ssl/d1_lib.c

   1 /*
   2  * Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include <stdio.h>
  11 #define USE_SOCKETS
  12 #include <openssl/objects.h>
  13 #include <openssl/rand.h>
  14 #include "ssl_locl.h"
  15
  16 #if defined(OPENSSL_SYS_VMS)
  17 # include <sys/timeb.h>
  18 #elif defined(OPENSSL_SYS_VXWORKS)
  19 # include <sys/times.h>
  20 #elif !defined(OPENSSL_SYS_WIN32)
  21 # include <sys/time.h>
  22 #endif
  23
  24 static void get_current_time(struct timeval *t);
  25 static int dtls1_handshake_write(SSL *s);
  26 static size_t dtls1_link_min_mtu(void);
  27
  28 /* XDTLS:  figure out the right values */
  29 static const size_t g_probable_mtu[] = { 1500, 512, 256 };
  30
  31 const SSL3_ENC_METHOD DTLSv1_enc_data = {
  32     tls1_enc,
  33     tls1_mac,
  34     tls1_setup_key_block,
  35     tls1_generate_master_secret,
  36     tls1_change_cipher_state,
  37     tls1_final_finish_mac,
  38     TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE,
  39     TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE,
  40     tls1_alert_code,
  41     tls1_export_keying_material,
  42     SSL_ENC_FLAG_DTLS | SSL_ENC_FLAG_EXPLICIT_IV,
  43     dtls1_set_handshake_header,
  44     dtls1_close_construct_packet,
  45     dtls1_handshake_write
  46 };
  47
  48 const SSL3_ENC_METHOD DTLSv1_2_enc_data = {
  49     tls1_enc,
  50     tls1_mac,
  51     tls1_setup_key_block,
  52     tls1_generate_master_secret,
  53     tls1_change_cipher_state,
  54     tls1_final_finish_mac,
  55     TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE,
  56     TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE,
  57     tls1_alert_code,
  58     tls1_export_keying_material,
  59     SSL_ENC_FLAG_DTLS | SSL_ENC_FLAG_EXPLICIT_IV | SSL_ENC_FLAG_SIGALGS
  60         | SSL_ENC_FLAG_SHA256_PRF | SSL_ENC_FLAG_TLS1_2_CIPHERS,
  61     dtls1_set_handshake_header,
  62     dtls1_close_construct_packet,
  63     dtls1_handshake_write
  64 };
  65
  66 long dtls1_default_timeout(void)
  67 {
  68     /*
  69      * 2 hours, the 24 hours mentioned in the DTLSv1 spec is way too long for
  70      * http, the cache would over fill
  71      */
  72     return (60 * 60 * 2);
  73 }
  74
  75 int dtls1_new(SSL *s)
  76 {
  77     DTLS1_STATE *d1;
  78
  79     if (!DTLS_RECORD_LAYER_new(&s->rlayer)) {
  80         return 0;
  81     }
  82
  83     if (!ssl3_new(s))
  84         return (0);
  85     if ((d1 = OPENSSL_zalloc(sizeof(*d1))) == NULL) {
  86         ssl3_free(s);
  87         return (0);
  88     }
  89
  90     d1->buffered_messages = pqueue_new();
  91     d1->sent_messages = pqueue_new();
  92
  93     if (s->server) {
  94         d1->cookie_len = sizeof(s->d1->cookie);
  95     }
  96
  97     d1->link_mtu = 0;
  98     d1->mtu = 0;
  99
 100     if (d1->buffered_messages == NULL || d1->sent_messages == NULL) {
 101         pqueue_free(d1->buffered_messages);
 102         pqueue_free(d1->sent_messages);
 103         OPENSSL_free(d1);
 104         ssl3_free(s);
 105         return (0);
 106     }
 107
 108     s->d1 = d1;
 109     s->method->ssl_clear(s);
 110     return (1);
 111 }
 112
 113 static void dtls1_clear_queues(SSL *s)
 114 {
 115     dtls1_clear_received_buffer(s);
 116     dtls1_clear_sent_buffer(s);
 117 }
 118
 119 void dtls1_clear_received_buffer(SSL *s)
 120 {
 121     pitem *item = NULL;
 122     hm_fragment *frag = NULL;
 123
 124     while ((item = pqueue_pop(s->d1->buffered_messages)) != NULL) {
 125         frag = (hm_fragment *)item->data;
 126         dtls1_hm_fragment_free(frag);
 127         pitem_free(item);
 128     }
 129 }
 130
 131 void dtls1_clear_sent_buffer(SSL *s)
 132 {
 133     pitem *item = NULL;
 134     hm_fragment *frag = NULL;
 135
 136     while ((item = pqueue_pop(s->d1->sent_messages)) != NULL) {
 137         frag = (hm_fragment *)item->data;
