![[*]](crossref.png)
GNUTLS
[RE] [LO] [RO,LE] [C]
This document tries to be self contained, although basic network programming and PKI knowlegde is assumed in most of it. [6] is a good introduction to Public Key Infrastructure.
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 TLS 1.01.1 and SSL 3.0 protocols, accompanied with the required framework for authentication and public key infrastructure. The library is available under the GNU Lesser GPL license1.2. Important features of the GnuTLS library include:
Additionally GnuTLS provides a limited emulation API for the widely used OpenSSL1.3 library, to ease integration with existing applications.
GnuTLS consists of three independent parts, namely the ``TLS protocol part'', the ``Certificate part'', and the ``Crypto backend'' 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 which is partially implemented in the GnuTLS library. The Libtasn11.4a library which offers ASN.1 parsing capabilities, is used for the X.509 certificate parsing functions, and Opencdk1.5is used for the OpenPGP key support in GnuTLS. The `Crypto backend' is provided by the libgcrypt1.6library.
In order to ease integration in embedded systems, parts of the GnuTLS library can be disabled at compile time. That way a small library, with the required features, can be generated.
.
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 some structures needed for the ASN.1 parser. This structure is never modified by any GnuTLS function, except for the deinitialization function which frees all memory allocated in the global structure and is called after the program has permanently finished using GnuTLS.
The credentials structure is used by some authentication methods, such as certificate authentication1.7. A credentials structure may contain certificates, private keys, temporary parameters for diffie hellman or RSA key exchange, and other stuff that may be shared between several TLS sessions.
This structure should be initialized using the appropriate initialization functions. For example an application which uses certificate authentication would probably initialize the credentials, using the appropriate functions, and put its trusted certificates in this structure. The next step is to associate the credentials structure with each TLS session.
A GnuTLS session contains all the required stuff for a session to handle one secure connection. This session calls directly to the transport layer functions, in order to communicate with the peer. Every session has a unique session ID shared with the peer.
Since TLS sessions can be resumed, servers would probably need a database backend to hold the session's parameters. Every GnuTLS session after a successful handshake calls the appropriate backend function1.8 to store the newly negotiated session. The session database is examined by the server just after having received the client hello1.9, 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.
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. An example of a fatal error code is GNUTLS_E_DECRYPTION_FAILED. Non-fatal errors may warn about something, ie 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 .
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. All the error codes are documented
in appendix B on page .
GnuTLS internally handles heap allocated objects differently, depending on the sensitivity of the data they contain. However for performance reasons, the default memory functions do not overwrite sensitive data from memory, nor protect such objects from being written to the swap. In order to change the default behavior the gnutls_global_set_mem_functions function is available which can be used to set other memory handlers than the defaults.
The libgcrypt library on which GnuTLS depends, has such secure memory allocation functions available. These should be used in cases where even the system's swap memory is not considered secure. See the documentation of libgcrypt for more information.
There are several cases where GnuTLS may need some 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.
Other callback functions such as the one set by gnutls_srp_set_server_credentials_function , may require more complicated input, including data to be allocated. These callbacks should allocate and free memory using the functions shown below.
TLS stands for 'Transport Layer Security' and is the successor of SSL, the Secure Sockets Layer protocol2.1 designed by Netscape. TLS 1.0 is an Internet protocol, defined by IETF2.2, described in [4] and also in [16]. The protocol provides confidentiality, and authentication layers over any reliable transport layer. The description, below, refers to TLS 1.0 but also applies to SSL 3.0 since the differences of these protocols are minor. Older protocols such as SSL 2.0 are not discussed nor implemented in GnuTLS since they are not considered secure today.
TLS 1.0 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 section 2.4 on page 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 section 2.5 on page for more information
about the handshake protocol.
The protocol layering in TLS is shown at figure.
TLS is not limited to one transport layer, it can be used above any transport layer, as long as it is a reliable one. A set of functions is provided and their purpose is to load to GnuTLS the required callbacks to access the transport layer.
These functions accept a callback function as a parameter. The callback functions should return the number of bytes written, or -1 on error and should set errno appropriately.
GnuTLS currently only interprets the EINTR and EAGAIN errno values and returns the corresponding GnuTLS error codes GNUTLS_E_INTERRUPTED and GNUTLS_E_AGAIN. These values are usually returned by interrupted system calls, or when non blocking IO is used. All GnuTLS functions can be resumed (called again), if any of these error codes is returned. The error codes above refer to the system call, not the GnuTLS function, since signals do not interrupt GnuTLS' functions.
By default, if the transport functions are not set, GnuTLS will use the Berkeley Sockets functions. In this case GnuTLS will use some hacks in order for select() to work, thus making it easy to add TLS support to existing TCP/IP servers.
The Record protocol is the secure communications provider. Its purpose is to encrypt, authenticate and -optionally- compress packets. The following functions are available:
As you may have already noticed, the functions which access the Record protocol, are quite limited, given the importance of this protocol in TLS. 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.
The included algorithms perform really good when text, or other compressable data are to be transfered, 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. As a drawback, compression increases latency.
The record layer compression in GnuTLS is implemented based on the paper [7].
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 which is implemented in GnuTLS. For a detailed discussion see the archives of the TLS Working Group mailing list and the paper [12].
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 (see GNUTLS_A_CLOSE_NOTIFY), and others refer to the application protocol solely (see 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 renegotiations using the current session ID.
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.
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. Available functions to control the handshake protocol include:
The Handshake Protocol of TLS 1.0 negotiates cipher suites
of the form
TLS_DHE_RSA_WITH_3DES_CBC_SHA.
The usual cipher suites contain these parameters:
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.
The priority functions, dicussed above, allow the application layer to enable
and set priorities on the individual ciphers. It may imply that all combinations of ciphersuites
are allowed, but this is not true. For several reasons, not discussed here, some combinations
were not defined in the TLS protocol. The supported ciphersuites are shown
in appendix C on page .
The gnutls_handshake function, is expensive since a lot of calculations are performed. In order to support many fast connections to the same server a client may use session resuming. Session resuming 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 using the previously established keys. GnuTLS supports this feature, and the example resume client illustrates a typical use of it.
Keep in mind that sessions are expired after some time, for security reasons, thus it may be normal for a server not to resume a session even if you requested that. Also note that you must enable, using the priority functions, at least the algorithms used in the last session.
The server side is different. A server has to specify some callback functions which store, retrieve and delete session data. These can be registered with:
It might also be useful to be able to check for expired sessions in order to remove them, and save space. The function gnutls_db_check_entry is provided for that reason.
A number of extensions to the TLS protocol have been proposed mainly in [2]. The extensions supported in GnuTLS are
This extension allows a TLS 1.0 implementation to negotiate a smaller value for record packet maximum length. This extension may be useful to clients with constrained capabilities. See the gnutls_record_set_max_size and the gnutls_record_get_max_size functions.
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.
The TLS protocol provides confidentiality and encryption, but also offers authentication, which is a prerequisite for a secure connection. The available authentication methods in GnuTLS are:
X.509 certificates contain the public parameters,
of a public key algorithm, and an authority's signature, which proves the
authenticity of the parameters.
See section 4.1 on page for more information
on X.509 protocols.
OpenPGP keys also contain public parameters of a public key algorithm, and signatures from several other parties. Depending on whether a signer is trusted the key is considered trusted or not. GnuTLS's OpenPGP authentication implementation is based on the [11] proposal.
See 4.2 on page for more information
about the OpenPGP trust model. For a more detailed introduction to OpenPGP
and GnuPG see [1].
In GnuTLS both the OpenPGP and X.509 certificates are part of the certificate authentication and thus are handled using a common API.
When using certificates the server is required to have at least one certificate and private key pair. A client may or may not have such a pair. The certificate and key pair should be loaded, before any TLS session is initialized, in a certificate credentials structure. This should be done by using gnutls_certificate_set_x509_key_file or gnutls_certificate_set_openpgp_key_file depending on the certificate type. In the X.509 case, the functions will also accept and use a certificate list that leads to a trusted authority. The certificate list 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.
As an alternative, a callback may be used so the server or the client specify the certificate and the key at the handshake time. That callback can be set using the functions:
Certificate verification is possible by loading the trusted authorities into the credentials structure by using gnutls_certificate_set_x509_trust_file or gnutls_certificate_set_openpgp_keyring_file for openpgp keys. Note however that the peer's certificate is not automatically verified, you should call gnutls_certificate_verify_peers , after a successful handshake, to verify the signatures of the certificate. An alternative way, which reports a more detailed verification output, is to use gnutls_certificate_get_peers to obtain the raw certificate of the peer and verify it using the functions discussed in section 4.1 on page.
In a handshake, the negotiated cipher suite depends on the certificate's parameters, so not all key exchange methods will be available with some 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, but only the DHE_RSA ones. It is recommended not to use RSA keys for both signing and encryption. If possible use the same key for the DHE_RSA and RSA_EXPORT ciphersuites, which use signing, and a different key for the plain RSA ciphersuites, which use encryption. All the key exchange methods shown in figure are available in certificate authentication.
Note that the DHE key exchange methods are generally slower3.1 than plain RSA and require Diffie Hellman parameters to be generated and associated with a credentials structure. The RSA-EXPORT method also requires 512 bit RSA parameters, that should also be generated and associated with the credentials structure. See the functions:
Note that the key exchange methods for anonymous authentication require Diffie Hellman parameters to be generated and associated with an anonymous credentials structure.
Authentication using the SRP3.2protocol is actually password authentication. The two 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 schemas, is that 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 ``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. See [18] for a detailed description of the SRP protocol and the Stanford SRP libraries, which includes a PAM module that synchronizes the system's users passwords with the SRP password files. That way SRP authentication could be used for all the system's users.
The implementation in GnuTLS is based on paper [17]. The available key exchange methods are shown in figure.
If clients supporting SRP know the username and password before the connection, should initialize the client credentials and call the function gnutls_srp_set_client_credentials . Alternatively they could specify a callback function by using the function gnutls_srp_set_client_credentials_function . This has the advantage that allows probing the server for SRP support. In that case the callback function will be called twice per handshake. The first time is before the ciphersuite is negotiated, and if the callback returns a negative error code, the callback will be called again if SRP has been negotiated. This uses a special TLS-SRP handshake idiom in order to avoid, in interactive applications, to ask the user for SRP password and username if the server does not negotiate an SRP ciphersuite.
In server side the default behaviour of GnuTLS is to read the usernames and SRP verifiers from password files. These password files are the ones used by the Stanford srp libraries and can be specified using the gnutls_srp_set_server_credentials_file . If a different password file format is to be used, then the function gnutls_srp_set_server_credentials_function , should be called, in order to set an appropriate callback.
Some helper functions such as
are included in GnuTLS, and may be used to generate, and maintain SRP verifiers, and password files. A program to manipulate the required parameters for SRP authentication is also included. See section 7.1 on page for more information.
Several parameters such as the ones used for Diffie-Hellman authentication are stored within the credentials structures, so all sessions can access them. Those parameters are stored in structures such as gnutls_dh_params and gnutls_rsa_params, and functions like gnutls_certificate_set_dh_params and gnutls_certificate_set_rsa_export_params can be used to associate those parameters with the given credentials structure.
Since those parameters need to be renewed from time to time and a global structure such as the credentials, may not be easy to modify since it is accessible by all sessions, an alternative interface is available using a callback function. This can be set using the gnutls_certificate_set_params_function . An example is shown below.
![\includegraphics[height=8cm,width=12cm]{internals}](img1.png)
![\includegraphics[height=8cm,width=12cm]{layers}](img2.png)
#include <gnutls.h>
gnutls_rsa_params rsa_params;
gnutls_dh_params dh_params;
/* This function will be called once a session requests DH
* or RSA parameters. The parameters returned (if any) will
* be used for the first handshake only.
*/
static int get_params( gnutls_session session, gnutls_params_type type,
gnutls_params_st *st)
{
if (type == GNUTLS_PARAMS_RSA_EXPORT)
st->params.rsa_export = rsa_params;
else if (type == GNUTLS_PARAMS_DH)
st->params.dh = dh_params;
else return -1;
st->type = type;
/* do not deinitialize those parameters.
*/
st->deinit = 0;
return 0;
}
int main()
{
gnutls_certificate_credentials cert_cred;
initialize_params();
/* ...
*/
gnutls_certificate_set_params_function( cert_cred, get_params);
}
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. See figure 4.1 for a typical example.
The API for handling X.509 certificates is described at section 8.2
on page . Some examples are listed below.
| version | the field that indicates the version of the certificate. |
| serialNumber | this field holds a unique serial number per certificate. |
| issuer | holds the issuer's distinguished name |
| validity | the activation and expiration dates. |
| subject | the subject's distinguished name of the certificate. |
| [gray]0.9 extensions | The extensions are fields only present in version 3 certificates. |
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
IDs 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 the table below.
| 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. |
| CRL distribution points | 2.5.29.31 | This extension is set by the CA, in order to inform about the issued CRLs. |
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 section 6.5.2 on
page .
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. See [15] and section 6.3.3
on page for an example.
In GnuTLS the PKCS #10 structures are handled using the
gnutls_x509_crq_t type.
An example of a certificate request generation can be found at section 6.5.3
on page .
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. An Bag of type encrypted should be decrypted in order for its data to be accessed.
An example of a PKCS #12 structure generation can be found at section 6.5.4
on page .
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's else 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: If David trusts Alice to be an introducer, and Alice signed Bob's key, Dave also 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.
There are two verification functions in GnuTLS,
The gnutls_openpgp_key_verify_ring
and the gnutls_openpgp_key_verify_trustdb
.
The first one 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 is shown in figure 4.3.
The latter function checks a GnuPG trust database for the given key. This function does not
check the key signatures, only checks for disabled and revoked keys.
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 HTTPS5.1 protocol [15].
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 work5.2. 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.
This method is used by almost all modern protocols and there is even the [9] paper which proposes extensions to HTTP to support it.
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 thought 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 file5.4, or anything else!
