ssl/statem/statem.c

   1 /*
   2  * Copyright 2015-2016 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 <openssl/rand.h>
  11 #include "../ssl_locl.h"
  12 #include "statem_locl.h"
  13
  14 /*
  15  * This file implements the SSL/TLS/DTLS state machines.
  16  *
  17  * There are two primary state machines:
  18  *
  19  * 1) Message flow state machine
  20  * 2) Handshake state machine
  21  *
  22  * The Message flow state machine controls the reading and sending of messages
  23  * including handling of non-blocking IO events, flushing of the underlying
  24  * write BIO, handling unexpected messages, etc. It is itself broken into two
  25  * separate sub-state machines which control reading and writing respectively.
  26  *
  27  * The Handshake state machine keeps track of the current SSL/TLS handshake
  28  * state. Transitions of the handshake state are the result of events that
  29  * occur within the Message flow state machine.
  30  *
  31  * Overall it looks like this:
  32  *
  33  * ---------------------------------------------            -------------------
  34  * |                                           |            |                 |
  35  * | Message flow state machine                |            |                 |
  36  * |                                           |            |                 |
  37  * | -------------------- -------------------- | Transition | Handshake state |
  38  * | | MSG_FLOW_READING | | MSG_FLOW_WRITING | | Event      | machine         |
  39  * | | sub-state        | | sub-state        | |----------->|                 |
  40  * | | machine for      | | machine for      | |            |                 |
  41  * | | reading messages | | writing messages | |            |                 |
  42  * | -------------------- -------------------- |            |                 |
  43  * |                                           |            |                 |
  44  * ---------------------------------------------            -------------------
  45  *
  46  */
  47
  48 /* Sub state machine return values */
  49 typedef enum  {
  50     /* Something bad happened or NBIO */
  51     SUB_STATE_ERROR,
  52     /* Sub state finished go to the next sub state */
  53     SUB_STATE_FINISHED,
  54     /* Sub state finished and handshake was completed */
  55     SUB_STATE_END_HANDSHAKE
  56 } SUB_STATE_RETURN;
  57
  58 static int state_machine(SSL *s, int server);
  59 static void init_read_state_machine(SSL *s);
  60 static SUB_STATE_RETURN read_state_machine(SSL *s);
  61 static void init_write_state_machine(SSL *s);
  62 static SUB_STATE_RETURN write_state_machine(SSL *s);
  63
  64 OSSL_HANDSHAKE_STATE SSL_get_state(const SSL *ssl)
  65 {
  66     return ssl->statem.hand_state;
  67 }
  68
  69 int SSL_in_init(SSL *s)
  70 {
  71     return s->statem.in_init;
  72 }
  73
  74 int SSL_is_init_finished(SSL *s)
  75 {
  76     return !(s->statem.in_init) && (s->statem.hand_state == TLS_ST_OK);
  77 }
  78
  79 int SSL_in_before(SSL *s)
  80 {
  81     /*
  82      * Historically being "in before" meant before anything had happened. In the
  83      * current code though we remain in the "before" state for a while after we
  84      * have started the handshake process (e.g. as a server waiting for the
  85      * first message to arrive). There "in before" is taken to mean "in before"
  86      * and not started any handshake process yet.
  87      */
  88     return (s->statem.hand_state == TLS_ST_BEFORE)
  89         && (s->statem.state == MSG_FLOW_UNINITED);
  90 }
  91
  92 /*
  93  * Clear the state machine state and reset back to MSG_FLOW_UNINITED
  94  */
  95 void ossl_statem_clear(SSL *s)
  96 {
  97     s->statem.state = MSG_FLOW_UNINITED;
  98     s->statem.hand_state = TLS_ST_BEFORE;
  99     s->statem.in_init = 1;
 100     s->statem.no_cert_verify = 0;
 101 }
 102
 103 /*
 104  * Set the state machine up ready for a renegotiation handshake
 105  */
 106 void ossl_statem_set_renegotiate(SSL *s)
 107 {
 108     s->statem.state = MSG_FLOW_RENEGOTIATE;
 109     s->statem.in_init = 1;
 110 }
 111
 112 /*
 113  * Put the state machine into an error state. This is a permanent error for
 114  * the current connection.
 115  */
 116 void ossl_statem_set_error(SSL *s)
 117 {
 118     s->statem.state = MSG_FLOW_ERROR;
 119 }
 120
 121 /*
 122  * Discover whether the current connection is in the error state.
