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_check_finish_init(SSL *s, int send)
173 if ((send && s->statem.hand_state == TLS_ST_CW_PENDING_EARLY_DATA_END)
174 || (!send && s->statem.hand_state == TLS_ST_CW_EARLY_DATA))
175 ossl_statem_set_in_init(s, 1);
178 void ossl_statem_set_hello_verify_done(SSL *s)
180 s->statem.state = MSG_FLOW_UNINITED;
181 s->statem.in_init = 1;
183 * This will get reset (briefly) back to TLS_ST_BEFORE when we enter
184 * state_machine() because |state| is MSG_FLOW_UNINITED, but until then any
185 * calls to SSL_in_before() will return false. Also calls to
186 * SSL_state_string() and SSL_state_string_long() will return something
189 s->statem.hand_state = TLS_ST_SR_CLNT_HELLO;
192 int ossl_statem_connect(SSL *s)
194 return state_machine(s, 0);
197 int ossl_statem_accept(SSL *s)
199 return state_machine(s, 1);
202 typedef void (*info_cb) (const SSL *, int, int);
204 static info_cb get_callback(SSL *s)
206 if (s->info_callback != NULL)
207 return s->info_callback;
208 else if (s->ctx->info_callback != NULL)
209 return s->ctx->info_callback;
215 * The main message flow state machine. We start in the MSG_FLOW_UNINITED or
216 * MSG_FLOW_FINISHED state and finish in MSG_FLOW_FINISHED. Valid states and
217 * transitions are as follows:
219 * MSG_FLOW_UNINITED MSG_FLOW_FINISHED
221 * +-----------------------+
223 * MSG_FLOW_WRITING <---> MSG_FLOW_READING
231 * We may exit at any point due to an error or NBIO event. If an NBIO event
232 * occurs then we restart at the point we left off when we are recalled.
233 * MSG_FLOW_WRITING and MSG_FLOW_READING have sub-state machines associated with them.
235 * In addition to the above there is also the MSG_FLOW_ERROR state. We can move
236 * into that state at any point in the event that an irrecoverable error occurs.
238 * Valid return values are:
242 static int state_machine(SSL *s, int server)
245 unsigned long Time = (unsigned long)time(NULL);
246 void (*cb) (const SSL *ssl, int type, int val) = NULL;
247 OSSL_STATEM *st = &s->statem;
251 if (st->state == MSG_FLOW_ERROR) {
252 /* Shouldn't have been called if we're already in the error state */
256 RAND_add(&Time, sizeof(Time), 0);
260 cb = get_callback(s);
263 if (!SSL_in_init(s) || SSL_in_before(s)) {
267 #ifndef OPENSSL_NO_SCTP
268 if (SSL_IS_DTLS(s)) {
270 * Notify SCTP BIO socket to enter handshake mode and prevent stream
271 * identifier other than 0. Will be ignored if no SCTP is used.
273 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
274 st->in_handshake, NULL);
278 /* Initialise state machine */
279 if (st->state == MSG_FLOW_UNINITED
280 || st->state == MSG_FLOW_FINISHED) {
281 if (st->state == MSG_FLOW_UNINITED) {
282 st->hand_state = TLS_ST_BEFORE;
283 st->request_state = TLS_ST_BEFORE;
288 cb(s, SSL_CB_HANDSHAKE_START, 1);
290 if (SSL_IS_DTLS(s)) {
291 if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00) &&
292 (server || (s->version & 0xff00) != (DTLS1_BAD_VER & 0xff00))) {
293 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
297 if ((s->version >> 8) != SSL3_VERSION_MAJOR) {
298 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
303 if (!ssl_security(s, SSL_SECOP_VERSION, 0, s->version, NULL)) {
304 SSLerr(SSL_F_STATE_MACHINE, SSL_R_VERSION_TOO_LOW);
308 if (s->init_buf == NULL) {
309 if ((buf = BUF_MEM_new()) == NULL) {
312 if (!BUF_MEM_grow(buf, SSL3_RT_MAX_PLAIN_LENGTH)) {
319 if (!ssl3_setup_buffers(s)) {
325 * Should have been reset by tls_process_finished, too.