 138         dtls1_hm_fragment_free(frag);
 139         pitem_free(item);
 140     }
 141 }
 142
 143
 144 void dtls1_free(SSL *s)
 145 {
 146     DTLS_RECORD_LAYER_free(&s->rlayer);
 147
 148     ssl3_free(s);
 149
 150     dtls1_clear_queues(s);
 151
 152     pqueue_free(s->d1->buffered_messages);
 153     pqueue_free(s->d1->sent_messages);
 154
 155     OPENSSL_free(s->d1);
 156     s->d1 = NULL;
 157 }
 158
 159 void dtls1_clear(SSL *s)
 160 {
 161     pqueue *buffered_messages;
 162     pqueue *sent_messages;
 163     size_t mtu;
 164     size_t link_mtu;
 165
 166     DTLS_RECORD_LAYER_clear(&s->rlayer);
 167
 168     if (s->d1) {
 169         buffered_messages = s->d1->buffered_messages;
 170         sent_messages = s->d1->sent_messages;
 171         mtu = s->d1->mtu;
 172         link_mtu = s->d1->link_mtu;
 173
 174         dtls1_clear_queues(s);
 175
 176         memset(s->d1, 0, sizeof(*s->d1));
 177
 178         if (s->server) {
 179             s->d1->cookie_len = sizeof(s->d1->cookie);
 180         }
 181
 182         if (SSL_get_options(s) & SSL_OP_NO_QUERY_MTU) {
 183             s->d1->mtu = mtu;
 184             s->d1->link_mtu = link_mtu;
 185         }
 186
 187         s->d1->buffered_messages = buffered_messages;
 188         s->d1->sent_messages = sent_messages;
 189     }
 190
 191     ssl3_clear(s);
 192
 193     if (s->method->version == DTLS_ANY_VERSION)
 194         s->version = DTLS_MAX_VERSION;
 195 #ifndef OPENSSL_NO_DTLS1_METHOD
 196     else if (s->options & SSL_OP_CISCO_ANYCONNECT)
 197         s->client_version = s->version = DTLS1_BAD_VER;
 198 #endif
 199     else
 200         s->version = s->method->version;
 201 }
 202
 203 long dtls1_ctrl(SSL *s, int cmd, long larg, void *parg)
 204 {
 205     int ret = 0;
 206
 207     switch (cmd) {
 208     case DTLS_CTRL_GET_TIMEOUT:
 209         if (dtls1_get_timeout(s, (struct timeval *)parg) != NULL) {
 210             ret = 1;
 211         }
 212         break;
 213     case DTLS_CTRL_HANDLE_TIMEOUT:
 214         ret = dtls1_handle_timeout(s);
 215         break;
 216     case DTLS_CTRL_SET_LINK_MTU:
 217         if (larg < (long)dtls1_link_min_mtu())
 218             return 0;
 219         s->d1->link_mtu = larg;
 220         return 1;
 221     case DTLS_CTRL_GET_LINK_MIN_MTU:
 222         return (long)dtls1_link_min_mtu();
 223     case SSL_CTRL_SET_MTU:
 224         /*
 225          *  We may not have a BIO set yet so can't call dtls1_min_mtu()
 226          *  We'll have to make do with dtls1_link_min_mtu() and max overhead
 227          */
 228         if (larg < (long)dtls1_link_min_mtu() - DTLS1_MAX_MTU_OVERHEAD)
 229             return 0;
 230         s->d1->mtu = larg;
 231         return larg;
 232     default:
 233         ret = ssl3_ctrl(s, cmd, larg, parg);
 234         break;
 235     }
 236     return (ret);
 237 }
 238
 239 void dtls1_start_timer(SSL *s)
 240 {
 241 #ifndef OPENSSL_NO_SCTP
 242     /* Disable timer for SCTP */
 243     if (BIO_dgram_is_sctp(SSL_get_wbio(s))) {
 244         memset(&s->d1->next_timeout, 0, sizeof(s->d1->next_timeout));
 245         return;
 246     }
 247 #endif
 248
 249     /* If timer is not set, initialize duration with 1 second */
 250     if (s->d1->next_timeout.tv_sec == 0 && s->d1->next_timeout.tv_usec == 0) {
 251         s->d1->timeout_duration = 1;
 252     }
 253
 254     /* Set timeout to current time */
 255     get_current_time(&(s->d1->next_timeout));
 256
 257     /* Add duration to current time */
 258     s->d1->next_timeout.tv_sec += s->d1->timeout_duration;
 259     BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT, 0,
 260              &(s->d1->next_timeout));
 261 }
 262
 263 struct timeval *dtls1_get_timeout(SSL *s, struct timeval *timeleft)
 264 {
 265     struct timeval timenow;
 266
 267     /* If no timeout is set, just return NULL */
