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.in_init = 1;
109 s->statem.request_state = TLS_ST_SW_HELLO_REQ;
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 /* Are we in a sensible state to skip over unreadable early data? */
155 int ossl_statem_skip_early_data(SSL *s)
157 if (s->ext.early_data != SSL_EARLY_DATA_REJECTED)
160 if (s->hello_retry_request) {
161 if (s->statem.hand_state != TLS_ST_SW_HELLO_RETRY_REQUEST)
164 if (s->statem.hand_state != TLS_ST_SW_FINISHED)
171 void ossl_statem_set_hello_verify_done(SSL *s)
173 s->statem.state = MSG_FLOW_UNINITED;
174 s->statem.in_init = 1;
176 * This will get reset (briefly) back to TLS_ST_BEFORE when we enter
177 * state_machine() because |state| is MSG_FLOW_UNINITED, but until then any
178 * calls to SSL_in_before() will return false. Also calls to
179 * SSL_state_string() and SSL_state_string_long() will return something
182 s->statem.hand_state = TLS_ST_SR_CLNT_HELLO;
185 int ossl_statem_connect(SSL *s)
187 return state_machine(s, 0);
190 int ossl_statem_accept(SSL *s)
192 return state_machine(s, 1);
195 typedef void (*info_cb) (const SSL *, int, int);
197 static info_cb get_callback(SSL *s)
199 if (s->info_callback != NULL)
200 return s->info_callback;
201 else if (s->ctx->info_callback != NULL)
202 return s->ctx->info_callback;
208 * The main message flow state machine. We start in the MSG_FLOW_UNINITED or
209 * MSG_FLOW_FINISHED state and finish in MSG_FLOW_FINISHED. Valid states and
210 * transitions are as follows:
212 * MSG_FLOW_UNINITED MSG_FLOW_FINISHED
214 * +-----------------------+
216 * MSG_FLOW_WRITING <---> MSG_FLOW_READING
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.
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.
231 * Valid return values are:
235 static int state_machine(SSL *s, int server)
238 unsigned long Time = (unsigned long)time(NULL);
239 void (*cb) (const SSL *ssl, int type, int val) = NULL;
240 OSSL_STATEM *st = &s->statem;
244 if (st->state == MSG_FLOW_ERROR) {
245 /* Shouldn't have been called if we're already in the error state */
249 RAND_add(&Time, sizeof(Time), 0);
253 cb = get_callback(s);
256 if (!SSL_in_init(s) || SSL_in_before(s)) {
260 #ifndef OPENSSL_NO_SCTP
261 if (SSL_IS_DTLS(s)) {
263 * Notify SCTP BIO socket to enter handshake mode and prevent stream
264 * identifier other than 0. Will be ignored if no SCTP is used.
266 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
267 st->in_handshake, NULL);
271 /* Initialise state machine */
272 if (st->state == MSG_FLOW_UNINITED
273 || st->state == MSG_FLOW_FINISHED) {
274 if (st->state == MSG_FLOW_UNINITED) {
275 st->hand_state = TLS_ST_BEFORE;
276 st->request_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) &&
285 (server || (s->version & 0xff00) != (DTLS1_BAD_VER & 0xff00))) {
286 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
290 if ((s->version >> 8) != SSL3_VERSION_MAJOR) {
291 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
296 if (!ssl_security(s, SSL_SECOP_VERSION, 0, s->version, NULL)) {
297 SSLerr(SSL_F_STATE_MACHINE, SSL_R_VERSION_TOO_LOW);
301 if (s->init_buf == NULL) {
302 if ((buf = BUF_MEM_new()) == NULL) {
305 if (!BUF_MEM_grow(buf, SSL3_RT_MAX_PLAIN_LENGTH)) {
312 if (!ssl3_setup_buffers(s)) {
318 * Should have been reset by tls_process_finished, too.