 123  *
 124  * Valid return values are:
 125  *   1: Yes
 126  *   0: No
 127  */
 128 int ossl_statem_in_error(const SSL *s)
 129 {
 130     if (s->statem.state == MSG_FLOW_ERROR)
 131         return 1;
 132
 133     return 0;
 134 }
 135
 136 void ossl_statem_set_in_init(SSL *s, int init)
 137 {
 138     s->statem.in_init = init;
 139 }
 140
 141 int ossl_statem_get_in_handshake(SSL *s)
 142 {
 143     return s->statem.in_handshake;
 144 }
 145
 146 void ossl_statem_set_in_handshake(SSL *s, int inhand)
 147 {
 148     if (inhand)
 149         s->statem.in_handshake++;
 150     else
 151         s->statem.in_handshake--;
 152 }
 153
 154 void ossl_statem_set_hello_verify_done(SSL *s)
 155 {
 156     s->statem.state = MSG_FLOW_UNINITED;
 157     s->statem.in_init = 1;
 158     /*
 159      * This will get reset (briefly) back to TLS_ST_BEFORE when we enter
 160      * state_machine() because |state| is MSG_FLOW_UNINITED, but until then any
 161      * calls to SSL_in_before() will return false. Also calls to
 162      * SSL_state_string() and SSL_state_string_long() will return something
 163      * sensible.
 164      */
 165     s->statem.hand_state = TLS_ST_SR_CLNT_HELLO;
 166 }
 167
 168 int ossl_statem_connect(SSL *s) {
 169     return state_machine(s, 0);
 170 }
 171
 172 int ossl_statem_accept(SSL *s)
 173 {
 174     return state_machine(s, 1);
 175 }
 176
 177 static void (*get_callback(SSL *s))(const SSL *, int, int)
 178 {
 179     if (s->info_callback != NULL)
 180         return s->info_callback;
 181     else if (s->ctx->info_callback != NULL)
 182         return s->ctx->info_callback;
 183
 184     return NULL;
 185 }
 186
 187 /*
 188  * The main message flow state machine. We start in the MSG_FLOW_UNINITED or
 189  * MSG_FLOW_RENEGOTIATE state and finish in MSG_FLOW_FINISHED. Valid states and
 190  * transitions are as follows:
 191  *
 192  * MSG_FLOW_UNINITED     MSG_FLOW_RENEGOTIATE
 193  *        |                       |
 194  *        +-----------------------+
 195  *        v
 196  * MSG_FLOW_WRITING <---> MSG_FLOW_READING
 197  *        |
 198  *        V
 199  * MSG_FLOW_FINISHED
 200  *        |
 201  *        V
 202  *    [SUCCESS]
 203  *
 204  * We may exit at any point due to an error or NBIO event. If an NBIO event
 205  * occurs then we restart at the point we left off when we are recalled.
 206  * MSG_FLOW_WRITING and MSG_FLOW_READING have sub-state machines associated with them.
 207  *
 208  * In addition to the above there is also the MSG_FLOW_ERROR state. We can move
 209  * into that state at any point in the event that an irrecoverable error occurs.
 210  *
 211  * Valid return values are:
 212  *   1: Success
 213  * <=0: NBIO or error
 214  */
 215 static int state_machine(SSL *s, int server)
 216 {
 217     BUF_MEM *buf = NULL;
 218     unsigned long Time = (unsigned long)time(NULL);
 219     void (*cb) (const SSL *ssl, int type, int val) = NULL;
 220     OSSL_STATEM *st = &s->statem;
 221     int ret = -1;
 222     int ssret;
 223
 224     if (st->state == MSG_FLOW_ERROR) {
 225         /* Shouldn't have been called if we're already in the error state */
 226         return -1;
 227     }
 228
 229     RAND_add(&Time, sizeof(Time), 0);
 230     ERR_clear_error();
 231     clear_sys_error();
 232
 233     cb = get_callback(s);
 234
 235     st->in_handshake++;
 236     if (!SSL_in_init(s) || SSL_in_before(s)) {
 237         if (!SSL_clear(s))
 238             return -1;
 239     }
 240
 241 #ifndef OPENSSL_NO_SCTP
 242     if (SSL_IS_DTLS(s)) {
 243         /*
 244          * Notify SCTP BIO socket to enter handshake mode and prevent stream
 245          * identifier other than 0. Will be ignored if no SCTP is used.
