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