 268     if (s->d1->next_timeout.tv_sec == 0 && s->d1->next_timeout.tv_usec == 0) {
 269         return NULL;
 270     }
 271
 272     /* Get current time */
 273     get_current_time(&timenow);
 274
 275     /* If timer already expired, set remaining time to 0 */
 276     if (s->d1->next_timeout.tv_sec < timenow.tv_sec ||
 277         (s->d1->next_timeout.tv_sec == timenow.tv_sec &&
 278          s->d1->next_timeout.tv_usec <= timenow.tv_usec)) {
 279         memset(timeleft, 0, sizeof(*timeleft));
 280         return timeleft;
 281     }
 282
 283     /* Calculate time left until timer expires */
 284     memcpy(timeleft, &(s->d1->next_timeout), sizeof(struct timeval));
 285     timeleft->tv_sec -= timenow.tv_sec;
 286     timeleft->tv_usec -= timenow.tv_usec;
 287     if (timeleft->tv_usec < 0) {
 288         timeleft->tv_sec--;
 289         timeleft->tv_usec += 1000000;
 290     }
 291
 292     /*
 293      * If remaining time is less than 15 ms, set it to 0 to prevent issues
 294      * because of small divergences with socket timeouts.
 295      */
 296     if (timeleft->tv_sec == 0 && timeleft->tv_usec < 15000) {
 297         memset(timeleft, 0, sizeof(*timeleft));
 298     }
 299
 300     return timeleft;
 301 }
 302
 303 int dtls1_is_timer_expired(SSL *s)
 304 {
 305     struct timeval timeleft;
 306
 307     /* Get time left until timeout, return false if no timer running */
 308     if (dtls1_get_timeout(s, &timeleft) == NULL) {
 309         return 0;
 310     }
 311
 312     /* Return false if timer is not expired yet */
 313     if (timeleft.tv_sec > 0 || timeleft.tv_usec > 0) {
 314         return 0;
 315     }
 316
 317     /* Timer expired, so return true */
 318     return 1;
 319 }
 320
 321 void dtls1_double_timeout(SSL *s)
 322 {
 323     s->d1->timeout_duration *= 2;
 324     if (s->d1->timeout_duration > 60)
 325         s->d1->timeout_duration = 60;
 326     dtls1_start_timer(s);
 327 }
 328
 329 void dtls1_stop_timer(SSL *s)
 330 {
 331     /* Reset everything */
 332     memset(&s->d1->timeout, 0, sizeof(s->d1->timeout));
 333     memset(&s->d1->next_timeout, 0, sizeof(s->d1->next_timeout));
 334     s->d1->timeout_duration = 1;
 335     BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT, 0,
 336              &(s->d1->next_timeout));
 337     /* Clear retransmission buffer */
 338     dtls1_clear_sent_buffer(s);
 339 }
 340
 341 int dtls1_check_timeout_num(SSL *s)
 342 {
 343     size_t mtu;
 344
 345     s->d1->timeout.num_alerts++;
 346
 347     /* Reduce MTU after 2 unsuccessful retransmissions */
 348     if (s->d1->timeout.num_alerts > 2
 349         && !(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) {
 350         mtu =
 351             BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_GET_FALLBACK_MTU, 0, NULL);
 352         if (mtu < s->d1->mtu)
 353             s->d1->mtu = mtu;
 354     }
 355
 356     if (s->d1->timeout.num_alerts > DTLS1_TMO_ALERT_COUNT) {
 357         /* fail the connection, enough alerts have been sent */
 358         SSLerr(SSL_F_DTLS1_CHECK_TIMEOUT_NUM, SSL_R_READ_TIMEOUT_EXPIRED);
 359         return -1;
 360     }
 361
 362     return 0;
 363 }
 364
 365 int dtls1_handle_timeout(SSL *s)
 366 {
 367     /* if no timer is expired, don't do anything */
 368     if (!dtls1_is_timer_expired(s)) {
 369         return 0;
 370     }
 371
 372     dtls1_double_timeout(s);
 373
 374     if (dtls1_check_timeout_num(s) < 0)
 375         return -1;
 376
 377     s->d1->timeout.read_timeouts++;
 378     if (s->d1->timeout.read_timeouts > DTLS1_TMO_READ_COUNT) {
 379         s->d1->timeout.read_timeouts = 1;
 380     }
 381
 382     dtls1_start_timer(s);
 383     return dtls1_retransmit_buffered_messages(s);
 384 }
 385
 386 static void get_current_time(struct timeval *t)
 387 {
 388 #if defined(_WIN32)
 389     SYSTEMTIME st;
 390     union {
 391         unsigned __int64 ul;
