doc/examples/ex-serv-dtls.c

   1 /* This example code is placed in the public domain. */
   2
   3 #ifdef HAVE_CONFIG_H
   4 #include <config.h>
   5 #endif
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <errno.h>
  10 #include <sys/types.h>
  11 #include <sys/socket.h>
  12 #include <arpa/inet.h>
  13 #include <netinet/in.h>
  14 #include <sys/select.h>
  15 #include <netdb.h>
  16 #include <string.h>
  17 #include <unistd.h>
  18 #include <gnutls/gnutls.h>
  19 #include <gnutls/dtls.h>
  20
  21 #define KEYFILE "key.pem"
  22 #define CERTFILE "cert.pem"
  23 #define CAFILE "/etc/ssl/certs/ca-certificates.crt"
  24 #define CRLFILE "crl.pem"
  25
  26 /* This is a sample DTLS echo server, using X.509 authentication.
  27  * Note that error checking is minimal to simplify the example.
  28  */
  29
  30 #define MAX_BUFFER 1024
  31 #define PORT 5556
  32
  33 typedef struct
  34 {
  35   gnutls_session_t session;
  36   int fd;
  37   struct sockaddr *cli_addr;
  38   socklen_t cli_addr_size;
  39 } priv_data_st;
  40
  41 static int pull_timeout_func (gnutls_transport_ptr_t ptr, unsigned int ms);
  42 static ssize_t push_func (gnutls_transport_ptr_t p, const void *data,
  43                           size_t size);
  44 static ssize_t pull_func (gnutls_transport_ptr_t p, void *data, size_t size);
  45 static const char *human_addr (const struct sockaddr *sa, socklen_t salen,
  46                                char *buf, size_t buflen);
  47 static int wait_for_connection (int fd);
  48 static gnutls_session_t initialize_tls_session (void);
  49 static int generate_dh_params (void);
  50
  51 /* Use global credentials and parameters to simplify
  52  * the example. */
  53 static gnutls_certificate_credentials_t x509_cred;
  54 static gnutls_priority_t priority_cache;
  55 static gnutls_dh_params_t dh_params;
  56
  57 int
  58 main (void)
  59 {
  60   int listen_sd;
  61   int sock, ret;
  62   struct sockaddr_in sa_serv;
  63   struct sockaddr_in cli_addr;
  64   socklen_t cli_addr_size;
  65   gnutls_session_t session;
  66   char buffer[MAX_BUFFER];
  67   priv_data_st priv;
  68   gnutls_datum_t cookie_key;
  69   gnutls_dtls_prestate_st prestate;
  70   int mtu = 1400;
  71   unsigned char sequence[8];
  72
  73   /* this must be called once in the program
  74    */
  75   gnutls_global_init ();
  76
  77   gnutls_certificate_allocate_credentials (&x509_cred);
  78   gnutls_certificate_set_x509_trust_file (x509_cred, CAFILE,
  79                                           GNUTLS_X509_FMT_PEM);
  80
  81   gnutls_certificate_set_x509_crl_file (x509_cred, CRLFILE,
  82                                         GNUTLS_X509_FMT_PEM);
  83
  84   ret = gnutls_certificate_set_x509_key_file (x509_cred, CERTFILE, KEYFILE,
  85                                         GNUTLS_X509_FMT_PEM);
  86   if (ret < 0)
  87     {
  88       printf("No certificate or key were found\n");
  89       exit(1);
  90     }
  91
  92   generate_dh_params ();
  93
  94   gnutls_certificate_set_dh_params (x509_cred, dh_params);
  95
  96   gnutls_priority_init (&priority_cache,
  97                         "PERFORMANCE:-VERS-TLS-ALL:+VERS-DTLS1.0:%SERVER_PRECEDENCE",
  98                         NULL);
  99
 100   gnutls_key_generate (&cookie_key, GNUTLS_COOKIE_KEY_SIZE);
 101
 102   /* Socket operations
 103    */
 104   listen_sd = socket (AF_INET, SOCK_DGRAM, 0);
 105
 106   memset (&sa_serv, '\0', sizeof (sa_serv));
 107   sa_serv.sin_family = AF_INET;
 108   sa_serv.sin_addr.s_addr = INADDR_ANY;
 109   sa_serv.sin_port = htons (PORT);
 110
 111   { /* DTLS requires the IP don't fragment (DF) bit to be set */
 112 #if defined(IP_DONTFRAG)
 113     int optval = 1;
 114     setsockopt (listen_sd, IPPROTO_IP, IP_DONTFRAG,
 115                 (const void *) &optval, sizeof (optval));
 116 #elif defined(IP_MTU_DISCOVER)
 117     int optval = IP_PMTUDISC_DO;
 118     setsockopt(listen_sd, IPPROTO_IP, IP_MTU_DISCOVER,
 119                (const void*) &optval, sizeof (optval));
 120 #endif
 121   }
 122
 123   bind (listen_sd, (struct sockaddr *) &sa_serv, sizeof (sa_serv));
 124
 125   printf ("UDP server ready. Listening to port '%d'.\n\n", PORT);
 126
 127   for (;;)
 128     {
 129       printf ("Waiting for connection...\n");
 130       sock = wait_for_connection (listen_sd);
 131       if (sock < 0)
 132         continue;
 133
 134       cli_addr_size = sizeof (cli_addr);