327 s->s3->change_cipher_spec = 0;
330 * Ok, we now need to push on a buffering BIO ...but not with
333 #ifndef OPENSSL_NO_SCTP
334 if (!SSL_IS_DTLS(s) || !BIO_dgram_is_sctp(SSL_get_wbio(s)))
336 if (!ssl_init_wbio_buffer(s)) {
340 if ((SSL_IS_FIRST_HANDSHAKE(s)
341 && s->early_data_state != SSL_EARLY_DATA_FINISHED_WRITING
342 && s->early_data_state != SSL_EARLY_DATA_FINISHED_READING)
344 if (!tls_setup_handshake(s)) {
345 ossl_statem_set_error(s);
349 if (SSL_IS_FIRST_HANDSHAKE(s))
350 st->read_state_first_init = 1;
353 st->state = MSG_FLOW_WRITING;
354 init_write_state_machine(s);
357 while (st->state != MSG_FLOW_FINISHED) {
358 if (st->state == MSG_FLOW_READING) {
359 ssret = read_state_machine(s);
360 if (ssret == SUB_STATE_FINISHED) {
361 st->state = MSG_FLOW_WRITING;
362 init_write_state_machine(s);
367 } else if (st->state == MSG_FLOW_WRITING) {
368 ssret = write_state_machine(s);
369 if (ssret == SUB_STATE_FINISHED) {
370 st->state = MSG_FLOW_READING;
371 init_read_state_machine(s);
372 } else if (ssret == SUB_STATE_END_HANDSHAKE) {
373 st->state = MSG_FLOW_FINISHED;
380 ossl_statem_set_error(s);
390 #ifndef OPENSSL_NO_SCTP
391 if (SSL_IS_DTLS(s)) {
393 * Notify SCTP BIO socket to leave handshake mode and allow stream
394 * identifier other than 0. Will be ignored if no SCTP is used.
396 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
397 st->in_handshake, NULL);
404 cb(s, SSL_CB_ACCEPT_EXIT, ret);
406 cb(s, SSL_CB_CONNECT_EXIT, ret);
412 * Initialise the MSG_FLOW_READING sub-state machine
414 static void init_read_state_machine(SSL *s)
416 OSSL_STATEM *st = &s->statem;
418 st->read_state = READ_STATE_HEADER;
421 static int grow_init_buf(SSL *s, size_t size) {
423 size_t msg_offset = (char *)s->init_msg - s->init_buf->data;
425 if (!BUF_MEM_grow_clean(s->init_buf, (int)size))
428 if (size < msg_offset)
431 s->init_msg = s->init_buf->data + msg_offset;
437 * This function implements the sub-state machine when the message flow is in
438 * MSG_FLOW_READING. The valid sub-states and transitions are:
440 * READ_STATE_HEADER <--+<-------------+
443 * READ_STATE_BODY -----+-->READ_STATE_POST_PROCESS
445 * +----------------------------+
447 * [SUB_STATE_FINISHED]
449 * READ_STATE_HEADER has the responsibility for reading in the message header
450 * and transitioning the state of the handshake state machine.
452 * READ_STATE_BODY reads in the rest of the message and then subsequently
455 * READ_STATE_POST_PROCESS is an optional step that may occur if some post
456 * processing activity performed on the message may block.
458 * Any of the above states could result in an NBIO event occurring in which case
459 * control returns to the calling application. When this function is recalled we
460 * will resume in the same state where we left off.
