7.3.7 Simple Client Example with SRP Authentication
The following client is a very simple SRP TLS
client which connects to a server and authenticates using a
username and a password. The server may authenticate
itself using a certificate, and in that case it has to be verified.
/* This example code is placed in the public domain. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gnutls/gnutls.h>
#include <gnutls/extra.h>
/* 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 "user"
#define PASSWORD "pass"
#define CAFILE "ca.pem"
#define MSG "GET / HTTP/1.0\r\n\r\n"
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;
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_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_priority_set_direct (session, "NORMAL:+SRP:+SRP-RSA:+SRP-DSS", 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_ptr (session, (gnutls_transport_ptr_t) 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, 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;
}