7.2.1 Echo server with X.509 authentication

This example is a very simple echo server which supports X.509 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 <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>

#define KEYFILE "key.pem"
#define CERTFILE "cert.pem"
#define CAFILE "/etc/ssl/certs/ca-certificates.crt"
#define CRLFILE "crl.pem"

/* The OCSP status file contains up to date information about revocation
 * of the server's certificate. That can be periodically be updated
 * using:
 * $ ocsptool --ask --load-cert your_cert.pem --load-issuer your_issuer.pem
 *            --load-signer your_issuer.pem --outfile ocsp-status.der
 */
#define OCSP_STATUS_FILE "ocsp-status.der"

/* This is a sample TLS 1.0 echo server, using X.509 authentication and
 * OCSP stapling support.
 */

#define MAX_BUF 1024
#define PORT 5556               /* listen to 5556 port */

/* These are global */
static gnutls_dh_params_t dh_params;

static int generate_dh_params(void)
{
        unsigned int bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH,
                                                        GNUTLS_SEC_PARAM_LEGACY);

        /* Generate Diffie-Hellman parameters - for use with DHE
         * kx algorithms. When short bit length is used, it might
         * be wise to regenerate parameters often.
         */
        gnutls_dh_params_init(&dh_params);
        gnutls_dh_params_generate2(dh_params, bits);

        return 0;
}

int main(void)
{
        int listen_sd;
        int sd, ret;
        gnutls_certificate_credentials_t x509_cred;
        gnutls_priority_t priority_cache;
        struct sockaddr_in sa_serv;
        struct sockaddr_in sa_cli;
        socklen_t client_len;
        char topbuf[512];
        gnutls_session_t session;
        char buffer[MAX_BUF + 1];
        int optval = 1;

        /* this must be called once in the program
         */
        gnutls_global_init();

        gnutls_certificate_allocate_credentials(&x509_cred);
        /* gnutls_certificate_set_x509_system_trust(xcred); */
        gnutls_certificate_set_x509_trust_file(x509_cred, CAFILE,
                                               GNUTLS_X509_FMT_PEM);

        gnutls_certificate_set_x509_crl_file(x509_cred, CRLFILE,
                                             GNUTLS_X509_FMT_PEM);

        ret =
            gnutls_certificate_set_x509_key_file(x509_cred, CERTFILE,
                                                 KEYFILE,
                                                 GNUTLS_X509_FMT_PEM);
        if (ret < 0) {
                printf("No certificate or key were found\n");
                exit(1);
        }

        /* loads an OCSP status request if available */
        gnutls_certificate_set_ocsp_status_request_file(x509_cred,
                                                        OCSP_STATUS_FILE,
                                                        0);

        generate_dh_params();

        gnutls_priority_init(&priority_cache,
                             "PERFORMANCE:%SERVER_PRECEDENCE", NULL);


        gnutls_certificate_set_dh_params(x509_cred, dh_params);

        /* Socket operations
         */
        listen_sd = socket(AF_INET, SOCK_STREAM, 0);

        memset(&sa_serv, '\0', sizeof(sa_serv));
        sa_serv.sin_family = AF_INET;
        sa_serv.sin_addr.s_addr = INADDR_ANY;
        sa_serv.sin_port = htons(PORT); /* Server Port number */

        setsockopt(listen_sd, SOL_SOCKET, SO_REUSEADDR, (void *) &optval,
                   sizeof(int));

        bind(listen_sd, (struct sockaddr *) &sa_serv, sizeof(sa_serv));

        listen(listen_sd, 1024);

        printf("Server ready. Listening to port '%d'.\n\n", PORT);

        client_len = sizeof(sa_cli);
        for (;;) {
                gnutls_init(&session, GNUTLS_SERVER);
                gnutls_priority_set(session, priority_cache);
                gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE,
                                       x509_cred);
                /* We don't request any certificate from the client.
                 * If we did we would need to verify it.
                 */
                gnutls_certificate_server_set_request(session,
                                                      GNUTLS_CERT_IGNORE);

                sd = accept(listen_sd, (struct sockaddr *) &sa_cli,
                            &client_len);

                printf("- connection from %s, port %d\n",
                       inet_ntop(AF_INET, &sa_cli.sin_addr, topbuf,
                                 sizeof(topbuf)), ntohs(sa_cli.sin_port));

                gnutls_transport_set_int(session, sd);

                do {
                        ret = gnutls_handshake(session);
                }
                while (ret < 0 && gnutls_error_is_fatal(ret) == 0);

                if (ret < 0) {
                        close(sd);
                        gnutls_deinit(session);
                        fprintf(stderr,
                                "*** Handshake has failed (%s)\n\n",
                                gnutls_strerror(ret));
                        continue;
                }
                printf("- Handshake was completed\n");

                /* see the Getting peer's information example */
                /* print_info(session); */

                for (;;) {
                        ret = gnutls_record_recv(session, buffer, MAX_BUF);

                        if (ret == 0) {
                                printf
                                    ("\n- Peer has closed the GnuTLS connection\n");
                                break;
                        } else if (ret < 0
                                   && gnutls_error_is_fatal(ret) == 0) {
                                fprintf(stderr, "*** Warning: %s\n",
                                        gnutls_strerror(ret));
                        } else if (ret < 0) {
                                fprintf(stderr, "\n*** Received corrupted "
                                        "data(%d). Closing the connection.\n\n",
                                        ret);
                                break;
                        } else if (ret > 0) {
                                /* echo data back to the client
                                 */
                                gnutls_record_send(session, buffer, ret);
                        }
                }
                printf("\n");
                /* do not wait for the peer to close the connection.
                 */
                gnutls_bye(session, GNUTLS_SHUT_WR);

                close(sd);
                gnutls_deinit(session);

        }
        close(listen_sd);

        gnutls_certificate_free_credentials(x509_cred);
        gnutls_priority_deinit(priority_cache);

        gnutls_global_deinit();

        return 0;

}

This document was generated on February 9, 2014 using texi2html 5.0.