2 * Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.
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
10 #include <openssl/rand.h>
11 #include "../ssl_locl.h"
12 #include "statem_locl.h"
15 * This file implements the SSL/TLS/DTLS state machines.
17 * There are two primary state machines:
19 * 1) Message flow state machine
20 * 2) Handshake state machine
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.
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.
31 * Overall it looks like this:
33 * --------------------------------------------- -------------------
35 * | Message flow state machine | | |
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 * | -------------------- -------------------- | | |
44 * --------------------------------------------- -------------------
48 /* Sub state machine return values */
50 /* Something bad happened or NBIO */
52 /* Sub state finished go to the next sub state */
54 /* Sub state finished and handshake was completed */
55 SUB_STATE_END_HANDSHAKE
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);
64 OSSL_HANDSHAKE_STATE SSL_get_state(const SSL *ssl)
66 return ssl->statem.hand_state;
69 int SSL_in_init(SSL *s)
71 return s->statem.in_init;
74 int SSL_is_init_finished(SSL *s)
76 return !(s->statem.in_init) && (s->statem.hand_state == TLS_ST_OK);
79 int SSL_in_before(SSL *s)
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.
88 return (s->statem.hand_state == TLS_ST_BEFORE)
89 && (s->statem.state == MSG_FLOW_UNINITED);
93 * Clear the state machine state and reset back to MSG_FLOW_UNINITED
95 void ossl_statem_clear(SSL *s)
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;
104 * Set the state machine up ready for a renegotiation handshake
106 void ossl_statem_set_renegotiate(SSL *s)
108 s->statem.state = MSG_FLOW_RENEGOTIATE;
109 s->statem.in_init = 1;
113 * Put the state machine into an error state. This is a permanent error for
114 * the current connection.
116 void ossl_statem_set_error(SSL *s)
118 s->statem.state = MSG_FLOW_ERROR;
122 * Discover whether the current connection is in the error state.
124 * Valid return values are:
128 int ossl_statem_in_error(const SSL *s)
130 if (s->statem.state == MSG_FLOW_ERROR)
136 void ossl_statem_set_in_init(SSL *s, int init)
138 s->statem.in_init = init;
141 int ossl_statem_get_in_handshake(SSL *s)
143 return s->statem.in_handshake;
146 void ossl_statem_set_in_handshake(SSL *s, int inhand)
149 s->statem.in_handshake++;
151 s->statem.in_handshake--;
154 void ossl_statem_set_hello_verify_done(SSL *s)
156 s->statem.state = MSG_FLOW_UNINITED;
157 s->statem.in_init = 1;
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
165 s->statem.hand_state = TLS_ST_SR_CLNT_HELLO;
168 int ossl_statem_connect(SSL *s) {
169 return state_machine(s, 0);
172 int ossl_statem_accept(SSL *s)
174 return state_machine(s, 1);
177 static void (*get_callback(SSL *s))(const SSL *, int, int)
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;
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:
192 * MSG_FLOW_UNINITED MSG_FLOW_RENEGOTIATE
194 * +-----------------------+
196 * MSG_FLOW_WRITING <---> MSG_FLOW_READING
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.
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.
211 * Valid return values are:
215 static int state_machine(SSL *s, int server)
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;
224 if (st->state == MSG_FLOW_ERROR) {
225 /* Shouldn't have been called if we're already in the error state */
229 RAND_add(&Time, sizeof(Time), 0);
233 cb = get_callback(s);
236 if (!SSL_in_init(s) || SSL_in_before(s)) {
241 #ifndef OPENSSL_NO_SCTP
242 if (SSL_IS_DTLS(s)) {
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.
247 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
248 st->in_handshake, NULL);
252 #ifndef OPENSSL_NO_HEARTBEATS
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
258 if (s->tlsext_hb_pending) {
261 s->tlsext_hb_pending = 0;
266 /* Initialise state machine */
268 if (st->state == MSG_FLOW_RENEGOTIATE) {
271 s->ctx->stats.sess_connect_renegotiate++;
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;
281 cb(s, SSL_CB_HANDSHAKE_START, 1);
283 if (SSL_IS_DTLS(s)) {
284 if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00) &&
286 || (s->version & 0xff00) != (DTLS1_BAD_VER & 0xff00))) {
287 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
291 if ((s->version >> 8) != SSL3_VERSION_MAJOR) {
292 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
297 if (!ssl_security(s, SSL_SECOP_VERSION, 0, s->version, NULL)) {
298 SSLerr(SSL_F_STATE_MACHINE, SSL_R_VERSION_TOO_LOW);
302 if (s->init_buf == NULL) {
303 if ((buf = BUF_MEM_new()) == NULL) {
306 if (!BUF_MEM_grow(buf, SSL3_RT_MAX_PLAIN_LENGTH)) {
313 if (!ssl3_setup_buffers(s)) {
319 * Should have been reset by tls_process_finished, too.
