file must pre-exist --load-signer=file Read OCSP response signer from file - prohibits the option 'load-trust' - file must pre-exist --inder Use DER format for input certificates and private keys - disabled as '--no-inder' -Q, --load-request=file Read DER encoded OCSP request from file - file must pre-exist -S, --load-response=file Read DER encoded OCSP response from file - file must pre-exist -v, --version[=arg] output version information and exit -h, --help display extended usage information and exit -!, --more-help extended usage information passed thru pager Options are specified by doubled hyphens and their name or by a single hyphen and the flag character. Ocsptool is a program that can parse and print information about OCSP requests/responses, generate requests and verify responses. Please send bug reports to: <bug-gnutls@gnu.org>
This is the “enable debugging.” option. This option takes an argument number. Specifies the debug level.
This is the “ask an ocsp/http server on a certificate validity” option. This option takes an optional argument string server name|url.
This option has some usage constraints. It:
Connects to the specified HTTP OCSP server and queries on the validity of the loaded certificate.
One of the following exit values will be returned:
Successful program execution.
The operation failed or the command syntax was not valid.
To parse an OCSP request and print information about the content, the
-i
or --request-info
parameter may be used as follows.
The -Q
parameter specify the name of the file containing the
OCSP request, and it should contain the OCSP request in binary DER
format.
$ ocsptool -i -Q ocsp-request.der
The input file may also be sent to standard input like this:
$ cat ocsp-request.der | ocsptool --request-info
Similar to parsing OCSP requests, OCSP responses can be parsed using
the -j
or --response-info
as follows.
$ ocsptool -j -Q ocsp-response.der $ cat ocsp-response.der | ocsptool --response-info
The -q
or --generate-request
parameters are used to
generate an OCSP request. By default the OCSP request is written to
standard output in binary DER format, but can be stored in a file
using --outfile
. To generate an OCSP request the issuer of the
certificate to check needs to be specified with --load-issuer
and the certificate to check with --load-cert
. By default PEM
format is used for these files, although --inder
can be used to
specify that the input files are in DER format.
$ ocsptool -q --load-issuer issuer.pem --load-cert client.pem \ --outfile ocsp-request.der
When generating OCSP requests, the tool will add an OCSP extension
containing a nonce. This behaviour can be disabled by specifying
--no-nonce
.
To verify the signature in an OCSP response the -e
or
--verify-response
parameter is used. The tool will read an
OCSP response in DER format from standard input, or from the file
specified by --load-response
. The OCSP response is verified
against a set of trust anchors, which are specified using
--load-trust
. The trust anchors are concatenated certificates
in PEM format. The certificate that signed the OCSP response needs to
be in the set of trust anchors, or the issuer of the signer
certificate needs to be in the set of trust anchors and the OCSP
Extended Key Usage bit has to be asserted in the signer certificate.
$ ocsptool -e --load-trust issuer.pem \ --load-response ocsp-response.der
The tool will print status of verification.
It is possible to override the normal trust logic if you know that a
certain certificate is supposed to have signed the OCSP response, and
you want to use it to check the signature. This is achieved using
--load-signer
instead of --load-trust
. This will load
one certificate and it will be used to verify the signature in the
OCSP response. It will not check the Extended Key Usage bit.
$ ocsptool -e --load-signer ocsp-signer.pem \ --load-response ocsp-response.der
This approach is normally only relevant in two situations. The first
is when the OCSP response does not contain a copy of the signer
certificate, so the --load-trust
code would fail. The second
is if you want to avoid the indirect mode where the OCSP response
signer certificate is signed by a trust anchor.
Here is an example of how to generate an OCSP request for a
certificate and to verify the response. For illustration we’ll use
the blog.josefsson.org
host, which (as of writing) uses a
certificate from CACert. First we’ll use gnutls-cli
to get a
copy of the server certificate chain. The server is not required to
send this information, but this particular one is configured to do so.
$ echo | gnutls-cli -p 443 blog.josefsson.org --print-cert > chain.pem
Use a text editor on chain.pem
to create three files for each
separate certificates, called cert.pem
for the first
certificate for the domain itself, secondly issuer.pem
for the
intermediate certificate and root.pem
for the final root
certificate.
The domain certificate normally contains a pointer to where the OCSP
responder is located, in the Authority Information Access Information
extension. For example, from certtool -i < cert.pem
there is
this information:
Authority Information Access Information (not critical): Access Method: 1.3.6.1.5.5.7.48.1 (id-ad-ocsp) Access Location URI: http://ocsp.CAcert.org/
This means the CA support OCSP queries over HTTP. We are now ready to create a OCSP request for the certificate.
$ ocsptool --ask ocsp.CAcert.org --load-issuer issuer.pem \ --load-cert cert.pem --outfile ocsp-response.der
The request is sent via HTTP to the OCSP server address specified. If the address is ommited ocsptool will use the address stored in the certificate.
Next: Abstract key types, Previous: ocsptool Invocation, Up: More on certificate authentication [Contents][Index]
In this section we present the smart-card and hardware security module (HSM) support in GnuTLS using PKCS #11 [PKCS11]. Hardware security modules and smart cards provide a way to store private keys and perform operations on them without exposing them. This decouples cryptographic keys from the applications that use them and provide an additional security layer against cryptographic key extraction. Since this can also be achieved in software components such as in Gnome keyring, we will use the term security module to describe any cryptographic key separation subsystem.
PKCS #11 is plugin API allowing applications to access cryptographic operations on a security module, as well as to objects residing on it. PKCS #11 modules exist for hardware tokens such as smart cards9, the trusted platform module (TPM)10 as well as for software modules like Gnome Keyring. The objects residing on a security module may be certificates, public keys, private keys or secret keys. Of those certificates and public/private key pairs can be used with GnuTLS. PKCS #11’s main advantage is that it allows operations on private key objects such as decryption and signing without exposing the key.
Moreover PKCS #11 can be (ab)used to allow all applications in the same operating system to access shared cryptographic keys and certificates in a uniform way, as in Figure 6.2. That way applications could load their trusted certificate list, as well as user certificates from a common PKCS #11 module. Such a provider exists in the Gnome system, being the Gnome Keyring.
• PKCS11 Initialization: | ||
• Reading objects: | ||
• Writing objects: | ||
• Using a PKCS11 token with TLS: | ||
• p11tool Invocation: | Invoking p11tool |
Next: Reading objects, Up: Smart cards and HSMs [Contents][Index]
To allow all the GnuTLS applications to access PKCS #11 tokens
you can use a configuration per module, stored in /etc/pkcs11/modules/
.
These are the configuration files of p11-kit11.
For example a file that will load the OpenSC module, could be named
/etc/pkcs11/modules/opensc
and contain the following:
module: /usr/lib/opensc-pkcs11.so
If you use this file, then there is no need for other initialization in GnuTLS, except for the PIN and token functions. Those allow retrieving a PIN when accessing a protected object, such as a private key, as well as probe the user to insert the token. All the initialization functions are below.
flags: GNUTLS_PKCS11_FLAG_MANUAL
or GNUTLS_PKCS11_FLAG_AUTO
deprecated_config_file: either NULL or the location of a deprecated configuration file
This function will initialize the PKCS 11 subsystem in gnutls. It will
read configuration files if GNUTLS_PKCS11_FLAG_AUTO
is used or allow
you to independently load PKCS 11 modules using gnutls_pkcs11_add_provider()
if GNUTLS_PKCS11_FLAG_MANUAL
is specified.
Normally you don’t need to call this function since it is being called
by gnutls_global_init()
using the GNUTLS_PKCS11_FLAG_AUTO
. If other option
is required then it must be called before it.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
void gnutls_pkcs11_set_token_function (gnutls_pkcs11_token_callback_t fn, void * userdata)
void gnutls_pkcs11_set_pin_function (gnutls_pkcs11_pin_callback_t fn, void * userdata)
int gnutls_pkcs11_add_provider (const char * name, const char * params)
Note that due to limitations of PKCS #11 there are issues when multiple libraries are sharing a module. To avoid this problem GnuTLS uses p11-kit that provides a middleware to control access to resources over the multiple users.
Moreover PKCS #11 modules must be reinitialized on the child processes
after a fork
. GnuTLS provides gnutls_pkcs11_reinit
to be called for this purpose.
This function will reinitialize the PKCS 11 subsystem in gnutls.
This is required by PKCS 11 when an application uses fork()
. The
reinitialization function must be called on the child.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
Next: Writing objects, Previous: PKCS11 Initialization, Up: Smart cards and HSMs [Contents][Index]
All PKCS #11 objects are referenced by GnuTLS functions by URLs as described in [PKCS11URI]. This allows for a consistent naming of objects across systems and applications in the same system. For example a public key on a smart card may be referenced as:
pkcs11:token=Nikos;serial=307521161601031;model=PKCS%2315; \ manufacturer=EnterSafe;object=test1;objecttype=public;\ id=32f153f3e37990b08624141077ca5dec2d15faed
while the smart card itself can be referenced as:
pkcs11:token=Nikos;serial=307521161601031;model=PKCS%2315;manufacturer=EnterSafe
Objects stored in a PKCS #11 token can be extracted if they are not marked as sensitive. Usually only private keys are marked as sensitive and cannot be extracted, while certificates and other data can be retrieved. The functions that can be used to access objects are shown below.
int gnutls_pkcs11_obj_import_url (gnutls_pkcs11_obj_t cert, const char * url, unsigned int flags)
int gnutls_pkcs11_obj_export_url (gnutls_pkcs11_obj_t obj, gnutls_pkcs11_url_type_t detailed, char ** url)
crt: should contain a gnutls_pkcs11_obj_t
structure
itype: Denotes the type of information requested
output: where output will be stored
output_size: contains the maximum size of the output and will be overwritten with actual
This function will return information about the PKCS11 certificate
such as the label, id as well as token information where the key is
stored. When output is text it returns null terminated string
although output_size
contains the size of the actual data only.
Returns: GNUTLS_E_SUCCESS
(0) on success or a negative error code on error.
Since: 2.12.0
int gnutls_x509_crt_import_pkcs11 (gnutls_x509_crt_t crt, gnutls_pkcs11_obj_t pkcs11_crt)
int gnutls_x509_crt_import_pkcs11_url (gnutls_x509_crt_t crt, const char * url, unsigned int flags)
int gnutls_x509_crt_list_import_pkcs11 (gnutls_x509_crt_t * certs, unsigned int cert_max, gnutls_pkcs11_obj_t * const objs, unsigned int flags)
Properties of the physical token can also be accessed and altered with GnuTLS. For example data in a token can be erased (initialized), PIN can be altered, etc.
int gnutls_pkcs11_token_init (const char * token_url, const char * so_pin, const char * label)
int gnutls_pkcs11_token_get_url (unsigned int seq, gnutls_pkcs11_url_type_t detailed, char ** url)
int gnutls_pkcs11_token_get_info (const char * url, gnutls_pkcs11_token_info_t ttype, void * output, size_t * output_size)
int gnutls_pkcs11_token_get_flags (const char * url, unsigned int * flags)
int gnutls_pkcs11_token_set_pin (const char * token_url, const char * oldpin, const char * newpin, unsigned int flags)
The following examples demonstrate the usage of the API. The first example will list all available PKCS #11 tokens in a system and the latter will list all certificates in a token that have a corresponding private key.
int i; char* url; gnutls_global_init(); for (i=0;;i++) { ret = gnutls_pkcs11_token_get_url(i, &url); if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) break; if (ret < 0) exit(1); fprintf(stdout, "Token[%d]: URL: %s\n", i, url); gnutls_free(url); } gnutls_global_deinit();
/* This example code is placed in the public domain. */ #include <config.h> #include <gnutls/gnutls.h> #include <gnutls/pkcs11.h> #include <stdio.h> #include <stdlib.h> #define URL "pkcs11:URL" int main (int argc, char** argv) { gnutls_pkcs11_obj_t *obj_list; gnutls_x509_crt_t xcrt; unsigned int obj_list_size = 0; gnutls_datum_t cinfo; int ret; unsigned int i; obj_list_size = 0; ret = gnutls_pkcs11_obj_list_import_url (NULL, &obj_list_size, URL, GNUTLS_PKCS11_OBJ_ATTR_CRT_WITH_PRIVKEY, 0); if (ret < 0 && ret != GNUTLS_E_SHORT_MEMORY_BUFFER) return -1; /* no error checking from now on */ obj_list = malloc (sizeof (*obj_list) * obj_list_size); gnutls_pkcs11_obj_list_import_url (obj_list, &obj_list_size, URL, GNUTLS_PKCS11_OBJ_ATTR_CRT_WITH_PRIVKEY, 0); /* now all certificates are in obj_list */ for (i = 0; i < obj_list_size; i++) { gnutls_x509_crt_init (&xcrt); gnutls_x509_crt_import_pkcs11 (xcrt, obj_list[i]); gnutls_x509_crt_print (xcrt, GNUTLS_CRT_PRINT_FULL, &cinfo); fprintf (stdout, "cert[%d]:\n %s\n\n", i, cinfo.data); gnutls_free (cinfo.data); gnutls_x509_crt_deinit (xcrt); } return 0; }
Next: Using a PKCS11 token with TLS, Previous: Reading objects, Up: Smart cards and HSMs [Contents][Index]
With GnuTLS you can copy existing private keys and certificates
to a token. Note that when copying private keys it is recommended to mark
them as sensitive using the GNUTLS_PKCS11_OBJ_FLAG_MARK_SENSITIVE
to prevent its extraction. An object can be marked as private using the flag
GNUTLS_PKCS11_OBJ_FLAG_MARK_PRIVATE
, to require PIN to be
entered before accessing the object (for operations or otherwise).
token_url: A PKCS 11
URL specifying a token
key: A private key
label: A name to be used for the stored data
key_usage: One of GNUTLS_KEY_*
flags: One of GNUTLS_PKCS11_OBJ_* flags
This function will copy a private key into a PKCS 11
token specified by
a URL. It is highly recommended flags to contain GNUTLS_PKCS11_OBJ_FLAG_MARK_SENSITIVE
unless there is a strong reason not to.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
token_url: A PKCS 11
URL specifying a token
crt: A certificate
label: A name to be used for the stored data
flags: One of GNUTLS_PKCS11_OBJ_FLAG_*
This function will copy a certificate into a PKCS 11
token specified by
a URL. The certificate can be marked as trusted or not.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
object_url: The URL of the object to delete.
flags: One of GNUTLS_PKCS11_OBJ_* flags
This function will delete objects matching the given URL. Note that not all tokens support the delete operation.
Returns: On success, the number of objects deleted is returned, otherwise a negative error value.
Since: 2.12.0
Next: p11tool Invocation, Previous: Writing objects, Up: Smart cards and HSMs [Contents][Index]
It is possible to use a PKCS #11 token to a TLS session, as shown in ex:pkcs11-client. In addition the following functions can be used to load PKCS #11 key and certificates by specifying a PKCS #11 URL instead of a filename.
int gnutls_certificate_set_x509_trust_file (gnutls_certificate_credentials_t cred, const char * cafile, gnutls_x509_crt_fmt_t type)
int gnutls_certificate_set_x509_key_file (gnutls_certificate_credentials_t res, const char * certfile, const char * keyfile, gnutls_x509_crt_fmt_t type)
cred: is a gnutls_certificate_credentials_t
structure.
This function adds the system’s default trusted CAs in order to verify client or server certificates.
In the case the system is currently unsupported GNUTLS_E_UNIMPLEMENTED_FEATURE
is returned.
Returns: the number of certificates processed or a negative error code on error.
Since: 3.0
Previous: Using a PKCS11 token with TLS, Up: Smart cards and HSMs [Contents][Index]
Program that allows handling data from PKCS #11 smart cards and security modules.
To use PKCS #11 tokens with gnutls the configuration file /etc/gnutls/pkcs11.conf has to exist and contain a number of lines of the form ’load=/usr/lib/opensc-pkcs11.so’.
This section was generated by AutoGen,
using the agtexi-cmd
template and the option descriptions for the p11tool
program.
This software is released under the GNU General Public License, version 3 or later.
This is the automatically generated usage text for p11tool.
The text printed is the same whether selected with the help
option
(--help) or the more-help
option (--more-help). more-help
will print
the usage text by passing it through a pager program.
more-help
is disabled on platforms without a working
fork(2)
function. The PAGER
environment variable is
used to select the program, defaulting to more. Both will exit
with a status code of 0.
p11tool - GnuTLS PKCS #11 tool Usage: p11tool [ -<flag> [<val>] | --<name>[{=| }<val>] ]... [url] -d, --debug=num Enable debugging. - it must be in the range: 0 to 9999 --outfile=str Output file --list-tokens List all available tokens --export Export the object specified by the URL --list-mechanisms List all available mechanisms in a token --list-all List all available objects in a token --list-all-certs List all available certificates in a token --list-certs List all certificates that have an associated private key --list-all-privkeys List all available private keys in a token --list-all-trusted List all available certificates marked as trusted --initialize Initializes a PKCS #11 token --write Writes the loaded objects to a PKCS #11 token --delete Deletes the objects matching the PKCS #11 URL --generate-rsa Generate an RSA private-public key pair --generate-dsa Generate an RSA private-public key pair --generate-ecc Generate an RSA private-public key pair --label=str Sets a label for the write operation --trusted Marks the object to be written as trusted - disabled as '--no-trusted' --private Marks the object to be written as private - disabled as '--no-private' - enabled by default --login Force login to token - disabled as '--no-login' --detailed-url Print detailed URLs - disabled as '--no-detailed-url' --secret-key=str Provide a hex encoded secret key --load-privkey=file Private key file to use - file must pre-exist --load-pubkey=file Public key file to use - file must pre-exist --load-certificate=file Certificate file to use - file must pre-exist -8, --pkcs8 Use PKCS #8 format for private keys --bits=num Specify the number of bits for key generate --sec-param=str Specify the security level --inder Use DER/RAW format for input - disabled as '--no-inder' --inraw an alias for the 'inder' option --provider=file Specify the PKCS #11 provider library - file must pre-exist -v, --version[=arg] output version information and exit -h, --help display extended usage information and exit -!, --more-help extended usage information passed thru pager Options are specified by doubled hyphens and their name or by a single hyphen and the flag character. Operands and options may be intermixed. They will be reordered. Program that allows handling data from PKCS #11 smart cards and security modules. To use PKCS #11 tokens with gnutls the configuration file /etc/gnutls/pkcs11.conf has to exist and contain a number of lines of the form 'load=/usr/lib/opensc-pkcs11.so'. Please send bug reports to: <bug-gnutls@gnu.org>
This is the “enable debugging.” option. This option takes an argument number. Specifies the debug level.
This is the “writes the loaded objects to a pkcs #11 token” option. It can be used to write private keys, certificates or secret keys to a token.
This is the “generate an rsa private-public key pair” option. Generates an RSA private-public key pair on the specified token.
This is the “generate an rsa private-public key pair” option. Generates an RSA private-public key pair on the specified token.
This is the “generate an rsa private-public key pair” option. Generates an RSA private-public key pair on the specified token.
This is the “marks the object to be written as private” option.
This option has some usage constraints. It:
The written object will require a PIN to be used.
This is the “specify the security level” option. This option takes an argument string Security parameter. This is alternative to the bits option. Available options are [low, legacy, normal, high, ultra].
This is the “use der/raw format for input” option. Use DER/RAW format for input certificates and private keys.
This is an alias for the inder
option,
see the inder option documentation.
This is the “specify the pkcs #11 provider library” option. This option takes an argument file. This will override the default options in /etc/gnutls/pkcs11.conf
One of the following exit values will be returned:
Successful program execution.
The operation failed or the command syntax was not valid.
To view all tokens in your system use:
$ p11tool --list-tokens
To view all objects in a token use:
$ p11tool --login --list-all "pkcs11:TOKEN-URL"
To store a private key and a certificate in a token run:
$ p11tool --login --write "pkcs11:URL" --load-privkey key.pem \ --label "Mykey" $ p11tool --login --write "pkcs11:URL" --load-certificate cert.pem \ --label "Mykey"
Note that some tokens require the same label to be used for the certificate and its corresponding private key.
Previous: Smart cards and HSMs, Up: More on certificate authentication [Contents][Index]
Since there are many forms of a public or private keys supported by GnuTLS such as
X.509, OpenPGP, or PKCS #11 it is desirable to allow common operations
on them. For these reasons the abstract gnutls_privkey_t
and gnutls_pubkey_t
were
introduced in gnutls/abstract.h
header. Those types are initialized using a specific type of
key and then can be used to perform operations in an abstract way. For example in order
to sign an X.509 certificate with a key that resides in a token the following steps must be
used.
#inlude <gnutls/abstract.h> #inlude <gnutls/pkcs11.h> void sign_cert( gnutls_x509_crt_t to_be_signed) { gnutls_pkcs11_privkey_t ca_key; gnutls_x509_crt_t ca_cert; gnutls_privkey_t abs_key; /* load the PKCS #11 key and certificates */ gnutls_pkcs11_privkey_init(&ca_key); gnutls_pkcs11_privkey_import_url(ca_key, key_url); gnutls_x509_crt_init(&ca_cert); gnutls_x509_crt_import_pkcs11_url(&ca_cert, cert_url); /* initialize the abstract key */ gnutls_privkey_init(&abs_key); gnutls_privkey_import_pkcs11(abs_key, ca_key); /* sign the certificate to be signed */ gnutls_x509_crt_privkey_sign(to_be_signed, ca_cert, ca_key, GNUTLS_DIG_SHA256, 0); }
• Abstract public keys: | ||
• Abstract private keys: | ||
• Operations: |
Next: Abstract private keys, Up: Abstract key types [Contents][Index]
An abstract gnutls_pubkey_t
can be initialized
using the functions below. It can be imported through
an existing structure like gnutls_x509_crt_t
,
or through an ASN.1 encoding of the X.509 SubjectPublicKeyInfo
sequence.
key: The public key
crt: The certificate to be imported
flags: should be zero
This function will import the given public key to the abstract
gnutls_pubkey_t
structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
int gnutls_pubkey_import_openpgp (gnutls_pubkey_t key, gnutls_openpgp_crt_t crt, unsigned int flags)
int gnutls_pubkey_import_pkcs11 (gnutls_pubkey_t key, gnutls_pkcs11_obj_t obj, unsigned int flags)
int gnutls_pubkey_import_pkcs11_url (gnutls_pubkey_t key, const char * url, unsigned int flags)
int gnutls_pubkey_import_privkey (gnutls_pubkey_t key, gnutls_privkey_t pkey, unsigned int usage, unsigned int flags)
int gnutls_pubkey_import (gnutls_pubkey_t key, const gnutls_datum_t * data, gnutls_x509_crt_fmt_t format)
key: Holds the certificate
format: the format of output params. One of PEM or DER.
output_data: will contain a certificate PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the public key to DER or PEM format. The contents of the exported data is the SubjectPublicKeyInfo X.509 structure.
If the buffer provided is not long enough to hold the output, then
*output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will
be returned.
If the structure is PEM encoded, it will have a header of "BEGIN CERTIFICATE".
Returns: In case of failure a negative error code will be returned, and 0 on success.
Since: 2.12.0
Additional functions are available that will return information over a public key.
int gnutls_pubkey_get_pk_algorithm (gnutls_pubkey_t key, unsigned int * bits)
int gnutls_pubkey_get_preferred_hash_algorithm (gnutls_pubkey_t key, gnutls_digest_algorithm_t * hash, unsigned int * mand)
int gnutls_pubkey_get_key_id (gnutls_pubkey_t key, unsigned int flags, unsigned char * output_data, size_t * output_data_size)
Next: Operations, Previous: Abstract public keys, Up: Abstract key types [Contents][Index]
An abstract gnutls_privkey_t
can be initialized
using the functions below. It can be imported through
an existing structure like gnutls_x509_privkey_t
,
but unlike public keys it cannot be exported. That is
to allow abstraction over PKCS #11 keys that
are not extractable.
int gnutls_privkey_import_x509 (gnutls_privkey_t pkey, gnutls_x509_privkey_t key, unsigned int flags)
int gnutls_privkey_import_openpgp (gnutls_privkey_t pkey, gnutls_openpgp_privkey_t key, unsigned int flags)
int gnutls_privkey_import_pkcs11 (gnutls_privkey_t pkey, gnutls_pkcs11_privkey_t key, unsigned int flags)
int gnutls_privkey_get_pk_algorithm (gnutls_privkey_t key, unsigned int * bits)
gnutls_privkey_type_t gnutls_privkey_get_type (gnutls_privkey_t key)
In order to support cryptographic operations using an external API, the following function is provided. This allows for a simple extensibility API without resorting to PKCS #11.
pkey: The private key
pk: The public key algorithm
userdata: private data to be provided to the callbacks
sign_func: callback for signature operations
decrypt_func: callback for decryption operations
flags: Flags for the import
This function will associate the given callbacks with the
gnutls_privkey_t
structure. At least one of the two callbacks
must be non-null.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
Previous: Abstract private keys, Up: Abstract key types [Contents][Index]
The abstract key types can be used to access signing and signature verification operations with the underlying keys.
pubkey: Holds the public key
algo: The signature algorithm used
flags: should be 0 for now
data: holds the signed data
signature: contains the signature
This function will verify the given signed data, using the parameters from the certificate.
Returns: In case of a verification failure GNUTLS_E_PK_SIG_VERIFY_FAILED
is returned, and zero or positive code on success.
Since: 3.0
key: Holds the public key
algo: The signature algorithm used
flags: should be 0 for now
hash: holds the hash digest to be verified
signature: contains the signature
This function will verify the given signed digest, using the parameters from the public key.
Returns: In case of a verification failure GNUTLS_E_PK_SIG_VERIFY_FAILED
is returned, and zero or positive code on success.
Since: 3.0
key: Holds the public key
flags: should be 0 for now
plaintext: The data to be encrypted
ciphertext: contains the encrypted data
This function will encrypt the given data, using the public key.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
signer: Holds the key
hash: should be a digest algorithm
flags: should be 0 for now
data: holds the data to be signed
signature: will contain the signature allocate with gnutls_malloc()
This function will sign the given data using a signature algorithm supported by the private key. Signature algorithms are always used together with a hash functions. Different hash functions may be used for the RSA algorithm, but only the SHA family for the DSA keys.
Use gnutls_pubkey_get_preferred_hash_algorithm()
to determine
the hash algorithm.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
signer: Holds the signer’s key
hash_algo: The hash algorithm used
flags: zero for now
hash_data: holds the data to be signed
signature: will contain newly allocated signature
This function will sign the given hashed data using a signature algorithm supported by the private key. Signature algorithms are always used together with a hash functions. Different hash functions may be used for the RSA algorithm, but only SHA-XXX for the DSA keys.
Use gnutls_pubkey_get_preferred_hash_algorithm()
to determine
the hash algorithm.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: Holds the key
flags: zero for now
ciphertext: holds the data to be decrypted
plaintext: will contain the decrypted data, allocated with gnutls_malloc()
This function will decrypt the given data using the algorithm supported by the private key.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
Signing existing structures, such as certificates, CRLs, or certificate requests, as well as associating public keys with structures is also possible using the key abstractions.
crq: should contain a gnutls_x509_crq_t
structure
key: holds a public key
This function will set the public parameters from the given public key to the request.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
crt: should contain a gnutls_x509_crt_t
structure
key: holds a public key
This function will set the public parameters from the given public key to the request.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
int gnutls_x509_crt_privkey_sign (gnutls_x509_crt_t crt, gnutls_x509_crt_t issuer, gnutls_privkey_t issuer_key, gnutls_digest_algorithm_t dig, unsigned int flags)
int gnutls_x509_crl_privkey_sign (gnutls_x509_crl_t crl, gnutls_x509_crt_t issuer, gnutls_privkey_t issuer_key, gnutls_digest_algorithm_t dig, unsigned int flags)
int gnutls_x509_crq_privkey_sign (gnutls_x509_crq_t crq, gnutls_privkey_t key, gnutls_digest_algorithm_t dig, unsigned int flags)
Next: GnuTLS application examples, Previous: More on certificate authentication, Up: Top [Contents][Index]
Next: Preparation, Up: How to use GnuTLS in applications [Contents][Index]
• General idea: | ||
• Error handling: | ||
• Common types: | ||
• Debugging and auditing: | ||
• Thread safety: | ||
• Callback functions: |
Next: Error handling, Up: Introduction to the library [Contents][Index]
A brief description of how GnuTLS works internally is shown at Figure 7.1. This section may become more clear after having read the rest of this section. As shown in the figure, there is a read-only global state that is initialized once by the global initialization function. This global structure, among others, contains the memory allocation functions used, and structures needed for the ASN.1 parser. This structure is never modified by any GnuTLS function, except for the deinitialization function which frees all allocated memory and is called after the program has permanently finished using GnuTLS.
The credentials structures are used by the authentication methods, such as certificate authentication. They store certificates, privates keys, and other information that is needed to prove the identity to the peer, and/or verify the indentity of the peer. The information stored in the credentials structures is initialized once and then can be shared by many TLS sessions.
A GnuTLS session contains all the required information to handle one secure connection. The session communicates with the peers using the provided functions of the transport layer. Every session has a unique session ID shared with the peer.
Since TLS sessions can be resumed, servers need a database back-end to hold the session’s parameters. Every GnuTLS session after a successful handshake calls the appropriate back-end function (see resume) to store the newly negotiated session. The session database is examined by the server just after having received the client hello12, and if the session ID sent by the client, matches a stored session, the stored session will be retrieved, and the new session will be a resumed one, and will share the same session ID with the previous one.
Next: Common types, Previous: General idea, Up: Introduction to the library [Contents][Index]
In GnuTLS most functions return an integer type as a result. In almost all cases a zero or a positive number means success, and a negative number indicates failure, or a situation that some action has to be taken. Thus negative error codes may be fatal or not.
Fatal errors terminate the connection immediately and further sends
and receives will be disallowed. Such an example is
GNUTLS_E_DECRYPTION_FAILED
. Non-fatal errors may warn about
something, i.e., a warning alert was received, or indicate the some
action has to be taken. This is the case with the error code
GNUTLS_E_REHANDSHAKE
returned by gnutls_record_recv.
This error code indicates that the server requests a re-handshake. The
client may ignore this request, or may reply with an alert. You can
test if an error code is a fatal one by using the
gnutls_error_is_fatal.
All errors can be converted to a descriptive string using gnutls_strerror.
If any non fatal errors, that require an action, are to be returned by
a function, these error codes will be documented in the function’s
reference. For example the error codes GNUTLS_E_WARNING_ALERT_RECEIVED
and GNUTLS_E_FATAL_ALERT_RECEIVED
that may returned when receiving data, should be handled by notifying the
user of the alert (as explained in Handling alerts).
See Error codes, for a description of the available error codes.
Next: Debugging and auditing, Previous: Error handling, Up: Introduction to the library [Contents][Index]
Several functions in GnuTLS use gnutls_datum_t
which is
convenient way to combine a pointer to data and data’s size. Its definition is
shown below.
typedef struct { unsigned char *data; unsigned int size; } gnutls_datum_t;
Other functions that require data for scattered read use a structure similar
to struct iovec
typically used by readv
. It is shown
below.
typedef struct { void *iov_base; /* Starting address */ size_t iov_len; /* Number of bytes to transfer */ } giovec_t;
Next: Thread safety, Previous: Common types, Up: Introduction to the library [Contents][Index]
In many cases things may not go as expected and further information, to assist debugging, from GnuTLS is desired. Those are the cases where the gnutls_global_set_log_level and gnutls_global_set_log_function are to be used. Those will print verbose information on the GnuTLS functions internal flow.
void gnutls_global_set_log_level (int level)
void gnutls_global_set_log_function (gnutls_log_func log_func)
When debugging is not required, important issues, such as detected attacks on the protocol still need to be logged. This is provided by the logging function set by gnutls_global_set_audit_log_function. The provided function will receive an message and the corresponding TLS session. The session information might be used to derive IP addresses or other information about the peer involved.
log_func: it is the audit log function
This is the function where you set the logging function gnutls is
going to use. This is different from gnutls_global_set_log_function()
because it will report the session of the event if any. Note that
that session might be null if there is no corresponding TLS session.
gnutls_audit_log_func
is of the form,
void (*gnutls_audit_log_func)( gnutls_session_t, int level, const char*);
Since: 3.0
Next: Callback functions, Previous: Debugging and auditing, Up: Introduction to the library [Contents][Index]
The GnuTLS library is thread safe by design, meaning that objects of the library such as TLS sessions, can be safely divided across threads as long as a single thread accesses a single object. This is sufficient to support a server which handles several sessions per thread. If, however, an object needs to be shared across threads then access must be protected with a mutex. Read-only access to objects, for example the credentials holding structures, is also thread-safe.
The random generator of the cryptographic back-end, is not thread safe and requires
mutex locks which are setup by GnuTLS.
Applications can either call gnutls_global_init which will initialize the default
operating system provided locks (i.e. pthreads
on GNU/Linux and
CriticalSection
on Windows), or manually specify the locking system using
the function gnutls_global_set_mutex before calling gnutls_global_init.
Setting mutexes manually is recommended
only for applications that have full control of the underlying libraries. If this
is not the case, the use of the operating system defaults is recommended. An example of
non-native thread usage is shown below.
#include <gnutls/gnutls.h> int main() { /* When the system mutexes are not to be used * gnutls_global_set_mutex() must be called explicitly */ gnutls_global_set_mutex (mutex_init, mutex_deinit, mutex_lock, mutex_unlock); gnutls_global_init(); }
init: mutex initialization function
deinit: mutex deinitialization function
lock: mutex locking function
unlock: mutex unlocking function
With this function you are allowed to override the default mutex locks used in some parts of gnutls and dependent libraries. This function should be used if you have complete control of your program and libraries. Do not call this function from a library. Instead only initialize gnutls and the default OS mutex locks will be used.
This function must be called before gnutls_global_init()
.
Since: 2.12.0
Previous: Thread safety, Up: Introduction to the library [Contents][Index]
There are several cases where GnuTLS may need out of band input from your program. This is now implemented using some callback functions, which your program is expected to register.
An example of this type of functions are the push and pull callbacks which are used to specify the functions that will retrieve and send data to the transport layer.
void gnutls_transport_set_push_function (gnutls_session_t session, gnutls_push_func push_func)
void gnutls_transport_set_pull_function (gnutls_session_t session, gnutls_pull_func pull_func)
Other callback functions may require more complicated input and data
to be allocated. Such an example is
gnutls_srp_set_server_credentials_function.
All callbacks should allocate and free memory using
gnutls_malloc
and gnutls_free
.
Next: Session initialization, Previous: Introduction to the library, Up: How to use GnuTLS in applications [Contents][Index]
To use GnuTLS, you have to perform some changes to your sources and your build system. The necessary changes are explained in the following subsections.
• Headers: | ||
• Initialization: | ||
• Version check: | ||
• Building the source: |
Next: Initialization, Up: Preparation [Contents][Index]
All the data types and functions of the GnuTLS library are defined in the header file gnutls/gnutls.h. This must be included in all programs that make use of the GnuTLS library.
Next: Version check, Previous: Headers, Up: Preparation [Contents][Index]
GnuTLS must be initialized before it can be used. The library is initialized by calling gnutls_global_init. The resources allocated by the initialization process can be released if the application no longer has a need to call GnuTLS functions, this is done by calling gnutls_global_deinit.
In order to take advantage of the internationalization features in
GnuTLS, such as translated error messages, the application must set
the current locale using setlocale
before initializing GnuTLS.
Next: Building the source, Previous: Initialization, Up: Preparation [Contents][Index]
It is often desirable to check that the version of ‘gnutls’ used is indeed one which fits all requirements. Even with binary compatibility new features may have been introduced but due to problem with the dynamic linker an old version is actually used. So you may want to check that the version is okay right after program start-up. See the function gnutls_check_version.
Previous: Version check, Up: Preparation [Contents][Index]
If you want to compile a source file including the gnutls/gnutls.h header file, you must make sure that the compiler can find it in the directory hierarchy. This is accomplished by adding the path to the directory in which the header file is located to the compilers include file search path (via the -I option).
However, the path to the include file is determined at the time the
source is configured. To solve this problem, the library uses the
external package pkg-config
that knows the path to the
include file and other configuration options. The options that need
to be added to the compiler invocation at compile time are output by
the --cflags option to pkg-config gnutls
. The
following example shows how it can be used at the command line:
gcc -c foo.c `pkg-config gnutls --cflags`
Adding the output of ‘pkg-config gnutls --cflags’ to the compilers command line will ensure that the compiler can find the gnutls/gnutls.h header file.
A similar problem occurs when linking the program with the library.
Again, the compiler has to find the library files. For this to work,
the path to the library files has to be added to the library search
path (via the -L option). For this, the option
--libs to pkg-config gnutls
can be used. For
convenience, this option also outputs all other options that are
required to link the program with the library (for instance, the
‘-ltasn1’ option). The example shows how to link foo.o
with the library to a program foo
.
gcc -o foo foo.o `pkg-config gnutls --libs`
Of course you can also combine both examples to a single command by
specifying both options to pkg-config
:
gcc -o foo foo.c `pkg-config gnutls --cflags --libs`
When a program uses the GNU autoconf system, then the following line or similar can be used to detect the presence of GnuTLS.
PKG_CHECK_MODULES([LIBGNUTLS], [gnutls >= 3.0.0]) AC_SUBST([LIBGNUTLS_CFLAGS]) AC_SUBST([LIBGNUTLS_LIBS])
Next: Associating the credentials, Previous: Preparation, Up: How to use GnuTLS in applications [Contents][Index]
In the previous sections we have discussed the global initialization required for GnuTLS as well as the initialization required for each authentication method’s credentials (see Authentication). In this section we elaborate on the TLS or DTLS session initiation. Each session is initialized using gnutls_init which among others is used to specify the type of the connection (server or client), and the underlying protocol type, i.e., datagram (UDP) or reliable (TCP).
session: is a pointer to a gnutls_session_t
structure.
flags: indicate if this session is to be used for server or client.
This function initializes the current session to null. Every
session must be initialized before use, so internal structures can
be allocated. This function allocates structures which can only
be free’d by calling gnutls_deinit()
. Returns GNUTLS_E_SUCCESS
(0) on success.
flags
can be one of GNUTLS_CLIENT
and GNUTLS_SERVER
. For a DTLS
entity, the flags GNUTLS_DATAGRAM
and GNUTLS_NONBLOCK
are
also available. The latter flag will enable a non-blocking
operation of the DTLS timers.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
After the session initialization details on the allowed ciphersuites and protocol versions should be set using the priority functions such as gnutls_priority_set_direct. We elaborate on them in Priority Strings. The credentials used for the key exchange method, such as certificates or usernames and passwords should also be associated with the session current session using gnutls_credentials_set.
session: is a gnutls_session_t
structure.
type: is the type of the credentials
cred: is a pointer to a structure.
Sets the needed credentials for the specified type. Eg username,
password - or public and private keys etc. The cred
parameter is
a structure that depends on the specified type and on the current
session (client or server).
In order to minimize memory usage, and share credentials between
several threads gnutls keeps a pointer to cred, and not the whole
cred structure. Thus you will have to keep the structure allocated
until you call gnutls_deinit()
.
For GNUTLS_CRD_ANON
, cred
should be
gnutls_anon_client_credentials_t
in case of a client. In case of
a server it should be gnutls_anon_server_credentials_t
.
For GNUTLS_CRD_SRP
, cred
should be gnutls_srp_client_credentials_t
in case of a client, and gnutls_srp_server_credentials_t
, in case
of a server.
For GNUTLS_CRD_CERTIFICATE
, cred
should be
gnutls_certificate_credentials_t
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
Next: Setting up the transport layer, Previous: Session initialization, Up: How to use GnuTLS in applications [Contents][Index]
• Certificate credentials: | ||
• SRP credentials: | ||
• PSK credentials: | ||
• Anonymous credentials: |
Each authentication method is associated with a key exchange method, and a credentials type. The contents of the credentials is method-dependent, e.g. certificates for certificate authentication and should be initialized and associated with a session (see gnutls_credentials_set). A mapping of the key exchange methods with the credential types is shown in Table 7.1.
Authentication method | Key exchange | Client credentials | Server credentials |
---|---|---|---|
Certificate | KX_RSA ,
KX_DHE_RSA ,
KX_DHE_DSS ,
KX_ECDHE_RSA ,
KX_ECDHE_ECDSA ,
KX_RSA_EXPORT | CRD_CERTIFICATE | CRD_CERTIFICATE |
Password and certificate | KX_SRP_RSA , KX_SRP_DSS | CRD_SRP | CRD_CERTIFICATE , CRD_SRP |
Password | KX_SRP | CRD_SRP | CRD_SRP |
Anonymous | KX_ANON_DH ,
KX_ANON_ECDH | CRD_ANON | CRD_ANON |
Pre-shared key | KX_PSK ,
KX_DHE_PSK , KX_ECDHE_PSK | CRD_PSK | CRD_PSK |
Table 7.1: Key exchange algorithms and the corresponding credential types.
Next: SRP credentials, Up: Associating the credentials [Contents][Index]
When using certificates the server is required to have at least one certificate and private key pair. Clients may not hold such a pair, but a server could require it. In this section we discuss general issues applying to both client and server certificates. The next section will elaborate on issues arising from client authentication only.
int gnutls_certificate_allocate_credentials (gnutls_certificate_credentials_t * res)
void gnutls_certificate_free_credentials (gnutls_certificate_credentials_t sc)
After the credentials structures are initialized, the certificate and key pair must be loaded. This occurs before any TLS session is initialized, and the same structures are reused for multiple sessions. Depending on the certificate type different loading functions are available, as shown below. For X.509 certificates, the functions will accept and use a certificate chain that leads to a trusted authority. The certificate chain must be ordered in such way that every certificate certifies the one before it. The trusted authority’s certificate need not to be included since the peer should possess it already.
int gnutls_certificate_set_x509_key_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * cert, const gnutls_datum_t * key, gnutls_x509_crt_fmt_t type)
int gnutls_certificate_set_x509_key (gnutls_certificate_credentials_t res, gnutls_x509_crt_t * cert_list, int cert_list_size, gnutls_x509_privkey_t key)
int gnutls_certificate_set_x509_key_file (gnutls_certificate_credentials_t res, const char * certfile, const char * keyfile, gnutls_x509_crt_fmt_t type)
int gnutls_certificate_set_openpgp_key_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * cert, const gnutls_datum_t * key, gnutls_openpgp_crt_fmt_t format)
int gnutls_certificate_set_openpgp_key (gnutls_certificate_credentials_t res, gnutls_openpgp_crt_t crt, gnutls_openpgp_privkey_t pkey)
int gnutls_certificate_set_openpgp_key_file (gnutls_certificate_credentials_t res, const char * certfile, const char * keyfile, gnutls_openpgp_crt_fmt_t format)
int gnutls_certificate_set_key (gnutls_certificate_credentials_t res, const char** names, int names_size, gnutls_pcert_st * pcert_list, int pcert_list_size, gnutls_privkey_t key)
If multiple certificates are used with the functions above each client’s request will be served with the certificate that matches the requested name (see Server name indication).
As an alternative to loading from files or buffers, a callback may be used for the server or the client to specify the certificate and the key at the handshake time. In that case a certificate should be selected according the peer’s signature algorithm preferences. To get those preferences use gnutls_sign_algorithm_get_requested. Both functions are shown below.
void gnutls_certificate_set_retrieve_function (gnutls_certificate_credentials_t cred, gnutls_certificate_retrieve_function * func)
void gnutls_certificate_set_retrieve_function2 (gnutls_certificate_credentials_t cred, gnutls_certificate_retrieve_function2 * func)
int gnutls_sign_algorithm_get_requested (gnutls_session_t session, size_t indx, gnutls_sign_algorithm_t * algo)
The functions above do not handle the requested server name automatically. A server would need to check the name requested by the client using gnutls_server_name_get, and serve the appropriate certificate.
In a handshake, the negotiated cipher suite depends on the
certificate’s parameters, so some key exchange methods might not be
available with all certificates. GnuTLS will disable
ciphersuites that are not compatible with the key, or the enabled
authentication methods. For example keys marked as sign-only, will
not be able to access the plain RSA ciphersuites, that require
decryption. It is not recommended to use RSA keys for both
signing and encryption. If possible use a different key for the
DHE-RSA
which uses signing and RSA
that requires decryption.
All the key exchange methods shown in Table 4.1 are
available in certificate authentication.
If a certificate is to be requested from the client during the handshake, the server will send a certificate request message. This behavior is controlled gnutls_certificate_server_set_request. The request contains a list of the acceptable by the server certificate signers. This list is constructed using the trusted certificate authorities of the server. In cases where the server supports a large number of certificate authorities it makes sense not to advertise all of the names to save bandwidth. That can be controlled using the function gnutls_certificate_send_x509_rdn_sequence. This however will have the side-effect of not restricting the client to certificates signed by server’s acceptable signers.
session: is a gnutls_session_t
structure.
req: is one of GNUTLS_CERT_REQUEST, GNUTLS_CERT_REQUIRE
This function specifies if we (in case of a server) are going to
send a certificate request message to the client. If req
is
GNUTLS_CERT_REQUIRE then the server will return an error if the
peer does not provide a certificate. If you do not call this
function then the client will not be asked to send a certificate.
session: is a pointer to a gnutls_session_t
structure.
status: is 0 or 1
If status is non zero, this function will order gnutls not to send the rdnSequence in the certificate request message. That is the server will not advertise its trusted CAs to the peer. If status is zero then the default behaviour will take effect, which is to advertise the server’s trusted CAs.
This function has no effect in clients, and in authentication methods other than certificate with X.509 certificates.
Certificate verification is possible by loading the trusted authorities into the credentials structure by using the following functions, applicable to X.509 and OpenPGP certificates.
int gnutls_certificate_set_x509_trust_file (gnutls_certificate_credentials_t cred, const char * cafile, gnutls_x509_crt_fmt_t type)
int gnutls_certificate_set_openpgp_keyring_file (gnutls_certificate_credentials_t c, const char * file, gnutls_openpgp_crt_fmt_t format)
The peer’s certificate is not automatically verified and one should call gnutls_certificate_verify_peers2 after a successful handshake to verify the certificate’s signature. Alternative the verification can occur during the handshake by using gnutls_certificate_set_verify_function.
In order to report a detailed verification output, an alternative way has to be used. For that, one should call gnutls_certificate_get_peers to obtain the raw certificate of the peer and verify it using the functions discussed in X.509 certificates.
session: is a gnutls session
status: is the output of the verification
This function will try to verify the peer’s certificate and return
its status (trusted, invalid etc.). The value of status
should
be one or more of the gnutls_certificate_status_t enumerated
elements bitwise or’d. To avoid denial of service attacks some
default upper limits regarding the certificate key size and chain
size are set. To override them use
gnutls_certificate_set_verify_limits()
.
Note that you must also check the peer’s name in order to check if the verified certificate belongs to the actual peer.
This function uses gnutls_x509_crt_list_verify()
with the CAs in
the credentials as trusted CAs.
Returns: a negative error code on error and GNUTLS_E_SUCCESS
(0) on success.
cred: is a gnutls_certificate_credentials_t
structure.
func: is the callback function
This function sets a callback to be called when peer’s certificate has been received in order to verify it on receipt rather than doing after the handshake is completed.
The callback’s function prototype is: int (*callback)(gnutls_session_t);
If the callback function is provided then gnutls will call it, in the
handshake, just after the certificate message has been received.
To verify or obtain the certificate the gnutls_certificate_verify_peers2()
,
gnutls_certificate_type_get()
, gnutls_certificate_get_peers()
functions
can be used.
The callback function should return 0 for the handshake to continue or non-zero to terminate.
Since: 2.10.0
Next: PSK credentials, Previous: Certificate credentials, Up: Associating the credentials [Contents][Index]
The initialization functions in SRP credentials differ between client and server. Clients supporting SRP should set the username and password prior to connection, to the credentials structure. Alternatively gnutls_srp_set_client_credentials_function may be used instead, to specify a callback function that should return the SRP username and password. The callback is called once during the TLS handshake.
int gnutls_srp_allocate_server_credentials (gnutls_srp_server_credentials_t * sc)
int gnutls_srp_allocate_client_credentials (gnutls_srp_client_credentials_t * sc)
void gnutls_srp_free_server_credentials (gnutls_srp_server_credentials_t sc)
void gnutls_srp_free_client_credentials (gnutls_srp_client_credentials_t sc)
int gnutls_srp_set_client_credentials (gnutls_srp_client_credentials_t res, const char * username, const char * password)
cred: is a gnutls_srp_server_credentials_t
structure.
func: is the callback function
This function can be used to set a callback to retrieve the username and password for client SRP authentication. The callback’s function form is:
int (*callback)(gnutls_session_t, char** username, char**password);
The username
and password
must be allocated using
gnutls_malloc()
. username
and password
should be ASCII strings
or UTF-8 strings prepared using the "SASLprep" profile of
"stringprep".
The callback function will be called once per handshake before the initial hello message is sent.
The callback should not return a negative error code the second time called, since the handshake procedure will be aborted.
The callback function should return 0 on success. -1 indicates an error.
In server side the default behavior of GnuTLS is to read the usernames and SRP verifiers from password files. These password file format is compatible the with the Stanford srp libraries format. If a different password file format is to be used, then gnutls_srp_set_server_credentials_function should be called, to set an appropriate callback.
res: is a gnutls_srp_server_credentials_t
structure.
password_file: is the SRP password file (tpasswd)
password_conf_file: is the SRP password conf file (tpasswd.conf)
This function sets the password files, in a
gnutls_srp_server_credentials_t
structure. Those password files
hold usernames and verifiers and will be used for SRP
authentication.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
cred: is a gnutls_srp_server_credentials_t
structure.
func: is the callback function
This function can be used to set a callback to retrieve the user’s SRP credentials. The callback’s function form is:
int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t* salt, gnutls_datum_t *verifier, gnutls_datum_t* g, gnutls_datum_t* n);
username
contains the actual username.
The salt
, verifier
, generator
and prime
must be filled
in using the gnutls_malloc()
. For convenience prime
and generator
may also be one of the static parameters defined in gnutls.h.
In case the callback returned a negative number then gnutls will assume that the username does not exist.
In order to prevent attackers from guessing valid usernames, if a user does not exist, g and n values should be filled in using a random user’s parameters. In that case the callback must return the special value (1).
The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error.
Next: Anonymous credentials, Previous: SRP credentials, Up: Associating the credentials [Contents][Index]
The initialization functions in PSK credentials differ between client and server.
int gnutls_psk_allocate_server_credentials (gnutls_psk_server_credentials_t * sc)
int gnutls_psk_allocate_client_credentials (gnutls_psk_client_credentials_t * sc)
void gnutls_psk_free_server_credentials (gnutls_psk_server_credentials_t sc)
void gnutls_psk_free_client_credentials (gnutls_psk_client_credentials_t sc)
Clients supporting PSK should supply the username and key before a TLS session is established. Alternatively gnutls_psk_set_client_credentials_function can be used to specify a callback function. This has the advantage that the callback will be called only if PSK has been negotiated.
int gnutls_psk_set_client_credentials (gnutls_psk_client_credentials_t res, const char * username, const gnutls_datum_t * key, gnutls_psk_key_flags flags)
cred: is a gnutls_psk_server_credentials_t
structure.
func: is the callback function
This function can be used to set a callback to retrieve the username and password for client PSK authentication. The callback’s function form is: int (*callback)(gnutls_session_t, char** username, gnutls_datum_t* key);
The username
and key
->data must be allocated using gnutls_malloc()
.
username
should be ASCII strings or UTF-8 strings prepared using
the "SASLprep" profile of "stringprep".
The callback function will be called once per handshake.
The callback function should return 0 on success. -1 indicates an error.
In server side the default behavior of GnuTLS is to read the usernames and PSK keys from a password file. The password file should contain usernames and keys in hexadecimal format. The name of the password file can be stored to the credentials structure by calling gnutls_psk_set_server_credentials_file. If a different password file format is to be used, then a callback should be set instead by gnutls_psk_set_server_credentials_function.
The server can help the client chose a suitable username and password, by sending a hint. Note that there is no common profile for the PSK hint and applications are discouraged to use it. A server, may specify the hint by calling gnutls_psk_set_server_credentials_hint. The client can retrieve the hint, for example in the callback function, using gnutls_psk_client_get_hint.
res: is a gnutls_psk_server_credentials_t
structure.
password_file: is the PSK password file (passwd.psk)
This function sets the password file, in a
gnutls_psk_server_credentials_t
structure. This password file
holds usernames and keys and will be used for PSK authentication.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
void gnutls_psk_set_server_credentials_function (gnutls_psk_server_credentials_t cred, gnutls_psk_server_credentials_function * func)
int gnutls_psk_set_server_credentials_hint (gnutls_psk_server_credentials_t res, const char * hint)
const char * gnutls_psk_client_get_hint (gnutls_session_t session)
Previous: PSK credentials, Up: Associating the credentials [Contents][Index]
The key exchange methods for anonymous authentication might require Diffie-Hellman parameters to be generated by the server and associated with an anonymous credentials structure. Check Parameter generation for more information. The initialization functions for the credentials are shown below.
int gnutls_anon_allocate_server_credentials (gnutls_anon_server_credentials_t * sc)
int gnutls_anon_allocate_client_credentials (gnutls_anon_client_credentials_t * sc)
void gnutls_anon_free_server_credentials (gnutls_anon_server_credentials_t sc)
void gnutls_anon_free_client_credentials (gnutls_anon_client_credentials_t sc)
Next: TLS handshake, Previous: Associating the credentials, Up: How to use GnuTLS in applications [Contents][Index]
The next step is to setup the underlying transport layer details. The Berkeley sockets are implicitly used by GnuTLS, thus a call to gnutls_transport_set_ptr2 would be sufficient to specify the socket descriptor.
session: is a gnutls_session_t
structure.
recv_ptr: is the value for the pull function
send_ptr: is the value for the push function
Used to set the first argument of the transport function (for push and pull callbacks). In berkeley style sockets this function will set the connection descriptor. With this function you can use two different pointers for receiving and sending.
void gnutls_transport_set_ptr (gnutls_session_t session, gnutls_transport_ptr_t ptr)
If however another transport layer than TCP is selected, then the following functions have to be specified.
session: is a gnutls_session_t
structure.
push_func: a callback function similar to write()
This is the function where you set a push function for gnutls to use in order to send data. If you are going to use berkeley style sockets, you do not need to use this function since the default send(2) will probably be ok. Otherwise you should specify this function for gnutls to be able to send data. The callback should return a positive number indicating the bytes sent, and -1 on error.
push_func
is of the form,
ssize_t (*gnutls_push_func)(gnutls_transport_ptr_t, const void*, size_t);
session: is a gnutls_session_t
structure.
vec_func: a callback function similar to writev()
Using this function you can override the default writev(2)
function for gnutls to send data. Setting this callback
instead of gnutls_transport_set_push_function()
is recommended
since it introduces less overhead in the TLS handshake process.
vec_func
is of the form,
ssize_t (*gnutls_vec_push_func) (gnutls_transport_ptr_t, const giovec_t * iov, int iovcnt);
Since: 2.12.0
session: is a gnutls_session_t
structure.
pull_func: a callback function similar to read()
This is the function where you set a function for gnutls to receive data. Normally, if you use berkeley style sockets, do not need to use this function since the default recv(2) will probably be ok. The callback should return 0 on connection termination, a positive number indicating the number of bytes received, and -1 on error.
gnutls_pull_func
is of the form,
ssize_t (*gnutls_pull_func)(gnutls_transport_ptr_t, void*, size_t);
The functions above accept a callback function which
should return the number of bytes written, or -1 on
error and should set errno
appropriately.
In some environments, setting errno
is unreliable. For example
Windows have several errno variables in different CRTs, or in other
systems it may be a non thread-local variable. If this is a concern to
you, call gnutls_transport_set_errno with the intended errno
value instead of setting errno
directly.
session: is a gnutls_session_t
structure.
err: error value to store in session-specific errno variable.
Store err
in the session-specific errno variable. Useful values
for err
is EAGAIN and EINTR, other values are treated will be
treated as real errors in the push/pull function.
This function is useful in replacement push and pull functions set by
gnutls_transport_set_push_function()
and
gnutls_transport_set_pull_function()
under Windows, where the
replacements may not have access to the same errno
variable that is used by GnuTLS (e.g., the application is linked to
msvcr71.dll and gnutls is linked to msvcrt.dll).
GnuTLS currently only interprets the EINTR, EAGAIN and EMSGSIZE errno values and returns the corresponding GnuTLS error codes:
GNUTLS_E_INTERRUPTED
GNUTLS_E_AGAIN
GNUTLS_E_LARGE_PACKET
The EINTR and EAGAIN values are returned by interrupted system calls, or when non blocking IO is used. All GnuTLS functions can be resumed (called again), if any of the above error codes is returned. The EMSGSIZE value is returned when attempting to send a large datagram.
In the case of DTLS it is also desirable to override the generic
transport functions with functions that emulate the operation
of recvfrom
and sendto
. In addition
DTLS requires timers during the receive of a handshake
message, set using the gnutls_transport_set_pull_timeout_function
function. To check the retransmission timers the function
gnutls_dtls_get_timeout is provided, which returns the time
remaining until the next retransmission, or better the time until
gnutls_handshake should be called again.
session: is a gnutls_session_t
structure.
func: a callback function
This is the function where you set a function for gnutls to know
whether data are ready to be received. It should wait for data a
given time frame in milliseconds. The callback should return 0 on
timeout, a positive number if data can be received, and -1 on error.
You’ll need to override this function if select()
is not suitable
for the provided transport calls.
The callback function is used in DTLS only.
gnutls_pull_timeout_func
is of the form,
ssize_t (*gnutls_pull_timeout_func)(gnutls_transport_ptr_t, unsigned int ms);
Since: 3.0
session: is a gnutls_session_t
structure.
This function will return the milliseconds remaining
for a retransmission of the previously sent handshake
message. This function is useful when DTLS is used in
non-blocking mode, to estimate when to call gnutls_handshake()
if no packets have been received.
Returns: the remaining time in milliseconds.
Since: 3.0
• Asynchronous operation: | ||
• DTLS sessions: |
Next: DTLS sessions, Up: Setting up the transport layer [Contents][Index]
GnuTLS can be used with asynchronous socket or event-driven programming.
The approach is similar to using Berkeley sockets under such an environment.
The blocking, due to network interaction, calls such as
gnutls_handshake, gnutls_record_recv,
can be set to non-blocking by setting the underlying sockets to non-blocking.
If other push and pull functions are setup, then they should behave the same
way as recv
and send
when used in a non-blocking
way, i.e., set errno to EAGAIN
. Since, during a TLS protocol session
GnuTLS does not block except for network interaction, the non blocking
EAGAIN
errno will be propagated and GnuTLS functions
will return the GNUTLS_E_AGAIN
error code. Such calls can be resumed the
same way as a system call would.
The only exception is gnutls_record_send,
which if interrupted subsequent calls need not to include the data to be
sent (can be called with NULL argument).
The select
system call can also be used in combination with the
GnuTLS functions. select
allows monitoring of sockets
and notifies on them being ready for reading or writing data. Note however
that this system call cannot notify on data present in GnuTLS
read buffers, it is only applicable to the kernel sockets API. Thus if
you are using it for reading from a GnuTLS session, make sure
that any cached data are read completely. That can be achieved by checking there
are no data waiting to be read (using gnutls_record_check_pending),
either before the select
system call, or after a call to
gnutls_record_recv. GnuTLS does not keep a write buffer,
thus when writing no additional actions are required.
Although in the TLS protocol implementation each call to receive or send function implies to restoring the same function that was interrupted, in the DTLS protocol this requirement isn’t true. There are cases where a retransmission is required, which are indicated by a received message and thus gnutls_record_get_direction must be called to decide which direction to check prior to restoring a function call.
session: is a gnutls_session_t
structure.
This function provides information about the internals of the
record protocol and is only useful if a prior gnutls function call
(e.g. gnutls_handshake()
) was interrupted for some reason, that
is, if a function returned GNUTLS_E_INTERRUPTED
or
GNUTLS_E_AGAIN
. In such a case, you might want to call select()
or poll()
before calling the interrupted gnutls function again. To
tell you whether a file descriptor should be selected for either
reading or writing, gnutls_record_get_direction()
returns 0 if the
interrupted function was trying to read data, and 1 if it was
trying to write data.