462 static SUB_STATE_RETURN read_state_machine(SSL *s)
464 OSSL_STATEM *st = &s->statem;
467 int (*transition) (SSL *s, int mt);
469 MSG_PROCESS_RETURN(*process_message) (SSL *s, PACKET *pkt);
470 WORK_STATE(*post_process_message) (SSL *s, WORK_STATE wst);
471 size_t (*max_message_size) (SSL *s);
472 void (*cb) (const SSL *ssl, int type, int val) = NULL;
474 cb = get_callback(s);
477 transition = ossl_statem_server_read_transition;
478 process_message = ossl_statem_server_process_message;
479 max_message_size = ossl_statem_server_max_message_size;
480 post_process_message = ossl_statem_server_post_process_message;
482 transition = ossl_statem_client_read_transition;
483 process_message = ossl_statem_client_process_message;
484 max_message_size = ossl_statem_client_max_message_size;
485 post_process_message = ossl_statem_client_post_process_message;
488 if (st->read_state_first_init) {
490 st->read_state_first_init = 0;
494 switch (st->read_state) {
495 case READ_STATE_HEADER:
496 /* Get the state the peer wants to move to */
497 if (SSL_IS_DTLS(s)) {
499 * In DTLS we get the whole message in one go - header and body
501 ret = dtls_get_message(s, &mt, &len);
503 ret = tls_get_message_header(s, &mt);
507 /* Could be non-blocking IO */
508 return SUB_STATE_ERROR;
512 /* Notify callback of an impending state change */
514 cb(s, SSL_CB_ACCEPT_LOOP, 1);
516 cb(s, SSL_CB_CONNECT_LOOP, 1);
519 * Validate that we are allowed to move to the new state and move
520 * to that state if so
522 if (!transition(s, mt)) {
523 ossl_statem_set_error(s);
524 return SUB_STATE_ERROR;
527 if (s->s3->tmp.message_size > max_message_size(s)) {
528 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
529 SSLerr(SSL_F_READ_STATE_MACHINE, SSL_R_EXCESSIVE_MESSAGE_SIZE);
530 return SUB_STATE_ERROR;
533 /* dtls_get_message already did this */
535 && s->s3->tmp.message_size > 0
536 && !grow_init_buf(s, s->s3->tmp.message_size
537 + SSL3_HM_HEADER_LENGTH)) {
538 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
539 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_BUF_LIB);
540 return SUB_STATE_ERROR;
543 st->read_state = READ_STATE_BODY;
546 case READ_STATE_BODY:
547 if (!SSL_IS_DTLS(s)) {
548 /* We already got this above for DTLS */
549 ret = tls_get_message_body(s, &len);
551 /* Could be non-blocking IO */
552 return SUB_STATE_ERROR;
557 if (!PACKET_buf_init(&pkt, s->init_msg, len)) {
558 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
559 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
560 return SUB_STATE_ERROR;
562 ret = process_message(s, &pkt);
564 /* Discard the packet data */
568 case MSG_PROCESS_ERROR:
569 return SUB_STATE_ERROR;
571 case MSG_PROCESS_FINISHED_READING:
572 if (SSL_IS_DTLS(s)) {
575 return SUB_STATE_FINISHED;
577 case MSG_PROCESS_CONTINUE_PROCESSING:
578 st->read_state = READ_STATE_POST_PROCESS;
579 st->read_state_work = WORK_MORE_A;
583 st->read_state = READ_STATE_HEADER;
588 case READ_STATE_POST_PROCESS:
589 st->read_state_work = post_process_message(s, st->read_state_work);
590 switch (st->read_state_work) {
595 return SUB_STATE_ERROR;
597 case WORK_FINISHED_CONTINUE:
598 st->read_state = READ_STATE_HEADER;
601 case WORK_FINISHED_STOP:
602 if (SSL_IS_DTLS(s)) {
605 return SUB_STATE_FINISHED;
610 /* Shouldn't happen */
611 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
612 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
613 ossl_statem_set_error(s);
614 return SUB_STATE_ERROR;
620 * Send a previously constructed message to the peer.
622 static int statem_do_write(SSL *s)
624 OSSL_STATEM *st = &s->statem;
626 if (st->hand_state == TLS_ST_CW_CHANGE
627 || st->hand_state == TLS_ST_SW_CHANGE) {
629 return dtls1_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
631 return ssl3_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
633 return ssl_do_write(s);
638 * Initialise the MSG_FLOW_WRITING sub-state machine
640 static void init_write_state_machine(SSL *s)
642 OSSL_STATEM *st = &s->statem;
644 st->write_state = WRITE_STATE_TRANSITION;
648 * This function implements the sub-state machine when the message flow is in
649 * MSG_FLOW_WRITING. The valid sub-states and transitions are:
651 * +-> WRITE_STATE_TRANSITION ------> [SUB_STATE_FINISHED]
654 * | WRITE_STATE_PRE_WORK -----> [SUB_STATE_END_HANDSHAKE]
660 * | WRITE_STATE_POST_WORK
664 * WRITE_STATE_TRANSITION transitions the state of the handshake state machine
666 * WRITE_STATE_PRE_WORK performs any work necessary to prepare the later
667 * sending of the message. This could result in an NBIO event occurring in
668 * which case control returns to the calling application. When this function
669 * is recalled we will resume in the same state where we left off.