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.
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.
The extra functionality of the GnuTLS-extra library is available by including the header file `gnutls/extra.h' in your programs.
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, GnuTLS ships with two small helper programs ``libgnutls-config'' and ``libgnutls-extra-config'' that knows about 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 libgnutls-config . The following example shows how it can be used at the command line:
gcc -c foo.c `libgnutls-config --cflags`
Adding the output of ``libgnutls-config -cflags'' to the compilers command line will ensure that the compiler can find the GnuTLS 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 ``libgnutls-config'' can be used. For convenience, this option also outputs all other options that are required to link the program with the GnuTLS libararies. The example shows how to link `foo.o' with the GnuTLS libraries to a program foo.
gcc -o foo foo.o `libgnutls-config --libs`
Of course you can also combine both examples to a single command by specifying both options to `libgnutls-config':
gcc -o foo foo.c `libgnutls-config --cflags --libs`
Although the GnuTLS library is thread safe by design, some parts of the crypto backend, such as the random generator, are not. Since libgcrypt 1.1.92 there was an automatic detection of the thread library used by the application, so most applications wouldn't need to do any changes to ensure thread-safety. Due to the unportability of the automatic thread detection, this was removed from later releases of libgcrypt, so applications have now to register callback functions to ensure proper locking in sensitive parts of libgcrypt.
There are helper macros to help you properly initialize the libraries. Examples are shown below.
![\includegraphics[height=9.5cm,width=7cm]{x509-1}](img10.png)
![\includegraphics[height=9cm,width=11cm]{pgp-fig1}](img12.png)
#include <gnutls.h>
#include <gcrypt.h>
#include <errno.h>
#include <pthread.h>
GCRY_THREAD_OPTION_PTHREAD_IMPL;
int main()
{
/* The order matters.
*/
gcry_control (GCRYCTL_SET_THREAD_CBS, &gcry_threads_pthread);
gnutls_global_init();
}
#include <gnutls.h>
#include <gcrypt.h>
#include <errno.h>
#include <pth.h>
GCRY_THREAD_OPTION_PTH_IMPL;
int main()
{
gcry_control (GCRYCTL_SET_THREAD_CBS, &gcry_threads_pth);
gnutls_global_init();
}
/* The gcry_thread_cbs structure must have been
* initialized.
*/
static struct gcry_thread_cbs gcry_threads_other = { ... };
int main()
{
gcry_control (GCRYCTL_SET_THREAD_CBS, &gcry_threads_other);
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
/* A very basic TLS client.
*/
#define MAX_BUF 1024
#define CAFILE "ca.pem"
#define SA struct sockaddr
#define MSG "GET / HTTP/1.0\r\n\r\n"
/* Connects to the peer and returns a socket
* descriptor.
*/
int tcp_connect( void)
{
const char *PORT = "443";
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, (SA *) & sa, sizeof(sa));
if (err < 0) {
fprintf(stderr, "Connect error\n");
exit(1);
}
return sd;
}
/* closes the given socket descriptor.
*/
void tcp_close( int sd)
{
shutdown(sd, SHUT_RDWR); /* no more receptions */
close(sd);
}
int main()
{
int ret, sd, ii;
gnutls_session session;
char buffer[MAX_BUF + 1];
gnutls_certificate_credentials xcred;
/* Allow connections to servers that have OpenPGP keys as well.
*/
const int cert_type_priority[3] = { GNUTLS_CRT_X509,
GNUTLS_CRT_OPENPGP, 0 };
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);
/* Initialize TLS session
*/
gnutls_init(&session, GNUTLS_CLIENT);
/* Use default priorities */
gnutls_set_default_priority(session);
gnutls_certificate_type_set_priority(session, cert_type_priority);
/* 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)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_global_deinit();
return 0;
}
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
extern void print_x509_certificate_info(gnutls_session);
/* This function will print some details of the
* given session.
*/
int print_info(gnutls_session session)
{
const char *tmp;
gnutls_credentials_type cred;
gnutls_kx_algorithm kx;
/* 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_ANON: /* anonymous authentication */
printf("- Anonymous DH using prime of %d bits\n",
gnutls_dh_get_prime_bits(session));
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) {
printf("\n- Ephemeral DH using prime of %d bits\n",
gnutls_dh_get_prime_bits(session));
}
/* if the certificate list is available, then
* print some information about it.
*/
print_x509_certificate_info(session);
} /* switch */
/* 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;
}
#include <stdio.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
/* All the available CRLs
*/
extern gnutls_x509_crl* crl_list;
extern int crl_list_size;
/* All the available trusted CAs
*/
extern gnutls_x509_crt* ca_list;
extern int ca_list_size;
static void verify_cert2(gnutls_x509_crt crt,
gnutls_x509_crt issuer, gnutls_x509_crl * crl_list, int crl_list_size);
static void verify_last_cert(gnutls_x509_crt crt,
gnutls_x509_crt *ca_list, int ca_list_size,
gnutls_x509_crl * crl_list, int crl_list_size);
/* This function will try to verify the peer's certificate chain, and
* also check if the hostname matches, and the activation, expiration dates.
*/
void verify_certificate_chain( gnutls_session session, const char* hostname,
const gnutls_datum* cert_chain, int cert_chain_length)
{
int i, ret;
gnutls_x509_crt 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);
}
/* Now verify the certificates against their issuers
* in the chain.
*/
for (i=1;i<cert_chain_length;i++) {
verify_cert2( cert[i-1], cert[i], crl_list, crl_list_size);
}
/* Here we must verify the last certificate in the chain against
* our trusted CA list.
*/
verify_last_cert( cert[cert_chain_length-1],
ca_list, ca_list_size, crl_list, crl_list_size);
/* 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);
}
for (i=0;i<cert_chain_length;i++)
gnutls_x509_crt_deinit( cert[i]);
return;
}
/* Verifies a certificate against an other certificate
* which is supposed to be it's issuer. Also checks the
* crl_list if the certificate is revoked.
*/
static void verify_cert2(gnutls_x509_crt crt,
gnutls_x509_crt issuer, gnutls_x509_crl * crl_list, int crl_list_size)
{
unsigned int output;
int ret;
time_t now = time(0);
size_t name_size;
char name[64];
/* Print information about the certificates to
* be checked.
*/
name_size = sizeof(name);
gnutls_x509_crt_get_dn( crt, name, &name_size);
fprintf(stderr, "\nCertificate: %s\n", name);
name_size = sizeof(name);
gnutls_x509_crt_get_issuer_dn(crt, name, &name_size);
fprintf(stderr, "Issued by: %s\n", name);
/* Get the DN of the issuer cert.
*/
name_size = sizeof(name);
gnutls_x509_crt_get_dn(issuer, name, &name_size);
fprintf(stderr, "Checking against: %s\n", name);
/* Do the actual verification.
*/
gnutls_x509_crt_verify(crt, &issuer, 1, 0, &output);
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");
fprintf(stderr, "\n");
} else
fprintf(stderr, "Trusted\n");
/* Now check the expiration dates.
*/
if (gnutls_x509_crt_get_activation_time(crt) > now)
fprintf(stderr, "Not yet activated\n");
if (gnutls_x509_crt_get_expiration_time(crt) < now)
fprintf(stderr, "Expired\n");
/* Check if the certificate is revoked.
*/
ret = gnutls_x509_crt_check_revocation(crt, crl_list, crl_list_size);
if (ret == 1) { /* revoked */
fprintf(stderr, "Revoked\n");
}
}
/* Verifies a certificate against the trusted CA list.
* Also checks the crl_list if the certificate is revoked.
*/
static void verify_last_cert(gnutls_x509_crt crt,
gnutls_x509_crt *ca_list, int ca_list_size,
gnutls_x509_crl * crl_list, int crl_list_size)
{
unsigned int output;
int ret;
time_t now = time(0);
size_t name_size;
char name[64];
/* Print information about the certificates to
* be checked.
*/
name_size = sizeof(name);
gnutls_x509_crt_get_dn( crt, name, &name_size);
fprintf(stderr, "\nCertificate: %s\n", name);
name_size = sizeof(name);
gnutls_x509_crt_get_issuer_dn(crt, name, &name_size);
fprintf(stderr, "Issued by: %s\n", name);
/* Do the actual verification.
*/
gnutls_x509_crt_verify(crt, ca_list, ca_list_size, 0, &output);
if (output & GNUTLS_CERT_INVALID) {
fprintf(stderr, "Not trusted");
if (output & GNUTLS_CERT_SIGNER_NOT_CA)
fprintf(stderr, ": Issuer is not a CA\n");
else
fprintf(stderr, "\n");
} else
fprintf(stderr, "Trusted\n");
/* Now check the expiration dates.
*/
if (gnutls_x509_crt_get_activation_time(crt) > now)
fprintf(stderr, "Not yet activated\n");
if (gnutls_x509_crt_get_expiration_time(crt) < now)
fprintf(stderr, "Expired\n");
/* Check if the certificate is revoked.
*/
ret = gnutls_x509_crt_check_revocation(crt, crl_list, crl_list_size);
if (ret == 1) { /* revoked */
fprintf(stderr, "Revoked\n");
}
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
/* A TLS client that loads the certificate and key.
*/
#define MAX_BUF 1024
#define SA struct sockaddr
#define MSG "GET / HTTP/1.0\r\n\r\n"
#define CERT_FILE "cert.pem"
#define KEY_FILE "key.pem"
#define CAFILE "ca.pem"
static int cert_callback(gnutls_session session,
const gnutls_datum* req_ca_rdn, int nreqs,
const gnutls_pk_algorithm* sign_algos, int sign_algos_length,
gnutls_retr_st * st);
gnutls_x509_crt crt;
gnutls_x509_privkey key;
/* Helper functions to load a certificate and key
* files into memory. They use mmap for simplicity.
*/
static gnutls_datum mmap_file( const char* file)
{
int fd;
gnutls_datum mmaped_file = { NULL, 0 };
struct stat stat_st;
void* ptr;
fd = open( file, 0);
if (fd==-1) return mmaped_file;
fstat( fd, &stat_st);
if ((ptr=mmap( NULL, stat_st.st_size, PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED)
return mmaped_file;
mmaped_file.data = ptr;
mmaped_file.size = stat_st.st_size;
return mmaped_file;
}
static void munmap_file( gnutls_datum data)
{
munmap( data.data, data.size);
}
/* Load the certificate and the private key.
*/
static void load_keys( void)
{
int ret;
gnutls_datum data;
data = mmap_file( CERT_FILE);
if (data.data == NULL) {
fprintf(stderr, "*** Error loading cert file.\n");
exit(1);
}
gnutls_x509_crt_init( &crt);
ret = gnutls_x509_crt_import( crt, &data, GNUTLS_X509_FMT_PEM);
if (ret < 0) {
fprintf(stderr, "*** Error loading key file: %s\n", gnutls_strerror(ret));
exit(1);
}
munmap_file( data);
data = mmap_file( KEY_FILE);
if (data.data == NULL) {
fprintf(stderr, "*** Error loading key file.\n");
exit(1);
}
gnutls_x509_privkey_init( &key);
ret = gnutls_x509_privkey_import( key, &data, GNUTLS_X509_FMT_PEM);
if (ret < 0) {
fprintf(stderr, "*** Error loading key file: %s\n", gnutls_strerror(ret));
exit(1);
}
munmap_file( data);
}
int main()
{
int ret, sd, ii;
gnutls_session session;
char buffer[MAX_BUF + 1];
gnutls_certificate_credentials xcred;
/* Allow connections to servers that have OpenPGP keys as well.
*/
gnutls_global_init();
load_keys();
/* 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_client_set_retrieve_function( xcred, cert_callback);
/* Initialize TLS session
*/
gnutls_init(&session, GNUTLS_CLIENT);
/* Use default priorities */
gnutls_set_default_priority(session);
/* 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)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_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 session,
const gnutls_datum* req_ca_rdn, int nreqs,
const gnutls_pk_algorithm* sign_algos, int sign_algos_length,
gnutls_retr_st * st)
{
char issuer_dn[256];
int i, ret;
size_t len;
gnutls_certificate_type 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) {
st->type = type;
st->ncerts = 1;
st->cert.x509 = &crt;
st->key.x509 = key;
st->deinit_all = 0;
} else {
return -1;
}
return 0;
}
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
/* Those functions are defined in other examples.
*/
extern void check_alert(gnutls_session session, int ret);
extern int tcp_connect( void);
extern void tcp_close( int sd);
#define MAX_BUF 1024
#define CRLFILE "crl.pem"
#define CAFILE "ca.pem"
#define SA struct sockaddr
#define MSG "GET / HTTP/1.0\r\n\r\n"
int main()
{
int ret;
int sd, ii, alert;
gnutls_session session;
char buffer[MAX_BUF + 1];
gnutls_certificate_credentials xcred;
/* variables used in session resuming
*/
int t;
char *session_data;
size_t session_data_size;
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_set_default_priority(session);
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)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");
}
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;
}
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/extra.h>
/* Those functions are defined in other examples.
*/
extern void check_alert(gnutls_session 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 "ca.pem"
#define SA struct sockaddr
#define MSG "GET / HTTP/1.0\r\n\r\n"
const int kx_priority[] = { GNUTLS_KX_SRP, GNUTLS_KX_SRP_DSS,
GNUTLS_KX_SRP_RSA, 0 };
int main()
{
int ret;
int sd, ii;
gnutls_session session;
char buffer[MAX_BUF + 1];
gnutls_srp_client_credentials srp_cred;
gnutls_certificate_client_credentials cert_cred;
gnutls_global_init();
/* now enable the gnutls-extra library which contains the
* SRP stuff.
*/
gnutls_global_init_extra();
gnutls_srp_allocate_client_credentials(&srp_cred);
gnutls_certificate_allocate_client_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_set_default_priority(session);
gnutls_kx_set_priority(session, kx_priority);
/* 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)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 (gnutls_error_is_fatal(ret) == 1 || 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, 0);
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;
}
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
#define KEYFILE "key.pem"
#define CERTFILE "cert.pem"
#define CAFILE "ca.pem"
#define CRLFILE "crl.pem"
/* This is a sample TLS 1.0 echo server.