Returns: 0 if trying to read data, 1 if trying to write data.
Moreover, to prevent blocking from DTLS’ retransmission timers to block a
handshake, the gnutls_init function should be called with the
GNUTLS_NONBLOCK
flag set (see Session initialization).
Previous: Asynchronous operation, Up: Setting up the transport layer [Contents][Index]
Because datagram TLS can operate over connections where the peer of a server cannot be reliably verified, functionality is available to prevent denial of service attacks. GnuTLS requires a server to generate a secret key that is used to sign a cookie13. That cookie is sent to the client using gnutls_dtls_cookie_send, and the client must reply using the correct cookie. The server side should verify the initial message sent by client using gnutls_dtls_cookie_verify. If successful the session should be initialized and associated with the cookie using gnutls_dtls_prestate_set, before proceeding to the handshake.
int gnutls_key_generate (gnutls_datum_t * key, unsigned int key_size)
int gnutls_dtls_cookie_send (gnutls_datum_t* key, void* client_data, size_t client_data_size, gnutls_dtls_prestate_st* prestate, gnutls_transport_ptr_t ptr, gnutls_push_func push_func)
int gnutls_dtls_cookie_verify (gnutls_datum_t* key, void* client_data, size_t client_data_size, void* _msg, size_t msg_size, gnutls_dtls_prestate_st* prestate)
void gnutls_dtls_prestate_set (gnutls_session_t session, gnutls_dtls_prestate_st* prestate)
Note that the above apply to server side only and they are not mandatory to be used. Not using them, however, allows denial of service attacks. The client side cookie handling is part of gnutls_handshake.
Datagrams are typically restricted by a maximum transfer unit (MTU). For that both client and server side should set the correct maximum transfer unit for the layer underneath GnuTLS. This will allow proper fragmentation of DTLS messages and prevent messages from being silently discarded by the transport layer. The “correct” maximum transfer unit can be obtained through a path MTU discovery mechanism [RFC4821].
void gnutls_dtls_set_mtu (gnutls_session_t session, unsigned int mtu)
unsigned int gnutls_dtls_get_mtu (gnutls_session_t session)
unsigned int gnutls_dtls_get_data_mtu (gnutls_session_t session)
Next: Data transfer and termination, Previous: Setting up the transport layer, Up: How to use GnuTLS in applications [Contents][Index]
Once a session has been initialized and a network connection has been set up, TLS and DTLS protocols perform a handshake. The handshake is the actual key exchange.
session: is a gnutls_session_t
structure.
This function does the handshake of the TLS/SSL protocol, and initializes the TLS connection.
This function will fail if any problem is encountered, and will return a negative error code. In case of a client, if the client has asked to resume a session, but the server couldn’t, then a full handshake will be performed.
The non-fatal errors such as GNUTLS_E_AGAIN
and
GNUTLS_E_INTERRUPTED
interrupt the handshake procedure, which
should be resumed later. Call this function again, until it
returns 0; cf. gnutls_record_get_direction()
and
gnutls_error_is_fatal()
.
If this function is called by a server after a rehandshake request
then GNUTLS_E_GOT_APPLICATION_DATA
or
GNUTLS_E_WARNING_ALERT_RECEIVED
may be returned. Note that these
are non fatal errors, only in the specific case of a rehandshake.
Their meaning is that the client rejected the rehandshake request or
in the case of GNUTLS_E_GOT_APPLICATION_DATA
it might also mean that
some data were pending.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
The handshake process doesn’t ensure the verification of the peer’s identity. When certificates are in use, this can be done, either after the handshake is complete, or during the handshake if gnutls_certificate_set_verify_function has been used. In both cases the gnutls_certificate_verify_peers2 function can be used to verify the peer’s certificate (see Certificate authentication for more information).
int gnutls_certificate_verify_peers2 (gnutls_session_t session, unsigned int * status)
Next: Handling alerts, Previous: TLS handshake, Up: How to use GnuTLS in applications [Contents][Index]
Once the handshake is complete and peer’s identity
has been verified data can be exchanged. The available
functions resemble the POSIX recv
and send
functions. It is suggested to use gnutls_error_is_fatal
to check whether the error codes returned by these functions are
fatal for the protocol or can be ignored.
session: is a gnutls_session_t
structure.
data: contains the data to send
data_size: is the length of the data
This function has the similar semantics with send()
. The only
difference is that it accepts a GnuTLS session, and uses different
error codes.
Note that if the send buffer is full, send()
will block this
function. See the send()
documentation for full information. You
can replace the default push function by using
gnutls_transport_set_ptr2()
with a call to send()
with a
MSG_DONTWAIT flag if blocking is a problem.
If the EINTR is returned by the internal push function (the
default is send()
) then GNUTLS_E_INTERRUPTED
will be returned. If
GNUTLS_E_INTERRUPTED
or GNUTLS_E_AGAIN
is returned, you must
call this function again, with the same parameters; alternatively
you could provide a NULL
pointer for data, and 0 for
size. cf. gnutls_record_get_direction()
. The errno value EMSGSIZE
maps to GNUTLS_E_LARGE_PACKET
.
Returns: The number of bytes sent, or a negative error code. The
number of bytes sent might be less than data_size
. The maximum
number of bytes this function can send in a single call depends
on the negotiated maximum record size.
session: is a gnutls_session_t
structure.
data: the buffer that the data will be read into
data_size: the number of requested bytes
This function has the similar semantics with recv()
. The only
difference is that it accepts a GnuTLS session, and uses different
error codes.
In the special case that a server requests a renegotiation, the
client may receive an error code of GNUTLS_E_REHANDSHAKE
. This
message may be simply ignored, replied with an alert
GNUTLS_A_NO_RENEGOTIATION
, or replied with a new handshake,
depending on the client’s will.
If EINTR
is returned by the internal push function (the default
is recv()
) then GNUTLS_E_INTERRUPTED
will be returned. If
GNUTLS_E_INTERRUPTED
or GNUTLS_E_AGAIN
is returned, you must
call this function again to get the data. See also
gnutls_record_get_direction()
.
A server may also receive GNUTLS_E_REHANDSHAKE
when a client has
initiated a handshake. In that case the server can only initiate a
handshake or terminate the connection.
Returns: The number of bytes received and zero on EOF (for stream
connections). A negative error code is returned in case of an error.
The number of bytes received might be less than the requested data_size
.
error: is a GnuTLS error code, a negative error code
If a GnuTLS function returns a negative error code you may feed that value to this function to see if the error condition is fatal. Note that you may also want to check the error code manually, since some non-fatal errors to the protocol (such as a warning alert or a rehandshake request) may be fatal for your program.
This function is only useful if you are dealing with errors from the record layer or the handshake layer.
Returns: 1 if the error code is fatal, for positive error
values,
0 is returned. For unknown error
values, -1 is returned.
Although, in the TLS protocol the receive function can be called at any time, when DTLS is used the GnuTLS receive functions must be called once a message is available for reading, even if no data are expected. This is because in DTLS various (internal) actions may be required due to retransmission timers. Moreover, an extended receive function is shown below, which allows the extraction of the message’s sequence number. Due to the unreliable nature of the protocol, this field allows distinguishing out-of-order messages.
session: is a gnutls_session_t
structure.
data: the buffer that the data will be read into
data_size: the number of requested bytes
seq: is the packet’s 64-bit sequence number. Should have space for 8 bytes.
This function is the same as gnutls_record_recv()
, except that
it returns in addition to data, the sequence number of the data.
This is useful in DTLS where record packets might be received
out-of-order. The returned 8-byte sequence number is an
integer in big-endian format and should be
treated as a unique message identification.
Returns: The number of bytes received and zero on EOF. A negative
error code is returned in case of an error. The number of bytes
received might be less than data_size
.
Since: 3.0
The gnutls_record_check_pending helper function is available to
allow checking whether data are available to be read in a GnuTLS session
buffers. Note that this function complements but does not replace select
,
i.e., gnutls_record_check_pending reports no data to be read, select
should be called to check for data in the network buffers.
session: is a gnutls_session_t
structure.
This function checks if there are unread data
in the gnutls buffers. If the return value is
non-zero the next call to gnutls_record_recv()
is guarranteed not to block.
Returns: Returns the size of the data or zero.
int gnutls_record_get_direction (gnutls_session_t session)
Once a TLS or DTLS session is no longer needed, it is recommended to use gnutls_bye to terminate the session. That way the peer is notified securely about the intention of termination, which allows distinguishing it from a malicious connection termination. A session can be deinitialized with the gnutls_deinit function.
session: is a gnutls_session_t
structure.
how: is an integer
Terminates the current TLS/SSL connection. The connection should
have been initiated using gnutls_handshake()
. how
should be one
of GNUTLS_SHUT_RDWR
, GNUTLS_SHUT_WR
.
In case of GNUTLS_SHUT_RDWR
the TLS session gets
terminated and further receives and sends will be disallowed. If
the return value is zero you may continue using the underlying
transport layer. GNUTLS_SHUT_RDWR
sends an alert containing a close
request and waits for the peer to reply with the same message.
In case of GNUTLS_SHUT_WR
the TLS session gets terminated
and further sends will be disallowed. In order to reuse the
connection you should wait for an EOF from the peer.
GNUTLS_SHUT_WR
sends an alert containing a close request.
Note that not all implementations will properly terminate a TLS connection. Some of them, usually for performance reasons, will terminate only the underlying transport layer, and thus not distinguishing between a malicious party prematurely terminating the connection and normal termination.
This function may also return GNUTLS_E_AGAIN
or
GNUTLS_E_INTERRUPTED
; cf. gnutls_record_get_direction()
.
Returns: GNUTLS_E_SUCCESS
on success, or an error code, see
function documentation for entire semantics.
session: is a gnutls_session_t
structure.
This function clears all buffers associated with the session
.
This function will also remove session data from the session
database if the session was terminated abnormally.
Next: Priority Strings, Previous: Data transfer and termination, Up: How to use GnuTLS in applications [Contents][Index]
During a TLS connection alert messages may be exchanged by the
two peers. Those messages may be fatal, meaning the connection
must be terminated afterwards, or warning when something needs
to be reported to the peer, but without interrupting the session.
The error codes GNUTLS_E_WARNING_ALERT_RECEIVED
or GNUTLS_E_FATAL_ALERT_RECEIVED
signal those alerts
when received, and may be returned by all GnuTLS functions that receive
data from the peer, being gnutls_handshake and gnutls_record_recv.
If those error codes are received the alert and its level should be logged or reported to the peer using the functions below.
session: is a gnutls_session_t
structure.
This function will return the last alert number received. This
function should be called when GNUTLS_E_WARNING_ALERT_RECEIVED
or
GNUTLS_E_FATAL_ALERT_RECEIVED
errors are returned by a gnutls
function. The peer may send alerts if he encounters an error.
If no alert has been received the returned value is undefined.
Returns: the last alert received, a
gnutls_alert_description_t
value.
alert: is an alert number.
This function will return a string that describes the given alert
number, or NULL
. See gnutls_alert_get()
.
Returns: string corresponding to gnutls_alert_description_t
value.
The peer may also be warned or notified of a fatal issue by using one of the functions below. All the available alerts are listed in The Alert Protocol.
session: is a gnutls_session_t
structure.
level: is the level of the alert
desc: is the alert description
This function will send an alert to the peer in order to inform him of something important (eg. his Certificate could not be verified). If the alert level is Fatal then the peer is expected to close the connection, otherwise he may ignore the alert and continue.
The error code of the underlying record send function will be
returned, so you may also receive GNUTLS_E_INTERRUPTED
or
GNUTLS_E_AGAIN
as well.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
err: is a negative integer
level: the alert level will be stored there
Get an alert depending on the error code returned by a gnutls
function. All alerts sent by this function should be considered
fatal. The only exception is when err
is GNUTLS_E_REHANDSHAKE
,
where a warning alert should be sent to the peer indicating that no
renegotiation will be performed.
If there is no mapping to a valid alert the alert to indicate internal error is returned.
Returns: the alert code to use for a particular error code.
Next: Advanced and other topics, Previous: Handling alerts, Up: How to use GnuTLS in applications [Contents][Index]
In order to specify cipher suite preferences on a TLS session there are priority functions that accept a string specifying the enabled for the handshake algorithms. That string may contain a single initial keyword such as in Table 7.2 and may be followed by additional algorithm or special keywords.
int gnutls_priority_set_direct (gnutls_session_t session, const char * priorities, const char ** err_pos)
int gnutls_priority_set (gnutls_session_t session, gnutls_priority_t priority)
Keyword | Description |
---|---|
PERFORMANCE | All the known to be secure ciphersuites are enabled, limited to 128 bit ciphers and sorted by terms of speed performance. The message authenticity security level is of 64 bits or more. |
NORMAL | Means all the known to be secure ciphersuites. The ciphers are sorted by security margin, although the 256-bit ciphers are included as a fallback only. The message authenticity security level is of 64 bits or more. |
SECURE128 | Means all known to be secure ciphersuites that offer a security level 128-bit or more and a message authenticity security level of 80 bits or more. |
SECURE192 | Means all the known to be secure ciphersuites that offer a security level 192-bit or more and a message authenticity security level of 128 bits or more. |
SECURE256 | Currently alias for SECURE192. |
SUITEB128 | Means all the NSA Suite B cryptography (RFC5430) ciphersuites with an 128 bit security level. |
SUITEB192 | Means all the NSA Suite B cryptography (RFC5430) ciphersuites with an 192 bit security level. |
EXPORT | Means all ciphersuites are enabled, including the low-security 40 bit ciphers. |
NONE | Means nothing is enabled. This disables even protocols and compression methods. It should be followed by the algorithms to be enabled. |
Table 7.2: Supported initial keywords.
Unless the initial keyword is "NONE" the defaults (in preference order) are for TLS protocols TLS 1.2, TLS1.1, TLS1.0, SSL3.0; for compression NULL; for certificate types X.509. In key exchange algorithms when in NORMAL or SECURE levels the perfect forward secrecy algorithms take precedence of the other protocols. In all cases all the supported key exchange algorithms are enabled14.
Note that the SECURE levels distinguish between overall security level and message authenticity security level. That is because the message authenticity security level requires the adversary to break the algorithms at real-time during the protocol run, whilst the overall security level refers to off-line adversaries (e.g. adversaries breaking the ciphertext years after it was captured).
The NONE keyword, if used, must followed by keywords specifying the algorithms and protocols to be enabled. The other initial keywords may be followed by such keywords. The order with which every algorithm or protocol is specified is significant. Algorithms specified before others will take precedence. The supported algorithms and protocols are shown in Table 7.3. To avoid collisions in order to specify a compression algorithm in the priority string you have to prefix it with "COMP-", protocol versions with "VERS-", signature algorithms with "SIGN-" and certificate types with "CTYPE-". All other algorithms don’t need a prefix. Each specified keyword can be prefixed with any of the following characters.
appended with an algorithm will remove this algorithm.
appended with an algorithm will add this algorithm.
Type | Keywords |
---|---|
Ciphers | AES-128-CBC, AES-256-CBC, AES-128-GCM, CAMELLIA-128-CBC, CAMELLIA-256-CBC, ARCFOUR-128, 3DES-CBC ARCFOUR-40. Catch all name is CIPHER-ALL which will add all the algorithms from NORMAL priority. |
Key exchange | RSA, DHE-RSA, DHE-DSS, SRP, SRP-RSA, SRP-DSS, PSK, DHE-PSK, ECDHE-RSA, ANON-ECDH, ANON-DH, RSA-EXPORT. The Catch all name is KX-ALL which will add all the algorithms from NORMAL priority. |
MAC | MD5, SHA1, SHA256, AEAD (used with GCM ciphers only). All algorithms from NORMAL priority can be accessed with MAC-ALL. |
Compression algorithms | COMP-NULL, COMP-DEFLATE. Catch all is COMP-ALL. |
TLS versions | VERS-SSL3.0, VERS-TLS1.0, VERS-TLS1.1, VERS-TLS1.2, VERS-DTLS1.0. Catch all is VERS-TLS-ALL and VERS-DTLS-ALL. |
Signature algorithms | SIGN-RSA-SHA1, SIGN-RSA-SHA224, SIGN-RSA-SHA256, SIGN-RSA-SHA384, SIGN-RSA-SHA512, SIGN-DSA-SHA1, SIGN-DSA-SHA224, SIGN-DSA-SHA256, SIGN-RSA-MD5. Catch all is SIGN-ALL. This is only valid for TLS 1.2 and later. |
Elliptic curves | CURVE-SECP192R1, CURVE-SECP224R1, CURVE-SECP256R1, CURVE-SECP384R1, CURVE-SECP521R1. Catch all is CURVE-ALL. |
Table 7.3: The supported algorithm keywords in priority strings.
Note that the DHE key exchange methods are generally slower15 than their elliptic curves counterpart (ECDHE). Moreover the plain Diffie-Hellman key exchange requires parameters to be generated and associated with a credentials structure by the server (see Parameter generation).
The available special keywords are shown in Table 7.4.
Keyword | Description |
---|---|
%COMPAT | will enable compatibility mode. It might mean that violations of the protocols are allowed as long as maximum compatibility with problematic clients and servers is achieved. More specifically this string would disable TLS record random padding and tolerate packets over the maximum allowed TLS record. |
%NO_EXTENSIONS | will prevent the sending of any TLS extensions in client side. Note that TLS 1.2 requires extensions to be used, as well as safe renegotiation thus this option must be used with care. |
%STATELESS_COMPRESSION | will disable keeping state across records when compressing. This may help to mitigate attacks when compression is used but an attacker is in control of input data. |
%SERVER_PRECEDENCE | The ciphersuite will be selected according to server priorities and not the client’s. |
%DISABLE_SAFE_RENEGOTIATION | will disable safe renegotiation completely. Do not use unless you know what you are doing. Testing purposes only. |
%UNSAFE_RENEGOTIATION | will allow handshakes and re-handshakes without the safe renegotiation extension. Note that for clients this mode is insecure (you may be under attack), and for servers it will allow insecure clients to connect (which could be fooled by an attacker). Do not use unless you know what you are doing and want maximum compatibility. |
%PARTIAL_RENEGOTIATION | will allow initial handshakes to proceed, but not re-handshakes. This leaves the client vulnerable to attack, and servers will be compatible with non-upgraded clients for initial handshakes. This is currently the default for clients and servers, for compatibility reasons. |
%SAFE_RENEGOTIATION | will enforce safe renegotiation. Clients and servers will refuse to talk to an insecure peer. Currently this causes interoperability problems, but is required for full protection. |
%SSL3_RECORD_VERSION | will use SSL3.0 record version in client hello. This is the default. |
%LATEST_RECORD_VERSION | will use the latest TLS version record version in client hello. |
%VERIFY_ALLOW_SIGN_RSA_MD5 | will allow RSA-MD5 signatures in certificate chains. |
%VERIFY_ALLOW_X509_V1_CA_CRT | will allow V1 CAs in chains. |
Table 7.4: Special priority string keywords.
Finally the ciphersuites enabled by any priority string can be
listed using the gnutls-cli
application (see gnutls-cli Invocation),
or by using the priority functions as in Listing the ciphersuites in a priority string.
Example priority strings are:
The default priority without the HMAC-MD5: "NORMAL:-MD5" Specifying RSA with AES-128-CBC: "NONE:+VERS-TLS-ALL:+MAC-ALL:+RSA:+AES-128-CBC:+SIGN-ALL:+COMP-NULL" Specifying the defaults except ARCFOUR-128: "NORMAL:-ARCFOUR-128" Enabling the 128-bit secure ciphers, while disabling SSL 3.0 and enabling compression: "SECURE128:-VERS-SSL3.0:+COMP-DEFLATE"
Next: Using the cryptographic library, Previous: Priority Strings, Up: How to use GnuTLS in applications [Contents][Index]
• Session resumption: | ||
• Parameter generation: | ||
• Keying Material Exporters: | ||
• Channel Bindings: | ||
• Interoperability: | ||
• Compatibility with the OpenSSL library: |
Next: Parameter generation, Up: Advanced and other topics [Contents][Index]
To reduce time and roundtrips spent in a handshake the client can request session resumption from a server that previously shared a session with. For that the client has to retrieve and store the session parameters. Before establishing a new session to the same server the parameters must be re-associated with the GnuTLS session using gnutls_session_set_data.
int gnutls_session_get_data (gnutls_session_t session, void * session_data, size_t * session_data_size)
int gnutls_session_get_id (gnutls_session_t session, void * session_id, size_t * session_id_size)
int gnutls_session_set_data (gnutls_session_t session, const void * session_data, size_t session_data_size)
Keep in mind that sessions will be expired after some time, depending on the server, and a server may choose not to resume a session even when requested to. The expiration is to prevent temporal session keys from becoming long-term keys. Also note that as a client you must enable, using the priority functions, at least the algorithms used in the last session.
It is highly recommended for clients to enable the session ticket extension using gnutls_session_ticket_enable_client in order to allow resumption with servers that do not store any state.
int gnutls_session_ticket_enable_client (gnutls_session_t session)
session: is a gnutls_session_t
structure.
Check whether session is resumed or not.
Returns: non zero if this session is resumed, or a zero if this is a new session.
In order to support resumption a server can store the session security parameters in a local database or by using session tickets (see Session tickets) to delegate storage to the client. Because session tickets might not be supported by all clients, servers could combine the two methods.
A storing server needs to specify callback functions to store, retrieve and delete session data. These can be registered with the functions below. The stored sessions in the database can be checked using gnutls_db_check_entry for expiration.
void gnutls_db_set_retrieve_function (gnutls_session_t session, gnutls_db_retr_func retr_func)
void gnutls_db_set_store_function (gnutls_session_t session, gnutls_db_store_func store_func)
void gnutls_db_set_ptr (gnutls_session_t session, void * ptr)
void gnutls_db_set_remove_function (gnutls_session_t session, gnutls_db_remove_func rem_func)
int gnutls_db_check_entry (gnutls_session_t session, gnutls_datum_t session_entry)
A server utilizing tickets should generate ticket encryption and authentication keys using gnutls_session_ticket_key_generate. Those keys should be associated with the GnuTLS session using gnutls_session_ticket_enable_server.
session: is a gnutls_session_t
structure.
key: key to encrypt session parameters.
Request that the server should attempt session resumption using
SessionTicket. key
must be initialized with
gnutls_session_ticket_key_generate()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
Since: 2.10.0
key: is a pointer to a gnutls_datum_t
which will contain a newly
created key.
Generate a random key to encrypt security parameters within SessionTicket.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
Since: 2.10.0
session: is a gnutls_session_t
structure.
Check whether the client has asked for session resumption. This function is valid only on server side.
Returns: non zero if session resumption was asked, or a zero if not.
A server enabling both session tickets and a storage for session data would use session tickets when clients support it and the storage otherwise.
Next: Keying Material Exporters, Previous: Session resumption, Up: Advanced and other topics [Contents][Index]
Several TLS ciphersuites require additional parameters that need to be generated or provided by the application. The Diffie-Hellman based ciphersuites (ANON-DH or DHE), require the group parameters to be provided. Those can either be be generated on the fly using gnutls_dh_params_generate2 or imported from pregenerated data using gnutls_dh_params_import_pkcs3. The parameters can be used in a TLS session by calling gnutls_certificate_set_dh_params or gnutls_anon_set_server_dh_params for anonymous sessions.
int gnutls_dh_params_generate2 (gnutls_dh_params_t params, unsigned int bits)
int gnutls_dh_params_import_pkcs3 (gnutls_dh_params_t params, const gnutls_datum_t * pkcs3_params, gnutls_x509_crt_fmt_t format)
void gnutls_certificate_set_dh_params (gnutls_certificate_credentials_t res, gnutls_dh_params_t dh_params)
void gnutls_anon_set_server_dh_params (gnutls_anon_server_credentials_t res, gnutls_dh_params_t dh_params)
Due to the time-consuming calculations required for the generation
of Diffie-Hellman parameters we suggest against performing generation
of them within an application. The certtool
tool can be used to
generate or export known safe values that can be stored in code
or in a configuration file to provide the ability to replace. We also
recommend the usage of gnutls_sec_param_to_pk_bits
(see Selecting cryptographic key sizes) to determine
the bit size of the generated parameters.
Note that the information stored in the generated PKCS #3 structure
changed with GnuTLS 3.0.9. Since that version the privateValueLength
member of the structure is set, allowing the server utilizing the
parameters to use keys of the size of the security parameter. This
provides better performance in key exchange.
The ciphersuites that involve the RSA-EXPORT key exchange require additional parameters. Those ciphersuites are rarely used today because they are by design insecure, thus if you have no requirement for them, the rest of this section can be skipped. The RSA-EXPORT key exchange requires 512-bit RSA keys to be generated. It is recommended those parameters to be refreshed (regenerated) in short intervals. The following functions can be used for these parameters.
int gnutls_rsa_params_generate2 (gnutls_rsa_params_t params, unsigned int bits)
void gnutls_certificate_set_rsa_export_params (gnutls_certificate_credentials_t res, gnutls_rsa_params_t rsa_params)
int gnutls_rsa_params_import_pkcs1 (gnutls_rsa_params_t params, const gnutls_datum_t * pkcs1_params, gnutls_x509_crt_fmt_t format)
int gnutls_rsa_params_export_pkcs1 (gnutls_rsa_params_t params, gnutls_x509_crt_fmt_t format, unsigned char * params_data, size_t * params_data_size)
To allow renewal of the parameters within an application without accessing the credentials, which are a shared structure, an alternative interface is available using a callback function.
res: is a gnutls_certificate_credentials_t structure
func: is the function to be called
This function will set a callback in order for the server to get
the Diffie-Hellman or RSA parameters for certificate
authentication. The callback should return GNUTLS_E_SUCCESS
(0) on success.
Next: Channel Bindings, Previous: Parameter generation, Up: Advanced and other topics [Contents][Index]
The TLS PRF can be used by other protocols to derive keys based on
the TLS master secret. The API to use is gnutls_prf. The
function needs to be provided with the label in the parameter
label
, and the extra data to mix in the
extra
parameter. Depending on whether you want to mix in the
client or server random data first, you can set the
server_random_first
parameter.
For example, after establishing a TLS session using gnutls_handshake, you can invoke the TLS PRF with this call:
#define MYLABEL "EXPORTER-FOO" #define MYCONTEXT "some context data" char out[32]; rc = gnutls_prf (session, strlen (MYLABEL), MYLABEL, 0, strlen (MYCONTEXT), MYCONTEXT, 32, out);
If you don’t want to mix in the client/server random, there is a low-level TLS PRF interface called gnutls_prf_raw.
Next: Interoperability, Previous: Keying Material Exporters, Up: Advanced and other topics [Contents][Index]
In user authentication protocols (e.g., EAP or SASL mechanisms) it is useful to have a unique string that identifies the secure channel that is used, to bind together the user authentication with the secure channel. This can protect against man-in-the-middle attacks in some situations. That unique string is called a “channel binding”. For background and discussion see [RFC5056].
In GnuTLS you can extract a channel binding using the
gnutls_session_channel_binding function. Currently only the
type GNUTLS_CB_TLS_UNIQUE
is supported, which corresponds to
the tls-unique
channel binding for TLS defined in
[RFC5929].
The following example describes how to print the channel binding data. Note that it must be run after a successful TLS handshake.
{ gnutls_datum_t cb; int rc; rc = gnutls_session_channel_binding (session, GNUTLS_CB_TLS_UNIQUE, &cb); if (rc) fprintf (stderr, "Channel binding error: %s\n", gnutls_strerror (rc)); else { size_t i; printf ("- Channel binding 'tls-unique': "); for (i = 0; i < cb.size; i++) printf ("%02x", cb.data[i]); printf ("\n"); } }
Next: Compatibility with the OpenSSL library, Previous: Channel Bindings, Up: Advanced and other topics [Contents][Index]
The TLS protocols support many ciphersuites, extensions and version numbers. As a result, few implementations are not able to properly interoperate once faced with extensions or version protocols they do not support and understand. The TLS protocol allows for a graceful downgrade to the commonly supported options, but practice shows it is not always implemented correctly.
Because there is no way to achieve maximum interoperability with broken peers without sacrificing security, GnuTLS ignores such peers by default. This might not be acceptable in cases where maximum compatibility is required. Thus we allow enabling compatibility with broken peers using priority strings (see Priority Strings). A conservative priority string that would disable certain TLS protocol options that are known to cause compatibility problems, is shown below.
NORMAL:%COMPAT
For broken peers that do not tolerate TLS version numbers over TLS 1.0 another priority string is:
NORMAL:-VERS-TLS-ALL:+VERS-TLS1.0:+VERS-SSL3.0:%COMPAT
This priority string will in addition to above, only enable SSL 3.0 and TLS 1.0 as protocols. Note however that there are known attacks against those protocol versions, especially over the CBC-mode ciphersuites. To mitigate them another priority string that only allows the stream cipher ARCFOUR is below.
NORMAL:-VERS-TLS-ALL:+VERS-TLS1.0:+VERS-SSL3.0:-CIPHER-ALL:+ARCFOUR-128:%COMPAT
Previous: Interoperability, Up: Advanced and other topics [Contents][Index]
To ease GnuTLS’ integration with existing applications, a
compatibility layer with the OpenSSL library is included
in the gnutls-openssl
library. This compatibility layer is not
complete and it is not intended to completely re-implement the OpenSSL
API with GnuTLS. It only provides limited source-level
compatibility.
The prototypes for the compatibility functions are in the gnutls/openssl.h header file. The limitations imposed by the compatibility layer include:
Next: Selecting cryptographic key sizes, Previous: Advanced and other topics, Up: How to use GnuTLS in applications [Contents][Index]
GnuTLS is not a low-level cryptographic library, i.e., it does not provide access to basic cryptographic primitives. However it abstracts the internal cryptographic back-end (see Cryptographic Backend), providing symmetric crypto, hash and HMAC algorithms, as well access to the random number generation.
• Symmetric cryptography: | ||
• Hash and HMAC functions: | ||
• Random number generation: |
Next: Hash and HMAC functions, Up: Using the cryptographic library [Contents][Index]
The available functions to access symmetric crypto algorithms operations are shown below. The supported algorithms are the algorithms required by the TLS protocol. They are listed in Table 3.1.
int gnutls_cipher_init (gnutls_cipher_hd_t * handle, gnutls_cipher_algorithm_t cipher, const gnutls_datum_t * key, const gnutls_datum_t * iv)
int gnutls_cipher_encrypt2 (gnutls_cipher_hd_t handle, const void * text, size_t textlen, void * ciphertext, size_t ciphertextlen)
int gnutls_cipher_decrypt2 (gnutls_cipher_hd_t handle, const void * ciphertext, size_t ciphertextlen, void * text, size_t textlen)
void gnutls_cipher_set_iv (gnutls_cipher_hd_t handle, void * iv, size_t ivlen)
void gnutls_cipher_deinit (gnutls_cipher_hd_t handle)
In order to support authenticated encryption with associated data (AEAD) algorithms the following functions are provided to set the associated data and retrieve the authentication tag.
int gnutls_cipher_add_auth (gnutls_cipher_hd_t handle, const void * text, size_t text_size)
int gnutls_cipher_tag (gnutls_cipher_hd_t handle, void * tag, size_t tag_size)
Next: Random number generation, Previous: Symmetric cryptography, Up: Using the cryptographic library [Contents][Index]
The available operations to access hash functions and hash-MAC (HMAC) algorithms are shown below. HMAC algorithms provided keyed hash functionality. They supported HMAC algorithms are listed in Table 3.2.
int gnutls_hmac_init (gnutls_hmac_hd_t * dig, gnutls_mac_algorithm_t algorithm, const void * key, size_t keylen)
int gnutls_hmac (gnutls_hmac_hd_t handle, const void * text, size_t textlen)
void gnutls_hmac_output (gnutls_hmac_hd_t handle, void * digest)
void gnutls_hmac_deinit (gnutls_hmac_hd_t handle, void * digest)
int gnutls_hmac_get_len (gnutls_mac_algorithm_t algorithm)
int gnutls_hmac_fast (gnutls_mac_algorithm_t algorithm, const void * key, size_t keylen, const void * text, size_t textlen, void * digest)
The available functions to access hash functions are shown below. The supported hash functions are the same as the HMAC algorithms.
int gnutls_hash_init (gnutls_hash_hd_t * dig, gnutls_digest_algorithm_t algorithm)
int gnutls_hash (gnutls_hash_hd_t handle, const void * text, size_t textlen)
void gnutls_hash_output (gnutls_hash_hd_t handle, void * digest)
void gnutls_hash_deinit (gnutls_hash_hd_t handle, void * digest)
int gnutls_hash_get_len (gnutls_digest_algorithm_t algorithm)
int gnutls_hash_fast (gnutls_digest_algorithm_t algorithm, const void * text, size_t textlen, void * digest)
Previous: Hash and HMAC functions, Up: Using the cryptographic library [Contents][Index]
Access to the random number generator is provided using the gnutls_rnd function. It allows obtaining random data of various levels.
GNUTLS_RND_NONCE
Non-predictable random number. Fatal in parts of session if broken, i.e., vulnerable to statistical analysis.
GNUTLS_RND_RANDOM
Pseudo-random cryptographic random number. Fatal in session if broken.
GNUTLS_RND_KEY
Fatal in many sessions if broken.
Figure 7.2: The random number levels.
level: a security level
data: place to store random bytes
len: The requested size
This function will generate random data and store it to output buffer.
Returns: Zero or a negative error code on error.
Since: 2.12.0
Previous: Using the cryptographic library, Up: How to use GnuTLS in applications [Contents][Index]
Because many algorithms are involved in TLS, it is not easy to set a consistent security level. For this reason in Table 7.5 we present some correspondence between key sizes of symmetric algorithms and public key algorithms based on [ECRYPT]. Those can be used to generate certificates with appropriate key sizes as well as select parameters for Diffie-Hellman and SRP authentication.
Security bits | RSA, DH and SRP parameter size | ECC key size | Security parameter | Description |
---|---|---|---|---|
80 | 1248 | 160 | LOW | Very short term protection against agencies |
96 | 1776 | 192 | LEGACY | Legacy standard level |
112 | 2432 | 224 | NORMAL | Medium-term protection |
128 | 3248 | 256 | HIGH | Long term protection |
256 | 15424 | 512 | ULTRA | Foreseeable future |
Table 7.5: Key sizes and security parameters.
The first column provides a security parameter in a number of bits. This
gives an indication of the number of combinations to be tried by an adversary
to brute force a key. For example to test all possible keys in a 112 bit security parameter
2^{112} combinations have to be tried. For today’s technology this is infeasible.
The next two columns correlate the security
parameter with actual bit sizes of parameters for DH, RSA, SRP and ECC algorithms.
A mapping to gnutls_sec_param_t
value is given for each security parameter, on
the next column, and finally a brief description of the level.
Note, however, that the values suggested here are nothing more than an educated guess that is valid today. There are no guarantees that an algorithm will remain unbreakable or that these values will remain constant in time. There could be scientific breakthroughs that cannot be predicted or total failure of the current public key systems by quantum computers. On the other hand though the cryptosystems used in TLS are selected in a conservative way and such catastrophic breakthroughs or failures are believed to be unlikely. The NIST publication SP 800-57 [NISTSP80057] contains a similar table.
When using GnuTLS and a decision on bit sizes for a public key algorithm is required, use of the following functions is recommended:
algo: is a public key algorithm
param: is a security parameter
When generating private and public key pairs a difficult question is which size of "bits" the modulus will be in RSA and the group size in DSA. The easy answer is 1024, which is also wrong. This function will convert a human understandable security parameter to an appropriate size for the specific algorithm.
Returns: The number of bits, or (0).
Since: 2.12.0
algo: is a public key algorithm
bits: is the number of bits
This is the inverse of gnutls_sec_param_to_pk_bits()
. Given an algorithm
and the number of bits, it will return the security parameter. This is
a rough indication.
Returns: The security parameter.
Since: 2.12.0
Those functions will convert a human understandable security parameter
of gnutls_sec_param_t
type, to a number of bits suitable for a public
key algorithm.
The following functions will set the minimum acceptable group size for Diffie-Hellman and SRP authentication.
void gnutls_dh_set_prime_bits (gnutls_session_t session, unsigned int bits)
void gnutls_srp_set_prime_bits (gnutls_session_t session, unsigned int bits)
Next: Other included programs, Previous: How to use GnuTLS in applications, Up: Top [Contents][Index]
In this chapter several examples of real-world use cases are listed. The examples are simplified to promote readability and contain little or no error checking.
• Client examples: | ||
• Server examples: | ||
• OCSP example: | ||
• Miscellaneous examples: |
Next: Server examples, Up: GnuTLS application examples [Contents][Index]
This section contains examples of TLS and SSL clients, using GnuTLS. Note that some of the examples require functions implemented by another example.
Next: Simple client example with SSH-style certificate verification, Up: Client examples [Contents][Index]
Let’s assume now that we want to create a TCP client which communicates with servers that use X.509 or OpenPGP certificate authentication. The following client is a very simple TLS client, which uses the high level verification functions for certificates, but does not support session resumption.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <gnutls/gnutls.h> #include <gnutls/x509.h> #include "examples.h" /* A very basic TLS client, with X.509 authentication and server certificate * verification. Note that error checking for missing files etc. is missing * for simplicity. */ #define MAX_BUF 1024 #define CAFILE "/etc/ssl/certs/ca-certificates.crt" #define MSG "GET / HTTP/1.0\r\n\r\n" extern int tcp_connect (void); extern void tcp_close (int sd); static int _verify_certificate_callback (gnutls_session_t session); int main (void) { int ret, sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; const char *err; gnutls_certificate_credentials_t xcred; gnutls_global_init (); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); /* sets the trusted cas file */ /* gnutls_certificate_set_x509_system_trust(xcred); */ gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_verify_function (xcred, _verify_certificate_callback); /* If client holds a certificate it can be set using the following: * gnutls_certificate_set_x509_key_file (xcred, "cert.pem", "key.pem", GNUTLS_X509_FMT_PEM); */ /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); gnutls_session_set_ptr (session, (void *) "my_host_name"); gnutls_server_name_set (session, GNUTLS_NAME_DNS, "my_host_name", strlen("my_host_name")); /* Use default priorities */ ret = gnutls_priority_set_direct (session, "NORMAL", &err); if (ret < 0) { if (ret == GNUTLS_E_INVALID_REQUEST) { fprintf (stderr, "Syntax error at: %s\n", err); } exit (1); } /* put the x509 credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); /* connect to the peer */ sd = tcp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ do { ret = gnutls_handshake (session); } while (ret < 0 && gnutls_error_is_fatal (ret) == 0); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_certificate_free_credentials (xcred); gnutls_global_deinit (); return 0; } /* This function will verify the peer's certificate, and check * if the hostname matches, as well as the activation, expiration dates. */ static int _verify_certificate_callback (gnutls_session_t session) { unsigned int status; const gnutls_datum_t *cert_list; unsigned int cert_list_size; int ret; gnutls_x509_crt_t cert; const char *hostname; /* read hostname */ hostname = gnutls_session_get_ptr (session); /* This verification function uses the trusted CAs in the credentials * structure. So you must have installed one or more CA certificates. */ ret = gnutls_certificate_verify_peers2 (session, &status); if (ret < 0) { printf ("Error\n"); return GNUTLS_E_CERTIFICATE_ERROR; } if (status & GNUTLS_CERT_SIGNER_NOT_FOUND) printf ("The certificate hasn't got a known issuer.\n"); if (status & GNUTLS_CERT_REVOKED) printf ("The certificate has been revoked.\n"); if (status & GNUTLS_CERT_EXPIRED) printf ("The certificate has expired\n"); if (status & GNUTLS_CERT_NOT_ACTIVATED) printf ("The certificate is not yet activated\n"); if (status & GNUTLS_CERT_INVALID) { printf ("The certificate is not trusted.\n"); return GNUTLS_E_CERTIFICATE_ERROR; } /* Up to here the process is the same for X.509 certificates and * OpenPGP keys. From now on X.509 certificates are assumed. This can * be easily extended to work with openpgp keys as well. */ if (gnutls_certificate_type_get (session) != GNUTLS_CRT_X509) return GNUTLS_E_CERTIFICATE_ERROR; if (gnutls_x509_crt_init (&cert) < 0) { printf ("error in initialization\n"); return GNUTLS_E_CERTIFICATE_ERROR; } cert_list = gnutls_certificate_get_peers (session, &cert_list_size); if (cert_list == NULL) { printf ("No certificate was found!\n"); return GNUTLS_E_CERTIFICATE_ERROR; } if (gnutls_x509_crt_import (cert, &cert_list[0], GNUTLS_X509_FMT_DER) < 0) { printf ("error parsing certificate\n"); return GNUTLS_E_CERTIFICATE_ERROR; } if (!gnutls_x509_crt_check_hostname (cert, hostname)) { printf ("The certificate's owner does not match hostname '%s'\n", hostname); return GNUTLS_E_CERTIFICATE_ERROR; } gnutls_x509_crt_deinit (cert); /* notify gnutls to continue handshake normally */ return 0; }
Next: Simple client example with anonymous authentication, Previous: Simple client example with X.509 certificate support, Up: Client examples [Contents][Index]
This is an alternative verification function that will use the X.509 certificate authorities for verification, but also assume an trust on first use (SSH-like) authentication system. That is the user is prompted on unknown public keys and known public keys are considered trusted.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <gnutls/gnutls.h> #include <gnutls/x509.h> #include "examples.h" /* This function will verify the peer's certificate, check * if the hostname matches. In addition it will perform an * SSH-style authentication, where ultimately trusted keys * are only the keys that have been seen before. */ int _ssh_verify_certificate_callback (gnutls_session_t session) { unsigned int status; const gnutls_datum_t *cert_list; unsigned int cert_list_size; int ret; gnutls_x509_crt_t cert; const char *hostname; /* read hostname */ hostname = gnutls_session_get_ptr (session); /* This verification function uses the trusted CAs in the credentials * structure. So you must have installed one or more CA certificates. */ ret = gnutls_certificate_verify_peers2 (session, &status); if (ret < 0) { printf ("Error\n"); return GNUTLS_E_CERTIFICATE_ERROR; } if (status & GNUTLS_CERT_INVALID) printf ("The certificate is not trusted.\n"); if (status & GNUTLS_CERT_SIGNER_NOT_FOUND) printf ("The certificate hasn't got a known issuer.\n"); if (status & GNUTLS_CERT_REVOKED) printf ("The certificate has been revoked.\n"); if (status & GNUTLS_CERT_EXPIRED) printf ("The certificate has expired\n"); if (status & GNUTLS_CERT_NOT_ACTIVATED) printf ("The certificate is not yet activated\n"); /* Up to here the process is the same for X.509 certificates and * OpenPGP keys. From now on X.509 certificates are assumed. This can * be easily extended to work with openpgp keys as well. */ if (gnutls_certificate_type_get (session) != GNUTLS_CRT_X509) return GNUTLS_E_CERTIFICATE_ERROR; if (gnutls_x509_crt_init (&cert) < 0) { printf ("error in initialization\n"); return GNUTLS_E_CERTIFICATE_ERROR; } cert_list = gnutls_certificate_get_peers (session, &cert_list_size); if (cert_list == NULL) { printf ("No certificate was found!\n"); return GNUTLS_E_CERTIFICATE_ERROR; } /* This is not a real world example, since we only check the first * certificate in the given chain. */ if (gnutls_x509_crt_import (cert, &cert_list[0], GNUTLS_X509_FMT_DER) < 0) { printf ("error parsing certificate\n"); return GNUTLS_E_CERTIFICATE_ERROR; } if (!gnutls_x509_crt_check_hostname (cert, hostname)) { printf ("The certificate's owner does not match hostname '%s'\n", hostname); status |= GNUTLS_CERT_INVALID; } gnutls_x509_crt_deinit (cert); /* service may be obtained alternatively using getservbyport() */ ret = gnutls_verify_stored_pubkey(NULL, NULL, hostname, "https", GNUTLS_CRT_X509, &cert_list[0], 0); if (ret == GNUTLS_E_NO_CERTIFICATE_FOUND) { printf("Host %s is not known.", hostname); if (status == 0) printf("Its certificate is valid for %s.\n", hostname); /* the certificate must be printed and user must be asked on * whether it is trustworthy. --see gnutls_x509_crt_print() */ /* if not trusted */ return GNUTLS_E_CERTIFICATE_ERROR; } else if (ret == GNUTLS_E_CERTIFICATE_KEY_MISMATCH) { printf("Warning: host %s is known but has another key associated.", hostname); printf("It might be that the server has multiple keys, or you are under attack\n"); if (status == 0) printf("Its certificate is valid for %s.\n", hostname); /* the certificate must be printed and user must be asked on * whether it is trustworthy. --see gnutls_x509_crt_print() */ /* if not trusted */ return GNUTLS_E_CERTIFICATE_ERROR; } else if (ret < 0) { printf("gnutls_verify_stored_pubkey: %s\n", gnutls_strerror(ret)); return ret; } /* user trusts the key -> store it */ if (ret != 0) { ret = gnutls_store_pubkey(NULL, NULL, hostname, "https", GNUTLS_CRT_X509, &cert_list[0], 0, 0); if (ret < 0) printf("gnutls_store_pubkey: %s\n", gnutls_strerror(ret)); } /* notify gnutls to continue handshake normally */ return 0; }
Next: Simple Datagram TLS client example, Previous: Simple client example with SSH-style certificate verification, Up: Client examples [Contents][Index]
The simplest client using TLS is the one that doesn’t do any authentication. This means no external certificates or passwords are needed to set up the connection. As could be expected, the connection is vulnerable to man-in-the-middle (active or redirection) attacks. However, the data are integrity protected and encrypted from passive eavesdroppers.
Note that due to the vulnerable nature of this method very few public servers support it.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <unistd.h> #include <gnutls/gnutls.h> /* A very basic TLS client, with anonymous authentication. */ #define MAX_BUF 1024 #define MSG "GET / HTTP/1.0\r\n\r\n" extern int tcp_connect (void); extern void tcp_close (int sd); int main (void) { int ret, sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; gnutls_anon_client_credentials_t anoncred; /* Need to enable anonymous KX specifically. */ gnutls_global_init (); gnutls_anon_allocate_client_credentials (&anoncred); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); /* Use default priorities */ gnutls_priority_set_direct (session, "PERFORMANCE:+ANON-ECDH:+ANON-DH", NULL); /* put the anonymous credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_ANON, anoncred); /* connect to the peer */ sd = tcp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ do { ret = gnutls_handshake (session); } while (ret < 0 && gnutls_error_is_fatal (ret) == 0); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_anon_free_client_credentials (anoncred); gnutls_global_deinit (); return 0; }
Next: Obtaining session information, Previous: Simple client example with anonymous authentication, Up: Client examples [Contents][Index]
This is a client that uses UDP to connect to a server. This is the DTLS equivalent to the TLS example with X.509 certificates.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <unistd.h> #include <gnutls/gnutls.h> #include <gnutls/dtls.h> /* A very basic Datagram TLS client, over UDP with X.509 authentication. */ #define MAX_BUF 1024 #define CAFILE "/etc/ssl/certs/ca-certificates.crt" #define MSG "GET / HTTP/1.0\r\n\r\n" extern int udp_connect (void); extern void udp_close (int sd); extern int verify_certificate_callback (gnutls_session_t session); int main (void) { int ret, sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; const char *err; gnutls_certificate_credentials_t xcred; gnutls_global_init (); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); /* sets the trusted cas file */ gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_verify_function (xcred, verify_certificate_callback); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT | GNUTLS_DATAGRAM); /* Use default priorities */ ret = gnutls_priority_set_direct (session, "NORMAL", &err); if (ret < 0) { if (ret == GNUTLS_E_INVALID_REQUEST) { fprintf (stderr, "Syntax error at: %s\n", err); } exit (1); } /* put the x509 credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); gnutls_server_name_set (session, GNUTLS_NAME_DNS, "my_host_name", strlen("my_host_name")); /* connect to the peer */ sd = udp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* set the connection MTU */ gnutls_dtls_set_mtu (session, 1000); /* Perform the TLS handshake */ do { ret = gnutls_handshake (session); } while (ret < 0 && gnutls_error_is_fatal (ret) == 0); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); /* It is suggested not to use GNUTLS_SHUT_RDWR in DTLS * connections because the peer's closure message might * be lost */ gnutls_bye (session, GNUTLS_SHUT_WR); end: udp_close (sd); gnutls_deinit (session); gnutls_certificate_free_credentials (xcred); gnutls_global_deinit (); return 0; }
Next: Using a callback to select the certificate to use, Previous: Simple Datagram TLS client example, Up: Client examples [Contents][Index]
Most of the times it is desirable to know the security properties of the current established session. This includes the underlying ciphers and the protocols involved. That is the purpose of the following function. Note that this function will print meaningful values only if called after a successful gnutls_handshake.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <gnutls/gnutls.h> #include <gnutls/x509.h> #include "examples.h" /* This function will print some details of the * given session. */ int print_info (gnutls_session_t session) { const char *tmp; gnutls_credentials_type_t cred; gnutls_kx_algorithm_t kx; int dhe, ecdh; dhe = ecdh = 0; /* print the key exchange's algorithm name */ kx = gnutls_kx_get (session); tmp = gnutls_kx_get_name (kx); printf ("- Key Exchange: %s\n", tmp); /* Check the authentication type used and switch * to the appropriate. */ cred = gnutls_auth_get_type (session); switch (cred) { case GNUTLS_CRD_IA: printf ("- TLS/IA session\n"); break; #ifdef ENABLE_SRP case GNUTLS_CRD_SRP: printf ("- SRP session with username %s\n", gnutls_srp_server_get_username (session)); break; #endif case GNUTLS_CRD_PSK: /* This returns NULL in server side. */ if (gnutls_psk_client_get_hint (session) != NULL) printf ("- PSK authentication. PSK hint '%s'\n", gnutls_psk_client_get_hint (session)); /* This returns NULL in client side. */ if (gnutls_psk_server_get_username (session) != NULL) printf ("- PSK authentication. Connected as '%s'\n", gnutls_psk_server_get_username (session)); if (kx == GNUTLS_KX_ECDHE_PSK) ecdh = 1; else if (kx == GNUTLS_KX_DHE_PSK) dhe = 1; break; case GNUTLS_CRD_ANON: /* anonymous authentication */ printf ("- Anonymous authentication.\n"); if (kx == GNUTLS_KX_ANON_ECDH) ecdh = 1; else if (kx == GNUTLS_KX_ANON_DH) dhe = 1; break; case GNUTLS_CRD_CERTIFICATE: /* certificate authentication */ /* Check if we have been using ephemeral Diffie-Hellman. */ if (kx == GNUTLS_KX_DHE_RSA || kx == GNUTLS_KX_DHE_DSS) dhe = 1; else if (kx == GNUTLS_KX_ECDHE_RSA || kx == GNUTLS_KX_ECDHE_ECDSA) ecdh = 1; /* if the certificate list is available, then * print some information about it. */ print_x509_certificate_info (session); } /* switch */ if (ecdh != 0) printf ("- Ephemeral ECDH using curve %s\n", gnutls_ecc_curve_get_name (gnutls_ecc_curve_get (session))); else if (dhe != 0) printf ("- Ephemeral DH using prime of %d bits\n", gnutls_dh_get_prime_bits (session)); /* print the protocol's name (ie TLS 1.0) */ tmp = gnutls_protocol_get_name (gnutls_protocol_get_version (session)); printf ("- Protocol: %s\n", tmp); /* print the certificate type of the peer. * ie X.509 */ tmp = gnutls_certificate_type_get_name (gnutls_certificate_type_get (session)); printf ("- Certificate Type: %s\n", tmp); /* print the compression algorithm (if any) */ tmp = gnutls_compression_get_name (gnutls_compression_get (session)); printf ("- Compression: %s\n", tmp); /* print the name of the cipher used. * ie 3DES. */ tmp = gnutls_cipher_get_name (gnutls_cipher_get (session)); printf ("- Cipher: %s\n", tmp); /* Print the MAC algorithms name. * ie SHA1 */ tmp = gnutls_mac_get_name (gnutls_mac_get (session)); printf ("- MAC: %s\n", tmp); return 0; }
Next: Verifying a certificate, Previous: Obtaining session information, Up: Client examples [Contents][Index]
There are cases where a client holds several certificate and key pairs, and may not want to load all of them in the credentials structure. The following example demonstrates the use of the certificate selection callback.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <unistd.h> #include <gnutls/gnutls.h> #include <gnutls/x509.h> #include <gnutls/abstract.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> /* A TLS client that loads the certificate and key. */ #define MAX_BUF 1024 #define MSG "GET / HTTP/1.0\r\n\r\n" #define CERT_FILE "cert.pem" #define KEY_FILE "key.pem" #define CAFILE "/etc/ssl/certs/ca-certificates.crt" extern int tcp_connect (void); extern void tcp_close (int sd); static int cert_callback (gnutls_session_t session, const gnutls_datum_t * req_ca_rdn, int nreqs, const gnutls_pk_algorithm_t * sign_algos, int sign_algos_length, gnutls_pcert_st ** pcert, unsigned int *pcert_length, gnutls_privkey_t * pkey); gnutls_pcert_st crt; gnutls_privkey_t key; /* Helper functions to load a certificate and key * files into memory. */ static gnutls_datum_t load_file (const char *file) { FILE *f; gnutls_datum_t loaded_file = { NULL, 0 }; long filelen; void *ptr; if (!(f = fopen (file, "r")) || fseek (f, 0, SEEK_END) != 0 || (filelen = ftell (f)) < 0 || fseek (f, 0, SEEK_SET) != 0 || !(ptr = malloc ((size_t) filelen)) || fread (ptr, 1, (size_t) filelen, f) < (size_t) filelen) { if (f) fclose (f); return loaded_file; } loaded_file.data = ptr; loaded_file.size = (unsigned int) filelen; return loaded_file; } static void unload_file (gnutls_datum_t data) { free (data.data); } /* Load the certificate and the private key. */ static void load_keys (void) { int ret; gnutls_datum_t data; gnutls_x509_privkey_t x509_key; data = load_file (CERT_FILE); if (data.data == NULL) { fprintf (stderr, "*** Error loading certificate file.\n"); exit (1); } ret = gnutls_pcert_import_x509_raw (&crt, &data, GNUTLS_X509_FMT_PEM, 0); if (ret < 0) { fprintf (stderr, "*** Error loading certificate file: %s\n", gnutls_strerror (ret)); exit (1); } unload_file (data); data = load_file (KEY_FILE); if (data.data == NULL) { fprintf (stderr, "*** Error loading key file.\n"); exit (1); } gnutls_x509_privkey_init (&x509_key); ret = gnutls_x509_privkey_import (x509_key, &data, GNUTLS_X509_FMT_PEM); if (ret < 0) { fprintf (stderr, "*** Error loading key file: %s\n", gnutls_strerror (ret)); exit (1); } gnutls_privkey_init (&key); ret = gnutls_privkey_import_x509 (key, x509_key, GNUTLS_PRIVKEY_IMPORT_AUTO_RELEASE); if (ret < 0) { fprintf (stderr, "*** Error importing key: %s\n", gnutls_strerror (ret)); exit (1); } unload_file (data); } int main (void) { int ret, sd, ii; gnutls_session_t session; gnutls_priority_t priorities_cache; char buffer[MAX_BUF + 1]; gnutls_certificate_credentials_t xcred; /* Allow connections to servers that have OpenPGP keys as well. */ gnutls_global_init (); load_keys (); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); /* priorities */ gnutls_priority_init (&priorities_cache, "NORMAL", NULL); /* sets the trusted cas file */ gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_retrieve_function2 (xcred, cert_callback); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); /* Use default priorities */ gnutls_priority_set (session, priorities_cache); /* put the x509 credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); /* connect to the peer */ sd = tcp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ ret = gnutls_handshake (session); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_certificate_free_credentials (xcred); gnutls_priority_deinit (priorities_cache); gnutls_global_deinit (); return 0; } /* This callback should be associated with a session by calling * gnutls_certificate_client_set_retrieve_function( session, cert_callback), * before a handshake. */ static int cert_callback (gnutls_session_t session, const gnutls_datum_t * req_ca_rdn, int nreqs, const gnutls_pk_algorithm_t * sign_algos, int sign_algos_length, gnutls_pcert_st ** pcert, unsigned int *pcert_length, gnutls_privkey_t * pkey) { char issuer_dn[256]; int i, ret; size_t len; gnutls_certificate_type_t type; /* Print the server's trusted CAs */ if (nreqs > 0) printf ("- Server's trusted authorities:\n"); else printf ("- Server did not send us any trusted authorities names.\n"); /* print the names (if any) */ for (i = 0; i < nreqs; i++) { len = sizeof (issuer_dn); ret = gnutls_x509_rdn_get (&req_ca_rdn[i], issuer_dn, &len); if (ret >= 0) { printf (" [%d]: ", i); printf ("%s\n", issuer_dn); } } /* Select a certificate and return it. * The certificate must be of any of the "sign algorithms" * supported by the server. */ type = gnutls_certificate_type_get (session); if (type == GNUTLS_CRT_X509) { *pcert_length = 1; *pcert = &crt; *pkey = key; } else { return -1; } return 0; }
Next: Client using a smart card with TLS, Previous: Using a callback to select the certificate to use, Up: Client examples [Contents][Index]
An example is listed below which uses the high level verification functions to verify a given certificate list.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <gnutls/gnutls.h> #include <gnutls/x509.h> #include "examples.h" /* All the available CRLs */ gnutls_x509_crl_t *crl_list; int crl_list_size; /* All the available trusted CAs */ gnutls_x509_crt_t *ca_list; int ca_list_size; static int print_details_func (gnutls_x509_crt_t cert, gnutls_x509_crt_t issuer, gnutls_x509_crl_t crl, unsigned int verification_output); /* This function will try to verify the peer's certificate chain, and * also check if the hostname matches. */ void verify_certificate_chain (const char *hostname, const gnutls_datum_t * cert_chain, int cert_chain_length) { int i; gnutls_x509_trust_list_t tlist; gnutls_x509_crt_t *cert; unsigned int output; /* Initialize the trusted certificate list. This should be done * once on initialization. gnutls_x509_crt_list_import2() and * gnutls_x509_crl_list_import2() can be used to load them. */ gnutls_x509_trust_list_init (&tlist, 0); gnutls_x509_trust_list_add_cas (tlist, ca_list, ca_list_size, 0); gnutls_x509_trust_list_add_crls (tlist, crl_list, crl_list_size, GNUTLS_TL_VERIFY_CRL, 0); cert = malloc (sizeof (*cert) * cert_chain_length); /* Import all the certificates in the chain to * native certificate format. */ for (i = 0; i < cert_chain_length; i++) { gnutls_x509_crt_init (&cert[i]); gnutls_x509_crt_import (cert[i], &cert_chain[i], GNUTLS_X509_FMT_DER); } gnutls_x509_trust_list_verify_named_crt (tlist, cert[0], hostname, strlen (hostname), GNUTLS_VERIFY_DISABLE_CRL_CHECKS, &output, print_details_func); /* if this certificate is not explicitly trusted verify against CAs */ if (output != 0) { gnutls_x509_trust_list_verify_crt (tlist, cert, cert_chain_length, 0, &output, print_details_func); } if (output & GNUTLS_CERT_INVALID) { fprintf (stderr, "Not trusted"); if (output & GNUTLS_CERT_SIGNER_NOT_FOUND) fprintf (stderr, ": no issuer was found"); if (output & GNUTLS_CERT_SIGNER_NOT_CA) fprintf (stderr, ": issuer is not a CA"); if (output & GNUTLS_CERT_NOT_ACTIVATED) fprintf (stderr, ": not yet activated\n"); if (output & GNUTLS_CERT_EXPIRED) fprintf (stderr, ": expired\n"); fprintf (stderr, "\n"); } else fprintf (stderr, "Trusted\n"); /* Check if the name in the first certificate matches our destination! */ if (!gnutls_x509_crt_check_hostname (cert[0], hostname)) { printf ("The certificate's owner does not match hostname '%s'\n", hostname); } gnutls_x509_trust_list_deinit (tlist, 1); return; } static int print_details_func (gnutls_x509_crt_t cert, gnutls_x509_crt_t issuer, gnutls_x509_crl_t crl, unsigned int verification_output) { char name[512]; char issuer_name[512]; size_t name_size; size_t issuer_name_size; issuer_name_size = sizeof (issuer_name); gnutls_x509_crt_get_issuer_dn (cert, issuer_name, &issuer_name_size); name_size = sizeof (name); gnutls_x509_crt_get_dn (cert, name, &name_size); fprintf (stdout, "\tSubject: %s\n", name); fprintf (stdout, "\tIssuer: %s\n", issuer_name); if (issuer != NULL) { issuer_name_size = sizeof (issuer_name); gnutls_x509_crt_get_dn (issuer, issuer_name, &issuer_name_size); fprintf (stdout, "\tVerified against: %s\n", issuer_name); } if (crl != NULL) { issuer_name_size = sizeof (issuer_name); gnutls_x509_crl_get_issuer_dn (crl, issuer_name, &issuer_name_size); fprintf (stdout, "\tVerified against CRL of: %s\n", issuer_name); } fprintf (stdout, "\tVerification output: %x\n\n", verification_output); return 0; }
Next: Client with Resume capability example, Previous: Verifying a certificate, Up: Client examples [Contents][Index]
This example will demonstrate how to load keys and certificates from a smart-card or any other PKCS #11 token, and use it in a TLS connection.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <unistd.h> #include <gnutls/gnutls.h> #include <gnutls/x509.h> #include <gnutls/pkcs11.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <getpass.h> /* for getpass() */ /* A TLS client that loads the certificate and key. */ #define MAX_BUF 1024 #define MSG "GET / HTTP/1.0\r\n\r\n" #define MIN(x,y) (((x)<(y))?(x):(y)) #define CAFILE "/etc/ssl/certs/ca-certificates.crt" /* The URLs of the objects can be obtained * using p11tool --list-all --login */ #define KEY_URL "pkcs11:manufacturer=SomeManufacturer;object=Private%20Key" \ ";objecttype=private;id=%db%5b%3e%b5%72%33" #define CERT_URL "pkcs11:manufacturer=SomeManufacturer;object=Certificate;" \ "objecttype=cert;id=db%5b%3e%b5%72%33" extern int tcp_connect (void); extern void tcp_close (int sd); static int pin_callback (void *user, int attempt, const char *token_url, const char *token_label, unsigned int flags, char *pin, size_t pin_max) { const char *password; int len; /* Note that a PIN callback may be called multiple times during a * session. It is expected to cache and return the same PIN for * the same token_url, unless flags is set to GNUTLS_PKCS11_PIN_WRONG. */ printf ("PIN required for token '%s' with URL '%s'\n", token_label, token_url); if (flags & GNUTLS_PKCS11_PIN_FINAL_TRY) printf ("*** This is the final try before locking!\n"); if (flags & GNUTLS_PKCS11_PIN_COUNT_LOW) printf ("*** Only few tries left before locking!\n"); if (flags & GNUTLS_PKCS11_PIN_WRONG) printf ("*** Wrong PIN\n"); password = getpass ("Enter pin: "); if (password == NULL || password[0] == 0) { fprintf (stderr, "No password given\n"); exit (1); } len = MIN (pin_max, strlen (password)); memcpy (pin, password, len); pin[len] = 0; return 0; } int main (void) { int ret, sd, ii; gnutls_session_t session; gnutls_priority_t priorities_cache; char buffer[MAX_BUF + 1]; gnutls_certificate_credentials_t xcred; /* Allow connections to servers that have OpenPGP keys as well. */ gnutls_global_init (); /* PKCS11 private key operations might require PIN. * Register a callback. */ gnutls_pkcs11_set_pin_function (pin_callback, NULL); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); /* priorities */ gnutls_priority_init (&priorities_cache, "NORMAL", NULL); /* sets the trusted cas file */ gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_x509_key_file (xcred, CERT_URL, KEY_URL, GNUTLS_X509_FMT_DER); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); /* Use default priorities */ gnutls_priority_set (session, priorities_cache); /* put the x509 credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); /* connect to the peer */ sd = tcp_connect (); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ ret = gnutls_handshake (session); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_certificate_free_credentials (xcred); gnutls_priority_deinit (priorities_cache); gnutls_global_deinit (); return 0; }
Next: Simple client example with SRP authentication, Previous: Client using a smart card with TLS, Up: Client examples [Contents][Index]
This is a modification of the simple client example. Here we demonstrate the use of session resumption. The client tries to connect once using TLS, close the connection and then try to establish a new connection using the previously negotiated data.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <string.h> #include <stdio.h> #include <stdlib.h> #include <gnutls/gnutls.h> /* Those functions are defined in other examples. */ extern void check_alert (gnutls_session_t session, int ret); extern int tcp_connect (void); extern void tcp_close (int sd); #define MAX_BUF 1024 #define CAFILE "/etc/ssl/certs/ca-certificates.crt" #define MSG "GET / HTTP/1.0\r\n\r\n" int main (void) { int ret; int sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; gnutls_certificate_credentials_t xcred; /* variables used in session resuming */ int t; char *session_data = NULL; size_t session_data_size = 0; gnutls_global_init (); /* X509 stuff */ gnutls_certificate_allocate_credentials (&xcred); gnutls_certificate_set_x509_trust_file (xcred, CAFILE, GNUTLS_X509_FMT_PEM); for (t = 0; t < 2; t++) { /* connect 2 times to the server */ sd = tcp_connect (); gnutls_init (&session, GNUTLS_CLIENT); gnutls_priority_set_direct (session, "PERFORMANCE:!ARCFOUR-128", NULL); gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, xcred); if (t > 0) { /* if this is not the first time we connect */ gnutls_session_set_data (session, session_data, session_data_size); free (session_data); } gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ do { ret = gnutls_handshake (session); } while (ret < 0 && gnutls_error_is_fatal (ret) == 0); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } if (t == 0) { /* the first time we connect */ /* get the session data size */ gnutls_session_get_data (session, NULL, &session_data_size); session_data = malloc (session_data_size); /* put session data to the session variable */ gnutls_session_get_data (session, session_data, &session_data_size); } else { /* the second time we connect */ /* check if we actually resumed the previous session */ if (gnutls_session_is_resumed (session) != 0) { printf ("- Previous session was resumed\n"); } else { fprintf (stderr, "*** Previous session was NOT resumed\n"); } } /* This function was defined in a previous example */ /* print_info(session); */ gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("- Peer has closed the TLS connection\n"); goto end; } else if (ret < 0) { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); } /* for() */ gnutls_certificate_free_credentials (xcred); gnutls_global_deinit (); return 0; }
Next: Simple client example in C++, Previous: Client with Resume capability example, Up: Client examples [Contents][Index]
The following client is a very simple SRP TLS client which connects to a server and authenticates using a username and a password. The server may authenticate itself using a certificate, and in that case it has to be verified.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <gnutls/gnutls.h> /* Those functions are defined in other examples. */ extern void check_alert (gnutls_session_t session, int ret); extern int tcp_connect (void); extern void tcp_close (int sd); #define MAX_BUF 1024 #define USERNAME "user" #define PASSWORD "pass" #define CAFILE "/etc/ssl/certs/ca-certificates.crt" #define MSG "GET / HTTP/1.0\r\n\r\n" int main (void) { int ret; int sd, ii; gnutls_session_t session; char buffer[MAX_BUF + 1]; gnutls_srp_client_credentials_t srp_cred; gnutls_certificate_credentials_t cert_cred; gnutls_global_init (); gnutls_srp_allocate_client_credentials (&srp_cred); gnutls_certificate_allocate_credentials (&cert_cred); gnutls_certificate_set_x509_trust_file (cert_cred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_srp_set_client_credentials (srp_cred, USERNAME, PASSWORD); /* connects to server */ sd = tcp_connect (); /* Initialize TLS session */ gnutls_init (&session, GNUTLS_CLIENT); /* Set the priorities. */ gnutls_priority_set_direct (session, "NORMAL:+SRP:+SRP-RSA:+SRP-DSS", NULL); /* put the SRP credentials to the current session */ gnutls_credentials_set (session, GNUTLS_CRD_SRP, srp_cred); gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, cert_cred); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); /* Perform the TLS handshake */ do { ret = gnutls_handshake (session); } while (ret < 0 && gnutls_error_is_fatal (ret) == 0); if (ret < 0) { fprintf (stderr, "*** Handshake failed\n"); gnutls_perror (ret); goto end; } else { printf ("- Handshake was completed\n"); } gnutls_record_send (session, MSG, strlen (MSG)); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (gnutls_error_is_fatal (ret) != 0 || ret == 0) { if (ret == 0) { printf ("- Peer has closed the GnuTLS connection\n"); goto end; } else { fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret)); goto end; } } else check_alert (session, ret); if (ret > 0) { printf ("- Received %d bytes: ", ret); for (ii = 0; ii < ret; ii++) { fputc (buffer[ii], stdout); } fputs ("\n", stdout); } gnutls_bye (session, GNUTLS_SHUT_RDWR); end: tcp_close (sd); gnutls_deinit (session); gnutls_srp_free_client_credentials (srp_cred); gnutls_certificate_free_credentials (cert_cred); gnutls_global_deinit (); return 0; }
Next: Helper functions for TCP connections, Previous: Simple client example with SRP authentication, Up: Client examples [Contents][Index]
The following client is a simple example of a client client utilizing the GnuTLS C++ API.