321 s->s3->change_cipher_spec = 0;
325 * Ok, we now need to push on a buffering BIO ...but not with
328 #ifndef OPENSSL_NO_SCTP
329 if (!SSL_IS_DTLS(s) || !BIO_dgram_is_sctp(SSL_get_wbio(s)))
331 if (!ssl_init_wbio_buffer(s)) {
335 if (!server || st->state != MSG_FLOW_RENEGOTIATE)
336 ssl3_init_finished_mac(s);
339 if (st->state != MSG_FLOW_RENEGOTIATE) {
340 s->ctx->stats.sess_accept++;
341 } else if (!s->s3->send_connection_binding &&
343 SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION)) {
345 * Server attempting to renegotiate with client that doesn't
346 * support secure renegotiation.
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);
355 * st->state == MSG_FLOW_RENEGOTIATE, we will just send a
358 s->ctx->stats.sess_accept_renegotiate++;
361 s->ctx->stats.sess_connect++;
363 /* mark client_random uninitialized */
364 memset(s->s3->client_random, 0, sizeof(s->s3->client_random));
367 s->s3->tmp.cert_request = 0;
369 if (SSL_IS_DTLS(s)) {
374 st->state = MSG_FLOW_WRITING;
375 init_write_state_machine(s);
376 st->read_state_first_init = 1;
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);
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;
402 ossl_statem_set_error(s);
407 st->state = MSG_FLOW_UNINITED;
413 #ifndef OPENSSL_NO_SCTP
414 if (SSL_IS_DTLS(s)) {
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.
419 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
420 st->in_handshake, NULL);
427 cb(s, SSL_CB_ACCEPT_EXIT, ret);
429 cb(s, SSL_CB_CONNECT_EXIT, ret);
435 * Initialise the MSG_FLOW_READING sub-state machine
437 static void init_read_state_machine(SSL *s)
439 OSSL_STATEM *st = &s->statem;
441 st->read_state = READ_STATE_HEADER;
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:
448 * READ_STATE_HEADER <--+<-------------+
451 * READ_STATE_BODY -----+-->READ_STATE_POST_PROCESS
453 * +----------------------------+
455 * [SUB_STATE_FINISHED]
457 * READ_STATE_HEADER has the responsibility for reading in the message header
458 * and transitioning the state of the handshake state machine.
460 * READ_STATE_BODY reads in the rest of the message and then subsequently
463 * READ_STATE_POST_PROCESS is an optional step that may occur if some post
464 * processing activity performed on the message may block.
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.
470 static SUB_STATE_RETURN read_state_machine(SSL *s) {
471 OSSL_STATEM *st = &s->statem;
473 unsigned long len = 0;
474 int (*transition)(SSL *s, int mt);
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;
481 cb = get_callback(s);
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;
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;
495 if (st->read_state_first_init) {
497 st->read_state_first_init = 0;
501 switch(st->read_state) {
502 case READ_STATE_HEADER:
504 /* Get the state the peer wants to move to */
505 if (SSL_IS_DTLS(s)) {
507 * In DTLS we get the whole message in one go - header and body
509 ret = dtls_get_message(s, &mt, &len);
511 ret = tls_get_message_header(s, &mt);
515 /* Could be non-blocking IO */
516 return SUB_STATE_ERROR;
520 /* Notify callback of an impending state change */
522 cb(s, SSL_CB_ACCEPT_LOOP, 1);
524 cb(s, SSL_CB_CONNECT_LOOP, 1);
527 * Validate that we are allowed to move to the new state and move
528 * to that state if so
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;
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;
542 st->read_state = READ_STATE_BODY;
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);
550 /* Could be non-blocking IO */
551 return SUB_STATE_ERROR;
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;
561 ret = process_message(s, &pkt);
562 if (ret == MSG_PROCESS_ERROR) {
563 return SUB_STATE_ERROR;
566 if (ret == MSG_PROCESS_FINISHED_READING) {
567 if (SSL_IS_DTLS(s)) {
570 return SUB_STATE_FINISHED;
573 if (ret == MSG_PROCESS_CONTINUE_PROCESSING) {
574 st->read_state = READ_STATE_POST_PROCESS;
575 st->read_state_work = WORK_MORE_A;
577 st->read_state = READ_STATE_HEADER;
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) {
585 return SUB_STATE_ERROR;
587 case WORK_FINISHED_CONTINUE:
588 st->read_state = READ_STATE_HEADER;
591 case WORK_FINISHED_STOP:
592 if (SSL_IS_DTLS(s)) {
595 return SUB_STATE_FINISHED;
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;
610 * Send a previously constructed message to the peer.
