ssl/statem/statem.c

   1 /* ssl/statem/statem.c */
   2 /*
   3  * Written by Matt Caswell for the OpenSSL project.
   4  */
   5 /* ====================================================================
   6  * Copyright (c) 1998-2015 The OpenSSL Project.  All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  *
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  *
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in
  17  *    the documentation and/or other materials provided with the
  18  *    distribution.
  19  *
  20  * 3. All advertising materials mentioning features or use of this
  21  *    software must display the following acknowledgment:
  22  *    "This product includes software developed by the OpenSSL Project
  23  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  24  *
  25  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  26  *    endorse or promote products derived from this software without
  27  *    prior written permission. For written permission, please contact
  28  *    openssl-core@openssl.org.
  29  *
  30  * 5. Products derived from this software may not be called "OpenSSL"
  31  *    nor may "OpenSSL" appear in their names without prior written
  32  *    permission of the OpenSSL Project.
  33  *
  34  * 6. Redistributions of any form whatsoever must retain the following
  35  *    acknowledgment:
  36  *    "This product includes software developed by the OpenSSL Project
  37  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  38  *
  39  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  40  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  41  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  42  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  43  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  44  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  45  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  46  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  47  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  48  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  49  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  50  * OF THE POSSIBILITY OF SUCH DAMAGE.
  51  * ====================================================================
  52  *
  53  * This product includes cryptographic software written by Eric Young
  54  * (eay@cryptsoft.com).  This product includes software written by Tim
  55  * Hudson (tjh@cryptsoft.com).
  56  *
  57  */
  58
  59 #include <openssl/rand.h>
  60 #include "../ssl_locl.h"
  61 #include "statem_locl.h"
  62
  63 /*
  64  * This file implements the SSL/TLS/DTLS state machines.
  65  *
  66  * There are two primary state machines:
  67  *
  68  * 1) Message flow state machine
  69  * 2) Handshake state machine
  70  *
  71  * The Message flow state machine controls the reading and sending of messages
  72  * including handling of non-blocking IO events, flushing of the underlying
  73  * write BIO, handling unexpected messages, etc. It is itself broken into two
  74  * separate sub-state machines which control reading and writing respectively.
  75  *
  76  * The Handshake state machine keeps track of the current SSL/TLS handshake
  77  * state. Transitions of the handshake state are the result of events that
  78  * occur within the Message flow state machine.
  79  *
  80  * Overall it looks like this:
  81  *
  82  * ---------------------------------------------            -------------------
  83  * |                                           |            |                 |
  84  * | Message flow state machine                |            |                 |
  85  * |                                           |            |                 |
  86  * | -------------------- -------------------- | Transition | Handshake state |
  87  * | | MSG_FLOW_READING | | MSG_FLOW_WRITING | | Event      | machine         |
  88  * | | sub-state        | | sub-state        | |----------->|                 |
  89  * | | machine for      | | machine for      | |            |                 |
  90  * | | reading messages | | writing messages | |            |                 |
  91  * | -------------------- -------------------- |            |                 |
  92  * |                                           |            |                 |
  93  * ---------------------------------------------            -------------------
  94  *
  95  */
  96
  97 /* Sub state machine return values */
  98 enum SUB_STATE_RETURN {
  99     /* Something bad happened or NBIO */
 100     SUB_STATE_ERROR,
 101     /* Sub state finished go to the next sub state */
 102     SUB_STATE_FINISHED,
 103     /* Sub state finished and handshake was completed */
 104     SUB_STATE_END_HANDSHAKE
 105 };
 106
 107 static int state_machine(SSL *s, int server);
 108 static void init_read_state_machine(SSL *s);
 109 static enum SUB_STATE_RETURN read_state_machine(SSL *s);
 110 static void init_write_state_machine(SSL *s);
 111 static enum SUB_STATE_RETURN write_state_machine(SSL *s);
 112
 113 OSSL_HANDSHAKE_STATE SSL_state(const SSL *ssl)
 114 {
 115     return ssl->statem.hand_state;
 116 }
 117
 118 void SSL_set_state(SSL *ssl, OSSL_HANDSHAKE_STATE state)
 119 {
 120     /*
 121      * This function seems like a really bad idea. Should we remove it
 122      * completely?