#include <config.h> #include <iostream> #include <stdexcept> #include <gnutls/gnutls.h> #include <gnutls/gnutlsxx.h> #include <cstring> /* for strlen */ /* A very basic TLS client, with anonymous authentication. * written by Eduardo Villanueva Che. */ #define MAX_BUF 1024 #define SA struct sockaddr #define CAFILE "ca.pem" #define MSG "GET / HTTP/1.0\r\n\r\n" extern "C" { int tcp_connect(void); void tcp_close(int sd); } int main(void) { int sd = -1; gnutls_global_init(); try { /* Allow connections to servers that have OpenPGP keys as well. */ gnutls::client_session session; /* X509 stuff */ gnutls::certificate_credentials credentials; /* sets the trusted cas file */ credentials.set_x509_trust_file(CAFILE, GNUTLS_X509_FMT_PEM); /* put the x509 credentials to the current session */ session.set_credentials(credentials); /* Use default priorities */ session.set_priority ("NORMAL", NULL); /* connect to the peer */ sd = tcp_connect(); session.set_transport_ptr((gnutls_transport_ptr_t) (ptrdiff_t)sd); /* Perform the TLS handshake */ int ret = session.handshake(); if (ret < 0) { throw std::runtime_error("Handshake failed"); } else { std::cout << "- Handshake was completed" << std::endl; } session.send(MSG, strlen(MSG)); char buffer[MAX_BUF + 1]; ret = session.recv(buffer, MAX_BUF); if (ret == 0) { throw std::runtime_error("Peer has closed the TLS connection"); } else if (ret < 0) { throw std::runtime_error(gnutls_strerror(ret)); } std::cout << "- Received " << ret << " bytes:" << std::endl; std::cout.write(buffer, ret); std::cout << std::endl; session.bye(GNUTLS_SHUT_RDWR); } catch (std::exception &ex) { std::cerr << "Exception caught: " << ex.what() << std::endl; } if (sd != -1) tcp_close(sd); gnutls_global_deinit(); return 0; }
Next: Helper functions for UDP connections, Previous: Simple client example in C++, Up: Client examples [Contents][Index]
Those helper function abstract away TCP connection handling from the other examples. It is required to build some examples.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <netinet/in.h> #include <unistd.h> /* tcp.c */ int tcp_connect (void); void tcp_close (int sd); /* Connects to the peer and returns a socket * descriptor. */ extern int tcp_connect (void) { const char *PORT = "5556"; const char *SERVER = "127.0.0.1"; int err, sd; struct sockaddr_in sa; /* connects to server */ sd = socket (AF_INET, SOCK_STREAM, 0); memset (&sa, '\0', sizeof (sa)); sa.sin_family = AF_INET; sa.sin_port = htons (atoi (PORT)); inet_pton (AF_INET, SERVER, &sa.sin_addr); err = connect (sd, (struct sockaddr *) & sa, sizeof (sa)); if (err < 0) { fprintf (stderr, "Connect error\n"); exit (1); } return sd; } /* closes the given socket descriptor. */ extern void tcp_close (int sd) { shutdown (sd, SHUT_RDWR); /* no more receptions */ close (sd); }
Previous: Helper functions for TCP connections, Up: Client examples [Contents][Index]
The UDP helper functions abstract away UDP connection handling from the other examples. It is required to build the examples using UDP.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <netinet/in.h> #include <unistd.h> /* udp.c */ int udp_connect (void); void udp_close (int sd); /* Connects to the peer and returns a socket * descriptor. */ extern int udp_connect (void) { const char *PORT = "5557"; const char *SERVER = "127.0.0.1"; int err, sd, optval; struct sockaddr_in sa; /* connects to server */ sd = socket (AF_INET, SOCK_DGRAM, 0); memset (&sa, '\0', sizeof (sa)); sa.sin_family = AF_INET; sa.sin_port = htons (atoi (PORT)); inet_pton (AF_INET, SERVER, &sa.sin_addr); #if defined(IP_DONTFRAG) optval = 1; setsockopt (sd, IPPROTO_IP, IP_DONTFRAG, (const void *) &optval, sizeof (optval)); #elif defined(IP_MTU_DISCOVER) optval = IP_PMTUDISC_DO; setsockopt(sd, IPPROTO_IP, IP_MTU_DISCOVER, (const void*) &optval, sizeof (optval)); #endif err = connect (sd, (struct sockaddr *) & sa, sizeof (sa)); if (err < 0) { fprintf (stderr, "Connect error\n"); exit (1); } return sd; } /* closes the given socket descriptor. */ extern void udp_close (int sd) { close (sd); }
Next: OCSP example, Previous: Client examples, Up: GnuTLS application examples [Contents][Index]
This section contains examples of TLS and SSL servers, using GnuTLS.
Next: Echo server with OpenPGP authentication, Up: Server examples [Contents][Index]
This example is a very simple echo server which supports X.509 authentication.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <netinet/in.h> #include <string.h> #include <unistd.h> #include <gnutls/gnutls.h> #define KEYFILE "key.pem" #define CERTFILE "cert.pem" #define CAFILE "/etc/ssl/certs/ca-certificates.crt" #define CRLFILE "crl.pem" /* This is a sample TLS 1.0 echo server, using X.509 authentication. */ #define MAX_BUF 1024 #define PORT 5556 /* listen to 5556 port */ /* These are global */ gnutls_certificate_credentials_t x509_cred; gnutls_priority_t priority_cache; static gnutls_session_t initialize_tls_session (void) { gnutls_session_t session; gnutls_init (&session, GNUTLS_SERVER); gnutls_priority_set (session, priority_cache); gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, x509_cred); /* We don't request any certificate from the client. * If we did we would need to verify it. */ gnutls_certificate_server_set_request (session, GNUTLS_CERT_IGNORE); return session; } static gnutls_dh_params_t dh_params; static int generate_dh_params (void) { int bits = gnutls_sec_param_to_pk_bits (GNUTLS_PK_DH, GNUTLS_SEC_PARAM_LOW); /* Generate Diffie-Hellman parameters - for use with DHE * kx algorithms. When short bit length is used, it might * be wise to regenerate parameters often. */ gnutls_dh_params_init (&dh_params); gnutls_dh_params_generate2 (dh_params, bits); return 0; } int main (void) { int listen_sd; int sd, ret; struct sockaddr_in sa_serv; struct sockaddr_in sa_cli; socklen_t client_len; char topbuf[512]; gnutls_session_t session; char buffer[MAX_BUF + 1]; int optval = 1; /* this must be called once in the program */ gnutls_global_init (); gnutls_certificate_allocate_credentials (&x509_cred); /* gnutls_certificate_set_x509_system_trust(xcred); */ gnutls_certificate_set_x509_trust_file (x509_cred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_x509_crl_file (x509_cred, CRLFILE, GNUTLS_X509_FMT_PEM); ret = gnutls_certificate_set_x509_key_file (x509_cred, CERTFILE, KEYFILE, GNUTLS_X509_FMT_PEM); if (ret < 0) { printf("No certificate or key were found\n"); exit(1); } generate_dh_params (); gnutls_priority_init (&priority_cache, "PERFORMANCE:%SERVER_PRECEDENCE", NULL); gnutls_certificate_set_dh_params (x509_cred, dh_params); /* Socket operations */ listen_sd = socket (AF_INET, SOCK_STREAM, 0); memset (&sa_serv, '\0', sizeof (sa_serv)); sa_serv.sin_family = AF_INET; sa_serv.sin_addr.s_addr = INADDR_ANY; sa_serv.sin_port = htons (PORT); /* Server Port number */ setsockopt (listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval, sizeof (int)); bind (listen_sd, (struct sockaddr *) & sa_serv, sizeof (sa_serv)); listen (listen_sd, 1024); printf ("Server ready. Listening to port '%d'.\n\n", PORT); client_len = sizeof (sa_cli); for (;;) { session = initialize_tls_session (); sd = accept (listen_sd, (struct sockaddr *) & sa_cli, &client_len); printf ("- connection from %s, port %d\n", inet_ntop (AF_INET, &sa_cli.sin_addr, topbuf, sizeof (topbuf)), ntohs (sa_cli.sin_port)); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); do { ret = gnutls_handshake (session); } while (ret < 0 && gnutls_error_is_fatal (ret) == 0); if (ret < 0) { close (sd); gnutls_deinit (session); fprintf (stderr, "*** Handshake has failed (%s)\n\n", gnutls_strerror (ret)); continue; } printf ("- Handshake was completed\n"); /* see the Getting peer's information example */ /* print_info(session); */ for (;;) { memset (buffer, 0, MAX_BUF + 1); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("\n- Peer has closed the GnuTLS connection\n"); break; } else if (ret < 0) { fprintf (stderr, "\n*** Received corrupted " "data(%d). Closing the connection.\n\n", ret); break; } else if (ret > 0) { /* echo data back to the client */ gnutls_record_send (session, buffer, strlen (buffer)); } } printf ("\n"); /* do not wait for the peer to close the connection. */ gnutls_bye (session, GNUTLS_SHUT_WR); close (sd); gnutls_deinit (session); } close (listen_sd); gnutls_certificate_free_credentials (x509_cred); gnutls_priority_deinit (priority_cache); gnutls_global_deinit (); return 0; }
Next: Echo server with SRP authentication, Previous: Echo server with X.509 authentication, Up: Server examples [Contents][Index]
The following example is an echo server which supports OpenPGP key authentication. You can easily combine this functionality —that is have a server that supports both X.509 and OpenPGP certificates— but we separated them to keep these examples as simple as possible.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <netinet/in.h> #include <string.h> #include <unistd.h> #include <gnutls/gnutls.h> #include <gnutls/openpgp.h> #define KEYFILE "secret.asc" #define CERTFILE "public.asc" #define RINGFILE "ring.gpg" /* This is a sample TLS 1.0-OpenPGP echo server. */ #define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);} #define MAX_BUF 1024 #define PORT 5556 /* listen to 5556 port */ #define DH_BITS 1024 /* These are global */ gnutls_certificate_credentials_t cred; gnutls_dh_params_t dh_params; static int generate_dh_params (void) { /* Generate Diffie-Hellman parameters - for use with DHE * kx algorithms. These should be discarded and regenerated * once a day, once a week or once a month. Depending on the * security requirements. */ gnutls_dh_params_init (&dh_params); gnutls_dh_params_generate2 (dh_params, DH_BITS); return 0; } static gnutls_session_t initialize_tls_session (void) { gnutls_session_t session; gnutls_init (&session, GNUTLS_SERVER); gnutls_priority_set_direct (session, "NORMAL:+CTYPE-OPENPGP", NULL); /* request client certificate if any. */ gnutls_certificate_server_set_request (session, GNUTLS_CERT_REQUEST); gnutls_dh_set_prime_bits (session, DH_BITS); return session; } int main (void) { int err, listen_sd; int sd, ret; struct sockaddr_in sa_serv; struct sockaddr_in sa_cli; socklen_t client_len; char topbuf[512]; gnutls_session_t session; char buffer[MAX_BUF + 1]; int optval = 1; char name[256]; strcpy (name, "Echo Server"); /* this must be called once in the program */ gnutls_global_init (); gnutls_certificate_allocate_credentials (&cred); gnutls_certificate_set_openpgp_keyring_file (cred, RINGFILE, GNUTLS_OPENPGP_FMT_BASE64); gnutls_certificate_set_openpgp_key_file (cred, CERTFILE, KEYFILE, GNUTLS_OPENPGP_FMT_BASE64); generate_dh_params (); gnutls_certificate_set_dh_params (cred, dh_params); /* Socket operations */ listen_sd = socket (AF_INET, SOCK_STREAM, 0); SOCKET_ERR (listen_sd, "socket"); memset (&sa_serv, '\0', sizeof (sa_serv)); sa_serv.sin_family = AF_INET; sa_serv.sin_addr.s_addr = INADDR_ANY; sa_serv.sin_port = htons (PORT); /* Server Port number */ setsockopt (listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval, sizeof (int)); err = bind (listen_sd, (struct sockaddr *) & sa_serv, sizeof (sa_serv)); SOCKET_ERR (err, "bind"); err = listen (listen_sd, 1024); SOCKET_ERR (err, "listen"); printf ("%s ready. Listening to port '%d'.\n\n", name, PORT); client_len = sizeof (sa_cli); for (;;) { session = initialize_tls_session (); sd = accept (listen_sd, (struct sockaddr *) & sa_cli, &client_len); printf ("- connection from %s, port %d\n", inet_ntop (AF_INET, &sa_cli.sin_addr, topbuf, sizeof (topbuf)), ntohs (sa_cli.sin_port)); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); ret = gnutls_handshake (session); if (ret < 0) { close (sd); gnutls_deinit (session); fprintf (stderr, "*** Handshake has failed (%s)\n\n", gnutls_strerror (ret)); continue; } printf ("- Handshake was completed\n"); /* see the Getting peer's information example */ /* print_info(session); */ for (;;) { memset (buffer, 0, MAX_BUF + 1); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("\n- Peer has closed the GnuTLS connection\n"); break; } else if (ret < 0) { fprintf (stderr, "\n*** Received corrupted " "data(%d). Closing the connection.\n\n", ret); break; } else if (ret > 0) { /* echo data back to the client */ gnutls_record_send (session, buffer, strlen (buffer)); } } printf ("\n"); /* do not wait for the peer to close the connection. */ gnutls_bye (session, GNUTLS_SHUT_WR); close (sd); gnutls_deinit (session); } close (listen_sd); gnutls_certificate_free_credentials (cred); gnutls_global_deinit (); return 0; }
Next: Echo server with anonymous authentication, Previous: Echo server with OpenPGP authentication, Up: Server examples [Contents][Index]
This is a server which supports SRP authentication. It is also possible to combine this functionality with a certificate server. Here it is separate for simplicity.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <netinet/in.h> #include <string.h> #include <unistd.h> #include <gnutls/gnutls.h> #define SRP_PASSWD "tpasswd" #define SRP_PASSWD_CONF "tpasswd.conf" #define KEYFILE "key.pem" #define CERTFILE "cert.pem" #define CAFILE "/etc/ssl/certs/ca-certificates.crt" /* This is a sample TLS-SRP echo server. */ #define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);} #define MAX_BUF 1024 #define PORT 5556 /* listen to 5556 port */ /* These are global */ gnutls_srp_server_credentials_t srp_cred; gnutls_certificate_credentials_t cert_cred; static gnutls_session_t initialize_tls_session (void) { gnutls_session_t session; gnutls_init (&session, GNUTLS_SERVER); gnutls_priority_set_direct (session, "NORMAL:-KX-ALL:+SRP:+SRP-DSS:+SRP-RSA", NULL); gnutls_credentials_set (session, GNUTLS_CRD_SRP, srp_cred); /* for the certificate authenticated ciphersuites. */ gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, cert_cred); /* request client certificate if any. */ gnutls_certificate_server_set_request (session, GNUTLS_CERT_IGNORE); return session; } int main (void) { int err, listen_sd; int sd, ret; struct sockaddr_in sa_serv; struct sockaddr_in sa_cli; socklen_t client_len; char topbuf[512]; gnutls_session_t session; char buffer[MAX_BUF + 1]; int optval = 1; char name[256]; strcpy (name, "Echo Server"); gnutls_global_init (); /* SRP_PASSWD a password file (created with the included srptool utility) */ gnutls_srp_allocate_server_credentials (&srp_cred); gnutls_srp_set_server_credentials_file (srp_cred, SRP_PASSWD, SRP_PASSWD_CONF); gnutls_certificate_allocate_credentials (&cert_cred); gnutls_certificate_set_x509_trust_file (cert_cred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_x509_key_file (cert_cred, CERTFILE, KEYFILE, GNUTLS_X509_FMT_PEM); /* TCP socket operations */ listen_sd = socket (AF_INET, SOCK_STREAM, 0); SOCKET_ERR (listen_sd, "socket"); memset (&sa_serv, '\0', sizeof (sa_serv)); sa_serv.sin_family = AF_INET; sa_serv.sin_addr.s_addr = INADDR_ANY; sa_serv.sin_port = htons (PORT); /* Server Port number */ setsockopt (listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval, sizeof (int)); err = bind (listen_sd, (struct sockaddr *) & sa_serv, sizeof (sa_serv)); SOCKET_ERR (err, "bind"); err = listen (listen_sd, 1024); SOCKET_ERR (err, "listen"); printf ("%s ready. Listening to port '%d'.\n\n", name, PORT); client_len = sizeof (sa_cli); for (;;) { session = initialize_tls_session (); sd = accept (listen_sd, (struct sockaddr *) & sa_cli, &client_len); printf ("- connection from %s, port %d\n", inet_ntop (AF_INET, &sa_cli.sin_addr, topbuf, sizeof (topbuf)), ntohs (sa_cli.sin_port)); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd); do { ret = gnutls_handshake (session); } while (ret < 0 && gnutls_error_is_fatal (ret) == 0); if (ret < 0) { close (sd); gnutls_deinit (session); fprintf (stderr, "*** Handshake has failed (%s)\n\n", gnutls_strerror (ret)); continue; } printf ("- Handshake was completed\n"); printf ("- User %s was connected\n", gnutls_srp_server_get_username(session)); /* print_info(session); */ for (;;) { memset (buffer, 0, MAX_BUF + 1); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("\n- Peer has closed the GnuTLS connection\n"); break; } else if (ret < 0) { fprintf (stderr, "\n*** Received corrupted " "data(%d). Closing the connection.\n\n", ret); break; } else if (ret > 0) { /* echo data back to the client */ gnutls_record_send (session, buffer, strlen (buffer)); } } printf ("\n"); /* do not wait for the peer to close the connection. */ gnutls_bye (session, GNUTLS_SHUT_WR); close (sd); gnutls_deinit (session); } close (listen_sd); gnutls_srp_free_server_credentials (srp_cred); gnutls_certificate_free_credentials (cert_cred); gnutls_global_deinit (); return 0; }
Next: DTLS echo server with X.509 authentication, Previous: Echo server with SRP authentication, Up: Server examples [Contents][Index]
This example server supports anonymous authentication, and could be used to serve the example client for anonymous authentication.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <netinet/in.h> #include <string.h> #include <unistd.h> #include <gnutls/gnutls.h> /* This is a sample TLS 1.0 echo server, for anonymous authentication only. */ #define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);} #define MAX_BUF 1024 #define PORT 5556 /* listen to 5556 port */ #define DH_BITS 1024 /* These are global */ gnutls_anon_server_credentials_t anoncred; static gnutls_session_t initialize_tls_session (void) { gnutls_session_t session; gnutls_init (&session, GNUTLS_SERVER); gnutls_priority_set_direct (session, "NORMAL:+ANON-ECDH:+ANON-DH", NULL); gnutls_credentials_set (session, GNUTLS_CRD_ANON, anoncred); gnutls_dh_set_prime_bits (session, DH_BITS); return session; } static gnutls_dh_params_t dh_params; static int generate_dh_params (void) { /* Generate Diffie-Hellman parameters - for use with DHE * kx algorithms. These should be discarded and regenerated * once a day, once a week or once a month. Depending on the * security requirements. */ gnutls_dh_params_init (&dh_params); gnutls_dh_params_generate2 (dh_params, DH_BITS); return 0; } int main (void) { int err, listen_sd; int sd, ret; struct sockaddr_in sa_serv; struct sockaddr_in sa_cli; socklen_t client_len; char topbuf[512]; gnutls_session_t session; char buffer[MAX_BUF + 1]; int optval = 1; /* this must be called once in the program */ gnutls_global_init (); gnutls_anon_allocate_server_credentials (&anoncred); generate_dh_params (); gnutls_anon_set_server_dh_params (anoncred, dh_params); /* Socket operations */ listen_sd = socket (AF_INET, SOCK_STREAM, 0); SOCKET_ERR (listen_sd, "socket"); memset (&sa_serv, '\0', sizeof (sa_serv)); sa_serv.sin_family = AF_INET; sa_serv.sin_addr.s_addr = INADDR_ANY; sa_serv.sin_port = htons (PORT); /* Server Port number */ setsockopt (listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval, sizeof (int)); err = bind (listen_sd, (struct sockaddr *) & sa_serv, sizeof (sa_serv)); SOCKET_ERR (err, "bind"); err = listen (listen_sd, 1024); SOCKET_ERR (err, "listen"); printf ("Server ready. Listening to port '%d'.\n\n", PORT); client_len = sizeof (sa_cli); for (;;) { session = initialize_tls_session (); sd = accept (listen_sd, (struct sockaddr *) & sa_cli, &client_len); printf ("- connection from %s, port %d\n", inet_ntop (AF_INET, &sa_cli.sin_addr, topbuf, sizeof (topbuf)), ntohs (sa_cli.sin_port)); gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) ((ptrdiff_t) sd)); do { ret = gnutls_handshake (session); } while (ret < 0 && gnutls_error_is_fatal (ret) == 0); if (ret < 0) { close (sd); gnutls_deinit (session); fprintf (stderr, "*** Handshake has failed (%s)\n\n", gnutls_strerror (ret)); continue; } printf ("- Handshake was completed\n"); /* see the Getting peer's information example */ /* print_info(session); */ for (;;) { memset (buffer, 0, MAX_BUF + 1); ret = gnutls_record_recv (session, buffer, MAX_BUF); if (ret == 0) { printf ("\n- Peer has closed the GnuTLS connection\n"); break; } else if (ret < 0) { fprintf (stderr, "\n*** Received corrupted " "data(%d). Closing the connection.\n\n", ret); break; } else if (ret > 0) { /* echo data back to the client */ gnutls_record_send (session, buffer, strlen (buffer)); } } printf ("\n"); /* do not wait for the peer to close the connection. */ gnutls_bye (session, GNUTLS_SHUT_WR); close (sd); gnutls_deinit (session); } close (listen_sd); gnutls_anon_free_server_credentials (anoncred); gnutls_global_deinit (); return 0; }
Previous: Echo server with anonymous authentication, Up: Server examples [Contents][Index]
This example is a very simple echo server using Datagram TLS and X.509 authentication.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <netinet/in.h> #include <sys/select.h> #include <netdb.h> #include <string.h> #include <unistd.h> #include <gnutls/gnutls.h> #include <gnutls/dtls.h> #define KEYFILE "key.pem" #define CERTFILE "cert.pem" #define CAFILE "/etc/ssl/certs/ca-certificates.crt" #define CRLFILE "crl.pem" /* This is a sample DTLS echo server, using X.509 authentication. * Note that error checking is minimal to simplify the example. */ #define MAX_BUFFER 1024 #define PORT 5556 typedef struct { gnutls_session_t session; int fd; struct sockaddr *cli_addr; socklen_t cli_addr_size; } priv_data_st; static int pull_timeout_func (gnutls_transport_ptr_t ptr, unsigned int ms); static ssize_t push_func (gnutls_transport_ptr_t p, const void *data, size_t size); static ssize_t pull_func (gnutls_transport_ptr_t p, void *data, size_t size); static const char *human_addr (const struct sockaddr *sa, socklen_t salen, char *buf, size_t buflen); static int wait_for_connection (int fd); static gnutls_session_t initialize_tls_session (void); static int generate_dh_params (void); /* Use global credentials and parameters to simplify * the example. */ static gnutls_certificate_credentials_t x509_cred; static gnutls_priority_t priority_cache; static gnutls_dh_params_t dh_params; int main (void) { int listen_sd; int sock, ret; struct sockaddr_in sa_serv; struct sockaddr_in cli_addr; socklen_t cli_addr_size; gnutls_session_t session; char buffer[MAX_BUFFER]; priv_data_st priv; gnutls_datum_t cookie_key; gnutls_dtls_prestate_st prestate; int mtu = 1400; unsigned char sequence[8]; /* this must be called once in the program */ gnutls_global_init (); gnutls_certificate_allocate_credentials (&x509_cred); gnutls_certificate_set_x509_trust_file (x509_cred, CAFILE, GNUTLS_X509_FMT_PEM); gnutls_certificate_set_x509_crl_file (x509_cred, CRLFILE, GNUTLS_X509_FMT_PEM); ret = gnutls_certificate_set_x509_key_file (x509_cred, CERTFILE, KEYFILE, GNUTLS_X509_FMT_PEM); if (ret < 0) { printf("No certificate or key were found\n"); exit(1); } generate_dh_params (); gnutls_certificate_set_dh_params (x509_cred, dh_params); gnutls_priority_init (&priority_cache, "PERFORMANCE:-VERS-TLS-ALL:+VERS-DTLS1.0:%SERVER_PRECEDENCE", NULL); gnutls_key_generate (&cookie_key, GNUTLS_COOKIE_KEY_SIZE); /* Socket operations */ listen_sd = socket (AF_INET, SOCK_DGRAM, 0); memset (&sa_serv, '\0', sizeof (sa_serv)); sa_serv.sin_family = AF_INET; sa_serv.sin_addr.s_addr = INADDR_ANY; sa_serv.sin_port = htons (PORT); { /* DTLS requires the IP don't fragment (DF) bit to be set */ #if defined(IP_DONTFRAG) int optval = 1; setsockopt (listen_sd, IPPROTO_IP, IP_DONTFRAG, (const void *) &optval, sizeof (optval)); #elif defined(IP_MTU_DISCOVER) int optval = IP_PMTUDISC_DO; setsockopt(listen_sd, IPPROTO_IP, IP_MTU_DISCOVER, (const void*) &optval, sizeof (optval)); #endif } bind (listen_sd, (struct sockaddr *) &sa_serv, sizeof (sa_serv)); printf ("UDP server ready. Listening to port '%d'.\n\n", PORT); for (;;) { printf ("Waiting for connection...\n"); sock = wait_for_connection (listen_sd); if (sock < 0) continue; cli_addr_size = sizeof (cli_addr); ret = recvfrom (sock, buffer, sizeof (buffer), MSG_PEEK, (struct sockaddr *) &cli_addr, &cli_addr_size); if (ret > 0) { memset (&prestate, 0, sizeof (prestate)); ret = gnutls_dtls_cookie_verify (&cookie_key, &cli_addr, sizeof (cli_addr), buffer, ret, &prestate); if (ret < 0) /* cookie not valid */ { priv_data_st s; memset (&s, 0, sizeof (s)); s.fd = sock; s.cli_addr = (void *) &cli_addr; s.cli_addr_size = sizeof (cli_addr); printf ("Sending hello verify request to %s\n", human_addr ((struct sockaddr *) &cli_addr, sizeof (cli_addr), buffer, sizeof (buffer))); gnutls_dtls_cookie_send (&cookie_key, &cli_addr, sizeof (cli_addr), &prestate, (gnutls_transport_ptr_t) & s, push_func); /* discard peeked data */ recvfrom (sock, buffer, sizeof (buffer), 0, (struct sockaddr *) &cli_addr, &cli_addr_size); usleep (100); continue; } printf ("Accepted connection from %s\n", human_addr ((struct sockaddr *) &cli_addr, sizeof (cli_addr), buffer, sizeof (buffer))); } else continue; session = initialize_tls_session (); gnutls_dtls_prestate_set (session, &prestate); gnutls_dtls_set_mtu (session, mtu); priv.session = session; priv.fd = sock; priv.cli_addr = (struct sockaddr *) &cli_addr; priv.cli_addr_size = sizeof (cli_addr); gnutls_transport_set_ptr (session, &priv); gnutls_transport_set_push_function (session, push_func); gnutls_transport_set_pull_function (session, pull_func); gnutls_transport_set_pull_timeout_function (session, pull_timeout_func); do { ret = gnutls_handshake (session); } while (ret < 0 && gnutls_error_is_fatal (ret) == 0); if (ret < 0) { fprintf (stderr, "Error in handshake(): %s\n", gnutls_strerror (ret)); gnutls_deinit (session); continue; } printf ("- Handshake was completed\n"); for (;;) { do { ret = gnutls_record_recv_seq (session, buffer, MAX_BUFFER, sequence); } while (ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED); if (ret < 0) { fprintf (stderr, "Error in recv(): %s\n", gnutls_strerror (ret)); break; } if (ret == 0) { printf ("EOF\n\n"); break; } buffer[ret] = 0; printf ("received[%.2x%.2x%.2x%.2x%.2x%.2x%.2x%.2x]: %s\n", sequence[0], sequence[1], sequence[2], sequence[3], sequence[4], sequence[5], sequence[6], sequence[7], buffer); /* reply back */ ret = gnutls_record_send (session, buffer, ret); if (ret < 0) { fprintf (stderr, "Error in send(): %s\n", gnutls_strerror (ret)); break; } } gnutls_bye (session, GNUTLS_SHUT_WR); gnutls_deinit (session); } close (listen_sd); gnutls_certificate_free_credentials (x509_cred); gnutls_priority_deinit (priority_cache); gnutls_global_deinit (); return 0; } static int wait_for_connection (int fd) { fd_set rd, wr; int n; FD_ZERO (&rd); FD_ZERO (&wr); FD_SET (fd, &rd); /* waiting part */ n = select (fd + 1, &rd, &wr, NULL, NULL); if (n == -1 && errno == EINTR) return -1; if (n < 0) { perror ("select()"); exit (1); } return fd; } /* Wait for data to be received within a timeout period in milliseconds */ static int pull_timeout_func (gnutls_transport_ptr_t ptr, unsigned int ms) { fd_set rfds; struct timeval tv; priv_data_st *priv = ptr; struct sockaddr_in cli_addr; socklen_t cli_addr_size; int ret; char c; FD_ZERO (&rfds); FD_SET (priv->fd, &rfds); tv.tv_sec = 0; tv.tv_usec = ms * 1000; ret = select (priv->fd + 1, &rfds, NULL, NULL, &tv); if (ret <= 0) return ret; /* only report ok if the next message is from the peer we expect * from */ cli_addr_size = sizeof (cli_addr); ret = recvfrom (priv->fd, &c, 1, MSG_PEEK, (struct sockaddr *) &cli_addr, &cli_addr_size); if (ret > 0) { if (cli_addr_size == priv->cli_addr_size && memcmp (&cli_addr, priv->cli_addr, sizeof (cli_addr)) == 0) return 1; } return 0; } static ssize_t push_func (gnutls_transport_ptr_t p, const void *data, size_t size) { priv_data_st *priv = p; return sendto (priv->fd, data, size, 0, priv->cli_addr, priv->cli_addr_size); } static ssize_t pull_func (gnutls_transport_ptr_t p, void *data, size_t size) { priv_data_st *priv = p; struct sockaddr_in cli_addr; socklen_t cli_addr_size; char buffer[64]; int ret; cli_addr_size = sizeof (cli_addr); ret = recvfrom (priv->fd, data, size, 0, (struct sockaddr *) &cli_addr, &cli_addr_size); if (ret == -1) return ret; if (cli_addr_size == priv->cli_addr_size && memcmp (&cli_addr, priv->cli_addr, sizeof (cli_addr)) == 0) return ret; printf ("Denied connection from %s\n", human_addr ((struct sockaddr *) &cli_addr, sizeof (cli_addr), buffer, sizeof (buffer))); gnutls_transport_set_errno (priv->session, EAGAIN); return -1; } static const char * human_addr (const struct sockaddr *sa, socklen_t salen, char *buf, size_t buflen) { const char *save_buf = buf; size_t l; if (!buf || !buflen) return NULL; *buf = '\0'; switch (sa->sa_family) { #if HAVE_IPV6 case AF_INET6: snprintf (buf, buflen, "IPv6 "); break; #endif case AF_INET: snprintf (buf, buflen, "IPv4 "); break; } l = strlen (buf); buf += l; buflen -= l; if (getnameinfo (sa, salen, buf, buflen, NULL, 0, NI_NUMERICHOST) != 0) return NULL; l = strlen (buf); buf += l; buflen -= l; strncat (buf, " port ", buflen); l = strlen (buf); buf += l; buflen -= l; if (getnameinfo (sa, salen, NULL, 0, buf, buflen, NI_NUMERICSERV) != 0) return NULL; return save_buf; } static gnutls_session_t initialize_tls_session (void) { gnutls_session_t session; gnutls_init (&session, GNUTLS_SERVER | GNUTLS_DATAGRAM); gnutls_priority_set (session, priority_cache); gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, x509_cred); return session; } static int generate_dh_params (void) { int bits = gnutls_sec_param_to_pk_bits (GNUTLS_PK_DH, GNUTLS_SEC_PARAM_LOW); /* Generate Diffie-Hellman parameters - for use with DHE * kx algorithms. When short bit length is used, it might * be wise to regenerate parameters often. */ gnutls_dh_params_init (&dh_params); gnutls_dh_params_generate2 (dh_params, bits); return 0; }
Next: Miscellaneous examples, Previous: Server examples, Up: GnuTLS application examples [Contents][Index]
A small tool to generate OCSP requests.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <string.h> #include <gnutls/gnutls.h> #include <gnutls/crypto.h> #include <gnutls/ocsp.h> #ifndef NO_LIBCURL #include <curl/curl.h> #endif #include "read-file.h" size_t get_data (void *buffer, size_t size, size_t nmemb, void *userp); static gnutls_x509_crt_t load_cert (const char *cert_file); static void _response_info (const gnutls_datum_t * data); static void _generate_request (gnutls_datum_t * rdata, const char *cert_file, const char *issuer_file); static int _verify_response (gnutls_datum_t * data, const char *signer_file); /* This program queries an OCSP server. It expects three files. argv[1] containing the certificate to be checked, argv[2] holding the issuer for this certificate, and argv[3] holding a trusted certificate to verify OCSP's response. argv[4] is optional and should hold the server host name. For simplicity the libcurl library is used. */ int main (int argc, char *argv[]) { gnutls_datum_t ud, tmp; int ret; gnutls_datum_t req; #ifndef NO_LIBCURL CURL *handle; struct curl_slist *headers = NULL; #endif int v, seq; const char *cert_file = argv[1]; const char *issuer_file = argv[2]; const char *signer_file = argv[3]; char *hostname = NULL; gnutls_global_init (); if (argc > 4) hostname = argv[4]; if (hostname == NULL) { gnutls_x509_crt_t cert = load_cert (cert_file); for (seq = 0;; seq++) { ret = gnutls_x509_crt_get_authority_info_access (cert, seq, GNUTLS_IA_OCSP_URI, &tmp, NULL); if (ret == GNUTLS_E_UNKNOWN_ALGORITHM) continue; if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) { fprintf (stderr, "No URI was found in the certificate.\n"); exit (1); } if (ret < 0) { fprintf (stderr, "error: %s\n", gnutls_strerror (ret)); exit (1); } printf ("CA issuers URI: %.*s\n", tmp.size, tmp.data); hostname = malloc (tmp.size + 1); memcpy (hostname, tmp.data, tmp.size); hostname[tmp.size] = 0; gnutls_free (tmp.data); break; } gnutls_x509_crt_deinit (cert); } /* Note that the OCSP servers hostname might be available * using gnutls_x509_crt_get_authority_info_access() in the issuer's * certificate */ memset (&ud, 0, sizeof (ud)); fprintf (stderr, "Connecting to %s\n", hostname); _generate_request (&req, cert_file, issuer_file); #ifndef NO_LIBCURL curl_global_init (CURL_GLOBAL_ALL); handle = curl_easy_init (); if (handle == NULL) exit (1); headers = curl_slist_append (headers, "Content-Type: application/ocsp-request"); curl_easy_setopt (handle, CURLOPT_HTTPHEADER, headers); curl_easy_setopt (handle, CURLOPT_POSTFIELDS, (void *) req.data); curl_easy_setopt (handle, CURLOPT_POSTFIELDSIZE, req.size); curl_easy_setopt (handle, CURLOPT_URL, hostname); curl_easy_setopt (handle, CURLOPT_WRITEFUNCTION, get_data); curl_easy_setopt (handle, CURLOPT_WRITEDATA, &ud); ret = curl_easy_perform (handle); if (ret != 0) { fprintf (stderr, "curl[%d] error %d\n", __LINE__, ret); exit (1); } curl_easy_cleanup (handle); #endif _response_info (&ud); v = _verify_response (&ud, signer_file); gnutls_global_deinit (); return v; } static void _response_info (const gnutls_datum_t * data) { gnutls_ocsp_resp_t resp; int ret; gnutls_datum buf; ret = gnutls_ocsp_resp_init (&resp); if (ret < 0) exit (1); ret = gnutls_ocsp_resp_import (resp, data); if (ret < 0) exit (1); ret = gnutls_ocsp_resp_print (resp, GNUTLS_OCSP_PRINT_FULL, &buf); if (ret != 0) exit (1); printf ("%.*s", buf.size, buf.data); gnutls_free (buf.data); gnutls_ocsp_resp_deinit (resp); } static gnutls_x509_crt_t load_cert (const char *cert_file) { gnutls_x509_crt_t crt; int ret; gnutls_datum_t data; size_t size; ret = gnutls_x509_crt_init (&crt); if (ret < 0) exit (1); data.data = (void *) read_binary_file (cert_file, &size); data.size = size; if (!data.data) { fprintf (stderr, "Cannot open file: %s\n", cert_file); exit (1); } ret = gnutls_x509_crt_import (crt, &data, GNUTLS_X509_FMT_PEM); free (data.data); if (ret < 0) { fprintf (stderr, "Cannot import certificate in %s: %s\n", cert_file, gnutls_strerror (ret)); exit (1); } return crt; } static void _generate_request (gnutls_datum_t * rdata, const char *cert_file, const char *issuer_file) { gnutls_ocsp_req_t req; int ret; gnutls_x509_crt_t issuer, cert; unsigned char noncebuf[23]; gnutls_datum_t nonce = { noncebuf, sizeof (noncebuf) }; ret = gnutls_ocsp_req_init (&req); if (ret < 0) exit (1); issuer = load_cert (issuer_file); cert = load_cert (cert_file); ret = gnutls_ocsp_req_add_cert (req, GNUTLS_DIG_SHA1, issuer, cert); if (ret < 0) exit (1); gnutls_x509_crt_deinit (issuer); gnutls_x509_crt_deinit (cert); ret = gnutls_rnd (GNUTLS_RND_RANDOM, nonce.data, nonce.size); if (ret < 0) exit (1); ret = gnutls_ocsp_req_set_nonce (req, 0, &nonce); if (ret < 0) exit (1); ret = gnutls_ocsp_req_export (req, rdata); if (ret != 0) exit (1); gnutls_ocsp_req_deinit (req); return; } static int _verify_response (gnutls_datum_t * data, const char *signer_file) { gnutls_ocsp_resp_t resp; int ret; size_t size; gnutls_x509_crt_t signer; unsigned verify; gnutls_datum_t dat; ret = gnutls_ocsp_resp_init (&resp); if (ret < 0) exit (1); ret = gnutls_ocsp_resp_import (resp, data); if (ret < 0) exit (1); ret = gnutls_x509_crt_init (&signer); if (ret < 0) exit (1); dat.data = (void *) read_binary_file (signer_file, &size); if (dat.data == NULL) exit (1); dat.size = size; ret = gnutls_x509_crt_import (signer, &dat, GNUTLS_X509_FMT_PEM); free (dat.data); if (ret < 0) exit (1); ret = gnutls_ocsp_resp_verify_direct (resp, signer, &verify, 0); if (ret < 0) exit (1); printf ("Verifying OCSP Response: "); if (verify == 0) printf ("Verification success!\n"); else printf ("Verification error!\n"); if (verify & GNUTLS_OCSP_VERIFY_SIGNER_NOT_FOUND) printf ("Signer cert not found\n"); if (verify & GNUTLS_OCSP_VERIFY_SIGNER_KEYUSAGE_ERROR) printf ("Signer cert keyusage error\n"); if (verify & GNUTLS_OCSP_VERIFY_UNTRUSTED_SIGNER) printf ("Signer cert is not trusted\n"); if (verify & GNUTLS_OCSP_VERIFY_INSECURE_ALGORITHM) printf ("Insecure algorithm\n"); if (verify & GNUTLS_OCSP_VERIFY_SIGNATURE_FAILURE) printf ("Signature failure\n"); if (verify & GNUTLS_OCSP_VERIFY_CERT_NOT_ACTIVATED) printf ("Signer cert not yet activated\n"); if (verify & GNUTLS_OCSP_VERIFY_CERT_EXPIRED) printf ("Signer cert expired\n"); gnutls_ocsp_resp_deinit (resp); return verify; } size_t get_data (void *buffer, size_t size, size_t nmemb, void *userp) { gnutls_datum_t *ud = userp; size *= nmemb; ud->data = realloc (ud->data, size + ud->size); if (ud->data == NULL) { fprintf (stderr, "Not enough memory for the request\n"); exit (1); } memcpy (&ud->data[ud->size], buffer, size); ud->size += size; return size; }
Previous: OCSP example, Up: GnuTLS application examples [Contents][Index]
• Checking for an alert: | ||
• X.509 certificate parsing example: | ||
• Listing the ciphersuites in a priority string: |
Next: X.509 certificate parsing example, Up: Miscellaneous examples [Contents][Index]
This is a function that checks if an alert has been received in the current session.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <gnutls/gnutls.h> #include "examples.h" /* This function will check whether the given return code from * a gnutls function (recv/send), is an alert, and will print * that alert. */ void check_alert (gnutls_session_t session, int ret) { int last_alert; if (ret == GNUTLS_E_WARNING_ALERT_RECEIVED || ret == GNUTLS_E_FATAL_ALERT_RECEIVED) { last_alert = gnutls_alert_get (session); /* The check for renegotiation is only useful if we are * a server, and we had requested a rehandshake. */ if (last_alert == GNUTLS_A_NO_RENEGOTIATION && ret == GNUTLS_E_WARNING_ALERT_RECEIVED) printf ("* Received NO_RENEGOTIATION alert. " "Client Does not support renegotiation.\n"); else printf ("* Received alert '%d': %s.\n", last_alert, gnutls_alert_get_name (last_alert)); } }
Next: Listing the ciphersuites in a priority string, Previous: Checking for an alert, Up: Miscellaneous examples [Contents][Index]
To demonstrate the X.509 parsing capabilities an example program is listed below. That program reads the peer’s certificate, and prints information about it.
/* This example code is placed in the public domain. */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <stdio.h> #include <stdlib.h> #include <gnutls/gnutls.h> #include <gnutls/x509.h> #include "examples.h" static const char * bin2hex (const void *bin, size_t bin_size) { static char printable[110]; const unsigned char *_bin = bin; char *print; size_t i; if (bin_size > 50) bin_size = 50; print = printable; for (i = 0; i < bin_size; i++) { sprintf (print, "%.2x ", _bin[i]); print += 2; } return printable; } /* This function will print information about this session's peer * certificate. */ void print_x509_certificate_info (gnutls_session_t session) { char serial[40]; char dn[256]; size_t size; unsigned int algo, bits; time_t expiration_time, activation_time; const gnutls_datum_t *cert_list; unsigned int cert_list_size = 0; gnutls_x509_crt_t cert; gnutls_datum_t cinfo; /* This function only works for X.509 certificates. */ if (gnutls_certificate_type_get (session) != GNUTLS_CRT_X509) return; cert_list = gnutls_certificate_get_peers (session, &cert_list_size); printf ("Peer provided %d certificates.\n", cert_list_size); if (cert_list_size > 0) { int ret; /* we only print information about the first certificate. */ gnutls_x509_crt_init (&cert); gnutls_x509_crt_import (cert, &cert_list[0], GNUTLS_X509_FMT_DER); printf ("Certificate info:\n"); /* This is the preferred way of printing short information about a certificate. */ ret = gnutls_x509_crt_print (cert, GNUTLS_CRT_PRINT_ONELINE, &cinfo); if (ret == 0) { printf ("\t%s\n", cinfo.data); gnutls_free (cinfo.data); } /* If you want to extract fields manually for some other reason, below are popular example calls. */ expiration_time = gnutls_x509_crt_get_expiration_time (cert); activation_time = gnutls_x509_crt_get_activation_time (cert); printf ("\tCertificate is valid since: %s", ctime (&activation_time)); printf ("\tCertificate expires: %s", ctime (&expiration_time)); /* Print the serial number of the certificate. */ size = sizeof (serial); gnutls_x509_crt_get_serial (cert, serial, &size); printf ("\tCertificate serial number: %s\n", bin2hex (serial, size)); /* Extract some of the public key algorithm's parameters */ algo = gnutls_x509_crt_get_pk_algorithm (cert, &bits); printf ("Certificate public key: %s", gnutls_pk_algorithm_get_name (algo)); /* Print the version of the X.509 * certificate. */ printf ("\tCertificate version: #%d\n", gnutls_x509_crt_get_version (cert)); size = sizeof (dn); gnutls_x509_crt_get_dn (cert, dn, &size); printf ("\tDN: %s\n", dn); size = sizeof (dn); gnutls_x509_crt_get_issuer_dn (cert, dn, &size); printf ("\tIssuer's DN: %s\n", dn); gnutls_x509_crt_deinit (cert); } }
Previous: X.509 certificate parsing example, Up: Miscellaneous examples [Contents][Index]
This is a small program to list the enabled ciphersuites by a priority string.
/* This example code is placed in the public domain. */ #include <config.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <gnutls/gnutls.h> static void print_cipher_suite_list (const char* priorities) { size_t i; int ret; unsigned int idx; const char *name; const char *err; unsigned char id[2]; gnutls_protocol_t version; gnutls_priority_t pcache; if (priorities != NULL) { printf ("Cipher suites for %s\n", priorities); ret = gnutls_priority_init(&pcache, priorities, &err); if (ret < 0) { fprintf (stderr, "Syntax error at: %s\n", err); exit(1); } for (i=0;;i++) { ret = gnutls_priority_get_cipher_suite_index(pcache, i, &idx); if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) break; if (ret == GNUTLS_E_UNKNOWN_CIPHER_SUITE) continue; name = gnutls_cipher_suite_info(idx, id, NULL, NULL, NULL, &version); if (name != NULL) printf ("%-50s\t0x%02x, 0x%02x\t%s\n", name, (unsigned char) id[0], (unsigned char) id[1], gnutls_protocol_get_name (version)); } return; } } int main(int argc, char** argv) { if (argc > 1) print_cipher_suite_list (argv[1]); }
Next: Internal architecture of GnuTLS, Previous: GnuTLS application examples, Up: Top [Contents][Index]
Included with GnuTLS are also a few command line tools that let you use the library for common tasks without writing an application. The applications are discussed in this chapter.
• gnutls-cli Invocation: | Invoking gnutls-cli | |
• gnutls-serv Invocation: | Invoking gnutls-serv | |
• gnutls-cli-debug Invocation: | Invoking gnutls-cli-debug |
Next: gnutls-serv Invocation, Up: Other included programs [Contents][Index]
Simple client program to set up a TLS connection to some other computer. It sets up a TLS connection and forwards data from the standard input to the secured socket and vice versa.
This section was generated by AutoGen,
using the agtexi-cmd
template and the option descriptions for the gnutls-cli
program.
This software is released under the GNU General Public License, version 3 or later.
This is the automatically generated usage text for gnutls-cli.
The text printed is the same whether selected with the help
option
(--help) or the more-help
option (--more-help). more-help
will print
the usage text by passing it through a pager program.
more-help
is disabled on platforms without a working
fork(2)
function. The PAGER
environment variable is
used to select the program, defaulting to more. Both will exit
with a status code of 0.
gnutls-cli - GnuTLS client Usage: gnutls-cli [ -<flag> [<val>] | --<name>[{=| }<val>] ]... [hostname] -d, --debug=num Enable debugging. - it must be in the range: 0 to 9999 -V, --verbose More verbose output - may appear multiple times --tofu Enable trust on first use authentication - disabled as '--no-tofu' --dane Enable DANE certificate verification (DNSSEC) - disabled as '--no-dane' --local-dns Use the local DNS server for DNSSEC resolving. - disabled as '--no-local-dns' --ca-verification Disable CA certificate verification - disabled as '--no-ca-verification' - enabled by default --ocsp Enable OCSP certificate verification - disabled as '--no-ocsp' -r, --resume Establish a session and resume -e, --rehandshake Establish a session and rehandshake -s, --starttls Connect, establish a plain session and start TLS. -u, --udp Use DTLS (datagram TLS) over UDP --mtu=num Set MTU for datagram TLS - it must be in the range: 0 to 17000 --crlf Send CR LF instead of LF --x509fmtder Use DER format for certificates to read from -f, --fingerprint Send the openpgp fingerprint, instead of the key --print-cert Print peer's certificate in PEM format --dh-bits=num The minimum number of bits allowed for DH --priority=str Priorities string --x509cafile=str Certificate file or PKCS #11 URL to use --x509crlfile=file CRL file to use - file must pre-exist --pgpkeyfile=file PGP Key file to use - file must pre-exist --pgpkeyring=file PGP Key ring file to use - file must pre-exist --pgpcertfile=file PGP Public Key (certificate) file to use - file must pre-exist --x509keyfile=str X.509 key file or PKCS #11 URL to use --x509certfile=str X.509 Certificate file or PKCS #11 URL to use --pgpsubkey=str PGP subkey to use (hex or auto) --srpusername=str SRP username to use --srppasswd=str SRP password to use --pskusername=str PSK username to use --pskkey=str PSK key (in hex) to use -p, --port=str The port or service to connect to --insecure Don't abort program if server certificate can't be validated --ranges Use length-hiding padding to prevent traffic analysis --benchmark-ciphers Benchmark individual ciphers --benchmark-soft-ciphers Benchmark individual software ciphers (no hw acceleration) --benchmark-tls-kx Benchmark TLS key exchange methods --benchmark-tls-ciphers Benchmark TLS ciphers -l, --list Print a list of the supported algorithms and modes --noticket Don't allow session tickets --srtp-profiles=str Offer SRTP profiles --alpn=str Application layer protocol - may appear multiple times -b, --heartbeat Activate heartbeat support --recordsize=num The maximum record size to advertize - it must be in the range: 0 to 4096 --disable-sni Do not send a Server Name Indication (SNI) --disable-extensions Disable all the TLS extensions -v, --version[=arg] output version information and exit -h, --help display extended usage information and exit -!, --more-help extended usage information passed thru pager Options are specified by doubled hyphens and their name or by a single hyphen and the flag character. Operands and options may be intermixed. They will be reordered. Simple client program to set up a TLS connection to some other computer. It sets up a TLS connection and forwards data from the standard input to the secured socket and vice versa. Please send bug reports to: <bug-gnutls@gnu.org>
This is the “enable debugging.” option. This option takes an argument number. Specifies the debug level.
This is the “enable trust on first use authentication” option. This option will, in addition to certificate authentication, perform authentication based on previously seen public keys, a model similar to SSH authentication.
This is the “enable ocsp certificate verification” option. This option will enable verification of the peer’s certificate using ocsp
This is the “establish a session and resume” option. Connect, establish a session, reconnect and resume.
This is the “establish a session and rehandshake” option. Connect, establish a session and rehandshake immediately.
This is the “connect, establish a plain session and start tls.” option. The TLS session will be initiated when EOF or a SIGALRM is received.