 392         FILETIME ft;
 393     } now;
 394
 395     GetSystemTime(&st);
 396     SystemTimeToFileTime(&st, &now.ft);
 397     /* re-bias to 1/1/1970 */
 398 # ifdef  __MINGW32__
 399     now.ul -= 116444736000000000ULL;
 400 # else
 401     /* *INDENT-OFF* */
 402     now.ul -= 116444736000000000UI64;
 403     /* *INDENT-ON* */
 404 # endif
 405     t->tv_sec = (long)(now.ul / 10000000);
 406     t->tv_usec = ((int)(now.ul % 10000000)) / 10;
 407 #elif defined(OPENSSL_SYS_VMS)
 408     struct timeb tb;
 409     ftime(&tb);
 410     t->tv_sec = (long)tb.time;
 411     t->tv_usec = (long)tb.millitm * 1000;
 412 #else
 413     gettimeofday(t, NULL);
 414 #endif
 415 }
 416
 417 #define LISTEN_SUCCESS              2
 418 #define LISTEN_SEND_VERIFY_REQUEST  1
 419
 420 #ifndef OPENSSL_NO_SOCK
 421 int DTLSv1_listen(SSL *s, BIO_ADDR *client)
 422 {
 423     int next, n, ret = 0, clearpkt = 0;
 424     unsigned char cookie[DTLS1_COOKIE_LENGTH];
 425     unsigned char seq[SEQ_NUM_SIZE];
 426     const unsigned char *data;
 427     unsigned char *buf;
 428     size_t fragoff, fraglen, msglen;
 429     unsigned int rectype, versmajor, msgseq, msgtype, clientvers, cookielen;
 430     BIO *rbio, *wbio;
 431     BUF_MEM *bufm;
 432     BIO_ADDR *tmpclient = NULL;
 433     PACKET pkt, msgpkt, msgpayload, session, cookiepkt;
 434
 435     if (s->handshake_func == NULL) {
 436         /* Not properly initialized yet */
 437         SSL_set_accept_state(s);
 438     }
 439
 440     /* Ensure there is no state left over from a previous invocation */
 441     if (!SSL_clear(s))
 442         return -1;
 443
 444     ERR_clear_error();
 445
 446     rbio = SSL_get_rbio(s);
 447     wbio = SSL_get_wbio(s);
 448
 449     if (!rbio || !wbio) {
 450         SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_BIO_NOT_SET);
 451         return -1;
 452     }
 453
 454     /*
 455      * We only peek at incoming ClientHello's until we're sure we are going to
 456      * to respond with a HelloVerifyRequest. If its a ClientHello with a valid
 457      * cookie then we leave it in the BIO for accept to handle.
 458      */
 459     BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL);
 460
 461     /*
 462      * Note: This check deliberately excludes DTLS1_BAD_VER because that version
 463      * requires the MAC to be calculated *including* the first ClientHello
 464      * (without the cookie). Since DTLSv1_listen is stateless that cannot be
 465      * supported. DTLS1_BAD_VER must use cookies in a stateful manner (e.g. via
 466      * SSL_accept)
 467      */
 468     if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00)) {
 469         SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNSUPPORTED_SSL_VERSION);
 470         return -1;
 471     }
 472
 473     if (s->init_buf == NULL) {
 474         if ((bufm = BUF_MEM_new()) == NULL) {
 475             SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE);
 476             return -1;
 477         }
 478
 479         if (!BUF_MEM_grow(bufm, SSL3_RT_MAX_PLAIN_LENGTH)) {
 480             BUF_MEM_free(bufm);
 481             SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE);
 482             return -1;
 483         }
 484         s->init_buf = bufm;
 485     }
 486     buf = (unsigned char *)s->init_buf->data;
 487
 488     do {
 489         /* Get a packet */
 490
 491         clear_sys_error();
 492         /*
 493          * Technically a ClientHello could be SSL3_RT_MAX_PLAIN_LENGTH
 494          * + DTLS1_RT_HEADER_LENGTH bytes long. Normally init_buf does not store
 495          * the record header as well, but we do here. We've set up init_buf to
 496          * be the standard size for simplicity. In practice we shouldn't ever
 497          * receive a ClientHello as long as this. If we do it will get dropped
 498          * in the record length check below.