 123      */
 124     ssl->statem.hand_state = state;
 125 }
 126
 127 int SSL_in_init(SSL *s)
 128 {
 129     return s->statem.in_init;
 130 }
 131
 132 int SSL_is_init_finished(SSL *s)
 133 {
 134     return !(s->statem.in_init) && (s->statem.hand_state == TLS_ST_OK);
 135 }
 136
 137 int SSL_in_before(SSL *s)
 138 {
 139     /*
 140      * Historically being "in before" meant before anything had happened. In the
 141      * current code though we remain in the "before" state for a while after we
 142      * have started the handshake process (e.g. as a server waiting for the
 143      * first message to arrive). There "in before" is taken to mean "in before"
 144      * and not started any handshake process yet.
 145      */
 146     return (s->statem.hand_state == TLS_ST_BEFORE)
 147         && (s->statem.state == MSG_FLOW_UNINITED);
 148 }
 149
 150 /*
 151  * Clear the state machine state and reset back to MSG_FLOW_UNINITED
 152  */
 153 void statem_clear(SSL *s)
 154 {
 155     s->statem.state = MSG_FLOW_UNINITED;
 156     s->statem.hand_state = TLS_ST_BEFORE;
 157     s->statem.in_init = 1;
 158 }
 159
 160 /*
 161  * Set the state machine up ready for a renegotiation handshake
 162  */
 163 void statem_set_renegotiate(SSL *s)
 164 {
 165     s->statem.state = MSG_FLOW_RENEGOTIATE;
 166     s->statem.in_init = 1;
 167 }
 168
 169 /*
 170  * Put the state machine into an error state. This is a permanent error for
 171  * the current connection.
 172  */
 173 void statem_set_error(SSL *s)
 174 {
 175     s->statem.state = MSG_FLOW_ERROR;
 176 }
 177
 178 /*
 179  * Discover whether the current connection is in the error state.
 180  *
 181  * Valid return values are:
 182  *   1: Yes
 183  *   0: No
 184  */
 185 int statem_in_error(const SSL *s)
 186 {
 187     if (s->statem.state == MSG_FLOW_ERROR)
 188         return 1;
 189
 190     return 0;
 191 }
 192
 193 void statem_set_in_init(SSL *s, int init)
 194 {
 195     s->statem.in_init = init;
 196 }
 197
 198 int statem_connect(SSL *s) {
 199     return state_machine(s, 0);
 200 }
 201
 202 int statem_accept(SSL *s)
 203 {
 204     return state_machine(s, 1);
 205 }
 206
 207 /*
 208  * The main message flow state machine. We start in the MSG_FLOW_UNINITED or
 209  * MSG_FLOW_RENEGOTIATE state and finish in MSG_FLOW_FINISHED. Valid states and
 210  * transitions are as follows:
 211  *
 212  * MSG_FLOW_UNINITED     MSG_FLOW_RENEGOTIATE
 213  *        |                       |
 214  *        +-----------------------+
 215  *        v
 216  * MSG_FLOW_WRITING <---> MSG_FLOW_READING
 217  *        |
 218  *        V
 219  * MSG_FLOW_FINISHED
 220  *        |
 221  *        V
 222  *    [SUCCESS]
 223  *
 224  * We may exit at any point due to an error or NBIO event. If an NBIO event
 225  * occurs then we restart at the point we left off when we are recalled.
 226  * MSG_FLOW_WRITING and MSG_FLOW_READING have sub-state machines associated with them.