This is the “priorities string” option. This option takes an argument string. TLS algorithms and protocols to enable. You can use predefined sets of ciphersuites such as PERFORMANCE, NORMAL, SECURE128, SECURE256.
Check the GnuTLS manual on section “Priority strings” for more information on allowed keywords
This is the “print a list of the supported algorithms and modes” option. Print a list of the supported algorithms and modes. If a priority string is given then only the enabled ciphersuites are shown.
One of the following exit values will be returned:
Successful program execution.
The operation failed or the command syntax was not valid.
gnutls-cli-debug(1), gnutls-serv(1)
To connect to a server using PSK authentication, you need to enable the choice of PSK by using a cipher priority parameter such as in the example below.
$ ./gnutls-cli -p 5556 localhost --pskusername psk_identity \ --pskkey 88f3824b3e5659f52d00e959bacab954b6540344 \ --priority NORMAL:-KX-ALL:+ECDHE-PSK:+DHE-PSK:+PSK Resolving 'localhost'... Connecting to '127.0.0.1:5556'... - PSK authentication. - Version: TLS1.1 - Key Exchange: PSK - Cipher: AES-128-CBC - MAC: SHA1 - Compression: NULL - Handshake was completed - Simple Client Mode:
By keeping the –pskusername parameter and removing the –pskkey parameter, it will query only for the password during the handshake.
To list the ciphersuites in a priority string:
$ ./gnutls-cli --priority SECURE192 -l Cipher suites for SECURE192 TLS_ECDHE_ECDSA_AES_256_CBC_SHA384 0xc0, 0x24 TLS1.2 TLS_ECDHE_ECDSA_AES_256_GCM_SHA384 0xc0, 0x2e TLS1.2 TLS_ECDHE_RSA_AES_256_GCM_SHA384 0xc0, 0x30 TLS1.2 TLS_DHE_RSA_AES_256_CBC_SHA256 0x00, 0x6b TLS1.2 TLS_DHE_DSS_AES_256_CBC_SHA256 0x00, 0x6a TLS1.2 TLS_RSA_AES_256_CBC_SHA256 0x00, 0x3d TLS1.2 Certificate types: CTYPE-X.509 Protocols: VERS-TLS1.2, VERS-TLS1.1, VERS-TLS1.0, VERS-SSL3.0, VERS-DTLS1.0 Compression: COMP-NULL Elliptic curves: CURVE-SECP384R1, CURVE-SECP521R1 PK-signatures: SIGN-RSA-SHA384, SIGN-ECDSA-SHA384, SIGN-RSA-SHA512, SIGN-ECDSA-SHA512
Next: gnutls-cli-debug Invocation, Previous: gnutls-cli Invocation, Up: Other included programs [Contents][Index]
Server program that listens to incoming TLS connections.
This section was generated by AutoGen,
using the agtexi-cmd
template and the option descriptions for the gnutls-serv
program.
This software is released under the GNU General Public License, version 3 or later.
This is the automatically generated usage text for gnutls-serv.
The text printed is the same whether selected with the help
option
(--help) or the more-help
option (--more-help). more-help
will print
the usage text by passing it through a pager program.
more-help
is disabled on platforms without a working
fork(2)
function. The PAGER
environment variable is
used to select the program, defaulting to more. Both will exit
with a status code of 0.
gnutls-serv - GnuTLS server Usage: gnutls-serv [ -<flag> [<val>] | --<name>[{=| }<val>] ]... -d, --debug=num Enable debugging. - it must be in the range: 0 to 9999 --noticket Don't accept session tickets -g, --generate Generate Diffie-Hellman and RSA-export parameters -q, --quiet Suppress some messages --nodb Do not use a resumption database --http Act as an HTTP server --echo Act as an Echo server -u, --udp Use DTLS (datagram TLS) over UDP --mtu=num Set MTU for datagram TLS - it must be in the range: 0 to 17000 --srtp-profiles=str Offer SRTP profiles -a, --disable-client-cert Do not request a client certificate -r, --require-client-cert Require a client certificate -b, --heartbeat Activate heartbeat support --x509fmtder Use DER format for certificates to read from --priority=str Priorities string --dhparams=file DH params file to use - file must pre-exist --x509cafile=str Certificate file or PKCS #11 URL to use --x509crlfile=file CRL file to use - file must pre-exist --pgpkeyfile=file PGP Key file to use - file must pre-exist --pgpkeyring=file PGP Key ring file to use - file must pre-exist --pgpcertfile=file PGP Public Key (certificate) file to use - file must pre-exist --x509keyfile=str X.509 key file or PKCS #11 URL to use --x509certfile=str X.509 Certificate file or PKCS #11 URL to use --x509dsakeyfile=str Alternative X.509 key file or PKCS #11 URL to use --x509dsacertfile=str Alternative X.509 Certificate file or PKCS #11 URL to use --x509ecckeyfile=str Alternative X.509 key file or PKCS #11 URL to use --x509ecccertfile=str Alternative X.509 Certificate file or PKCS #11 URL to use --pgpsubkey=str PGP subkey to use (hex or auto) --srppasswd=file SRP password file to use - file must pre-exist --srppasswdconf=file SRP password configuration file to use - file must pre-exist --pskpasswd=file PSK password file to use - file must pre-exist --pskhint=str PSK identity hint to use --ocsp-response=file The OCSP response to send to client - file must pre-exist -p, --port=num The port to connect to -l, --list Print a list of the supported algorithms and modes -v, --version[=arg] output version information and exit -h, --help display extended usage information and exit -!, --more-help extended usage information passed thru pager Options are specified by doubled hyphens and their name or by a single hyphen and the flag character. Server program that listens to incoming TLS connections. Please send bug reports to: <bug-gnutls@gnu.org>
This is the “enable debugging.” option. This option takes an argument number. Specifies the debug level.
This is the “priorities string” option. This option takes an argument string. TLS algorithms and protocols to enable. You can use predefined sets of ciphersuites such as PERFORMANCE, NORMAL, SECURE128, SECURE256.
Check the GnuTLS manual on section “Priority strings” for more information on allowed keywords
This is the “print a list of the supported algorithms and modes” option. Print a list of the supported algorithms and modes. If a priority string is given then only the enabled ciphersuites are shown.
One of the following exit values will be returned:
Successful program execution.
The operation failed or the command syntax was not valid.
gnutls-cli-debug(1), gnutls-cli(1)
Running your own TLS server based on GnuTLS can be useful when
debugging clients and/or GnuTLS itself. This section describes how to
use gnutls-serv
as a simple HTTPS server.
The most basic server can be started as:
gnutls-serv --http
It will only support anonymous ciphersuites, which many TLS clients refuse to use.
The next step is to add support for X.509. First we generate a CA:
$ certtool --generate-privkey > x509-ca-key.pem $ echo 'cn = GnuTLS test CA' > ca.tmpl $ echo 'ca' >> ca.tmpl $ echo 'cert_signing_key' >> ca.tmpl $ certtool --generate-self-signed --load-privkey x509-ca-key.pem \ --template ca.tmpl --outfile x509-ca.pem ...
Then generate a server certificate. Remember to change the dns_name value to the name of your server host, or skip that command to avoid the field.
$ certtool --generate-privkey > x509-server-key.pem $ echo 'organization = GnuTLS test server' > server.tmpl $ echo 'cn = test.gnutls.org' >> server.tmpl $ echo 'tls_www_server' >> server.tmpl $ echo 'encryption_key' >> server.tmpl $ echo 'signing_key' >> server.tmpl $ echo 'dns_name = test.gnutls.org' >> server.tmpl $ certtool --generate-certificate --load-privkey x509-server-key.pem \ --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem \ --template server.tmpl --outfile x509-server.pem ...
For use in the client, you may want to generate a client certificate as well.
$ certtool --generate-privkey > x509-client-key.pem $ echo 'cn = GnuTLS test client' > client.tmpl $ echo 'tls_www_client' >> client.tmpl $ echo 'encryption_key' >> client.tmpl $ echo 'signing_key' >> client.tmpl $ certtool --generate-certificate --load-privkey x509-client-key.pem \ --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem \ --template client.tmpl --outfile x509-client.pem ...
To be able to import the client key/certificate into some applications, you will need to convert them into a PKCS#12 structure. This also encrypts the security sensitive key with a password.
$ certtool --to-p12 --load-ca-certificate x509-ca.pem \ --load-privkey x509-client-key.pem --load-certificate x509-client.pem \ --outder --outfile x509-client.p12
For icing, we’ll create a proxy certificate for the client too.
$ certtool --generate-privkey > x509-proxy-key.pem $ echo 'cn = GnuTLS test client proxy' > proxy.tmpl $ certtool --generate-proxy --load-privkey x509-proxy-key.pem \ --load-ca-certificate x509-client.pem --load-ca-privkey x509-client-key.pem \ --load-certificate x509-client.pem --template proxy.tmpl \ --outfile x509-proxy.pem ...
Then start the server again:
$ gnutls-serv --http \ --x509cafile x509-ca.pem \ --x509keyfile x509-server-key.pem \ --x509certfile x509-server.pem
Try connecting to the server using your web browser. Note that the server listens to port 5556 by default.
While you are at it, to allow connections using DSA, you can also create a DSA key and certificate for the server. These credentials will be used in the final example below.
$ certtool --generate-privkey --dsa > x509-server-key-dsa.pem $ certtool --generate-certificate --load-privkey x509-server-key-dsa.pem \ --load-ca-certificate x509-ca.pem --load-ca-privkey x509-ca-key.pem \ --template server.tmpl --outfile x509-server-dsa.pem ...
The next step is to create OpenPGP credentials for the server.
gpg --gen-key ...enter whatever details you want, use 'test.gnutls.org' as name...
Make a note of the OpenPGP key identifier of the newly generated key,
here it was 5D1D14D8
. You will need to export the key for
GnuTLS to be able to use it.
gpg -a --export 5D1D14D8 > openpgp-server.txt gpg --export 5D1D14D8 > openpgp-server.bin gpg --export-secret-keys 5D1D14D8 > openpgp-server-key.bin gpg -a --export-secret-keys 5D1D14D8 > openpgp-server-key.txt
Let’s start the server with support for OpenPGP credentials:
gnutls-serv --http \ --pgpkeyfile openpgp-server-key.txt \ --pgpcertfile openpgp-server.txt
The next step is to add support for SRP authentication. This requires
an SRP password file created with srptool
.
To start the server with SRP support:
gnutls-serv --http \ --srppasswdconf srp-tpasswd.conf \ --srppasswd srp-passwd.txt
Let’s also start a server with support for PSK. This would require
a password file created with psktool
.
gnutls-serv --http \ --pskpasswd psk-passwd.txt
Finally, we start the server with all the earlier parameters and you get this command:
gnutls-serv --http \ --x509cafile x509-ca.pem \ --x509keyfile x509-server-key.pem \ --x509certfile x509-server.pem \ --x509dsakeyfile x509-server-key-dsa.pem \ --x509dsacertfile x509-server-dsa.pem \ --pgpkeyfile openpgp-server-key.txt \ --pgpcertfile openpgp-server.txt \ --srppasswdconf srp-tpasswd.conf \ --srppasswd srp-passwd.txt \ --pskpasswd psk-passwd.txt
Previous: gnutls-serv Invocation, Up: Other included programs [Contents][Index]
TLS debug client. It sets up multiple TLS connections to a server and queries its capabilities. It was created to assist in debugging GnuTLS, but it might be useful to extract a TLS server’s capabilities. It connects to a TLS server, performs tests and print the server’s capabilities. If called with the ‘-v’ parameter more checks will be performed. Can be used to check for servers with special needs or bugs.
This section was generated by AutoGen,
using the agtexi-cmd
template and the option descriptions for the gnutls-cli-debug
program.
This software is released under the GNU General Public License, version 3 or later.
This is the automatically generated usage text for gnutls-cli-debug.
The text printed is the same whether selected with the help
option
(--help) or the more-help
option (--more-help). more-help
will print
the usage text by passing it through a pager program.
more-help
is disabled on platforms without a working
fork(2)
function. The PAGER
environment variable is
used to select the program, defaulting to more. Both will exit
with a status code of 0.
gnutls-cli-debug - GnuTLS debug client Usage: gnutls-cli-debug [ -<flag> [<val>] | --<name>[{=| }<val>] ]... -d, --debug=num Enable debugging. - it must be in the range: 0 to 9999 -V, --verbose More verbose output - may appear multiple times -p, --port=num The port to connect to - it must be in the range: 0 to 65536 -v, --version[=arg] output version information and exit -h, --help display extended usage information and exit -!, --more-help extended usage information passed thru pager Options are specified by doubled hyphens and their name or by a single hyphen and the flag character. Operands and options may be intermixed. They will be reordered. TLS debug client. It sets up multiple TLS connections to a server and queries its capabilities. It was created to assist in debugging GnuTLS, but it might be useful to extract a TLS server's capabilities. It connects to a TLS server, performs tests and print the server's capabilities. If called with the `-v' parameter more checks will be performed. Can be used to check for servers with special needs or bugs. Please send bug reports to: <bug-gnutls@gnu.org>
This is the “enable debugging.” option. This option takes an argument number. Specifies the debug level.
One of the following exit values will be returned:
Successful program execution.
The operation failed or the command syntax was not valid.
$ ../src/gnutls-cli-debug localhost Resolving 'localhost'... Connecting to '127.0.0.1:443'... Checking for SSL 3.0 support... yes Checking whether %COMPAT is required... no Checking for TLS 1.0 support... yes Checking for TLS 1.1 support... no Checking fallback from TLS 1.1 to... TLS 1.0 Checking for TLS 1.2 support... no Checking whether we need to disable TLS 1.0... N/A Checking for Safe renegotiation support... yes Checking for Safe renegotiation support (SCSV)... yes Checking for HTTPS server name... not checked Checking for version rollback bug in RSA PMS... no Checking for version rollback bug in Client Hello... no Checking whether the server ignores the RSA PMS version... no Checking whether the server can accept Hello Extensions... yes Checking whether the server can accept small records (512 bytes)... yes Checking whether the server can accept cipher suites not in SSL 3.0 spec... yes Checking whether the server can accept a bogus TLS record version in the client hello... yes Checking for certificate information... N/A Checking for trusted CAs... N/A Checking whether the server understands TLS closure alerts... partially Checking whether the server supports session resumption... yes Checking for export-grade ciphersuite support... no Checking RSA-export ciphersuite info... N/A Checking for anonymous authentication support... no Checking anonymous Diffie-Hellman group info... N/A Checking for ephemeral Diffie-Hellman support... no Checking ephemeral Diffie-Hellman group info... N/A Checking for ephemeral EC Diffie-Hellman support... yes Checking ephemeral EC Diffie-Hellman group info... Curve SECP256R1 Checking for AES-GCM cipher support... no Checking for AES-CBC cipher support... yes Checking for CAMELLIA cipher support... no Checking for 3DES-CBC cipher support... yes Checking for ARCFOUR 128 cipher support... yes Checking for ARCFOUR 40 cipher support... no Checking for MD5 MAC support... yes Checking for SHA1 MAC support... yes Checking for SHA256 MAC support... no Checking for ZLIB compression support... no Checking for max record size... no Checking for OpenPGP authentication support... no
Next: Upgrading from previous versions, Previous: Other included programs, Up: Top [Contents][Index]
This chapter is to give a brief description of the way GnuTLS works. The focus is to give an idea to potential developers and those who want to know what happens inside the black box.
• The TLS Protocol: | ||
• TLS Handshake Protocol: | ||
• TLS Authentication Methods: | ||
• TLS Extension Handling: | ||
• Cryptographic Backend: |
Next: TLS Handshake Protocol, Up: Internal architecture of GnuTLS [Contents][Index]
The main use case for the TLS protocol is shown in Figure 10.1. A user of a library implementing the protocol expects no less than this functionality, i.e., to be able to set parameters such as the accepted security level, perform a negotiation with the peer and be able to exchange data.
Next: TLS Authentication Methods, Previous: The TLS Protocol, Up: Internal architecture of GnuTLS [Contents][Index]
The GnuTLS handshake protocol is implemented as a state machine that waits for input or returns immediately when the non-blocking transport layer functions are used. The main idea is shown in Figure 10.2.
Also the way the input is processed varies per ciphersuite. Several
implementations of the internal handlers are available and
gnutls_handshake only multiplexes the input to the appropriate
handler. For example a PSK ciphersuite has a different
implementation of the process_client_key_exchange
than a
certificate ciphersuite. We illustrate the idea in Figure 10.3.
Next: TLS Extension Handling, Previous: TLS Handshake Protocol, Up: Internal architecture of GnuTLS [Contents][Index]
In GnuTLS authentication methods can be implemented quite easily. Since the required changes to add a new authentication method affect only the handshake protocol, a simple interface is used. An authentication method needs to implement the functions shown below.
typedef struct { const char *name; int (*gnutls_generate_server_certificate) (gnutls_session_t, gnutls_buffer_st*); int (*gnutls_generate_client_certificate) (gnutls_session_t, gnutls_buffer_st*); int (*gnutls_generate_server_kx) (gnutls_session_t, gnutls_buffer_st*); int (*gnutls_generate_client_kx) (gnutls_session_t, gnutls_buffer_st*); int (*gnutls_generate_client_cert_vrfy) (gnutls_session_t, gnutls_buffer_st *); int (*gnutls_generate_server_certificate_request) (gnutls_session_t, gnutls_buffer_st *); int (*gnutls_process_server_certificate) (gnutls_session_t, opaque *, size_t); int (*gnutls_process_client_certificate) (gnutls_session_t, opaque *, size_t); int (*gnutls_process_server_kx) (gnutls_session_t, opaque *, size_t); int (*gnutls_process_client_kx) (gnutls_session_t, opaque *, size_t); int (*gnutls_process_client_cert_vrfy) (gnutls_session_t, opaque *, size_t); int (*gnutls_process_server_certificate_request) (gnutls_session_t, opaque *, size_t); } mod_auth_st;
Those functions are responsible for the
interpretation of the handshake protocol messages. It is common for such
functions to read data from one or more credentials_t
structures16 and write data,
such as certificates, usernames etc. to auth_info_t
structures.
Simple examples of existing authentication methods can be seen in
auth/psk.c
for PSK ciphersuites and auth/srp.c
for SRP
ciphersuites. After implementing these functions the structure holding
its pointers has to be registered in gnutls_algorithms.c
in the
_gnutls_kx_algorithms
structure.
Next: Cryptographic Backend, Previous: TLS Authentication Methods, Up: Internal architecture of GnuTLS [Contents][Index]
As with authentication methods, the TLS extensions handlers can be implemented using the interface shown below.
typedef int (*gnutls_ext_recv_func) (gnutls_session_t session, const unsigned char *data, size_t len); typedef int (*gnutls_ext_send_func) (gnutls_session_t session, gnutls_buffer_st *extdata);
Here there are two functions, one for receiving the extension data and one for sending. These functions have to check internally whether they operate in client or server side.
A simple example of an extension handler can be seen in
ext/srp.c
in GnuTLS’ source code. After implementing these functions,
together with the extension number they handle, they have to be registered
using _gnutls_ext_register
in
gnutls_extensions.c
typically within _gnutls_ext_init
.
Adding support for a new TLS extension is done from time to time, and
the process to do so is not difficult. Here are the steps you need to
follow if you wish to do this yourself. For sake of discussion, let’s
consider adding support for the hypothetical TLS extension
foobar
.
configure
option like --enable-foobar
or --disable-foobar
.This step is useful when the extension code is large and it might be desirable to disable the extension under some circumstances. Otherwise it can be safely skipped.
Whether to chose enable or disable depends on whether you intend to make the extension be enabled by default. Look at existing checks (i.e., SRP, authz) for how to model the code. For example:
AC_MSG_CHECKING([whether to disable foobar support]) AC_ARG_ENABLE(foobar, AS_HELP_STRING([--disable-foobar], [disable foobar support]), ac_enable_foobar=no) if test x$ac_enable_foobar != xno; then AC_MSG_RESULT(no) AC_DEFINE(ENABLE_FOOBAR, 1, [enable foobar]) else ac_full=0 AC_MSG_RESULT(yes) fi AM_CONDITIONAL(ENABLE_FOOBAR, test "$ac_enable_foobar" != "no")
These lines should go in lib/m4/hooks.m4
.
extensions_t
in gnutls_int.h
.A good name for the value would be GNUTLS_EXTENSION_FOOBAR. Check with http://www.iana.org/assignments/tls-extensiontype-values for allocated values. For experiments, you could pick a number but remember that some consider it a bad idea to deploy such modified version since it will lead to interoperability problems in the future when the IANA allocates that number to someone else, or when the foobar protocol is allocated another number.
_gnutls_extensions
in gnutls_extensions.c
.A typical entry would be:
int ret; #if ENABLE_FOOBAR ret = _gnutls_ext_register (&foobar_ext); if (ret != GNUTLS_E_SUCCESS) return ret; #endif
Most likely you’ll need to add an #include "ext/foobar.h"
, that
will contain something like
like:
extension_entry_st foobar_ext = { .name = "FOOBAR", .type = GNUTLS_EXTENSION_FOOBAR, .parse_type = GNUTLS_EXT_TLS, .recv_func = _foobar_recv_params, .send_func = _foobar_send_params, .pack_func = _foobar_pack, .unpack_func = _foobar_unpack, .deinit_func = NULL }
The GNUTLS_EXTENSION_FOOBAR is the integer value you added to
gnutls_int.h
earlier. In this structure you specify the
functions to read the extension from the hello message, the function
to send the reply to, and two more functions to pack and unpack from
stored session data (e.g. when resumming a session). The deinit
function
will be called to deinitialize the extension’s private parameters, if any.
Note that the conditional ENABLE_FOOBAR
definition should only be
used if step 1 with the configure
options has taken place.
The functions you are responsible to add are those mentioned in the
previous step. They should be added in a file such as ext/foobar.c
and headers should be placed in ext/foobar.h
.
As a starter, you could add this:
int _foobar_recv_params (gnutls_session_t session, const opaque * data, size_t data_size) { return 0; } int _foobar_send_params (gnutls_session_t session, gnutls_buffer_st* data) { return 0; } int _foobar_pack (extension_priv_data_t epriv, gnutls_buffer_st * ps) { /* Append the extension's internal state to buffer */ return 0; } int _foobar_unpack (gnutls_buffer_st * ps, extension_priv_data_t * epriv) { /* Read the internal state from buffer */ return 0; }
The _foobar_recv_params
function is responsible for
parsing incoming extension data (both in the client and server).
The _foobar_send_params
function is responsible for
sending extension data (both in the client and server).
If you receive length fields that don’t match, return
GNUTLS_E_UNEXPECTED_PACKET_LENGTH
. If you receive invalid
data, return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER
. You can use
other error codes from the list in Error codes. Return 0 on success.
An extension typically stores private information in the session
data for later usage. That can be done using the functions
_gnutls_ext_set_session_data
and
_gnutls_ext_get_session_data
. You can check simple examples
at ext/max_record.c
and ext/server_name.c
extensions.
That private information can be saved and restored across session
resumption if the following functions are set:
The _foobar_pack
function is responsible for packing
internal extension data to save them in the session resumption storage.
The _foobar_unpack
function is responsible for
restoring session data from the session resumption storage.
Recall that both the client and server, send and receive parameters, and your code most likely will need to do different things depending on which mode it is in. It may be useful to make this distinction explicit in the code. Thus, for example, a better template than above would be:
int _gnutls_foobar_recv_params (gnutls_session_t session, const opaque * data, size_t data_size) { if (session->security_parameters.entity == GNUTLS_CLIENT) return foobar_recv_client (session, data, data_size); else return foobar_recv_server (session, data, data_size); } int _gnutls_foobar_send_params (gnutls_session_t session, gnutls_buffer_st * data) { if (session->security_parameters.entity == GNUTLS_CLIENT) return foobar_send_client (session, data); else return foobar_send_server (session, data); }
The functions used would be declared as static
functions, of
the appropriate prototype, in the same file.
When adding the files, you’ll need to add them to ext/Makefile.am
as well, for example:
if ENABLE_FOOBAR libgnutls_ext_la_SOURCES += ext/foobar.c ext/foobar.h endif
It might be desirable to allow users of the extension to
request use of the extension, or set extension specific data.
This can be implemented by adding extension specific function calls
that can be added to includes/gnutls/gnutls.h
,
as long as the LGPLv3+ applies.
The implementation of the function should lie in the ext/foobar.c
file.
To make the API available in the shared library you need to add the
symbol in lib/libgnutls.map
, so that the symbol
is exported properly.
When writing GTK-DOC style documentation for your new APIs, don’t
forget to add Since:
tags to indicate the GnuTLS version the
API was introduced in.
TLS handshake extensions allow to send so called supplemental data handshake messages [RFC4680]. This short section explains how to implement a supplemental data handshake message for a given TLS extension.
First of all, modify your extension foobar
in the way, the that
flags
session->security_parameters.do_send_supplemental
and
session->security_parameters.do_recv_supplemental
are set:
int _gnutls_foobar_recv_params (gnutls_session_t session, const opaque * data, size_t _data_size) { ... session->security_parameters.do_recv_supplemental=1; ... } int _gnutls_foobar_send_params (gnutls_session_t session, gnutls_buffer_st *extdata) { ... session->security_parameters.do_send_supplemental=1; ... }
Furthermore add the functions _foobar_supp_recv_params
and _foobar_supp_send_params
to _foobar.h
and
_foobar.c
. The following example code shows how to send a
“Hello World” string in the supplemental data handshake message:
int _foobar_supp_recv_params(gnutls_session_t session, const opaque *data, size_t _data_size) { uint8_t len = _data_size; unsigned char *msg; msg = gnutls_malloc(len); if (msg == NULL) return GNUTLS_E_MEMORY_ERROR; memcpy(msg, data, len); msg[len]='\0'; /* do something with msg */ gnutls_free(msg); return len; } int _foobar_supp_send_params(gnutls_session_t session, gnutls_buffer_st *buf) { unsigned char *msg = "hello world"; int len = strlen(msg); _gnutls_buffer_append_data_prefix(buf, 8, msg, len); return len; }
Afterwards, add the new supplemental data handshake message to
lib/gnutls_supplemental.c
by adding a new entry to the
_gnutls_supplemental[]
structure:
gnutls_supplemental_entry _gnutls_supplemental[] = { {"foobar", GNUTLS_SUPPLEMENTAL_FOOBAR_DATA, _foobar_supp_recv_params, _foobar_supp_send_params}, {0, 0, 0, 0} };
You have to include your foobar.h
header file as well:
#include "foobar.h"
Lastly, add the new supplemental data type to
lib/includes/gnutls/gnutls.h
:
typedef enum { GNUTLS_SUPPLEMENTAL_USER_MAPPING_DATA = 0, GNUTLS_SUPPLEMENTAL_FOOBAR_DATA = 1 } gnutls_supplemental_data_format_type_t;
Previous: TLS Extension Handling, Up: Internal architecture of GnuTLS [Contents][Index]
Today most new processors, either for embedded or desktop systems include either instructions intended to speed up cryptographic operations, or a co-processor with cryptographic capabilities. Taking advantage of those is a challenging task for every cryptographic application or library. Unfortunately the cryptographic library that GnuTLS is based on takes no advantage of these capabilities. For this reason GnuTLS handles this internally by following a layered approach to accessing cryptographic operations as in Figure 10.4.
The TLS layer uses a cryptographic provider layer, that will in turn either
use the default crypto provider – a software crypto library, or use an external
crypto provider, if available in the local system. The reason of handling
the external cryptographic provider in GnuTLS and not delegating it to
the cryptographic libraries, is that none of the supported cryptographic
libraries support /dev/crypto
or CPU-optimized cryptography in
an efficient way.
The Cryptographic library layer, currently supports only libnettle. Older versions of GnuTLS used to support libgcrypt, but it was switched with nettle mainly for performance reasons17 and secondary because it is a simpler library to use. In the future other cryptographic libraries might be supported as well.
Systems that include a cryptographic co-processor, typically come with
kernel drivers to utilize the operations from software. For this reason
GnuTLS provides a layer where each individual algorithm used can be replaced
by another implementation, i.e., the one provided by the driver. The
FreeBSD, OpenBSD and Linux kernels18 include already
a number of hardware assisted implementations, and also provide an interface
to access them, called /dev/crypto
.
GnuTLS will take advantage of this interface if compiled with special
options. That is because in most systems where hardware-assisted
cryptographic operations are not available, using this interface might
actually harm performance.
In systems that include cryptographic instructions with the CPU’s
instructions set, using the kernel interface will introduce an
unneeded layer. For this reason GnuTLS includes such optimizations
found in popular processors such as the AES-NI or VIA PADLOCK instruction sets.
This is achieved using a mechanism that detects CPU capabilities and
overrides parts of crypto back-end at runtime.
The next section discusses the registration of a detected algorithm
optimization. For more information please consult the GnuTLS
source code in lib/accelerated/
.
When an optimized implementation of a single algorithm is available,
say a hardware assisted version of AES-CBC then the
following (internal) functions, from crypto-backend.h
, can
be used to register those algorithms.
gnutls_crypto_single_cipher_register
:
To register a cipher algorithm.
gnutls_crypto_single_digest_register
:
To register a hash (digest) or MAC algorithm.
Those registration functions will only replace the specified algorithm and leave the rest of subsystem intact.
In some systems, that might contain a broad acceleration engine, it might be desirable to override big parts of the cryptographic back-end, or even all of them. The following functions are provided for this reason.
gnutls_crypto_cipher_register
:
To override the cryptographic algorithms back-end.
gnutls_crypto_digest_register
:
To override the digest algorithms back-end.
gnutls_crypto_rnd_register
:
To override the random number generator back-end.
gnutls_crypto_bigint_register
:
To override the big number number operations back-end.
gnutls_crypto_pk_register
:
To override the public key encryption back-end. This is tied to the
big number operations so either none or both of them should be overriden.
Next: Support, Previous: Internal architecture of GnuTLS, Up: Top [Contents][Index]
The GnuTLS library typically maintains binary and source code compatibility across versions. The releases that have the major version increased break binary compatibility but source compatibility is provided. This section lists exceptional cases where changes to existing code are required due to library changes.
GnuTLS 2.12.x is binary compatible with previous versions but changes the
semantics of gnutls_transport_set_lowat
, which might cause breakage
in applications that relied on its default value be 1. Two fixes
are proposed:
gnutls_transport_set_lowat (session, 1);
after gnutls_init.
select
to check for gnutls pending data, the
function gnutls_record_check_pending has to be used to achieve the same
functionality as described in Asynchronous operation.
GnuTLS 3.0.x is source compatible with previous versions except for the functions listed below.
Old function | Replacement |
---|---|
gnutls_transport_set_lowat | To replace its functionality the function gnutls_record_check_pending has to be used, as described in Asynchronous operation |
gnutls_session_get_server_random ,
gnutls_session_get_client_random | They are replaced by the safer function gnutls_session_get_random |
gnutls_session_get_master_secret | Replaced by the keying material exporters discussed in Keying Material Exporters |
gnutls_transport_set_global_errno | Replaced by using the system’s errno fascility or gnutls_transport_set_errno. |
gnutls_x509_privkey_verify_data | Replaced by gnutls_pubkey_verify_data. |
gnutls_certificate_verify_peers | Replaced by gnutls_certificate_verify_peers2. |
gnutls_psk_netconf_derive_key | Removed. The key derivation function was never standardized. |
gnutls_session_set_finished_function | Removed. |
gnutls_ext_register | Removed. Extension registration API is now internal to allow easier changes in the API. |
gnutls_certificate_get_x509_crls , gnutls_certificate_get_x509_cas | Removed to allow updating the internal structures. Replaced by gnutls_certificate_get_issuer. |
gnutls_certificate_get_openpgp_keyring | Removed. |
gnutls_ia_* | Removed. The inner application extensions were completely removed (they failed to be standardized). |
Next: Error codes, Previous: Upgrading from previous versions, Up: Top [Contents][Index]
• Getting help: | ||
• Commercial Support: | ||
• Bug Reports: | ||
• Contributing: |
Next: Commercial Support, Up: Support [Contents][Index]
A mailing list where users may help each other exists, and you can reach it by sending e-mail to help-gnutls@gnu.org. Archives of the mailing list discussions, and an interface to manage subscriptions, is available through the World Wide Web at http://lists.gnu.org/mailman/listinfo/help-gnutls.
A mailing list for developers are also available, see http://www.gnu.org/software/gnutls/lists.html. Bug reports should be sent to bug-gnutls@gnu.org, see Bug Reports.
Next: Bug Reports, Previous: Getting help, Up: Support [Contents][Index]
Commercial support is available for users of GnuTLS. The kind of support that can be purchased may include:
If you are interested, please write to:
Simon Josefsson Datakonsult Hagagatan 24 113 47 Stockholm Sweden E-mail: simon@josefsson.org
If your company provides support related to GnuTLS and would like to be mentioned here, contact the authors.
Next: Contributing, Previous: Commercial Support, Up: Support [Contents][Index]
If you think you have found a bug in GnuTLS, please investigate it and report it.
Please make an effort to produce a self-contained report, with something definite that can be tested or debugged. Vague queries or piecemeal messages are difficult to act on and don’t help the development effort.
If your bug report is good, we will do our best to help you to get a corrected version of the software; if the bug report is poor, we won’t do anything about it (apart from asking you to send better bug reports).
If you think something in this manual is unclear, or downright incorrect, or if the language needs to be improved, please also send a note.
Send your bug report to:
Previous: Bug Reports, Up: Support [Contents][Index]
If you want to submit a patch for inclusion – from solving a typo you discovered, up to adding support for a new feature – you should submit it as a bug report, using the process in Bug Reports. There are some things that you can do to increase the chances for it to be included in the official package.
Unless your patch is very small (say, under 10 lines) we require that you assign the copyright of your work to the Free Software Foundation. This is to protect the freedom of the project. If you have not already signed papers, we will send you the necessary information when you submit your contribution.
For contributions that doesn’t consist of actual programming code, the only guidelines are common sense. For code contributions, a number of style guides will help you:
If you normally code using another coding standard, there is no problem, but you should use ‘indent’ to reformat the code before submitting your work.
Next: Supported ciphersuites, Previous: Support, Up: Top [Contents][Index]
The error codes used throughout the library are described below. The
return code GNUTLS_E_SUCCESS
indicate successful operation, and
is guaranteed to have the value 0, so you can use it in logical
expressions.
0 | GNUTLS_E_SUCCESS | Success. |
-3 | GNUTLS_E_UNKNOWN_COMPRESSION_ALGORITHM | Could not negotiate a supported compression method. |
-6 | GNUTLS_E_UNKNOWN_CIPHER_TYPE | The cipher type is unsupported. |
-7 | GNUTLS_E_LARGE_PACKET | The transmitted packet is too large (EMSGSIZE). |
-8 | GNUTLS_E_UNSUPPORTED_VERSION_PACKET | A record packet with illegal version was received. |
-9 | GNUTLS_E_UNEXPECTED_PACKET_LENGTH | A TLS packet with unexpected length was received. |
-10 | GNUTLS_E_INVALID_SESSION | The specified session has been invalidated for some reason. |
-12 | GNUTLS_E_FATAL_ALERT_RECEIVED | A TLS fatal alert has been received. |
-15 | GNUTLS_E_UNEXPECTED_PACKET | An unexpected TLS packet was received. |
-16 | GNUTLS_E_WARNING_ALERT_RECEIVED | A TLS warning alert has been received. |
-18 | GNUTLS_E_ERROR_IN_FINISHED_PACKET | An error was encountered at the TLS Finished packet calculation. |
-19 | GNUTLS_E_UNEXPECTED_HANDSHAKE_PACKET | An unexpected TLS handshake packet was received. |
-21 | GNUTLS_E_UNKNOWN_CIPHER_SUITE | Could not negotiate a supported cipher suite. |
-22 | GNUTLS_E_UNWANTED_ALGORITHM | An algorithm that is not enabled was negotiated. |
-23 | GNUTLS_E_MPI_SCAN_FAILED | The scanning of a large integer has failed. |
-24 | GNUTLS_E_DECRYPTION_FAILED | Decryption has failed. |
-25 | GNUTLS_E_MEMORY_ERROR | Internal error in memory allocation. |
-26 | GNUTLS_E_DECOMPRESSION_FAILED | Decompression of the TLS record packet has failed. |
-27 | GNUTLS_E_COMPRESSION_FAILED | Compression of the TLS record packet has failed. |
-28 | GNUTLS_E_AGAIN | Resource temporarily unavailable, try again. |
-29 | GNUTLS_E_EXPIRED | The requested session has expired. |
-30 | GNUTLS_E_DB_ERROR | Error in Database backend. |
-31 | GNUTLS_E_SRP_PWD_ERROR | Error in password file. |
-32 | GNUTLS_E_INSUFFICIENT_CREDENTIALS | Insufficient credentials for that request. |
-33 | GNUTLS_E_HASH_FAILED | Hashing has failed. |
-34 | GNUTLS_E_BASE64_DECODING_ERROR | Base64 decoding error. |
-35 | GNUTLS_E_MPI_PRINT_FAILED | Could not export a large integer. |
-37 | GNUTLS_E_REHANDSHAKE | Rehandshake was requested by the peer. |
-38 | GNUTLS_E_GOT_APPLICATION_DATA | TLS Application data were received, while expecting handshake data. |
-39 | GNUTLS_E_RECORD_LIMIT_REACHED | The upper limit of record packet sequence numbers has been reached. Wow! |
-40 | GNUTLS_E_ENCRYPTION_FAILED | Encryption has failed. |
-43 | GNUTLS_E_CERTIFICATE_ERROR | Error in the certificate. |
-44 | GNUTLS_E_PK_ENCRYPTION_FAILED | Public key encryption has failed. |
-45 | GNUTLS_E_PK_DECRYPTION_FAILED | Public key decryption has failed. |
-46 | GNUTLS_E_PK_SIGN_FAILED | Public key signing has failed. |
-47 | GNUTLS_E_X509_UNSUPPORTED_CRITICAL_EXTENSION | Unsupported critical extension in X.509 certificate. |
-48 | GNUTLS_E_KEY_USAGE_VIOLATION | Key usage violation in certificate has been detected. |
-49 | GNUTLS_E_NO_CERTIFICATE_FOUND | No certificate was found. |
-50 | GNUTLS_E_INVALID_REQUEST | The request is invalid. |
-51 | GNUTLS_E_SHORT_MEMORY_BUFFER | The given memory buffer is too short to hold parameters. |
-52 | GNUTLS_E_INTERRUPTED | Function was interrupted. |
-53 | GNUTLS_E_PUSH_ERROR | Error in the push function. |
-54 | GNUTLS_E_PULL_ERROR | Error in the pull function. |
-55 | GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER | An illegal parameter has been received. |
-56 | GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE | The requested data were not available. |
-57 | GNUTLS_E_PKCS1_WRONG_PAD | Wrong padding in PKCS1 packet. |
-58 | GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION | An illegal TLS extension was received. |
-59 | GNUTLS_E_INTERNAL_ERROR | GnuTLS internal error. |
-60 | GNUTLS_E_CERTIFICATE_KEY_MISMATCH | The certificate and the given key do not match. |
-61 | GNUTLS_E_UNSUPPORTED_CERTIFICATE_TYPE | The certificate type is not supported. |
-62 | GNUTLS_E_X509_UNKNOWN_SAN | Unknown Subject Alternative name in X.509 certificate. |
-63 | GNUTLS_E_DH_PRIME_UNACCEPTABLE | The Diffie-Hellman prime sent by the server is not acceptable (not long enough). |
-64 | GNUTLS_E_FILE_ERROR | Error while reading file. |
-67 | GNUTLS_E_ASN1_ELEMENT_NOT_FOUND | ASN1 parser: Element was not found. |
-68 | GNUTLS_E_ASN1_IDENTIFIER_NOT_FOUND | ASN1 parser: Identifier was not found |
-69 | GNUTLS_E_ASN1_DER_ERROR | ASN1 parser: Error in DER parsing. |
-70 | GNUTLS_E_ASN1_VALUE_NOT_FOUND | ASN1 parser: Value was not found. |
-71 | GNUTLS_E_ASN1_GENERIC_ERROR | ASN1 parser: Generic parsing error. |
-72 | GNUTLS_E_ASN1_VALUE_NOT_VALID | ASN1 parser: Value is not valid. |
-73 | GNUTLS_E_ASN1_TAG_ERROR | ASN1 parser: Error in TAG. |
-74 | GNUTLS_E_ASN1_TAG_IMPLICIT | ASN1 parser: error in implicit tag |
-75 | GNUTLS_E_ASN1_TYPE_ANY_ERROR | ASN1 parser: Error in type ’ANY’. |
-76 | GNUTLS_E_ASN1_SYNTAX_ERROR | ASN1 parser: Syntax error. |
-77 | GNUTLS_E_ASN1_DER_OVERFLOW | ASN1 parser: Overflow in DER parsing. |
-78 | GNUTLS_E_TOO_MANY_EMPTY_PACKETS | Too many empty record packets have been received. |
-79 | GNUTLS_E_OPENPGP_UID_REVOKED | The OpenPGP User ID is revoked. |
-80 | GNUTLS_E_UNKNOWN_PK_ALGORITHM | An unknown public key algorithm was encountered. |
-81 | GNUTLS_E_TOO_MANY_HANDSHAKE_PACKETS | Too many handshake packets have been received. |
-84 | GNUTLS_E_NO_TEMPORARY_RSA_PARAMS | No temporary RSA parameters were found. |
-86 | GNUTLS_E_NO_COMPRESSION_ALGORITHMS | No supported compression algorithms have been found. |
-87 | GNUTLS_E_NO_CIPHER_SUITES | No supported cipher suites have been found. |
-88 | GNUTLS_E_OPENPGP_GETKEY_FAILED | Could not get OpenPGP key. |
-89 | GNUTLS_E_PK_SIG_VERIFY_FAILED | Public key signature verification has failed. |
-90 | GNUTLS_E_ILLEGAL_SRP_USERNAME | The SRP username supplied is illegal. |
-91 | GNUTLS_E_SRP_PWD_PARSING_ERROR | Parsing error in password file. |
-93 | GNUTLS_E_NO_TEMPORARY_DH_PARAMS | No temporary DH parameters were found. |
-94 | GNUTLS_E_OPENPGP_FINGERPRINT_UNSUPPORTED | The OpenPGP fingerprint is not supported. |
-95 | GNUTLS_E_X509_UNSUPPORTED_ATTRIBUTE | The certificate has unsupported attributes. |
-96 | GNUTLS_E_UNKNOWN_HASH_ALGORITHM | The hash algorithm is unknown. |
-97 | GNUTLS_E_UNKNOWN_PKCS_CONTENT_TYPE | The PKCS structure’s content type is unknown. |
-98 | GNUTLS_E_UNKNOWN_PKCS_BAG_TYPE | The PKCS structure’s bag type is unknown. |
-99 | GNUTLS_E_INVALID_PASSWORD | The given password contains invalid characters. |
-100 | GNUTLS_E_MAC_VERIFY_FAILED | The Message Authentication Code verification failed. |
-101 | GNUTLS_E_CONSTRAINT_ERROR | Some constraint limits were reached. |
-102 | GNUTLS_E_WARNING_IA_IPHF_RECEIVED | Received a TLS/IA Intermediate Phase Finished message |
-103 | GNUTLS_E_WARNING_IA_FPHF_RECEIVED | Received a TLS/IA Final Phase Finished message |
-104 | GNUTLS_E_IA_VERIFY_FAILED | Verifying TLS/IA phase checksum failed |
-105 | GNUTLS_E_UNKNOWN_ALGORITHM | The specified algorithm or protocol is unknown. |
-106 | GNUTLS_E_UNSUPPORTED_SIGNATURE_ALGORITHM | The signature algorithm is not supported. |
-107 | GNUTLS_E_SAFE_RENEGOTIATION_FAILED | Safe renegotiation failed. |
-108 | GNUTLS_E_UNSAFE_RENEGOTIATION_DENIED | Unsafe renegotiation denied. |
-109 | GNUTLS_E_UNKNOWN_SRP_USERNAME | The SRP username supplied is unknown. |
-110 | GNUTLS_E_PREMATURE_TERMINATION | The TLS connection was non-properly terminated. |
-201 | GNUTLS_E_BASE64_ENCODING_ERROR | Base64 encoding error. |
-202 | GNUTLS_E_INCOMPATIBLE_GCRYPT_LIBRARY | The crypto library version is too old. |
-203 | GNUTLS_E_INCOMPATIBLE_LIBTASN1_LIBRARY | The tasn1 library version is too old. |
-204 | GNUTLS_E_OPENPGP_KEYRING_ERROR | Error loading the keyring. |
-205 | GNUTLS_E_X509_UNSUPPORTED_OID | The OID is not supported. |
-206 | GNUTLS_E_RANDOM_FAILED | Failed to acquire random data. |
-207 | GNUTLS_E_BASE64_UNEXPECTED_HEADER_ERROR | Base64 unexpected header error. |
-208 | GNUTLS_E_OPENPGP_SUBKEY_ERROR | Could not find OpenPGP subkey. |
-209 | GNUTLS_E_CRYPTO_ALREADY_REGISTERED | There is already a crypto algorithm with lower priority. |
-210 | GNUTLS_E_HANDSHAKE_TOO_LARGE | The handshake data size is too large. |
-211 | GNUTLS_E_CRYPTODEV_IOCTL_ERROR | Error interfacing with /dev/crypto |
-212 | GNUTLS_E_CRYPTODEV_DEVICE_ERROR | Error opening /dev/crypto |
-213 | GNUTLS_E_CHANNEL_BINDING_NOT_AVAILABLE | Channel binding data not available |
-214 | GNUTLS_E_BAD_COOKIE | The cookie was bad. |
-215 | GNUTLS_E_OPENPGP_PREFERRED_KEY_ERROR | The OpenPGP key has not a preferred key set. |
-216 | GNUTLS_E_INCOMPAT_DSA_KEY_WITH_TLS_PROTOCOL | The given DSA key is incompatible with the selected TLS protocol. |
-300 | GNUTLS_E_PKCS11_ERROR | PKCS #11 error. |
-301 | GNUTLS_E_PKCS11_LOAD_ERROR | PKCS #11 initialization error. |
-302 | GNUTLS_E_PARSING_ERROR | Error in parsing. |
-303 | GNUTLS_E_PKCS11_PIN_ERROR | PKCS #11 error in PIN. |
-305 | GNUTLS_E_PKCS11_SLOT_ERROR | PKCS #11 error in slot |
-306 | GNUTLS_E_LOCKING_ERROR | Thread locking error |
-307 | GNUTLS_E_PKCS11_ATTRIBUTE_ERROR | PKCS #11 error in attribute |
-308 | GNUTLS_E_PKCS11_DEVICE_ERROR | PKCS #11 error in device |
-309 | GNUTLS_E_PKCS11_DATA_ERROR | PKCS #11 error in data |
-310 | GNUTLS_E_PKCS11_UNSUPPORTED_FEATURE_ERROR | PKCS #11 unsupported feature |
-311 | GNUTLS_E_PKCS11_KEY_ERROR | PKCS #11 error in key |
-312 | GNUTLS_E_PKCS11_PIN_EXPIRED | PKCS #11 PIN expired |
-313 | GNUTLS_E_PKCS11_PIN_LOCKED | PKCS #11 PIN locked |
-314 | GNUTLS_E_PKCS11_SESSION_ERROR | PKCS #11 error in session |
-315 | GNUTLS_E_PKCS11_SIGNATURE_ERROR | PKCS #11 error in signature |
-316 | GNUTLS_E_PKCS11_TOKEN_ERROR | PKCS #11 error in token |
-317 | GNUTLS_E_PKCS11_USER_ERROR | PKCS #11 user error |
-318 | GNUTLS_E_CRYPTO_INIT_FAILED | The initialization of crypto backend has failed. |
-319 | GNUTLS_E_TIMEDOUT | The operation timed out |
-320 | GNUTLS_E_USER_ERROR | The operation was cancelled due to user error |
-321 | GNUTLS_E_ECC_NO_SUPPORTED_CURVES | No supported ECC curves were found |
-322 | GNUTLS_E_ECC_UNSUPPORTED_CURVE | The curve is unsupported |
-323 | GNUTLS_E_PKCS11_REQUESTED_OBJECT_NOT_AVAILBLE | The requested PKCS #11 object is not available |
-324 | GNUTLS_E_CERTIFICATE_LIST_UNSORTED | The provided X.509 certificate list is not sorted (in subject to issuer order) |
-325 | GNUTLS_E_ILLEGAL_PARAMETER | An illegal parameter was found. |
-326 | GNUTLS_E_NO_PRIORITIES_WERE_SET | No or insufficient priorities were set. |
-327 | GNUTLS_E_X509_UNSUPPORTED_EXTENSION | Unsupported extension in X.509 certificate. |
-328 | GNUTLS_E_SESSION_EOF | Peer has terminated the connection |
-341 | GNUTLS_E_OCSP_RESPONSE_ERROR | The OCSP response is invalid |
Next: API reference, Previous: Error codes, Up: Top [Contents][Index]
Ciphersuite name | TLS ID | Since |
---|---|---|
TLS_DH_ANON_ARCFOUR_MD5 | 0x00 0x18 | SSL3.0 |
TLS_DH_ANON_3DES_EDE_CBC_SHA1 | 0x00 0x1B | SSL3.0 |
TLS_DH_ANON_AES_128_CBC_SHA1 | 0x00 0x34 | SSL3.0 |
TLS_DH_ANON_AES_256_CBC_SHA1 | 0x00 0x3A | SSL3.0 |
TLS_DH_ANON_CAMELLIA_128_CBC_SHA1 | 0x00 0x46 | TLS1.0 |
TLS_DH_ANON_CAMELLIA_256_CBC_SHA1 | 0x00 0x89 | TLS1.0 |
TLS_DH_ANON_AES_128_CBC_SHA256 | 0x00 0x6C | TLS1.2 |
TLS_DH_ANON_AES_256_CBC_SHA256 | 0x00 0x6D | TLS1.2 |
TLS_PSK_SHA_ARCFOUR_SHA1 | 0x00 0x8A | TLS1.0 |
TLS_PSK_SHA_3DES_EDE_CBC_SHA1 | 0x00 0x8B | TLS1.0 |
TLS_PSK_SHA_AES_128_CBC_SHA1 | 0x00 0x8C | TLS1.0 |
TLS_PSK_SHA_AES_256_CBC_SHA1 | 0x00 0x8D | TLS1.0 |
TLS_PSK_AES_128_CBC_SHA256 | 0x00 0xAE | TLS1.0 |
TLS_PSK_AES_128_GCM_SHA256 | 0x00 0xA8 | TLS1.2 |
TLS_PSK_NULL_SHA256 | 0x00 0xB0 | TLS1.0 |
TLS_DHE_PSK_SHA_ARCFOUR_SHA1 | 0x00 0x8E | TLS1.0 |
TLS_DHE_PSK_SHA_3DES_EDE_CBC_SHA1 | 0x00 0x8F | TLS1.0 |
TLS_DHE_PSK_SHA_AES_128_CBC_SHA1 | 0x00 0x90 | TLS1.0 |
TLS_DHE_PSK_SHA_AES_256_CBC_SHA1 | 0x00 0x91 | TLS1.0 |
TLS_DHE_PSK_AES_128_CBC_SHA256 | 0x00 0xB2 | TLS1.0 |
TLS_DHE_PSK_AES_128_GCM_SHA256 | 0x00 0xAA | TLS1.2 |
TLS_DHE_PSK_NULL_SHA256 | 0x00 0xB4 | TLS1.0 |
TLS_SRP_SHA_3DES_EDE_CBC_SHA1 | 0xC0 0x1A | TLS1.0 |
TLS_SRP_SHA_AES_128_CBC_SHA1 | 0xC0 0x1D | TLS1.0 |
TLS_SRP_SHA_AES_256_CBC_SHA1 | 0xC0 0x20 | TLS1.0 |
TLS_SRP_SHA_DSS_3DES_EDE_CBC_SHA1 | 0xC0 0x1C | TLS1.0 |
TLS_SRP_SHA_RSA_3DES_EDE_CBC_SHA1 | 0xC0 0x1B | TLS1.0 |
TLS_SRP_SHA_DSS_AES_128_CBC_SHA1 | 0xC0 0x1F | TLS1.0 |
TLS_SRP_SHA_RSA_AES_128_CBC_SHA1 | 0xC0 0x1E | TLS1.0 |
TLS_SRP_SHA_DSS_AES_256_CBC_SHA1 | 0xC0 0x22 | TLS1.0 |
TLS_SRP_SHA_RSA_AES_256_CBC_SHA1 | 0xC0 0x21 | TLS1.0 |
TLS_DHE_DSS_ARCFOUR_SHA1 | 0x00 0x66 | TLS1.0 |
TLS_DHE_DSS_3DES_EDE_CBC_SHA1 | 0x00 0x13 | SSL3.0 |
TLS_DHE_DSS_AES_128_CBC_SHA1 | 0x00 0x32 | SSL3.0 |
TLS_DHE_DSS_AES_256_CBC_SHA1 | 0x00 0x38 | SSL3.0 |
TLS_DHE_DSS_CAMELLIA_128_CBC_SHA1 | 0x00 0x44 | TLS1.0 |
TLS_DHE_DSS_CAMELLIA_256_CBC_SHA1 | 0x00 0x87 | TLS1.0 |
TLS_DHE_DSS_AES_128_CBC_SHA256 | 0x00 0x40 | TLS1.2 |
TLS_DHE_DSS_AES_256_CBC_SHA256 | 0x00 0x6A | TLS1.2 |
TLS_DHE_RSA_3DES_EDE_CBC_SHA1 | 0x00 0x16 | SSL3.0 |
TLS_DHE_RSA_AES_128_CBC_SHA1 | 0x00 0x33 | SSL3.0 |
TLS_DHE_RSA_AES_256_CBC_SHA1 | 0x00 0x39 | SSL3.0 |
TLS_DHE_RSA_CAMELLIA_128_CBC_SHA1 | 0x00 0x45 | TLS1.0 |
TLS_DHE_RSA_CAMELLIA_256_CBC_SHA1 | 0x00 0x88 | TLS1.0 |
TLS_DHE_RSA_AES_128_CBC_SHA256 | 0x00 0x67 | TLS1.2 |
TLS_DHE_RSA_AES_256_CBC_SHA256 | 0x00 0x6B | TLS1.2 |
TLS_RSA_NULL_MD5 | 0x00 0x01 | SSL3.0 |
TLS_RSA_NULL_SHA1 | 0x00 0x02 | SSL3.0 |
TLS_RSA_NULL_SHA256 | 0x00 0x3B | TLS1.2 |
TLS_RSA_EXPORT_ARCFOUR_40_MD5 | 0x00 0x03 | SSL3.0 |
TLS_RSA_ARCFOUR_SHA1 | 0x00 0x05 | SSL3.0 |
TLS_RSA_ARCFOUR_MD5 | 0x00 0x04 | SSL3.0 |
TLS_RSA_3DES_EDE_CBC_SHA1 | 0x00 0x0A | SSL3.0 |
TLS_RSA_AES_128_CBC_SHA1 | 0x00 0x2F | SSL3.0 |
TLS_RSA_AES_256_CBC_SHA1 | 0x00 0x35 | SSL3.0 |
TLS_RSA_CAMELLIA_128_CBC_SHA1 | 0x00 0x41 | TLS1.0 |
TLS_RSA_CAMELLIA_256_CBC_SHA1 | 0x00 0x84 | TLS1.0 |
TLS_RSA_AES_128_CBC_SHA256 | 0x00 0x3C | TLS1.2 |
TLS_RSA_AES_256_CBC_SHA256 | 0x00 0x3D | TLS1.2 |
TLS_RSA_AES_128_GCM_SHA256 | 0x00 0x9C | TLS1.2 |
TLS_DHE_RSA_AES_128_GCM_SHA256 | 0x00 0x9E | TLS1.2 |
TLS_DHE_DSS_AES_128_GCM_SHA256 | 0x00 0xA2 | TLS1.2 |
TLS_DH_ANON_AES_128_GCM_SHA256 | 0x00 0xA6 | TLS1.2 |
TLS_ECDH_ANON_NULL_SHA1 | 0xC0 0x15 | SSL3.0 |
TLS_ECDH_ANON_3DES_EDE_CBC_SHA1 | 0xC0 0x17 | SSL3.0 |
TLS_ECDH_ANON_AES_128_CBC_SHA1 | 0xC0 0x18 | SSL3.0 |
TLS_ECDH_ANON_AES_256_CBC_SHA1 | 0xC0 0x19 | SSL3.0 |
TLS_ECDHE_RSA_NULL_SHA1 | 0xC0 0x10 | SSL3.0 |
TLS_ECDHE_RSA_3DES_EDE_CBC_SHA1 | 0xC0 0x12 | SSL3.0 |
TLS_ECDHE_RSA_AES_128_CBC_SHA1 | 0xC0 0x13 | SSL3.0 |
TLS_ECDHE_RSA_AES_256_CBC_SHA1 | 0xC0 0x14 | SSL3.0 |
TLS_ECDHE_ECDSA_NULL_SHA1 | 0xC0 0x06 | SSL3.0 |
TLS_ECDHE_ECDSA_3DES_EDE_CBC_SHA1 | 0xC0 0x08 | SSL3.0 |
TLS_ECDHE_ECDSA_AES_128_CBC_SHA1 | 0xC0 0x09 | SSL3.0 |
TLS_ECDHE_ECDSA_AES_256_CBC_SHA1 | 0xC0 0x0A | SSL3.0 |
TLS_ECDHE_ECDSA_AES_128_CBC_SHA256 | 0xC0 0x23 | TLS1.2 |
TLS_ECDHE_RSA_AES_128_CBC_SHA256 | 0xC0 0x27 | TLS1.2 |
TLS_ECDHE_ECDSA_AES_128_GCM_SHA256 | 0xC0 0x2B | TLS1.2 |
TLS_ECDHE_RSA_AES_128_GCM_SHA256 | 0xC0 0x2F | TLS1.2 |
TLS_ECDHE_PSK_3DES_EDE_CBC_SHA1 | 0xC0 0x34 | SSL3.0 |
TLS_ECDHE_PSK_AES_128_CBC_SHA1 | 0xC0 0x35 | SSL3.0 |
TLS_ECDHE_PSK_AES_256_CBC_SHA1 | 0xC0 0x36 | SSL3.0 |
TLS_ECDHE_PSK_AES_128_CBC_SHA256 | 0xC0 0x37 | SSL3.0 |
TLS_ECDHE_PSK_AES_256_CBC_SHA384 | 0xC0 0x38 | SSL3.0 |
TLS_ECDHE_PSK_NULL_SHA256 | 0xC0 0x3A | SSL3.0 |
TLS_ECDHE_PSK_NULL_SHA384 | 0xC0 0x3B | SSL3.0 |
TLS_ECDHE_ECDSA_AES_256_GCM_SHA384 | 0xC0 0x2C | TLS1.2 |
TLS_ECDHE_RSA_AES_256_GCM_SHA384 | 0xC0 0x30 | TLS1.2 |
TLS_ECDHE_ECDSA_AES_256_CBC_SHA384 | 0xC0 0x24 | TLS1.2 |
TLS_PSK_WITH_AES_256_GCM_SHA384 | 0x00 0xA9 | TLS1.2 |
TLS_DHE_PSK_WITH_AES_256_GCM_SHA384 | 0x00 0xAB | TLS1.2 |
X.509
OPENPGP
SSL3.0
TLS1.0
TLS1.1
TLS1.2
DTLS0.9
DTLS1.0
AES-256-CBC
AES-192-CBC
AES-128-CBC
AES-128-GCM
AES-256-GCM
ARCFOUR-128
CAMELLIA-256-CBC
CAMELLIA-128-CBC
3DES-CBC
DES-CBC
ARCFOUR-40
RC2-40
SHA1
MD5
SHA256
SHA384
SHA512
SHA224
AEAD
ANON-DH
ANON-ECDH
RSA
RSA-EXPORT
DHE-RSA
ECDHE-RSA
ECDHE-ECDSA
DHE-DSS
SRP-DSS
SRP-RSA
SRP
PSK
DHE-PSK
ECDHE-PSK
RSA
DSA
EC
RSA-SHA1
RSA-SHA224
RSA-SHA256
RSA-SHA384
RSA-SHA512
RSA-RMD160
DSA-SHA1
DSA-SHA224
DSA-SHA256
RSA-MD5
RSA-MD2
ECDSA-SHA1
ECDSA-SHA224
ECDSA-SHA256
ECDSA-SHA384
ECDSA-SHA512
SECP192R1
SECP224R1
SECP256R1
SECP384R1
SECP521R1
DEFLATE
NULL
Next: Copying Information, Previous: Supported ciphersuites, Up: Top [Contents][Index]
• Core TLS API: | ||
• Datagram TLS API: | ||
• X509 certificate API: | ||
• OCSP API: | ||
• OpenPGP API: | ||
• PKCS 12 API: | ||
• PKCS 11 API: | ||
• Abstract key API: | ||
• Cryptographic API: | ||
• Compatibility API: |
Next: Datagram TLS API, Up: API reference [Contents][Index]
The prototypes for the following functions lie in gnutls/gnutls.h.
session: is a gnutls_session_t
structure.