*/
#define SA struct sockaddr
#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 x509_cred;
gnutls_session initialize_tls_session()
{
gnutls_session session;
gnutls_init(&session, GNUTLS_SERVER);
/* avoid calling all the priority functions, since the defaults
* are adequate.
*/
gnutls_set_default_priority( session);
gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, x509_cred);
/* request client certificate if any.
*/
gnutls_certificate_server_set_request( session, GNUTLS_CERT_REQUEST);
gnutls_dh_set_prime_bits( session, DH_BITS);
return session;
}
static gnutls_dh_params 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()
{
int err, listen_sd, i;
int sd, ret;
struct sockaddr_in sa_serv;
struct sockaddr_in sa_cli;
int client_len;
char topbuf[512];
gnutls_session 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_trust_file(x509_cred, CAFILE,
GNUTLS_X509_FMT_PEM);
gnutls_certificate_set_x509_crl_file(x509_cred, CRLFILE,
GNUTLS_X509_FMT_PEM);
gnutls_certificate_set_x509_key_file(x509_cred, CERTFILE, KEYFILE,
GNUTLS_X509_FMT_PEM);
generate_dh_params();
gnutls_certificate_set_dh_params( x509_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, &optval, sizeof(int));
err = bind(listen_sd, (SA *) & 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, (SA *) & 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)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); */
i = 0;
for (;;) {
bzero(buffer, 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");
gnutls_bye( session, GNUTLS_SHUT_WR); /* do not wait for
* the peer to close the connection.
*/
close(sd);
gnutls_deinit(session);
}
close(listen_sd);
gnutls_certificate_free_credentials(x509_cred);
gnutls_global_deinit();
return 0;
}
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
#define KEYFILE "key.pem"
#define CERTFILE "cert.pem"
#define CAFILE "ca.pem"
#define CRLFILE "crl.pem"
/* This is a sample TLS 1.0 echo server.
* Export-grade ciphersuites and session resuming are supported.
*/
#define SA struct sockaddr
#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 cert_cred;
static void wrap_db_init(void);
static void wrap_db_deinit(void);
static int wrap_db_store(void *dbf, gnutls_datum key, gnutls_datum data);
static gnutls_datum wrap_db_fetch(void *dbf, gnutls_datum key);
static int wrap_db_delete(void *dbf, gnutls_datum key);
#define TLS_SESSION_CACHE 50
gnutls_session initialize_tls_session()
{
gnutls_session session;
gnutls_init(&session, GNUTLS_SERVER);
/* Use the default priorities, plus, export cipher suites.
*/
gnutls_set_default_export_priority(session);
gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, cert_cred);
/* request client certificate if any.
*/
gnutls_certificate_server_set_request(session, GNUTLS_CERT_REQUEST);
gnutls_dh_set_prime_bits(session, DH_BITS);
if (TLS_SESSION_CACHE != 0) {
gnutls_db_set_retrieve_function(session, wrap_db_fetch);
gnutls_db_set_remove_function(session, wrap_db_delete);
gnutls_db_set_store_function(session, wrap_db_store);
gnutls_db_set_ptr(session, NULL);
}
return session;
}
gnutls_dh_params dh_params;
/* Export-grade cipher suites require temporary RSA
* keys.
*/
gnutls_rsa_params rsa_params;
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. Depends on the
* security requirements.
*/
gnutls_dh_params_init(&dh_params);
gnutls_dh_params_generate2( dh_params, DH_BITS);
return 0;
}
static int generate_rsa_params(void)
{
gnutls_rsa_params_init(&rsa_params);
/* Generate RSA parameters - for use with RSA-export
* cipher suites. These should be discarded and regenerated
* once a day, once every 500 transactions etc. Depends on the
* security requirements.
*/
gnutls_rsa_params_generate2( rsa_params, 512);
return 0;
}
int main()
{
int err, listen_sd, i;
int sd, ret;
struct sockaddr_in sa_serv;
struct sockaddr_in sa_cli;
int client_len;
char topbuf[512];
gnutls_session 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(&cert_cred);
gnutls_certificate_set_x509_trust_file(cert_cred, CAFILE,
GNUTLS_X509_FMT_PEM);
gnutls_certificate_set_x509_crl_file(cert_cred, CRLFILE,
GNUTLS_X509_FMT_PEM);
gnutls_certificate_set_x509_key_file(cert_cred, CERTFILE, KEYFILE,
GNUTLS_X509_FMT_PEM);
generate_dh_params();
generate_rsa_params();
if (TLS_SESSION_CACHE != 0) {
wrap_db_init();
}
gnutls_certificate_set_dh_params(cert_cred, dh_params);
gnutls_certificate_set_rsa_export_params(cert_cred, rsa_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, &optval, sizeof(int));
err = bind(listen_sd, (SA *) & 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, (SA *) & 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)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");
/* print_info(session); */
i = 0;
for (;;) {
bzero(buffer, MAX_BUF + 1);
ret = gnutls_record_recv(session, buffer, MAX_BUF);
if (ret == 0) {
printf("\n- Peer has closed the TLS 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");
gnutls_bye(session, GNUTLS_SHUT_WR); /* do not wait for
* the peer to close the connection.
*/
close(sd);
gnutls_deinit(session);
}
close(listen_sd);
gnutls_certificate_free_credentials(cert_cred);
gnutls_global_deinit();
return 0;
}
/* Functions and other stuff needed for session resuming.
* This is done using a very simple list which holds session ids
* and session data.
*/
#define MAX_SESSION_ID_SIZE 32
#define MAX_SESSION_DATA_SIZE 512
typedef struct {
char session_id[MAX_SESSION_ID_SIZE];
int session_id_size;
char session_data[MAX_SESSION_DATA_SIZE];
int session_data_size;
} CACHE;
static CACHE *cache_db;
static int cache_db_ptr = 0;
static void wrap_db_init(void)
{
/* allocate cache_db */
cache_db = calloc(1, TLS_SESSION_CACHE * sizeof(CACHE));
}
static void wrap_db_deinit(void)
{
return;
}
static int wrap_db_store(void *dbf, gnutls_datum key, gnutls_datum data)
{
if (cache_db == NULL)
return -1;
if (key.size > MAX_SESSION_ID_SIZE)
return -1;
if (data.size > MAX_SESSION_DATA_SIZE)
return -1;
memcpy(cache_db[cache_db_ptr].session_id, key.data, key.size);
cache_db[cache_db_ptr].session_id_size = key.size;
memcpy(cache_db[cache_db_ptr].session_data, data.data, data.size);
cache_db[cache_db_ptr].session_data_size = data.size;
cache_db_ptr++;
cache_db_ptr %= TLS_SESSION_CACHE;
return 0;
}
static gnutls_datum wrap_db_fetch(void *dbf, gnutls_datum key)
{
gnutls_datum res = { NULL, 0 };
int i;
if (cache_db == NULL)
return res;
for (i = 0; i < TLS_SESSION_CACHE; i++) {
if (key.size == cache_db[i].session_id_size &&
memcmp(key.data, cache_db[i].session_id, key.size) == 0) {
res.size = cache_db[i].session_data_size;
res.data = gnutls_malloc(res.size);
if (res.data == NULL)
return res;
memcpy(res.data, cache_db[i].session_data, res.size);
return res;
}
}
return res;
}
static int wrap_db_delete(void *dbf, gnutls_datum key)
{
int i;
if (cache_db == NULL)
return -1;
for (i = 0; i < TLS_SESSION_CACHE; i++) {
if (key.size == cache_db[i].session_id_size &&
memcmp(key.data, cache_db[i].session_id, key.size) == 0) {
cache_db[i].session_id_size = 0;
cache_db[i].session_data_size = 0;
return 0;
}
}
return -1;
}
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
/* Must be linked against gnutls-extra.
*/
#include <gnutls/extra.h>
#define KEYFILE "secret.asc"
#define CERTFILE "public.asc"
#define RINGFILE "ring.gpg"
/* This is a sample TLS 1.0-OpenPGP echo server.
*/
#define SA struct sockaddr
#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 cred;
const int cert_type_priority[2] = { GNUTLS_CRT_OPENPGP, 0 };
gnutls_dh_params dh_params;
/* Defined in a previous example */
extern int generate_dh_params( void);
extern gnutls_session initialize_tls_session( void);
int main()
{
int err, listen_sd, i;
int sd, ret;
struct sockaddr_in sa_serv;
struct sockaddr_in sa_cli;
int client_len;
char topbuf[512];
gnutls_session 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_certificate_set_openpgp_key_file( cred, CERTFILE, KEYFILE);
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, &optval, sizeof(int));
err = bind(listen_sd, (SA *) & 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();
gnutls_certificate_type_set_priority(session, cert_type_priority);
sd = accept(listen_sd, (SA *) & 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)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); */
i = 0;
for (;;) {
bzero(buffer, 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");
gnutls_bye( session, GNUTLS_SHUT_WR); /* do not wait for
* the peer to close the connection.
*/
close(sd);
gnutls_deinit(session);
}
close(listen_sd);
gnutls_certificate_free_credentials( cred);
gnutls_global_deinit();
return 0;
}
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
#include <gnutls/extra.h>
#define SRP_PASSWD "tpasswd"
#define SRP_PASSWD_CONF "tpasswd.conf"
#define KEYFILE "key.pem"
#define CERTFILE "cert.pem"
#define CAFILE "ca.pem"
/* This is a sample TLS-SRP echo server.
*/
#define SA struct sockaddr
#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 srp_cred;
gnutls_certificate_credentials cert_cred;
gnutls_session initialize_tls_session()
{
gnutls_session session;
const int kx_priority[] = { GNUTLS_KX_SRP, GNUTLS_KX_SRP_DSS,
GNUTLS_KX_SRP_RSA, 0 };
gnutls_init(&session, GNUTLS_SERVER);
gnutls_set_default_priority(session);
gnutls_kx_set_priority(session, kx_priority);
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()
{
int err, listen_sd, i;
int sd, ret;
struct sockaddr_in sa_serv;
struct sockaddr_in sa_cli;
int client_len;
char topbuf[512];
gnutls_session session;
char buffer[MAX_BUF + 1];
int optval = 1;
char name[256];
strcpy(name, "Echo Server");
/* these must be called once in the program
*/
gnutls_global_init();
gnutls_global_init_extra(); /* for SRP */
/* 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, &optval, sizeof(int));
err = bind(listen_sd, (SA *) & 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, (SA *) & 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)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");
/* print_info(session); */
i = 0;
for (;;) {
bzero(buffer, 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");
gnutls_bye( session, GNUTLS_SHUT_WR); /* do not wait for
* the peer to close the connection.
*/
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;
}
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.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 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));
}
}
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
static const char* bin2hex( const void* bin, size_t bin_size)
{
static char printable[110];
unsigned char *_bin = bin;
char* print;
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.
*/
static void print_x509_certificate_info(gnutls_session session)
{
char serial[40];
char dn[128];
int i;
size_t size;
unsigned int algo, bits;
time_t expiration_time, activation_time;
const gnutls_datum *cert_list;
int cert_list_size = 0;
gnutls_x509_crt cert;
/* 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) {
/* we only print information about the first certificate.
*/
gnutls_x509_crt_init( &cert);
gnutls_x509_crt_import( cert, &cert_list[0]);
printf("Certificate info:\n");
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);
size = sizeof( serial);
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);
}
}
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include <time.h>
/* This example will generate a private key and a certificate
* request.
*/
int main()
{
gnutls_x509_crq crq;
gnutls_x509_privkey key;
unsigned char buffer[10*1024];
int buffer_size = sizeof(buffer);
int ret;
gnutls_global_init();
/* Initialize an empty certificate request, and
* an empty private key.
*/
gnutls_x509_crq_init(&crq);
gnutls_x509_privkey_init(&key);
/* Generate a 1024 bit RSA private key.
*/
gnutls_x509_privkey_generate(key, GNUTLS_PK_RSA, 1024, 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_sign(crq, key);
/* 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;
}
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/pkcs12.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 * cert, const gnutls_datum * pkcs8_key,
const char *password)
{
gnutls_pkcs12 pkcs12;
int ret, bag_index;
gnutls_pkcs12_bag bag, key_bag;
char pkcs12_struct[10 * 1024];
int 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 key_id = { "\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));
exit(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));
exit(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));
exit(1);
}
fd = fopen(OUTFILE, "w");
if (fd == NULL) {
fprintf(stderr, "cannot open file\n");
exit(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);
}
To ease GnuTLS' integration with existing applications, a compatibility layer with the widely used OpenSSL library is included in the gnutls-openssl library. This compatibility layer is not complete and it is not intended to completely reimplement the OpenSSL API with GnuTLS. It only provides source-level compatibility. There is currently no attempt to make it binary-compatible with OpenSSL.
The prototypes for the compatibility functions are in the ``gnutls/openssl.h'' header file.
Current limitations imposed by the compatibility layer include:
The ``srptool'' is a very simple program that emulates the programs in the Stanford SRP libraries. It is intended for use in places where you don't expect SRP authentication to be the used for system users. Traditionally libsrp used two files. One called 'tpasswd' which holds usernames and verifiers, and 'tpasswd.conf' which holds generators and primes.