320 s->s3->change_cipher_spec = 0;
323 * Ok, we now need to push on a buffering BIO ...but not with
326 #ifndef OPENSSL_NO_SCTP
327 if (!SSL_IS_DTLS(s) || !BIO_dgram_is_sctp(SSL_get_wbio(s)))
329 if (!ssl_init_wbio_buffer(s)) {
333 if ((SSL_IS_FIRST_HANDSHAKE(s)
334 && s->early_data_state != SSL_EARLY_DATA_FINISHED_WRITING
335 && s->early_data_state != SSL_EARLY_DATA_FINISHED_READING)
337 if (!tls_setup_handshake(s)) {
338 ossl_statem_set_error(s);
342 if (SSL_IS_FIRST_HANDSHAKE(s))
343 st->read_state_first_init = 1;
346 st->state = MSG_FLOW_WRITING;
347 init_write_state_machine(s);
350 while (st->state != MSG_FLOW_FINISHED) {
351 if (st->state == MSG_FLOW_READING) {
352 ssret = read_state_machine(s);
353 if (ssret == SUB_STATE_FINISHED) {
354 st->state = MSG_FLOW_WRITING;
355 init_write_state_machine(s);
360 } else if (st->state == MSG_FLOW_WRITING) {
361 ssret = write_state_machine(s);
362 if (ssret == SUB_STATE_FINISHED) {
363 st->state = MSG_FLOW_READING;
364 init_read_state_machine(s);
365 } else if (ssret == SUB_STATE_END_HANDSHAKE) {
366 st->state = MSG_FLOW_FINISHED;
373 ossl_statem_set_error(s);
383 #ifndef OPENSSL_NO_SCTP
384 if (SSL_IS_DTLS(s)) {
386 * Notify SCTP BIO socket to leave handshake mode and allow stream
387 * identifier other than 0. Will be ignored if no SCTP is used.
389 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
390 st->in_handshake, NULL);
397 cb(s, SSL_CB_ACCEPT_EXIT, ret);
399 cb(s, SSL_CB_CONNECT_EXIT, ret);
405 * Initialise the MSG_FLOW_READING sub-state machine
407 static void init_read_state_machine(SSL *s)
409 OSSL_STATEM *st = &s->statem;
411 st->read_state = READ_STATE_HEADER;
414 static int grow_init_buf(SSL *s, size_t size) {
416 size_t msg_offset = (char *)s->init_msg - s->init_buf->data;
418 if (!BUF_MEM_grow_clean(s->init_buf, (int)size))
421 if (size < msg_offset)
424 s->init_msg = s->init_buf->data + msg_offset;
430 * This function implements the sub-state machine when the message flow is in
431 * MSG_FLOW_READING. The valid sub-states and transitions are:
433 * READ_STATE_HEADER <--+<-------------+
436 * READ_STATE_BODY -----+-->READ_STATE_POST_PROCESS
438 * +----------------------------+
440 * [SUB_STATE_FINISHED]
442 * READ_STATE_HEADER has the responsibility for reading in the message header
443 * and transitioning the state of the handshake state machine.
445 * READ_STATE_BODY reads in the rest of the message and then subsequently
448 * READ_STATE_POST_PROCESS is an optional step that may occur if some post
449 * processing activity performed on the message may block.
451 * Any of the above states could result in an NBIO event occurring in which case
452 * control returns to the calling application. When this function is recalled we
453 * will resume in the same state where we left off.
455 static SUB_STATE_RETURN read_state_machine(SSL *s)
457 OSSL_STATEM *st = &s->statem;
460 int (*transition) (SSL *s, int mt);
462 MSG_PROCESS_RETURN(*process_message) (SSL *s, PACKET *pkt);
463 WORK_STATE(*post_process_message) (SSL *s, WORK_STATE wst);
464 size_t (*max_message_size) (SSL *s);
465 void (*cb) (const SSL *ssl, int type, int val) = NULL;
467 cb = get_callback(s);
470 transition = ossl_statem_server_read_transition;
471 process_message = ossl_statem_server_process_message;
472 max_message_size = ossl_statem_server_max_message_size;
473 post_process_message = ossl_statem_server_post_process_message;
475 transition = ossl_statem_client_read_transition;
476 process_message = ossl_statem_client_process_message;
477 max_message_size = ossl_statem_client_max_message_size;
478 post_process_message = ossl_statem_client_post_process_message;
481 if (st->read_state_first_init) {
483 st->read_state_first_init = 0;
487 switch (st->read_state) {
488 case READ_STATE_HEADER:
489 /* Get the state the peer wants to move to */
