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<title>GnuTLS 3.4.9: Obtaining session information</title>
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<link href="Using-a-callback-to-select-the-certificate-to-use.html#Using-a-callback-to-select-the-certificate-to-use" rel="next" title="Using a callback to select the certificate to use">
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<a name="Obtaining-session-information"></a>
<div class="header">
<p>
Next: <a href="Using-a-callback-to-select-the-certificate-to-use.html#Using-a-callback-to-select-the-certificate-to-use" accesskey="n" rel="next">Using a callback to select the certificate to use</a>, Previous: <a href="Simple-Datagram-TLS-client-example.html#Simple-Datagram-TLS-client-example" accesskey="p" rel="prev">Simple Datagram TLS client example</a>, Up: <a href="Client-examples.html#Client-examples" accesskey="u" rel="up">Client examples</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="Obtaining-session-information-1"></a>
<h4 class="subsection">7.1.5 Obtaining session information</h4>
<p>Most of the times it is desirable to know the security properties of
the current established session. This includes the underlying ciphers
and the protocols involved. That is the purpose of the following
function. Note that this function will print meaningful values only
if called after a successful <a href="Core-TLS-API.html#gnutls_005fhandshake">gnutls_handshake</a>.
</p>
<pre class="verbatim">/* This example code is placed in the public domain. */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include "examples.h"
/* This function will print some details of the
* given session.
*/
int print_info(gnutls_session_t session)
{
const char *tmp;
gnutls_credentials_type_t cred;
gnutls_kx_algorithm_t kx;
int dhe, ecdh;
dhe = ecdh = 0;
/* print the key exchange's algorithm name
*/
kx = gnutls_kx_get(session);
tmp = gnutls_kx_get_name(kx);
printf("- Key Exchange: %s\n", tmp);
/* Check the authentication type used and switch
* to the appropriate.
*/
cred = gnutls_auth_get_type(session);
switch (cred) {
case GNUTLS_CRD_IA:
printf("- TLS/IA session\n");
break;
#ifdef ENABLE_SRP
case GNUTLS_CRD_SRP:
printf("- SRP session with username %s\n",
gnutls_srp_server_get_username(session));
break;
#endif
case GNUTLS_CRD_PSK:
/* This returns NULL in server side.
*/
if (gnutls_psk_client_get_hint(session) != NULL)
printf("- PSK authentication. PSK hint '%s'\n",
gnutls_psk_client_get_hint(session));
/* This returns NULL in client side.
*/
if (gnutls_psk_server_get_username(session) != NULL)
printf("- PSK authentication. Connected as '%s'\n",
gnutls_psk_server_get_username(session));
if (kx == GNUTLS_KX_ECDHE_PSK)
ecdh = 1;
else if (kx == GNUTLS_KX_DHE_PSK)
dhe = 1;
break;
case GNUTLS_CRD_ANON: /* anonymous authentication */
printf("- Anonymous authentication.\n");
if (kx == GNUTLS_KX_ANON_ECDH)
ecdh = 1;
else if (kx == GNUTLS_KX_ANON_DH)
dhe = 1;
break;
case GNUTLS_CRD_CERTIFICATE: /* certificate authentication */
/* Check if we have been using ephemeral Diffie-Hellman.
*/
if (kx == GNUTLS_KX_DHE_RSA || kx == GNUTLS_KX_DHE_DSS)
dhe = 1;
else if (kx == GNUTLS_KX_ECDHE_RSA
|| kx == GNUTLS_KX_ECDHE_ECDSA)
ecdh = 1;
/* if the certificate list is available, then
* print some information about it.
*/
print_x509_certificate_info(session);
} /* switch */
if (ecdh != 0)
printf("- Ephemeral ECDH using curve %s\n",
gnutls_ecc_curve_get_name(gnutls_ecc_curve_get
(session)));
else if (dhe != 0)
printf("- Ephemeral DH using prime of %d bits\n",
gnutls_dh_get_prime_bits(session));
/* print the protocol's name (ie TLS 1.0)
*/
tmp =
gnutls_protocol_get_name(gnutls_protocol_get_version(session));
printf("- Protocol: %s\n", tmp);
/* print the certificate type of the peer.
* ie X.509
*/
tmp =
gnutls_certificate_type_get_name(gnutls_certificate_type_get
(session));
printf("- Certificate Type: %s\n", tmp);
/* print the compression algorithm (if any)
*/
tmp = gnutls_compression_get_name(gnutls_compression_get(session));
printf("- Compression: %s\n", tmp);
/* print the name of the cipher used.
* ie 3DES.
*/
tmp = gnutls_cipher_get_name(gnutls_cipher_get(session));
printf("- Cipher: %s\n", tmp);
/* Print the MAC algorithms name.
* ie SHA1
*/
tmp = gnutls_mac_get_name(gnutls_mac_get(session));
printf("- MAC: %s\n", tmp);
return 0;
}
</pre>
<hr>
<div class="header">
<p>
Next: <a href="Using-a-callback-to-select-the-certificate-to-use.html#Using-a-callback-to-select-the-certificate-to-use" accesskey="n" rel="next">Using a callback to select the certificate to use</a>, Previous: <a href="Simple-Datagram-TLS-client-example.html#Simple-Datagram-TLS-client-example" accesskey="p" rel="prev">Simple Datagram TLS client example</a>, Up: <a href="Client-examples.html#Client-examples" accesskey="u" rel="up">Client examples</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>
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