 246          */
 247         BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
 248                  st->in_handshake, NULL);
 249     }
 250 #endif
 251
 252 #ifndef OPENSSL_NO_HEARTBEATS
 253     /*
 254      * If we're awaiting a HeartbeatResponse, pretend we already got and
 255      * don't await it anymore, because Heartbeats don't make sense during
 256      * handshakes anyway.
 257      */
 258     if (s->tlsext_hb_pending) {
 259         if (SSL_IS_DTLS(s))
 260             dtls1_stop_timer(s);
 261         s->tlsext_hb_pending = 0;
 262         s->tlsext_hb_seq++;
 263     }
 264 #endif
 265
 266     /* Initialise state machine */
 267
 268     if (st->state == MSG_FLOW_RENEGOTIATE) {
 269         s->renegotiate = 1;
 270         if (!server)
 271             s->ctx->stats.sess_connect_renegotiate++;
 272     }
 273
 274     if (st->state == MSG_FLOW_UNINITED || st->state == MSG_FLOW_RENEGOTIATE) {
 275         if (st->state == MSG_FLOW_UNINITED) {
 276             st->hand_state = TLS_ST_BEFORE;
 277         }
 278
 279         s->server = server;
 280         if (cb != NULL)
 281             cb(s, SSL_CB_HANDSHAKE_START, 1);
 282
 283         if (SSL_IS_DTLS(s)) {
 284             if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00) &&
 285                     (server
 286                     || (s->version & 0xff00) != (DTLS1_BAD_VER & 0xff00))) {
 287                 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
 288                 goto end;
 289             }
 290         } else {
 291             if ((s->version >> 8) != SSL3_VERSION_MAJOR) {
 292                 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
 293                 goto end;
 294             }
 295         }
 296
 297         if (!ssl_security(s, SSL_SECOP_VERSION, 0, s->version, NULL)) {
 298             SSLerr(SSL_F_STATE_MACHINE, SSL_R_VERSION_TOO_LOW);
 299             goto end;
 300         }
 301
 302         if (s->init_buf == NULL) {
 303             if ((buf = BUF_MEM_new()) == NULL) {
 304                 goto end;
 305             }
 306             if (!BUF_MEM_grow(buf, SSL3_RT_MAX_PLAIN_LENGTH)) {
 307                 goto end;
 308             }
 309             s->init_buf = buf;
 310             buf = NULL;
 311         }
 312
 313         if (!ssl3_setup_buffers(s)) {
 314             goto end;
 315         }
 316         s->init_num = 0;
 317
 318         /*
 319          * Should have been reset by tls_process_finished, too.
 320          */
 321         s->s3->change_cipher_spec = 0;
 322
 323
 324         /*
 325          * Ok, we now need to push on a buffering BIO ...but not with
 326          * SCTP
 327          */
 328 #ifndef OPENSSL_NO_SCTP
 329         if (!SSL_IS_DTLS(s) || !BIO_dgram_is_sctp(SSL_get_wbio(s)))
 330 #endif
 331             if (!ssl_init_wbio_buffer(s)) {
 332                 goto end;
 333             }
 334
 335         if (!server || st->state != MSG_FLOW_RENEGOTIATE)
 336             ssl3_init_finished_mac(s);
 337
 338         if (server) {
 339             if (st->state != MSG_FLOW_RENEGOTIATE) {
 340                 s->ctx->stats.sess_accept++;
 341             } else if (!s->s3->send_connection_binding &&
 342                        !(s->options &
 343                          SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION)) {
 344                 /*
 345                  * Server attempting to renegotiate with client that doesn't
 346                  * support secure renegotiation.