How to use srptool:
$ srptool --create-conf /etc/tpasswd.conf
$ srptool --passwd /etc/tpasswd \
--passwd-conf /etc/tpasswd.conf -u test
$ srptool --passwd /etc/tpasswd \
--passwd-conf /etc/tpasswd.conf --verify -u test
This program was created to assist in debugging GnuTLS, but it might be useful to extract a TLS server's capabilities. It's purpose is to connect onto a TLS server, perform some tests and print the server's capabilities. If called with the `-v' parameter a more checks will be performed. An example output is:
crystal:/cvs/gnutls/src$ ./gnutls-cli-debug localhost -p 5556 Resolving 'localhost'... Connecting to '127.0.0.1:5556'... Checking for TLS 1.1 support... yes Checking fallback from TLS 1.1 to... N/A Checking for TLS 1.0 support... yes Checking for SSL 3.0 support... yes Checking for version rollback bug in RSA PMS... no Checking for version rollback bug in Client Hello... no Checking whether we need to disable TLS 1.0... N/A 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 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... yes 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 AES cipher support (TLS extension)... yes Checking for 3DES 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 RIPEMD160 MAC support (TLS extension)... yes Checking for ZLIB compression support (TLS extension)... yes Checking for LZO compression support (GnuTLS extension)... yes Checking for max record size (TLS extension)... yes Checking for SRP authentication support (TLS extension)... yes Checking for OpenPGP authentication support (TLS extension)... no
This is a program to generate X.509 certificates, certificate requests, CRLs and private keys. The program can be used interactively or non interactively by specifying the -template command line option. See doc/certtool.cfg, in the distribution, for an example of a template file.
How to use certtool interactively:
$ certtool --generate-privkey --outfile ca-key.pem $ certtool --generate-self-signed --load-privkey ca-key.pem --outfile ca-cert.pemNote that a self-signed certificate usually belongs to a certificate authority, that signs other certificates.
$ certtool --generate-privkey --outfile key.pem
$ certtool --generate-request --load-privkey key.pem --outfile request.pem
$ certtool --generate-certificate --load-request request.pem --outfile cert.pem \ --load-ca-certificate ca-cert.pem --load-ca-privkey ca-key.pem
$ certtool --certificate-info --infile cert.pem
$ certtool --load-certificate cert.pem --load-privkey key.pem --to-p12 \ --outder --outfile key.p12
Certtool's template file format:
$ 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:
# 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" # 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." "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" # 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" # 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 # 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 prefered 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
Arguments
Description
This function clears all buffers associated with the session.
The difference with gnutls_deinit() is that this function will not
interfere with the session database.
Arguments
Description
Returns a string that describes the given alert number or NULL.
See gnutls_alert_get().
Arguments
Description
Returns the last alert number received. This function
should be called if GNUTLS_E_WARNING_ALERT_RECEIVED or
GNUTLS_E_FATAL_ALERT_RECEIVED has been returned by a gnutls function.
The peer may send alerts if he thinks some things were not
right. Check gnutls.h for the available alert descriptions.
Arguments
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 0 on success.
Arguments
Description
This structure is complex enough to manipulate directly thus
this helper function is provided in order to allocate it.
Arguments
Description
This structure is complex enough to manipulate directly thus
this helper function is provided in order to allocate it.
Arguments
Description
This structure is complex enough to manipulate directly thus
this helper function is provided in order to free (deallocate) it.
Arguments
Description
This structure is complex enough to manipulate directly thus
this helper function is provided in order to free (deallocate) it.
Arguments
Description
This function will set a callback in order for the server to get the
diffie hellman parameters for anonymous authentication. The callback should
return zero on success.
Arguments
Description
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.
Arguments
Description
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: KX_RSA, KX_DHE_RSA),
the same function are to be used to access the authentication data.
Arguments
Description
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 then the TLS connection gets terminated and
further receives and sends will be disallowed. If the return
value is zero you may continue using the connection.
GNUTLS_SHUT_RDWR actually sends an alert containing a close request
and waits for the peer to reply with the same message.
In case of GNUTLS_SHUT_WR then the TLS connection 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.
This function may also return GNUTLS_E_AGAIN or GNUTLS_E_INTERRUPTED; cf.
gnutls_record_get_direction().
Arguments
Description
This function will return the peer's certificate activation time.
This is the creation time for openpgp keys.
Returns (time_t) -1 on error.
Arguments
Description
This structure is complex enough to manipulate directly thus
this helper function is provided in order to allocate it.
Returns 0 on success.
Arguments
Description
This function will return 0 if the peer (server) did not request client
authentication or 1 otherwise.
Returns a negative value in case of an error.
Arguments
Description
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, const gnutls_datum* req_ca_dn, int nreqs,
gnutls_pk_algorithm* pk_algos, int pk_algos_length, gnutls_retr_st* st);
st should contain the certificates and private keys.
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.
If the callback function is provided then gnutls will call it, in the
handshake, after the certificate request message has been received.
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.
Arguments
Description
This function sets a callback to be called while selecting the (client) certificate.
The callback's function prototype is:
int (*callback)(gnutls_session, const gnutls_datum *client_cert, int ncerts, const gnutls_datum* req_ca_dn, int nreqs);
client_cert contains ncerts gnutls_datum structures which hold
the raw certificates (DER for X.509 or binary for OpenPGP), of the
client.
req_ca_dn, 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().
This function specifies what we, in case of a client, are going
to do when we have to send a certificate. If this callback
function is not provided then gnutls will automatically try to
find an appropriate certificate to send. The appropriate certificate
is chosen based on the CAs sent by the server, and the requested
public key algorithms.
If the callback function is provided then gnutls will call it, in the
handshake, after the certificate request message has been received.
The callback function should return the index of the certificate
choosen by the user. The index is relative to the certificates in the
callback's parameter. The value (-1) indicates that the user
does not want to use client authentication.
Arguments
Description
This function will return the peer's certificate expiration time.
Returns (time_t) -1 on error.
Arguments
Description
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.
CA names are used by servers to advertize the CAs they
support to clients.
Arguments
Description
This function will delete all the CAs associated
with the given credentials. Servers that do not use
gnutls_certificate_verify_peers() may call this to
save some memory.
Arguments
Description
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).
Arguments
Description
This function will delete all the CRLs associated
with the given credentials.
Arguments
Description
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.
Arguments
Description
This function will return the certificate as sent to the peer,
in the last handshake. These certificates are in raw format.
In X.509 this is a certificate list. In OpenPGP this is a single
certificate.
Returns NULL in case of an error, or if no certificate was used.
Arguments
Description
This function will return 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 raw encoded key is returned.
Returns NULL in case of an error, or if no certificate was sent.
Arguments
Description
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 advertize
it's trusted CAs to the peer. If status is zero then the default behaviour will
take effect, which is to advertize the server's trusted CAs.
This function has no effect in clients, and in authentication methods other than
certificate with X.509 certificates.
Arguments
Description
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.
Arguments
Description
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, gnutls_retr_st* st);
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.
The callback function should set the certificate list to be sent, and
return 0 on success. The value (-1) indicates error and the handshake
will be terminated.
Arguments
Description
This function sets a callback to be called while selecting the (server) certificate.
The callback's function form is:
int (*callback)(gnutls_session, gnutls_datum *server_cert, int ncerts);
server_cert contains ncerts gnutls_datum structures which hold
the raw certificate (DER encoded in X.509) of the server.
This function specifies what we, in case of a server, are going
to do when we have to send a certificate. If this callback
function is not provided then gnutls will automatically try to
find an appropriate certificate to send. (actually send the first in the list)
In case the callback returned a negative number then gnutls will
not attempt to choose the appropriate certificate and the caller function
will fail.
The callback function will only be called once per handshake.
The callback function should return the index of the certificate
choosen by the server. -1 indicates an error.
Arguments
Description
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.
Arguments
Description
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 zero on success.
Arguments
Description
This function will set the temporary RSA parameters for a certificate
server to use. These parameters will be used in RSA-EXPORT
cipher suites.
Arguments
Description
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.
Arguments
Description
This function will set some upper limits for the default verification function
(gnutls_certificate_verify_peers()) to avoid denial of service attacks.
Arguments
Description
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_peers().
This function may be called multiple times.
Returns the number of CRLs processed or a negative value
on error.
Arguments
Description
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_peers().
This function may be called multiple times.
Returns the number of CRLs processed or a negative value
on error.
Arguments
Description
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_peers().
This function may be called multiple times.
Returns 0 on success.
Arguments
Description
This function sets a certificate/private key pair in the
gnutls_certificate_credentials structure. This function may be called
more than once (in case multiple keys/certificates exist for the
server).
Currently only PKCS-1 encoded RSA and DSA private keys are accepted by
this function.
Arguments
Description
This function sets a certificate/private key pair in the
gnutls_certificate_credentials structure. This function may be called
more than once (in case multiple keys/certificates exist for the
server).
Currently are supported
RSA PKCS-1 encoded private keys,
DSA private keys.
DSA private keys are encoded the OpenSSL way, which is an ASN.1
DER sequence of 6 INTEGERs - version, p, q, g, pub, priv.
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.
Arguments
Description
This function sets a certificate/private key pair in the
gnutls_certificate_credentials structure. This function may be called
more than once (in case multiple keys/certificates exist for the
server).
Arguments
Description
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_peers().
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
value on error.
Arguments
Description
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_peers().
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
value on error.
Arguments
Description
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_peers().
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 0 on success.
Arguments
Description
Returns a string (or NULL) that contains the name
of the specified certificate type.
Arguments
Description
Returns the currently used certificate type. The certificate type
is by default X.509, unless it is negotiated as a TLS extension.
Arguments
Description
Sets the priority on the certificate types supported by gnutls.
Priority is higher for types 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.
Arguments
Description
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
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.
Returns a negative error code on error and zero on success.
This is the same as gnutls_x509_verify_certificate() and
uses the loaded CAs in the credentials as trusted CAs.
Arguments
Description
This function will try to verify the peer's certificate and return its status (trusted, invalid etc.).
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.
The return value should be one or more of the gnutls_certificate_status
enumerated elements bitwise or'd, or a negative error code on error.
This is the same as gnutls_x509_verify_certificate() and
uses the loaded CAs in the credentials as trusted CAs.
Arguments
Description
Check that the version of the library is at minimum the requested one
and return the version string; return NULL if the condition is not
satisfied. If a NULL is passed to this function, no check is done,
but the version string is simply returned.
Arguments
Description
Returns the length (in bytes) of the given cipher's key size.
Returns 0 if the given cipher is invalid.
Arguments
Description
Returns a pointer to a string that contains the name
of the specified cipher or NULL.
Arguments
Description
Returns the currently used cipher.
Arguments
Description
Sets the priority on the ciphers supported by gnutls.
Priority is higher for ciphers 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.
Arguments
Description
Returns a string that contains the name of a TLS
cipher suite, specified by the given algorithms, or NULL.
Note that the full cipher suite name must be prepended
by TLS or SSL depending of the protocol in use.
Arguments
Description
Returns a pointer to a string that contains the name
of the specified compression algorithm or NULL.
Arguments
Description
Returns the currently used compression method.
Arguments
Description
Sets the priority on the compression algorithms supported by gnutls.
Priority is higher for algorithms 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.
Arguments
Description
Clears all the credentials previously set in this session.
Arguments
Description
Sets the needed credentials for the specified type.
Eg username, password - or public and private keys etc.
The (void* 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 in case of a client.
In case of a server it should be gnutls_anon_server_credentials.
For GNUTLS_CRD_SRP cred should be gnutls_srp_client_credentials
in case of a client, and gnutls_srp_server_credentials, in case
of a server.
For GNUTLS_CRD_CERTIFICATE cred should be gnutls_certificate_credentials.
Arguments
Description
This function returns GNUTLS_E_EXPIRED, if the database entry
has expired or 0 otherwise. This function is to be used when
you want to clear unnesessary session which occupy space in your
backend.
Arguments
Description
Returns the pointer that will be sent to db store, retrieve and delete functions, as
the first argument.
Arguments
Description
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.
Arguments
Description
Sets the expiration time for resumed sessions. The default is 3600 (one hour)
at the time writing this.
Arguments
Description
Sets the pointer that will be provided to db store, retrieve and delete functions, as
the first argument.
Arguments
Description
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_function() will be null unless gnutls_db_set_ptr()
has been called.
Arguments
Description
Sets the function that will be used to retrieve data from the resumed
sessions database. This function must return a gnutls_datum containing the
data on success, or a gnutls_datum containing null and 0 on failure.
The datum's data must be allocated using the function
gnutls_malloc().
The first argument to store_function() will be null unless gnutls_db_set_ptr()
has been called.
Arguments
Description
Sets the function that will be used to store data from the resumed
sessions database. This function must remove 0 on success.
The first argument to store_function() will be null unless gnutls_db_set_ptr()
has been called.
Arguments
Description
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.
Arguments
Description
This function will return the bits used in the last Diffie Hellman authentication
with the peer. Should be used for both anonymous and ephemeral diffie Hellman.
Returns a negative value in case of an error.
Arguments
Description
This function will return the bits of the prime used in the last Diffie Hellman authentication
with the peer. Should be used for both anonymous and ephemeral diffie Hellman.
Returns a negative value in case of an error.
Arguments
Description
This function will return the bits used in the last Diffie Hellman authentication
with the peer. Should be used for both anonymous and ephemeral diffie Hellman.
Returns a negative value in case of an error.
Arguments
Description
This function will copy the DH parameters structure from source
to destination.
Arguments
Description
This function will deinitialize the DH parameters structure.
Arguments
Description
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".
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
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.
Arguments
Description
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.
Note that the bits value should be one of 768, 1024, 2048, 3072 or 4096.
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.
Arguments
Description
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".
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
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.
Arguments
Description
This function will initialize the DH parameters structure.
Arguments
Description
This function sets the number of bits, for use in an
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.
Arguments
Description
If a function returns a negative value you may feed that value
to this function to see if it is fatal. Returns 1 for a fatal
error 0 otherwise. However you may want to check the
error code manually, since some non-fatal errors to the protocol
may be fatal for you (your program).
This is only useful if you are dealing with errors from the
record layer or the handshake layer.
Arguments
Description
Returns 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 == GNUTLS_E_REHANDSHAKE, where a warning
alert should be sent to the peer indicating that no renegotiation will
be performed.
If the return value is GNUTLS_E_INVALID_REQUEST, then there was no
mapping to an alert.
Arguments
Description
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 a negative value in case of an error.
Arguments
Description
This function will free data pointed by ptr.
The deallocation function used is the one set by gnutls_global_set_mem_functions().
