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<title>GnuTLS 3.5.4: X.509 certificate parsing example</title>
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<a name="X_002e509-certificate-parsing-example"></a>
<div class="header">
<p>
Next: <a href="Listing-the-ciphersuites-in-a-priority-string.html#Listing-the-ciphersuites-in-a-priority-string" accesskey="n" rel="next">Listing the ciphersuites in a priority string</a>, Previous: <a href="Checking-for-an-alert.html#Checking-for-an-alert" accesskey="p" rel="prev">Checking for an alert</a>, Up: <a href="Miscellaneous-examples.html#Miscellaneous-examples" accesskey="u" rel="up">Miscellaneous 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="X_002e509-certificate-parsing-example-1"></a>
<h4 class="subsection">7.4.2 <acronym>X.509</acronym> certificate parsing example</h4>
<a name="ex_002dx509_002dinfo"></a>
<p>To demonstrate the <acronym>X.509</acronym> parsing capabilities an example program is
listed below. That program reads the peer’s certificate, and prints
information about it.
</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"
static const char *bin2hex(const void *bin, size_t bin_size)
{
static char printable[110];
const unsigned char *_bin = bin;
char *print;
size_t i;
if (bin_size > 50)
bin_size = 50;
print = printable;
for (i = 0; i < bin_size; i++) {
sprintf(print, "%.2x ", _bin[i]);
print += 2;
}
return printable;
}
/* This function will print information about this session's peer
* certificate.
*/
void print_x509_certificate_info(gnutls_session_t session)
{
char serial[40];
char dn[256];
size_t size;
unsigned int algo, bits;
time_t expiration_time, activation_time;
const gnutls_datum_t *cert_list;
unsigned int cert_list_size = 0;
gnutls_x509_crt_t cert;
gnutls_datum_t cinfo;
/* This function only works for X.509 certificates.
*/
if (gnutls_certificate_type_get(session) != GNUTLS_CRT_X509)
return;
cert_list = gnutls_certificate_get_peers(session, &cert_list_size);
printf("Peer provided %d certificates.\n", cert_list_size);
if (cert_list_size > 0) {
int ret;
/* we only print information about the first certificate.
*/
gnutls_x509_crt_init(&cert);
gnutls_x509_crt_import(cert, &cert_list[0],
GNUTLS_X509_FMT_DER);
printf("Certificate info:\n");
/* This is the preferred way of printing short information about
a certificate. */
ret =
gnutls_x509_crt_print(cert, GNUTLS_CRT_PRINT_ONELINE,
&cinfo);
if (ret == 0) {
printf("\t%s\n", cinfo.data);
gnutls_free(cinfo.data);
}
/* If you want to extract fields manually for some other reason,
below are popular example calls. */
expiration_time =
gnutls_x509_crt_get_expiration_time(cert);
activation_time =
gnutls_x509_crt_get_activation_time(cert);
printf("\tCertificate is valid since: %s",
ctime(&activation_time));
printf("\tCertificate expires: %s",
ctime(&expiration_time));
/* Print the serial number of the certificate.
*/
size = sizeof(serial);
gnutls_x509_crt_get_serial(cert, serial, &size);
printf("\tCertificate serial number: %s\n",
bin2hex(serial, size));
/* Extract some of the public key algorithm's parameters
*/
algo = gnutls_x509_crt_get_pk_algorithm(cert, &bits);
printf("Certificate public key: %s",
gnutls_pk_algorithm_get_name(algo));
/* Print the version of the X.509
* certificate.
*/
printf("\tCertificate version: #%d\n",
gnutls_x509_crt_get_version(cert));
size = sizeof(dn);
gnutls_x509_crt_get_dn(cert, dn, &size);
printf("\tDN: %s\n", dn);
size = sizeof(dn);
gnutls_x509_crt_get_issuer_dn(cert, dn, &size);
printf("\tIssuer's DN: %s\n", dn);
gnutls_x509_crt_deinit(cert);
}
}
</pre>
<hr>
<div class="header">
<p>
Next: <a href="Listing-the-ciphersuites-in-a-priority-string.html#Listing-the-ciphersuites-in-a-priority-string" accesskey="n" rel="next">Listing the ciphersuites in a priority string</a>, Previous: <a href="Checking-for-an-alert.html#Checking-for-an-alert" accesskey="p" rel="prev">Checking for an alert</a>, Up: <a href="Miscellaneous-examples.html#Miscellaneous-examples" accesskey="u" rel="up">Miscellaneous 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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