612 static int statem_do_write(SSL *s)
614 OSSL_STATEM *st = &s->statem;
616 if (st->hand_state == TLS_ST_CW_CHANGE
617 || st->hand_state == TLS_ST_SW_CHANGE) {
619 return dtls1_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
621 return ssl3_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
623 return ssl_do_write(s);
628 * Initialise the MSG_FLOW_WRITING sub-state machine
630 static void init_write_state_machine(SSL *s)
632 OSSL_STATEM *st = &s->statem;
634 st->write_state = WRITE_STATE_TRANSITION;
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:
641 * +-> WRITE_STATE_TRANSITION ------> [SUB_STATE_FINISHED]
644 * | WRITE_STATE_PRE_WORK -----> [SUB_STATE_END_HANDSHAKE]
650 * | WRITE_STATE_POST_WORK
654 * WRITE_STATE_TRANSITION transitions the state of the handshake state machine
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.
661 * WRITE_STATE_SEND sends the message and performs any work to be done after
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.
668 static SUB_STATE_RETURN write_state_machine(SSL *s)
670 OSSL_STATEM *st = &s->statem;
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;
678 cb = get_callback(s);
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;
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;
693 switch(st->write_state) {
694 case WRITE_STATE_TRANSITION:
696 /* Notify callback of an impending state change */
698 cb(s, SSL_CB_ACCEPT_LOOP, 1);
700 cb(s, SSL_CB_CONNECT_LOOP, 1);
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;
708 case WRITE_TRAN_FINISHED:
709 return SUB_STATE_FINISHED;
713 return SUB_STATE_ERROR;
717 case WRITE_STATE_PRE_WORK:
718 switch(st->write_state_work = pre_work(s, st->write_state_work)) {
720 return SUB_STATE_ERROR;
722 case WORK_FINISHED_CONTINUE:
723 st->write_state = WRITE_STATE_SEND;
726 case WORK_FINISHED_STOP:
727 return SUB_STATE_END_HANDSHAKE;
729 if(construct_message(s) == 0)
730 return SUB_STATE_ERROR;
734 case WRITE_STATE_SEND:
735 if (SSL_IS_DTLS(s) && st->use_timer) {
736 dtls1_start_timer(s);
738 ret = statem_do_write(s);
740 return SUB_STATE_ERROR;
742 st->write_state = WRITE_STATE_POST_WORK;
743 st->write_state_work = WORK_MORE_A;
746 case WRITE_STATE_POST_WORK:
747 switch(st->write_state_work = post_work(s, st->write_state_work)) {
749 return SUB_STATE_ERROR;
751 case WORK_FINISHED_CONTINUE:
752 st->write_state = WRITE_STATE_TRANSITION;
755 case WORK_FINISHED_STOP:
756 return SUB_STATE_END_HANDSHAKE;
761 return SUB_STATE_ERROR;
767 * Flush the write BIO
769 int statem_flush(SSL *s)
771 s->rwstate = SSL_WRITING;
772 if (BIO_flush(s->wbio) <= 0) {
775 s->rwstate = SSL_NOTHING;
781 * Called by the record layer to determine whether application data is
782 * allowed to be sent in the current handshake state or not.
785 * 1: Yes (application data allowed)
786 * 0: No (application data not allowed)
788 int ossl_statem_app_data_allowed(SSL *s)
790 OSSL_STATEM *st = &s->statem;
792 if (st->state == MSG_FLOW_UNINITED || st->state == MSG_FLOW_RENEGOTIATE)
795 if (!s->s3->in_read_app_data || (s->s3->total_renegotiations == 0))
800 * If we're a server and we haven't got as far as writing our
801 * ServerHello yet then we allow app data
803 if (st->hand_state == TLS_ST_BEFORE
804 || st->hand_state == TLS_ST_SR_CLNT_HELLO)
808 * If we're a client and we haven't read the ServerHello yet then we
811 if (st->hand_state == TLS_ST_CW_CLNT_HELLO)
818 #ifndef OPENSSL_NO_SCTP
820 * Set flag used by SCTP to determine whether we are in the read sock state
822 void ossl_statem_set_sctp_read_sock(SSL *s, int read_sock)
824 s->statem.in_sctp_read_sock = read_sock;
828 * Called by the record layer to determine whether we are in the read sock
832 * 1: Yes (we are in the read sock state)
833 * 0: No (we are not in the read sock state)
835 int ossl_statem_in_sctp_read_sock(SSL *s)
837 return s->statem.in_sctp_read_sock;