Arguments
Description
This function deinitializes the global data, that were initialized
using gnutls_global_init().
Arguments
Description
This function initializes the global data to defaults.
Every gnutls application has a global data which holds common parameters
shared by gnutls session structures.
You must call gnutls_global_deinit() when gnutls usage is no longer needed
Returns zero on success.
Note that this function will also initialize libgcrypt, if it has not
been initialized before. Thus if you want to manually initialize libgcrypt
you must do it before calling this function. This is useful in cases you
want to disable libgcrypt's internal lockings etc.
Arguments
Description
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*);
Arguments
Description
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.
Arguments
Description
This is the function were 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 (ie the gcrypt allocation functions).
This function must be called before gnutls_global_init() is called.
Arguments
Description
Returns the last handshake message received. 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.h for the available handshake descriptions.
Arguments
Description
Returns the last handshake message sent. 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.h for the available handshake descriptions.
Arguments
Description
This function will set the maximum size of a handshake message.
Handshake messages over this size are rejected.
The default value is 16kb which is large enough. Set this to 0 if you do not want
to set an upper limit.
Arguments
Description
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.
Unless this function is called with the option to allow (1), then
no compression algorithms, like LZO. That is because these algorithms
are not yet defined in any RFC or even internet draft.
Enabling the private ciphersuites when talking to other than gnutls
servers and clients may cause interoperability problems.
Arguments
Description
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 later be resumed.
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.
Arguments
Description
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 zero on success.
Arguments
Description
Returns a pointer to a string that contains the name
of the specified key exchange algorithm or NULL.
Arguments
Description
Returns the key exchange algorithm used in the last handshake.
Arguments
Description
Sets the priority on the key exchange algorithms supported by gnutls.
Priority is higher for algorithms 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.
Arguments
Description
Returns a string that contains the name
of the specified MAC algorithm or NULL.
Arguments
Description
Returns the currently used mac algorithm.
Arguments
Description
Sets the priority on the mac algorithms supported by gnutls.
Priority is higher for algorithms 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.
Arguments
Description
This function will allocate 's' bytes data, and
return a pointer to memory. This function is supposed
to be used by callbacks.
The allocation function used is the one set by gnutls_global_set_mem_functions().
Arguments
Description
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.
Arguments
Description
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.
Arguments
Description
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 GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough,
or 0 on success.
Arguments
Description
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.
Arguments
Description
This function will convert the given data to printable data, using the base64
encoding. This is the encoding used in PEM messages. If the provided
buffer is not long enough GNUTLS_E_SHORT_MEMORY_BUFFER is returned.
The output string will be null terminated, although the size will not include
the terminating null.
Arguments
Description
This function is like perror(). The only difference is that it accepts an
error number returned by a gnutls function.
Arguments
Description
Returns a string that contains the name
of the specified public key algorithm or NULL.
Arguments
Description
Returns a string that contains the name
of the specified TLS version or NULL.
Arguments
Description
Returns the version of the currently used protocol.
Arguments
Description
Sets the priority on the protocol versions supported by gnutls.
This function actually enables or disables protocols. Newer protocol
versions always have highest priority.
Arguments
Description
This function checks if there are any data to receive
in the gnutls buffers. Returns the size of that data or 0.
Notice that you may also use select() to check for data in
a TCP connection, instead of this function.
(gnutls leaves some data in the tcp buffer in order for select
to work).
Arguments
Description
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.
Arguments
Description
This function returns the maximum record packet size in this connection.
The maximum record size is negotiated by the client after the
first handshake message.
Arguments
Description
This function has the similar semantics to send(). The only
difference is that it accepts a GNUTLS session.
If the 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 containing NO_RENEGOTIATION,
or replied with a new handshake.
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.
A negative error code is returned in case of an error.
Arguments
Description
This function has the similar semantics with recv(). The only
difference is that is accepts a GNUTLS session, and uses different
error codes.
If the 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, with the
same parameters; cf. gnutls_record_get_direction(). Alternatively
you could provide a NULL pointer for data, and 0 for size.
Otherwise the write operation will be corrupted and the connection
will be terminated.
Returns the number of bytes sent, or a negative error code. The number
of bytes sent might be less than sizeofdata. The maximum number of bytes
this function can send in a single call depends on the negotiated
maximum record size.
Arguments
Description
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(=29), 1024(=210), 2048(=211) and 4096(=212).
Returns 0 on success. 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.
Arguments
Description
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.
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.
Arguments
Description
This function will return the bits used in the last RSA-EXPORT key exchange
with the peer.
Returns a negative value in case of an error.
Arguments
Description
This function will copy the RSA parameters structure from source
to destination.
Arguments
Description
This function will deinitialize the RSA parameters structure.
Arguments
Description
This function will export the given RSA parameters to a PKCS1
RSAPublicKey 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".
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
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.
Arguments
Description
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.
Arguments
Description
This function will extract the RSAPublicKey found in a PKCS1 formatted
structure.
If the structure is PEM encoded, it should have a header
of "BEGIN RSA PRIVATE KEY".
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
This function will replace the parameters in the given structure.
The new parameters should be stored in the appropriate gnutls_datum.
Arguments
Description
This function will initialize the temporary RSA parameters structure.
Arguments
Description
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.
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.
Arguments
Description
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 ind type. In case of GNUTLS_NAME_DNS,
an ASCII or UTF-8 null terminated string, without the trailing dot, is expected.
IPv4 or IPv6 addresses are not permitted.
Arguments
Description
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 succesful one.
Arguments
Description
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.
Arguments
Description
This function will return the user given pointer from the session structure.
This is the pointer set with gnutls_session_set_ptr().
Arguments
Description
This function will return non zero if this session is a resumed one,
or a zero if this is a new session.
Arguments
Description
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 a negative value on error.
Arguments
Description
This function will set (assosiate) the user given pointer to the session structure.
This is pointer can be accessed with gnutls_session_get_ptr().
Arguments
Description
Sets some default priority on the ciphers, key exchange methods, macs
and compression methods. This is to avoid using the gnutls_*_priority() functions, if
these defaults are ok. This function also includes weak algorithms.
The order is TLS1, SSL3 for protocols, RSA, DHE_DSS,
DHE_RSA, RSA_EXPORT for key exchange algorithms.
SHA, MD5, RIPEMD160 for MAC algorithms,
AES_256_CBC, AES_128_CBC,
and 3DES_CBC, ARCFOUR_128, ARCFOUR_40 for ciphers.
Arguments
Description
Sets some default priority on the ciphers, key exchange methods, macs
and compression methods. This is to avoid using the gnutls_*_priority() functions, if
these defaults are ok. You may override any of the following priorities by calling
the appropriate functions.
The order is TLS1, SSL3 for protocols.
RSA, DHE_DSS, DHE_RSA for key exchange
algorithms. SHA, MD5 and RIPEMD160 for MAC algorithms.
AES_256_CBC, AES_128_CBC, 3DES_CBC,
and ARCFOUR_128 for ciphers.
Arguments
Description
Returns a string that contains the name
of the specified sign algorithm or NULL.
Arguments
Description
This function is similar to strerror(). Differences: it accepts an error
number returned by a gnutls function; In case of an unknown error
a descriptive string is sent instead of NULL.
Arguments
Description
Used to get the arguments of the transport functions (like PUSH and
PULL). These should have been set using gnutls_transport_set_ptr2().
Arguments
Description
Used to get the first argument of the transport function (like PUSH and
PULL). This must have been set using gnutls_transport_set_ptr().
Arguments
Description
Used to set the lowat value in order for select to check
if there are pending data to socket buffer. Used only
if you have changed the default low water value (default is 1).
Normally you will not need that function.
This function is only useful if using berkeley style sockets.
Otherwise it must be called and set lowat to zero.
Arguments
Description
Used to set the first argument of the transport function (like PUSH and
PULL). In berkeley style sockets this function will set the connection
handle. With this function you can use two different pointers for
receiving and sending.
Arguments
Description
Used to set the first argument of the transport function (like PUSH and
PULL). In berkeley style sockets this function will set the connection
handle.
Arguments
Description
This is the function where you set a function for gnutls
to receive data. Normally, if you use berkeley style sockets,
you may not use this function since the default (recv(2)) will
probably be ok.
This function should be called once and after gnutls_global_init().
PULL_FUNC is of the form,
ssize_t (*gnutls_pull_func)(gnutls_transport_ptr, const void*, size_t);
Arguments
Description
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 may not 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.
This function should be called once and after gnutls_global_init().
PUSH_FUNC is of the form,
ssize_t (*gnutls_push_func)(gnutls_transport_ptr, const void*, size_t);
Arguments
Description
This function will decrypt the given encrypted bag and return 0 on success.
Arguments
Description
This function will deinitialize a PKCS12 Bag structure.
Arguments
Description
This function will encrypt the given bag and return 0 on success.
Arguments
Description
This function will return the number of the elements withing the bag.
Arguments
Description
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 0 on success and a negative error code on error.
Arguments
Description
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 0 on success, or a negative value on error.
Arguments
Description
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 0 on success, or a negative value on error.
Arguments
Description
This function will return the bag's type. One of the gnutls_pkcs12_bag_type
enumerations.
Arguments
Description
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 0 on success.
Arguments
Description
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
value on failure.
Arguments
Description
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.
Arguments
Description
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.
Arguments
Description
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 0 on success, or a negative value on error.
Arguments
Description
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 0 on success, or a negative value on error.
Arguments
Description
This function will deinitialize a PKCS12 structure.
Arguments
Description
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
GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
If the structure is PEM encoded, it will have a header
of "BEGIN PKCS12".
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
This function will generate a MAC for the PKCS12 structure.
Returns 0 on success.
Arguments
Description
This function will return a Bag from the PKCS12 structure.
Returns 0 on success.
After the last Bag has been read GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Arguments
Description
This function will convert the given DER or PEM encoded PKCS12
to the native gnutls_pkcs12 format. The output will be stored in 'pkcs12'.
If the PKCS12 is PEM encoded it should have a header of "PKCS12".
Returns 0 on success.
Arguments
Description
This function will initialize a PKCS12 structure. PKCS12 structures
usually contain lists of X.509 Certificates and X.509 Certificate
revocation lists.
Returns 0 on success.
Arguments
Description
This function will insert a Bag into the PKCS12 structure.
Returns 0 on success.
Arguments
Description
This function will verify the MAC for the PKCS12 structure.
Returns 0 on success.
Arguments
Description
This function will deinitialize a PKCS7 structure.
Arguments
Description
This function will delete a crl from a PKCS7 or RFC2630 crl set.
Index starts from 0. Returns 0 on success.
Arguments
Description
This function will delete a certificate from a PKCS7 or RFC2630 certificate set.
Index starts from 0. Returns 0 on success.
Arguments
Description
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
GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
If the structure is PEM encoded, it will have a header
of "BEGIN PKCS7".
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
This function will return the number of certifcates in the PKCS7 or
RFC2630 crl set.
Returns a negative value on failure.
Arguments
Description
This function will return a crl of the PKCS7 or RFC2630 crl set.
Returns 0 on success. If the provided buffer is not long enough,
then GNUTLS_E_SHORT_MEMORY_BUFFER is returned.
After the last crl has been read GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Arguments
Description
This function will return the number of certifcates in the PKCS7 or
RFC2630 certificate set.
Returns a negative value on failure.
Arguments
Description
This function will return a certificate of the PKCS7 or RFC2630 certificate set.
Returns 0 on success. If the provided buffer is not long enough,
then GNUTLS_E_SHORT_MEMORY_BUFFER is returned.
After the last certificate has been read GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
will be returned.
Arguments
Description
This function will convert the given DER or PEM encoded PKCS7
to the native gnutls_pkcs7 format. The output will be stored in 'pkcs7'.
If the PKCS7 is PEM encoded it should have a header of "PKCS7".
Returns 0 on success.
Arguments
Description
This function will initialize a PKCS7 structure. PKCS7 structures
usually contain lists of X.509 Certificates and X.509 Certificate
revocation lists.
Returns 0 on success.
Arguments
Description
This function will add a crl to the PKCS7 or RFC2630 crl set.
Returns 0 on success.
Arguments
Description
This function will add a parsed crl to the PKCS7 or RFC2630 crl set.
Returns 0 on success.
Arguments
Description
This function will add a certificate to the PKCS7 or RFC2630 certificate set.
Returns 0 on success.
Arguments
Description
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 0 on success.
Arguments
Description
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.
A negative value is returned in case of an error.
Arguments
Description
This function will deinitialize a CRL structure.
Arguments
Description
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 0 on success, and a negative value on failure.
Arguments
Description
This function will return the number of revoked certificates in the
given CRL.
Returns a negative value on failure.
Arguments
Description
This function will return the serial number of the specified, by the index,
revoked certificate.
Returns a negative value on failure.
Arguments
Description
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.
Arguments
Description
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 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 zero, 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().
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.
Arguments
Description
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 RFC2253. 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.
Arguments
Description
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 (time_t)-1 on error.
Arguments
Description
This function will return a value of the gnutls_sign_algorithm enumeration that
is the signature algorithm.
Returns a negative value on error.
Arguments
Description
This function will return the time this CRL was issued.
Returns (time_t)-1 on error.
Arguments
Description
This function will return the version of the specified CRL.
Returns a negative value on error.
Arguments
Description
This function will convert the given DER or PEM encoded CRL
to the native gnutls_x509_crl format. The output will be stored in 'crl'.
If the CRL is PEM encoded it should have a header of "X509 CRL".
Returns 0 on success.
Arguments
Description
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 0 on success.
Arguments
Description
This function will set a revoked certificate's serial number to the CRL.
Returns 0 on success, or a negative value in case of an error.
Arguments
Description
This function will set a revoked certificate's serial number to the CRL.
Returns 0 on success, or a negative value in case of an error.
Arguments
Description
This function will set the time this CRL will be updated.
Returns 0 on success, or a negative value in case of an error.
Arguments
Description
This function will set the time this CRL was issued.