 347                  */
 348                 SSLerr(SSL_F_STATE_MACHINE,
 349                        SSL_R_UNSAFE_LEGACY_RENEGOTIATION_DISABLED);
 350                 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_HANDSHAKE_FAILURE);
 351                 ossl_statem_set_error(s);
 352                 goto end;
 353             } else {
 354                 /*
 355                  * st->state == MSG_FLOW_RENEGOTIATE, we will just send a
 356                  * HelloRequest
 357                  */
 358                 s->ctx->stats.sess_accept_renegotiate++;
 359             }
 360         } else {
 361             s->ctx->stats.sess_connect++;
 362
 363             /* mark client_random uninitialized */
 364             memset(s->s3->client_random, 0, sizeof(s->s3->client_random));
 365             s->hit = 0;
 366
 367             s->s3->tmp.cert_request = 0;
 368
 369             if (SSL_IS_DTLS(s)) {
 370                 st->use_timer = 1;
 371             }
 372         }
 373
 374         st->state = MSG_FLOW_WRITING;
 375         init_write_state_machine(s);
 376         st->read_state_first_init = 1;
 377     }
 378
 379     while(st->state != MSG_FLOW_FINISHED) {
 380         if(st->state == MSG_FLOW_READING) {
 381             ssret = read_state_machine(s);
 382             if (ssret == SUB_STATE_FINISHED) {
 383                 st->state = MSG_FLOW_WRITING;
 384                 init_write_state_machine(s);
 385             } else {
 386                 /* NBIO or error */
 387                 goto end;
 388             }
 389         } else if (st->state == MSG_FLOW_WRITING) {
 390             ssret = write_state_machine(s);
 391             if (ssret == SUB_STATE_FINISHED) {
 392                 st->state = MSG_FLOW_READING;
 393                 init_read_state_machine(s);
 394             } else if (ssret == SUB_STATE_END_HANDSHAKE) {
 395                 st->state = MSG_FLOW_FINISHED;
 396             } else {
 397                 /* NBIO or error */
 398                 goto end;
 399             }
 400         } else {
 401             /* Error */
 402             ossl_statem_set_error(s);
 403             goto end;
 404         }
 405     }
 406
 407     st->state = MSG_FLOW_UNINITED;
 408     ret = 1;
 409
 410  end:
 411     st->in_handshake--;
 412
 413 #ifndef OPENSSL_NO_SCTP
 414     if (SSL_IS_DTLS(s)) {
 415         /*
 416          * Notify SCTP BIO socket to leave handshake mode and allow stream
 417          * identifier other than 0. Will be ignored if no SCTP is used.
 418          */
 419         BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
 420                  st->in_handshake, NULL);
 421     }
 422 #endif
 423
 424     BUF_MEM_free(buf);
 425     if (cb != NULL) {
 426         if (server)
 427             cb(s, SSL_CB_ACCEPT_EXIT, ret);
 428         else
 429             cb(s, SSL_CB_CONNECT_EXIT, ret);
 430     }
 431     return ret;
 432 }
 433
 434 /*
 435  * Initialise the MSG_FLOW_READING sub-state machine
 436  */
 437 static void init_read_state_machine(SSL *s)
 438 {
 439     OSSL_STATEM *st = &s->statem;
 440
 441     st->read_state = READ_STATE_HEADER;
 442 }
 443
 444 /*
 445  * This function implements the sub-state machine when the message flow is in
 446  * MSG_FLOW_READING. The valid sub-states and transitions are:
 447  *
 448  * READ_STATE_HEADER <--+<-------------+
 449  *        |             |              |
 450  *        v             |              |
 451  * READ_STATE_BODY -----+-->READ_STATE_POST_PROCESS
 452  *        |                            |
 453  *        +----------------------------+
 454  *        v
 455  * [SUB_STATE_FINISHED]
 456  *
 457  * READ_STATE_HEADER has the responsibility for reading in the message header
 458  * and transitioning the state of the handshake state machine.
 459  *
 460  * READ_STATE_BODY reads in the rest of the message and then subsequently
 461  * processes it.
 462  *
 463  * READ_STATE_POST_PROCESS is an optional step that may occur if some post
 464  * processing activity performed on the message may block.
 465  *
 466  * Any of the above states could result in an NBIO event occurring in which case
 467  * control returns to the calling application. When this function is recalled we
 468  * will resume in the same state where we left off.
