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<title>GnuTLS 3.4.8: TLS Authentication Methods</title>
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<a name="TLS-Authentication-Methods"></a>
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<p>
Next: <a href="TLS-Extension-Handling.html#TLS-Extension-Handling" accesskey="n" rel="next">TLS Extension Handling</a>, Previous: <a href="TLS-Handshake-Protocol.html#TLS-Handshake-Protocol" accesskey="p" rel="prev">TLS Handshake Protocol</a>, Up: <a href="Internal-architecture-of-GnuTLS.html#Internal-architecture-of-GnuTLS" accesskey="u" rel="up">Internal architecture of GnuTLS</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="TLS-Authentication-Methods-1"></a>
<h3 class="section">10.3 TLS Authentication Methods</h3>
<p>In <acronym>GnuTLS</acronym> authentication methods can be implemented quite
easily. Since the required changes to add a new authentication method
affect only the handshake protocol, a simple interface is used. An
authentication method needs to implement the functions shown below.
</p>
<pre class="verbatim">typedef struct
{
const char *name;
int (*gnutls_generate_server_certificate) (gnutls_session_t, gnutls_buffer_st*);
int (*gnutls_generate_client_certificate) (gnutls_session_t, gnutls_buffer_st*);
int (*gnutls_generate_server_kx) (gnutls_session_t, gnutls_buffer_st*);
int (*gnutls_generate_client_kx) (gnutls_session_t, gnutls_buffer_st*);
int (*gnutls_generate_client_cert_vrfy) (gnutls_session_t, gnutls_buffer_st *);
int (*gnutls_generate_server_certificate_request) (gnutls_session_t,
gnutls_buffer_st *);
int (*gnutls_process_server_certificate) (gnutls_session_t, opaque *,
size_t);
int (*gnutls_process_client_certificate) (gnutls_session_t, opaque *,
size_t);
int (*gnutls_process_server_kx) (gnutls_session_t, opaque *, size_t);
int (*gnutls_process_client_kx) (gnutls_session_t, opaque *, size_t);
int (*gnutls_process_client_cert_vrfy) (gnutls_session_t, opaque *, size_t);
int (*gnutls_process_server_certificate_request) (gnutls_session_t,
opaque *, size_t);
} mod_auth_st;
</pre>
<p>Those functions are responsible for the
interpretation of the handshake protocol messages. It is common for such
functions to read data from one or more <code>credentials_t</code>
structures<a name="DOCF20" href="#FOOT20"><sup>20</sup></a> and write data,
such as certificates, usernames etc. to <code>auth_info_t</code> structures.
</p>
<p>Simple examples of existing authentication methods can be seen in
<code>auth/psk.c</code> for PSK ciphersuites and <code>auth/srp.c</code> for SRP
ciphersuites. After implementing these functions the structure holding
its pointers has to be registered in <code>gnutls_algorithms.c</code> in the
<code>_gnutls_kx_algorithms</code> structure.
</p>
<div class="footnote">
<hr>
<h4 class="footnotes-heading">Footnotes</h4>
<h3><a name="FOOT20" href="#DOCF20">(20)</a></h3>
<p>such as the
<code>gnutls_certificate_credentials_t</code> structures</p>
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