 227  *
 228  * In addition to the above there is also the MSG_FLOW_ERROR state. We can move
 229  * into that state at any point in the event that an irrecoverable error occurs.
 230  *
 231  * Valid return values are:
 232  *   1: Success
 233  * <=0: NBIO or error
 234  */
 235 static int state_machine(SSL *s, int server) {
 236     BUF_MEM *buf = NULL;
 237     unsigned long Time = (unsigned long)time(NULL);
 238     void (*cb) (const SSL *ssl, int type, int val) = NULL;
 239     STATEM *st = &s->statem;
 240     int ret = -1;
 241     int ssret;
 242
 243     if (st->state == MSG_FLOW_ERROR) {
 244         /* Shouldn't have been called if we're already in the error state */
 245         return -1;
 246     }
 247
 248     RAND_add(&Time, sizeof(Time), 0);
 249     ERR_clear_error();
 250     clear_sys_error();
 251
 252     if (s->info_callback != NULL)
 253         cb = s->info_callback;
 254     else if (s->ctx->info_callback != NULL)
 255         cb = s->ctx->info_callback;
 256
 257     s->in_handshake++;
 258     if (!SSL_in_init(s) || SSL_in_before(s)) {
 259         if (!SSL_clear(s))
 260             return -1;
 261     }
 262
 263 #ifndef OPENSSL_NO_SCTP
 264     if (SSL_IS_DTLS(s)) {
 265         /*
 266          * Notify SCTP BIO socket to enter handshake mode and prevent stream
 267          * identifier other than 0. Will be ignored if no SCTP is used.
 268          */
 269         BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
 270                  s->in_handshake, NULL);
 271     }
 272 #endif
 273
 274 #ifndef OPENSSL_NO_HEARTBEATS
 275     /*
 276      * If we're awaiting a HeartbeatResponse, pretend we already got and
 277      * don't await it anymore, because Heartbeats don't make sense during
 278      * handshakes anyway.
 279      */
 280     if (s->tlsext_hb_pending) {
 281         if (SSL_IS_DTLS(s))
 282             dtls1_stop_timer(s);
 283         s->tlsext_hb_pending = 0;
 284         s->tlsext_hb_seq++;
 285     }
 286 #endif
 287
 288     /* Initialise state machine */
 289
 290     if (st->state == MSG_FLOW_RENEGOTIATE) {
 291         s->renegotiate = 1;
 292         if (!server)
 293             s->ctx->stats.sess_connect_renegotiate++;
 294     }
 295
 296     if (st->state == MSG_FLOW_UNINITED || st->state == MSG_FLOW_RENEGOTIATE) {
 297         if (st->state == MSG_FLOW_UNINITED) {
 298             st->hand_state = TLS_ST_BEFORE;
 299         }
 300
 301         s->server = server;
 302         if (cb != NULL)
 303             cb(s, SSL_CB_HANDSHAKE_START, 1);
 304
 305         if (SSL_IS_DTLS(s)) {
 306             if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00) &&
 307                     (server
 308                     || (s->version & 0xff00) != (DTLS1_BAD_VER & 0xff00))) {
 309                 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
 310                 goto end;
 311             }
 312         } else {
 313             if ((s->version >> 8) != SSL3_VERSION_MAJOR
 314                     && s->version != TLS_ANY_VERSION) {
 315                 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
 316                 goto end;
 317             }
 318         }
 319
 320         if (!SSL_IS_DTLS(s)) {
 321             if (s->version != TLS_ANY_VERSION &&
 322                     !ssl_security(s, SSL_SECOP_VERSION, 0, s->version, NULL)) {
 323                 SSLerr(SSL_F_STATE_MACHINE, SSL_R_VERSION_TOO_LOW);
 324                 goto end;
 325             }
 326         }
 327
 328         if (s->init_buf == NULL) {
 329             if ((buf = BUF_MEM_new()) == NULL) {
 330                 goto end;
 331             }
 332             if (!BUF_MEM_grow(buf, SSL3_RT_MAX_PLAIN_LENGTH)) {
 333                 goto end;
 334             }
 335             s->init_buf = buf;
 336             buf = NULL;
 337         }
 338
 339         if (!ssl3_setup_buffers(s)) {
 340             goto end;
 341         }
 342         s->init_num = 0;
 343
 344         /*
 345          * Should have been reset by tls_process_finished, too.