This function will return the last alert number received. This
function should be called when GNUTLS_E_WARNING_ALERT_RECEIVED
or
GNUTLS_E_FATAL_ALERT_RECEIVED
errors are returned by a gnutls
function. The peer may send alerts if he encounters an error.
If no alert has been received the returned value is undefined.
Returns: the last alert received, a
gnutls_alert_description_t
value.
alert: is an alert number.
This function will return a string that describes the given alert
number, or NULL
. See gnutls_alert_get()
.
Returns: string corresponding to gnutls_alert_description_t
value.
alert: is an alert number.
This function will return a string of the name of the alert.
Returns: string corresponding to gnutls_alert_description_t
value.
Since: 3.0
session: is a gnutls_session_t
structure.
level: is the level of the alert
desc: is the alert description
This function will send an alert to the peer in order to inform him of something important (eg. his Certificate could not be verified). If the alert level is Fatal then the peer is expected to close the connection, otherwise he may ignore the alert and continue.
The error code of the underlying record send function will be
returned, so you may also receive GNUTLS_E_INTERRUPTED
or
GNUTLS_E_AGAIN
as well.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls_session_t
structure.
err: is an integer
Sends an alert to the peer depending on the error code returned by
a gnutls function. This function will call gnutls_error_to_alert()
to determine the appropriate alert to send.
This function may also return GNUTLS_E_AGAIN
, or
GNUTLS_E_INTERRUPTED
.
If the return value is GNUTLS_E_INVALID_REQUEST
, then no alert has
been sent to the peer.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
sc: is a pointer to a gnutls_anon_client_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
sc: is a pointer to a gnutls_anon_server_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
sc: is a gnutls_anon_client_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.
sc: is a gnutls_anon_server_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.
res: is a gnutls_anon_server_credentials_t structure
func: is the function to be called
This function will set a callback in order for the server to get
the Diffie-Hellman or RSA parameters for anonymous authentication.
The callback should return GNUTLS_E_SUCCESS
(0) on success.
res: is a gnutls_anon_server_credentials_t structure
dh_params: is a structure that holds Diffie-Hellman parameters.
This function will set the Diffie-Hellman parameters for an anonymous server to use. These parameters will be used in Anonymous Diffie-Hellman cipher suites.
res: is a gnutls_certificate_credentials_t structure
func: is the function to be called
This function will set a callback in order for the server to get
the Diffie-Hellman parameters for anonymous authentication. The
callback should return GNUTLS_E_SUCCESS
(0) on success.
session: is a gnutls_session_t
structure.
Returns the type of credentials that were used for client authentication. The returned information is to be used to distinguish the function used to access authentication data.
Returns: The type of credentials for the client authentication
schema, a gnutls_credentials_type_t
type.
session: is a gnutls_session_t
structure.
Returns type of credentials for the current authentication schema. The returned information is to be used to distinguish the function used to access authentication data.
Eg. for CERTIFICATE ciphersuites (key exchange algorithms:
GNUTLS_KX_RSA
, GNUTLS_KX_DHE_RSA
), the same function are to be
used to access the authentication data.
Returns: The type of credentials for the current authentication
schema, a gnutls_credentials_type_t
type.
session: is a gnutls_session_t
structure.
Returns the type of credentials that were used for server authentication. The returned information is to be used to distinguish the function used to access authentication data.
Returns: The type of credentials for the server authentication
schema, a gnutls_credentials_type_t
type.
session: is a gnutls_session_t
structure.
how: is an integer
Terminates the current TLS/SSL connection. The connection should
have been initiated using gnutls_handshake()
. how
should be one
of GNUTLS_SHUT_RDWR
, GNUTLS_SHUT_WR
.
In case of GNUTLS_SHUT_RDWR
the TLS session gets
terminated and further receives and sends will be disallowed. If
the return value is zero you may continue using the underlying
transport layer. GNUTLS_SHUT_RDWR
sends an alert containing a close
request and waits for the peer to reply with the same message.
In case of GNUTLS_SHUT_WR
the TLS session gets terminated
and further sends will be disallowed. In order to reuse the
connection you should wait for an EOF from the peer.
GNUTLS_SHUT_WR
sends an alert containing a close request.
Note that not all implementations will properly terminate a TLS connection. Some of them, usually for performance reasons, will terminate only the underlying transport layer, and thus not distinguishing between a malicious party prematurely terminating the connection and normal termination.
This function may also return GNUTLS_E_AGAIN
or
GNUTLS_E_INTERRUPTED
; cf. gnutls_record_get_direction()
.
Returns: GNUTLS_E_SUCCESS
on success, or an error code, see
function documentation for entire semantics.
session: is a gnutls session
This function will return the peer’s certificate activation time. This is the creation time for openpgp keys.
Returns: (time_t)-1 on error.
Deprecated: gnutls_certificate_verify_peers2()
now verifies activation times.
res: is a pointer to a gnutls_certificate_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
session: is a gnutls session
Get whether client certificate is requested or not.
Returns: 0 if the peer (server) did not request client authentication or 1 otherwise, or a negative error code in case of error.
session: is a gnutls session
This function will return the peer’s certificate expiration time.
Returns: (time_t)-1 on error.
Deprecated: gnutls_certificate_verify_peers2()
now verifies expiration times.
sc: is a gnutls_certificate_credentials_t
structure.
This function will delete all the CA name in the given credentials. Clients may call this to save some memory since in client side the CA names are not used. Servers might want to use this function if a large list of trusted CAs is present and sending the names of it would just consume bandwidth without providing information to client.
CA names are used by servers to advertise the CAs they support to clients.
sc: is a gnutls_certificate_credentials_t
structure.
This function will delete all the CAs associated with the given
credentials. Servers that do not use
gnutls_certificate_verify_peers2()
may call this to save some
memory.
sc: is a gnutls_certificate_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.
This function does not free any temporary parameters associated with this structure (ie RSA and DH parameters are not freed by this function).
sc: is a gnutls_certificate_credentials_t
structure.
This function will delete all the CRLs associated with the given credentials.
sc: is a gnutls_certificate_credentials_t
structure.
This function will delete all the keys and the certificates associated with the given credentials. This function must not be called when a TLS negotiation that uses the credentials is in progress.
sc: is a gnutls_certificate_credentials_t
structure.
cert: is the certificate to find issuer for
issuer: Will hold the issuer if any. Should be treated as constant.
flags: Use zero.
This function will return the issuer of a given certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
session: is a gnutls session
Gets the certificate as sent to the peer in the last handshake. The certificate is in raw (DER) format. No certificate list is being returned. Only the first certificate.
Returns: a pointer to a gnutls_datum_t
containing our
certificate, or NULL
in case of an error or if no certificate
was used.
session: is a gnutls session
list_size: is the length of the certificate list
Get the peer’s raw certificate (chain) as sent by the peer. These certificates are in raw format (DER encoded for X.509). In case of a X.509 then a certificate list may be present. The first certificate in the list is the peer’s certificate, following the issuer’s certificate, then the issuer’s issuer etc.
In case of OpenPGP keys a single key will be returned in raw format.
Returns: a pointer to a gnutls_datum_t
containing our
certificates, or NULL
in case of an error or if no certificate
was used.
session: is a pointer to a gnutls_session_t
structure.
status: is 0 or 1
If status is non zero, this function will order gnutls not to send the rdnSequence in the certificate request message. That is the server will not advertise its trusted CAs to the peer. If status is zero then the default behaviour will take effect, which is to advertise the server’s trusted CAs.
This function has no effect in clients, and in authentication methods other than certificate with X.509 certificates.
session: is a gnutls_session_t
structure.
req: is one of GNUTLS_CERT_REQUEST, GNUTLS_CERT_REQUIRE
This function specifies if we (in case of a server) are going to
send a certificate request message to the client. If req
is
GNUTLS_CERT_REQUIRE then the server will return an error if the
peer does not provide a certificate. If you do not call this
function then the client will not be asked to send a certificate.
res: is a gnutls_certificate_credentials_t structure
dh_params: is a structure that holds Diffie-Hellman parameters.
This function will set the Diffie-Hellman parameters for a certificate server to use. These parameters will be used in Ephemeral Diffie-Hellman cipher suites. Note that only a pointer to the parameters are stored in the certificate handle, so if you deallocate the parameters before the certificate is deallocated, you must change the parameters stored in the certificate first.
res: is a gnutls_certificate_credentials_t structure
func: is the function to be called
This function will set a callback in order for the server to get
the Diffie-Hellman or RSA parameters for certificate
authentication. The callback should return GNUTLS_E_SUCCESS
(0) on success.
cred: is a gnutls_certificate_credentials_t
structure.
func: is the callback function
This function sets a callback to be called in order to retrieve the
certificate to be used in the handshake. You are advised
to use gnutls_certificate_set_retrieve_function2()
because it
is much more efficient in the processing it requires from gnutls.
The callback’s function prototype is: int (*callback)(gnutls_session_t, const gnutls_datum_t* req_ca_dn, int nreqs, const gnutls_pk_algorithm_t* pk_algos, int pk_algos_length, gnutls_retr2_st* st);
req_ca_cert
is only used in X.509 certificates.
Contains a list with the CA names that the server considers trusted.
Normally we should send a certificate that is signed
by one of these CAs. These names are DER encoded. To get a more
meaningful value use the function gnutls_x509_rdn_get()
.
pk_algos
contains a list with server’s acceptable signature algorithms.
The certificate returned should support the server’s given algorithms.
st
should contain the certificates and private keys.
If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received.
In server side pk_algos and req_ca_dn are NULL.
The callback function should set the certificate list to be sent, and return 0 on success. If no certificate was selected then the number of certificates should be set to zero. The value (-1) indicates error and the handshake will be terminated.
Since: 3.0
res: is a gnutls_certificate_credentials_t structure
flags: are the flags
This function will set the flags to be used at verification of the
certificates. Flags must be OR of the
gnutls_certificate_verify_flags
enumerations. The default
for TLS sessions is GNUTLS_VERIFY_ALLOW_UNSORTED_CHAIN.
cred: is a gnutls_certificate_credentials_t
structure.
func: is the callback function
This function sets a callback to be called when peer’s certificate has been received in order to verify it on receipt rather than doing after the handshake is completed.
The callback’s function prototype is: int (*callback)(gnutls_session_t);
If the callback function is provided then gnutls will call it, in the
handshake, just after the certificate message has been received.
To verify or obtain the certificate the gnutls_certificate_verify_peers2()
,
gnutls_certificate_type_get()
, gnutls_certificate_get_peers()
functions
can be used.
The callback function should return 0 for the handshake to continue or non-zero to terminate.
Since: 2.10.0
res: is a gnutls_certificate_credentials structure
max_bits: is the number of bits of an acceptable certificate (default 8200)
max_depth: is maximum depth of the verification of a certificate chain (default 5)
This function will set some upper limits for the default
verification function, gnutls_certificate_verify_peers2()
, to avoid
denial of service attacks. You can set them to zero to disable
limits.
res: is a gnutls_certificate_credentials_t
structure.
crl_list: is a list of trusted CRLs. They should have been verified before.
crl_list_size: holds the size of the crl_list
This function adds the trusted CRLs in order to verify client or
server certificates. In case of a client this is not required to
be called if the certificates are not verified using
gnutls_certificate_verify_peers2()
. This function may be called
multiple times.
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
Since: 2.4.0
res: is a gnutls_certificate_credentials_t
structure.
crlfile: is a file containing the list of verified CRLs (DER or PEM list)
type: is PEM or DER
This function adds the trusted CRLs in order to verify client or server
certificates. In case of a client this is not required
to be called if the certificates are not verified using
gnutls_certificate_verify_peers2()
.
This function may be called multiple times.
Returns: number of CRLs processed or a negative error code on error.
res: is a gnutls_certificate_credentials_t
structure.
CRL: is a list of trusted CRLs. They should have been verified before.
type: is DER or PEM
This function adds the trusted CRLs in order to verify client or
server certificates. In case of a client this is not required to
be called if the certificates are not verified using
gnutls_certificate_verify_peers2()
. This function may be called
multiple times.
Returns: number of CRLs processed, or a negative error code on error.
res: is a gnutls_certificate_credentials_t
structure.
cert_list: contains a certificate list (path) for the specified private key
cert_list_size: holds the size of the certificate list
key: is a gnutls_x509_privkey_t key
This function sets a certificate/private key pair in the
gnutls_certificate_credentials_t structure. This function may be
called more than once, in case multiple keys/certificates exist for
the server. For clients that wants to send more than its own end
entity certificate (e.g., also an intermediate CA cert) then put
the certificate chain in cert_list
.
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
Since: 2.4.0
res: is a gnutls_certificate_credentials_t
structure.
certfile: is a file that containing the certificate list (path) for the specified private key, in PKCS7 format, or a list of certificates
keyfile: is a file that contains the private key
type: is PEM or DER
This function sets a certificate/private key pair in the
gnutls_certificate_credentials_t structure. This function may be
called more than once, in case multiple keys/certificates exist for
the server. For clients that need to send more than its own end
entity certificate, e.g., also an intermediate CA cert, then the
certfile
must contain the ordered certificate chain.
This function can also accept PKCS 11
URLs at keyfile
and certfile
. In that case it
will import the private key and certificate indicated by the URLs.
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
res: is a gnutls_certificate_credentials_t
structure.
cert: contains a certificate list (path) for the specified private key
key: is the private key, or NULL
type: is PEM or DER
This function sets a certificate/private key pair in the gnutls_certificate_credentials_t structure. This function may be called more than once, in case multiple keys/certificates exist for the server.
Note that the keyUsage (2.5.29.15) PKIX extension in X.509 certificates is supported. This means that certificates intended for signing cannot be used for ciphersuites that require encryption.
If the certificate and the private key are given in PEM encoding then the strings that hold their values must be null terminated.
The key
may be NULL
if you are using a sign callback, see
gnutls_sign_callback_set()
.
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
res: is a gnutls_certificate_credentials_t
structure.
pkcs12file: filename of file containing PKCS12
blob.
type: is PEM or DER of the pkcs12file
.
password: optional password used to decrypt PKCS12
file, bags and keys.
This function sets a certificate/private key pair and/or a CRL in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server).
PKCS12
files with a MAC, encrypted bags and PKCS 8
private keys are supported. However,
only password based security, and the same password for all
operations, are supported.
PKCS12
file may contain many keys and/or certificates, and there
is no way to identify which key/certificate pair you want. You
should make sure the PKCS12
file only contain one key/certificate
pair and/or one CRL.
It is believed that the limitations of this function is acceptable for most usage, and that any more flexibility would introduce complexity that would make it harder to use this functionality at all.
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
res: is a gnutls_certificate_credentials_t
structure.
p12blob: the PKCS12
blob.
type: is PEM or DER of the pkcs12file
.
password: optional password used to decrypt PKCS12
file, bags and keys.
This function sets a certificate/private key pair and/or a CRL in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server).
MAC: ed PKCS12
files are supported. Encrypted PKCS12
bags are
supported. Encrypted PKCS8
private keys are supported. However,
only password based security, and the same password for all
operations, are supported.
PKCS12
file may contain many keys and/or certificates, and there
is no way to identify which key/certificate pair you want. You
should make sure the PKCS12
file only contain one key/certificate
pair and/or one CRL.
It is believed that the limitations of this function is acceptable for most usage, and that any more flexibility would introduce complexity that would make it harder to use this functionality at all.
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
Since: 2.8.0
cred: is a gnutls_certificate_credentials_t
structure.
This function adds the system’s default trusted CAs in order to verify client or server certificates.
In the case the system is currently unsupported GNUTLS_E_UNIMPLEMENTED_FEATURE
is returned.
Returns: the number of certificates processed or a negative error code on error.
Since: 3.0
res: is a gnutls_certificate_credentials_t
structure.
ca_list: is a list of trusted CAs
ca_list_size: holds the size of the CA list
This function adds the trusted CAs in order to verify client
or server certificates. In case of a client this is not required
to be called if the certificates are not verified using
gnutls_certificate_verify_peers2()
.
This function may be called multiple times.
In case of a server the CAs set here will be sent to the client if
a certificate request is sent. This can be disabled using
gnutls_certificate_send_x509_rdn_sequence()
.
Returns: the number of certificates processed or a negative error code on error.
Since: 2.4.0
cred: is a gnutls_certificate_credentials_t
structure.
cafile: is a file containing the list of trusted CAs (DER or PEM list)
type: is PEM or DER
This function adds the trusted CAs in order to verify client or
server certificates. In case of a client this is not required to
be called if the certificates are not verified using
gnutls_certificate_verify_peers2()
. This function may be called
multiple times.
In case of a server the names of the CAs set here will be sent to
the client if a certificate request is sent. This can be disabled
using gnutls_certificate_send_x509_rdn_sequence()
.
This function can also accept PKCS 11
URLs. In that case it
will import all certificates that are marked as trusted.
Returns: number of certificates processed, or a negative error code on error.
res: is a gnutls_certificate_credentials_t
structure.
ca: is a list of trusted CAs or a DER certificate
type: is DER or PEM
This function adds the trusted CAs in order to verify client or
server certificates. In case of a client this is not required to be
called if the certificates are not verified using
gnutls_certificate_verify_peers2()
. This function may be called
multiple times.
In case of a server the CAs set here will be sent to the client if
a certificate request is sent. This can be disabled using
gnutls_certificate_send_x509_rdn_sequence()
.
Returns: the number of certificates processed or a negative error code on error.
session: is a gnutls_session_t
structure.
The certificate type is by default X.509, unless it is negotiated as a TLS extension.
Returns: the currently used gnutls_certificate_type_t
certificate
type.
name: is a certificate type name
The names are compared in a case insensitive way.
Returns: a gnutls_certificate_type_t
for the specified in a
string certificate type, or GNUTLS_CRT_UNKNOWN
on error.
type: is a certificate type
Convert a gnutls_certificate_type_t
type to a string.
Returns: a string that contains the name of the specified
certificate type, or NULL
in case of unknown types.
Get a list of certificate types. Note that to be able to use
OpenPGP certificates, you must link to libgnutls-extra and call
gnutls_global_init_extra()
.
Returns: a (0)-terminated list of gnutls_certificate_type_t
integers indicating the available certificate types.
session: is a gnutls session
status: is the output of the verification
This function will try to verify the peer’s certificate and return
its status (trusted, invalid etc.). The value of status
should
be one or more of the gnutls_certificate_status_t enumerated
elements bitwise or’d. To avoid denial of service attacks some
default upper limits regarding the certificate key size and chain
size are set. To override them use
gnutls_certificate_set_verify_limits()
.
Note that you must also check the peer’s name in order to check if the verified certificate belongs to the actual peer.
This function uses gnutls_x509_crt_list_verify()
with the CAs in
the credentials as trusted CAs.
Returns: a negative error code on error and GNUTLS_E_SUCCESS
(0) on success.
req_version: version string to compare with, or NULL
.
Check GnuTLS Library version.
See GNUTLS_VERSION
for a suitable req_version
string.
Returns: Check that the version of the library is at
minimum the one given as a string in req_version
and return the
actual version string of the library; return NULL
if the
condition is not met. If NULL
is passed to this function no
check is done and only the version string is returned.
session: is a gnutls_session_t
structure.
Get currently used cipher.
Returns: the currently used cipher, a gnutls_cipher_algorithm_t
type.
name: is a cipher algorithm name
The names are compared in a case insensitive way.
Returns: return a gnutls_cipher_algorithm_t
value corresponding to
the specified cipher, or GNUTLS_CIPHER_UNKNOWN
on error.
algorithm: is an encryption algorithm
Get key size for cipher.
Returns: length (in bytes) of the given cipher’s key size, or 0 if the given cipher is invalid.
algorithm: is an encryption algorithm
Convert a gnutls_cipher_algorithm_t
type to a string.
Returns: a pointer to a string that contains the name of the
specified cipher, or NULL
.
Get a list of supported cipher algorithms. Note that not
necessarily all ciphers are supported as TLS cipher suites. For
example, DES is not supported as a cipher suite, but is supported
for other purposes (e.g., PKCS8
or similar).
This function is not thread safe.
Returns: a (0)-terminated list of gnutls_cipher_algorithm_t
integers indicating the available ciphers.
kx_algorithm: is a Key exchange algorithm
cipher_algorithm: is a cipher algorithm
mac_algorithm: is a MAC algorithm
Note that the full cipher suite name must be prepended by TLS or SSL depending of the protocol in use.
Returns: a string that contains the name of a TLS cipher suite,
specified by the given algorithms, or NULL
.
idx: index of cipher suite to get information about, starts on 0.
cs_id: output buffer with room for 2 bytes, indicating cipher suite value
kx: output variable indicating key exchange algorithm, or NULL
.
cipher: output variable indicating cipher, or NULL
.
mac: output variable indicating MAC algorithm, or NULL
.
min_version: output variable indicating TLS protocol version, or NULL
.
Get information about supported cipher suites. Use the function iteratively to get information about all supported cipher suites. Call with idx=0 to get information about first cipher suite, then idx=1 and so on until the function returns NULL.
Returns: the name of idx
cipher suite, and set the information
about the cipher suite in the output variables. If idx
is out of
bounds, NULL
is returned.
session: is a gnutls_session_t
structure.
Get currently used compression algorithm.
Returns: the currently used compression method, a
gnutls_compression_method_t
value.
name: is a compression method name
The names are compared in a case insensitive way.
Returns: an id of the specified in a string compression method, or
GNUTLS_COMP_UNKNOWN
on error.
algorithm: is a Compression algorithm
Convert a gnutls_compression_method_t
value to a string.
Returns: a pointer to a string that contains the name of the
specified compression algorithm, or NULL
.
Get a list of compression methods.
Returns: a zero-terminated list of gnutls_compression_method_t
integers indicating the available compression methods.
session: is a gnutls_session_t
structure.
Clears all the credentials previously set in this session.
session: is a gnutls_session_t
structure.
type: is the type of the credentials
cred: is a pointer to a structure.
Sets the needed credentials for the specified type. Eg username,
password - or public and private keys etc. The cred
parameter is
a structure that depends on the specified type and on the current
session (client or server).
In order to minimize memory usage, and share credentials between
several threads gnutls keeps a pointer to cred, and not the whole
cred structure. Thus you will have to keep the structure allocated
until you call gnutls_deinit()
.
For GNUTLS_CRD_ANON
, cred
should be
gnutls_anon_client_credentials_t
in case of a client. In case of
a server it should be gnutls_anon_server_credentials_t
.
For GNUTLS_CRD_SRP
, cred
should be gnutls_srp_client_credentials_t
in case of a client, and gnutls_srp_server_credentials_t
, in case
of a server.
For GNUTLS_CRD_CERTIFICATE
, cred
should be
gnutls_certificate_credentials_t
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
session: is a gnutls_session_t
structure.
session_entry: is the session data (not key)
Check if database entry has expired. This function is to be used when you want to clear unnecessary sessions which occupy space in your backend.
Returns: Returns GNUTLS_E_EXPIRED
, if the database entry has
expired or 0 otherwise.
session: is a gnutls_session_t
structure.
Get db function pointer.
Returns: the pointer that will be sent to db store, retrieve and delete functions, as the first argument.
session: is a gnutls_session_t
structure.
This function will remove the current session data from the
session database. This will prevent future handshakes reusing
these session data. This function should be called if a session
was terminated abnormally, and before gnutls_deinit()
is called.
Normally gnutls_deinit()
will remove abnormally terminated
sessions.
session: is a gnutls_session_t
structure.
seconds: is the number of seconds.
Set the expiration time for resumed sessions. The default is 3600 (one hour) at the time of this writing.
session: is a gnutls_session_t
structure.
ptr: is the pointer
Sets the pointer that will be provided to db store, retrieve and delete functions, as the first argument.
session: is a gnutls_session_t
structure.
rem_func: is the function.
Sets the function that will be used to remove data from the resumed sessions database. This function must return 0 on success.
The first argument to rem_func
will be null unless
gnutls_db_set_ptr()
has been called.
session: is a gnutls_session_t
structure.
retr_func: is the function.
Sets the function that will be used to retrieve data from the resumed sessions database. This function must return a gnutls_datum_t containing the data on success, or a gnutls_datum_t containing null and 0 on failure.
The datum’s data must be allocated using the function
gnutls_malloc()
.
The first argument to retr_func
will be null unless
gnutls_db_set_ptr()
has been called.
session: is a gnutls_session_t
structure.
store_func: is the function
Sets the function that will be used to store data in the resumed sessions database. This function must return 0 on success.
The first argument to store_func
will be null unless
gnutls_db_set_ptr()
has been called.
session: is a gnutls_session_t
structure.
This function clears all buffers associated with the session
.
This function will also remove session data from the session
database if the session was terminated abnormally.
session: is a gnutls session
raw_gen: will hold the generator.
raw_prime: will hold the prime.
This function will return the group parameters used in the last
Diffie-Hellman key exchange with the peer. These are the prime and
the generator used. This function should be used for both
anonymous and ephemeral Diffie-Hellman. The output parameters must
be freed with gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls session
Get the Diffie-Hellman public key bit size. Can be used for both anonymous and ephemeral Diffie-Hellman.
Returns: The public key bit size used in the last Diffie-Hellman key exchange with the peer, or a negative error code in case of error.
session: is a gnutls session
This function will return the bits of the prime used in the last Diffie-Hellman key exchange with the peer. Should be used for both anonymous and ephemeral Diffie-Hellman. Note that some ciphers, like RSA and DSA without DHE, do not use a Diffie-Hellman key exchange, and then this function will return 0.
Returns: The Diffie-Hellman bit strength is returned, or 0 if no Diffie-Hellman key exchange was done, or a negative error code on failure.
session: is a gnutls session
raw_key: will hold the public key.
This function will return the peer’s public key used in the last
Diffie-Hellman key exchange. This function should be used for both
anonymous and ephemeral Diffie-Hellman. The output parameters must
be freed with gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls session
This function will return the bits used in the last Diffie-Hellman key exchange with the peer. Should be used for both anonymous and ephemeral Diffie-Hellman.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
dst: Is the destination structure, which should be initialized.
src: Is the source structure
This function will copy the DH parameters structure from source to destination.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
dh_params: Is a structure that holds the prime numbers
This function will deinitialize the DH parameters structure.
params: Holds the DH parameters
format: the format of output params. One of PEM or DER.
params_data: will contain a PKCS3 DHParams structure PEM or DER encoded
params_data_size: holds the size of params_data (and will be replaced by the actual size of parameters)
This function will export the given dh parameters to a PKCS3 DHParams structure. This is the format generated by "openssl dhparam" tool. If the buffer provided is not long enough to hold the output, then GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN DH PARAMETERS".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
params: Holds the DH parameters
prime: will hold the new prime
generator: will hold the new generator
bits: if non null will hold the secret key’s number of bits
This function will export the pair of prime and generator for use
in the Diffie-Hellman key exchange. The new parameters will be
allocated using gnutls_malloc()
and will be stored in the
appropriate datum.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
params: Is the structure that the DH parameters will be stored
bits: is the prime’s number of bits
This function will generate a new pair of prime and generator for use in
the Diffie-Hellman key exchange. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
This function is normally slow.
Do not set the number of bits directly, use gnutls_sec_param_to_pk_bits()
to
get bits for GNUTLS_PK_DSA
.
Also note that the DH parameters are only useful to servers.
Since clients use the parameters sent by the server, it’s of
no use to call this in client side.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
params: A structure where the parameters will be copied to
pkcs3_params: should contain a PKCS3 DHParams structure PEM or DER encoded
format: the format of params. PEM or DER.
This function will extract the DHParams found in a PKCS3 formatted structure. This is the format generated by "openssl dhparam" tool.
If the structure is PEM encoded, it should have a header of "BEGIN DH PARAMETERS".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
dh_params: Is a structure that will hold the prime numbers
prime: holds the new prime
generator: holds the new generator
This function will replace the pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters should be stored in the appropriate gnutls_datum.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
dh_params: Is a structure that will hold the prime numbers
This function will initialize the DH parameters structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
session: is a gnutls_session_t
structure.
bits: is the number of bits
This function sets the number of bits, for use in a Diffie-Hellman key exchange. This is used both in DH ephemeral and DH anonymous cipher suites. This will set the minimum size of the prime that will be used for the handshake.
In the client side it sets the minimum accepted number of bits. If
a server sends a prime with less bits than that
GNUTLS_E_DH_PRIME_UNACCEPTABLE
will be returned by the handshake.
Note that values lower than 512 bits may allow decryption of the exchanged data.
This function has no effect in server side.
session: is a gnutls_session_t
structure.
Returns the currently used elliptic curve. Only valid when using an elliptic curve ciphersuite.
Returns: the currently used curve, a gnutls_ecc_curve_t
type.
Since: 3.0
curve: is an ECC curve
Convert a gnutls_ecc_curve_t
value to a string.
Returns: a string that contains the name of the specified
curve or NULL
.
Since: 3.0
curve: is an ECC curve
Returns the size in bytes of the curve.
Returns: a the size or (0).
Since: 3.0
Get the list of supported elliptic curves.
This function is not thread safe.
Returns: Return a (0)-terminated list of gnutls_ecc_curve_t
integers indicating the available curves.
error: is a GnuTLS error code, a negative error code
If a GnuTLS function returns a negative error code you may feed that value to this function to see if the error condition is fatal. Note that you may also want to check the error code manually, since some non-fatal errors to the protocol (such as a warning alert or a rehandshake request) may be fatal for your program.
This function is only useful if you are dealing with errors from the record layer or the handshake layer.
Returns: 1 if the error code is fatal, for positive error
values,
0 is returned. For unknown error
values, -1 is returned.
err: is a negative integer
level: the alert level will be stored there
Get an alert depending on the error code returned by a gnutls
function. All alerts sent by this function should be considered
fatal. The only exception is when err
is GNUTLS_E_REHANDSHAKE
,
where a warning alert should be sent to the peer indicating that no
renegotiation will be performed.
If there is no mapping to a valid alert the alert to indicate internal error is returned.
Returns: the alert code to use for a particular error code.
algo: is a digest algorithm
data: is the data
result: is the place where the result will be copied (may be null).
result_size: should hold the size of the result. The actual size of the returned result will also be copied there.
This function will calculate a fingerprint (actually a hash), of the given data. The result is not printable data. You should convert it to hex, or to something else printable.
This is the usual way to calculate a fingerprint of an X.509 DER encoded certificate. Note however that the fingerprint of an OpenPGP is not just a hash and cannot be calculated with this function.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
This function deinitializes the global data, that were initialized
using gnutls_global_init()
.
Note! This function is not thread safe. See the discussion for
gnutls_global_init()
for more information.
This function initializes the global data to defaults.
In order to free resources you may call gnutls_global_deinit()
when gnutls usage is no longer needed.
Note that this function will also initialize the underlying crypto backend, if it has not been initialized before.
This function increments a global counter, so that
gnutls_global_deinit()
only releases resources when it has been
called as many times as gnutls_global_init()
. This is useful when
GnuTLS is used by more than one library in an application. This
function can be called many times, but will only do something the
first time.
Note! This function is not thread safe. If two threads call this function simultaneously, they can cause a race between checking the global counter and incrementing it, causing both threads to execute the library initialization code. That would lead to a memory leak. To handle this, your application could invoke this function after aquiring a thread mutex. To ignore the potential memory leak is also an option.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
log_func: it is the audit log function
This is the function where you set the logging function gnutls is
going to use. This is different from gnutls_global_set_log_function()
because it will report the session of the event if any. Note that
that session might be null if there is no corresponding TLS session.
gnutls_audit_log_func
is of the form,
void (*gnutls_audit_log_func)( gnutls_session_t, int level, const char*);
Since: 3.0
log_func: it’s a log function
This is the function where you set the logging function gnutls is going to use. This function only accepts a character array. Normally you may not use this function since it is only used for debugging purposes.
gnutls_log_func
is of the form,
void (*gnutls_log_func)( int level, const char*);
level: it’s an integer from 0 to 9.
This is the function that allows you to set the log level. The level is an integer between 0 and 9. Higher values mean more verbosity. The default value is 0. Larger values should only be used with care, since they may reveal sensitive information.
Use a log level over 10 to enable all debugging options.
alloc_func: it’s the default memory allocation function. Like malloc()
.
secure_alloc_func: This is the memory allocation function that will be used for sensitive data.
is_secure_func: a function that returns 0 if the memory given is not secure. May be NULL.
realloc_func: A realloc function
free_func: The function that frees allocated data. Must accept a NULL pointer.
This is the function where you set the memory allocation functions
gnutls is going to use. By default the libc’s allocation functions
(malloc()
, free()
), are used by gnutls, to allocate both sensitive
and not sensitive data. This function is provided to set the
memory allocation functions to something other than the defaults
This function must be called before gnutls_global_init()
is called.
This function is not thread safe.
init: mutex initialization function
deinit: mutex deinitialization function
lock: mutex locking function
unlock: mutex unlocking function
With this function you are allowed to override the default mutex locks used in some parts of gnutls and dependent libraries. This function should be used if you have complete control of your program and libraries. Do not call this function from a library. Instead only initialize gnutls and the default OS mutex locks will be used.
This function must be called before gnutls_global_init()
.
Since: 2.12.0
time_func: it’s the system time function, a gnutls_time_func()
callback.
This is the function where you can override the default system time function. The application provided function should behave the same as the standard function.
Since: 2.12.0
session: is a gnutls_session_t
structure.
This function does the handshake of the TLS/SSL protocol, and initializes the TLS connection.
This function will fail if any problem is encountered, and will return a negative error code. In case of a client, if the client has asked to resume a session, but the server couldn’t, then a full handshake will be performed.
The non-fatal errors such as GNUTLS_E_AGAIN
and
GNUTLS_E_INTERRUPTED
interrupt the handshake procedure, which
should be resumed later. Call this function again, until it
returns 0; cf. gnutls_record_get_direction()
and
gnutls_error_is_fatal()
.
If this function is called by a server after a rehandshake request
then GNUTLS_E_GOT_APPLICATION_DATA
or
GNUTLS_E_WARNING_ALERT_RECEIVED
may be returned. Note that these
are non fatal errors, only in the specific case of a rehandshake.
Their meaning is that the client rejected the rehandshake request or
in the case of GNUTLS_E_GOT_APPLICATION_DATA
it might also mean that
some data were pending.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
session: is a gnutls_session_t
structure.
This function is only useful to check where the last performed handshake failed. If the previous handshake succeed or was not performed at all then no meaningful value will be returned.
Check gnutls_handshake_description_t
in gnutls.h for the
available handshake descriptions.
Returns: the last handshake message type received, a
gnutls_handshake_description_t
.
session: is a gnutls_session_t
structure.
This function is only useful to check where the last performed handshake failed. If the previous handshake succeed or was not performed at all then no meaningful value will be returned.
Check gnutls_handshake_description_t
in gnutls.h for the
available handshake descriptions.
Returns: the last handshake message type sent, a
gnutls_handshake_description_t
.
session: is a gnutls_session_t
structure.
max: is the maximum number.
This function will set the maximum size of all handshake messages.
Handshakes over this size are rejected with
GNUTLS_E_HANDSHAKE_TOO_LARGE
error code. The default value is
48kb which is typically large enough. Set this to 0 if you do not
want to set an upper limit.
The reason for restricting the handshake message sizes are to limit Denial of Service attacks.
session: is a gnutls_session_t
structure.
func: is the function to be called
This function will set a callback to be called after the client hello has been received (callback valid in server side only). This allows the server to adjust settings based on received extensions.
Those settings could be ciphersuites, requesting certificate, or anything else except for version negotiation (this is done before the hello message is parsed).
This callback must return 0 on success or a gnutls error code to terminate the handshake.
Warning: You should not use this function to terminate the handshake based on client input unless you know what you are doing. Before the handshake is finished there is no way to know if there is a man-in-the-middle attack being performed.
session: is a gnutls_session_t
structure.
allow: is an integer (0 or 1)
This function will enable or disable the use of private cipher
suites (the ones that start with 0xFF). By default or if allow
is 0 then these cipher suites will not be advertized nor used.
Currently GnuTLS does not include such cipher-suites or compression algorithms.
Enabling the private ciphersuites when talking to other than gnutls servers and clients may cause interoperability problems.
hex_data: string with data in hex format
hex_size: size of hex data
bin_data: output array with binary data
bin_size: when calling should hold maximum size of bin_data
,
on return will hold actual length of bin_data
.
Convert a buffer with hex data to binary data.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.4.0
hex_data: contain the encoded data
result: the place where decoded data will be copied
result_size: holds the size of the result
This function will decode the given encoded data, using the hex encoding used by PSK password files.
Note that hex_data should be null terminated.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the buffer given is not
long enough, or 0 on success.
data: contain the raw data
result: the place where hex data will be copied
result_size: holds the size of the result
This function will convert the given data to printable data, using the hex encoding, as used in the PSK password files.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the buffer given is not
long enough, or 0 on success.
session: is a pointer to a gnutls_session_t
structure.
flags: indicate if this session is to be used for server or client.
This function initializes the current session to null. Every
session must be initialized before use, so internal structures can
be allocated. This function allocates structures which can only
be free’d by calling gnutls_deinit()
. Returns GNUTLS_E_SUCCESS
(0) on success.
flags
can be one of GNUTLS_CLIENT
and GNUTLS_SERVER
. For a DTLS
entity, the flags GNUTLS_DATAGRAM
and GNUTLS_NONBLOCK
are
also available. The latter flag will enable a non-blocking
operation of the DTLS timers.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: is a pointer to a gnutls_datum_t
which will contain a newly
created key.
key_size: The number of bytes of the key.
Generates a random key of key_bytes
size.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
Since: 3.0
session: is a gnutls_session_t
structure.
Get currently used key exchange algorithm.
Returns: the key exchange algorithm used in the last handshake, a
gnutls_kx_algorithm_t
value.
name: is a KX name
Convert a string to a gnutls_kx_algorithm_t
value. The names are
compared in a case insensitive way.
Returns: an id of the specified KX algorithm, or GNUTLS_KX_UNKNOWN
on error.
algorithm: is a key exchange algorithm
Convert a gnutls_kx_algorithm_t
value to a string.
Returns: a pointer to a string that contains the name of the
specified key exchange algorithm, or NULL
.
Get a list of supported key exchange algorithms.
This function is not thread safe.
Returns: a (0)-terminated list of gnutls_kx_algorithm_t
integers
indicating the available key exchange algorithms.
session: is a gnutls_session_t
structure.
Get currently used MAC algorithm.
Returns: the currently used mac algorithm, a
gnutls_mac_algorithm_t
value.
name: is a MAC algorithm name
Convert a string to a gnutls_mac_algorithm_t
value. The names are
compared in a case insensitive way.
Returns: a gnutls_mac_algorithm_t
id of the specified MAC
algorithm string, or GNUTLS_MAC_UNKNOWN
on failures.
algorithm: is an encryption algorithm
Get size of MAC key.
Returns: length (in bytes) of the given MAC key size, or 0 if the given MAC algorithm is invalid.
algorithm: is a MAC algorithm
Convert a gnutls_mac_algorithm_t
value to a string.
Returns: a string that contains the name of the specified MAC
algorithm, or NULL
.
Get a list of hash algorithms for use as MACs. Note that not necessarily all MACs are supported in TLS cipher suites. For example, MD2 is not supported as a cipher suite, but is supported for other purposes (e.g., X.509 signature verification or similar).
This function is not thread safe.
Returns: Return a (0)-terminated list of gnutls_mac_algorithm_t
integers indicating the available MACs.
session: is a pointer to a gnutls_session_t
structure.
status: is one of GNUTLS_OPENPGP_CERT, or GNUTLS_OPENPGP_CERT_FINGERPRINT
This function will order gnutls to send the key fingerprint instead of the key in the initial handshake procedure. This should be used with care and only when there is indication or knowledge that the server can obtain the client’s key.
header: A null terminated string with the PEM header (eg. CERTIFICATE)
b64_data: contain the encoded data
result: the place where decoded data will be copied
result_size: holds the size of the result
This function will decode the given encoded data. If the header given is non null this function will search for "—–BEGIN header" and decode only this part. Otherwise it will decode the first PEM packet found.
Returns: On success GNUTLS_E_SUCCESS
(0) is returned,
GNUTLS_E_SHORT_MEMORY_BUFFER
is returned if the buffer given is
not long enough, or 0 on success.
header: The PEM header (eg. CERTIFICATE)
b64_data: contains the encoded data
result: the place where decoded data lie
This function will decode the given encoded data. The decoded data will be allocated, and stored into result. If the header given is non null this function will search for "—–BEGIN header" and decode only this part. Otherwise it will decode the first PEM packet found.
You should use gnutls_free()
to free the returned data.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
msg: is a message to be put in the header
data: contain the raw data
result: the place where base64 data will be copied
result_size: holds the size of the result
This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in PEM messages.
The output string will be null terminated, although the size will not include the terminating null.
Returns: On success GNUTLS_E_SUCCESS
(0) is returned,
GNUTLS_E_SHORT_MEMORY_BUFFER
is returned if the buffer given is
not long enough, or 0 on success.
msg: is a message to be put in the encoded header
data: contains the raw data
result: will hold the newly allocated encoded data
This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in PEM messages. This function will allocate the required memory to hold the encoded data.
You should use gnutls_free()
to free the returned data.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
error: is a GnuTLS error code, a negative error code
This function is like perror()
. The only difference is that it
accepts an error number returned by a gnutls function.
algorithm: is a pk algorithm
Convert a gnutls_pk_algorithm_t
value to a string.
Returns: a string that contains the name of the specified public
key algorithm, or NULL
.
algo: is a public key algorithm
bits: is the number of bits
This is the inverse of gnutls_sec_param_to_pk_bits()
. Given an algorithm
and the number of bits, it will return the security parameter. This is
a rough indication.
Returns: The security parameter.
Since: 2.12.0
name: is a string containing a public key algorithm name.
Convert a string to a gnutls_pk_algorithm_t
value. The names are
compared in a case insensitive way. For example,
gnutls_pk_get_id("RSA") will return GNUTLS_PK_RSA
.
Returns: a gnutls_pk_algorithm_t
id of the specified public key
algorithm string, or GNUTLS_PK_UNKNOWN
on failures.
Since: 2.6.0
algorithm: is a public key algorithm
Convert a gnutls_pk_algorithm_t
value to a string.
Returns: a pointer to a string that contains the name of the
specified public key algorithm, or NULL
.
Since: 2.6.0
Get a list of supported public key algorithms.
This function is not thread safe.
Returns: a (0)-terminated list of gnutls_pk_algorithm_t
integers
indicating the available ciphers.
Since: 2.6.0
pk: is a public key algorithm
hash: a hash algorithm
This function maps public key and hash algorithms combinations to signature algorithms.
Returns: return a gnutls_sign_algorithm_t
value, or GNUTLS_SIGN_UNKNOWN
on error.
session: is a gnutls_session_t
structure.
label_size: length of the label
variable.
label: label used in PRF computation, typically a short string.
server_random_first: non-0 if server random field should be first in seed
extra_size: length of the extra
variable.
extra: optional extra data to seed the PRF with.
outsize: size of pre-allocated output buffer to hold the output.
out: pre-allocate buffer to hold the generated data.
Apply the TLS Pseudo-Random-Function (PRF) on the master secret and the provided data, seeded with the client and server random fields.
The label
variable usually contain a string denoting the purpose
for the generated data. The server_random_first
indicate whether
the client random field or the server random field should be first
in the seed. Non-0 indicate that the server random field is first,
0 that the client random field is first.
The extra
variable can be used to add more data to the seed, after
the random variables. It can be used to tie make sure the
generated output is strongly connected to some additional data
(e.g., a string used in user authentication).
The output is placed in out
, which must be pre-allocated.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
session: is a gnutls_session_t
structure.
label_size: length of the label
variable.
label: label used in PRF computation, typically a short string.
seed_size: length of the seed
variable.
seed: optional extra data to seed the PRF with.
outsize: size of pre-allocated output buffer to hold the output.
out: pre-allocate buffer to hold the generated data.
Apply the TLS Pseudo-Random-Function (PRF) on the master secret and the provided data.
The label
variable usually contain a string denoting the purpose
for the generated data. The seed
usually contain data such as the
client and server random, perhaps together with some additional
data that is added to guarantee uniqueness of the output for a
particular purpose.
Because the output is not guaranteed to be unique for a particular
session unless seed
include the client random and server random
fields (the PRF would output the same data on another connection
resumed from the first one), it is not recommended to use this
function directly. The gnutls_prf()
function seed the PRF with the
client and server random fields directly, and is recommended if you
want to generate pseudo random data unique for each session.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
pcache: is a gnutls_prioritity_t
structure.
list: will point to an integer list
Get a list of available certificate types in the priority structure.
Returns: the number of certificate types, or an error code.
Since: 3.0
pcache: is a gnutls_prioritity_t
structure.
list: will point to an integer list
Get a list of available compression method in the priority structure.
Returns: the number of methods, or an error code.
Since: 3.0
priority_cache: is a gnutls_prioritity_t
structure.
Deinitializes the priority cache.
pcache: is a gnutls_prioritity_t
structure.
list: will point to an integer list
Get a list of available elliptic curves in the priority structure.
Returns: the number of curves, or an error code.
Since: 3.0
pcache: is a gnutls_prioritity_t
structure.
idx: is an index number.
sidx: internal index of cipher suite to get information about.
Provides the internal ciphersuite index to be used with
gnutls_cipher_suite_info()
. The index idx
provided is an
index kept at the priorities structure. It might be that a valid
priorities index does not correspond to a ciphersuite and in
that case GNUTLS_E_UNKNOWN_CIPHER_SUITE
will be returned.
Once the last available index is crossed then
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Returns: On success it returns GNUTLS_E_SUCCESS
(0), or a negative error value otherwise.
priority_cache: is a gnutls_prioritity_t
structure.
priorities: is a string describing priorities
err_pos: In case of an error this will have the position in the string the error occured
Sets priorities for the ciphers, key exchange methods, macs and compression methods.
The priorities
option allows you to specify a colon
separated list of the cipher priorities to enable.
Some keywords are defined to provide quick access
to common preferences.
"PERFORMANCE" means all the "secure" ciphersuites are enabled, limited to 128 bit ciphers and sorted by terms of speed performance.
"NORMAL" means all "secure" ciphersuites. The 256-bit ciphers are included as a fallback only. The ciphers are sorted by security margin.
"SECURE128" means all "secure" ciphersuites of security level 128-bit or more.
"SECURE192" means all "secure" ciphersuites of security level 192-bit or more.
"SUITEB128" means all the NSA SuiteB ciphersuites with security level of 128.
"SUITEB192" means all the NSA SuiteB ciphersuites with security level of 192.
"EXPORT" means all ciphersuites are enabled, including the low-security 40 bit ciphers.
"NONE" means nothing is enabled. This disables even protocols and compression methods.
Special keywords are "!", "-" and "+". "!" or "-" appended with an algorithm will remove this algorithm. "+" appended with an algorithm will add this algorithm.
Check the GnuTLS manual section "Priority strings" for detailed information.
Examples: "NONE:+VERS-TLS-ALL:+MAC-ALL:+RSA:+AES-128-CBC:+SIGN-ALL:+COMP-NULL"
"NORMAL:-ARCFOUR-128" means normal ciphers except for ARCFOUR-128.
"SECURE:-VERS-SSL3.0:+COMP-DEFLATE" means that only secure ciphers are enabled, SSL3.0 is disabled, and libz compression enabled.
"NONE:+VERS-TLS-ALL:+AES-128-CBC:+RSA:+SHA1:+COMP-NULL:+SIGN-RSA-SHA1",
"NONE:+VERS-TLS-ALL:+AES-128-CBC:+ECDHE-RSA:+SHA1:+COMP-NULL:+SIGN-RSA-SHA1:+CURVE-SECP256R1",
"NORMAL:COMPAT
" is the most compatible mode.
Returns: On syntax error GNUTLS_E_INVALID_REQUEST
is returned,
GNUTLS_E_SUCCESS
on success, or an error code.
pcache: is a gnutls_prioritity_t
structure.
list: will point to an integer list
Get a list of available TLS version numbers in the priority structure.
Returns: the number of protocols, or an error code.
Since: 3.0
session: is a gnutls_session_t
structure.
priority: is a gnutls_priority_t
structure.
Sets the priorities to use on the ciphers, key exchange methods, macs and compression methods.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
session: is a gnutls_session_t
structure.
priorities: is a string describing priorities
err_pos: In case of an error this will have the position in the string the error occured
Sets the priorities to use on the ciphers, key exchange methods,
macs and compression methods. This function avoids keeping a
priority cache and is used to directly set string priorities to a
TLS session. For documentation check the gnutls_priority_init()
.
Returns: On syntax error GNUTLS_E_INVALID_REQUEST
is returned,
GNUTLS_E_SUCCESS
on success, or an error code.
pcache: is a gnutls_prioritity_t
structure.
list: will point to an integer list
Get a list of available signature algorithms in the priority structure.
Returns: the number of algorithms, or an error code.
Since: 3.0
name: is a protocol name
The names are compared in a case insensitive way.
Returns: an id of the specified protocol, or
GNUTLS_VERSION_UNKNOWN
on error.
version: is a (gnutls) version number
Convert a gnutls_protocol_t
value to a string.
Returns: a string that contains the name of the specified TLS
version (e.g., "TLS1.0"), or NULL
.
session: is a gnutls_session_t
structure.
Get TLS version, a gnutls_protocol_t
value.
Returns: The version of the currently used protocol.
Get a list of supported protocols, e.g. SSL 3.0, TLS 1.0 etc.
This function is not thread safe.
Returns: a (0)-terminated list of gnutls_protocol_t
integers
indicating the available protocols.
sc: is a pointer to a gnutls_psk_server_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
sc: is a pointer to a gnutls_psk_server_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls session
The PSK identity hint may give the client help in deciding which username to use. This should only be called in case of PSK authentication and in case of a client.
Returns: the identity hint of the peer, or NULL
in case of an error.
Since: 2.4.0
sc: is a gnutls_psk_client_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.
sc: is a gnutls_psk_server_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.
session: is a gnutls session
This should only be called in case of PSK authentication and in case of a server.
Returns: the username of the peer, or NULL
in case of an error.
res: is a gnutls_psk_client_credentials_t
structure.
username: is the user’s zero-terminated userid
key: is the user’s key
flags: indicate the format of the key, either
GNUTLS_PSK_KEY_RAW
or GNUTLS_PSK_KEY_HEX
.
This function sets the username and password, in a
gnutls_psk_client_credentials_t structure. Those will be used in
PSK authentication. username
should be an ASCII string or UTF-8
strings prepared using the "SASLprep" profile of "stringprep". The
key can be either in raw byte format or in Hex format (without the
0x prefix).
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
cred: is a gnutls_psk_server_credentials_t
structure.
func: is the callback function
This function can be used to set a callback to retrieve the username and password for client PSK authentication. The callback’s function form is: int (*callback)(gnutls_session_t, char** username, gnutls_datum_t* key);
The username
and key
->data must be allocated using gnutls_malloc()
.
username
should be ASCII strings or UTF-8 strings prepared using
the "SASLprep" profile of "stringprep".
The callback function will be called once per handshake.
The callback function should return 0 on success. -1 indicates an error.
res: is a gnutls_psk_server_credentials_t structure
func: is the function to be called
This function will set a callback in order for the server to get
the Diffie-Hellman or RSA parameters for PSK authentication. The
callback should return GNUTLS_E_SUCCESS
(0) on success.
res: is a gnutls_psk_server_credentials_t
structure.
password_file: is the PSK password file (passwd.psk)
This function sets the password file, in a
gnutls_psk_server_credentials_t
structure. This password file
holds usernames and keys and will be used for PSK authentication.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
cred: is a gnutls_psk_server_credentials_t
structure.
func: is the callback function
This function can be used to set a callback to retrieve the user’s PSK credentials. The callback’s function form is: int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t* key);
username
contains the actual username.
The key
must be filled in using the gnutls_malloc()
.
In case the callback returned a negative number then gnutls will assume that the username does not exist.
The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error.
res: is a gnutls_psk_server_credentials_t
structure.
hint: is the PSK identity hint string
This function sets the identity hint, in a
gnutls_psk_server_credentials_t
structure. This hint is sent to
the client to help it chose a good PSK credential (i.e., username
and password).
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
Since: 2.4.0
res: is a gnutls_psk_server_credentials_t structure
dh_params: is a structure that holds Diffie-Hellman parameters.
This function will set the Diffie-Hellman parameters for an anonymous server to use. These parameters will be used in Diffie-Hellman exchange with PSK cipher suites.
res: is a gnutls_certificate_credentials_t
structure
func: is the function to be called
This function will set a callback in order for the server to get
the Diffie-Hellman parameters for PSK authentication. The callback
should return GNUTLS_E_SUCCESS
(0) on success.
type: The type of the random art
key_type: The type of the key (RSA, DSA etc.)
key_size: The size of the key in bits
fpr: The fingerprint of the key
fpr_size: The size of the fingerprint
art: The returned random art
This function will convert a given fingerprint to an "artistic"
image. The returned image is allocated using gnutls_malloc()
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls_session_t
structure.
This function checks if there are unread data
in the gnutls buffers. If the return value is
non-zero the next call to gnutls_record_recv()
is guarranteed not to block.
Returns: Returns the size of the data or zero.
session: is a gnutls_session_t
structure.
Used to disabled padding in TLS 1.0 and above. Normally you do not need to use this function, but there are buggy clients that complain if a server pads the encrypted data. This of course will disable protection against statistical attacks on the data.
Normally only servers that require maximum compatibility with everything out there, need to call this function.
session: is a gnutls_session_t
structure.
This function provides information about the internals of the
record protocol and is only useful if a prior gnutls function call
(e.g. gnutls_handshake()
) was interrupted for some reason, that
is, if a function returned GNUTLS_E_INTERRUPTED
or
GNUTLS_E_AGAIN
. In such a case, you might want to call select()
or poll()
before calling the interrupted gnutls function again. To
tell you whether a file descriptor should be selected for either
reading or writing, gnutls_record_get_direction()
returns 0 if the
interrupted function was trying to read data, and 1 if it was
trying to write data.
Returns: 0 if trying to read data, 1 if trying to write data.
session: is a gnutls_session_t
structure.
Get the record size. The maximum record size is negotiated by the client after the first handshake message.
Returns: The maximum record packet size in this connection.
session: is a gnutls_session_t
structure.
data: the buffer that the data will be read into
data_size: the number of requested bytes
This function has the similar semantics with recv()
. The only
difference is that it accepts a GnuTLS session, and uses different
error codes.
In the special case that a server requests a renegotiation, the
client may receive an error code of GNUTLS_E_REHANDSHAKE
. This
message may be simply ignored, replied with an alert
GNUTLS_A_NO_RENEGOTIATION
, or replied with a new handshake,
depending on the client’s will.
If EINTR
is returned by the internal push function (the default
is recv()
) then GNUTLS_E_INTERRUPTED
will be returned. If
GNUTLS_E_INTERRUPTED
or GNUTLS_E_AGAIN
is returned, you must
call this function again to get the data. See also
gnutls_record_get_direction()
.
A server may also receive GNUTLS_E_REHANDSHAKE
when a client has
initiated a handshake. In that case the server can only initiate a
handshake or terminate the connection.
Returns: The number of bytes received and zero on EOF (for stream
connections). A negative error code is returned in case of an error.
The number of bytes received might be less than the requested data_size
.
session: is a gnutls_session_t
structure.
data: the buffer that the data will be read into
data_size: the number of requested bytes
seq: is the packet’s 64-bit sequence number. Should have space for 8 bytes.
This function is the same as gnutls_record_recv()
, except that
it returns in addition to data, the sequence number of the data.
This is useful in DTLS where record packets might be received
out-of-order. The returned 8-byte sequence number is an
integer in big-endian format and should be
treated as a unique message identification.
Returns: The number of bytes received and zero on EOF. A negative
error code is returned in case of an error. The number of bytes
received might be less than data_size
.
Since: 3.0
session: is a gnutls_session_t
structure.
data: contains the data to send
data_size: is the length of the data
This function has the similar semantics with send()
. The only
difference is that it accepts a GnuTLS session, and uses different
error codes.
Note that if the send buffer is full, send()
will block this
function. See the send()
documentation for full information. You
can replace the default push function by using
gnutls_transport_set_ptr2()
with a call to send()
with a
MSG_DONTWAIT flag if blocking is a problem.
If the EINTR is returned by the internal push function (the
default is send()
) then GNUTLS_E_INTERRUPTED
will be returned. If
GNUTLS_E_INTERRUPTED
or GNUTLS_E_AGAIN
is returned, you must
call this function again, with the same parameters; alternatively
you could provide a NULL
pointer for data, and 0 for
size. cf. gnutls_record_get_direction()
. The errno value EMSGSIZE
maps to GNUTLS_E_LARGE_PACKET
.
Returns: The number of bytes sent, or a negative error code. The
number of bytes sent might be less than data_size
. The maximum
number of bytes this function can send in a single call depends
on the negotiated maximum record size.
session: is a gnutls_session_t
structure.
size: is the new size
This function sets the maximum record packet size in this connection. This property can only be set to clients. The server may choose not to accept the requested size.
Acceptable values are 512(=2^9), 1024(=2^10), 2048(=2^11) and 4096(=2^12). The requested record size does get in effect immediately only while sending data. The receive part will take effect after a successful handshake.
This function uses a TLS extension called ’max record size’. Not all TLS implementations use or even understand this extension.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
session: is a gnutls_session_t
structure.
This function will renegotiate security parameters with the client. This should only be called in case of a server.
This message informs the peer that we want to renegotiate parameters (perform a handshake).
If this function succeeds (returns 0), you must call the
gnutls_handshake()
function in order to negotiate the new
parameters.
Since TLS is full duplex some application data might have been
sent during peer’s processing of this message. In that case
one should call gnutls_record_recv()
until GNUTLS_E_REHANDSHAKE
is returned to clear any pending data. Care must be taken if
rehandshake is mandatory to terminate if it does not start after
some threshold.
If the client does not wish to renegotiate parameters he will
should with an alert message, thus the return code will be
GNUTLS_E_WARNING_ALERT_RECEIVED
and the alert will be
GNUTLS_A_NO_RENEGOTIATION
. A client may also choose to ignore
this message.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
session: is a gnutls_session_t
structure.
Can be used to check whether safe renegotiation is being used in the current session.
Returns: 0 when safe renegotiation is not used and non (0) when safe renegotiation is used.
Since: 2.10.0
param: is a security parameter
Convert a gnutls_sec_param_t
value to a string.
Returns: a pointer to a string that contains the name of the
specified security level, or NULL
.
Since: 2.12.0
algo: is a public key algorithm
param: is a security parameter
When generating private and public key pairs a difficult question is which size of "bits" the modulus will be in RSA and the group size in DSA. The easy answer is 1024, which is also wrong. This function will convert a human understandable security parameter to an appropriate size for the specific algorithm.
Returns: The number of bits, or (0).
Since: 2.12.0
session: is a gnutls_session_t
structure.
data: will hold the data
data_length: will hold the data length. Must hold the maximum size of data.
type: will hold the server name indicator type
indx: is the index of the server_name
This function will allow you to get the name indication (if any), a client has sent. The name indication may be any of the enumeration gnutls_server_name_type_t.