 469  */
 470 static SUB_STATE_RETURN read_state_machine(SSL *s) {
 471     OSSL_STATEM *st = &s->statem;
 472     int ret, mt;
 473     unsigned long len = 0;
 474     int (*transition)(SSL *s, int mt);
 475     PACKET pkt;
 476     MSG_PROCESS_RETURN (*process_message)(SSL *s, PACKET *pkt);
 477     WORK_STATE (*post_process_message)(SSL *s, WORK_STATE wst);
 478     unsigned long (*max_message_size)(SSL *s);
 479     void (*cb) (const SSL *ssl, int type, int val) = NULL;
 480
 481     cb = get_callback(s);
 482
 483     if(s->server) {
 484         transition = ossl_statem_server_read_transition;
 485         process_message = ossl_statem_server_process_message;
 486         max_message_size = ossl_statem_server_max_message_size;
 487         post_process_message = ossl_statem_server_post_process_message;
 488     } else {
 489         transition = ossl_statem_client_read_transition;
 490         process_message = ossl_statem_client_process_message;
 491         max_message_size = ossl_statem_client_max_message_size;
 492         post_process_message = ossl_statem_client_post_process_message;
 493     }
 494
 495     if (st->read_state_first_init) {
 496         s->first_packet = 1;
 497         st->read_state_first_init = 0;
 498     }
 499
 500     while(1) {
 501         switch(st->read_state) {
 502         case READ_STATE_HEADER:
 503             s->init_num = 0;
 504             /* Get the state the peer wants to move to */
 505             if (SSL_IS_DTLS(s)) {
 506                 /*
 507                  * In DTLS we get the whole message in one go - header and body
 508                  */
 509                 ret = dtls_get_message(s, &mt, &len);
 510             } else {
 511                 ret = tls_get_message_header(s, &mt);
 512             }
 513
 514             if (ret == 0) {
 515                 /* Could be non-blocking IO */
 516                 return SUB_STATE_ERROR;
 517             }
 518
 519             if (cb != NULL) {
 520                 /* Notify callback of an impending state change */
 521                 if (s->server)
 522                     cb(s, SSL_CB_ACCEPT_LOOP, 1);
 523                 else
 524                     cb(s, SSL_CB_CONNECT_LOOP, 1);
 525             }
 526             /*
 527              * Validate that we are allowed to move to the new state and move
 528              * to that state if so
 529              */
 530             if(!transition(s, mt)) {
 531                 ssl3_send_alert(s, SSL3_AL_FATAL, SSL3_AD_UNEXPECTED_MESSAGE);
 532                 SSLerr(SSL_F_READ_STATE_MACHINE, SSL_R_UNEXPECTED_MESSAGE);
 533                 return SUB_STATE_ERROR;
 534             }
 535
 536             if (s->s3->tmp.message_size > max_message_size(s)) {
 537                 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
 538                 SSLerr(SSL_F_READ_STATE_MACHINE, SSL_R_EXCESSIVE_MESSAGE_SIZE);
 539                 return SUB_STATE_ERROR;
 540             }
 541
 542             st->read_state = READ_STATE_BODY;
 543             /* Fall through */
 544
 545         case READ_STATE_BODY:
 546             if (!SSL_IS_DTLS(s)) {
 547                 /* We already got this above for DTLS */
 548                 ret = tls_get_message_body(s, &len);
 549                 if (ret == 0) {
 550                     /* Could be non-blocking IO */
 551                     return SUB_STATE_ERROR;
 552                 }
 553             }
 554
 555             s->first_packet = 0;
 556             if (!PACKET_buf_init(&pkt, s->init_msg, len)) {
 557                 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
 558                 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
 559                 return SUB_STATE_ERROR;
 560             }
 561             ret = process_message(s, &pkt);
 562             if (ret == MSG_PROCESS_ERROR) {
 563                 return SUB_STATE_ERROR;
 564             }
 565
 566             if (ret == MSG_PROCESS_FINISHED_READING) {
 567                 if (SSL_IS_DTLS(s)) {
 568                     dtls1_stop_timer(s);
 569                 }
 570                 return SUB_STATE_FINISHED;
 571             }
 572
 573             if (ret == MSG_PROCESS_CONTINUE_PROCESSING) {
 574                 st->read_state = READ_STATE_POST_PROCESS;
 575                 st->read_state_work = WORK_MORE_A;
 576             } else {
 577                 st->read_state = READ_STATE_HEADER;
 578             }
 579             break;
 580
 581         case READ_STATE_POST_PROCESS:
 582             st->read_state_work = post_process_message(s, st->read_state_work);
 583             switch(st->read_state_work) {
 584             default:
 585                 return SUB_STATE_ERROR;
 586
 587             case WORK_FINISHED_CONTINUE:
 588                 st->read_state = READ_STATE_HEADER;
 589                 break;
 590
 591             case WORK_FINISHED_STOP:
 592                 if (SSL_IS_DTLS(s)) {
 593                     dtls1_stop_timer(s);
 594                 }
 595                 return SUB_STATE_FINISHED;
 596             }
 597             break;
 598
 599         default:
 600             /* Shouldn't happen */
 601             ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
 602             SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
 603             ossl_statem_set_error(s);
 604             return SUB_STATE_ERROR;
 605         }
 606     }
 607 }
 608
 609 /*
 610  * Send a previously constructed message to the peer.