 499          */
 500         n = BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
 501
 502         if (n <= 0) {
 503             if (BIO_should_retry(rbio)) {
 504                 /* Non-blocking IO */
 505                 goto end;
 506             }
 507             return -1;
 508         }
 509
 510         /* If we hit any problems we need to clear this packet from the BIO */
 511         clearpkt = 1;
 512
 513         if (!PACKET_buf_init(&pkt, buf, n)) {
 514             SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_INTERNAL_ERROR);
 515             return -1;
 516         }
 517
 518         /*
 519          * Parse the received record. If there are any problems with it we just
 520          * dump it - with no alert. RFC6347 says this "Unlike TLS, DTLS is
 521          * resilient in the face of invalid records (e.g., invalid formatting,
 522          * length, MAC, etc.).  In general, invalid records SHOULD be silently
 523          * discarded, thus preserving the association; however, an error MAY be
 524          * logged for diagnostic purposes."
 525          */
 526
 527         /* this packet contained a partial record, dump it */
 528         if (n < DTLS1_RT_HEADER_LENGTH) {
 529             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_RECORD_TOO_SMALL);
 530             goto end;
 531         }
 532
 533         if (s->msg_callback)
 534             s->msg_callback(0, 0, SSL3_RT_HEADER, buf,
 535                             DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg);
 536
 537         /* Get the record header */
 538         if (!PACKET_get_1(&pkt, &rectype)
 539             || !PACKET_get_1(&pkt, &versmajor)) {
 540             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
 541             goto end;
 542         }
 543
 544         if (rectype != SSL3_RT_HANDSHAKE) {
 545             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
 546             goto end;
 547         }
 548
 549         /*
 550          * Check record version number. We only check that the major version is
 551          * the same.
 552          */
 553         if (versmajor != DTLS1_VERSION_MAJOR) {
 554             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_BAD_PROTOCOL_VERSION_NUMBER);
 555             goto end;
 556         }
 557
 558         if (!PACKET_forward(&pkt, 1)
 559             /* Save the sequence number: 64 bits, with top 2 bytes = epoch */
 560             || !PACKET_copy_bytes(&pkt, seq, SEQ_NUM_SIZE)
 561             || !PACKET_get_length_prefixed_2(&pkt, &msgpkt)) {
 562             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
 563             goto end;
 564         }
 565         /*
 566          * We allow data remaining at the end of the packet because there could
 567          * be a second record (but we ignore it)
 568          */
 569
 570         /* This is an initial ClientHello so the epoch has to be 0 */
 571         if (seq[0] != 0 || seq[1] != 0) {
 572             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
 573             goto end;
 574         }
 575
 576         /* Get a pointer to the raw message for the later callback */
 577         data = PACKET_data(&msgpkt);
 578
 579         /* Finished processing the record header, now process the message */
 580         if (!PACKET_get_1(&msgpkt, &msgtype)
 581             || !PACKET_get_net_3_len(&msgpkt, &msglen)
 582             || !PACKET_get_net_2(&msgpkt, &msgseq)
 583             || !PACKET_get_net_3_len(&msgpkt, &fragoff)
 584             || !PACKET_get_net_3_len(&msgpkt, &fraglen)
 585             || !PACKET_get_sub_packet(&msgpkt, &msgpayload, fraglen)
 586             || PACKET_remaining(&msgpkt) != 0) {
 587             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
 588             goto end;
 589         }
 590
 591         if (msgtype != SSL3_MT_CLIENT_HELLO) {
 592             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
 593             goto end;
 594         }
 595
 596         /* Message sequence number can only be 0 or 1 */
 597         if (msgseq > 2) {
 598             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_INVALID_SEQUENCE_NUMBER);
 599             goto end;
 600         }
 601
 602         /*
 603          * We don't support fragment reassembly for ClientHellos whilst
 604          * listening because that would require server side state (which is
 605          * against the whole point of the ClientHello/HelloVerifyRequest
 606          * mechanism). Instead we only look at the first ClientHello fragment
 607          * and require that the cookie must be contained within it.