Returns 0 on success, or a negative value in case of an error.
Arguments
Description
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 0 on success.
Arguments
Description
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 0 on success.
Arguments
Description
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.
Returns 0 on success and a negative value in case of an error.
Arguments
Description
This function will deinitialize a CRL structure.
Arguments
Description
This function will export the certificate request to a PKCS10
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 NEW CERTIFICATE REQUEST".
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
This function will return the challenge password in the
request.
Returns 0 on success.
Arguments
Description
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 zero, 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().
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.
On success 0 is returned.
Arguments
Description
This function will extract the requested OID of the name of the Certificate request subject, 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.
Arguments
Description
This function will copy the name of the Certificate request subject 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.
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.
On success 0 is returned.
Arguments
Description
This function will return the public key algorithm of a PKCS #10
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 enumeration on success,
or a negative value on error.
Arguments
Description
This function will return the version of the specified Certificate request.
Returns a negative value on error.
Arguments
Description
This function will convert the given DER or PEM encoded Certificate
to the native gnutls_x509_crq format. The output will be stored in cert.
If the Certificate is PEM encoded it should have a header of "NEW CERTIFICATE REQUEST".
Returns 0 on success.
Arguments
Description
This function will initialize a PKCS10 certificate request structure.
Returns 0 on success.
Arguments
Description
This function will set a challenge password to be used when revoking the request.
Returns 0 on success.
Arguments
Description
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 0 on success.
Arguments
Description
This function will set the public parameters from the given private key to the
request. Only RSA keys are currently supported.
Returns 0 on success.
Arguments
Description
This function will set the version of the certificate request. For
version 1 requests this must be one.
Returns 0 on success.
Arguments
Description
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 0 on success.
Arguments
Description
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 subject alternative name PKIX extension.
Returns non zero on success, and zero on failure.
Arguments
Description
This function will check if the given certificate was issued by the
given issuer. It will return true (1) if the given certificate is issued
by the given issuer, and false (0) if not.
A negative value is returned in case of an error.
Arguments
Description
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 value is returned on error.
Arguments
Description
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 0 on success.
Arguments
Description
This function will deinitialize a CRL structure.
Arguments
Description
This function will export the certificate 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 CERTIFICATE".
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
This function will return the time this Certificate was or will be activated.
Returns (time_t)-1 on error.
Arguments
Description
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.
Returns 0 on success and a negative value in case of an error.
Arguments
Description
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 zero if the certificate does not have
CA flag set.
A negative value 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.
Arguments
Description
This function will return the CRL distribution points (2.5.29.31), contained in the
given certificate.
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 zero for all possible reasons.
This is specified in X509v3 Certificate Extensions. GNUTLS will return the
distribution point type, or a negative error code on error.
Returns GNUTLS_E_SHORT_MEMORY_BUFFER 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.
If the certificate does not have an Alternative name with the specified
sequence number then returns GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE;
Arguments
Description
This function will extract the part of the name of the Certificate subject, specified
by the given OID. 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 zero, 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().
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.
On success 0 is returned.
Arguments
Description
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.
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.
Arguments
Description
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 RFC2253. 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.
On success 0 is returned.
Arguments
Description
This function will return the time this Certificate was or will be expired.
Returns (time_t)-1 on error.
Arguments
Description
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.
A negative value may be returned in case of parsing error.
If the certificate does not contain the specified extension
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned.
Arguments
Description
This function will return the requested extension OID in the certificate.
The extension OID will be stored as a string in the provided buffer.
A negative value may be returned in case of parsing error.
If your have reached the last extension available
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned.
Arguments
Description
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 sizeof_buf will be updated with the required size.
On success 0 is returned.
Arguments
Description
This function will extract the part of the name of the Certificate issuer 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 zero, 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().
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.
On success 0 is returned.
Arguments
Description
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.
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.
Arguments
Description
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 RFC2253. 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.
On success 0 is returned.
Arguments
Description
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
GNUTLS_E_SHORT_MEMORY_BUFFER will be returned. The output will normally
be a SHA-1 hash output, which is 20 bytes.
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
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.
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.
Arguments
Description
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.
A negative value may be returned in case of parsing error.
If the certificate does not contain the keyUsage extension
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned.
Arguments
Description
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 enumeration on success,
or a negative value on error.
Arguments
Description
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.
Arguments
Description
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.
Arguments
Description
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
opaque.
Returns 0 on success and a negative value in case of an error.
Arguments
Description
This function will return a value of the gnutls_sign_algorithm enumeration that
is the signature algorithm.
Returns a negative value on error.
Arguments
Description
This function will return the alternative names, contained in the
given certificate.
This is specified in X509v3 Certificate Extensions.
GNUTLS will return the Alternative name (2.5.29.17), or a negative
error code.
Returns GNUTLS_E_SHORT_MEMORY_BUFFER if ret_size is not enough to hold the alternative
name, or the type of alternative name if everything was ok. The type is
one of the enumerated gnutls_x509_subject_alt_name.
If the certificate does not have an Alternative name with the specified
sequence number then returns GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE;
Arguments
Description
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 0 on success and a negative value in case of an error.
Arguments
Description
This function will return the version of the specified Certificate.
Returns a negative value on error.
Arguments
Description
This function will convert the given DER or PEM encoded Certificate
to the native gnutls_x509_crt 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 0 on success.
Arguments
Description
This function will initialize an X.509 certificate structure.
Returns 0 on success.
Arguments
Description
This function will try to verify the given certificate list and return its status.
Note that expiration and activation dates are not checked
by this function, you should check them using the appropriate functions.
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 enumerated elements bitwise or'd.
For a more detailed verification status use gnutls_x509_crt_verify() per list
element.
GNUTLS_CERT_INVALID: the certificate chain is not valid.
GNUTLS_CERT_REVOKED: a certificate in the chain has been revoked.
Returns 0 on success and a negative value in case of an error.
Arguments
Description
This function will set the time this Certificate was or will be activated.
Returns 0 on success, or a negative value in case of an error.
Arguments
Description
This function will set the X.509 certificate's authority key ID extension.
Only the keyIdentifier field can be set with this function.
Returns 0 on success, or a negative value in case of an error.
Arguments
Description
This function will set the basicConstraints certificate extension.
Returns 0 on success.
Arguments
Description
This function will set the CRL distribution points certificate extension.
Returns 0 on success.
Arguments
Description
This function will set the name and public parameters from the given certificate request to the
certificate. Only RSA keys are currently supported.
Returns 0 on success.
Arguments
Description
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 0 on success.
Arguments
Description
This function will set the time this Certificate will expire.
Returns 0 on success, or a negative value in case of an error.
Arguments
Description
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 0 on success.
Arguments
Description
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.
On success 0 is returned.
Arguments
Description
This function will set the keyUsage certificate extension.
Returns 0 on success.
Arguments
Description
This function will set the public parameters from the given private key to the
certificate. Only RSA keys are currently supported.
Returns 0 on success.
Arguments
Description
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
opaque.
Returns 0 on success, or a negative value in case of an error.
Arguments
Description
This function will set the subject alternative name certificate extension.
Returns 0 on success.
Arguments
Description
This function will set the X.509 certificate's subject key ID extension.
Returns 0 on success, or a negative value in case of an error.
Arguments
Description
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.
Returns 0 on success.
Arguments
Description
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 0 on success.
Arguments
Description
This function will return the XML structures of the given X.509 certificate.
The XML structures are allocated internally (with malloc) and stored into res.
Returns a negative error code in case of an error.
Arguments
Description
This function will verify the given signed data, using the parameters from the
certificate.
In case of a verification failure 0 is returned, and
1 on success.
Arguments
Description
This function will try to verify the given certificate and return its status.
The verification output in this functions cannot be GNUTLS_CERT_NOT_VALID.
Returns 0 on success and a negative value in case of an error.
Arguments
Description
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.
Arguments
Description
This function will copy a private key from source to destination key.
Arguments
Description
This function will deinitialize a private key structure.
Arguments
Description
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.
Arguments
Description
This function will export the private key to a PKCS8 structure.
Currently only RSA keys can be exported. 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
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.
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
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.
Arguments
Description
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
GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
If the structure is PEM encoded, it will have a header
of "BEGIN RSA PRIVATE KEY".
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
This function will generate a random private key. Note that
this function must be called on an empty private key.
Returns 0 on success or a negative value on error.
Arguments
Description
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
GNUTLS_E_SHORT_MEMORY_BUFFER will be returned. The output will normally
be a SHA-1 hash output, which is 20 bytes.
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
This function will return the public key algorithm of a private
key.
Returns a member of the gnutls_pk_algorithm enumeration on success,
or a negative value on error.
Arguments
Description
This function will convert the given DSA raw parameters
to the native gnutls_x509_privkey format. The output will be stored in key.
Arguments
Description
This function will convert the given DER or PEM encoded PKCS8 2.0 encrypted key
to the native gnutls_x509_privkey format. The output will be stored in key.
Currently only RSA 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.
Returns 0 on success.
Arguments
Description
This function will convert the given RSA raw parameters
to the native gnutls_x509_privkey format. The output will be stored in key.
Arguments
Description
This function will convert the given DER or PEM encoded key
to the native gnutls_x509_privkey format. The output will be stored in key .
If the key is PEM encoded it should have a header of "RSA PRIVATE KEY", or
"DSA PRIVATE KEY".
Returns 0 on success.
Arguments
Description
This function will initialize an private key structure.
Returns 0 on success.
Arguments
Description
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
GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.
In case of failure a negative value will be returned, and
0 on success.
Arguments
Description
This function will verify the given signed data, using the parameters in the
private key.
In case of a verification failure 0 is returned, and
1 on success.
Arguments
Description
This function will return the name of the given Object identifier,
of the RDN sequence.
The name will be encoded using the rules from RFC2253.
Returns GNUTLS_E_SHORT_MEMORY_BUFFER if the provided buffer is not long enough,
and 0 on success.
Arguments
Description
This function will return the specified Object identifier,
of the RDN sequence.
Returns GNUTLS_E_SHORT_MEMORY_BUFFER if the provided buffer is not long enough,
and 0 on success.
Arguments
Description
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 RFC2253.
Returns GNUTLS_E_SHORT_MEMORY_BUFFER if the provided buffer is not long enough,
and 0 on success.
Arguments
Description
This function initializes the global state of gnutls-extra library to defaults.
Returns zero on success.
Note that gnutls_global_init() has to be called before this function.
If this function is not called then the gnutls-extra library will not
be usable.
Arguments
Description
This structure is complex enough to manipulate directly thus
this helper function is provided in order to allocate it.
Returns 0 on success.
Arguments
Description
This structure is complex enough to manipulate directly thus
this helper function is provided in order to allocate it.
Returns 0 on success.
Arguments
Description
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 found in libsrp.
You should use gnutls_free() to free the returned data.
Arguments
Description
This function will decode the given encoded data, using the base64 encoding
found in libsrp.
Note that b64_data should be null terminated.
Returns GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough,
or 0 on success.
Arguments
Description
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.
Arguments
Description
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.
Arguments
Description
This structure is complex enough to manipulate directly thus
this helper function is provided in order to free (deallocate) it.
Arguments
Description
This structure is complex enough to manipulate directly thus
this helper function is provided in order to free (deallocate) it.
Arguments
Description
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.
Arguments
Description
This function sets a callback to assist in selecting the proper password file,
in case there are more than one. The callback's function form is:
int (*callback)(gnutls_session, const char** pfiles, const char** pconffiles, int npfiles);
pfiles contains npfiles char* structures which hold
the password file name. pconffiles contain the corresponding
conf files.
This function specifies what we, in case of a server, are going
to do when we have to use a password file. If this callback
function is not provided then gnutls will automatically select the
first password file
In case the callback returned a negative number then gnutls will
terminate this handshake.
The callback function will only be called once per handshake.
The callback function should return the index of the password file
that will be used by the server. -1 indicates an error.
Arguments
Description
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, unsigned int times, char** username,
char** password);
The username and password must be allocated using gnutls_malloc().
times will be 0 the first time called, and 1 the second.
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 or twice per handshake.
The first time called, is before the ciphersuite is negotiated.
At that time if the callback returns a negative error code,
the callback will be called again if SRP has been
negotiated. This uses a special TLS-SRP idiom in order to avoid
asking the user for SRP password and username if the server does
not support SRP.
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.
Arguments
Description
This function sets the username and password, in a gnutls_srp_client_credentials 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 0 on success.
Arguments
Description
This function sets the password files, in a gnutls_srp_server_credentials structure.
Those password files hold usernames and verifiers and will be used for SRP authentication.
Returns 0 on success.
Arguments
Description
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, const char* username,
gnutls_datum* salt, gnutls_datum *verifier, gnutls_datum* g,
gnutls_datum* 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 extra.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.
Arguments
Description
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/extra.h or may be generated using the GCRYPT functions
gcry_prime_generate() and gcry_prime_group_generator().
The verifier will be allocated with malloc and will be stored in res using
binary format.
Arguments
Description
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 non zero on success, and zero on failure.
Arguments
Description
This function will deinitialize a key structure.
Arguments
Description
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 0 on success.
Arguments
Description
Returns the timestamp when the OpenPGP key was created.
Arguments
Description
Returns the time when the OpenPGP key expires. A value of '0' means
that the key doesn't expire at all.
Arguments
Description
Returns the fingerprint of the OpenPGP key. Depends on the algorithm,
the fingerprint can be 16 or 20 bytes.
Arguments
Description
Returns the 64-bit keyID of the OpenPGP key.
Arguments
Description
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.
A negative value may be returned in case of parsing error.
Arguments
Description
Extracts the userID from the parsed OpenPGP key.
Returns 0 on success, and GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE
if the index of the ID does not exist.
Arguments
Description
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_PKAlgorithm enumeration on success,
or a negative value on error.
Arguments
Description
Extract the version of the OpenPGP key.
Arguments
Description
This function will convert the given RAW or Base64 encoded key
to the native gnutls_openpgp_key format. The output will be stored in 'key'.
