manual/html_node/Simple-client-example-with-SRP-authentication.html


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<title>GnuTLS 3.5.3: Simple client example with SRP authentication</title>

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<a name="Simple-client-example-with-SRP-authentication"></a>
<div class="header">
<p>
Next: <a href="Legacy-client-example-with-X_002e509-certificate-support.html#Legacy-client-example-with-X_002e509-certificate-support" accesskey="n" rel="next">Legacy client example with X.509 certificate support</a>, Previous: <a href="Client-with-Resume-capability-example.html#Client-with-Resume-capability-example" accesskey="p" rel="prev">Client with Resume capability example</a>, Up: <a href="Client-examples.html#Client-examples" accesskey="u" rel="up">Client examples</a> &nbsp; [<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="Simple-client-example-with-SRP-authentication-1"></a>
<h4 class="subsection">7.1.10 Simple client example with <acronym>SRP</acronym> authentication</h4>

<p>The following client is a very simple <acronym>SRP</acronym> <acronym>TLS</acronym>
client which connects to a server and authenticates using a
<em>username</em> and a <em>password</em>. The server may authenticate
itself using a certificate, and in that case it has to be verified.
</p>
<pre class="verbatim">/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include &lt;config.h&gt;
#endif

#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;string.h&gt;
#include &lt;gnutls/gnutls.h&gt;

/* Those functions are defined in other examples.
 */
extern void check_alert(gnutls_session_t session, int ret);
extern int tcp_connect(void);
extern void tcp_close(int sd);

#define MAX_BUF 1024
#define USERNAME &quot;user&quot;
#define PASSWORD &quot;pass&quot;
#define CAFILE &quot;/etc/ssl/certs/ca-certificates.crt&quot;
#define MSG &quot;GET / HTTP/1.0\r\n\r\n&quot;

int main(void)
{
        int ret;
        int sd, ii;
        gnutls_session_t session;
        char buffer[MAX_BUF + 1];
        gnutls_srp_client_credentials_t srp_cred;
        gnutls_certificate_credentials_t cert_cred;

        if (gnutls_check_version(&quot;3.1.4&quot;) == NULL) {
                fprintf(stderr, &quot;GnuTLS 3.1.4 or later is required for this example\n&quot;);
                exit(1);
        }

        /* for backwards compatibility with gnutls &lt; 3.3.0 */
        gnutls_global_init();

        gnutls_srp_allocate_client_credentials(&amp;srp_cred);
        gnutls_certificate_allocate_credentials(&amp;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(&amp;session, GNUTLS_CLIENT);


        /* Set the priorities.
         */
        gnutls_priority_set_direct(session,
                                   &quot;NORMAL:+SRP:+SRP-RSA:+SRP-DSS&quot;,
                                   NULL);

        /* put the SRP credentials to the current session
         */
        gnutls_credentials_set(session, GNUTLS_CRD_SRP, srp_cred);
        gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, cert_cred);

        gnutls_transport_set_int(session, sd);
        gnutls_handshake_set_timeout(session,
                                     GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);

        /* Perform the TLS handshake
         */
        do {
                ret = gnutls_handshake(session);
        }
        while (ret &lt; 0 &amp;&amp; gnutls_error_is_fatal(ret) == 0);

        if (ret &lt; 0) {
                fprintf(stderr, &quot;*** Handshake failed\n&quot;);
                gnutls_perror(ret);
                goto end;
        } else {
                char *desc;

                desc = gnutls_session_get_desc(session);
                printf(&quot;- Session info: %s\n&quot;, desc);
                gnutls_free(desc);
        }

        gnutls_record_send(session, MSG, strlen(MSG));

        ret = gnutls_record_recv(session, buffer, MAX_BUF);
        if (gnutls_error_is_fatal(ret) != 0 || ret == 0) {
                if (ret == 0) {
                        printf
                            (&quot;- Peer has closed the GnuTLS connection\n&quot;);
                        goto end;
                } else {
                        fprintf(stderr, &quot;*** Error: %s\n&quot;,
                                gnutls_strerror(ret));
                        goto end;
                }
        } else
                check_alert(session, ret);

        if (ret &gt; 0) {
                printf(&quot;- Received %d bytes: &quot;, ret);
                for (ii = 0; ii &lt; ret; ii++) {
                        fputc(buffer[ii], stdout);
                }
                fputs(&quot;\n&quot;, stdout);
        }
        gnutls_bye(session, GNUTLS_SHUT_RDWR);

      end:

        tcp_close(sd);

        gnutls_deinit(session);

        gnutls_srp_free_client_credentials(srp_cred);
        gnutls_certificate_free_credentials(cert_cred);

        gnutls_global_deinit();

        return 0;
}
</pre>

<hr>
<div class="header">
<p>
Next: <a href="Legacy-client-example-with-X_002e509-certificate-support.html#Legacy-client-example-with-X_002e509-certificate-support" accesskey="n" rel="next">Legacy client example with X.509 certificate support</a>, Previous: <a href="Client-with-Resume-capability-example.html#Client-with-Resume-capability-example" accesskey="p" rel="prev">Client with Resume capability example</a>, Up: <a href="Client-examples.html#Client-examples" accesskey="u" rel="up">Client examples</a> &nbsp; [<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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