 608          */
 609         if (fragoff != 0 || fraglen > msglen) {
 610             /* Non initial ClientHello fragment (or bad fragment) */
 611             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_FRAGMENTED_CLIENT_HELLO);
 612             goto end;
 613         }
 614
 615         if (s->msg_callback)
 616             s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, data,
 617                             fraglen + DTLS1_HM_HEADER_LENGTH, s,
 618                             s->msg_callback_arg);
 619
 620         if (!PACKET_get_net_2(&msgpayload, &clientvers)) {
 621             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
 622             goto end;
 623         }
 624
 625         /*
 626          * Verify client version is supported
 627          */
 628         if (DTLS_VERSION_LT(clientvers, (unsigned int)s->method->version) &&
 629             s->method->version != DTLS_ANY_VERSION) {
 630             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_WRONG_VERSION_NUMBER);
 631             goto end;
 632         }
 633
 634         if (!PACKET_forward(&msgpayload, SSL3_RANDOM_SIZE)
 635             || !PACKET_get_length_prefixed_1(&msgpayload, &session)
 636             || !PACKET_get_length_prefixed_1(&msgpayload, &cookiepkt)) {
 637             /*
 638              * Could be malformed or the cookie does not fit within the initial
 639              * ClientHello fragment. Either way we can't handle it.
 640              */
 641             SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
 642             goto end;
 643         }
 644
 645         /*
 646          * Check if we have a cookie or not. If not we need to send a
 647          * HelloVerifyRequest.
 648          */
 649         if (PACKET_remaining(&cookiepkt) == 0) {
 650             next = LISTEN_SEND_VERIFY_REQUEST;
 651         } else {
 652             /*
 653              * We have a cookie, so lets check it.
 654              */
 655             if (s->ctx->app_verify_cookie_cb == NULL) {
 656                 SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_NO_VERIFY_COOKIE_CALLBACK);
 657                 /* This is fatal */
 658                 return -1;
 659             }
 660             if (s->ctx->app_verify_cookie_cb(s, PACKET_data(&cookiepkt),
 661                     (unsigned int)PACKET_remaining(&cookiepkt)) == 0) {
 662                 /*
 663                  * We treat invalid cookies in the same was as no cookie as
 664                  * per RFC6347
 665                  */
 666                 next = LISTEN_SEND_VERIFY_REQUEST;
 667             } else {
 668                 /* Cookie verification succeeded */
 669                 next = LISTEN_SUCCESS;
 670             }
 671         }
 672
 673         if (next == LISTEN_SEND_VERIFY_REQUEST) {
 674             WPACKET wpkt;
 675             unsigned int version;
 676             size_t wreclen;
 677
 678             /*
 679              * There was no cookie in the ClientHello so we need to send a
 680              * HelloVerifyRequest. If this fails we do not worry about trying
 681              * to resend, we just drop it.
 682              */
 683
 684             /*
 685              * Dump the read packet, we don't need it any more. Ignore return
 686              * value
 687              */
 688             BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL);
 689             BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
 690             BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL);
 691
 692             /* Generate the cookie */
 693             if (s->ctx->app_gen_cookie_cb == NULL ||
 694                 s->ctx->app_gen_cookie_cb(s, cookie, &cookielen) == 0 ||
 695                 cookielen > 255) {
 696                 SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_COOKIE_GEN_CALLBACK_FAILURE);
 697                 /* This is fatal */
 698                 return -1;
 699             }
 700
 701             /*
 702              * Special case: for hello verify request, client version 1.0 and we
 703              * haven't decided which version to use yet send back using version
 704              * 1.0 header: otherwise some clients will ignore it.
 705              */
 706             version = (s->method->version == DTLS_ANY_VERSION) ? DTLS1_VERSION
 707                                                                : s->version;
 708
 709             /* Construct the record and message headers */
 710             if (!WPACKET_init(&wpkt, s->init_buf)
 711                     || !WPACKET_put_bytes_u8(&wpkt, SSL3_RT_HANDSHAKE)
 712                     || !WPACKET_put_bytes_u16(&wpkt, version)
 713                        /*
 714                         * Record sequence number is always the same as in the
 715                         * received ClientHello
 716                         */
 717                     || !WPACKET_memcpy(&wpkt, seq, SEQ_NUM_SIZE)
 718                        /* End of record, start sub packet for message */
 719                     || !WPACKET_start_sub_packet_u16(&wpkt)
 720                        /* Message type */
 721                     || !WPACKET_put_bytes_u8(&wpkt,
 722                                              DTLS1_MT_HELLO_VERIFY_REQUEST)
 723                        /*
 724                         * Message length - doesn't follow normal TLS convention:
 725                         * the length isn't the last thing in the message header.