 346          */
 347         s->s3->change_cipher_spec = 0;
 348
 349         if (!server || st->state != MSG_FLOW_RENEGOTIATE) {
 350                 /*
 351                  * Ok, we now need to push on a buffering BIO ...but not with
 352                  * SCTP
 353                  */
 354 #ifndef OPENSSL_NO_SCTP
 355                 if (!SSL_IS_DTLS(s) || !BIO_dgram_is_sctp(SSL_get_wbio(s)))
 356 #endif
 357                     if (!ssl_init_wbio_buffer(s, server ? 1 : 0)) {
 358                         goto end;
 359                     }
 360
 361             ssl3_init_finished_mac(s);
 362         }
 363
 364         if (server) {
 365             if (st->state != MSG_FLOW_RENEGOTIATE) {
 366                 s->ctx->stats.sess_accept++;
 367             } else if (!s->s3->send_connection_binding &&
 368                        !(s->options &
 369                          SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION)) {
 370                 /*
 371                  * Server attempting to renegotiate with client that doesn't
 372                  * support secure renegotiation.
 373                  */
 374                 SSLerr(SSL_F_STATE_MACHINE,
 375                        SSL_R_UNSAFE_LEGACY_RENEGOTIATION_DISABLED);
 376                 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_HANDSHAKE_FAILURE);
 377                 statem_set_error(s);
 378                 goto end;
 379             } else {
 380                 /*
 381                  * st->state == MSG_FLOW_RENEGOTIATE, we will just send a
 382                  * HelloRequest
 383                  */
 384                 s->ctx->stats.sess_accept_renegotiate++;
 385             }
 386         } else {
 387             s->ctx->stats.sess_connect++;
 388
 389             /* mark client_random uninitialized */
 390             memset(s->s3->client_random, 0, sizeof(s->s3->client_random));
 391             s->hit = 0;
 392
 393             s->s3->tmp.cert_request = 0;
 394
 395             if (SSL_IS_DTLS(s)) {
 396                 st->use_timer = 1;
 397             }
 398         }
 399
 400         st->state = MSG_FLOW_WRITING;
 401         init_write_state_machine(s);
 402         st->read_state_first_init = 1;
 403     }
 404
 405     while(st->state != MSG_FLOW_FINISHED) {
 406         if(st->state == MSG_FLOW_READING) {
 407             ssret = read_state_machine(s);
 408             if (ssret == SUB_STATE_FINISHED) {
 409                 st->state = MSG_FLOW_WRITING;
 410                 init_write_state_machine(s);
 411             } else {
 412                 /* NBIO or error */
 413                 goto end;
 414             }
 415         } else if (st->state == MSG_FLOW_WRITING) {
 416             ssret = write_state_machine(s);
 417             if (ssret == SUB_STATE_FINISHED) {
 418                 st->state = MSG_FLOW_READING;
 419                 init_read_state_machine(s);
 420             } else if (ssret == SUB_STATE_END_HANDSHAKE) {
 421                 st->state = MSG_FLOW_FINISHED;
 422             } else {
 423                 /* NBIO or error */
 424                 goto end;
 425             }
 426         } else {
 427             /* Error */
 428             statem_set_error(s);
 429             goto end;
 430         }
 431     }
 432
 433     st->state = MSG_FLOW_UNINITED;
 434     ret = 1;
 435
 436  end:
 437     s->in_handshake--;
 438
 439 #ifndef OPENSSL_NO_SCTP
 440     if (SSL_IS_DTLS(s)) {
 441         /*
 442          * Notify SCTP BIO socket to leave handshake mode and allow stream
 443          * identifier other than 0. Will be ignored if no SCTP is used.