If type
is GNUTLS_NAME_DNS, then this function is to be used by
servers that support virtual hosting, and the data will be a null
terminated UTF-8 string.
If data
has not enough size to hold the server name
GNUTLS_E_SHORT_MEMORY_BUFFER is returned, and data_length
will
hold the required size.
index
is used to retrieve more than one server names (if sent by
the client). The first server name has an index of 0, the second 1
and so on. If no name with the given index exists
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE is returned.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
session: is a gnutls_session_t
structure.
type: specifies the indicator type
name: is a string that contains the server name.
name_length: holds the length of name
This function is to be used by clients that want to inform (via a TLS extension mechanism) the server of the name they connected to. This should be used by clients that connect to servers that do virtual hosting.
The value of name
depends on the type
type. In case of
GNUTLS_NAME_DNS
, an ASCII (0)-terminated domain name string,
without the trailing dot, is expected. IPv4 or IPv6 addresses are
not permitted.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
session: is a gnutls_session_t
structure.
cbtype: an gnutls_channel_binding_t
enumeration type
cb: output buffer array with data
Extract given channel binding data of the cbtype
(e.g.,
GNUTLS_CB_TLS_UNIQUE
) type.
Returns: GNUTLS_E_SUCCESS
on success,
GNUTLS_E_UNIMPLEMENTED_FEATURE
if the cbtype
is unsupported,
GNUTLS_E_CHANNEL_BINDING_NOT_AVAILABLE
if the data is not
currently available, or an error code.
Since: 2.12.0
session: is a gnutls_session_t
structure.
This function can be used to disable certain (security) features in
TLS in order to maintain maximum compatibility with buggy
clients. It is equivalent to calling:
gnutls_record_disable_padding()
Normally only servers that require maximum compatibility with everything out there, need to call this function.
session: is a gnutls_session_t
structure.
session_data: is a pointer to space to hold the session.
session_data_size: is the session_data’s size, or it will be set by the function.
Returns all session parameters, in order to support resuming. The
client should call this, and keep the returned session, if he
wants to resume that current version later by calling
gnutls_session_set_data()
This function must be called after a
successful handshake.
Resuming sessions is really useful and speedups connections after a successful one.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls_session_t
structure.
data: is a pointer to a datum that will hold the session.
Returns all session parameters, in order to support resuming. The
client should call this, and keep the returned session, if he wants
to resume that current version later by calling
gnutls_session_set_data()
. This function must be called after a
successful handshake. The returned datum must be freed with
gnutls_free()
.
Resuming sessions is really useful and speedups connections after a successful one.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls_session_t
structure.
session_id: is a pointer to space to hold the session id.
session_id_size: is the session id’s size, or it will be set by the function.
Returns the current session id. This can be used if you want to check if the next session you tried to resume was actually resumed. This is because resumed sessions have the same sessionID with the original session.
Session id is some data set by the server, that identify the current session. In TLS 1.0 and SSL 3.0 session id is always less than 32 bytes.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls_session_t
structure.
Get user pointer for session. Useful in callbacks. This is the
pointer set with gnutls_session_set_ptr()
.
Returns: the user given pointer from the session structure, or
NULL
if it was never set.
session: is a gnutls_session_t
structure.
client: the client part of the random
server: the server part of the random
This functions returns pointers to the client and server random fields used in the TLS handshake. The pointers are not to be modified or deallocated.
If a client random value has not yet been established, the output will be garbage.
Since: 3.0
session: is a gnutls_session_t
structure.
Check whether session is resumed or not.
Returns: non zero if this session is resumed, or a zero if this is a new session.
session: is a gnutls_session_t
structure.
Check whether the client has asked for session resumption. This function is valid only on server side.
Returns: non zero if session resumption was asked, or a zero if not.
session: is a gnutls_session_t
structure.
session_data: is a pointer to space to hold the session.
session_data_size: is the session’s size
Sets all session parameters, in order to resume a previously
established session. The session data given must be the one
returned by gnutls_session_get_data()
. This function should be
called before gnutls_handshake()
.
Keep in mind that session resuming is advisory. The server may choose not to resume the session, thus a full handshake will be performed.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls_session_t
structure.
entity: GNUTLS_SERVER or GNUTLS_CLIENT
version: the TLS protocol version
kx: the key exchange method
cipher: the cipher
mac: the MAC algorithm
comp: the compression method
master: the master key to use
session_id: the session identifier
This function sets the premaster secret in a session. This is
a function intended for exceptional uses. Do not use this
function unless you are implementing a legacy protocol.
Use gnutls_session_set_data()
instead.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
session: is a gnutls_session_t
structure.
ptr: is the user pointer
This function will set (associate) the user given pointer ptr
to
the session structure. This is pointer can be accessed with
gnutls_session_get_ptr()
.
session: is a gnutls_session_t
structure.
Request that the client should attempt session resumption using SessionTicket.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
Since: 2.10.0
session: is a gnutls_session_t
structure.
key: key to encrypt session parameters.
Request that the server should attempt session resumption using
SessionTicket. key
must be initialized with
gnutls_session_ticket_key_generate()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
Since: 2.10.0
key: is a pointer to a gnutls_datum_t
which will contain a newly
created key.
Generate a random key to encrypt security parameters within SessionTicket.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
Since: 2.10.0
session: is a gnutls_session_t
structure.
Sets some default priority on the ciphers, key exchange methods, macs and compression methods.
This is the same as calling:
gnutls_priority_set_direct (session, "NORMAL", NULL);
This function is kept around for backwards compatibility, but
because of its wide use it is still fully supported. If you wish
to allow users to provide a string that specify which ciphers to
use (which is recommended), you should use
gnutls_priority_set_direct()
or gnutls_priority_set()
instead.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
session: is a gnutls_session_t
structure.
indx: is an index of the signature algorithm to return
algo: the returned certificate type will be stored there
Returns the signature algorithm specified by index that was
requested by the peer. If the specified index has no data available
this function returns GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
. If
the negotiated TLS version does not support signature algorithms
then GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned even
for the first index. The first index is 0.
This function is useful in the certificate callback functions to assist in selecting the correct certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
Since: 2.10.0
name: is a MAC algorithm name
The names are compared in a case insensitive way.
Returns: return a gnutls_sign_algorithm_t
value corresponding to
the specified cipher, or GNUTLS_SIGN_UNKNOWN
on error.
algorithm: is a sign algorithm
Convert a gnutls_sign_algorithm_t
value to a string.
Returns: a string that contains the name of the specified sign
algorithm, or NULL
.
Get a list of supported public key signature algorithms.
Returns: a (0)-terminated list of gnutls_sign_algorithm_t
integers indicating the available ciphers.
sc: is a pointer to a gnutls_srp_server_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
sc: is a pointer to a gnutls_srp_server_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to allocate it.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
b64_data: contain the encoded data
result: the place where decoded data will be copied
result_size: holds the size of the result
This function will decode the given encoded data, using the base64 encoding found in libsrp.
Note that b64_data
should be null terminated.
Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the buffer given is not
long enough, or 0 on success.
b64_data: contains the encoded data
result: the place where decoded data lie
This function will decode the given encoded data. The decoded data will be allocated, and stored into result. It will decode using the base64 algorithm as used in libsrp.
You should use gnutls_free()
to free the returned data.
Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.
Returns: 0 on success, or an error code.
data: contain the raw data
result: the place where base64 data will be copied
result_size: holds the size of the result
This function will convert the given data to printable data, using the base64 encoding, as used in the libsrp. This is the encoding used in SRP password files. If the provided buffer is not long enough GNUTLS_E_SHORT_MEMORY_BUFFER is returned.
Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the buffer given is not
long enough, or 0 on success.
data: contains the raw data
result: will hold the newly allocated encoded data
This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in SRP password files. This function will allocate the required memory to hold the encoded data.
You should use gnutls_free()
to free the returned data.
Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.
Returns: 0 on success, or an error code.
sc: is a gnutls_srp_client_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.
sc: is a gnutls_srp_server_credentials_t
structure.
This structure is complex enough to manipulate directly thus this helper function is provided in order to free (deallocate) it.
session: is a gnutls session
This function will return the username of the peer. This should only be called in case of SRP authentication and in case of a server. Returns NULL in case of an error.
Returns: SRP username of the peer, or NULL in case of error.
res: is a gnutls_srp_client_credentials_t
structure.
username: is the user’s userid
password: is the user’s password
This function sets the username and password, in a
gnutls_srp_client_credentials_t
structure. Those will be used in
SRP authentication. username
and password
should be ASCII
strings or UTF-8 strings prepared using the "SASLprep" profile of
"stringprep".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
cred: is a gnutls_srp_server_credentials_t
structure.
func: is the callback function
This function can be used to set a callback to retrieve the username and password for client SRP authentication. The callback’s function form is:
int (*callback)(gnutls_session_t, char** username, char**password);
The username
and password
must be allocated using
gnutls_malloc()
. username
and password
should be ASCII strings
or UTF-8 strings prepared using the "SASLprep" profile of
"stringprep".
The callback function will be called once per handshake before the initial hello message is sent.
The callback should not return a negative error code the second time called, since the handshake procedure will be aborted.
The callback function should return 0 on success. -1 indicates an error.
session: is a gnutls_session_t
structure.
bits: is the number of bits
This function sets the minimum accepted number of bits, for use in an SRP key exchange. If zero, the default 2048 bits will be used.
In the client side it sets the minimum accepted number of bits. If
a server sends a prime with less bits than that
GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER
will be returned by the
handshake.
This function has no effect in server side.
Since: 2.6.0
res: is a gnutls_srp_server_credentials_t
structure.
password_file: is the SRP password file (tpasswd)
password_conf_file: is the SRP password conf file (tpasswd.conf)
This function sets the password files, in a
gnutls_srp_server_credentials_t
structure. Those password files
hold usernames and verifiers and will be used for SRP
authentication.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
cred: is a gnutls_srp_server_credentials_t
structure.
func: is the callback function
This function can be used to set a callback to retrieve the user’s SRP credentials. The callback’s function form is:
int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t* salt, gnutls_datum_t *verifier, gnutls_datum_t* g, gnutls_datum_t* n);
username
contains the actual username.
The salt
, verifier
, generator
and prime
must be filled
in using the gnutls_malloc()
. For convenience prime
and generator
may also be one of the static parameters defined in gnutls.h.
In case the callback returned a negative number then gnutls will assume that the username does not exist.
In order to prevent attackers from guessing valid usernames, if a user does not exist, g and n values should be filled in using a random user’s parameters. In that case the callback must return the special value (1).
The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error.
username: is the user’s name
password: is the user’s password
salt: should be some randomly generated bytes
generator: is the generator of the group
prime: is the group’s prime
res: where the verifier will be stored.
This function will create an SRP verifier, as specified in
RFC2945. The prime
and generator
should be one of the static
parameters defined in gnutls/gnutls.h or may be generated.
The verifier will be allocated with gnutls_malloc
() and will be stored in
res
using binary format.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or an
error code.
db_name: A file specifying the stored keys (use NULL for the default)
tdb: A storage structure or NULL to use the default
host: The peer’s name
service: non-NULL if this key is specific to a service (e.g. http)
hash_algo: The hash algorithm type
hash: The raw hash
expiration: The expiration time (use 0 to disable expiration)
flags: should be 0.
This function will store the provided hash commitment to the list of stored public keys. The key with the given hash will be considered valid until the provided expiration time.
The store
variable if non-null specifies a custom backend for
the storage of entries. If it is NULL then the
default file backend will be used.
Note that this function is not thread safe with the default backend.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
db_name: A file specifying the stored keys (use NULL for the default)
tdb: A storage structure or NULL to use the default
host: The peer’s name
service: non-NULL if this key is specific to a service (e.g. http)
cert_type: The type of the certificate
cert: The data of the certificate
expiration: The expiration time (use 0 to disable expiration)
flags: should be 0.
This function will store the provided certificate to the list of stored public keys. The key will be considered valid until the provided expiration time.
The store
variable if non-null specifies a custom backend for
the storage of entries. If it is NULL then the
default file backend will be used.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
error: is a GnuTLS error code, a negative error code
This function is similar to strerror. The difference is that it
accepts an error number returned by a gnutls function; In case of
an unknown error a descriptive string is sent instead of NULL
.
Error codes are always a negative error code.
Returns: A string explaining the GnuTLS error message.
error: is an error returned by a gnutls function.
Return the GnuTLS error code define as a string. For example, gnutls_strerror_name (GNUTLS_E_DH_PRIME_UNACCEPTABLE) will return the string "GNUTLS_E_DH_PRIME_UNACCEPTABLE".
Returns: A string corresponding to the symbol name of the error code.
Since: 2.6.0
type: is a supplemental data format type
Convert a gnutls_supplemental_data_format_type_t
value to a
string.
Returns: a string that contains the name of the specified
supplemental data format type, or NULL
for unknown types.
tdb: The structure to be deinitialized
This function will deinitialize a public key trust storage structure.
tdb: The structure to be initialized
This function will initialize a public key trust storage structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
tdb: The trust storage
cstore: The commitment storage function
This function will associate a commitment (hash) storage function with the trust storage structure. The function is of the following form.
gnutls_tdb_store_commitment_func(const char* db_name, const char* host, const char* service, time_t expiration, gnutls_digest_algorithm_t, const gnutls_datum_t* hash);
tdb: The trust storage
store: The storage function
This function will associate a storage function with the trust storage structure. The function is of the following form.
gnutls_tdb_store_func(const char* db_name, const char* host, const char* service, time_t expiration, const gnutls_datum_t* pubkey);
tdb: The trust storage
verify: The verification function
This function will associate a retrieval function with the trust storage structure. The function is of the following form.
gnutls_tdb_verify_func(const char* db_name, const char* host, const char* service, const gnutls_datum_t* pubkey);
session: is a gnutls_session_t
structure.
Used to get the first argument of the transport function (like
PUSH and PULL). This must have been set using
gnutls_transport_set_ptr()
.
Returns: The first argument of the transport function.
session: is a gnutls_session_t
structure.
recv_ptr: will hold the value for the pull function
send_ptr: will hold the value for the push function
Used to get the arguments of the transport functions (like PUSH
and PULL). These should have been set using
gnutls_transport_set_ptr2()
.
session: is a gnutls_session_t
structure.
err: error value to store in session-specific errno variable.
Store err
in the session-specific errno variable. Useful values
for err
is EAGAIN and EINTR, other values are treated will be
treated as real errors in the push/pull function.
This function is useful in replacement push and pull functions set by
gnutls_transport_set_push_function()
and
gnutls_transport_set_pull_function()
under Windows, where the
replacements may not have access to the same errno
variable that is used by GnuTLS (e.g., the application is linked to
msvcr71.dll and gnutls is linked to msvcrt.dll).
session: is a gnutls_session_t
structure.
errno_func: a callback function similar to write()
This is the function where you set a function to retrieve errno after a failed push or pull operation.
errno_func
is of the form,
int (*gnutls_errno_func)(gnutls_transport_ptr_t);
and should return the errno.
Since: 2.12.0
session: is a gnutls_session_t
structure.
ptr: is the value.
Used to set the first argument of the transport function (for push and pull callbacks). In berkeley style sockets this function will set the connection descriptor.
session: is a gnutls_session_t
structure.
recv_ptr: is the value for the pull function
send_ptr: is the value for the push function
Used to set the first argument of the transport function (for push and pull callbacks). In berkeley style sockets this function will set the connection descriptor. With this function you can use two different pointers for receiving and sending.
session: is a gnutls_session_t
structure.
pull_func: a callback function similar to read()
This is the function where you set a function for gnutls to receive data. Normally, if you use berkeley style sockets, do not need to use this function since the default recv(2) will probably be ok. The callback should return 0 on connection termination, a positive number indicating the number of bytes received, and -1 on error.
gnutls_pull_func
is of the form,
ssize_t (*gnutls_pull_func)(gnutls_transport_ptr_t, void*, size_t);
session: is a gnutls_session_t
structure.
func: a callback function
This is the function where you set a function for gnutls to know
whether data are ready to be received. It should wait for data a
given time frame in milliseconds. The callback should return 0 on
timeout, a positive number if data can be received, and -1 on error.
You’ll need to override this function if select()
is not suitable
for the provided transport calls.
The callback function is used in DTLS only.
gnutls_pull_timeout_func
is of the form,
ssize_t (*gnutls_pull_timeout_func)(gnutls_transport_ptr_t, unsigned int ms);
Since: 3.0
session: is a gnutls_session_t
structure.
push_func: a callback function similar to write()
This is the function where you set a push function for gnutls to use in order to send data. If you are going to use berkeley style sockets, you do not need to use this function since the default send(2) will probably be ok. Otherwise you should specify this function for gnutls to be able to send data. The callback should return a positive number indicating the bytes sent, and -1 on error.
push_func
is of the form,
ssize_t (*gnutls_push_func)(gnutls_transport_ptr_t, const void*, size_t);
session: is a gnutls_session_t
structure.
vec_func: a callback function similar to writev()
Using this function you can override the default writev(2)
function for gnutls to send data. Setting this callback
instead of gnutls_transport_set_push_function()
is recommended
since it introduces less overhead in the TLS handshake process.
vec_func
is of the form,
ssize_t (*gnutls_vec_push_func) (gnutls_transport_ptr_t, const giovec_t * iov, int iovcnt);
Since: 2.12.0
db_name: A file specifying the stored keys (use NULL for the default)
tdb: A storage structure or NULL to use the default
host: The peer’s name
service: non-NULL if this key is specific to a service (e.g. http)
cert_type: The type of the certificate
cert: The raw (der) data of the certificate
flags: should be 0.
This function will try to verify the provided certificate using
a list of stored public keys. The service
field if non-NULL should
be a port number.
The retrieve
variable if non-null specifies a custom backend for
the retrieval of entries. If it is NULL then the
default file backend will be used. In POSIX-like systems the
file backend uses the $HOME/.gnutls/known_hosts file.
Note that if the custom storage backend is provided the
retrieval function should return GNUTLS_E_CERTIFICATE_KEY_MISMATCH
if the host/service pair is found but key doesn’t match,
GNUTLS_E_NO_CERTIFICATE_FOUND
if no such host/service with
the given key is found, and 0 if it was found. The storage
function should return 0 on success.
Returns: If no associated public key is found
then GNUTLS_E_NO_CERTIFICATE_FOUND
will be returned. If a key
is found but does not match GNUTLS_E_CERTIFICATE_KEY_MISMATCH
is returned. On success, GNUTLS_E_SUCCESS
(0) is returned,
or a negative error value on other errors.
Since: 3.0
Next: X509 certificate API, Previous: Core TLS API, Up: API reference [Contents][Index]
The prototypes for the following functions lie in gnutls/dtls.h.
key: is a random key to be used at cookie generation
client_data: contains data identifying the client (i.e. address)
client_data_size: The size of client’s data
prestate: The previous cookie returned by gnutls_dtls_cookie_verify()
ptr: A transport pointer to be used by push_func
push_func: A function that will be used to reply
This function can be used to prevent denial of service
attacks to a DTLS server by requiring the client to
reply using a cookie sent by this function. That way
it can be ensured that a client we allocated resources
for (i.e. gnutls_session_t
) is the one that the
original incoming packet was originated from.
Returns: the number of bytes sent, or a negative error code.
Since: 3.0
key: is a random key to be used at cookie generation
client_data: contains data identifying the client (i.e. address)
client_data_size: The size of client’s data
_msg: An incoming message that initiates a connection.
msg_size: The size of the message.
prestate: The cookie of this client.
This function will verify an incoming message for
a valid cookie. If a valid cookie is returned then
it should be associated with the session using
gnutls_dtls_prestate_set()
;
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
Since: 3.0
session: is a gnutls_session_t
structure.
This function will return the actual maximum transfer unit for application data. I.e. DTLS headers are subtracted from the actual MTU.
Returns: the maximum allowed transfer unit.
Since: 3.0
session: is a gnutls_session_t
structure.
This function will return the MTU size as set with
gnutls_dtls_set_mtu()
. This is not the actual MTU
of data you can transmit. Use gnutls_dtls_get_data_mtu()
for that reason.
Returns: the set maximum transfer unit.
Since: 3.0
session: is a gnutls_session_t
structure.
This function will return the milliseconds remaining
for a retransmission of the previously sent handshake
message. This function is useful when DTLS is used in
non-blocking mode, to estimate when to call gnutls_handshake()
if no packets have been received.
Returns: the remaining time in milliseconds.
Since: 3.0
session: a new session
prestate: contains the client’s prestate
This function will associate the prestate acquired by the cookie authentication with the client, with the newly established session.
Since: 3.0
session: is a gnutls_session_t
structure.
mtu: The maximum unencrypted transfer unit of the session
This function will set the maximum size of the *unencrypted* records
which will be sent over a DTLS session. It is equivalent to calculating
the DTLS packet overhead with the current encryption parameters, and
calling gnutls_dtls_set_mtu()
with that value. In particular, this means
that you may need to call this function again after any negotiation or
renegotiation, in order to ensure that the MTU is still sufficient to
account for the new protocol overhead.
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
Since: 3.1
session: is a gnutls_session_t
structure.
mtu: The maximum transfer unit of the transport
This function will set the maximum transfer unit of the transport that DTLS packets are sent over. Note that this should exclude the IP (or IPv6) and UDP headers. So for DTLS over IPv6 on an Ethenet device with MTU 1500, the DTLS MTU set with this function would be 1500 - 40 (IPV6 header) - 8 (UDP header) = 1452.
Since: 3.0
session: is a gnutls_session_t
structure.
retrans_timeout: The time at which a retransmission will occur in milliseconds
total_timeout: The time at which the connection will be aborted, in milliseconds.
This function will set the timeouts required for the DTLS handshake
protocol. The retransmission timeout is the time after which a
message from the peer is not received, the previous messages will
be retransmitted. The total timeout is the time after which the
handshake will be aborted with GNUTLS_E_TIMEDOUT
.
The DTLS protocol recommends the values of 1 sec and 60 seconds respectively.
If the retransmission timeout is zero then the handshake will operate
in a non-blocking way, i.e., return GNUTLS_E_AGAIN
.
Since: 3.0
session: is a gnutls_session_t
structure.
Returns the number of discarded packets in a DTLS connection.
Returns: The number of discarded packets.
Since: 3.0
Next: OCSP API, Previous: Datagram TLS API, Up: API reference [Contents][Index]
The following functions are to be used for X.509 certificate handling. Their prototypes lie in gnutls/x509.h.
pkcs7: The structure to be initialized
This function will deinitialize a PKCS7 structure.
pkcs7: should contain a gnutls_pkcs7_t
structure
indx: the index of the crl to delete
This function will delete a crl from a PKCS7 or RFC2630 crl set. Index starts from 0. Returns 0 on success.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: should contain a gnutls_pkcs7_t structure
indx: the index of the certificate to delete
This function will delete a certificate from a PKCS7 or RFC2630 certificate set. Index starts from 0. Returns 0 on success.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: Holds the pkcs7 structure
format: the format of output params. One of PEM or DER.
output_data: will contain a structure PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the pkcs7 structure to DER or PEM format.
If the buffer provided is not long enough to hold the output, then
* output_data_size
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN PKCS7".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: should contain a gnutls_pkcs7_t structure
This function will return the number of certifcates in the PKCS7 or RFC2630 crl set.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: should contain a gnutls_pkcs7_t
structure
indx: contains the index of the crl to extract
crl: the contents of the crl will be copied there (may be null)
crl_size: should hold the size of the crl
This function will return a crl of the PKCS7 or RFC2630 crl set.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. If the provided buffer is not long enough,
then crl_size
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
is
returned. After the last crl has been read
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
pkcs7: should contain a gnutls_pkcs7_t
structure
This function will return the number of certifcates in the PKCS7 or RFC2630 certificate set.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: should contain a gnutls_pkcs7_t structure
indx: contains the index of the certificate to extract
certificate: the contents of the certificate will be copied there (may be null)
certificate_size: should hold the size of the certificate
This function will return a certificate of the PKCS7 or RFC2630 certificate set.
After the last certificate has been read
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. If the provided buffer is not long enough,
then certificate_size
is updated and
GNUTLS_E_SHORT_MEMORY_BUFFER
is returned.
pkcs7: The structure to store the parsed PKCS7.
data: The DER or PEM encoded PKCS7.
format: One of DER or PEM
This function will convert the given DER or PEM encoded PKCS7 to
the native gnutls_pkcs7_t
format. The output will be stored in
pkcs7
.
If the PKCS7 is PEM encoded it should have a header of "PKCS7".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: The structure to be initialized
This function will initialize a PKCS7 structure. PKCS7 structures usually contain lists of X.509 Certificates and X.509 Certificate revocation lists.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: should contain a gnutls_pkcs7_t
structure
crl: the DER encoded crl to be added
This function will add a parsed CRL to the PKCS7 or RFC2630 crl set.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: should contain a gnutls_pkcs7_t
structure
crl: the DER encoded crl to be added
This function will add a crl to the PKCS7 or RFC2630 crl set.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: should contain a gnutls_pkcs7_t
structure
crt: the certificate to be copied.
This function will add a parsed certificate to the PKCS7 or
RFC2630 certificate set. This is a wrapper function over
gnutls_pkcs7_set_crt_raw()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs7: should contain a gnutls_pkcs7_t
structure
crt: the DER encoded certificate to be added
This function will add a certificate to the PKCS7 or RFC2630 certificate set.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: is the CRL to be checked
issuer: is the certificate of a possible issuer
This function will check if the given CRL was issued by the given issuer certificate. It will return true (1) if the given CRL was issued by the given issuer, and false (0) if not.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: The structure to be initialized
This function will deinitialize a CRL structure.
crl: Holds the revocation list
format: the format of output params. One of PEM or DER.
output_data: will contain a private key PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the revocation list to DER or PEM format.
If the buffer provided is not long enough to hold the output, then
GNUTLS_E_SHORT_MEMORY_BUFFER
will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN X509 CRL".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. and a negative error code on failure.
crl: should contain a gnutls_x509_crl_t
structure
seq: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)
alt: is the place where the alternative name will be copied to
alt_size: holds the size of alt.
alt_type: holds the type of the alternative name (one of gnutls_x509_subject_alt_name_t).
serial: buffer to store the serial number (may be null)
serial_size: Holds the size of the serial field (may be null)
critical: will be non (0) if the extension is marked as critical (may be null)
This function will return the X.509 authority key identifier when stored as a general name (authorityCertIssuer) and serial number.
Because more than one general names might be stored
seq
can be used as a counter to request them all until
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
Returns: Returns 0 on success, or an error code.
Since: 3.0
crl: should contain a gnutls_x509_crl_t
structure
id: The place where the identifier will be copied
id_size: Holds the size of the result field.
critical: will be non (0) if the extension is marked as critical (may be null)
This function will return the CRL authority’s key identifier. This
is obtained by the X.509 Authority Key identifier extension field
(2.5.29.35). Note that this function
only returns the keyIdentifier field of the extension and
GNUTLS_E_X509_UNSUPPORTED_EXTENSION
, if the extension contains
the name and serial number of the certificate. In that case
gnutls_x509_crl_get_authority_key_gn_serial()
may be used.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error.
Since: 2.8.0
crl: should contain a gnutls_x509_crl_t
structure
This function will return the number of revoked certificates in the given CRL.
Returns: number of certificates, a negative error code on failure.
crl: should contain a gnutls_x509_crl_t
structure
indx: the index of the certificate to extract (starting from 0)
serial: where the serial number will be copied
serial_size: initially holds the size of serial
t: if non null, will hold the time this certificate was revoked
This function will retrieve the serial number of the specified, by the index, revoked certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. and a negative error code on error.
crl: should contain a gnutls_x509_crl_t structure
indx: Specifies which DN OID to send. Use (0) to get the first one.
oid: a pointer to a structure to hold the name (may be null)
sizeof_oid: initially holds the size of ’oid’
This function will extract the requested OID of the name of the CRL issuer, specified by the given index.
If oid is null then only the size will be filled.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the sizeof_oid will be updated
with the required size. On success 0 is returned.
crl: should contain a gnutls_x509_crl_t
structure
indx: Specifies which extension OID to send. Use (0) to get the first one.
data: a pointer to a structure to hold the data (may be null)
sizeof_data: initially holds the size of oid
This function will return the requested extension data in the CRL. The extension data will be stored as a string in the provided buffer.
Use gnutls_x509_crl_get_extension_info()
to extract the OID and
critical flag. Use gnutls_x509_crl_get_extension_info()
instead,
if you want to get data indexed by the extension OID rather than
sequence.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error. If your have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Since: 2.8.0
crl: should contain a gnutls_x509_crl_t
structure
indx: Specifies which extension OID to send, use (0) to get the first one.
oid: a pointer to a structure to hold the OID
sizeof_oid: initially holds the maximum size of oid
, on return
holds actual size of oid
.
critical: output variable with critical flag, may be NULL.
This function will return the requested extension OID in the CRL,
and the critical flag for it. The extension OID will be stored as
a string in the provided buffer. Use
gnutls_x509_crl_get_extension_data()
to extract the data.
If the buffer provided is not long enough to hold the output, then
* sizeof_oid
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will be
returned.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error. If your have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Since: 2.8.0
crl: should contain a gnutls_x509_crl_t
structure
indx: Specifies which extension OID to send, use (0) to get the first one.
oid: a pointer to a structure to hold the OID (may be null)
sizeof_oid: initially holds the size of oid
This function will return the requested extension OID in the CRL. The extension OID will be stored as a string in the provided buffer.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error. If your have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Since: 2.8.0
crl: should contain a gnutls_x509_crl_t structure
buf: a pointer to a structure to hold the peer’s name (may be null)
sizeof_buf: initially holds the size of buf
This function will copy the name of the CRL issuer in the provided buffer. The name will be in the form "C=xxxx,O=yyyy,CN=zzzz" as described in RFC4514. The output string will be ASCII or UTF-8 encoded, depending on the certificate data.
If buf is NULL
then only the size will be filled.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the sizeof_buf will be updated
with the required size, and 0 on success.
crl: should contain a gnutls_x509_crl_t structure
oid: holds an Object Identified in null terminated string
indx: In case multiple same OIDs exist in the RDN, this specifies which to send. Use (0) to get the first one.
raw_flag: If non (0) returns the raw DER data of the DN part.
buf: a pointer to a structure to hold the peer’s name (may be null)
sizeof_buf: initially holds the size of buf
This function will extract the part of the name of the CRL issuer specified by the given OID. The output will be encoded as described in RFC4514. The output string will be ASCII or UTF-8 encoded, depending on the certificate data.
Some helper macros with popular OIDs can be found in gnutls/x509.h
If raw flag is (0), this function will only return known OIDs as
text. Other OIDs will be DER encoded, as described in RFC4514 – in
hex format with a ’#’ prefix. You can check about known OIDs
using gnutls_x509_dn_oid_known()
.
If buf is null then only the size will be filled.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the sizeof_buf will be updated
with the required size, and 0 on success.
crl: should contain a gnutls_x509_crl_t
structure
This function will return the time the next CRL will be issued. This field is optional in a CRL so it might be normal to get an error instead.
Returns: when the next CRL will be issued, or (time_t)-1 on error.
crl: should contain a gnutls_x509_crl_t
structure
ret: The place where the number will be copied
ret_size: Holds the size of the result field.
critical: will be non (0) if the extension is marked as critical (may be null)
This function will return the CRL number extension. This is obtained by the CRL Number extension field (2.5.29.20).
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error.
Since: 2.8.0
crl: should contain a gnutls_x509_crl_t structure
dn: will hold the starting point of the DN
This function will return a pointer to the DER encoded DN structure and the length.
Returns: a negative error code on error, and (0) on success.
Since: 2.12.0
crl: should contain a gnutls_x509_crl_t structure
sig: a pointer where the signature part will be copied (may be null).
sizeof_sig: initially holds the size of sig
This function will extract the signature field of a CRL.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. and a negative error code on error.
crl: should contain a gnutls_x509_crl_t
structure
This function will return a value of the gnutls_sign_algorithm_t
enumeration that is the signature algorithm.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: should contain a gnutls_x509_crl_t
structure
This function will return the time this CRL was issued.
Returns: when the CRL was issued, or (time_t)-1 on error.
crl: should contain a gnutls_x509_crl_t
structure
This function will return the version of the specified CRL.
Returns: The version number, or a negative error code on error.
crl: The structure to store the parsed CRL.
data: The DER or PEM encoded CRL.
format: One of DER or PEM
This function will convert the given DER or PEM encoded CRL
to the native gnutls_x509_crl_t
format. The output will be stored in ’crl’.
If the CRL is PEM encoded it should have a header of "X509 CRL".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: The structure to be initialized
This function will initialize a CRL structure. CRL stands for Certificate Revocation List. A revocation list usually contains lists of certificate serial numbers that have been revoked by an Authority. The revocation lists are always signed with the authority’s private key.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crls: The structures to store the parsed CRLs. Must not be initialized.
crl_max: Initially must hold the maximum number of crls. It will be updated with the number of crls available.
data: The PEM encoded CRLs
format: One of DER or PEM.
flags: must be (0) or an OR’d sequence of gnutls_certificate_import_flags.
This function will convert the given PEM encoded CRL list
to the native gnutls_x509_crl_t format. The output will be stored
in crls
. They will be automatically initialized.
If the Certificate is PEM encoded it should have a header of "X509 CRL".
Returns: the number of certificates read or a negative error value.
Since: 3.0
crls: The structures to store the parsed crl list. Must not be initialized.
size: It will contain the size of the list.
data: The PEM encoded CRL.
format: One of DER or PEM.
flags: must be (0) or an OR’d sequence of gnutls_certificate_import_flags.
This function will convert the given PEM encoded CRL list
to the native gnutls_x509_crl_t format. The output will be stored
in crls
. They will be automatically initialized.
If the Certificate is PEM encoded it should have a header of "X509 CRL".
Returns: the number of certificates read or a negative error value.
Since: 3.0
crl: The structure to be printed
format: Indicate the format to use
out: Newly allocated datum with (0) terminated string.
This function will pretty print a X.509 certificate revocation list, suitable for display to a human.
The output out
needs to be deallocate using gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: a CRL of type gnutls_x509_crl_t
id: The key ID
id_size: Holds the size of the serial field.
This function will set the CRL’s authority key ID extension. Only the keyIdentifier field can be set with this function. This may be used by an authority that holds multiple private keys, to distinguish the used key.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.8.0
crl: should contain a gnutls_x509_crl_t structure
crt: a certificate of type gnutls_x509_crt_t
with the revoked certificate
revocation_time: The time this certificate was revoked
This function will set a revoked certificate’s serial number to the CRL.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: should contain a gnutls_x509_crl_t structure
serial: The revoked certificate’s serial number
serial_size: Holds the size of the serial field.
revocation_time: The time this certificate was revoked
This function will set a revoked certificate’s serial number to the CRL.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: should contain a gnutls_x509_crl_t structure
exp_time: The actual time
This function will set the time this CRL will be updated.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: a CRL of type gnutls_x509_crl_t
nr: The CRL number
nr_size: Holds the size of the nr field.
This function will set the CRL’s number extension. This is to be used as a unique and monotonic number assigned to the CRL by the authority.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.8.0
crl: should contain a gnutls_x509_crl_t structure
act_time: The actual time
This function will set the time this CRL was issued.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: should contain a gnutls_x509_crl_t structure
version: holds the version number. For CRLv1 crls must be 1.
This function will set the version of the CRL. This must be one for CRL version 1, and so on. The CRLs generated by gnutls should have a version number of 2.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: should contain a gnutls_x509_crl_t structure
issuer: is the certificate of the certificate issuer
issuer_key: holds the issuer’s private key
dig: The message digest to use. GNUTLS_DIG_SHA1 is the safe choice unless you know what you’re doing.
flags: must be 0
This function will sign the CRL with the issuer’s private key, and will copy the issuer’s information into the CRL.
This must be the last step in a certificate CRL since all the previously set parameters are now signed.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crl: is the crl to be verified
CA_list: is a certificate list that is considered to be trusted one
CA_list_length: holds the number of CA certificates in CA_list
flags: Flags that may be used to change the verification algorithm. Use OR of the gnutls_certificate_verify_flags enumerations.
verify: will hold the crl verification output.
This function will try to verify the given crl and return its status.
See gnutls_x509_crt_list_verify()
for a detailed description of
return values. Note that since GnuTLS 3.1.4 this function includes
the time checks.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: The structure to be initialized
This function will deinitialize a PKCS10
certificate request
structure.
crq: should contain a gnutls_x509_crq_t
structure
format: the format of output params. One of PEM or DER.
output_data: will contain a certificate request PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the certificate request to a PEM or DER encoded PKCS10 structure.
If the buffer provided is not long enough to hold the output, then
GNUTLS_E_SHORT_MEMORY_BUFFER
will be returned and
* output_data_size
will be updated.
If the structure is PEM encoded, it will have a header of "BEGIN NEW CERTIFICATE REQUEST".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: should contain a gnutls_x509_crq_t
structure
oid: holds an Object Identified in (0)-terminated string
indx: In case multiple same OIDs exist in the attribute list, this specifies which to send, use (0) to get the first one
buf: a pointer to a structure to hold the attribute data (may be NULL
)
sizeof_buf: initially holds the size of buf
This function will return the attribute in the certificate request specified by the given Object ID. The attribute will be DER encoded.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: should contain a gnutls_x509_crq_t
structure
indx: Specifies which attribute OID to send. Use (0) to get the first one.
data: a pointer to a structure to hold the data (may be null)
sizeof_data: initially holds the size of oid
This function will return the requested attribute data in the certificate request. The attribute data will be stored as a string in the provided buffer.
Use gnutls_x509_crq_get_attribute_info()
to extract the OID.
Use gnutls_x509_crq_get_attribute_by_oid()
instead,
if you want to get data indexed by the attribute OID rather than
sequence.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error. If your have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
indx: Specifies which attribute OID to send. Use (0) to get the first one.
oid: a pointer to a structure to hold the OID
sizeof_oid: initially holds the maximum size of oid
, on return
holds actual size of oid
.
This function will return the requested attribute OID in the
certificate, and the critical flag for it. The attribute OID will
be stored as a string in the provided buffer. Use
gnutls_x509_crq_get_attribute_data()
to extract the data.
If the buffer provided is not long enough to hold the output, then
* sizeof_oid
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will be
returned.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error. If your have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
critical: will be non (0) if the extension is marked as critical
ca: pointer to output integer indicating CA status, may be NULL, value is 1 if the certificate CA flag is set, 0 otherwise.
pathlen: pointer to output integer indicating path length (may be NULL), non-negative error codes indicate a present pathLenConstraint field and the actual value, -1 indicate that the field is absent.
This function will read the certificate’s basic constraints, and return the certificates CA status. It reads the basicConstraints X.509 extension (2.5.29.19).
Returns: If the certificate is a CA a positive value will be
returned, or (0) if the certificate does not have CA flag set.
A negative error code may be returned in case of errors. If the
certificate does not contain the basicConstraints extension
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
pass: will hold a (0)-terminated password string
sizeof_pass: Initially holds the size of pass
.
This function will return the challenge password in the request. The challenge password is intended to be used for requesting a revocation of the certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: should contain a gnutls_x509_crq_t
structure
buf: a pointer to a structure to hold the name (may be NULL
)
sizeof_buf: initially holds the size of buf
This function will copy the name of the Certificate request subject
to the provided buffer. The name will be in the form
"C=xxxx,O=yyyy,CN=zzzz" as described in RFC 2253. The output string
buf
will be ASCII or UTF-8 encoded, depending on the certificate
data.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is not
long enough, and in that case the * sizeof_buf
will be updated with
the required size. On success 0 is returned.
crq: should contain a gnutls_x509_crq_t structure
oid: holds an Object Identified in null terminated string
indx: In case multiple same OIDs exist in the RDN, this specifies which to send. Use (0) to get the first one.
raw_flag: If non (0) returns the raw DER data of the DN part.
buf: a pointer to a structure to hold the name (may be NULL
)
sizeof_buf: initially holds the size of buf
This function will extract the part of the name of the Certificate request subject, specified by the given OID. The output will be encoded as described in RFC2253. The output string will be ASCII or UTF-8 encoded, depending on the certificate data.
Some helper macros with popular OIDs can be found in gnutls/x509.h
If raw flag is (0), this function will only return known OIDs as
text. Other OIDs will be DER encoded, as described in RFC2253 –
in hex format with a ’\#’ prefix. You can check about known OIDs
using gnutls_x509_dn_oid_known()
.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the * sizeof_buf
will be
updated with the required size. On success 0 is returned.
crq: should contain a gnutls_x509_crq_t structure
indx: Specifies which DN OID to send. Use (0) to get the first one.
oid: a pointer to a structure to hold the name (may be NULL
)
sizeof_oid: initially holds the size of oid
This function will extract the requested OID of the name of the certificate request subject, specified by the given index.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the * sizeof_oid
will be
updated with the required size. On success 0 is returned.
crq: should contain a gnutls_x509_crq_t
structure
oid: holds an Object Identified in null terminated string
indx: In case multiple same OIDs exist in the extensions, this specifies which to send. Use (0) to get the first one.
buf: a pointer to a structure to hold the name (may be null)
sizeof_buf: initially holds the size of buf
critical: will be non (0) if the extension is marked as critical
This function will return the extension specified by the OID in the certificate. The extensions will be returned as binary data DER encoded, in the provided buffer.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error. If the certificate does not
contain the specified extension
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
indx: Specifies which extension OID to send. Use (0) to get the first one.
data: a pointer to a structure to hold the data (may be null)
sizeof_data: initially holds the size of oid
This function will return the requested extension data in the certificate. The extension data will be stored as a string in the provided buffer.
Use gnutls_x509_crq_get_extension_info()
to extract the OID and
critical flag. Use gnutls_x509_crq_get_extension_by_oid()
instead,
if you want to get data indexed by the extension OID rather than
sequence.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error. If your have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
indx: Specifies which extension OID to send. Use (0) to get the first one.
oid: a pointer to a structure to hold the OID
sizeof_oid: initially holds the maximum size of oid
, on return
holds actual size of oid
.
critical: output variable with critical flag, may be NULL.
This function will return the requested extension OID in the
certificate, and the critical flag for it. The extension OID will
be stored as a string in the provided buffer. Use
gnutls_x509_crq_get_extension_data()
to extract the data.
If the buffer provided is not long enough to hold the output, then
* sizeof_oid
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will be
returned.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code in case of an error. If your have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Since: 2.8.0
crq: a certificate of type gnutls_x509_crq_t
flags: should be 0 for now
output_data: will contain the key ID
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will return a unique ID the depends on the public key parameters. This ID can be used in checking whether a certificate corresponds to the given private key.
If the buffer provided is not long enough to hold the output, then
* output_data_size
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER will
be returned. The output will normally be a SHA-1 hash output,
which is 20 bytes.
Returns: In case of failure a negative error code will be returned, and 0 on success.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
indx: This specifies which OID to return, use (0) to get the first one
oid: a pointer to a buffer to hold the OID (may be NULL
)
sizeof_oid: initially holds the size of oid
critical: output variable with critical flag, may be NULL
.
This function will extract the key purpose OIDs of the Certificate specified by the given index. These are stored in the Extended Key Usage extension (2.5.29.37). See the GNUTLS_KP_* definitions for human readable names.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the * sizeof_oid
will be
updated with the required size. On success 0 is returned.
Since: 2.8.0
crq: Holds the certificate
m: will hold the modulus
e: will hold the public exponent
This function will export the RSA public key’s parameters found in
the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
key_usage: where the key usage bits will be stored
critical: will be non (0) if the extension is marked as critical
This function will return certificate’s key usage, by reading the
keyUsage X.509 extension (2.5.29.15). The key usage value will
ORed values of the: GNUTLS_KEY_DIGITAL_SIGNATURE
,
GNUTLS_KEY_NON_REPUDIATION
, GNUTLS_KEY_KEY_ENCIPHERMENT
,
GNUTLS_KEY_DATA_ENCIPHERMENT
, GNUTLS_KEY_KEY_AGREEMENT
,
GNUTLS_KEY_KEY_CERT_SIGN
, GNUTLS_KEY_CRL_SIGN
,
GNUTLS_KEY_ENCIPHER_ONLY
, GNUTLS_KEY_DECIPHER_ONLY
.
Returns: the certificate key usage, or a negative error code in case of
parsing error. If the certificate does not contain the keyUsage
extension GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be
returned.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
bits: if bits is non-NULL
it will hold the size of the parameters’ in bits
This function will return the public key algorithm of a PKCS10
certificate request.
If bits is non-NULL
, it should have enough size to hold the
parameters size in bits. For RSA the bits returned is the modulus.
For DSA the bits returned are of the public exponent.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or a negative error code on error.
crq: – undescribed –
activation: The activation time
expiration: The expiration time
critical: the extension status
This function will return the expiration and activation times of the private key of the certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
if the extension is not present, otherwise a negative error value.
crq: should contain a gnutls_x509_crq_t
structure
seq: specifies the sequence number of the alt name, 0 for the first one, 1 for the second etc.
ret: is the place where the alternative name will be copied to
ret_size: holds the size of ret.
ret_type: holds the gnutls_x509_subject_alt_name_t
name type
critical: will be non (0) if the extension is marked as critical (may be null)
This function will return the alternative names, contained in the
given certificate. It is the same as
gnutls_x509_crq_get_subject_alt_name()
except for the fact that it
will return the type of the alternative name in ret_type
even if
the function fails for some reason (i.e. the buffer provided is
not enough).
Returns: the alternative subject name type on success, one of the
enumerated gnutls_x509_subject_alt_name_t
. It will return
GNUTLS_E_SHORT_MEMORY_BUFFER
if ret_size
is not large enough to
hold the value. In that case ret_size
will be updated with the
required size. If the certificate request does not have an
Alternative name with the specified sequence number then
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
seq: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)
ret: is the place where the otherName OID will be copied to
ret_size: holds the size of ret.
This function will extract the type OID of an otherName Subject Alternative Name, contained in the given certificate, and return the type as an enumerated element.
This function is only useful if
gnutls_x509_crq_get_subject_alt_name()
returned
GNUTLS_SAN_OTHERNAME
.
Returns: the alternative subject name type on success, one of the
enumerated gnutls_x509_subject_alt_name_t. For supported OIDs,
it will return one of the virtual (GNUTLS_SAN_OTHERNAME_*) types,
e.g. GNUTLS_SAN_OTHERNAME_XMPP
, and GNUTLS_SAN_OTHERNAME
for
unknown OIDs. It will return GNUTLS_E_SHORT_MEMORY_BUFFER
if
ret_size
is not large enough to hold the value. In that case
ret_size
will be updated with the required size. If the
certificate does not have an Alternative name with the specified
sequence number and with the otherName type then
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
This function will return the version of the specified Certificate request.
Returns: version of certificate request, or a negative error code on error.
crq: The structure to store the parsed certificate request.
data: The DER or PEM encoded certificate.
format: One of DER or PEM
This function will convert the given DER or PEM encoded certificate
request to a gnutls_x509_crq_t
structure. The output will be
stored in crq
.
If the Certificate is PEM encoded it should have a header of "NEW CERTIFICATE REQUEST".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: The structure to be initialized
This function will initialize a PKCS10
certificate request
structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: The structure to be printed
format: Indicate the format to use
out: Newly allocated datum with (0) terminated string.
This function will pretty print a certificate request, suitable for display to a human.
The output out
needs to be deallocate using gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
oid: holds an Object Identified in (0)-terminated string
buf: a pointer to a structure that holds the attribute data
sizeof_buf: holds the size of buf
This function will set the attribute in the certificate request specified by the given Object ID. The attribute must be be DER encoded.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: a certificate request of type gnutls_x509_crq_t
ca: true(1) or false(0) depending on the Certificate authority status.
pathLenConstraint: non-negative error codes indicate maximum length of path, and negative error codes indicate that the pathLenConstraints field should not be present.
This function will set the basicConstraints certificate extension.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
pass: holds a (0)-terminated password
This function will set a challenge password to be used when revoking the request.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: should contain a gnutls_x509_crq_t
structure
oid: holds an Object Identifier in a (0)-terminated string
raw_flag: must be 0, or 1 if the data are DER encoded
data: a pointer to the input data
sizeof_data: holds the size of data
This function will set the part of the name of the Certificate request subject, specified by the given OID. The input string should be ASCII or UTF-8 encoded.
Some helper macros with popular OIDs can be found in gnutls/x509.h
With this function you can only set the known OIDs. You can test
for known OIDs using gnutls_x509_dn_oid_known()
. For OIDs that are
not known (by gnutls) you should properly DER encode your data, and
call this function with raw_flag set.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: should contain a gnutls_x509_crq_t
structure
key: holds a private key
This function will set the public parameters from the given private key to the request.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: a certificate of type gnutls_x509_crq_t
oid: a pointer to a (0)-terminated string that holds the OID
critical: Whether this extension will be critical or not
This function will set the key purpose OIDs of the Certificate. These are stored in the Extended Key Usage extension (2.5.29.37) See the GNUTLS_KP_* definitions for human readable names.
Subsequent calls to this function will append OIDs to the OID list.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
m: holds the modulus
e: holds the public exponent
This function will set the public parameters from the given private key to the request. Only RSA keys are currently supported.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.6.0
crq: a certificate request of type gnutls_x509_crq_t
usage: an ORed sequence of the GNUTLS_KEY_* elements.
This function will set the keyUsage certificate extension.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.8.0
crq: a certificate of type gnutls_x509_crq_t
activation: The activation time
expiration: The expiration time
This function will set the private key usage period extension (2.5.29.16).
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: a certificate request of type gnutls_x509_crq_t
nt: is one of the gnutls_x509_subject_alt_name_t
enumerations
data: The data to be set
data_size: The size of data to be set
flags: GNUTLS_FSAN_SET
to clear previous data or
GNUTLS_FSAN_APPEND
to append.
This function will set the subject alternative name certificate extension. It can set the following types:
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.8.0
crq: should contain a gnutls_x509_crq_t
structure
version: holds the version number, for v1 Requests must be 1
This function will set the version of the certificate request. For version 1 requests this must be one.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crq: should contain a gnutls_x509_crq_t
structure
key: holds a private key
dig: The message digest to use, i.e., GNUTLS_DIG_SHA1
flags: must be 0
This function will sign the certificate request with a private key.
This must be the same key as the one used in
gnutls_x509_crt_set_key()
since a certificate request is self
signed.
This must be the last step in a certificate request generation since all the previously set parameters are now signed.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
GNUTLS_E_ASN1_VALUE_NOT_FOUND
is returned if you didn’t set all
information in the certificate request (e.g., the version using
gnutls_x509_crq_set_version()
).
crq: is the crq to be verified
flags: Flags that may be used to change the verification algorithm. Use OR of the gnutls_certificate_verify_flags enumerations.
This function will verify self signature in the certificate request and return its status.
Returns: In case of a verification failure GNUTLS_E_PK_SIG_VERIFY_FAILED
is returned, and zero or positive code on success.
Since 2.12.0
cert: should contain an gnutls_x509_crt_t structure
hostname: A null terminated string that contains a DNS name
This function will check if the given certificate’s subject matches the given hostname. This is a basic implementation of the matching described in RFC2818 (HTTPS), which takes into account wildcards, and the DNSName/IPAddress subject alternative name PKIX extension.
Returns: non (0) for a successful match, and (0) on failure.
cert: is the certificate to be checked
issuer: is the certificate of a possible issuer
This function will check if the given certificate was issued by the given issuer. It checks the DN fields and the authority key identifier and subject key identifier fields match.
Returns: It will return true (1) if the given certificate is issued by the given issuer, and false (0) if not. A negative error code is returned in case of an error.
cert: should contain a gnutls_x509_crt_t
structure
crl_list: should contain a list of gnutls_x509_crl_t structures
crl_list_length: the length of the crl_list
This function will return check if the given certificate is revoked. It is assumed that the CRLs have been verified before.
Returns: 0 if the certificate is NOT revoked, and 1 if it is. A negative error code is returned on error.
dst: a certificate of type gnutls_x509_crt_t
src: the certificate where the dist points will be copied from
This function will copy the CRL distribution points certificate extension, from the source to the destination certificate. This may be useful to copy from a CA certificate to issued ones.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: The structure to be deinitialized
This function will deinitialize a certificate structure.
cert: Holds the certificate
format: the format of output params. One of PEM or DER.
output_data: will contain a certificate PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the certificate to DER or PEM format.
If the buffer provided is not long enough to hold the output, then *output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN CERTIFICATE".
Returns: In case of failure a negative error code will be returned, and 0 on success.
cert: should contain a gnutls_x509_crt_t
structure
This function will return the time this Certificate was or will be activated.
Returns: activation time, or (time_t)-1 on error.
crt: Holds the certificate
seq: specifies the sequence number of the access descriptor (0 for the first one, 1 for the second etc.)
what: what data to get, a gnutls_info_access_what_t
type.
data: output data to be freed with gnutls_free()
.
critical: pointer to output integer that is set to non-0 if the extension is marked as critical (may be NULL
)
This function extracts the Authority Information Access (AIA) extension, see RFC 5280 section 4.2.2.1 for more information. The AIA extension holds a sequence of AccessDescription (AD) data:
<informalexample><programlisting> AuthorityInfoAccessSyntax ::= SEQUENCE SIZE (1..MAX) OF AccessDescription
AccessDescription ::= SEQUENCE { accessMethod OBJECT IDENTIFIER, accessLocation GeneralName } </programlisting></informalexample>
The seq
input parameter is used to indicate which member of the
sequence the caller is interested in. The first member is 0, the
second member 1 and so on. When the seq
value is out of bounds,
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
The type of data returned in data
is specified via what
which
should be gnutls_info_access_what_t
values.
If what
is GNUTLS_IA_ACCESSMETHOD_OID
then data
will hold the
accessMethod OID (e.g., "1.3.6.1.5.5.7.48.1").
If what
is GNUTLS_IA_ACCESSLOCATION_GENERALNAME_TYPE
, data
will
hold the accessLocation GeneralName type (e.g.,
"uniformResourceIdentifier").
If what
is GNUTLS_IA_URI
, data
will hold the accessLocation URI
data. Requesting this what
value leads to an error if the
accessLocation is not of the "uniformResourceIdentifier" type.
If what
is GNUTLS_IA_OCSP_URI
, data
will hold the OCSP URI.
Requesting this what
value leads to an error if the accessMethod
is not 1.3.6.1.5.5.7.48.1 aka OSCP, or if accessLocation is not of
the "uniformResourceIdentifier" type.
If what
is GNUTLS_IA_CAISSUERS_URI
, data
will hold the caIssuers
URI. Requesting this what
value leads to an error if the
accessMethod is not 1.3.6.1.5.5.7.48.2 aka caIssuers, or if
accessLocation is not of the "uniformResourceIdentifier" type.
More what
values may be allocated in the future as needed.
If data
is NULL, the function does the same without storing the
output data, that is, it will set critical
and do error checking
as usual.
The value of the critical flag is returned in * critical
. Supply a
NULL critical
if you want the function to make sure the extension
is non-critical, as required by RFC 5280.
Returns: GNUTLS_E_SUCCESS
on success, GNUTLS_E_INVALID_REQUEST
on
invalid crt
, GNUTLS_E_CONSTRAINT_ERROR
if the extension is
incorrectly marked as critical (use a non-NULL critical
to
override), GNUTLS_E_UNKNOWN_ALGORITHM
if the requested OID does
not match (e.g., when using GNUTLS_IA_OCSP_URI
), otherwise a
negative error code.
Since: 3.0
cert: should contain a gnutls_x509_crt_t
structure
seq: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)
alt: is the place where the alternative name will be copied to
alt_size: holds the size of alt.
alt_type: holds the type of the alternative name (one of gnutls_x509_subject_alt_name_t).
serial: buffer to store the serial number (may be null)
serial_size: Holds the size of the serial field (may be null)
critical: will be non (0) if the extension is marked as critical (may be null)
This function will return the X.509 authority key identifier when stored as a general name (authorityCertIssuer) and serial number.
Because more than one general names might be stored
seq
can be used as a counter to request them all until
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
if the extension is not present, otherwise a negative error value.
Since: 3.0
cert: should contain a gnutls_x509_crt_t
structure
id: The place where the identifier will be copied
id_size: Holds the size of the id field.
critical: will be non (0) if the extension is marked as critical (may be null)
This function will return the X.509v3 certificate authority’s key
identifier. This is obtained by the X.509 Authority Key
identifier extension field (2.5.29.35). Note that this function
only returns the keyIdentifier field of the extension and
GNUTLS_E_X509_UNSUPPORTED_EXTENSION
, if the extension contains
the name and serial number of the certificate. In that case
gnutls_x509_crt_get_authority_key_gn_serial()
may be used.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
if the extension is not present, otherwise a negative error value.
cert: should contain a gnutls_x509_crt_t
structure
critical: will be non (0) if the extension is marked as critical
ca: pointer to output integer indicating CA status, may be NULL, value is 1 if the certificate CA flag is set, 0 otherwise.
pathlen: pointer to output integer indicating path length (may be NULL), non-negative error codes indicate a present pathLenConstraint field and the actual value, -1 indicate that the field is absent.
This function will read the certificate’s basic constraints, and return the certificates CA status. It reads the basicConstraints X.509 extension (2.5.29.19).
Returns: If the certificate is a CA a positive value will be returned, or (0) if the certificate does not have CA flag set. A negative error code may be returned in case of errors. If the certificate does not contain the basicConstraints extension GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned.
cert: should contain a gnutls_x509_crt_t
structure
critical: will be non (0) if the extension is marked as critical
This function will return certificates CA status, by reading the basicConstraints X.509 extension (2.5.29.19). If the certificate is a CA a positive value will be returned, or (0) if the certificate does not have CA flag set.
Use gnutls_x509_crt_get_basic_constraints()
if you want to read the
pathLenConstraint field too.
Returns: A negative error code may be returned in case of parsing error.
If the certificate does not contain the basicConstraints extension
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
cert: should contain a gnutls_x509_crt_t
structure
seq: specifies the sequence number of the distribution point (0 for the first one, 1 for the second etc.)
ret: is the place where the distribution point will be copied to
ret_size: holds the size of ret.
reason_flags: Revocation reasons flags.
critical: will be non (0) if the extension is marked as critical (may be null)
This function retrieves the CRL distribution points (2.5.29.31), contained in the given certificate in the X509v3 Certificate Extensions.
reason_flags
should be an ORed sequence of
GNUTLS_CRL_REASON_UNUSED
, GNUTLS_CRL_REASON_KEY_COMPROMISE
,
GNUTLS_CRL_REASON_CA_COMPROMISE
,
GNUTLS_CRL_REASON_AFFILIATION_CHANGED
,
GNUTLS_CRL_REASON_SUPERSEEDED
,
GNUTLS_CRL_REASON_CESSATION_OF_OPERATION
,
GNUTLS_CRL_REASON_CERTIFICATE_HOLD
,
GNUTLS_CRL_REASON_PRIVILEGE_WITHDRAWN
,
GNUTLS_CRL_REASON_AA_COMPROMISE
, or (0) for all possible reasons.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
and updates ret_size
if
ret_size
is not enough to hold the distribution point, or the
type of the distribution point if everything was ok. The type is
one of the enumerated gnutls_x509_subject_alt_name_t
. If the
certificate does not have an Alternative name with the specified
sequence number then GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is
returned.
cert: should contain a gnutls_x509_crt_t
structure
buf: a pointer to a structure to hold the name (may be null)
buf_size: initially holds the size of buf
This function will copy the name of the Certificate in the provided buffer. The name will be in the form "C=xxxx,O=yyyy,CN=zzzz" as described in RFC4514. The output string will be ASCII or UTF-8 encoded, depending on the certificate data.
If buf
is null then only the size will be filled.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is not
long enough, and in that case the buf_size
will be updated
with the required size. On success 0 is returned.
cert: should contain a gnutls_x509_crt_t
structure
oid: holds an Object Identified in null terminated string
indx: In case multiple same OIDs exist in the RDN, this specifies which to send. Use (0) to get the first one.
raw_flag: If non (0) returns the raw DER data of the DN part.
buf: a pointer where the DN part will be copied (may be null).
buf_size: initially holds the size of buf
This function will extract the part of the name of the Certificate subject specified by the given OID. The output, if the raw flag is not used, will be encoded as described in RFC4514. Thus a string that is ASCII or UTF-8 encoded, depending on the certificate data.