Returns 0 on success.
Arguments
Description
This function will initialize an OpenPGP key structure.
Returns 0 on success.
Arguments
Description
This function will return the all OpenPGP key information encapsulated as
a XML string.
Arguments
Description
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 enumerated elements bitwise or'd.
GNUTLS_CERT_INVALID: A signature on the key is invalid.
GNUTLS_CERT_REVOKED: The key has been revoked.
NOTE
this function does not verify using any "web of trust". You
may use GnuPG for that purpose, or any other external PGP application.
Returns 0 on success.
Arguments
Description
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 enumerated elements bitwise or'd.
GNUTLS_CERT_INVALID: The self signature on the key is invalid.
Returns 0 on success.
Arguments
Description
Checks if the key is revoked or disabled, in the trustdb.
The verification output will be put in verify and will be
one or more of the gnutls_certificate_status enumerated elements bitwise or'd.
GNUTLS_CERT_INVALID: A signature on the key is invalid.
GNUTLS_CERT_REVOKED: The key has been revoked.
NOTE
this function does not verify using any "web of trust". You
may use GnuPG for that purpose, or any other external PGP application.
Returns 0 on success.
Arguments
Description
Check if a given key ID exists in the keyring.
Returns 0 on success (if keyid exists) and a negative error code
on failure.
Arguments
Description
This function will deinitialize a CRL structure.
Arguments
Description
This function will convert the given RAW or Base64 encoded keyring
to the native gnutls_openpgp_keyring format. The output will be stored in 'keyring'.
Returns 0 on success.
Arguments
Description
This function will initialize an OpenPGP keyring structure.
Returns 0 on success.
Arguments
Description
This function will deinitialize a key structure.
Arguments
Description
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_PKAlgorithm enumeration on success,
or a negative value on error.
Arguments
Description
This function will convert the given RAW or Base64 encoded key
to the native gnutls_openpgp_privkey format. The output will be stored in 'key'.
Returns 0 on success.
Arguments
Description
This function will initialize an OpenPGP key structure.
Returns 0 on success.
Arguments
Description
This function will deinitialize a CRL structure.
Arguments
Description
This function will convert the given RAW or Base64 encoded trustdb
to the native gnutls_openpgp_trustdb format. The output will be stored in 'trustdb'.
Returns 0 on success.
Arguments
Description
This function will initialize an OpenPGP trustdb structure.
Returns 0 on success.
This appendix contains some example output of the XML convertion functions:
<?xml version="1.0" encoding="UTF-8"?>
<gnutls:x509:certificate version="1.1">
<certificate type="SEQUENCE">
<tbsCertificate type="SEQUENCE">
<version type="INTEGER" encoding="HEX">02</version>
<serialNumber type="INTEGER" encoding="HEX">01</serialNumber>
<signature type="SEQUENCE">
<algorithm type="OBJECT ID">1.2.840.113549.1.1.4</algorithm>
<parameters type="ANY">
<md5WithRSAEncryption encoding="HEX">0500</md5WithRSAEncryption>
</parameters>
</signature>
<issuer type="CHOICE">
<rdnSequence type="SEQUENCE OF">
<unnamed1 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.6</type>
<value type="ANY">
<X520countryName>GR</X520countryName>
</value>
</unnamed1>
</unnamed1>
<unnamed2 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.8</type>
<value type="ANY">
<X520StateOrProvinceName>Attiki</X520StateOrProvinceName>
</value>
</unnamed1>
</unnamed2>
<unnamed3 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.7</type>
<value type="ANY">
<X520LocalityName>Athina</X520LocalityName>
</value>
</unnamed1>
</unnamed3>
<unnamed4 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.10</type>
<value type="ANY">
<X520OrganizationName>GNUTLS</X520OrganizationName>
</value>
</unnamed1>
</unnamed4>
<unnamed5 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.11</type>
<value type="ANY">
<X520OrganizationalUnitName>GNUTLS dev.</X520OrganizationalUnitName>
</value>
</unnamed1>
</unnamed5>
<unnamed6 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.3</type>
<value type="ANY">
<X520CommonName>GNUTLS TEST CA</X520CommonName>
</value>
</unnamed1>
</unnamed6>
<unnamed7 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">1.2.840.113549.1.9.1</type>
<value type="ANY">
<Pkcs9email>gnutls-dev@gnupg.org</Pkcs9email>
</value>
</unnamed1>
</unnamed7>
</rdnSequence>
</issuer>
<validity type="SEQUENCE">
<notBefore type="CHOICE">
<utcTime type="TIME">010707101845Z</utcTime>
</notBefore>
<notAfter type="CHOICE">
<utcTime type="TIME">020707101845Z</utcTime>
</notAfter>
</validity>
<subject type="CHOICE">
<rdnSequence type="SEQUENCE OF">
<unnamed1 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.6</type>
<value type="ANY">
<X520countryName>GR</X520countryName>
</value>
</unnamed1>
</unnamed1>
<unnamed2 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.8</type>
<value type="ANY">
<X520StateOrProvinceName>Attiki</X520StateOrProvinceName>
</value>
</unnamed1>
</unnamed2>
<unnamed3 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.7</type>
<value type="ANY">
<X520LocalityName>Athina</X520LocalityName>
</value>
</unnamed1>
</unnamed3>
<unnamed4 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.10</type>
<value type="ANY">
<X520OrganizationName>GNUTLS</X520OrganizationName>
</value>
</unnamed1>
</unnamed4>
<unnamed5 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.11</type>
<value type="ANY">
<X520OrganizationalUnitName>GNUTLS dev.</X520OrganizationalUnitName>
</value>
</unnamed1>
</unnamed5>
<unnamed6 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">2.5.4.3</type>
<value type="ANY">
<X520CommonName>localhost</X520CommonName>
</value>
</unnamed1>
</unnamed6>
<unnamed7 type="SET OF">
<unnamed1 type="SEQUENCE">
<type type="OBJECT ID">1.2.840.113549.1.9.1</type>
<value type="ANY">
<Pkcs9email>root@localhost</Pkcs9email>
</value>
</unnamed1>
</unnamed7>
</rdnSequence>
</subject>
<subjectPublicKeyInfo type="SEQUENCE">
<algorithm type="SEQUENCE">
<algorithm type="OBJECT ID">1.2.840.113549.1.1.1</algorithm>
<parameters type="ANY">
<rsaEncryption encoding="HEX">0500</rsaEncryption>
</parameters>
</algorithm>
<subjectPublicKey type="BIT STRING" encoding="HEX" length="1120">30818902818100D00B49EBB226D951F5CC57072199DDF287683D2DA1A0EFCC96BFF73164777C78C3991E92EDA66584E7B97BAB4BE68D595D225557E01E7E57B5C35C04B491948C5C427AD588D8C6989764996D6D44E17B65CCFC86F3B4842DE559B730C1DE3AEF1CE1A328AFF8A357EBA911E1F7E8FC1598E21E4BF721748C587F50CF46157D950203010001</subjectPublicKey>
</subjectPublicKeyInfo>
<extensions type="SEQUENCE OF">
<unnamed1 type="SEQUENCE">
<extnID type="OBJECT ID">2.5.29.35</extnID>
<critical type="BOOLEAN">FALSE</critical>
<extnValue type="SEQUENCE">
<keyIdentifier type="OCTET STRING" encoding="HEX">EFEE94ABC8CA577F5313DB76DC1A950093BAF3C9</keyIdentifier>
</extnValue>
</unnamed1>
<unnamed2 type="SEQUENCE">
<extnID type="OBJECT ID">2.5.29.37</extnID>
<critical type="BOOLEAN">FALSE</critical>
<extnValue type="SEQUENCE OF">
<unnamed1 type="OBJECT ID">1.3.6.1.5.5.7.3.1</unnamed1>
<unnamed2 type="OBJECT ID">1.3.6.1.5.5.7.3.2</unnamed2>
<unnamed3 type="OBJECT ID">1.3.6.1.4.1.311.10.3.3</unnamed3>
<unnamed4 type="OBJECT ID">2.16.840.1.113730.4.1</unnamed4>
</extnValue>
</unnamed2>
<unnamed3 type="SEQUENCE">
<extnID type="OBJECT ID">2.5.29.19</extnID>
<critical type="BOOLEAN">TRUE</critical>
<extnValue type="SEQUENCE">
<cA type="BOOLEAN">FALSE</cA>
</extnValue>
</unnamed3>
</extensions>
</tbsCertificate>
<signatureAlgorithm type="SEQUENCE">
<algorithm type="OBJECT ID">1.2.840.113549.1.1.4</algorithm>
<parameters type="ANY">
<md5WithRSAEncryption encoding="HEX">0500</md5WithRSAEncryption>
</parameters>
</signatureAlgorithm>
<signature type="BIT STRING" encoding="HEX" length="1024">B73945273AF2A395EC54BF5DC669D953885A9D811A3B92909D24792D36A44EC27E1C463AF8738BEFD29B311CCE8C6D9661BEC30911DAABB39B8813382B32D2E259581EBCD26C495C083984763966FF35D1DEFE432891E610C85072578DA7423244A8F5997B41A1F44E61F4F22C94375775055A5E72F25D5E4557467A91BD4251</signature>
</certificate>
</gnutls:x509:certificate>
<?xml version="1.0"?>
<gnutls:openpgp:key version="1.0">
<OPENPGPKEY>
<MAINKEY>
<KEYID>BD572CDCCCC07C3</KEYID>
<FINGERPRINT>BE615E88D6CFF27225B8A2E7BD572CDCCCC07C35</FINGERPRINT>
<PKALGO>DSA</PKALGO>
<KEYLEN>1024</KEYLEN>
<CREATED>1011533164</CREATED>
<REVOKED>0</REVOKED>
<KEY ENCODING="HEX"/>
<DSA-P>0400E72E76B62EEFA9A3BD594093292418050C02D7029D6CA2066EFC34C86038627C643EB1A652A7AF1D37CF46FC505AC1E0C699B37895B4BCB3E53541FFDA4766D6168C2B8AAFD6AB22466D06D18034D5DAC698E6993BA5B350FF822E1CD8702A75114E8B73A6B09CB3B93CE44DBB516C9BB5F95BB666188602A0A1447236C0658F</DSA-P>
<DSA-Q>00A08F5B5E78D85F792CC2072F9474645726FB4D9373</DSA-Q>
<DSA-G>03FE3578D689D6606E9118E9F9A7042B963CF23F3D8F1377A273C0F0974DBF44B3CABCBE14DD64412555863E39A9C627662D77AC36662AE449792C3262D3F12E9832A7565309D67BA0AE4DF25F5EDA0937056AD5BE89F4069EBD7EC76CE432441DF5D52FFFD06D39E5F61E36947B698A77CB62AB81E4A4122BF9050671D9946C865E</DSA-G>
<DSA-Y>0400D061437A964DDE318818C2B24DE008E60096B60DB8A684B85A838D119FC930311889AD57A3B927F448F84EB253C623EDA73B42FF78BCE63A6A531D75A64CE8540513808E9F5B10CE075D3417B801164918B131D3544C8765A8ECB9971F61A09FC73D509806106B5977D211CB0E1D04D0ED96BCE89BAE8F73D800B052139CBF8D</DSA-Y>
</MAINKEY>
<USERID>
<NAME>OpenCDK test key (Only intended for test purposes!)</NAME>
<EMAIL>opencdk@foo-bar.org</EMAIL>
<PRIMARY>0</PRIMARY>
<REVOKED>0</REVOKED>
</USERID>
<SIGNATURE>
<VERSION>4</VERSION>
<SIGCLASS>19</SIGCLASS>
<EXPIRED>0</EXPIRED>
<PKALGO>DSA</PKALGO>
<MDALGO>SHA1</MDALGO>
<CREATED>1011533164</CREATED>
<KEYID>BD572CDCCCC07C3</KEYID>
</SIGNATURE>
<SUBKEY>
<KEYID>FCB0CF3A5261E06</KEYID>
<FINGERPRINT>297B48ACC09C0FF683CA1ED1FCB0CF3A5261E067</FINGERPRINT>
<PKALGO>ELG</PKALGO>
<KEYLEN>1024</KEYLEN>
<CREATED>1011533167</CREATED>
<REVOKED>0</REVOKED>
<KEY ENCODING="HEX"/>
<ELG-P>0400E20156526069D067D24F4D71E6D38658E08BE3BF246C1ADCE08DB69CD8D459C1ED335738410798755AFDB79F1797CF022E70C7960F12CA6896D27CFD24A11CD316DDE1FBCC1EA615C5C31FEC656E467078C875FC509B1ECB99C8B56C2D875C50E2018B5B0FA378606EB6425A2533830F55FD21D649015615D49A1D09E9510F5F</ELG-P>
<ELG-G>000305</ELG-G>
<ELG-Y>0400D0BDADE40432758675C87D0730C360981467BAE1BEB6CC105A3C1F366BFDBEA12E378456513238B8AD414E52A2A9661D1DF1DB6BB5F33F6906166107556C813224330B30932DB7C8CC8225672D7AE24AF2469750E539B661EA6475D2E03CD8D3838DC4A8AC4AFD213536FE3E96EC9D0AEA65164B576E01B37A8DCA89F2B257D0</ELG-Y>
</SUBKEY>
<SIGNATURE>
<VERSION>4</VERSION>
<SIGCLASS>24</SIGCLASS>
<EXPIRED>0</EXPIRED>
<PKALGO>DSA</PKALGO>
<MDALGO>SHA1</MDALGO>
<CREATED>1011533167</CREATED>
<KEYID>BD572CDCCCC07C3</KEYID>
</SIGNATURE>
</OPENPGPKEY>
</gnutls:openpgp:key>
| Error code | Description |
|---|---|
| GNUTLS_E_AGAIN | Function was interrupted. |
| GNUTLS_E_ASN1_DER_ERROR | ASN1 parser: Error in DER parsing. |
| GNUTLS_E_ASN1_DER_OVERFLOW | ASN1 parser: Overflow in DER parsing. |
| GNUTLS_E_ASN1_ELEMENT_NOT_FOUND | ASN1 parser: Element was not found. |