 135       ret = recvfrom (sock, buffer, sizeof (buffer), MSG_PEEK,
 136                       (struct sockaddr *) &cli_addr, &cli_addr_size);
 137       if (ret > 0)
 138         {
 139           memset (&prestate, 0, sizeof (prestate));
 140           ret = gnutls_dtls_cookie_verify (&cookie_key, &cli_addr,
 141                                            sizeof (cli_addr), buffer, ret,
 142                                            &prestate);
 143           if (ret < 0)          /* cookie not valid */
 144             {
 145               priv_data_st s;
 146
 147               memset (&s, 0, sizeof (s));
 148               s.fd = sock;
 149               s.cli_addr = (void *) &cli_addr;
 150               s.cli_addr_size = sizeof (cli_addr);
 151
 152               printf ("Sending hello verify request to %s\n",
 153                       human_addr ((struct sockaddr *) &cli_addr,
 154                                   sizeof (cli_addr), buffer,
 155                                   sizeof (buffer)));
 156
 157               gnutls_dtls_cookie_send (&cookie_key, &cli_addr,
 158                                        sizeof (cli_addr), &prestate,
 159                                        (gnutls_transport_ptr_t) & s,
 160                                        push_func);
 161
 162               /* discard peeked data */
 163               recvfrom (sock, buffer, sizeof (buffer), 0,
 164                         (struct sockaddr *) &cli_addr, &cli_addr_size);
 165               usleep (100);
 166               continue;
 167             }
 168           printf ("Accepted connection from %s\n",
 169                   human_addr ((struct sockaddr *)
 170                               &cli_addr, sizeof (cli_addr), buffer,
 171                               sizeof (buffer)));
 172         }
 173       else
 174         continue;
 175
 176       session = initialize_tls_session ();
 177       gnutls_dtls_prestate_set (session, &prestate);
 178       gnutls_dtls_set_mtu (session, mtu);
 179
 180       priv.session = session;
 181       priv.fd = sock;
 182       priv.cli_addr = (struct sockaddr *) &cli_addr;
 183       priv.cli_addr_size = sizeof (cli_addr);
 184
 185       gnutls_transport_set_ptr (session, &priv);
 186       gnutls_transport_set_push_function (session, push_func);
 187       gnutls_transport_set_pull_function (session, pull_func);
 188       gnutls_transport_set_pull_timeout_function (session, pull_timeout_func);
 189
 190       do
 191         {
 192           ret = gnutls_handshake (session);
 193         }
 194       while (ret < 0 && gnutls_error_is_fatal (ret) == 0);
 195
 196       if (ret < 0)
 197         {
 198           fprintf (stderr, "Error in handshake(): %s\n",
 199                    gnutls_strerror (ret));
 200           gnutls_deinit (session);
 201           continue;
 202         }
 203
 204       printf ("- Handshake was completed\n");
 205
 206       for (;;)
 207         {
 208           do
 209             {
 210               ret = gnutls_record_recv_seq (session, buffer, MAX_BUFFER,
 211                                             sequence);
 212             }
 213           while (ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED);
 214
 215           if (ret < 0)
 216             {
 217               fprintf (stderr, "Error in recv(): %s\n",
 218                        gnutls_strerror (ret));
 219               break;
 220             }
 221           if (ret == 0)
 222             {
 223               printf ("EOF\n\n");
 224               break;
 225             }
 226           buffer[ret] = 0;
 227           printf ("received[%.2x%.2x%.2x%.2x%.2x%.2x%.2x%.2x]: %s\n",
 228                   sequence[0], sequence[1], sequence[2], sequence[3],
 229                   sequence[4], sequence[5], sequence[6], sequence[7], buffer);
 230
 231           /* reply back */
 232           ret = gnutls_record_send (session, buffer, ret);
 233           if (ret < 0)
 234             {
 235               fprintf (stderr, "Error in send(): %s\n",
 236                        gnutls_strerror (ret));
 237               break;
 238             }
 239         }
 240
 241       gnutls_bye (session, GNUTLS_SHUT_WR);
 242       gnutls_deinit (session);
 243
 244     }
 245   close (listen_sd);
 246
 247   gnutls_certificate_free_credentials (x509_cred);
 248   gnutls_priority_deinit (priority_cache);
 249
 250   gnutls_global_deinit ();
 251
 252   return 0;
 253
 254 }
 255
 256 static int
