7.5.1 Example client with X.509 certificate authentication

/* 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/xssl.h>
#include "examples.h"

/* A simple TLS client, with X.509 authentication. Certificate verification
 * is explicit.
 */

extern int tcp_connect(void);
extern void tcp_close(int sd);

int main(void)
{
        int ret;
        char *line = NULL;
        size_t line_len;
        xssl_cred_t cred;
        xssl_t sb;
        unsigned int status;
        int fd;

        gnutls_global_init();

        fd = tcp_connect();

        ret = xssl_cred_init(&cred, GNUTLS_VMETHOD_SYSTEM_CAS, NULL, 0);
        if (ret < 0)
                exit(1);

        /* Initialize TLS session
         */
        ret = xssl_client_init(&sb, "www.example.com", NULL,
                               (gnutls_transport_ptr_t) fd,
                               NULL, cred, &status, 0);
        if (ret < 0) {
                if (ret == GNUTLS_E_AUTH_ERROR) {
                        gnutls_datum_t txt;

                        gnutls_certificate_verification_status_print
                            (status, GNUTLS_CRT_X509, &txt, 0);

                        fprintf(stderr, "Verification error (%x): %s\n",
                                status, txt.data);
                        gnutls_free(txt.data);
                }
                exit(1);
        }
#define REQ "GET / HTTP/1.0\r\n"
        ret = xssl_write(sb, REQ, sizeof(REQ) - 1);
        if (ret < 0)
                exit(1);

        do {
                ret = xssl_getline(sb, &line, &line_len);
                if (ret < 0)
                        exit(1);

                fprintf(stderr, "received: %s\n", line);
        }
        while (ret >= 0);

        gnutls_free(line);

        xssl_deinit(sb);

        tcp_close(fd);

        xssl_cred_deinit(cred);

        gnutls_global_deinit();

        return 0;
}

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