Some helper macros with popular OIDs can be found in gnutls/x509.h
If raw flag is (0), this function will only return known OIDs as
text. Other OIDs will be DER encoded, as described in RFC4514 –
in hex format with a ’#’ prefix. You can check about known OIDs
using gnutls_x509_dn_oid_known()
.
If buf
is null then only the size will be filled. If the raw_flag
is not specified the output is always null terminated, although the
buf_size
will not include the null character.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the *buf_size will be updated
with the required size. On success 0 is returned.
cert: should contain a gnutls_x509_crt_t
structure
indx: This specifies which OID to return. Use (0) to get the first one.
oid: a pointer to a buffer to hold the OID (may be null)
oid_size: initially holds the size of oid
This function will extract the OIDs of the name of the Certificate subject specified by the given index.
If oid
is null then only the size will be filled. The oid
returned will be null terminated, although oid_size
will not
account for the trailing null.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the oid_size
will be updated
with the required size. On success 0 is returned.
cert: should contain a gnutls_x509_crt_t
structure
This function will return the time this Certificate was or will be expired.
Returns: expiration time, or (time_t)-1 on error.
cert: should contain a gnutls_x509_crt_t
structure
oid: holds an Object Identified in null terminated string
indx: In case multiple same OIDs exist in the extensions, this specifies which to send. Use (0) to get the first one.
buf: a pointer to a structure to hold the name (may be null)
buf_size: initially holds the size of buf
critical: will be non (0) if the extension is marked as critical
This function will return the extension specified by the OID in the certificate. The extensions will be returned as binary data DER encoded, in the provided buffer.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned. If the certificate does not
contain the specified extension
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned.
cert: should contain a gnutls_x509_crt_t
structure
indx: Specifies which extension OID to send. Use (0) to get the first one.
data: a pointer to a structure to hold the data (may be null)
sizeof_data: initially holds the size of oid
This function will return the requested extension data in the certificate. The extension data will be stored as a string in the provided buffer.
Use gnutls_x509_crt_get_extension_info()
to extract the OID and
critical flag. Use gnutls_x509_crt_get_extension_by_oid()
instead,
if you want to get data indexed by the extension OID rather than
sequence.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned. If you have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
cert: should contain a gnutls_x509_crt_t
structure
indx: Specifies which extension OID to send. Use (0) to get the first one.
oid: a pointer to a structure to hold the OID
oid_size: initially holds the maximum size of oid
, on return
holds actual size of oid
.
critical: output variable with critical flag, may be NULL.
This function will return the requested extension OID in the
certificate, and the critical flag for it. The extension OID will
be stored as a string in the provided buffer. Use
gnutls_x509_crt_get_extension_data()
to extract the data.
If the buffer provided is not long enough to hold the output, then
oid_size
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will be
returned. The oid
returned will be null terminated, although
oid_size
will not account for the trailing null.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned. If you have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
cert: should contain a gnutls_x509_crt_t
structure
indx: Specifies which extension OID to send. Use (0) to get the first one.
oid: a pointer to a structure to hold the OID (may be null)
oid_size: initially holds the size of oid
This function will return the requested extension OID in the certificate. The extension OID will be stored as a string in the provided buffer.
The oid
returned will be null terminated, although oid_size
will not
account for the trailing null.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned. If you have reached the
last extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
cert: should contain a gnutls_x509_crt_t
structure
algo: is a digest algorithm
buf: a pointer to a structure to hold the fingerprint (may be null)
buf_size: initially holds the size of buf
This function will calculate and copy the certificate’s fingerprint in the provided buffer.
If the buffer is null then only the size will be filled.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the *buf_size will be updated
with the required size. On success 0 is returned.
cert: should contain a gnutls_x509_crt_t
structure
dn: output variable with pointer to uint8_t DN
Return the Certificate’s Issuer DN as an uint8_t data type. You may
use gnutls_x509_dn_get_rdn_ava()
to decode the DN.
Note that dn
should be treated as constant. Because points
into the cert
object, you may not deallocate cert
and continue to access dn
.
Returns: Returns 0 on success, or an error code.
cert: should contain a gnutls_x509_crt_t
structure
seq: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)
ian: is the place where the alternative name will be copied to
ian_size: holds the size of ian.
critical: will be non (0) if the extension is marked as critical (may be null)
This function retrieves the Issuer Alternative Name (2.5.29.18), contained in the given certificate in the X509v3 Certificate Extensions.
When the SAN type is otherName, it will extract the data in the
otherName’s value field, and GNUTLS_SAN_OTHERNAME
is returned.
You may use gnutls_x509_crt_get_subject_alt_othername_oid()
to get
the corresponding OID and the "virtual" SAN types (e.g.,
GNUTLS_SAN_OTHERNAME_XMPP
).
If an otherName OID is known, the data will be decoded. Otherwise the returned data will be DER encoded, and you will have to decode it yourself. Currently, only the RFC 3920 id-on-xmppAddr Issuer AltName is recognized.
Returns: the alternative issuer name type on success, one of the
enumerated gnutls_x509_subject_alt_name_t
. It will return
GNUTLS_E_SHORT_MEMORY_BUFFER
if ian_size
is not large enough
to hold the value. In that case ian_size
will be updated with
the required size. If the certificate does not have an
Alternative name with the specified sequence number then
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
Since: 2.10.0
cert: should contain a gnutls_x509_crt_t
structure
seq: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)
ian: is the place where the alternative name will be copied to
ian_size: holds the size of ret.
ian_type: holds the type of the alternative name (one of gnutls_x509_subject_alt_name_t).
critical: will be non (0) if the extension is marked as critical (may be null)
This function will return the alternative names, contained in the
given certificate. It is the same as
gnutls_x509_crt_get_issuer_alt_name()
except for the fact that it
will return the type of the alternative name in ian_type
even if
the function fails for some reason (i.e. the buffer provided is
not enough).
Returns: the alternative issuer name type on success, one of the
enumerated gnutls_x509_subject_alt_name_t
. It will return
GNUTLS_E_SHORT_MEMORY_BUFFER
if ian_size
is not large enough
to hold the value. In that case ian_size
will be updated with
the required size. If the certificate does not have an
Alternative name with the specified sequence number then
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
Since: 2.10.0
cert: should contain a gnutls_x509_crt_t
structure
seq: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)
ret: is the place where the otherName OID will be copied to
ret_size: holds the size of ret.
This function will extract the type OID of an otherName Subject Alternative Name, contained in the given certificate, and return the type as an enumerated element.
If oid
is null then only the size will be filled. The oid
returned will be null terminated, although oid_size
will not
account for the trailing null.
This function is only useful if
gnutls_x509_crt_get_issuer_alt_name()
returned
GNUTLS_SAN_OTHERNAME
.
Returns: the alternative issuer name type on success, one of the
enumerated gnutls_x509_subject_alt_name_t. For supported OIDs, it
will return one of the virtual (GNUTLS_SAN_OTHERNAME_*) types,
e.g. GNUTLS_SAN_OTHERNAME_XMPP
, and GNUTLS_SAN_OTHERNAME
for
unknown OIDs. It will return GNUTLS_E_SHORT_MEMORY_BUFFER
if
ret_size
is not large enough to hold the value. In that case
ret_size
will be updated with the required size. If the
certificate does not have an Alternative name with the specified
sequence number and with the otherName type then
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
Since: 2.10.0
cert: should contain a gnutls_x509_crt_t
structure
buf: a pointer to a structure to hold the name (may be null)
buf_size: initially holds the size of buf
This function will copy the name of the Certificate issuer in the provided buffer. The name will be in the form "C=xxxx,O=yyyy,CN=zzzz" as described in RFC4514. The output string will be ASCII or UTF-8 encoded, depending on the certificate data.
If buf
is null then only the size will be filled.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the provided buffer is not
long enough, and in that case the buf_size
will be updated with
the required size. On success 0 is returned.
cert: should contain a gnutls_x509_crt_t
structure
oid: holds an Object Identified in null terminated string
indx: In case multiple same OIDs exist in the RDN, this specifies which to send. Use (0) to get the first one.
raw_flag: If non (0) returns the raw DER data of the DN part.
buf: a pointer to a structure to hold the name (may be null)
buf_size: initially holds the size of buf
This function will extract the part of the name of the Certificate issuer specified by the given OID. The output, if the raw flag is not used, will be encoded as described in RFC4514. Thus a string that is ASCII or UTF-8 encoded, depending on the certificate data.
Some helper macros with popular OIDs can be found in gnutls/x509.h
If raw flag is (0), this function will only return known OIDs as
text. Other OIDs will be DER encoded, as described in RFC4514 –
in hex format with a ’#’ prefix. You can check about known OIDs
using gnutls_x509_dn_oid_known()
.
If buf
is null then only the size will be filled. If the raw_flag
is not specified the output is always null terminated, although the
buf_size
will not include the null character.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the provided buffer is not
long enough, and in that case the buf_size
will be updated
with the required size. On success 0 is returned.
cert: should contain a gnutls_x509_crt_t
structure
indx: This specifies which OID to return. Use (0) to get the first one.
oid: a pointer to a buffer to hold the OID (may be null)
oid_size: initially holds the size of oid
This function will extract the OIDs of the name of the Certificate issuer specified by the given index.
If oid
is null then only the size will be filled. The oid
returned will be null terminated, although oid_size
will not
account for the trailing null.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the provided buffer is not
long enough, and in that case the oid_size
will be updated
with the required size. On success 0 is returned.
crt: Holds the certificate
buf: user allocated memory buffer, will hold the unique id
buf_size: size of user allocated memory buffer (on input), will hold actual size of the unique ID on return.
This function will extract the issuerUniqueID value (if present) for the given certificate.
If the user allocated memory buffer is not large enough to hold the full subjectUniqueID, then a GNUTLS_E_SHORT_MEMORY_BUFFER error will be returned, and buf_size will be set to the actual length.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.12.0
crt: Holds the certificate
flags: should be 0 for now
output_data: will contain the key ID
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will return a unique ID the depends on the public key parameters. This ID can be used in checking whether a certificate corresponds to the given private key.
If the buffer provided is not long enough to hold the output, then *output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER will be returned. The output will normally be a SHA-1 hash output, which is 20 bytes.
Returns: In case of failure a negative error code will be returned, and 0 on success.
cert: should contain a gnutls_x509_crt_t
structure
indx: This specifies which OID to return. Use (0) to get the first one.
oid: a pointer to a buffer to hold the OID (may be null)
oid_size: initially holds the size of oid
critical: output flag to indicate criticality of extension
This function will extract the key purpose OIDs of the Certificate specified by the given index. These are stored in the Extended Key Usage extension (2.5.29.37) See the GNUTLS_KP_* definitions for human readable names.
If oid
is null then only the size will be filled. The oid
returned will be null terminated, although oid_size
will not
account for the trailing null.
Returns: GNUTLS_E_SHORT_MEMORY_BUFFER
if the provided buffer is
not long enough, and in that case the *oid_size will be updated
with the required size. On success 0 is returned.
cert: should contain a gnutls_x509_crt_t
structure
key_usage: where the key usage bits will be stored
critical: will be non (0) if the extension is marked as critical
This function will return certificate’s key usage, by reading the
keyUsage X.509 extension (2.5.29.15). The key usage value will ORed
values of the: GNUTLS_KEY_DIGITAL_SIGNATURE
,
GNUTLS_KEY_NON_REPUDIATION
, GNUTLS_KEY_KEY_ENCIPHERMENT
,
GNUTLS_KEY_DATA_ENCIPHERMENT
, GNUTLS_KEY_KEY_AGREEMENT
,
GNUTLS_KEY_KEY_CERT_SIGN
, GNUTLS_KEY_CRL_SIGN
,
GNUTLS_KEY_ENCIPHER_ONLY
, GNUTLS_KEY_DECIPHER_ONLY
.
Returns: the certificate key usage, or a negative error code in case of
parsing error. If the certificate does not contain the keyUsage
extension GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be
returned.
cert: should contain a gnutls_x509_crt_t
structure
bits: if bits is non null it will hold the size of the parameters’ in bits
This function will return the public key algorithm of an X.509 certificate.
If bits is non null, it should have enough size to hold the parameters size in bits. For RSA the bits returned is the modulus. For DSA the bits returned are of the public exponent.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or a negative error code on error.
crt: Holds the certificate
p: will hold the p
q: will hold the q
g: will hold the g
y: will hold the y
This function will export the DSA public key’s parameters found in
the given certificate. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
crt: Holds the certificate
m: will hold the modulus
e: will hold the public exponent
This function will export the RSA public key’s parameters found in
the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
cert: should contain a gnutls_x509_crt_t
structure
activation: The activation time
expiration: The expiration time
critical: the extension status
This function will return the expiration and activation times of the private key of the certificate. It relies on the PKIX extension 2.5.29.16 being present.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
if the extension is not present, otherwise a negative error value.
cert: should contain a gnutls_x509_crt_t
structure
critical: will be non (0) if the extension is marked as critical
pathlen: pointer to output integer indicating path length (may be NULL), non-negative error codes indicate a present pCPathLenConstraint field and the actual value, -1 indicate that the field is absent.
policyLanguage: output variable with OID of policy language
policy: output variable with policy data
sizeof_policy: output variable size of policy data
This function will get information from a proxy certificate. It reads the ProxyCertInfo X.509 extension (1.3.6.1.5.5.7.1.14).
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
cert: should contain a gnutls_x509_crt_t
structure
start: will hold the starting point of the DN
This function will return a pointer to the DER encoded DN structure and
the length. This points to allocated data that must be free’d using gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. or a negative error code on error.
cert: should contain a gnutls_x509_crt_t
structure
start: will hold the starting point of the DN
This function will return a pointer to the DER encoded DN structure
and the length. This points to allocated data that must be free’d using gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.or a negative error code on error.
cert: should contain a gnutls_x509_crt_t
structure
result: The place where the serial number will be copied
result_size: Holds the size of the result field.
This function will return the X.509 certificate’s serial number. This is obtained by the X509 Certificate serialNumber field. Serial is not always a 32 or 64bit number. Some CAs use large serial numbers, thus it may be wise to handle it as something uint8_t.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: should contain a gnutls_x509_crt_t
structure
sig: a pointer where the signature part will be copied (may be null).
sizeof_sig: initially holds the size of sig
This function will extract the signature field of a certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. and a negative error code on error.
cert: should contain a gnutls_x509_crt_t
structure
This function will return a value of the gnutls_sign_algorithm_t
enumeration that is the signature algorithm that has been used to
sign this certificate.
Returns: a gnutls_sign_algorithm_t
value, or a negative error code on
error.
cert: should contain a gnutls_x509_crt_t
structure
dn: output variable with pointer to uint8_t DN.
Return the Certificate’s Subject DN as an uint8_t data type. You
may use gnutls_x509_dn_get_rdn_ava()
to decode the DN.
Note that dn
should be treated as constant. Because points
into the cert
object, you may not deallocate cert
and continue to access dn
.
Returns: Returns 0 on success, or an error code.
cert: should contain a gnutls_x509_crt_t
structure
seq: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)
san: is the place where the alternative name will be copied to
san_size: holds the size of san.
critical: will be non (0) if the extension is marked as critical (may be null)
This function retrieves the Alternative Name (2.5.29.17), contained in the given certificate in the X509v3 Certificate Extensions.
When the SAN type is otherName, it will extract the data in the
otherName’s value field, and GNUTLS_SAN_OTHERNAME
is returned.
You may use gnutls_x509_crt_get_subject_alt_othername_oid()
to get
the corresponding OID and the "virtual" SAN types (e.g.,
GNUTLS_SAN_OTHERNAME_XMPP
).
If an otherName OID is known, the data will be decoded. Otherwise the returned data will be DER encoded, and you will have to decode it yourself. Currently, only the RFC 3920 id-on-xmppAddr SAN is recognized.
Returns: the alternative subject name type on success, one of the
enumerated gnutls_x509_subject_alt_name_t
. It will return
GNUTLS_E_SHORT_MEMORY_BUFFER
if san_size
is not large enough to
hold the value. In that case san_size
will be updated with the
required size. If the certificate does not have an Alternative
name with the specified sequence number then
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
cert: should contain a gnutls_x509_crt_t
structure
seq: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)
san: is the place where the alternative name will be copied to
san_size: holds the size of ret.
san_type: holds the type of the alternative name (one of gnutls_x509_subject_alt_name_t).
critical: will be non (0) if the extension is marked as critical (may be null)
This function will return the alternative names, contained in the
given certificate. It is the same as
gnutls_x509_crt_get_subject_alt_name()
except for the fact that it
will return the type of the alternative name in san_type
even if
the function fails for some reason (i.e. the buffer provided is
not enough).
Returns: the alternative subject name type on success, one of the
enumerated gnutls_x509_subject_alt_name_t
. It will return
GNUTLS_E_SHORT_MEMORY_BUFFER
if san_size
is not large enough
to hold the value. In that case san_size
will be updated with
the required size. If the certificate does not have an
Alternative name with the specified sequence number then
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
cert: should contain a gnutls_x509_crt_t
structure
seq: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)
oid: is the place where the otherName OID will be copied to
oid_size: holds the size of ret.
This function will extract the type OID of an otherName Subject Alternative Name, contained in the given certificate, and return the type as an enumerated element.
This function is only useful if
gnutls_x509_crt_get_subject_alt_name()
returned
GNUTLS_SAN_OTHERNAME
.
If oid
is null then only the size will be filled. The oid
returned will be null terminated, although oid_size
will not
account for the trailing null.
Returns: the alternative subject name type on success, one of the
enumerated gnutls_x509_subject_alt_name_t. For supported OIDs, it
will return one of the virtual (GNUTLS_SAN_OTHERNAME_*) types,
e.g. GNUTLS_SAN_OTHERNAME_XMPP
, and GNUTLS_SAN_OTHERNAME
for
unknown OIDs. It will return GNUTLS_E_SHORT_MEMORY_BUFFER
if
ian_size
is not large enough to hold the value. In that case
ian_size
will be updated with the required size. If the
certificate does not have an Alternative name with the specified
sequence number and with the otherName type then
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
is returned.
cert: should contain a gnutls_x509_crt_t
structure
ret: The place where the identifier will be copied
ret_size: Holds the size of the result field.
critical: will be non (0) if the extension is marked as critical (may be null)
This function will return the X.509v3 certificate’s subject key identifier. This is obtained by the X.509 Subject Key identifier extension field (2.5.29.14).
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
if the extension is not present, otherwise a negative error value.
crt: Holds the certificate
buf: user allocated memory buffer, will hold the unique id
buf_size: size of user allocated memory buffer (on input), will hold actual size of the unique ID on return.
This function will extract the subjectUniqueID value (if present) for the given certificate.
If the user allocated memory buffer is not large enough to hold the full subjectUniqueID, then a GNUTLS_E_SHORT_MEMORY_BUFFER error will be returned, and buf_size will be set to the actual length.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
cert: should contain a gnutls_x509_crt_t
structure
This function will return the version of the specified Certificate.
Returns: version of certificate, or a negative error code on error.
cert: The structure to store the parsed certificate.
data: The DER or PEM encoded certificate.
format: One of DER or PEM
This function will convert the given DER or PEM encoded Certificate
to the native gnutls_x509_crt_t format. The output will be stored
in cert
.
If the Certificate is PEM encoded it should have a header of "X509 CERTIFICATE", or "CERTIFICATE".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: The structure to be initialized
This function will initialize an X.509 certificate structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
certs: The structures to store the parsed certificate. Must not be initialized.
cert_max: Initially must hold the maximum number of certs. It will be updated with the number of certs available.
data: The PEM encoded certificate.
format: One of DER or PEM.
flags: must be (0) or an OR’d sequence of gnutls_certificate_import_flags.
This function will convert the given PEM encoded certificate list
to the native gnutls_x509_crt_t format. The output will be stored
in certs
. They will be automatically initialized.
The flag GNUTLS_X509_CRT_LIST_IMPORT_FAIL_IF_EXCEED
will cause
import to fail if the certificates in the provided buffer are more
than the available structures. The GNUTLS_X509_CRT_LIST_FAIL_IF_UNSORTED
flag will cause the function to fail if the provided list is not
sorted from subject to issuer.
If the Certificate is PEM encoded it should have a header of "X509 CERTIFICATE", or "CERTIFICATE".
Returns: the number of certificates read or a negative error value.
certs: The structures to store the parsed certificate. Must not be initialized.
size: It will contain the size of the list.
data: The PEM encoded certificate.
format: One of DER or PEM.
flags: must be (0) or an OR’d sequence of gnutls_certificate_import_flags.
This function will convert the given PEM encoded certificate list
to the native gnutls_x509_crt_t format. The output will be stored
in certs
. They will be automatically initialized.
If the Certificate is PEM encoded it should have a header of "X509 CERTIFICATE", or "CERTIFICATE".
Returns: the number of certificates read or a negative error value.
Since: 3.0
cert_list: is the certificate list to be verified
cert_list_length: holds the number of certificate in cert_list
CA_list: is the CA list which will be used in verification
CA_list_length: holds the number of CA certificate in CA_list
CRL_list: holds a list of CRLs.
CRL_list_length: the length of CRL list.
flags: Flags that may be used to change the verification algorithm. Use OR of the gnutls_certificate_verify_flags enumerations.
verify: will hold the certificate verification output.
This function will try to verify the given certificate list and return its status. If no flags are specified (0), this function will use the basicConstraints (2.5.29.19) PKIX extension. This means that only a certificate authority is allowed to sign a certificate.
You must also check the peer’s name in order to check if the verified certificate belongs to the actual peer.
The certificate verification output will be put in verify
and will
be one or more of the gnutls_certificate_status_t enumerated
elements bitwise or’d. For a more detailed verification status use
gnutls_x509_crt_verify()
per list element.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: The structure to be printed
format: Indicate the format to use
out: Newly allocated datum with (0) terminated string.
This function will pretty print a X.509 certificate, suitable for display to a human.
If the format is GNUTLS_CRT_PRINT_FULL
then all fields of the
certificate will be output, on multiple lines. The
GNUTLS_CRT_PRINT_ONELINE
format will generate one line with some
selected fields, which is useful for logging purposes.
The output out
needs to be deallocate using gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: a certificate of type gnutls_x509_crt_t
act_time: The actual time
This function will set the time this Certificate was or will be activated.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: Holds the certificate
what: what data to get, a gnutls_info_access_what_t
type.
data: output data to be freed with gnutls_free()
.
This function sets the Authority Information Access (AIA) extension, see RFC 5280 section 4.2.2.1 for more information.
The type of data stored in data
is specified via what
which
should be gnutls_info_access_what_t
values.
If what
is GNUTLS_IA_OCSP_URI
, data
will hold the OCSP URI.
If what
is GNUTLS_IA_CAISSUERS_URI
, data
will hold the caIssuers
URI.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
cert: a certificate of type gnutls_x509_crt_t
id: The key ID
id_size: Holds the size of the serial field.
This function will set the X.509 certificate’s authority key ID extension. Only the keyIdentifier field can be set with this function.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
ca: true(1) or false(0). Depending on the Certificate authority status.
pathLenConstraint: non-negative error codes indicate maximum length of path, and negative error codes indicate that the pathLenConstraints field should not be present.
This function will set the basicConstraints certificate extension.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
ca: true(1) or false(0). Depending on the Certificate authority status.
This function will set the basicConstraints certificate extension.
Use gnutls_x509_crt_set_basic_constraints()
if you want to control
the pathLenConstraint field too.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
type: is one of the gnutls_x509_subject_alt_name_t enumerations
data_string: The data to be set
reason_flags: revocation reasons
This function will set the CRL distribution points certificate extension.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
type: is one of the gnutls_x509_subject_alt_name_t enumerations
data: The data to be set
data_size: The data size
reason_flags: revocation reasons
This function will set the CRL distribution points certificate extension.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.6.0
crt: a certificate of type gnutls_x509_crt_t
crq: holds a certificate request
This function will set the name and public parameters as well as the extensions from the given certificate request to the certificate. Only RSA keys are currently supported.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
crq: holds a certificate request
This function will set extensions from the given request to the certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.8.0
crt: a certificate of type gnutls_x509_crt_t
oid: holds an Object Identifier in a null terminated string
raw_flag: must be 0, or 1 if the data are DER encoded
name: a pointer to the name
sizeof_name: holds the size of name
This function will set the part of the name of the Certificate subject, specified by the given OID. The input string should be ASCII or UTF-8 encoded.
Some helper macros with popular OIDs can be found in gnutls/x509.h
With this function you can only set the known OIDs. You can test
for known OIDs using gnutls_x509_dn_oid_known()
. For OIDs that are
not known (by gnutls) you should properly DER encode your data,
and call this function with raw_flag
set.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: a certificate of type gnutls_x509_crt_t
exp_time: The actual time
This function will set the time this Certificate will expire.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
oid: holds an Object Identified in null terminated string
buf: a pointer to a DER encoded data
sizeof_buf: holds the size of buf
critical: should be non (0) if the extension is to be marked as critical
This function will set an the extension, by the specified OID, in the certificate. The extension data should be binary data DER encoded.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
oid: holds an Object Identifier in a null terminated string
raw_flag: must be 0, or 1 if the data are DER encoded
name: a pointer to the name
sizeof_name: holds the size of name
This function will set the part of the name of the Certificate issuer, specified by the given OID. The input string should be ASCII or UTF-8 encoded.
Some helper macros with popular OIDs can be found in gnutls/x509.h
With this function you can only set the known OIDs. You can test
for known OIDs using gnutls_x509_dn_oid_known()
. For OIDs that are
not known (by gnutls) you should properly DER encode your data,
and call this function with raw_flag
set.
Normally you do not need to call this function, since the signing operation will copy the signer’s name as the issuer of the certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
key: holds a private key
This function will set the public parameters from the given private key to the certificate. Only RSA keys are currently supported.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: a certificate of type gnutls_x509_crt_t
oid: a pointer to a null terminated string that holds the OID
critical: Whether this extension will be critical or not
This function will set the key purpose OIDs of the Certificate. These are stored in the Extended Key Usage extension (2.5.29.37) See the GNUTLS_KP_* definitions for human readable names.
Subsequent calls to this function will append OIDs to the OID list.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
crt: a certificate of type gnutls_x509_crt_t
usage: an ORed sequence of the GNUTLS_KEY_* elements.
This function will set the keyUsage certificate extension.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
activation: The activation time
expiration: The expiration time
This function will set the private key usage period extension (2.5.29.16).
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
pathLenConstraint: non-negative error codes indicate maximum length of path, and negative error codes indicate that the pathLenConstraints field should not be present.
policyLanguage: OID describing the language of policy
.
policy: uint8_t byte array with policy language, can be NULL
sizeof_policy: size of policy
.
This function will set the proxyCertInfo extension.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a gnutls_x509_crt_t structure with the new proxy cert
eecrt: the end entity certificate that will be issuing the proxy
raw_flag: must be 0, or 1 if the CN is DER encoded
name: a pointer to the CN name, may be NULL (but MUST then be added later)
sizeof_name: holds the size of name
This function will set the subject in crt
to the end entity’s
eecrt
subject name, and add a single Common Name component name
of size sizeof_name
. This corresponds to the required proxy
certificate naming style. Note that if name
is NULL
, you MUST
set it later by using gnutls_x509_crt_set_dn_by_oid()
or similar.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: a certificate of type gnutls_x509_crt_t
serial: The serial number
serial_size: Holds the size of the serial field.
This function will set the X.509 certificate’s serial number. Serial is not always a 32 or 64bit number. Some CAs use large serial numbers, thus it may be wise to handle it as something uint8_t.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
type: is one of the gnutls_x509_subject_alt_name_t enumerations
data: The data to be set
data_size: The size of data to be set
flags: GNUTLS_FSAN_SET to clear previous data or GNUTLS_FSAN_APPEND to append.
This function will set the subject alternative name certificate extension. It can set the following types:
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.6.0
crt: a certificate of type gnutls_x509_crt_t
type: is one of the gnutls_x509_subject_alt_name_t enumerations
data_string: The data to be set, a (0) terminated string
This function will set the subject alternative name certificate extension. This function assumes that data can be expressed as a null terminated string.
The name of the function is unfortunate since it is incosistent with
gnutls_x509_crt_get_subject_alt_name()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: a certificate of type gnutls_x509_crt_t
id: The key ID
id_size: Holds the size of the serial field.
This function will set the X.509 certificate’s subject key ID extension.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
version: holds the version number. For X.509v1 certificates must be 1.
This function will set the version of the certificate. This must be one for X.509 version 1, and so on. Plain certificates without extensions must have version set to one.
To create well-formed certificates, you must specify version 3 if
you use any certificate extensions. Extensions are created by
functions such as gnutls_x509_crt_set_subject_alt_name()
or gnutls_x509_crt_set_key_usage()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
issuer: is the certificate of the certificate issuer
issuer_key: holds the issuer’s private key
This function is the same a gnutls_x509_crt_sign2()
with no flags,
and SHA1 as the hash algorithm.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: a certificate of type gnutls_x509_crt_t
issuer: is the certificate of the certificate issuer
issuer_key: holds the issuer’s private key
dig: The message digest to use, GNUTLS_DIG_SHA1
is a safe choice
flags: must be 0
This function will sign the certificate with the issuer’s private key, and will copy the issuer’s information into the certificate.
This must be the last step in a certificate generation since all the previously set parameters are now signed.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
cert: is the certificate to be verified
CA_list: is one certificate that is considered to be trusted one
CA_list_length: holds the number of CA certificate in CA_list
flags: Flags that may be used to change the verification algorithm. Use OR of the gnutls_certificate_verify_flags enumerations.
verify: will hold the certificate verification output.
This function will try to verify the given certificate and return its status.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
dn: a DN uint8_t object pointer.
This function deallocates the DN object as returned by
gnutls_x509_dn_import()
.
Since: 2.4.0
dn: Holds the uint8_t DN object
format: the format of output params. One of PEM or DER.
output_data: will contain a DN PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the DN to DER or PEM format.
If the buffer provided is not long enough to hold the output, then
* output_data_size
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN NAME".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
dn: input variable with uint8_t DN pointer
irdn: index of RDN
iava: index of AVA.
ava: Pointer to structure which will hold output information.
Get pointers to data within the DN.
Note that ava
will contain pointers into the dn
structure, so you
should not modify any data or deallocate it. Note also that the DN
in turn points into the original certificate structure, and thus
you may not deallocate the certificate and continue to access dn
.
Returns: Returns 0 on success, or an error code.
dn: the structure that will hold the imported DN
data: should contain a DER encoded RDN sequence
This function parses an RDN sequence and stores the result to a
gnutls_x509_dn_t
structure. The structure must have been initialized
with gnutls_x509_dn_init()
. You may use gnutls_x509_dn_get_rdn_ava()
to
decode the DN.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.4.0
dn: the object to be initialized
This function initializes a gnutls_x509_dn_t
structure.
The object returned must be deallocated using
gnutls_x509_dn_deinit()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.4.0
oid: holds an Object Identifier in a null terminated string
This function will inform about known DN OIDs. This is useful since
functions like gnutls_x509_crt_set_dn_by_oid()
use the information
on known OIDs to properly encode their input. Object Identifiers
that are not known are not encoded by these functions, and their
input is stored directly into the ASN.1 structure. In that case of
unknown OIDs, you have the responsibility of DER encoding your
data.
Returns: 1 on known OIDs and 0 otherwise.
oid: holds an Object Identifier in a null terminated string
flags: 0 or GNUTLS_X509_DN_OID_
*
This function will return the name of a known DN OID. If
GNUTLS_X509_DN_OID_RETURN_OID
is specified this function
will return the given OID if no descriptive name has been
found.
Returns: A null terminated string or NULL otherwise.
Since: 3.0
dst: The destination key, which should be initialized.
src: The source key
This function will copy a private key from source to destination key. Destination has to be initialized.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: The structure to be deinitialized
This function will deinitialize a private key structure.
key: Holds the key
format: the format of output params. One of PEM or DER.
output_data: will contain a private key PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the private key to a PKCS1 structure for RSA keys, or an integer sequence for DSA keys. The DSA keys are in the same format with the parameters used by openssl.
If the buffer provided is not long enough to hold the output, then
* output_data_size
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN RSA PRIVATE KEY".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: a structure that holds the DSA parameters
p: will hold the p
q: will hold the q
g: will hold the g
y: will hold the y
x: will hold the x
This function will export the DSA private key’s parameters found
in the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: a structure that holds the rsa parameters
curve: will hold the curve
x: will hold the x coordinate
y: will hold the y coordinate
k: will hold the private key
This function will export the ECC private key’s parameters found
in the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
key: Holds the key
format: the format of output params. One of PEM or DER.
password: the password that will be used to encrypt the key.
flags: an ORed sequence of gnutls_pkcs_encrypt_flags_t
output_data: will contain a private key PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the private key to a PKCS8 structure.
Both RSA and DSA keys can be exported. For DSA keys we use
PKCS 11
definitions. If the flags do not specify the encryption
cipher, then the default 3DES (PBES2) will be used.
The password
can be either ASCII or UTF-8 in the default PBES2
encryption schemas, or ASCII for the PKCS12 schemas.
If the buffer provided is not long enough to hold the output, then *output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN ENCRYPTED PRIVATE KEY" or "BEGIN PRIVATE KEY" if encryption is not used.
Returns: In case of failure a negative error code will be returned, and 0 on success.
key: a structure that holds the rsa parameters
m: will hold the modulus
e: will hold the public exponent
d: will hold the private exponent
p: will hold the first prime (p)
q: will hold the second prime (q)
u: will hold the coefficient
This function will export the RSA private key’s parameters found
in the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: a structure that holds the rsa parameters
m: will hold the modulus
e: will hold the public exponent
d: will hold the private exponent
p: will hold the first prime (p)
q: will hold the second prime (q)
u: will hold the coefficient
e1: will hold e1 = d mod (p-1)
e2: will hold e2 = d mod (q-1)
This function will export the RSA private key’s parameters found
in the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: Holds the key
This function will recalculate the secondary parameters in a key. In RSA keys, this can be the coefficient and exponent1,2.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: should contain a gnutls_x509_privkey_t
structure
algo: is one of the algorithms in gnutls_pk_algorithm_t
.
bits: the size of the modulus
flags: unused for now. Must be 0.
This function will generate a random private key. Note that this function must be called on an empty private key.
Do not set the number of bits directly, use gnutls_sec_param_to_pk_bits()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: Holds the key
flags: should be 0 for now
output_data: will contain the key ID
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will return a unique ID the depends on the public key parameters. This ID can be used in checking whether a certificate corresponds to the given key.
If the buffer provided is not long enough to hold the output, then
* output_data_size
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will
be returned. The output will normally be a SHA-1 hash output,
which is 20 bytes.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: should contain a gnutls_x509_privkey_t
structure
This function will return the public key algorithm of a private key.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or a negative error code on error.
key: The structure to store the parsed key
data: The DER or PEM encoded certificate.
format: One of DER or PEM
This function will convert the given DER or PEM encoded key to the
native gnutls_x509_privkey_t
format. The output will be stored in
key
.
If the key is PEM encoded it should have a header that contains "PRIVATE
KEY". Note that this function falls back to PKCS 8
decoding without
password, if the default format fails to import.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: The structure to store the parsed key
p: holds the p
q: holds the q
g: holds the g
y: holds the y
x: holds the x
This function will convert the given DSA raw parameters to the
native gnutls_x509_privkey_t
format. The output will be stored
in key
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: The structure to store the parsed key
curve: holds the curve
x: holds the x
y: holds the y
k: holds the k
This function will convert the given elliptic curve parameters to the
native gnutls_x509_privkey_t
format. The output will be stored
in key
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
key: The structure to store the parsed key
data: The DER or PEM encoded key.
format: One of DER or PEM
password: the password to decrypt the key (if it is encrypted).
flags: 0 if encrypted or GNUTLS_PKCS_PLAIN if not encrypted.
This function will convert the given DER or PEM encoded PKCS8 2.0
encrypted key to the native gnutls_x509_privkey_t format. The
output will be stored in key
. Both RSA and DSA keys can be
imported, and flags can only be used to indicate an unencrypted
key.
The password
can be either ASCII or UTF-8 in the default PBES2
encryption schemas, or ASCII for the PKCS12 schemas.
If the Certificate is PEM encoded it should have a header of "ENCRYPTED PRIVATE KEY", or "PRIVATE KEY". You only need to specify the flags if the key is DER encoded, since in that case the encryption status cannot be auto-detected.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: The structure to store the parsed key
m: holds the modulus
e: holds the public exponent
d: holds the private exponent
p: holds the first prime (p)
q: holds the second prime (q)
u: holds the coefficient
This function will convert the given RSA raw parameters to the
native gnutls_x509_privkey_t
format. The output will be stored in
key
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: The structure to store the parsed key
m: holds the modulus
e: holds the public exponent
d: holds the private exponent
p: holds the first prime (p)
q: holds the second prime (q)
u: holds the coefficient
e1: holds e1 = d mod (p-1)
e2: holds e2 = d mod (q-1)
This function will convert the given RSA raw parameters to the
native gnutls_x509_privkey_t
format. The output will be stored in
key
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: The structure to be initialized
This function will initialize an private key structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: a key structure
This function will return the security parameter appropriate with this private key.
Returns: On success, a valid security parameter is returned otherwise
GNUTLS_SEC_PARAM_UNKNOWN
is returned.
Since: 2.12.0
key: should contain a gnutls_x509_privkey_t
structure
This function will verify the private key parameters.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
idn: should contain a DER encoded RDN sequence
buf: a pointer to a structure to hold the peer’s name
sizeof_buf: holds the size of buf
This function will return the name of the given RDN sequence. The name will be in the form "C=xxxx,O=yyyy,CN=zzzz" as described in RFC4514.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or
GNUTLS_E_SHORT_MEMORY_BUFFER
is returned and * sizeof_buf
is
updated if the provided buffer is not long enough, otherwise a
negative error value.
idn: should contain a DER encoded RDN sequence
oid: an Object Identifier
indx: In case multiple same OIDs exist in the RDN indicates which to send. Use 0 for the first one.
raw_flag: If non (0) then the raw DER data are returned.
buf: a pointer to a structure to hold the peer’s name
sizeof_buf: holds the size of buf
This function will return the name of the given Object identifier, of the RDN sequence. The name will be encoded using the rules from RFC4514.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or
GNUTLS_E_SHORT_MEMORY_BUFFER
is returned and * sizeof_buf
is
updated if the provided buffer is not long enough, otherwise a
negative error value.
idn: should contain a DER encoded RDN sequence
indx: Indicates which OID to return. Use 0 for the first one.
buf: a pointer to a structure to hold the peer’s name OID
sizeof_buf: holds the size of buf
This function will return the specified Object identifier, of the RDN sequence.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, or
GNUTLS_E_SHORT_MEMORY_BUFFER
is returned and * sizeof_buf
is
updated if the provided buffer is not long enough, otherwise a
negative error value.
Since: 2.4.0
list: The structure of the list
clist: A list of CAs
clist_size: The length of the CA list
flags: should be 0.
This function will add the given certificate authorities to the trusted list. The list of CAs must not be deinitialized during this structure’s lifetime.
Returns: The number of added elements is returned.
Since: 3.0
list: The structure of the list
crl_list: A list of CRLs
crl_size: The length of the CRL list
flags: if GNUTLS_TL_VERIFY_CRL is given the CRLs will be verified before being added.
verification_flags: gnutls_certificate_verify_flags if flags specifies GNUTLS_TL_VERIFY_CRL
This function will add the given certificate revocation lists to the trusted list. The list of CRLs must not be deinitialized during this structure’s lifetime.
This function must be called after gnutls_x509_trust_list_add_cas()
to allow verifying the CRLs for validity.
Returns: The number of added elements is returned.
Since: 3.0
list: The structure of the list
cert: A certificate
name: An identifier for the certificate
name_size: The size of the identifier
flags: should be 0.
This function will add the given certificate to the trusted
list and associate it with a name. The certificate will not be
be used for verification with gnutls_x509_trust_list_verify_crt()
but only with gnutls_x509_trust_list_verify_named_crt()
.
In principle this function can be used to set individual "server" certificates that are trusted by the user for that specific server but for no other purposes.
The certificate must not be deinitialized during the lifetime of the trusted list.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
list: The structure to be deinitialized
all: if non-(0) it will deinitialize all the certificates and CRLs contained in the structure.
This function will deinitialize a trust list.
Since: 3.0
list: The structure of the list
cert: is the certificate to find issuer for
issuer: Will hold the issuer if any. Should be treated as constant.
flags: Use (0).
This function will attempt to find the issuer of the given certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
list: The structure to be initialized
size: The size of the internal hash table. Use (0) for default size.
This function will initialize an X.509 trust list structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
list: The structure of the list
cert_list: is the certificate list to be verified
cert_list_size: is the certificate list size
flags: Flags that may be used to change the verification algorithm. Use OR of the gnutls_certificate_verify_flags enumerations.
verify: will hold the certificate verification output.
func: If non-null will be called on each chain element verification with the output.
This function will try to verify the given certificate and return its status.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
list: The structure of the list
cert: is the certificate to be verified
name: is the certificate’s name
name_size: is the certificate’s name size
flags: Flags that may be used to change the verification algorithm. Use OR of the gnutls_certificate_verify_flags enumerations.
verify: will hold the certificate verification output.
func: If non-null will be called on each chain element verification with the output.
This function will try to find a matching named certificate. If a match is found the certificate is considered valid. In addition to that this function will also check CRLs.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
Next: OpenPGP API, Previous: X509 certificate API, Up: API reference [Contents][Index]
The following functions are for OCSP certificate status checking. Their prototypes lie in gnutls/ocsp.h.
req: should contain a gnutls_ocsp_req_t
structure
digest: hash algorithm, a gnutls_digest_algorithm_t
value
issuer: issuer of subject
certificate
cert: certificate to request status for
This function will add another request to the OCSP request for a
particular certificate. The issuer name hash, issuer key hash, and
serial number fields is populated as follows. The issuer name and
the serial number is taken from cert
. The issuer key is taken
from issuer
. The hashed values will be hashed using the digest
algorithm, normally GNUTLS_DIG_SHA1
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned.
req: should contain a gnutls_ocsp_req_t
structure
digest: hash algorithm, a gnutls_digest_algorithm_t
value
issuer_name_hash: hash of issuer’s DN
issuer_key_hash: hash of issuer’s public key
serial_number: serial number of certificate to check
This function will add another request to the OCSP request for a
particular certificate having the issuer name hash of
issuer_name_hash
and issuer key hash of issuer_key_hash
(both
hashed using digest
) and serial number serial_number
.
The information needed corresponds to the CertID structure:
<informalexample><programlisting> CertID ::= SEQUENCE { hashAlgorithm AlgorithmIdentifier, issuerNameHash OCTET STRING, – Hash of Issuer’s DN issuerKeyHash OCTET STRING, – Hash of Issuers public key serialNumber CertificateSerialNumber } </programlisting></informalexample>
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned.
req: The structure to be deinitialized
This function will deinitialize a OCSP request structure.
req: Holds the OCSP request
data: newly allocate buffer holding DER encoded OCSP request
This function will export the OCSP request to DER format.
Returns: In case of failure a negative error code will be returned, and 0 on success.
req: should contain a gnutls_ocsp_req_t
structure
indx: Specifies which extension OID to get. Use (0) to get the first one.
digest: output variable with gnutls_digest_algorithm_t
hash algorithm
issuer_name_hash: output buffer with hash of issuer’s DN
issuer_key_hash: output buffer with hash of issuer’s public key
serial_number: output buffer with serial number of certificate to check
This function will return the certificate information of the
indx
’ed request in the OCSP request. The information returned
corresponds to the CertID structure:
<informalexample><programlisting> CertID ::= SEQUENCE { hashAlgorithm AlgorithmIdentifier, issuerNameHash OCTET STRING, – Hash of Issuer’s DN issuerKeyHash OCTET STRING, – Hash of Issuers public key serialNumber CertificateSerialNumber } </programlisting></informalexample>
Each of the pointers to output variables may be NULL to indicate that the caller is not interested in that value.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned. If you have reached the last
CertID available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be
returned.
req: should contain a gnutls_ocsp_req_t
structure
indx: Specifies which extension OID to get. Use (0) to get the first one.
oid: will hold newly allocated buffer with OID of extension, may be NULL
critical: output variable with critical flag, may be NULL.
data: will hold newly allocated buffer with extension data, may be NULL
This function will return all information about the requested
extension in the OCSP request. The information returned is the
OID, the critical flag, and the data itself. The extension OID
will be stored as a string. Any of oid
, critical
, and data
may
be NULL which means that the caller is not interested in getting
that information back.
The caller needs to deallocate memory by calling gnutls_free()
on
oid
->data and data
->data.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned. If you have reached the last
extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will
be returned.
req: should contain a gnutls_ocsp_req_t
structure
critical: whether nonce extension is marked critical, or NULL
nonce: will hold newly allocated buffer with nonce data
This function will return the OCSP request nonce extension data.
The caller needs to deallocate memory by calling gnutls_free()
on
nonce
->data.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned.
req: should contain a gnutls_ocsp_req_t
structure
This function will return the version of the OCSP request. Typically this is always 1 indicating version 1.
Returns: version of OCSP request, or a negative error code on error.
req: The structure to store the parsed request.
data: DER encoded OCSP request.
This function will convert the given DER encoded OCSP request to
the native gnutls_ocsp_req_t
format. The output will be stored in
req
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
req: The structure to be initialized
This function will initialize an OCSP request structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
req: The structure to be printed
format: Indicate the format to use
out: Newly allocated datum with (0) terminated string.
This function will pretty print a OCSP request, suitable for display to a human.
If the format is GNUTLS_PRINT_FULL
then all fields of the request
will be output, on multiple lines.
The output out
->data needs to be deallocate using gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
req: should contain a gnutls_ocsp_req_t
structure
This function will add or update an nonce extension to the OCSP request with a newly generated random value.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned.
req: should contain a gnutls_ocsp_req_t
structure
oid: buffer with OID of extension as a string.
critical: critical flag, normally false.
data: the extension data
This function will add an extension to the OCSP request. Calling this function multiple times for the same OID will overwrite values from earlier calls.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned.
req: should contain a gnutls_ocsp_req_t
structure
critical: critical flag, normally false.
nonce: the nonce data
This function will add an nonce extension to the OCSP request. Calling this function multiple times will overwrite values from earlier calls.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned.
resp: should contain a gnutls_ocsp_resp_t
structure
indx: Specifies response number to get. Use (0) to get the first one.
crt: The certificate to check
This function will check whether the OCSP response is about the provided certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned.
resp: The structure to be deinitialized
This function will deinitialize a OCSP response structure.
resp: Holds the OCSP response
data: newly allocate buffer holding DER encoded OCSP response
This function will export the OCSP response to DER format.
Returns: In case of failure a negative error code will be returned, and 0 on success.
resp: should contain a gnutls_ocsp_resp_t
structure
certs: newly allocated array with gnutls_x509_crt_t
certificates
ncerts: output variable with number of allocated certs.
This function will extract the X.509 certificates found in the
Basic OCSP Response. The certs
output variable will hold a newly
allocated zero-terminated array with X.509 certificates.
Every certificate in the array needs to be de-allocated with
gnutls_x509_crt_deinit()
and the array itself must be freed using
gnutls_free()
.
Both the certs
and ncerts
variables may be NULL. Then the
function will work as normal but will not return the NULL:d
information. This can be used to get the number of certificates
only, or to just get the certificate array without its size.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
resp: should contain a gnutls_ocsp_resp_t
structure
indx: Specifies which extension OID to get. Use (0) to get the first one.
oid: will hold newly allocated buffer with OID of extension, may be NULL
critical: output variable with critical flag, may be NULL.
data: will hold newly allocated buffer with extension data, may be NULL
This function will return all information about the requested
extension in the OCSP response. The information returned is the
OID, the critical flag, and the data itself. The extension OID
will be stored as a string. Any of oid
, critical
, and data
may
be NULL which means that the caller is not interested in getting
that information back.
The caller needs to deallocate memory by calling gnutls_free()
on
oid
->data and data
->data.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned. If you have reached the last
extension available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will
be returned.
resp: should contain a gnutls_ocsp_resp_t
structure
critical: whether nonce extension is marked critical
nonce: will hold newly allocated buffer with nonce data
This function will return the Basic OCSP Response nonce extension data.
The caller needs to deallocate memory by calling gnutls_free()
on
nonce
->data.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned.
resp: should contain a gnutls_ocsp_resp_t
structure
This function will return the time when the OCSP response was signed.
Returns: signing time, or (time_t)-1 on error.
resp: should contain a gnutls_ocsp_resp_t
structure
dn: newly allocated buffer with name
This function will extract the name of the Basic OCSP Response in the provided buffer. The name will be in the form "C=xxxx,O=yyyy,CN=zzzz" as described in RFC2253. The output string will be ASCII or UTF-8 encoded, depending on the certificate data.
The caller needs to deallocate memory by calling gnutls_free()
on
dn
->data.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned.
resp: should contain a gnutls_ocsp_resp_t
structure
response_type_oid: newly allocated output buffer with response type OID
response: newly allocated output buffer with DER encoded response
This function will extract the response type OID in and the
response data from an OCSP response. Normally the
response_type_oid
is always "1.3.6.1.5.5.7.48.1.1" which means the
response
should be decoded as a Basic OCSP Response, but
technically other response types could be used.
This function is typically only useful when you want to extract the
response type OID of an response for diagnostic purposes.
Otherwise gnutls_ocsp_resp_import()
will decode the basic OCSP
response part and the caller need not worry about that aspect.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
resp: should contain a gnutls_ocsp_resp_t
structure
sig: newly allocated output buffer with signature data
This function will extract the signature field of a OCSP response.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
resp: should contain a gnutls_ocsp_resp_t
structure
This function will return a value of the gnutls_sign_algorithm_t
enumeration that is the signature algorithm that has been used to
sign the OCSP response.
Returns: a gnutls_sign_algorithm_t
value, or a negative error code
on error.
resp: should contain a gnutls_ocsp_resp_t
structure
indx: Specifies response number to get. Use (0) to get the first one.
digest: output variable with gnutls_digest_algorithm_t
hash algorithm
issuer_name_hash: output buffer with hash of issuer’s DN
issuer_key_hash: output buffer with hash of issuer’s public key
serial_number: output buffer with serial number of certificate to check
cert_status: a certificate status, a gnutls_ocsp_cert_status_t
enum.
this_update: time at which the status is known to be correct.
next_update: when newer information will be available, or (time_t)-1 if unspecified
revocation_time: when cert_status
is GNUTLS_OCSP_CERT_REVOKED
, holds time of revocation.
revocation_reason: revocation reason, a gnutls_x509_crl_reason_t
enum.
This function will return the certificate information of the
indx
’ed response in the Basic OCSP Response resp
. The
information returned corresponds to the SingleResponse structure
except the final singleExtensions, reproduced here for illustration:
<informalexample><programlisting> SingleResponse ::= SEQUENCE { certID CertID, certStatus CertStatus, thisUpdate GeneralizedTime, nextUpdate [0] EXPLICIT GeneralizedTime OPTIONAL, singleExtensions [1] EXPLICIT Extensions OPTIONAL }
CertID ::= SEQUENCE { hashAlgorithm AlgorithmIdentifier, issuerNameHash OCTET STRING, – Hash of Issuer’s DN issuerKeyHash OCTET STRING, – Hash of Issuers public key serialNumber CertificateSerialNumber }
CertStatus ::= CHOICE { good [0] IMPLICIT NULL, revoked [1] IMPLICIT RevokedInfo, unknown [2] IMPLICIT UnknownInfo }
RevokedInfo ::= SEQUENCE { revocationTime GeneralizedTime, revocationReason [0] EXPLICIT CRLReason OPTIONAL } </programlisting></informalexample>
Each of the pointers to output variables may be NULL to indicate that the caller is not interested in that value.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error code is returned. If you have reached the last
CertID available GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be
returned.
resp: should contain a gnutls_ocsp_resp_t
structure
This function will return the status of a OCSP response, an
gnutls_ocsp_resp_status_t
enumeration.
Returns: status of OCSP request as a gnutls_ocsp_resp_status_t
, or
a negative error code on error.
resp: should contain a gnutls_ocsp_resp_t
structure
This function will return the version of the Basic OCSP Response. Typically this is always 1 indicating version 1.
Returns: version of Basic OCSP response, or a negative error code on error.
resp: The structure to store the parsed response.
data: DER encoded OCSP response.
This function will convert the given DER encoded OCSP response to
the native gnutls_ocsp_resp_t
format. It also decodes the Basic
OCSP Response part, if any. The output will be stored in resp
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
resp: The structure to be initialized
This function will initialize an OCSP response structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
resp: The structure to be printed
format: Indicate the format to use
out: Newly allocated datum with (0) terminated string.
This function will pretty print a OCSP response, suitable for display to a human.
If the format is GNUTLS_PRINT_FULL
then all fields of the response
will be output, on multiple lines.
The output out
->data needs to be deallocate using gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
resp: should contain a gnutls_ocsp_resp_t
structure
trustlist: trust anchors as a gnutls_x509_trust_list_t
structure
verify: output variable with verification status, an gnutls_ocsp_cert_status_t
flags: verification flags, 0 for now.
Verify signature of the Basic OCSP Response against the public key
in the certificate of a trusted signer. The trustlist
should be
populated with trust anchors. The function will extract the signer
certificate from the Basic OCSP Response and will verify it against
the trustlist
. A trusted signer is a certificate that is either
in trustlist
, or it is signed directly by a certificate in
trustlist
and has the id-ad-ocspSigning Extended Key Usage bit
set.
The output verify
variable will hold verification status codes
(e.g., GNUTLS_OCSP_VERIFY_SIGNER_NOT_FOUND
,
GNUTLS_OCSP_VERIFY_INSECURE_ALGORITHM
) which are only valid if the
function returned GNUTLS_E_SUCCESS
.
Note that the function returns GNUTLS_E_SUCCESS
even when
verification failed. The caller must always inspect the verify
variable to find out the verification status.
The flags
variable should be 0 for now.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
resp: should contain a gnutls_ocsp_resp_t
structure
issuer: certificate believed to have signed the response
verify: output variable with verification status, an gnutls_ocsp_cert_status_t
flags: verification flags, 0 for now.
Verify signature of the Basic OCSP Response against the public key
in the issuer
certificate.
The output verify
variable will hold verification status codes
(e.g., GNUTLS_OCSP_VERIFY_SIGNER_NOT_FOUND
,
GNUTLS_OCSP_VERIFY_INSECURE_ALGORITHM
) which are only valid if the
function returned GNUTLS_E_SUCCESS
.
Note that the function returns GNUTLS_E_SUCCESS
even when
verification failed. The caller must always inspect the verify
variable to find out the verification status.
The flags
variable should be 0 for now.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Next: PKCS 12 API, Previous: OCSP API, Up: API reference [Contents][Index]
The following functions are to be used for OpenPGP certificate handling. Their prototypes lie in gnutls/openpgp.h.
res: is a gnutls_certificate_credentials_t
structure.
crt: contains an openpgp public key
pkey: is an openpgp private key
This function sets a certificate/private key pair in the gnutls_certificate_credentials_t structure. This function may be called more than once (in case multiple keys/certificates exist for the server).
Note that this function requires that the preferred key ids have
been set and be used. See gnutls_openpgp_crt_set_preferred_key_id()
.
Otherwise the master key will be used.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
res: the destination context to save the data.
certfile: the file that contains the public key.
keyfile: the file that contains the secret key.
format: the format of the keys
This funtion is used to load OpenPGP keys into the GnuTLS credentials structure. The file should contain at least one valid non encrypted subkey.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
res: the destination context to save the data.
certfile: the file that contains the public key.
keyfile: the file that contains the secret key.
subkey_id: a hex encoded subkey id
format: the format of the keys
This funtion is used to load OpenPGP keys into the GnuTLS credential structure. The file should contain at least one valid non encrypted subkey.
The special keyword "auto" is also accepted as subkey_id
. In that
case the gnutls_openpgp_crt_get_auth_subkey()
will be used to
retrieve the subkey.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.4.0
res: the destination context to save the data.
cert: the datum that contains the public key.
key: the datum that contains the secret key.
format: the format of the keys
This funtion is used to load OpenPGP keys into the GnuTLS credential structure. The datum should contain at least one valid non encrypted subkey.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
res: the destination context to save the data.
cert: the datum that contains the public key.
key: the datum that contains the secret key.
subkey_id: a hex encoded subkey id
format: the format of the keys
This funtion is used to load OpenPGP keys into the GnuTLS credentials structure. The datum should contain at least one valid non encrypted subkey.
The special keyword "auto" is also accepted as subkey_id
. In that
case the gnutls_openpgp_crt_get_auth_subkey()
will be used to
retrieve the subkey.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.4.0
c: A certificate credentials structure
file: filename of the keyring.
format: format of keyring.
The function is used to set keyrings that will be used internally by various OpenPGP functions. For example to find a key when it is needed for an operations. The keyring will also be used at the verification functions.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
c: A certificate credentials structure
data: buffer with keyring data.
dlen: length of data buffer.
format: the format of the keyring
The function is used to set keyrings that will be used internally by various OpenPGP functions. For example to find a key when it is needed for an operations. The keyring will also be used at the verification functions.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: should contain a gnutls_openpgp_crt_t
structure
hostname: A null terminated string that contains a DNS name
This function will check if the given key’s owner matches the given hostname. This is a basic implementation of the matching described in RFC2818 (HTTPS), which takes into account wildcards.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: The structure to be initialized
This function will deinitialize a key structure.
key: Holds the key.
format: One of gnutls_openpgp_crt_fmt_t elements.
output_data: will contain the raw or base64 encoded key
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will convert the given key to RAW or Base64 format.
If the buffer provided is not long enough to hold the output, then
GNUTLS_E_SHORT_MEMORY_BUFFER
will be returned.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
crt: the structure that contains the OpenPGP public key.
keyid: the struct to save the keyid.
flag: Non-zero indicates that a valid subkey is always returned.
Returns the 64-bit keyID of the first valid OpenPGP subkey marked for authentication. If flag is non-zero and no authentication subkey exists, then a valid subkey will be returned even if it is not marked for authentication.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: the structure that contains the OpenPGP public key.
Get key creation time.
Returns: the timestamp when the OpenPGP key was created.
key: the structure that contains the OpenPGP public key.
Get key expiration time. A value of ’0’ means that the key doesn’t expire at all.
Returns: the time when the OpenPGP key expires.
key: the raw data that contains the OpenPGP public key.
fpr: the buffer to save the fingerprint, must hold at least 20 bytes.
fprlen: the integer to save the length of the fingerprint.
Get key fingerprint. Depending on the algorithm, the fingerprint can be 16 or 20 bytes.
Returns: On success, 0 is returned. Otherwise, an error code.
key: the structure that contains the OpenPGP public key.
keyid: the buffer to save the keyid.
Get key id string.
Returns: the 64-bit keyID of the OpenPGP key.
Since: 2.4.0
key: should contain a gnutls_openpgp_crt_t structure
key_usage: where the key usage bits will be stored
This function will return certificate’s key usage, by checking the
key algorithm. The key usage value will ORed values of the:
GNUTLS_KEY_DIGITAL_SIGNATURE
, GNUTLS_KEY_KEY_ENCIPHERMENT
.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: the structure that contains the OpenPGP public key.
idx: the index of the ID to extract
buf: a pointer to a structure to hold the name, may be NULL
to only get the sizeof_buf
.
sizeof_buf: holds the maximum size of buf
, on return hold the
actual/required size of buf
.
Extracts the userID from the parsed OpenPGP key.
Returns: GNUTLS_E_SUCCESS
on success, and if the index of the ID
does not exist GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
, or an
error code.
key: is an OpenPGP key
bits: if bits is non null it will hold the size of the parameters’ in bits
This function will return the public key algorithm of an OpenPGP certificate.