 611  */
 612 static int statem_do_write(SSL *s)
 613 {
 614     OSSL_STATEM *st = &s->statem;
 615
 616     if (st->hand_state == TLS_ST_CW_CHANGE
 617             || st->hand_state == TLS_ST_SW_CHANGE) {
 618         if (SSL_IS_DTLS(s))
 619             return dtls1_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
 620         else
 621             return ssl3_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
 622     } else {
 623         return ssl_do_write(s);
 624     }
 625 }
 626
 627 /*
 628  * Initialise the MSG_FLOW_WRITING sub-state machine
 629  */
 630 static void init_write_state_machine(SSL *s)
 631 {
 632     OSSL_STATEM *st = &s->statem;
 633
 634     st->write_state = WRITE_STATE_TRANSITION;
 635 }
 636
 637 /*
 638  * This function implements the sub-state machine when the message flow is in
 639  * MSG_FLOW_WRITING. The valid sub-states and transitions are:
 640  *
 641  * +-> WRITE_STATE_TRANSITION ------> [SUB_STATE_FINISHED]
 642  * |             |
 643  * |             v
 644  * |      WRITE_STATE_PRE_WORK -----> [SUB_STATE_END_HANDSHAKE]
 645  * |             |
 646  * |             v
 647  * |       WRITE_STATE_SEND
 648  * |             |
 649  * |             v
 650  * |     WRITE_STATE_POST_WORK
 651  * |             |
 652  * +-------------+
 653  *
 654  * WRITE_STATE_TRANSITION transitions the state of the handshake state machine
 655
 656  * WRITE_STATE_PRE_WORK performs any work necessary to prepare the later
 657  * sending of the message. This could result in an NBIO event occurring in
 658  * which case control returns to the calling application. When this function
 659  * is recalled we will resume in the same state where we left off.
 660  *
 661  * WRITE_STATE_SEND sends the message and performs any work to be done after
 662  * sending.
 663  *
 664  * WRITE_STATE_POST_WORK performs any work necessary after the sending of the
 665  * message has been completed. As for WRITE_STATE_PRE_WORK this could also
 666  * result in an NBIO event.
 667  */
 668 static SUB_STATE_RETURN write_state_machine(SSL *s)
 669 {
 670     OSSL_STATEM *st = &s->statem;
 671     int ret;
 672     WRITE_TRAN (*transition)(SSL *s);
 673     WORK_STATE (*pre_work)(SSL *s, WORK_STATE wst);
 674     WORK_STATE (*post_work)(SSL *s, WORK_STATE wst);
 675     int (*construct_message)(SSL *s);
 676     void (*cb) (const SSL *ssl, int type, int val) = NULL;
 677
 678     cb = get_callback(s);
 679
 680     if(s->server) {
 681         transition = ossl_statem_server_write_transition;
 682         pre_work = ossl_statem_server_pre_work;
 683         post_work = ossl_statem_server_post_work;
 684         construct_message = ossl_statem_server_construct_message;
 685     } else {
 686         transition = ossl_statem_client_write_transition;
 687         pre_work = ossl_statem_client_pre_work;
 688         post_work = ossl_statem_client_post_work;
 689         construct_message = ossl_statem_client_construct_message;
 690     }
 691
 692     while(1) {
 693         switch(st->write_state) {
 694         case WRITE_STATE_TRANSITION:
 695             if (cb != NULL) {
 696                 /* Notify callback of an impending state change */
 697                 if (s->server)
 698                     cb(s, SSL_CB_ACCEPT_LOOP, 1);
 699                 else
 700                     cb(s, SSL_CB_CONNECT_LOOP, 1);
 701             }
 702             switch(transition(s)) {
 703             case WRITE_TRAN_CONTINUE:
 704                 st->write_state = WRITE_STATE_PRE_WORK;
 705                 st->write_state_work = WORK_MORE_A;
 706                 break;
 707
 708             case WRITE_TRAN_FINISHED:
 709                 return SUB_STATE_FINISHED;
 710                 break;
 711
 712             default:
