Next: , Previous: , Up: More advanced client and servers   [Contents][Index]


7.3.9 Echo server with PSK authentication

This is a server which supports PSK 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"

#define LOOP_CHECK(rval, cmd) \
        do { \
                rval = cmd; \
        } while(rval == GNUTLS_E_AGAIN || rval == GNUTLS_E_INTERRUPTED)

/* This is a sample TLS echo server, supporting X.509 and PSK
   authentication.
 */

#define SOCKET_ERR(err,s) if(err==-1) {perror(s);return(1);}
#define MAX_BUF 1024
#define PORT 5556               /* listen to 5556 port */

static int
pskfunc(gnutls_session_t session, const char *username,
        gnutls_datum_t * key)
{
        printf("psk: username %s\n", username);
        key->data = gnutls_malloc(4);
        key->data[0] = 0xDE;
        key->data[1] = 0xAD;
        key->data[2] = 0xBE;
        key->data[3] = 0xEF;
        key->size = 4;
        return 0;
}

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

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

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

        gnutls_certificate_allocate_credentials(&x509_cred);
        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);

        gnutls_certificate_set_x509_key_file(x509_cred, CERTFILE, KEYFILE,
                                             GNUTLS_X509_FMT_PEM);

        gnutls_psk_allocate_server_credentials(&psk_cred);
        gnutls_psk_set_server_credentials_function(psk_cred, pskfunc);

        /* pre-3.6.3 equivalent:
         * gnutls_priority_init(&priority_cache,
         *                      "NORMAL:+PSK:+ECDHE-PSK:+DHE-PSK",
         *                      NULL);
         */
        gnutls_priority_init2(&priority_cache,
                              "+ECDHE-PSK:+DHE-PSK:+PSK",
                              NULL, GNUTLS_PRIORITY_INIT_DEF_APPEND);

        gnutls_certificate_set_known_dh_params(x509_cred, GNUTLS_SEC_PARAM_MEDIUM);

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

        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));

        err =
            bind(listen_sd, (struct sockaddr *) &sa_serv, sizeof(sa_serv));
        SOCKET_ERR(err, "bind");
        err = listen(listen_sd, 1024);
        SOCKET_ERR(err, "listen");

        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);
                gnutls_credentials_set(session, GNUTLS_CRD_PSK, psk_cred);

                /* request client certificate if any.
                 */
                gnutls_certificate_server_set_request(session,
                                                      GNUTLS_CERT_REQUEST);

                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);
                LOOP_CHECK(ret, gnutls_handshake(session));
                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");

                kx = gnutls_kx_get(session);
                if (kx == GNUTLS_KX_PSK || kx == GNUTLS_KX_DHE_PSK ||
                    kx == GNUTLS_KX_ECDHE_PSK) {
                        printf("- User %s was connected\n",
                               gnutls_psk_server_get_username(session));
                }

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

                for (;;) {
                        LOOP_CHECK(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.
                 */
                LOOP_CHECK(ret, gnutls_bye(session, GNUTLS_SHUT_WR));

                close(sd);
                gnutls_deinit(session);

        }
        close(listen_sd);

        gnutls_certificate_free_credentials(x509_cred);
        gnutls_psk_free_server_credentials(psk_cred);

        gnutls_priority_deinit(priority_cache);

        gnutls_global_deinit();

        return 0;

}

Next: , Previous: , Up: More advanced client and servers   [Contents][Index]