 726                         * We'll need to fill this in later when we know the
 727                         * length. Set it to zero for now
 728                         */
 729                     || !WPACKET_put_bytes_u24(&wpkt, 0)
 730                        /*
 731                         * Message sequence number is always 0 for a
 732                         * HelloVerifyRequest
 733                         */
 734                     || !WPACKET_put_bytes_u16(&wpkt, 0)
 735                        /*
 736                         * We never fragment a HelloVerifyRequest, so fragment
 737                         * offset is 0
 738                         */
 739                     || !WPACKET_put_bytes_u24(&wpkt, 0)
 740                        /*
 741                         * Fragment length is the same as message length, but
 742                         * this *is* the last thing in the message header so we
 743                         * can just start a sub-packet. No need to come back
 744                         * later for this one.
 745                         */
 746                     || !WPACKET_start_sub_packet_u24(&wpkt)
 747                        /* Create the actual HelloVerifyRequest body */
 748                     || !dtls_raw_hello_verify_request(&wpkt, cookie, cookielen)
 749                        /* Close message body */
 750                     || !WPACKET_close(&wpkt)
 751                        /* Close record body */
 752                     || !WPACKET_close(&wpkt)
 753                     || !WPACKET_get_total_written(&wpkt, &wreclen)
 754                     || !WPACKET_finish(&wpkt)) {
 755                 SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_INTERNAL_ERROR);
 756                 WPACKET_cleanup(&wpkt);
 757                 /* This is fatal */
 758                 return -1;
 759             }
 760
 761             /*
 762              * Fix up the message len in the message header. Its the same as the
 763              * fragment len which has been filled in by WPACKET, so just copy
 764              * that. Destination for the message len is after the record header
 765              * plus one byte for the message content type. The source is the
 766              * last 3 bytes of the message header
 767              */
 768             memcpy(&buf[DTLS1_RT_HEADER_LENGTH + 1],
 769                    &buf[DTLS1_RT_HEADER_LENGTH + DTLS1_HM_HEADER_LENGTH - 3],
 770                    3);
 771
 772             if (s->msg_callback)
 773                 s->msg_callback(1, 0, SSL3_RT_HEADER, buf,
 774                                 DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg);
 775
 776             if ((tmpclient = BIO_ADDR_new()) == NULL) {
 777                 SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE);
 778                 goto end;
 779             }
 780
 781             /*
 782              * This is unnecessary if rbio and wbio are one and the same - but
 783              * maybe they're not. We ignore errors here - some BIOs do not
 784              * support this.
 785              */
 786             if (BIO_dgram_get_peer(rbio, tmpclient) > 0) {
 787                 (void)BIO_dgram_set_peer(wbio, tmpclient);
 788             }
 789             BIO_ADDR_free(tmpclient);
 790             tmpclient = NULL;
 791
 792             /* TODO(size_t): convert this call */
 793             if (BIO_write(wbio, buf, wreclen) < (int)wreclen) {
 794                 if (BIO_should_retry(wbio)) {
 795                     /*
 796                      * Non-blocking IO...but we're stateless, so we're just
 797                      * going to drop this packet.
 798                      */
 799                     goto end;
 800                 }
 801                 return -1;
 802             }
 803
 804             if (BIO_flush(wbio) <= 0) {
 805                 if (BIO_should_retry(wbio)) {
 806                     /*
 807                      * Non-blocking IO...but we're stateless, so we're just
 808                      * going to drop this packet.
 809                      */
 810                     goto end;
 811                 }
 812                 return -1;
 813             }
 814         }
 815     } while (next != LISTEN_SUCCESS);
 816
 817     /*
 818      * Set expected sequence numbers to continue the handshake.