 444          */
 445         BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
 446                  s->in_handshake, NULL);
 447     }
 448 #endif
 449
 450     BUF_MEM_free(buf);
 451     if (cb != NULL) {
 452         if (server)
 453             cb(s, SSL_CB_ACCEPT_EXIT, ret);
 454         else
 455             cb(s, SSL_CB_CONNECT_EXIT, ret);
 456     }
 457     return ret;
 458 }
 459
 460 /*
 461  * Initialise the MSG_FLOW_READING sub-state machine
 462  */
 463 static void init_read_state_machine(SSL *s)
 464 {
 465     STATEM *st = &s->statem;
 466
 467     st->read_state = READ_STATE_HEADER;
 468 }
 469
 470 /*
 471  * This function implements the sub-state machine when the message flow is in
 472  * MSG_FLOW_READING. The valid sub-states and transitions are:
 473  *
 474  * READ_STATE_HEADER <--+<-------------+
 475  *        |             |              |
 476  *        v             |              |
 477  * READ_STATE_BODY -----+-->READ_STATE_POST_PROCESS
 478  *        |                            |
 479  *        +----------------------------+
 480  *        v
 481  * [SUB_STATE_FINISHED]
 482  *
 483  * READ_STATE_HEADER has the responsibility for reading in the message header
 484  * and transitioning the state of the handshake state machine.
 485  *
 486  * READ_STATE_BODY reads in the rest of the message and then subsequently
 487  * processes it.
 488  *
 489  * READ_STATE_POST_PROCESS is an optional step that may occur if some post
 490  * processing activity performed on the message may block.
 491  *
 492  * Any of the above states could result in an NBIO event occuring in which case
 493  * control returns to the calling application. When this function is recalled we
 494  * will resume in the same state where we left off.
 495  */
 496 static enum SUB_STATE_RETURN read_state_machine(SSL *s) {
 497     STATEM *st = &s->statem;
 498     int ret, mt;
 499     unsigned long len;
 500     int (*transition)(SSL *s, int mt);
 501     PACKET pkt;
 502     enum MSG_PROCESS_RETURN (*process_message)(SSL *s, PACKET *pkt);
 503     enum WORK_STATE (*post_process_message)(SSL *s, enum WORK_STATE wst);
 504     unsigned long (*max_message_size)(SSL *s);
 505     void (*cb) (const SSL *ssl, int type, int val) = NULL;
 506
 507     if (s->info_callback != NULL)
 508         cb = s->info_callback;
 509     else if (s->ctx->info_callback != NULL)
 510         cb = s->ctx->info_callback;
 511
 512     if(s->server) {
 513         transition = server_read_transition;
 514         process_message = server_process_message;
 515         max_message_size = server_max_message_size;
 516         post_process_message = server_post_process_message;
 517     } else {
 518         transition = client_read_transition;
 519         process_message = client_process_message;
 520         max_message_size = client_max_message_size;
 521         post_process_message = client_post_process_message;
 522     }
 523
 524     if (st->read_state_first_init) {
 525         s->first_packet = 1;
 526         st->read_state_first_init = 0;
 527     }
 528
 529     while(1) {
 530         switch(st->read_state) {
 531         case READ_STATE_HEADER:
 532             s->init_num = 0;
 533             /* Get the state the peer wants to move to */
 534             if (SSL_IS_DTLS(s)) {
 535                 /*
 536                  * In DTLS we get the whole message in one go - header and body
 537                  */
 538                 ret = dtls_get_message(s, &mt, &len);
 539             } else {
 540                 ret = tls_get_message_header(s, &mt);
 541             }
 542
 543             if (ret == 0) {