If bits is non null, it should have enough size to hold the parameters size in bits. For RSA the bits returned is the modulus. For DSA the bits returned are of the public exponent.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or GNUTLS_PK_UNKNOWN on error.
crt: Holds the certificate
p: will hold the p
q: will hold the q
g: will hold the g
y: will hold the y
This function will export the DSA public key’s parameters found in
the given certificate. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.4.0
crt: Holds the certificate
m: will hold the modulus
e: will hold the public exponent
This function will export the RSA public key’s parameters found in
the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.4.0
key: the structure that contains the OpenPGP public key.
keyid: the struct to save the keyid.
Get preferred key id. If it hasn’t been set it returns
GNUTLS_E_INVALID_REQUEST
.
Returns: the 64-bit preferred keyID of the OpenPGP key.
key: the structure that contains the OpenPGP public key.
Get revocation status of key.
Returns: true (1) if the key has been revoked, or false (0) if it has not.
Since: 2.4.0
key: is an OpenPGP key
This function will return the number of subkeys present in the given OpenPGP certificate.
Returns: the number of subkeys, or a negative error code on error.
Since: 2.4.0
key: the structure that contains the OpenPGP public key.
idx: the subkey index
Get subkey creation time.
Returns: the timestamp when the OpenPGP sub-key was created.
Since: 2.4.0
key: the structure that contains the OpenPGP public key.
idx: the subkey index
Get subkey expiration time. A value of ’0’ means that the key doesn’t expire at all.
Returns: the time when the OpenPGP key expires.
Since: 2.4.0
key: the raw data that contains the OpenPGP public key.
idx: the subkey index
fpr: the buffer to save the fingerprint, must hold at least 20 bytes.
fprlen: the integer to save the length of the fingerprint.
Get key fingerprint of a subkey. Depending on the algorithm, the fingerprint can be 16 or 20 bytes.
Returns: On success, 0 is returned. Otherwise, an error code.
Since: 2.4.0
key: the structure that contains the OpenPGP public key.
idx: the subkey index
keyid: the buffer to save the keyid.
Get the subkey’s key-id.
Returns: the 64-bit keyID of the OpenPGP key.
key: the structure that contains the OpenPGP public key.
keyid: the keyid.
Get subkey’s index.
Returns: the index of the subkey or a negative error value.
Since: 2.4.0
key: is an OpenPGP key
idx: is the subkey index
bits: if bits is non null it will hold the size of the parameters’ in bits
This function will return the public key algorithm of a subkey of an OpenPGP certificate.
If bits is non null, it should have enough size to hold the parameters size in bits. For RSA the bits returned is the modulus. For DSA the bits returned are of the public exponent.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or GNUTLS_PK_UNKNOWN on error.
Since: 2.4.0
crt: Holds the certificate
idx: Is the subkey index
p: will hold the p
q: will hold the q
g: will hold the g
y: will hold the y
This function will export the DSA public key’s parameters found in
the given certificate. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.4.0
crt: Holds the certificate
idx: Is the subkey index
m: will hold the modulus
e: will hold the public exponent
This function will export the RSA public key’s parameters found in
the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.4.0
key: the structure that contains the OpenPGP public key.
idx: is the subkey index
Get subkey revocation status. A negative error code indicates an error.
Returns: true (1) if the key has been revoked, or false (0) if it has not.
Since: 2.4.0
key: should contain a gnutls_openpgp_crt_t structure
idx: the subkey index
key_usage: where the key usage bits will be stored
This function will return certificate’s key usage, by checking the
key algorithm. The key usage value will ORed values of
GNUTLS_KEY_DIGITAL_SIGNATURE
or GNUTLS_KEY_KEY_ENCIPHERMENT
.
A negative error code may be returned in case of parsing error.
Returns: key usage value.
Since: 2.4.0
key: the structure that contains the OpenPGP public key.
Extract the version of the OpenPGP key.
Returns: the version number is returned, or a negative error code on errors.
key: The structure to store the parsed key.
data: The RAW or BASE64 encoded key.
format: One of gnutls_openpgp_crt_fmt_t elements.
This function will convert the given RAW or Base64 encoded key to
the native gnutls_openpgp_crt_t
format. The output will be stored
in ’key’.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: The structure to be initialized
This function will initialize an OpenPGP key structure.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
cert: The structure to be printed
format: Indicate the format to use
out: Newly allocated datum with (0) terminated string.
This function will pretty print an OpenPGP certificate, suitable for display to a human.
The format should be (0) for future compatibility.
The output out
needs to be deallocate using gnutls_free()
.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: the structure that contains the OpenPGP public key.
keyid: the selected keyid
This allows setting a preferred key id for the given certificate. This key will be used by functions that involve key handling.
If the provided keyid
is NULL
then the master key is
set as preferred.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
key: the structure that holds the key.
keyring: holds the keyring to check against
flags: unused (should be 0)
verify: will hold the certificate verification output.
Verify all signatures in the key, using the given set of keys (keyring).
The key verification output will be put in verify
and will be one
or more of the gnutls_certificate_status_t
enumerated elements
bitwise or’d.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: the structure that holds the key.
flags: unused (should be 0)
verify: will hold the key verification output.
Verifies the self signature in the key. The key verification
output will be put in verify
and will be one or more of the
gnutls_certificate_status_t enumerated elements bitwise or’d.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
ring: holds the keyring to check against
keyid: will hold the keyid to check for.
flags: unused (should be 0)
Check if a given key ID exists in the keyring.
Returns: GNUTLS_E_SUCCESS
on success (if keyid exists) and a
negative error code on failure.
keyring: The structure to be initialized
This function will deinitialize a keyring structure.
ring: Holds the keyring.
idx: the index of the certificate to export
cert: An uninitialized gnutls_openpgp_crt_t
structure
This function will extract an OpenPGP certificate from the given
keyring. If the index given is out of range
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned. The
returned structure needs to be deinited.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
ring: is an OpenPGP key ring
This function will return the number of OpenPGP certificates present in the given keyring.
Returns: the number of subkeys, or a negative error code on error.
keyring: The structure to store the parsed key.
data: The RAW or BASE64 encoded keyring.
format: One of gnutls_openpgp_keyring_fmt
elements.
This function will convert the given RAW or Base64 encoded keyring
to the native gnutls_openpgp_keyring_t
format. The output will be
stored in ’keyring’.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
keyring: The structure to be initialized
This function will initialize an keyring structure.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: The structure to be initialized
This function will deinitialize a key structure.
key: Holds the key.
format: One of gnutls_openpgp_crt_fmt_t elements.
password: the password that will be used to encrypt the key. (unused for now)
flags: (0) for future compatibility
output_data: will contain the key base64 encoded or raw
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will convert the given key to RAW or Base64 format. If the buffer provided is not long enough to hold the output, then GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
Since: 2.4.0
pkey: Holds the certificate
p: will hold the p
q: will hold the q
g: will hold the g
y: will hold the y
x: will hold the x
This function will export the DSA private key’s parameters found in
the given certificate. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.4.0
pkey: Holds the certificate
m: will hold the modulus
e: will hold the public exponent
d: will hold the private exponent
p: will hold the first prime (p)
q: will hold the second prime (q)
u: will hold the coefficient
This function will export the RSA private key’s parameters found in
the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.4.0
pkey: Holds the certificate
idx: Is the subkey index
p: will hold the p
q: will hold the q
g: will hold the g
y: will hold the y
x: will hold the x
This function will export the DSA private key’s parameters found
in the given certificate. The new parameters will be allocated
using gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.4.0
pkey: Holds the certificate
idx: Is the subkey index
m: will hold the modulus
e: will hold the public exponent
d: will hold the private exponent
p: will hold the first prime (p)
q: will hold the second prime (q)
u: will hold the coefficient
This function will export the RSA private key’s parameters found in
the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.4.0
key: the raw data that contains the OpenPGP secret key.
fpr: the buffer to save the fingerprint, must hold at least 20 bytes.
fprlen: the integer to save the length of the fingerprint.
Get the fingerprint of the OpenPGP key. Depends on the algorithm, the fingerprint can be 16 or 20 bytes.
Returns: On success, 0 is returned, or an error code.
Since: 2.4.0
key: the structure that contains the OpenPGP secret key.
keyid: the buffer to save the keyid.
Get key-id.
Returns: the 64-bit keyID of the OpenPGP key.
Since: 2.4.0
key: is an OpenPGP key
bits: if bits is non null it will hold the size of the parameters’ in bits
This function will return the public key algorithm of an OpenPGP certificate.
If bits is non null, it should have enough size to hold the parameters size in bits. For RSA the bits returned is the modulus. For DSA the bits returned are of the public exponent.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or a negative error code on error.
Since: 2.4.0
key: the structure that contains the OpenPGP public key.
keyid: the struct to save the keyid.
Get the preferred key-id for the key.
Returns: the 64-bit preferred keyID of the OpenPGP key, or if it
hasn’t been set it returns GNUTLS_E_INVALID_REQUEST
.
key: the structure that contains the OpenPGP private key.
Get revocation status of key.
Returns: true (1) if the key has been revoked, or false (0) if it has not, or a negative error code indicates an error.
Since: 2.4.0
key: is an OpenPGP key
This function will return the number of subkeys present in the given OpenPGP certificate.
Returns: the number of subkeys, or a negative error code on error.
Since: 2.4.0
key: the structure that contains the OpenPGP private key.
idx: the subkey index
Get subkey creation time.
Returns: the timestamp when the OpenPGP key was created.
Since: 2.4.0
key: the raw data that contains the OpenPGP secret key.
idx: the subkey index
fpr: the buffer to save the fingerprint, must hold at least 20 bytes.
fprlen: the integer to save the length of the fingerprint.
Get the fingerprint of an OpenPGP subkey. Depends on the algorithm, the fingerprint can be 16 or 20 bytes.
Returns: On success, 0 is returned, or an error code.
Since: 2.4.0
key: the structure that contains the OpenPGP secret key.
idx: the subkey index
keyid: the buffer to save the keyid.
Get the key-id for the subkey.
Returns: the 64-bit keyID of the OpenPGP key.
Since: 2.4.0
key: the structure that contains the OpenPGP private key.
keyid: the keyid.
Get index of subkey.
Returns: the index of the subkey or a negative error value.
Since: 2.4.0
key: is an OpenPGP key
idx: is the subkey index
bits: if bits is non null it will hold the size of the parameters’ in bits
This function will return the public key algorithm of a subkey of an OpenPGP certificate.
If bits is non null, it should have enough size to hold the parameters size in bits. For RSA the bits returned is the modulus. For DSA the bits returned are of the public exponent.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or a negative error code on error.
Since: 2.4.0
key: the structure that contains the OpenPGP private key.
idx: is the subkey index
Get revocation status of key.
Returns: true (1) if the key has been revoked, or false (0) if it has not, or a negative error code indicates an error.
Since: 2.4.0
key: The structure to store the parsed key.
data: The RAW or BASE64 encoded key.
format: One of gnutls_openpgp_crt_fmt_t
elements.
password: not used for now
flags: should be (0)
This function will convert the given RAW or Base64 encoded key to the native gnutls_openpgp_privkey_t format. The output will be stored in ’key’.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: The structure to be initialized
This function will initialize an OpenPGP key structure.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: a key structure
This function will return the security parameter appropriate with this private key.
Returns: On success, a valid security parameter is returned otherwise
GNUTLS_SEC_PARAM_UNKNOWN
is returned.
Since: 2.12.0
key: the structure that contains the OpenPGP public key.
keyid: the selected keyid
This allows setting a preferred key id for the given certificate. This key will be used by functions that involve key handling.
If the provided keyid
is NULL
then the master key is
set as preferred.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
session: a TLS session
func: the callback
This funtion will set a key retrieval function for OpenPGP keys. This callback is only useful in server side, and will be used if the peer sent a key fingerprint instead of a full key.
The retrieved key must be allocated using gnutls_malloc()
.
Next: PKCS 11 API, Previous: OpenPGP API, Up: API reference [Contents][Index]
The following functions are to be used for PKCS 12 handling. Their prototypes lie in gnutls/pkcs12.h.
bag: The bag
pass: The password used for encryption, must be ASCII.
This function will decrypt the given encrypted bag and return 0 on success.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
bag: The structure to be initialized
This function will deinitialize a PKCS12 Bag structure.
bag: The bag
pass: The password used for encryption, must be ASCII
flags: should be one of gnutls_pkcs_encrypt_flags_t
elements bitwise or’d
This function will encrypt the given bag.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
otherwise a negative error code is returned.
bag: The bag
This function will return the number of the elements withing the bag.
Returns: Number of elements in bag, or an negative error code on error.
bag: The bag
indx: The element of the bag to get the data from
data: where the bag’s data will be. Should be treated as constant.
This function will return the bag’s data. The data is a constant that is stored into the bag. Should not be accessed after the bag is deleted.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
bag: The bag
indx: The bag’s element to add the id
name: will hold a pointer to the name (to be treated as const)
This function will return the friendly name, of the specified bag element. The key ID is usually used to distinguish the local private key and the certificate pair.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. or a negative error code on error.
bag: The bag
indx: The bag’s element to add the id
id: where the ID will be copied (to be treated as const)
This function will return the key ID, of the specified bag element. The key ID is usually used to distinguish the local private key and the certificate pair.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. or a negative error code on error.
bag: The bag
indx: The element of the bag to get the type
This function will return the bag’s type.
Returns: One of the gnutls_pkcs12_bag_type_t
enumerations.
bag: The structure to be initialized
This function will initialize a PKCS12 bag structure. PKCS12 Bags usually contain private keys, lists of X.509 Certificates and X.509 Certificate revocation lists.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
bag: The bag
crl: the CRL to be copied.
This function will insert the given CRL into the
bag. This is just a wrapper over gnutls_pkcs12_bag_set_data()
.
Returns: the index of the added bag on success, or a negative error code on failure.
bag: The bag
crt: the certificate to be copied.
This function will insert the given certificate into the
bag. This is just a wrapper over gnutls_pkcs12_bag_set_data()
.
Returns: the index of the added bag on success, or a negative value on failure.
bag: The bag
type: The data’s type
data: the data to be copied.
This function will insert the given data of the given type into the bag.
Returns: the index of the added bag on success, or a negative value on error.
bag: The bag
indx: The bag’s element to add the id
name: the name
This function will add the given key friendly name, to the specified, by the index, bag element. The name will be encoded as a ’Friendly name’ bag attribute, which is usually used to set a user name to the local private key and the certificate pair.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. or a negative error code on error.
bag: The bag
indx: The bag’s element to add the id
id: the ID
This function will add the given key ID, to the specified, by the index, bag element. The key ID will be encoded as a ’Local key identifier’ bag attribute, which is usually used to distinguish the local private key and the certificate pair.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value. or a negative error code on error.
pkcs12: The structure to be initialized
This function will deinitialize a PKCS12 structure.
pkcs12: Holds the pkcs12 structure
format: the format of output params. One of PEM or DER.
output_data: will contain a structure PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the pkcs12 structure to DER or PEM format.
If the buffer provided is not long enough to hold the output, then *output_data_size will be updated and GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN PKCS12".
Returns: In case of failure a negative error code will be returned, and 0 on success.
pkcs12: should contain a gnutls_pkcs12_t structure
pass: The password for the MAC
This function will generate a MAC for the PKCS12 structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs12: should contain a gnutls_pkcs12_t structure
indx: contains the index of the bag to extract
bag: An initialized bag, where the contents of the bag will be copied
This function will return a Bag from the PKCS12 structure.
After the last Bag has been read
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs12: The structure to store the parsed PKCS12.
data: The DER or PEM encoded PKCS12.
format: One of DER or PEM
flags: an ORed sequence of gnutls_privkey_pkcs8_flags
This function will convert the given DER or PEM encoded PKCS12 to the native gnutls_pkcs12_t format. The output will be stored in ’pkcs12’.
If the PKCS12 is PEM encoded it should have a header of "PKCS12".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs12: The structure to be initialized
This function will initialize a PKCS12 structure. PKCS12 structures usually contain lists of X.509 Certificates and X.509 Certificate revocation lists.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs12: should contain a gnutls_pkcs12_t structure
bag: An initialized bag
This function will insert a Bag into the PKCS12 structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
pkcs12: should contain a gnutls_pkcs12_t structure
pass: The password for the MAC
This function will verify the MAC for the PKCS12 structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Next: Abstract key API, Previous: PKCS 12 API, Up: API reference [Contents][Index]
The following functions are to be used for PKCS 11 handling. Their prototypes lie in gnutls/pkcs11.h.
name: The filename of the module
params: should be NULL
This function will load and add a PKCS 11 module to the module list used in gnutls. After this function is called the module will be used for PKCS 11 operations.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
token_url: A PKCS 11
URL specifying a token
key: The raw key
label: A name to be used for the stored data
key_usage: One of GNUTLS_KEY_*
flags: One of GNUTLS_PKCS11_OBJ_FLAG_*
This function will copy a raw secret (symmetric) key into a PKCS 11
token specified by a URL. The key can be marked as sensitive or not.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
token_url: A PKCS 11
URL specifying a token
crt: A certificate
label: A name to be used for the stored data
flags: One of GNUTLS_PKCS11_OBJ_FLAG_*
This function will copy a certificate into a PKCS 11
token specified by
a URL. The certificate can be marked as trusted or not.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
token_url: A PKCS 11
URL specifying a token
key: A private key
label: A name to be used for the stored data
key_usage: One of GNUTLS_KEY_*
flags: One of GNUTLS_PKCS11_OBJ_* flags
This function will copy a private key into a PKCS 11
token specified by
a URL. It is highly recommended flags to contain GNUTLS_PKCS11_OBJ_FLAG_MARK_SENSITIVE
unless there is a strong reason not to.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
This function will deinitialize the PKCS 11 subsystem in gnutls.
Since: 2.12.0
object_url: The URL of the object to delete.
flags: One of GNUTLS_PKCS11_OBJ_* flags
This function will delete objects matching the given URL. Note that not all tokens support the delete operation.
Returns: On success, the number of objects deleted is returned, otherwise a negative error value.
Since: 2.12.0
flags: GNUTLS_PKCS11_FLAG_MANUAL
or GNUTLS_PKCS11_FLAG_AUTO
deprecated_config_file: either NULL or the location of a deprecated configuration file
This function will initialize the PKCS 11 subsystem in gnutls. It will
read configuration files if GNUTLS_PKCS11_FLAG_AUTO
is used or allow
you to independently load PKCS 11 modules using gnutls_pkcs11_add_provider()
if GNUTLS_PKCS11_FLAG_MANUAL
is specified.
Normally you don’t need to call this function since it is being called
by gnutls_global_init()
using the GNUTLS_PKCS11_FLAG_AUTO
. If other option
is required then it must be called before it.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
obj: The structure to be initialized
This function will deinitialize a certificate structure.
Since: 2.12.0
obj: Holds the object
output_data: will contain a certificate PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the PKCS11 object data. It is normal for
data to be inaccesible and in that case GNUTLS_E_INVALID_REQUEST
will be returned.
If the buffer provided is not long enough to hold the output, then *output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN CERTIFICATE".
Returns: In case of failure a negative error code will be
returned, and GNUTLS_E_SUCCESS
(0) on success.
Since: 2.12.0
obj: Holds the PKCS 11 certificate
detailed: non zero if a detailed URL is required
url: will contain an allocated url
This function will export a URL identifying the given certificate.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
crt: should contain a gnutls_pkcs11_obj_t
structure
itype: Denotes the type of information requested
output: where output will be stored
output_size: contains the maximum size of the output and will be overwritten with actual
This function will return information about the PKCS11 certificate
such as the label, id as well as token information where the key is
stored. When output is text it returns null terminated string
although output_size
contains the size of the actual data only.
Returns: GNUTLS_E_SUCCESS
(0) on success or a negative error code on error.
Since: 2.12.0
obj: Holds the PKCS 11 object
This function will return the type of the certificate being stored in the structure.
Returns: The type of the certificate.
Since: 2.12.0
cert: The structure to store the parsed certificate
url: a PKCS 11 url identifying the key
flags: One of GNUTLS_PKCS11_OBJ_* flags
This function will "import" a PKCS 11 URL identifying a certificate
key to the gnutls_pkcs11_obj_t
structure. This does not involve any
parsing (such as X.509 or OpenPGP) since the gnutls_pkcs11_obj_t
is
format agnostic. Only data are transferred.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
obj: The structure to be initialized
This function will initialize a pkcs11 certificate structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
p_list: An uninitialized object list (may be NULL)
n_list: initially should hold the maximum size of the list. Will contain the actual size.
url: A PKCS 11 url identifying a set of objects
attrs: Attributes of type gnutls_pkcs11_obj_attr_t
that can be used to limit output
flags: One of GNUTLS_PKCS11_OBJ_* flags
This function will initialize and set values to an object list by using all objects identified by a PKCS 11 URL.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The structure to be initialized
This function will deinitialize a private key structure.
key: Holds the PKCS 11 key
detailed: non zero if a detailed URL is required
url: will contain an allocated url
This function will export a URL identifying the given key.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
url: a token URL
pk: the public key algorithm
bits: the security bits
label: a label
flags: should be zero
This function will generate a private key in the specified
by the url
token. The pivate key will be generate within
the token and will not be exportable.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
pkey: should contain a gnutls_pkcs11_privkey_t
structure
itype: Denotes the type of information requested
output: where output will be stored
output_size: contains the maximum size of the output and will be overwritten with actual
This function will return information about the PKCS 11 private key such
as the label, id as well as token information where the key is stored. When
output is text it returns null terminated string although output_size
contains
the size of the actual data only.
Returns: GNUTLS_E_SUCCESS
(0) on success or a negative error code on error.
key: should contain a gnutls_pkcs11_privkey_t
structure
bits: if bits is non null it will hold the size of the parameters’ in bits
This function will return the public key algorithm of a private key.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or a negative error code on error.
pkey: The structure to store the parsed key
url: a PKCS 11 url identifying the key
flags: sequence of GNUTLS_PKCS_PRIVKEY_*
This function will "import" a PKCS 11 URL identifying a private
key to the gnutls_pkcs11_privkey_t
structure. In reality since
in most cases keys cannot be exported, the private key structure
is being associated with the available operations on the token.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
key: The structure to be initialized
This function will initialize an private key structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
This function will reinitialize the PKCS 11 subsystem in gnutls.
This is required by PKCS 11 when an application uses fork()
. The
reinitialization function must be called on the child.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
fn: The PIN callback, a gnutls_pkcs11_pin_callback_t()
function.
userdata: data to be supplied to callback
This function will set a callback function to be used when a PIN is
required for PKCS 11 operations. See
gnutls_pkcs11_pin_callback_t()
on how the callback should behave.
Since: 2.12.0
fn: The token callback
userdata: data to be supplied to callback
This function will set a callback function to be used when a token needs to be inserted to continue PKCS 11 operations.
Since: 2.12.0
url: should contain a PKCS 11 URL
flags: The output flags (GNUTLS_PKCS11_TOKEN_*)
This function will return information about the PKCS 11 token flags.
The flags from the gnutls_pkcs11_token_info_t
enumeration.
Returns: GNUTLS_E_SUCCESS
(0) on success or a negative error code on error.
Since: 2.12.0
url: should contain a PKCS 11 URL
ttype: Denotes the type of information requested
output: where output will be stored
output_size: contains the maximum size of the output and will be overwritten with actual
This function will return information about the PKCS 11 token such as the label, id, etc.
Returns: GNUTLS_E_SUCCESS
(0) on success or a negative error code
on error.
Since: 2.12.0
url: should contain a PKCS 11 URL
idx: The index of the mechanism
mechanism: The PKCS 11
mechanism ID
This function will return the names of the supported mechanisms by the token. It should be called with an increasing index until it return GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE.
Returns: GNUTLS_E_SUCCESS
(0) on success or a negative error code on error.
Since: 2.12.0
seq: sequence number starting from 0
detailed: non zero if a detailed URL is required
url: will contain an allocated url
This function will return the URL for each token available
in system. The url has to be released using gnutls_free()
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned,
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
if the sequence number
exceeds the available tokens, otherwise a negative error value.
Since: 2.12.0
token_url: A PKCS 11
URL specifying a token
so_pin: Security Officer’s PIN
label: A name to be used for the token
This function will initialize (format) a token. If the token is at a factory defaults state the security officer’s PIN given will be set to be the default. Otherwise it should match the officer’s PIN.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
token_url: A PKCS 11
URL specifying a token
oldpin: old user’s PIN
newpin: new user’s PIN
flags: one of gnutls_pkcs11_pin_flag_t
.
This function will modify or set a user’s PIN for the given token. If it is called to set a user pin for first time the oldpin must be NULL.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
type: Holds the PKCS 11 object type, a gnutls_pkcs11_obj_type_t
.
This function will return a human readable description of the
PKCS11 object type obj
. It will return "Unknown" for unknown
types.
Returns: human readable string labeling the PKCS11 object type
type
.
Since: 2.12.0
crt: A certificate of type gnutls_x509_crt_t
pkcs11_crt: A PKCS 11 object that contains a certificate
This function will import a PKCS 11 certificate to a gnutls_x509_crt_t
structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
crt: A certificate of type gnutls_x509_crt_t
url: A PKCS 11 url
flags: One of GNUTLS_PKCS11_OBJ_* flags
This function will import a PKCS 11 certificate directly from a token
without involving the gnutls_pkcs11_obj_t
structure. This function will
fail if the certificate stored is not of X.509 type.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
certs: A list of certificates of type gnutls_x509_crt_t
cert_max: The maximum size of the list
objs: A list of PKCS 11 objects
flags: 0 for now
This function will import a PKCS 11 certificate list to a list of
gnutls_x509_crt_t
structure. These must not be initialized.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
Next: Cryptographic API, Previous: PKCS 11 API, Up: API reference [Contents][Index]
The following functions are to be used for abstract key handling. Their prototypes lie in gnutls/abstract.h.
res: is a gnutls_certificate_credentials_t
structure.
names: is an array of DNS name of the certificate (NULL if none)
names_size: holds the size of the names list
pcert_list: contains a certificate list (path) for the specified private key
pcert_list_size: holds the size of the certificate list
key: is a gnutls_x509_privkey_t key
This function sets a certificate/private key pair in the
gnutls_certificate_credentials_t structure. This function may be
called more than once, in case multiple keys/certificates exist for
the server. For clients that wants to send more than its own end
entity certificate (e.g., also an intermediate CA cert) then put
the certificate chain in pcert_list
. The pcert_list
and key
will
become part of the credentials structure and must not
be deallocated. They will be automatically deallocated when
res
is deinitialized.
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
Since: 3.0
cred: is a gnutls_certificate_credentials_t
structure.
func: is the callback function
This function sets a callback to be called in order to retrieve the certificate to be used in the handshake.
The callback’s function prototype is: int (*callback)(gnutls_session_t, const gnutls_datum_t* req_ca_dn, int nreqs, const gnutls_pk_algorithm_t* pk_algos, int pk_algos_length, gnutls_pcert_st** pcert, unsigned int *pcert_length, gnutls_privkey_t * pkey);
req_ca_cert
is only used in X.509 certificates.
Contains a list with the CA names that the server considers trusted.
Normally we should send a certificate that is signed
by one of these CAs. These names are DER encoded. To get a more
meaningful value use the function gnutls_x509_rdn_get()
.
pk_algos
contains a list with server’s acceptable signature algorithms.
The certificate returned should support the server’s given algorithms.
pcert
should contain a single certificate and public or a list of them.
pcert_length
is the size of the previous list.
pkey
is the private key.
If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received.
In server side pk_algos and req_ca_dn are NULL.
The callback function should set the certificate list to be sent, and return 0 on success. If no certificate was selected then the number of certificates should be set to zero. The value (-1) indicates error and the handshake will be terminated.
Since: 3.0
pcert: The structure to be deinitialized
This function will deinitialize a pcert structure.
Since: 3.0
pcert: The pcert structure
crt: The raw certificate to be imported
flags: zero for now
This convenience function will import the given certificate to a
gnutls_pcert_st
structure. The structure must be deinitialized
afterwards using gnutls_pcert_deinit()
;
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
pcert: The pcert structure
cert: The raw certificate to be imported
format: The format of the certificate
keyid: The key ID to use (NULL for the master key)
flags: zero for now
This convenience function will import the given certificate to a
gnutls_pcert_st
structure. The structure must be deinitialized
afterwards using gnutls_pcert_deinit()
;
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
pcert: The pcert structure
crt: The raw certificate to be imported
flags: zero for now
This convenience function will import the given certificate to a
gnutls_pcert_st
structure. The structure must be deinitialized
afterwards using gnutls_pcert_deinit()
;
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
pcert: The pcert structure
cert: The raw certificate to be imported
format: The format of the certificate
flags: zero for now
This convenience function will import the given certificate to a
gnutls_pcert_st
structure. The structure must be deinitialized
afterwards using gnutls_pcert_deinit()
;
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
pcerts: The structures to store the parsed certificate. Must not be initialized.
pcert_max: Initially must hold the maximum number of certs. It will be updated with the number of certs available.
data: The certificates.
format: One of DER or PEM.
flags: must be (0) or an OR’d sequence of gnutls_certificate_import_flags.
This function will convert the given PEM encoded certificate list
to the native gnutls_x509_crt_t format. The output will be stored
in certs
. They will be automatically initialized.
If the Certificate is PEM encoded it should have a header of "X509 CERTIFICATE", or "CERTIFICATE".
Returns: the number of certificates read or a negative error value.
Since: 3.0
key: Holds the key
flags: zero for now
ciphertext: holds the data to be decrypted
plaintext: will contain the decrypted data, allocated with gnutls_malloc()
This function will decrypt the given data using the algorithm supported by the private key.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The structure to be deinitialized
This function will deinitialize a private key structure.
Since: 2.12.0
key: should contain a gnutls_privkey_t
structure
bits: If set will return the number of bits of the parameters (may be NULL)
This function will return the public key algorithm of a private key and if possible will return a number of bits that indicates the security parameter of the key.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or a negative error code on error.
Since: 2.12.0
key: should contain a gnutls_privkey_t
structure
This function will return the type of the private key. This is actually the type of the subsystem used to set this private key.
Returns: a member of the gnutls_privkey_type_t
enumeration on
success, or a negative error code on error.
Since: 2.12.0
pkey: The private key
pk: The public key algorithm
userdata: private data to be provided to the callbacks
sign_func: callback for signature operations
decrypt_func: callback for decryption operations
flags: Flags for the import
This function will associate the given callbacks with the
gnutls_privkey_t
structure. At least one of the two callbacks
must be non-null.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
pkey: The private key
key: The private key to be imported
flags: Flags for the import
This function will import the given private key to the abstract
gnutls_privkey_t
structure.
The gnutls_openpgp_privkey_t
object must not be deallocated
during the lifetime of this structure. The subkey set as
preferred will be used, or the master key otherwise.
flags
might be zero or one of GNUTLS_PRIVKEY_IMPORT_AUTO_RELEASE
and GNUTLS_PRIVKEY_IMPORT_COPY
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
pkey: The private key
key: The private key to be imported
flags: Flags for the import
This function will import the given private key to the abstract
gnutls_privkey_t
structure.
The gnutls_pkcs11_privkey_t
object must not be deallocated
during the lifetime of this structure.
flags
might be zero or one of GNUTLS_PRIVKEY_IMPORT_AUTO_RELEASE
and GNUTLS_PRIVKEY_IMPORT_COPY
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
pkey: The private key
key: The private key to be imported
flags: Flags for the import
This function will import the given private key to the abstract
gnutls_privkey_t
structure.
The gnutls_x509_privkey_t
object must not be deallocated
during the lifetime of this structure.
flags
might be zero or one of GNUTLS_PRIVKEY_IMPORT_AUTO_RELEASE
and GNUTLS_PRIVKEY_IMPORT_COPY
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The structure to be initialized
This function will initialize an private key structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
signer: Holds the key
hash: should be a digest algorithm
flags: should be 0 for now
data: holds the data to be signed
signature: will contain the signature allocate with gnutls_malloc()
This function will sign the given data using a signature algorithm supported by the private key. Signature algorithms are always used together with a hash functions. Different hash functions may be used for the RSA algorithm, but only the SHA family for the DSA keys.
Use gnutls_pubkey_get_preferred_hash_algorithm()
to determine
the hash algorithm.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
signer: Holds the signer’s key
hash_algo: The hash algorithm used
flags: zero for now
hash_data: holds the data to be signed
signature: will contain newly allocated signature
This function will sign the given hashed data using a signature algorithm supported by the private key. Signature algorithms are always used together with a hash functions. Different hash functions may be used for the RSA algorithm, but only SHA-XXX for the DSA keys.
Use gnutls_pubkey_get_preferred_hash_algorithm()
to determine
the hash algorithm.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The structure to be deinitialized
This function will deinitialize a public key structure.
Since: 2.12.0
key: Holds the public key
flags: should be 0 for now
plaintext: The data to be encrypted
ciphertext: contains the encrypted data
This function will encrypt the given data, using the public key.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
key: Holds the certificate
format: the format of output params. One of PEM or DER.
output_data: will contain a certificate PEM or DER encoded
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will export the public key to DER or PEM format. The contents of the exported data is the SubjectPublicKeyInfo X.509 structure.
If the buffer provided is not long enough to hold the output, then
*output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will
be returned.
If the structure is PEM encoded, it will have a header of "BEGIN CERTIFICATE".
Returns: In case of failure a negative error code will be returned, and 0 on success.
Since: 2.12.0
key: Holds the public key
flags: should be 0 for now
output_data: will contain the key ID
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
This function will return a unique ID the depends on the public key parameters. This ID can be used in checking whether a certificate corresponds to the given public key.
If the buffer provided is not long enough to hold the output, then
*output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will
be returned. The output will normally be a SHA-1 hash output,
which is 20 bytes.
Returns: In case of failure a negative error code will be returned, and 0 on success.
Since: 2.12.0
key: should contain a gnutls_pubkey_t
structure
usage: If set will return the number of bits of the parameters (may be NULL)
This function will return the key usage of the public key.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: Holds the public key
flags: should be 0 or GNUTLS_PUBKEY_GET_OPENPGP_FINGERPRINT
output_data: will contain the key ID
output_data_size: holds the size of output_data (and will be replaced by the actual size of parameters)
subkey: Will be non zero if the key ID corresponds to a subkey
This function returns the OpenPGP key ID of the corresponding key. The key is a unique ID that depends on the public key parameters.
If the flag GNUTLS_PUBKEY_GET_OPENPGP_FINGERPRINT
is specified
this function returns the fingerprint of the master key.
If the buffer provided is not long enough to hold the output, then
*output_data_size is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will
be returned. The output is GNUTLS_OPENPGP_KEYID_SIZE
bytes long.
Returns: In case of failure a negative error code will be returned, and 0 on success.
Since: 3.0
key: should contain a gnutls_pubkey_t
structure
bits: If set will return the number of bits of the parameters (may be NULL)
This function will return the public key algorithm of a public key and if possible will return a number of bits that indicates the security parameter of the key.
Returns: a member of the gnutls_pk_algorithm_t
enumeration on
success, or a negative error code on error.
Since: 2.12.0
key: Holds the public key
p: will hold the p
q: will hold the q
g: will hold the g
y: will hold the y
This function will export the DSA public key’s parameters found in
the given certificate. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.12.0
key: Holds the public key
curve: will hold the curve
x: will hold x
y: will hold y
This function will export the ECC public key’s parameters found in
the given certificate. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 3.0
key: Holds the public key
parameters: DER encoding of an ANSI X9.62 parameters
ecpoint: DER encoding of ANSI X9.62 ECPoint
This function will export the ECC public key’s parameters found in
the given certificate. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 3.0
key: Holds the certificate
m: will hold the modulus
e: will hold the public exponent
This function will export the RSA public key’s parameters found in
the given structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
Since: 2.12.0
key: Holds the certificate
hash: The result of the call with the hash algorithm used for signature
mand: If non zero it means that the algorithm MUST use this hash. May be NULL.
This function will read the certifcate and return the appropriate digest algorithm to use for signing with this certificate. Some certificates (i.e. DSA might not be able to sign without the preferred algorithm).
Returns: the 0 if the hash algorithm is found. A negative error code is returned on error.
Since: 2.12.0
key: Holds the certificate
signature: contains the signature
hash: The result of the call with the hash algorithm used for signature
This function will read the certifcate and the signed data to determine the hash algorithm used to generate the signature.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The structure to store the parsed public key.
data: The DER or PEM encoded certificate.
format: One of DER or PEM
This function will import the provided public key in
a SubjectPublicKeyInfo X.509 structure to a native
gnutls_pubkey_t
structure. The output will be stored
in key
. If the public key is PEM encoded it should have a header
of "PUBLIC KEY".
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The structure to store the parsed key
p: holds the p
q: holds the q
g: holds the g
y: holds the y
This function will convert the given DSA raw parameters to the
native gnutls_pubkey_t
format. The output will be stored
in key
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The structure to store the parsed key
curve: holds the curve
x: holds the x
y: holds the y
This function will convert the given elliptic curve parameters to a
gnutls_pubkey_t
. The output will be stored in key
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
key: The structure to store the parsed key
parameters: DER encoding of an ANSI X9.62 parameters
ecpoint: DER encoding of ANSI X9.62 ECPoint
This function will convert the given elliptic curve parameters to a
gnutls_pubkey_t
. The output will be stored in key
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 3.0
key: The public key
crt: The certificate to be imported
flags: should be zero
Imports a public key from an openpgp key. This function will import
the given public key to the abstract gnutls_pubkey_t
structure. The subkey set as preferred will be imported or the
master key otherwise.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The public key
obj: The parameters to be imported
flags: should be zero
Imports a public key from a pkcs11 key. This function will import
the given public key to the abstract gnutls_pubkey_t
structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: A key of type gnutls_pubkey_t
url: A PKCS 11 url
flags: One of GNUTLS_PKCS11_OBJ_* flags
This function will import a PKCS 11 certificate to a gnutls_pubkey_t
structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The public key
pkey: The private key
usage: GNUTLS_KEY_* key usage flags.
flags: should be zero
Imports the public key from a private. This function will import
the given public key to the abstract gnutls_pubkey_t
structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: Is a structure will hold the parameters
m: holds the modulus
e: holds the public exponent
This function will replace the parameters in the given structure. The new parameters should be stored in the appropriate gnutls_datum.
Returns: GNUTLS_E_SUCCESS
on success, or an negative error code.
Since: 2.12.0
key: The public key
crt: The certificate to be imported
flags: should be zero
This function will import the given public key to the abstract
gnutls_pubkey_t
structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: The structure to be initialized
This function will initialize an public key structure.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
key: a certificate of type gnutls_x509_crt_t
usage: an ORed sequence of the GNUTLS_KEY_* elements.
This function will set the key usage flags of the public key. This is only useful if the key is to be exported to a certificate or certificate request.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
pubkey: Holds the public key
flags: should be 0 for now
data: holds the signed data
signature: contains the signature
This function will verify the given signed data, using the parameters from the certificate.
Returns: In case of a verification failure GNUTLS_E_PK_SIG_VERIFY_FAILED
is returned, and zero or positive code on success.
Since: 2.12.0
pubkey: Holds the public key
algo: The signature algorithm used
flags: should be 0 for now
data: holds the signed data
signature: contains the signature
This function will verify the given signed data, using the parameters from the certificate.
Returns: In case of a verification failure GNUTLS_E_PK_SIG_VERIFY_FAILED
is returned, and zero or positive code on success.
Since: 3.0
key: Holds the public key
flags: should be 0 for now
hash: holds the hash digest to be verified
signature: contains the signature
This function will verify the given signed digest, using the parameters from the public key.
Deprecated. This function cannot be easily used securely.
Use gnutls_pubkey_verify_hash2()
instead.
Returns: In case of a verification failure GNUTLS_E_PK_SIG_VERIFY_FAILED
is returned, and zero or positive code on success.
Since: 2.12.0
key: Holds the public key
algo: The signature algorithm used
flags: should be 0 for now
hash: holds the hash digest to be verified
signature: contains the signature
This function will verify the given signed digest, using the parameters from the public key.
Returns: In case of a verification failure GNUTLS_E_PK_SIG_VERIFY_FAILED
is returned, and zero or positive code on success.
Since: 3.0
crl: should contain a gnutls_x509_crl_t structure
issuer: is the certificate of the certificate issuer
issuer_key: holds the issuer’s private key
dig: The message digest to use. GNUTLS_DIG_SHA1 is the safe choice unless you know what you’re doing.
flags: must be 0
This function will sign the CRL with the issuer’s private key, and will copy the issuer’s information into the CRL.
This must be the last step in a certificate CRL since all the previously set parameters are now signed.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since 2.12.0
crq: should contain a gnutls_x509_crq_t
structure
key: holds a private key
dig: The message digest to use, i.e., GNUTLS_DIG_SHA1
flags: must be 0
This function will sign the certificate request with a private key.
This must be the same key as the one used in
gnutls_x509_crt_set_key()
since a certificate request is self
signed.
This must be the last step in a certificate request generation since all the previously set parameters are now signed.
Returns: GNUTLS_E_SUCCESS
on success, otherwise a negative error code.
GNUTLS_E_ASN1_VALUE_NOT_FOUND
is returned if you didn’t set all
information in the certificate request (e.g., the version using
gnutls_x509_crq_set_version()
).
Since: 2.12.0
crq: should contain a gnutls_x509_crq_t
structure
key: holds a public key
This function will set the public parameters from the given public key to the request.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
crt: a certificate of type gnutls_x509_crt_t
issuer: is the certificate of the certificate issuer
issuer_key: holds the issuer’s private key
dig: The message digest to use, GNUTLS_DIG_SHA1
is a safe choice
flags: must be 0
This function will sign the certificate with the issuer’s private key, and will copy the issuer’s information into the certificate.
This must be the last step in a certificate generation since all the previously set parameters are now signed.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
crt: should contain a gnutls_x509_crt_t
structure
key: holds a public key
This function will set the public parameters from the given public key to the request.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Since: 2.12.0
Next: Compatibility API, Previous: Abstract key API, Up: API reference [Contents][Index]
The following functions are to be used for low-level cryptographic operations. Their prototypes lie in gnutls/crypto.h.
handle: is a gnutls_cipher_hd_t
structure.
text: the data to be authenticated
text_size: The length of the data
This function operates on authenticated encryption with associated data (AEAD) ciphers and authenticate the input data. This function can only be called once and before any encryption operations.
Returns: Zero or a negative error code on error.
Since: 3.0
handle: is a gnutls_cipher_hd_t
structure.
ciphertext: the data to encrypt
ciphertextlen: The length of data to encrypt
This function will decrypt the given data using the algorithm specified by the context.
Returns: Zero or a negative error code on error.
Since: 2.10.0
handle: is a gnutls_cipher_hd_t
structure.
ciphertext: the data to encrypt
ciphertextlen: The length of data to encrypt
text: the decrypted data
textlen: The available length for decrypted data
This function will decrypt the given data using the algorithm specified by the context.
Returns: Zero or a negative error code on error.
Since: 2.12.0
handle: is a gnutls_cipher_hd_t
structure.
This function will deinitialize all resources occupied by the given encryption context.
Since: 2.10.0
handle: is a gnutls_cipher_hd_t
structure.
text: the data to encrypt
textlen: The length of data to encrypt
This function will encrypt the given data using the algorithm specified by the context.
Returns: Zero or a negative error code on error.
Since: 2.10.0
handle: is a gnutls_cipher_hd_t
structure.
text: the data to encrypt
textlen: The length of data to encrypt
ciphertext: the encrypted data
ciphertextlen: The available length for encrypted data
This function will encrypt the given data using the algorithm specified by the context.
Returns: Zero or a negative error code on error.
Since: 2.12.0
algorithm: is an encryption algorithm
Get block size for encryption algorithm.
Returns: block size for encryption algorithm.
Since: 2.10.0
handle: is a gnutls_cipher_hd_t
structure.
cipher: the encryption algorithm to use
key: The key to be used for encryption
iv: The IV to use (if not applicable set NULL)
This function will initialize an context that can be used for encryption/decryption of data. This will effectively use the current crypto backend in use by gnutls or the cryptographic accelerator in use.
Returns: Zero or a negative error code on error.
Since: 2.10.0
handle: is a gnutls_cipher_hd_t
structure.
iv: the IV to set
ivlen: The length of the IV
This function will set the IV to be used for the next encryption block.
Since: 3.0
handle: is a gnutls_cipher_hd_t
structure.
tag: will hold the tag
tag_size: The length of the tag to return
This function operates on authenticated encryption with associated data (AEAD) ciphers and will return the output tag.
Returns: Zero or a negative error code on error.
Since: 3.0
handle: is a gnutls_cipher_hd_t
structure.
text: the data to hash
textlen: The length of data to hash
This function will hash the given data using the algorithm specified by the context.
Returns: Zero or a negative error code on error.
Since: 2.10.0
handle: is a gnutls_hash_hd_t
structure.
digest: is the output value of the hash
This function will deinitialize all resources occupied by the given hash context.
Since: 2.10.0
algorithm: the hash algorithm to use
text: the data to hash
textlen: The length of data to hash
digest: is the output value of the hash
This convenience function will hash the given data and return output on a single call.
Returns: Zero or a negative error code on error.
Since: 2.10.0
algorithm: the hash algorithm to use
This function will return the length of the output data of the given hash algorithm.
Returns: The length or zero on error.
Since: 2.10.0
dig: is a gnutls_hash_hd_t
structure.
algorithm: the hash algorithm to use
This function will initialize an context that can be used to produce a Message Digest of data. This will effectively use the current crypto backend in use by gnutls or the cryptographic accelerator in use.
Returns: Zero or a negative error code on error.
Since: 2.10.0
handle: is a gnutls_hash_hd_t
structure.
digest: is the output value of the hash
This function will output the current hash value and reset the state of the hash.
Since: 2.10.0
handle: is a gnutls_cipher_hd_t
structure.
text: the data to hash
textlen: The length of data to hash
This function will hash the given data using the algorithm specified by the context.
Returns: Zero or a negative error code on error.
Since: 2.10.0
handle: is a gnutls_hmac_hd_t
structure.
digest: is the output value of the MAC
This function will deinitialize all resources occupied by the given hmac context.
Since: 2.10.0
algorithm: the hash algorithm to use
key: the key to use
keylen: The length of the key
text: the data to hash
textlen: The length of data to hash
digest: is the output value of the hash
This convenience function will hash the given data and return output on a single call.
Returns: Zero or a negative error code on error.
Since: 2.10.0
algorithm: the hmac algorithm to use
This function will return the length of the output data of the given hmac algorithm.
Returns: The length or zero on error.
Since: 2.10.0
dig: is a gnutls_hmac_hd_t
structure.
algorithm: the HMAC algorithm to use
key: The key to be used for encryption
keylen: The length of the key
This function will initialize an context that can be used to produce a Message Authentication Code (MAC) of data. This will effectively use the current crypto backend in use by gnutls or the cryptographic accelerator in use.
Returns: Zero or a negative error code on error.
Since: 2.10.0
handle: is a gnutls_hmac_hd_t
structure.
digest: is the output value of the MAC
This function will output the current MAC value and reset the state of the MAC.
Since: 2.10.0
level: a security level
data: place to store random bytes
len: The requested size
This function will generate random data and store it to output buffer.
Returns: Zero or a negative error code on error.
Since: 2.12.0
Previous: Cryptographic API, Up: API reference [Contents][Index]
The following functions are carried over from old GnuTLS released. They might be removed at a later version. Their prototypes lie in gnutls/compat.h.
res: is a gnutls_certificate_credentials_t structure
rsa_params: is a structure that holds temporary RSA parameters.
This function will set the temporary RSA parameters for a certificate server to use. These parameters will be used in RSA-EXPORT cipher suites.
session: is a gnutls_session_t
structure.
list: is a 0 terminated list of gnutls_certificate_type_t elements.
Sets the priority on the certificate types supported by gnutls. Priority is higher for elements specified before others. After specifying the types you want, you must append a 0. Note that the certificate type priority is set on the client. The server does not use the cert type priority except for disabling types that were not specified.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
session: is a gnutls_session_t
structure.
list: is a 0 terminated list of gnutls_cipher_algorithm_t elements.
Sets the priority on the ciphers supported by gnutls. Priority is higher for elements specified before others. After specifying the ciphers you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm’s priority except for disabling algorithms that were not specified.
Returns: GNUTLS_E_SUCCESS
(0) on success, or a negative error code.
session: is a gnutls_session_t
structure.
list: is a 0 terminated list of gnutls_compression_method_t elements.
Sets the priority on the compression algorithms supported by gnutls. Priority is higher for elements specified before others. After specifying the algorithms you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm’s priority except for disabling algorithms that were not specified.
TLS 1.0 does not define any compression algorithms except NULL. Other compression algorithms are to be considered as gnutls extensions.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
session: is a gnutls_session_t
structure.
list: is a 0 terminated list of gnutls_kx_algorithm_t elements.
Sets the priority on the key exchange algorithms supported by gnutls. Priority is higher for elements specified before others. After specifying the algorithms you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm’s priority except for disabling algorithms that were not specified.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
session: is a gnutls_session_t
structure.
list: is a 0 terminated list of gnutls_mac_algorithm_t elements.
Sets the priority on the mac algorithms supported by gnutls. Priority is higher for elements specified before others. After specifying the algorithms you want, you must append a 0. Note that the priority is set on the client. The server does not use the algorithm’s priority except for disabling algorithms that were not specified.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
key: Holds the key
hash: holds the data to be signed
signature: will contain newly allocated signature
This function will sign the given hash using the private key. You
should use gnutls_openpgp_privkey_set_preferred_key_id()
before
calling this function to set the subkey to use.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Deprecated: Use gnutls_privkey_sign_hash()
instead.
session: is a gnutls_session_t
structure.
list: is a 0 terminated list of gnutls_protocol_t elements.
Sets the priority on the protocol versions supported by gnutls. This function actually enables or disables protocols. Newer protocol versions always have highest priority.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
session: is a gnutls session
Get the export RSA parameter’s modulus size.
Returns: The bits used in the last RSA-EXPORT key exchange with the peer, or a negative error code in case of error.
session: is a gnutls session
exponent: will hold the exponent.
modulus: will hold the modulus.
This function will return the peer’s public key exponent and
modulus used in the last RSA-EXPORT authentication. The output
parameters must be freed with gnutls_free()
.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise
an error code is returned.
dst: Is the destination structure, which should be initialized.
src: Is the source structure
This function will copy the RSA parameters structure from source to destination.
Returns: GNUTLS_E_SUCCESS
on success, or an negative error code.
rsa_params: Is a structure that holds the parameters
This function will deinitialize the RSA parameters structure.
params: Holds the RSA parameters
format: the format of output params. One of PEM or DER.
params_data: will contain a PKCS1 RSAPrivateKey structure PEM or DER encoded
params_data_size: holds the size of params_data (and will be replaced by the actual size of parameters)
This function will export the given RSA parameters to a PKCS1 RSAPrivateKey structure. If the buffer provided is not long enough to hold the output, then GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
If the structure is PEM encoded, it will have a header of "BEGIN RSA PRIVATE KEY".
Returns: GNUTLS_E_SUCCESS
on success, or an negative error code.
rsa: a structure that holds the rsa parameters
m: will hold the modulus
e: will hold the public exponent
d: will hold the private exponent
p: will hold the first prime (p)
q: will hold the second prime (q)
u: will hold the coefficient
bits: if non null will hold the prime’s number of bits
This function will export the RSA parameters found in the given
structure. The new parameters will be allocated using
gnutls_malloc()
and will be stored in the appropriate datum.
Returns: GNUTLS_E_SUCCESS
on success, or an negative error code.
params: The structure where the parameters will be stored
bits: is the prime’s number of bits
This function will generate new temporary RSA parameters for use in RSA-EXPORT ciphersuites. This function is normally slow.
Note that if the parameters are to be used in export cipher suites the bits value should be 512 or less. Also note that the generation of new RSA parameters is only useful to servers. Clients use the parameters sent by the server, thus it’s no use calling this in client side.
Returns: GNUTLS_E_SUCCESS
on success, or an negative error code.
params: A structure where the parameters will be copied to
pkcs1_params: should contain a PKCS1 RSAPrivateKey structure PEM or DER encoded
format: the format of params. PEM or DER.
This function will extract the RSAPrivateKey found in a PKCS1 formatted structure.
If the structure is PEM encoded, it should have a header of "BEGIN RSA PRIVATE KEY".
Returns: GNUTLS_E_SUCCESS
on success, or an negative error code.
rsa_params: Is a structure will hold the parameters
m: holds the modulus
e: holds the public exponent
d: holds the private exponent
p: holds the first prime (p)
q: holds the second prime (q)
u: holds the coefficient
This function will replace the parameters in the given structure. The new parameters should be stored in the appropriate gnutls_datum.
Returns: GNUTLS_E_SUCCESS
on success, or an negative error code.
rsa_params: Is a structure that will hold the parameters
This function will initialize the temporary RSA parameters structure.
Returns: GNUTLS_E_SUCCESS
on success, or an negative error code.
session: is a gnutls_session_t
structure.
Sets some default priority on the ciphers, key exchange methods, macs and compression methods. This function also includes weak algorithms.
This is the same as calling:
gnutls_priority_set_direct (session, "EXPORT", NULL);
This function is kept around for backwards compatibility, but
because of its wide use it is still fully supported. If you wish
to allow users to provide a string that specify which ciphers to
use (which is recommended), you should use
gnutls_priority_set_direct()
or gnutls_priority_set()
instead.
Returns: GNUTLS_E_SUCCESS
on success, or an error code.
session: is a gnutls session
userdata: if non-NULL
, will be set to abstract callback pointer.
Retrieve the callback function, and its userdata pointer.
Returns: The function pointer set by gnutls_sign_callback_set()
, or
if not set, NULL
.
Deprecated: Use the PKCS 11 interfaces instead.
session: is a gnutls session
sign_func: function pointer to application’s sign callback.
userdata: void pointer that will be passed to sign callback.
Set the callback function. The function must have this prototype:
typedef int (*gnutls_sign_func) (gnutls_session_t session, void *userdata, gnutls_certificate_type_t cert_type, const gnutls_datum_t * cert, const gnutls_datum_t * hash, gnutls_datum_t * signature);
The userdata
parameter is passed to the sign_func
verbatim, and
can be used to store application-specific data needed in the
callback function. See also gnutls_sign_callback_get()
.
Deprecated: Use the PKCS 11 or gnutls_privkey_t
interfacess like gnutls_privkey_import_ext()
instead.
crl: should contain a gnutls_x509_crl_t structure
issuer: is the certificate of the certificate issuer
issuer_key: holds the issuer’s private key
This function is the same a gnutls_x509_crl_sign2()
with no flags, and
SHA1 as the hash algorithm.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Deprecated: Use gnutls_x509_crl_privkey_sign()
.
crq: should contain a gnutls_x509_crq_t
structure
key: holds a private key
This function is the same a gnutls_x509_crq_sign2()
with no flags,
and SHA1 as the hash algorithm.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Deprecated: Use gnutls_x509_crq_privkey_sign()
instead.
crt: Holds the certificate
hash: The result of the call with the hash algorithm used for signature
mand: If non (0) it means that the algorithm MUST use this hash. May be NULL.
This function will read the certifcate and return the appropriate digest algorithm to use for signing with this certificate. Some certificates (i.e. DSA might not be able to sign without the preferred algorithm).
Deprecated: Please use gnutls_pubkey_get_preferred_hash_algorithm()
.
Returns: the 0 if the hash algorithm is found. A negative error code is returned on error.
Since: 2.12.0
crt: Holds the certificate
signature: contains the signature
hash: The result of the call with the hash algorithm used for signature
This function will read the certifcate and the signed data to determine the hash algorithm used to generate the signature.
Deprecated: Use gnutls_pubkey_get_verify_algorithm()
instead.
Returns: the 0 if the hash algorithm is found. A negative error code is returned on error.
Since: 2.8.0
crt: Holds the certificate
flags: should be 0 for now
data: holds the data to be signed
signature: contains the signature
This function will verify the given signed data, using the parameters from the certificate.
Deprecated. Please use gnutls_pubkey_verify_data()
.
Returns: In case of a verification failure GNUTLS_E_PK_SIG_VERIFY_FAILED
is returned, and zero or positive code on success.
crt: Holds the certificate
flags: should be 0 for now
hash: holds the hash digest to be verified
signature: contains the signature
This function will verify the given signed digest, using the parameters from the certificate.
Deprecated. Please use gnutls_pubkey_verify_data2()
or gnutls_pubkey_verify_hash2()
.
Returns: In case of a verification failure GNUTLS_E_PK_SIG_VERIFY_FAILED
is returned, and zero or positive code on success.
key: Holds the key
digest: should be MD5 or SHA1
flags: should be 0 for now
data: holds the data to be signed
signature: will contain the signature
signature_size: holds the size of signature (and will be replaced by the new size)
This function will sign the given data using a signature algorithm supported by the private key. Signature algorithms are always used together with a hash functions. Different hash functions may be used for the RSA algorithm, but only SHA-1 for the DSA keys.
If the buffer provided is not long enough to hold the output, then
* signature_size
is updated and GNUTLS_E_SHORT_MEMORY_BUFFER
will
be returned.
Use gnutls_x509_crt_get_preferred_hash_algorithm()
to determine
the hash algorithm.
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Deprecated: Use gnutls_privkey_sign_data()
.
key: Holds the key
hash: holds the data to be signed
signature: will contain newly allocated signature
This function will sign the given hash using the private key. Do not use this function directly unless you know what it is. Typical signing requires the data to be hashed and stored in special formats (e.g. BER Digest-Info for RSA).
Returns: On success, GNUTLS_E_SUCCESS
(0) is returned, otherwise a
negative error value.
Deprecated in: 2.12.0
Next: Bibliography, Previous: API reference, Up: Top [Contents][Index]
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Next: Function and Data Index, Previous: Copying Information, Up: Top [Contents][Index]
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Mike Ashley, "The GNU Privacy Handbook", 2002, available from http://www.gnupg.org/gph/en/manual.pdf.
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J. Schaad, "Internet X.509 Public Key Infrastructure Certificate Request Message Format (CRMF)", September 2005, Available from http://www.ietf.org/rfc/rfc4211.txt.
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Tom Wu, "The SRP Authentication and Key Exchange System", September 2000, Available from http://www.ietf.org/rfc/rfc2945.txt.
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Scott Hollenbeck, "Transport Layer Security Protocol Compression Methods", May 2004, available from http://www.ietf.org/rfc/rfc3749.txt.
Steven Tuecke, Von Welch, Doug Engert, Laura Pearlman, and Mary Thompson, "Internet X.509 Public Key Infrastructure (PKI) Proxy Certificate Profile", June 2004, available from http://www.ietf.org/rfc/rfc3820.
E. Rescorla, M. Ray, S. Dispensa, and N. Oskov, "Transport Layer Security (TLS) Renegotiation Indication Extension", February 2010, available from http://www.ietf.org/rfc/rfc5746.
Joseph Salowey, Hao Zhou, Pasi Eronen, Hannes Tschofenig, "Transport Layer Security (TLS) Session Resumption without Server-Side State", January 2008, available from http://www.ietf.org/rfc/rfc5077.
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http://www.gnu.org/software/libtasn1/
http://www.lysator.liu.se/~nisse/nettle/
IETF, or Internet Engineering Task Force, is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is open to any interested individual.
If this is not possible then please consult Interoperability.
MAC stands for Message Authentication Code. It can be described as a keyed hash algorithm. See RFC2104.
See also the Server Name Indication extension on serverind.
See LDAP, IMAP etc.
http://www.gnupg.org/related_software/gpgme/
http://trousers.sourceforge.net/
http://p11-glue.freedesktop.org/
The first message in a TLS handshake
A key of 128 bits or 16 bytes should be sufficient for this purpose.
Except for the RSA-EXPORT which is only enabled in EXPORT level.
It depends on the group used. Primes with lesser bits are always faster, but also easier to break. See Selecting cryptographic key sizes for the acceptable security levels.
such as the
gnutls_certificate_credentials_t
structures
See http://lists.gnu.org/archive/html/gnutls-devel/2011-02/msg00079.html.
Check http://home.gna.org/cryptodev-linux/
for the Linux kernel implementation of /dev/crypto
.