 819      */
 820     s->d1->handshake_read_seq = 1;
 821     s->d1->handshake_write_seq = 1;
 822     s->d1->next_handshake_write_seq = 1;
 823     DTLS_RECORD_LAYER_set_write_sequence(&s->rlayer, seq);
 824
 825     /*
 826      * We are doing cookie exchange, so make sure we set that option in the
 827      * SSL object
 828      */
 829     SSL_set_options(s, SSL_OP_COOKIE_EXCHANGE);
 830
 831     /*
 832      * Tell the state machine that we've done the initial hello verify
 833      * exchange
 834      */
 835     ossl_statem_set_hello_verify_done(s);
 836
 837     /*
 838      * Some BIOs may not support this. If we fail we clear the client address
 839      */
 840     if (BIO_dgram_get_peer(rbio, client) <= 0)
 841         BIO_ADDR_clear(client);
 842
 843     ret = 1;
 844     clearpkt = 0;
 845  end:
 846     BIO_ADDR_free(tmpclient);
 847     BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL);
 848     if (clearpkt) {
 849         /* Dump this packet. Ignore return value */
 850         BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
 851     }
 852     return ret;
 853 }
 854 #endif
 855
 856 static int dtls1_handshake_write(SSL *s)
 857 {
 858     return dtls1_do_write(s, SSL3_RT_HANDSHAKE);
 859 }
 860
 861 int dtls1_shutdown(SSL *s)
 862 {
 863     int ret;
 864 #ifndef OPENSSL_NO_SCTP
 865     BIO *wbio;
 866
 867     wbio = SSL_get_wbio(s);
 868     if (wbio != NULL && BIO_dgram_is_sctp(wbio) &&
 869         !(s->shutdown & SSL_SENT_SHUTDOWN)) {
 870         ret = BIO_dgram_sctp_wait_for_dry(wbio);
 871         if (ret < 0)
 872             return -1;
 873
 874         if (ret == 0)
 875             BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 1,
 876                      NULL);
 877     }
 878 #endif
 879     ret = ssl3_shutdown(s);
 880 #ifndef OPENSSL_NO_SCTP
 881     BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 0, NULL);
 882 #endif
 883     return ret;
 884 }
 885
 886 int dtls1_query_mtu(SSL *s)
 887 {
 888     if (s->d1->link_mtu) {
 889         s->d1->mtu =
 890             s->d1->link_mtu - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
 891         s->d1->link_mtu = 0;
 892     }
 893
 894     /* AHA!  Figure out the MTU, and stick to the right size */
 895     if (s->d1->mtu < dtls1_min_mtu(s)) {
 896         if (!(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) {
 897             s->d1->mtu =
 898                 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
 899
 900             /*
 901              * I've seen the kernel return bogus numbers when it doesn't know
 902              * (initial write), so just make sure we have a reasonable number
 903              */
 904             if (s->d1->mtu < dtls1_min_mtu(s)) {
 905                 /* Set to min mtu */
 906                 s->d1->mtu = dtls1_min_mtu(s);
 907                 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU,
 908                          (long)s->d1->mtu, NULL);
 909             }
 910         } else
 911             return 0;
 912     }
 913     return 1;
 914 }
 915
 916 static size_t dtls1_link_min_mtu(void)
 917 {
 918     return (g_probable_mtu[(sizeof(g_probable_mtu) /
 919                             sizeof(g_probable_mtu[0])) - 1]);
 920 }
 921
 922 size_t dtls1_min_mtu(SSL *s)
 923 {
 924     return dtls1_link_min_mtu() - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
 925 }
 926
 927 size_t DTLS_get_data_mtu(const SSL *s)
 928 {
 929     size_t mac_overhead, int_overhead, blocksize, ext_overhead;
 930     const SSL_CIPHER *ciph = SSL_get_current_cipher(s);
 931     size_t mtu = s->d1->mtu;
 932
 933     if (ciph == NULL)
 934         return 0;
 935
 936     if (!ssl_cipher_get_overhead(ciph, &mac_overhead, &int_overhead,
 937                                  &blocksize, &ext_overhead))
 938         return 0;
 939
 940     if (SSL_USE_ETM(s))
 941         ext_overhead += mac_overhead;
 942     else
 943         int_overhead += mac_overhead;
 944
 945     /* Subtract external overhead (e.g. IV/nonce, separate MAC) */
 946     if (ext_overhead + DTLS1_RT_HEADER_LENGTH >= mtu)
 947         return 0;
 948     mtu -= ext_overhead + DTLS1_RT_HEADER_LENGTH;
 949
 950     /* Round encrypted payload down to cipher block size (for CBC etc.)
 951      * No check for overflow since 'mtu % blocksize' cannot exceed mtu. */
 952     if (blocksize)
 953         mtu -= (mtu % blocksize);
 954
 955     /* Subtract internal overhead (e.g. CBC padding len byte) */
 956     if (int_overhead >= mtu)
 957         return 0;
 958     mtu -= int_overhead;
 959
 960     return mtu;
 961 }