 544                 /* Could be non-blocking IO */
 545                 return SUB_STATE_ERROR;
 546             }
 547
 548             if (cb != NULL) {
 549                 /* Notify callback of an impending state change */
 550                 if (s->server)
 551                     cb(s, SSL_CB_ACCEPT_LOOP, 1);
 552                 else
 553                     cb(s, SSL_CB_CONNECT_LOOP, 1);
 554             }
 555             /*
 556              * Validate that we are allowed to move to the new state and move
 557              * to that state if so
 558              */
 559             if(!transition(s, mt)) {
 560                 ssl3_send_alert(s, SSL3_AL_FATAL, SSL3_AD_UNEXPECTED_MESSAGE);
 561                 SSLerr(SSL_F_READ_STATE_MACHINE, SSL_R_UNEXPECTED_MESSAGE);
 562                 return SUB_STATE_ERROR;
 563             }
 564
 565             if (s->s3->tmp.message_size > max_message_size(s)) {
 566                 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
 567                 SSLerr(SSL_F_READ_STATE_MACHINE, SSL_R_EXCESSIVE_MESSAGE_SIZE);
 568                 return SUB_STATE_ERROR;
 569             }
 570
 571             st->read_state = READ_STATE_BODY;
 572             /* Fall through */
 573
 574         case READ_STATE_BODY:
 575             if (!SSL_IS_DTLS(s)) {
 576                 /* We already got this above for DTLS */
 577                 ret = tls_get_message_body(s, &len);
 578                 if (ret == 0) {
 579                     /* Could be non-blocking IO */
 580                     return SUB_STATE_ERROR;
 581                 }
 582             }
 583
 584             s->first_packet = 0;
 585             if (!PACKET_buf_init(&pkt, s->init_msg, len)) {
 586                 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
 587                 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
 588                 return SUB_STATE_ERROR;
 589             }
 590             ret = process_message(s, &pkt);
 591             if (ret == MSG_PROCESS_ERROR) {
 592                 return SUB_STATE_ERROR;
 593             }
 594
 595             if (ret == MSG_PROCESS_FINISHED_READING) {
 596                 if (SSL_IS_DTLS(s)) {
 597                     dtls1_stop_timer(s);
 598                 }
 599                 return SUB_STATE_FINISHED;
 600             }
 601
 602             if (ret == MSG_PROCESS_CONTINUE_PROCESSING) {
 603                 st->read_state = READ_STATE_POST_PROCESS;
 604                 st->read_state_work = WORK_MORE_A;
 605             } else {
 606                 st->read_state = READ_STATE_HEADER;
 607             }
 608             break;
 609
 610         case READ_STATE_POST_PROCESS:
 611             st->read_state_work = post_process_message(s, st->read_state_work);
 612             switch(st->read_state_work) {
 613             default:
 614                 return SUB_STATE_ERROR;
 615
 616             case WORK_FINISHED_CONTINUE:
 617                 st->read_state = READ_STATE_HEADER;
 618                 break;
 619
 620             case WORK_FINISHED_STOP:
 621                 if (SSL_IS_DTLS(s)) {
 622                     dtls1_stop_timer(s);
 623                 }
 624                 return SUB_STATE_FINISHED;
 625             }
 626             break;
 627
 628         default:
 629             /* Shouldn't happen */
 630             ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
 631             SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
 632             statem_set_error(s);
 633             return SUB_STATE_ERROR;
 634         }
 635     }
 636 }
 637
 638 /*
 639  * Send a previously constructed message to the peer.