 257 wait_for_connection (int fd)
 258 {
 259   fd_set rd, wr;
 260   int n;
 261
 262   FD_ZERO (&rd);
 263   FD_ZERO (&wr);
 264
 265   FD_SET (fd, &rd);
 266
 267   /* waiting part */
 268   n = select (fd + 1, &rd, &wr, NULL, NULL);
 269   if (n == -1 && errno == EINTR)
 270     return -1;
 271   if (n < 0)
 272     {
 273       perror ("select()");
 274       exit (1);
 275     }
 276
 277   return fd;
 278 }
 279
 280 /* Wait for data to be received within a timeout period in milliseconds
 281  */
 282 static int
 283 pull_timeout_func (gnutls_transport_ptr_t ptr, unsigned int ms)
 284 {
 285   fd_set rfds;
 286   struct timeval tv;
 287   priv_data_st *priv = ptr;
 288   struct sockaddr_in cli_addr;
 289   socklen_t cli_addr_size;
 290   int ret;
 291   char c;
 292
 293   FD_ZERO (&rfds);
 294   FD_SET (priv->fd, &rfds);
 295
 296   tv.tv_sec = 0;
 297   tv.tv_usec = ms * 1000;
 298
 299   ret = select (priv->fd + 1, &rfds, NULL, NULL, &tv);
 300
 301   if (ret <= 0)
 302     return ret;
 303
 304   /* only report ok if the next message is from the peer we expect
 305    * from
 306    */
 307   cli_addr_size = sizeof (cli_addr);
 308   ret =
 309     recvfrom (priv->fd, &c, 1, MSG_PEEK, (struct sockaddr *) &cli_addr,
 310               &cli_addr_size);
 311   if (ret > 0)
 312     {
 313       if (cli_addr_size == priv->cli_addr_size
 314           && memcmp (&cli_addr, priv->cli_addr, sizeof (cli_addr)) == 0)
 315         return 1;
 316     }
 317
 318   return 0;
 319 }
 320
 321 static ssize_t
 322 push_func (gnutls_transport_ptr_t p, const void *data, size_t size)
 323 {
 324   priv_data_st *priv = p;
 325
 326   return sendto (priv->fd, data, size, 0, priv->cli_addr,
 327                  priv->cli_addr_size);
 328 }
 329
 330 static ssize_t
 331 pull_func (gnutls_transport_ptr_t p, void *data, size_t size)
 332 {
 333   priv_data_st *priv = p;
 334   struct sockaddr_in cli_addr;
 335   socklen_t cli_addr_size;
 336   char buffer[64];
 337   int ret;
 338
 339   cli_addr_size = sizeof (cli_addr);
 340   ret =
 341     recvfrom (priv->fd, data, size, 0, (struct sockaddr *) &cli_addr,
 342               &cli_addr_size);
 343   if (ret == -1)
 344     return ret;
 345
 346   if (cli_addr_size == priv->cli_addr_size
 347       && memcmp (&cli_addr, priv->cli_addr, sizeof (cli_addr)) == 0)
 348     return ret;
 349
 350   printf ("Denied connection from %s\n",
 351           human_addr ((struct sockaddr *)
 352                       &cli_addr, sizeof (cli_addr), buffer, sizeof (buffer)));
 353
 354   gnutls_transport_set_errno (priv->session, EAGAIN);
 355   return -1;
 356 }
 357
 358 static const char *
 359 human_addr (const struct sockaddr *sa, socklen_t salen,
 360             char *buf, size_t buflen)
 361 {
 362   const char *save_buf = buf;
 363   size_t l;
 364
 365   if (!buf || !buflen)
 366     return NULL;
 367
 368   *buf = '\0';
 369
 370   switch (sa->sa_family)
 371     {
 372 #if HAVE_IPV6
 373     case AF_INET6:
 374       snprintf (buf, buflen, "IPv6 ");
 375       break;
 376 #endif
 377
 378     case AF_INET:
 379       snprintf (buf, buflen, "IPv4 ");
 380       break;
 381     }
 382
 383   l = strlen (buf);
 384   buf += l;
 385   buflen -= l;
 386
 387   if (getnameinfo (sa, salen, buf, buflen, NULL, 0, NI_NUMERICHOST) != 0)
 388     return NULL;
 389
 390   l = strlen (buf);
 391   buf += l;
 392   buflen -= l;
 393
 394   strncat (buf, " port ", buflen);
 395
 396   l = strlen (buf);
 397   buf += l;
 398   buflen -= l;
 399
 400   if (getnameinfo (sa, salen, NULL, 0, buf, buflen, NI_NUMERICSERV) != 0)
 401     return NULL;
 402
 403   return save_buf;
 404 }
 405
 406 static gnutls_session_t
 407 initialize_tls_session (void)
 408 {
 409   gnutls_session_t session;
 410
 411   gnutls_init (&session, GNUTLS_SERVER | GNUTLS_DATAGRAM);
 412
 413   gnutls_priority_set (session, priority_cache);
 414
 415   gnutls_credentials_set (session, GNUTLS_CRD_CERTIFICATE, x509_cred);
 416
 417   return session;
 418 }
 419
 420 static int
 421 generate_dh_params (void)
 422 {
 423   int bits = gnutls_sec_param_to_pk_bits (GNUTLS_PK_DH, GNUTLS_SEC_PARAM_LOW);
 424
 425   /* Generate Diffie-Hellman parameters - for use with DHE
 426    * kx algorithms. When short bit length is used, it might
 427    * be wise to regenerate parameters often.
 428    */
 429   gnutls_dh_params_init (&dh_params);
 430   gnutls_dh_params_generate2 (dh_params, bits);
 431
 432   return 0;
 433 }