490 if (SSL_IS_DTLS(s)) {
492 * In DTLS we get the whole message in one go - header and body
494 ret = dtls_get_message(s, &mt, &len);
496 ret = tls_get_message_header(s, &mt);
500 /* Could be non-blocking IO */
501 return SUB_STATE_ERROR;
505 /* Notify callback of an impending state change */
507 cb(s, SSL_CB_ACCEPT_LOOP, 1);
509 cb(s, SSL_CB_CONNECT_LOOP, 1);
512 * Validate that we are allowed to move to the new state and move
513 * to that state if so
515 if (!transition(s, mt)) {
516 ossl_statem_set_error(s);
517 return SUB_STATE_ERROR;
520 if (s->s3->tmp.message_size > max_message_size(s)) {
521 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
522 SSLerr(SSL_F_READ_STATE_MACHINE, SSL_R_EXCESSIVE_MESSAGE_SIZE);
523 return SUB_STATE_ERROR;
526 /* dtls_get_message already did this */
528 && s->s3->tmp.message_size > 0
529 && !grow_init_buf(s, s->s3->tmp.message_size
530 + SSL3_HM_HEADER_LENGTH)) {
531 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
532 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_BUF_LIB);
533 return SUB_STATE_ERROR;
536 st->read_state = READ_STATE_BODY;
539 case READ_STATE_BODY:
540 if (!SSL_IS_DTLS(s)) {
541 /* We already got this above for DTLS */
542 ret = tls_get_message_body(s, &len);
544 /* Could be non-blocking IO */
545 return SUB_STATE_ERROR;
550 if (!PACKET_buf_init(&pkt, s->init_msg, len)) {
551 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
552 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
553 return SUB_STATE_ERROR;
555 ret = process_message(s, &pkt);
557 /* Discard the packet data */
561 case MSG_PROCESS_ERROR:
562 return SUB_STATE_ERROR;
564 case MSG_PROCESS_FINISHED_READING:
565 if (SSL_IS_DTLS(s)) {
568 return SUB_STATE_FINISHED;
570 case MSG_PROCESS_CONTINUE_PROCESSING:
571 st->read_state = READ_STATE_POST_PROCESS;
572 st->read_state_work = WORK_MORE_A;
576 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) {
588 return SUB_STATE_ERROR;
590 case WORK_FINISHED_CONTINUE:
591 st->read_state = READ_STATE_HEADER;
594 case WORK_FINISHED_STOP:
595 if (SSL_IS_DTLS(s)) {
598 return SUB_STATE_FINISHED;
603 /* Shouldn't happen */
604 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
605 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
606 ossl_statem_set_error(s);
607 return SUB_STATE_ERROR;
613 * Send a previously constructed message to the peer.
615 static int statem_do_write(SSL *s)
617 OSSL_STATEM *st = &s->statem;
619 if (st->hand_state == TLS_ST_CW_CHANGE
620 || st->hand_state == TLS_ST_SW_CHANGE) {
622 return dtls1_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
624 return ssl3_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
626 return ssl_do_write(s);
631 * Initialise the MSG_FLOW_WRITING sub-state machine
633 static void init_write_state_machine(SSL *s)
635 OSSL_STATEM *st = &s->statem;
637 st->write_state = WRITE_STATE_TRANSITION;
641 * This function implements the sub-state machine when the message flow is in
642 * MSG_FLOW_WRITING. The valid sub-states and transitions are:
644 * +-> WRITE_STATE_TRANSITION ------> [SUB_STATE_FINISHED]
647 * | WRITE_STATE_PRE_WORK -----> [SUB_STATE_END_HANDSHAKE]
653 * | WRITE_STATE_POST_WORK
657 * WRITE_STATE_TRANSITION transitions the state of the handshake state machine
659 * WRITE_STATE_PRE_WORK performs any work necessary to prepare the later
660 * sending of the message. This could result in an NBIO event occurring in
661 * which case control returns to the calling application. When this function
662 * is recalled we will resume in the same state where we left off.
664 * WRITE_STATE_SEND sends the message and performs any work to be done after
667 * WRITE_STATE_POST_WORK performs any work necessary after the sending of the
668 * message has been completed. As for WRITE_STATE_PRE_WORK this could also
669 * result in an NBIO event.