 640  */
 641 static int statem_do_write(SSL *s)
 642 {
 643     STATEM *st = &s->statem;
 644
 645     if (st->hand_state == TLS_ST_CW_CHANGE
 646             || st->hand_state == TLS_ST_SW_CHANGE) {
 647         if (SSL_IS_DTLS(s))
 648             return dtls1_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
 649         else
 650             return ssl3_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
 651     } else {
 652         return ssl_do_write(s);
 653     }
 654 }
 655
 656 /*
 657  * Initialise the MSG_FLOW_WRITING sub-state machine
 658  */
 659 static void init_write_state_machine(SSL *s)
 660 {
 661     STATEM *st = &s->statem;
 662
 663     st->write_state = WRITE_STATE_TRANSITION;
 664 }
 665
 666 /*
 667  * This function implements the sub-state machine when the message flow is in
 668  * MSG_FLOW_WRITING. The valid sub-states and transitions are:
 669  *
 670  * +-> WRITE_STATE_TRANSITION ------> [SUB_STATE_FINISHED]
 671  * |             |
 672  * |             v
 673  * |      WRITE_STATE_PRE_WORK -----> [SUB_STATE_END_HANDSHAKE]
 674  * |             |
 675  * |             v
 676  * |       WRITE_STATE_SEND
 677  * |             |
 678  * |             v
 679  * |     WRITE_STATE_POST_WORK
 680  * |             |
 681  * +-------------+
 682  *
 683  * WRITE_STATE_TRANSITION transitions the state of the handshake state machine
 684
 685  * WRITE_STATE_PRE_WORK performs any work necessary to prepare the later
 686  * sending of the message. This could result in an NBIO event occuring in
 687  * which case control returns to the calling application. When this function
 688  * is recalled we will resume in the same state where we left off.
 689  *
 690  * WRITE_STATE_SEND sends the message and performs any work to be done after
 691  * sending.
 692  *
 693  * WRITE_STATE_POST_WORK performs any work necessary after the sending of the
 694  * message has been completed. As for WRITE_STATE_PRE_WORK this could also
 695  * result in an NBIO event.
 696  */
 697 static enum SUB_STATE_RETURN write_state_machine(SSL *s)
 698 {
 699     STATEM *st = &s->statem;
 700     int ret;
 701     enum WRITE_TRAN (*transition)(SSL *s);
 702     enum WORK_STATE (*pre_work)(SSL *s, enum WORK_STATE wst);
 703     enum WORK_STATE (*post_work)(SSL *s, enum WORK_STATE wst);
 704     int (*construct_message)(SSL *s);
 705     void (*cb) (const SSL *ssl, int type, int val) = NULL;
 706
 707     if (s->info_callback != NULL)
 708         cb = s->info_callback;
 709     else if (s->ctx->info_callback != NULL)
 710         cb = s->ctx->info_callback;
 711
 712     if(s->server) {
 713         transition = server_write_transition;
 714         pre_work = server_pre_work;
 715         post_work = server_post_work;
 716         construct_message = server_construct_message;
 717     } else {
 718         transition = client_write_transition;
 719         pre_work = client_pre_work;
 720         post_work = client_post_work;
 721         construct_message = client_construct_message;
 722     }
 723
 724     while(1) {
 725         switch(st->write_state) {
 726         case WRITE_STATE_TRANSITION:
 727             if (cb != NULL) {
 728                 /* Notify callback of an impending state change */
 729                 if (s->server)
 730                     cb(s, SSL_CB_ACCEPT_LOOP, 1);
 731                 else
 732                     cb(s, SSL_CB_CONNECT_LOOP, 1);
 733             }
 734             switch(transition(s)) {
 735             case WRITE_TRAN_CONTINUE:
 736                 st->write_state = WRITE_STATE_PRE_WORK;
 737                 st->write_state_work = WORK_MORE_A;
 738                 break;
 739
 740             case WRITE_TRAN_FINISHED:
 741                 return SUB_STATE_FINISHED;
 742                 break;
 743