| GNUTLS_E_ASN1_GENERIC_ERROR | ASN1 parser: Generic parsing error. |
| GNUTLS_E_ASN1_IDENTIFIER_NOT_FOUND | ASN1 parser: Identifier was not found |
| GNUTLS_E_ASN1_SYNTAX_ERROR | ASN1 parser: Syntax error. |
| GNUTLS_E_ASN1_TAG_ERROR | ASN1 parser: Error in TAG. |
| GNUTLS_E_ASN1_TAG_IMPLICIT | ASN1 parser: error in implicit tag |
| GNUTLS_E_ASN1_TYPE_ANY_ERROR | ASN1 parser: Error in type 'ANY'. |
| GNUTLS_E_ASN1_VALUE_NOT_FOUND | ASN1 parser: Value was not found. |
| GNUTLS_E_ASN1_VALUE_NOT_VALID | ASN1 parser: Value is not valid. |
| GNUTLS_E_BASE64_DECODING_ERROR | Base64 decoding error. |
| GNUTLS_E_BASE64_ENCODING_ERROR | Base64 encoding error. |
| GNUTLS_E_CERTIFICATE_ERROR | Error in the certificate. |
| GNUTLS_E_CERTIFICATE_KEY_MISMATCH | The certificate and the given key do not match. |
| GNUTLS_E_COMPRESSION_FAILED | Compression of the TLS record packet has failed. |
| GNUTLS_E_CONSTRAINT_ERROR | Some constraint limits were reached. |
| GNUTLS_E_DB_ERROR | Error in Database backend. |
| GNUTLS_E_DECOMPRESSION_FAILED | Decompression of the TLS record packet has failed. |
| GNUTLS_E_DECRYPTION_FAILED | Decryption has failed. |
| GNUTLS_E_DH_PRIME_UNACCEPTABLE | The Diffie Hellman prime sent by the server is not acceptable (not long enough). |
| GNUTLS_E_ENCRYPTION_FAILED | Encryption has failed. |
| GNUTLS_E_ERROR_IN_FINISHED_PACKET | An error was encountered at the TLS Finished packet calculation. |
| GNUTLS_E_EXPIRED | The requested session has expired. |
| GNUTLS_E_FATAL_ALERT_RECEIVED | A TLS fatal alert has been received. |
| GNUTLS_E_FILE_ERROR | Error while reading file. |
| GNUTLS_E_GOT_APPLICATION_DATA | TLS Application data were received, while expecting handshake data. |
| GNUTLS_E_HASH_FAILED | Hashing has failed. |
| GNUTLS_E_ILLEGAL_SRP_USERNAME | The SRP username supplied is illegal. |
| GNUTLS_E_INCOMPATIBLE_GCRYPT_LIBRARY | The gcrypt library version is too old. |
| GNUTLS_E_INCOMPATIBLE_LIBTASN1_LIBRARY | The tasn1 library version is too old. |
| GNUTLS_E_INIT_LIBEXTRA | The initialization of GnuTLS-extra has failed. |
| GNUTLS_E_INSUFFICIENT_CREDENTIALS | Insufficient credentials for that request. |
| GNUTLS_E_INTERNAL_ERROR | GnuTLS internal error. |
| GNUTLS_E_INTERRUPTED | Function was interrupted. |
| GNUTLS_E_INVALID_PASSWORD | The given password contains invalid characters. |
| GNUTLS_E_INVALID_REQUEST | The request is invalid. |
| GNUTLS_E_INVALID_SESSION | The specified session has been invalidated for some reason. |
| GNUTLS_E_KEY_USAGE_VIOLATION | Key usage violation in certificate has been detected. |
| GNUTLS_E_LARGE_PACKET | A large TLS record packet was received. |
| GNUTLS_E_LIBRARY_VERSION_MISMATCH | The GnuTLS library version does not match the GnuTLS-extra library version. |
| GNUTLS_E_LZO_INIT_FAILED | The initialization of LZO has failed. |
| GNUTLS_E_MAC_VERIFY_FAILED | The Message Authentication Code verification failed. |
| GNUTLS_E_MEMORY_ERROR | Internal error in memory allocation. |
| GNUTLS_E_MPI_PRINT_FAILED | Could not export a large integer. |
| GNUTLS_E_MPI_SCAN_FAILED | The scanning of a large integer has failed. |
| GNUTLS_E_NO_CERTIFICATE_FOUND | The peer did not send any certificate. |
| GNUTLS_E_NO_CIPHER_SUITES | No supported cipher suites have been found. |
| GNUTLS_E_NO_COMPRESSION_ALGORITHMS | No supported compression algorithms have been found. |
| GNUTLS_E_NO_TEMPORARY_DH_PARAMS | No temporary DH parameters were found. |
| GNUTLS_E_NO_TEMPORARY_RSA_PARAMS | No temporary RSA parameters were found. |
| GNUTLS_E_OPENPGP_FINGERPRINT_UNSUPPORTED | The OpenPGP fingerprint is not supported. |
| GNUTLS_E_OPENPGP_GETKEY_FAILED | Could not get OpenPGP key. |
| GNUTLS_E_OPENPGP_KEYRING_ERROR | Error loading the keyring. |
| GNUTLS_E_OPENPGP_TRUSTDB_VERSION_UNSUPPORTED | The specified GnuPG TrustDB version is not supported. TrustDB v4 is supported. |
| GNUTLS_E_PKCS1_WRONG_PAD | Wrong padding in PKCS1 packet. |
| GNUTLS_E_PK_DECRYPTION_FAILED | Public key decryption has failed. |
| GNUTLS_E_PK_ENCRYPTION_FAILED | Public key encryption has failed. |
| GNUTLS_E_PK_SIGN_FAILED | Public key signing has failed. |
| GNUTLS_E_PK_SIG_VERIFY_FAILED | Public key signature verification has failed. |
| GNUTLS_E_PULL_ERROR | Error in the pull function. |
| GNUTLS_E_PUSH_ERROR | Error in the push function. |
| GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION | An illegal TLS extension was received. |
| GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER | An illegal parameter has been received. |
| GNUTLS_E_RECORD_LIMIT_REACHED | The upper limit of record packet sequence numbers has been reached. Wow! |
| GNUTLS_E_REHANDSHAKE | Rehandshake was requested by the peer. |
| GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE | The requested data were not available. |
| GNUTLS_E_SHORT_MEMORY_BUFFER | The given memory buffer is too short to hold parameters. |
| GNUTLS_E_SRP_PWD_ERROR | Error in SRP password file. |
| GNUTLS_E_SRP_PWD_PARSING_ERROR | Parsing error in SRP password file. |
| GNUTLS_E_SUCCESS | Success. |
| GNUTLS_E_TOO_MANY_EMPTY_PACKETS | Too many empty record packets have been received. |
| GNUTLS_E_UNEXPECTED_HANDSHAKE_PACKET | An unexpected TLS handshake packet was received. |
| GNUTLS_E_UNEXPECTED_PACKET | An unexpected TLS packet was received. |
| GNUTLS_E_UNEXPECTED_PACKET_LENGTH | A TLS packet with unexpected length was received. |
| GNUTLS_E_UNKNOWN_CIPHER_SUITE | Could not negotiate a supported cipher suite. |
| GNUTLS_E_UNKNOWN_CIPHER_TYPE | The cipher type is unsupported. |
| GNUTLS_E_UNKNOWN_COMPRESSION_ALGORITHM | Could not negotiate a supported compression method. |
| GNUTLS_E_UNKNOWN_HASH_ALGORITHM | The hash algorithm is unknown. |
| GNUTLS_E_UNKNOWN_PKCS_BAG_TYPE | The PKCS structure's bag type is unknown. |
| GNUTLS_E_UNKNOWN_PKCS_CONTENT_TYPE | The PKCS structure's content type is unknown. |
| GNUTLS_E_UNKNOWN_PK_ALGORITHM | An unknown public key algorithm was encountered. |
| GNUTLS_E_UNSUPPORTED_CERTIFICATE_TYPE | The certificate type is not supported. |
| GNUTLS_E_UNSUPPORTED_VERSION_PACKET | A record packet with illegal version was received. |
| GNUTLS_E_UNWANTED_ALGORITHM | An algorithm that is not enabled was negotiated. |
| GNUTLS_E_WARNING_ALERT_RECEIVED | A TLS warning alert has been received. |
| GNUTLS_E_X509_UNKNOWN_SAN | Unknown Subject Alternative name in X.509 certificate. |
| GNUTLS_E_X509_UNSUPPORTED_ATTRIBUTE | The certificate has unsupported attributes. |
| GNUTLS_E_X509_UNSUPPORTED_CRITICAL_EXTENSION | Unsupported critical extension in X.509 certificate. |
| GNUTLS_E_X509_UNSUPPORTED_OID | The OID is not supported. |
| Cipher suite | TLS value | defined at |
|---|---|---|
| TLS_RSA_NULL_MD5 | 0x00 0x01 | RFC2246 |
| TLS_ANON_DH_3DES_EDE_CBC_SHA | 0x00 0x1B | RFC2246 |
| TLS_ANON_DH_ARCFOUR_MD5 | 0x00 0x18 | RFC2246 |
| TLS_ANON_DH_AES_128_CBC_SHA | 0x00 0x34 | RFC2246 |
| TLS_ANON_DH_AES_256_CBC_SHA | 0x00 0x3A | RFC2246 |
| TLS_RSA_ARCFOUR_SHA | 0x00 0x05 | RFC2246 |
| TLS_RSA_ARCFOUR_MD5 | 0x00 0x04 | RFC2246 |
| TLS_RSA_3DES_EDE_CBC_SHA | 0x00 0x0A | RFC2246 |
| TLS_RSA_EXPORT_ARCFOUR_40_MD5 | 0x00 0x03 | RFC2246 |
| TLS_DHE_DSS_3DES_EDE_CBC_SHA | 0x00 0x13 | RFC2246 |
| TLS_DHE_RSA_3DES_EDE_CBC_SHA | 0x00 0x16 | RFC2246 |
| TLS_RSA_AES_128_CBC_SHA | 0x00 0x2F | RFC3268 |
| TLS_RSA_AES_128_CBC_SHA | 0x00 0x35 | RFC3268 |
| TLS_DHE_DSS_AES_256_CBC_SHA | 0x00 0x38 | RFC3268 |
| TLS_DHE_DSS_AES_128_CBC_SHA | 0x00 0x32 | RFC3268 |
| TLS_DHE_RSA_AES_256_CBC_SHA | 0x00 0x39 | RFC3268 |
| TLS_DHE_RSA_AES_128_CBC_SHA | 0x00 0x33 | RFC3268 |
| TLS_SRP_SHA_3DES_EDE_CBC_SHA | 0x00 0x50 | draft-ietf-tls-srp |
| TLS_SRP_SHA_AES_128_CBC_SHA | 0x00 0x53 | draft-ietf-tls-srp |
| TLS_SRP_SHA_AES_256_CBC_SHA | 0x00 0x56 | draft-ietf-tls-srp |
| TLS_SRP_SHA_RSA_3DES_EDE_CBC_SHA | 0x00 0x51 | draft-ietf-tls-srp |
| TLS_SRP_SHA_DSS_3DES_EDE_CBC_SHA | 0x00 0x52 | draft-ietf-tls-srp |
| TLS_SRP_SHA_RSA_AES_128_CBC_SHA | 0x00 0x54 | draft-ietf-tls-srp |
| TLS_SRP_SHA_DSS_AES_128_CBC_SHA | 0x00 0x55 | draft-ietf-tls-srp |
| TLS_SRP_SHA_RSA_AES_256_CBC_SHA | 0x00 0x57 | draft-ietf-tls-srp |
| TLS_SRP_SHA_DSS_AES_256_CBC_SHA | 0x00 0x58 | draft-ietf-tls-srp |
| TLS_DHE_DSS_3DES_EDE_CBC_RMD | 0x00 0x72 | draft-ietf-tls-openpgp-keys |
| TLS_DHE_RSA_3DES_EDE_CBC_RMD | 0x00 0x77 | draft-ietf-tls-openpgp-keys |
| TLS_DHE_DSS_AES_256_CBC_RMD | 0x00 0x73 | draft-ietf-tls-openpgp-keys |
| TLS_DHE_DSS_AES_128_CBC_RMD | 0x00 0x74 | draft-ietf-tls-openpgp-keys |
| TLS_DHE_RSA_AES_128_CBC_RMD | 0x00 0x78 | draft-ietf-tls-openpgp-keys |
| TLS_DHE_RSA_AES_256_CBC_RMD | 0x00 0x79 | draft-ietf-tls-openpgp-keys |
| TLS_RSA_3DES_EDE_CBC_RMD | 0x00 0x7C | draft-ietf-tls-openpgp-keys |
| TLS_RSA_AES_128_CBC_RMD | 0x00 0x7D | draft-ietf-tls-openpgp-keys |
| TLS_RSA_AES_256_CBC_RMD | 0x00 0x7E | draft-ietf-tls-openpgp-keys |
| TLS_DHE_DSS_ARCFOUR_SHA | 0x00 0x66 | draft-ietf-tls-56-bit-ciphersuites |
The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.
We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.
This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.
A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.
A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.
The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.
The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.
A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.
The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.
A section "Entitled XYZ" means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as "Acknowledgements", "Dedications", "Endorsements", or "History".) To "Preserve the Title" of such a section when you modify the Document means that it remains a section "Entitled XYZ" according to this definition.
The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.
You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and you may publicly display copies.
If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.
If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.
You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:
If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.
You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties-for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.
You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled "History" in the various original documents, forming one section Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections Entitled "Endorsements".
You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.
A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.
Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.
If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.
You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.
To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:
Copyright ©YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 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".
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.
for
a more detailed description of the protocols.
for information on initialization
.