671 static SUB_STATE_RETURN write_state_machine(SSL *s)
673 OSSL_STATEM *st = &s->statem;
675 WRITE_TRAN(*transition) (SSL *s);
676 WORK_STATE(*pre_work) (SSL *s, WORK_STATE wst);
677 WORK_STATE(*post_work) (SSL *s, WORK_STATE wst);
678 int (*get_construct_message_f) (SSL *s, WPACKET *pkt,
679 int (**confunc) (SSL *s, WPACKET *pkt),
681 void (*cb) (const SSL *ssl, int type, int val) = NULL;
682 int (*confunc) (SSL *s, WPACKET *pkt);
686 cb = get_callback(s);
689 transition = ossl_statem_server_write_transition;
690 pre_work = ossl_statem_server_pre_work;
691 post_work = ossl_statem_server_post_work;
692 get_construct_message_f = ossl_statem_server_construct_message;
694 transition = ossl_statem_client_write_transition;
695 pre_work = ossl_statem_client_pre_work;
696 post_work = ossl_statem_client_post_work;
697 get_construct_message_f = ossl_statem_client_construct_message;
701 switch (st->write_state) {
702 case WRITE_STATE_TRANSITION:
704 /* Notify callback of an impending state change */
706 cb(s, SSL_CB_ACCEPT_LOOP, 1);
708 cb(s, SSL_CB_CONNECT_LOOP, 1);
710 switch (transition(s)) {
711 case WRITE_TRAN_CONTINUE:
712 st->write_state = WRITE_STATE_PRE_WORK;
713 st->write_state_work = WORK_MORE_A;
716 case WRITE_TRAN_FINISHED:
717 return SUB_STATE_FINISHED;
720 case WRITE_TRAN_ERROR:
721 return SUB_STATE_ERROR;
725 case WRITE_STATE_PRE_WORK:
726 switch (st->write_state_work = pre_work(s, st->write_state_work)) {
731 return SUB_STATE_ERROR;
733 case WORK_FINISHED_CONTINUE:
734 st->write_state = WRITE_STATE_SEND;
737 case WORK_FINISHED_STOP:
738 return SUB_STATE_END_HANDSHAKE;
740 if (!WPACKET_init(&pkt, s->init_buf)
741 || !get_construct_message_f(s, &pkt, &confunc, &mt)
742 || !ssl_set_handshake_header(s, &pkt, mt)
743 || (confunc != NULL && !confunc(s, &pkt))
744 || !ssl_close_construct_packet(s, &pkt, mt)
745 || !WPACKET_finish(&pkt)) {
746 WPACKET_cleanup(&pkt);
747 ossl_statem_set_error(s);
748 return SUB_STATE_ERROR;
753 case WRITE_STATE_SEND:
754 if (SSL_IS_DTLS(s) && st->use_timer) {
755 dtls1_start_timer(s);
757 ret = statem_do_write(s);
759 return SUB_STATE_ERROR;
761 st->write_state = WRITE_STATE_POST_WORK;
762 st->write_state_work = WORK_MORE_A;
765 case WRITE_STATE_POST_WORK:
766 switch (st->write_state_work = post_work(s, st->write_state_work)) {
771 return SUB_STATE_ERROR;
773 case WORK_FINISHED_CONTINUE:
774 st->write_state = WRITE_STATE_TRANSITION;
777 case WORK_FINISHED_STOP:
778 return SUB_STATE_END_HANDSHAKE;
783 return SUB_STATE_ERROR;
789 * Flush the write BIO
791 int statem_flush(SSL *s)
793 s->rwstate = SSL_WRITING;
794 if (BIO_flush(s->wbio) <= 0) {
797 s->rwstate = SSL_NOTHING;
803 * Called by the record layer to determine whether application data is
804 * allowed to be received in the current handshake state or not.
807 * 1: Yes (application data allowed)
808 * 0: No (application data not allowed)
810 int ossl_statem_app_data_allowed(SSL *s)
812 OSSL_STATEM *st = &s->statem;
814 if (st->state == MSG_FLOW_UNINITED)
817 if (!s->s3->in_read_app_data || (s->s3->total_renegotiations == 0))
822 * If we're a server and we haven't got as far as writing our
823 * ServerHello yet then we allow app data
825 if (st->hand_state == TLS_ST_BEFORE
826 || st->hand_state == TLS_ST_SR_CLNT_HELLO)
830 * If we're a client and we haven't read the ServerHello yet then we
833 if (st->hand_state == TLS_ST_CW_CLNT_HELLO)
840 #ifndef OPENSSL_NO_SCTP
842 * Set flag used by SCTP to determine whether we are in the read sock state
844 void ossl_statem_set_sctp_read_sock(SSL *s, int read_sock)
846 s->statem.in_sctp_read_sock = read_sock;
850 * Called by the record layer to determine whether we are in the read sock
854 * 1: Yes (we are in the read sock state)
855 * 0: No (we are not in the read sock state)
857 int ossl_statem_in_sctp_read_sock(SSL *s)
859 return s->statem.in_sctp_read_sock;