 744             default:
 745                 return SUB_STATE_ERROR;
 746             }
 747             break;
 748
 749         case WRITE_STATE_PRE_WORK:
 750             switch(st->write_state_work = pre_work(s, st->write_state_work)) {
 751             default:
 752                 return SUB_STATE_ERROR;
 753
 754             case WORK_FINISHED_CONTINUE:
 755                 st->write_state = WRITE_STATE_SEND;
 756                 break;
 757
 758             case WORK_FINISHED_STOP:
 759                 return SUB_STATE_END_HANDSHAKE;
 760             }
 761             if(construct_message(s) == 0)
 762                 return SUB_STATE_ERROR;
 763
 764             /* Fall through */
 765
 766         case WRITE_STATE_SEND:
 767             if (SSL_IS_DTLS(s) && st->use_timer) {
 768                 dtls1_start_timer(s);
 769             }
 770             ret = statem_do_write(s);
 771             if (ret <= 0) {
 772                 return SUB_STATE_ERROR;
 773             }
 774             st->write_state = WRITE_STATE_POST_WORK;
 775             st->write_state_work = WORK_MORE_A;
 776             /* Fall through */
 777
 778         case WRITE_STATE_POST_WORK:
 779             switch(st->write_state_work = post_work(s, st->write_state_work)) {
 780             default:
 781                 return SUB_STATE_ERROR;
 782
 783             case WORK_FINISHED_CONTINUE:
 784                 st->write_state = WRITE_STATE_TRANSITION;
 785                 break;
 786
 787             case WORK_FINISHED_STOP:
 788                 return SUB_STATE_END_HANDSHAKE;
 789             }
 790             break;
 791
 792         default:
 793             return SUB_STATE_ERROR;
 794         }
 795     }
 796 }
 797
 798 /*
 799  * Flush the write BIO
 800  */
 801 int statem_flush(SSL *s)
 802 {
 803     s->rwstate = SSL_WRITING;
 804     if (BIO_flush(s->wbio) <= 0) {
 805         return 0;
 806     }
 807     s->rwstate = SSL_NOTHING;
 808
 809     return 1;
 810 }
 811
 812 /*
 813  * Called by the record layer to determine whether application data is
 814  * allowed to be sent in the current handshake state or not.
 815  *
 816  * Return values are:
 817  *   1: Yes (application data allowed)
 818  *   0: No (application data not allowed)
 819  */
 820 int statem_app_data_allowed(SSL *s)
 821 {
 822     STATEM *st = &s->statem;
 823
 824     if (st->state == MSG_FLOW_UNINITED || st->state == MSG_FLOW_RENEGOTIATE)
 825         return 0;
 826
 827     if (!s->s3->in_read_app_data || (s->s3->total_renegotiations == 0))
 828         return 0;
 829
 830     if (s->server) {
 831         /*
 832          * If we're a server and we haven't got as far as writing our
 833          * ServerHello yet then we allow app data
 834          */
 835         if (st->hand_state == TLS_ST_BEFORE
 836                 || st->hand_state == TLS_ST_SR_CLNT_HELLO)
 837             return 1;
 838     } else {
 839         /*
 840          * If we're a client and we haven't read the ServerHello yet then we
 841          * allow app data
 842          */
 843         if (st->hand_state == TLS_ST_CW_CLNT_HELLO)
 844             return 1;
 845     }
 846
 847     return 0;
 848 }
 849
 850 #ifndef OPENSSL_NO_SCTP
 851 /*
 852  * Set flag used by SCTP to determine whether we are in the read sock state
 853  */
 854 void statem_set_sctp_read_sock(SSL *s, int read_sock)
 855 {
 856     s->statem.in_sctp_read_sock = read_sock;
 857 }
 858
 859 /*
 860  * Called by the record layer to determine whether we are in the read sock
 861  * state or not.
 862  *
 863  * Return values are:
 864  *   1: Yes (we are in the read sock state)
 865  *   0: No (we are not in the read sock state)
 866  */
 867 int statem_in_sctp_read_sock(SSL *s)
 868 {
 869     return s->statem.in_sctp_read_sock;
 870 }
 871 #endif