 713                 return SUB_STATE_ERROR;
 714             }
 715             break;
 716
 717         case WRITE_STATE_PRE_WORK:
 718             switch(st->write_state_work = pre_work(s, st->write_state_work)) {
 719             default:
 720                 return SUB_STATE_ERROR;
 721
 722             case WORK_FINISHED_CONTINUE:
 723                 st->write_state = WRITE_STATE_SEND;
 724                 break;
 725
 726             case WORK_FINISHED_STOP:
 727                 return SUB_STATE_END_HANDSHAKE;
 728             }
 729             if(construct_message(s) == 0)
 730                 return SUB_STATE_ERROR;
 731
 732             /* Fall through */
 733
 734         case WRITE_STATE_SEND:
 735             if (SSL_IS_DTLS(s) && st->use_timer) {
 736                 dtls1_start_timer(s);
 737             }
 738             ret = statem_do_write(s);
 739             if (ret <= 0) {
 740                 return SUB_STATE_ERROR;
 741             }
 742             st->write_state = WRITE_STATE_POST_WORK;
 743             st->write_state_work = WORK_MORE_A;
 744             /* Fall through */
 745
 746         case WRITE_STATE_POST_WORK:
 747             switch(st->write_state_work = post_work(s, st->write_state_work)) {
 748             default:
 749                 return SUB_STATE_ERROR;
 750
 751             case WORK_FINISHED_CONTINUE:
 752                 st->write_state = WRITE_STATE_TRANSITION;
 753                 break;
 754
 755             case WORK_FINISHED_STOP:
 756                 return SUB_STATE_END_HANDSHAKE;
 757             }
 758             break;
 759
 760         default:
 761             return SUB_STATE_ERROR;
 762         }
 763     }
 764 }
 765
 766 /*
 767  * Flush the write BIO
 768  */
 769 int statem_flush(SSL *s)
 770 {
 771     s->rwstate = SSL_WRITING;
 772     if (BIO_flush(s->wbio) <= 0) {
 773         return 0;
 774     }
 775     s->rwstate = SSL_NOTHING;
 776
 777     return 1;
 778 }
 779
 780 /*
 781  * Called by the record layer to determine whether application data is
 782  * allowed to be sent in the current handshake state or not.
 783  *
 784  * Return values are:
 785  *   1: Yes (application data allowed)
 786  *   0: No (application data not allowed)
 787  */
 788 int ossl_statem_app_data_allowed(SSL *s)
 789 {
 790     OSSL_STATEM *st = &s->statem;
 791
 792     if (st->state == MSG_FLOW_UNINITED || st->state == MSG_FLOW_RENEGOTIATE)
 793         return 0;
 794
 795     if (!s->s3->in_read_app_data || (s->s3->total_renegotiations == 0))
 796         return 0;
 797
 798     if (s->server) {
 799         /*
 800          * If we're a server and we haven't got as far as writing our
 801          * ServerHello yet then we allow app data
 802          */
 803         if (st->hand_state == TLS_ST_BEFORE
 804                 || st->hand_state == TLS_ST_SR_CLNT_HELLO)
 805             return 1;
 806     } else {
 807         /*
 808          * If we're a client and we haven't read the ServerHello yet then we
 809          * allow app data
 810          */
 811         if (st->hand_state == TLS_ST_CW_CLNT_HELLO)
 812             return 1;
 813     }
 814
 815     return 0;
 816 }
 817
 818 #ifndef OPENSSL_NO_SCTP
 819 /*
 820  * Set flag used by SCTP to determine whether we are in the read sock state
 821  */
 822 void ossl_statem_set_sctp_read_sock(SSL *s, int read_sock)
 823 {
 824     s->statem.in_sctp_read_sock = read_sock;
 825 }
 826
 827 /*
 828  * Called by the record layer to determine whether we are in the read sock
 829  * state or not.
 830  *
 831  * Return values are:
 832  *   1: Yes (we are in the read sock state)
 833  *   0: No (we are not in the read sock state)
 834  */
 835 int ossl_statem_in_sctp_read_sock(SSL *s)
 836 {
 837     return s->statem.in_sctp_read_sock;
 838 }
 839 #endif