671 * WRITE_STATE_SEND sends the message and performs any work to be done after
674 * WRITE_STATE_POST_WORK performs any work necessary after the sending of the
675 * message has been completed. As for WRITE_STATE_PRE_WORK this could also
676 * result in an NBIO event.
678 static SUB_STATE_RETURN write_state_machine(SSL *s)
680 OSSL_STATEM *st = &s->statem;
682 WRITE_TRAN(*transition) (SSL *s);
683 WORK_STATE(*pre_work) (SSL *s, WORK_STATE wst);
684 WORK_STATE(*post_work) (SSL *s, WORK_STATE wst);
685 int (*get_construct_message_f) (SSL *s, WPACKET *pkt,
686 int (**confunc) (SSL *s, WPACKET *pkt),
688 void (*cb) (const SSL *ssl, int type, int val) = NULL;
689 int (*confunc) (SSL *s, WPACKET *pkt);
693 cb = get_callback(s);
696 transition = ossl_statem_server_write_transition;
697 pre_work = ossl_statem_server_pre_work;
698 post_work = ossl_statem_server_post_work;
699 get_construct_message_f = ossl_statem_server_construct_message;
701 transition = ossl_statem_client_write_transition;
702 pre_work = ossl_statem_client_pre_work;
703 post_work = ossl_statem_client_post_work;
704 get_construct_message_f = ossl_statem_client_construct_message;
708 switch (st->write_state) {
709 case WRITE_STATE_TRANSITION:
711 /* Notify callback of an impending state change */
713 cb(s, SSL_CB_ACCEPT_LOOP, 1);
715 cb(s, SSL_CB_CONNECT_LOOP, 1);
717 switch (transition(s)) {
718 case WRITE_TRAN_CONTINUE:
719 st->write_state = WRITE_STATE_PRE_WORK;
720 st->write_state_work = WORK_MORE_A;
723 case WRITE_TRAN_FINISHED:
724 return SUB_STATE_FINISHED;
727 case WRITE_TRAN_ERROR:
728 return SUB_STATE_ERROR;
732 case WRITE_STATE_PRE_WORK:
733 switch (st->write_state_work = pre_work(s, st->write_state_work)) {
738 return SUB_STATE_ERROR;
740 case WORK_FINISHED_CONTINUE:
741 st->write_state = WRITE_STATE_SEND;
744 case WORK_FINISHED_STOP:
745 return SUB_STATE_END_HANDSHAKE;
747 if (!WPACKET_init(&pkt, s->init_buf)
748 || !get_construct_message_f(s, &pkt, &confunc, &mt)
749 || !ssl_set_handshake_header(s, &pkt, mt)
750 || (confunc != NULL && !confunc(s, &pkt))
751 || !ssl_close_construct_packet(s, &pkt, mt)
752 || !WPACKET_finish(&pkt)) {
753 WPACKET_cleanup(&pkt);
754 ossl_statem_set_error(s);
755 return SUB_STATE_ERROR;
760 case WRITE_STATE_SEND:
761 if (SSL_IS_DTLS(s) && st->use_timer) {
762 dtls1_start_timer(s);
764 ret = statem_do_write(s);
766 return SUB_STATE_ERROR;
768 st->write_state = WRITE_STATE_POST_WORK;
769 st->write_state_work = WORK_MORE_A;
772 case WRITE_STATE_POST_WORK:
773 switch (st->write_state_work = post_work(s, st->write_state_work)) {
778 return SUB_STATE_ERROR;
780 case WORK_FINISHED_CONTINUE:
781 st->write_state = WRITE_STATE_TRANSITION;
784 case WORK_FINISHED_STOP:
785 return SUB_STATE_END_HANDSHAKE;
790 return SUB_STATE_ERROR;
796 * Flush the write BIO
798 int statem_flush(SSL *s)
800 s->rwstate = SSL_WRITING;
801 if (BIO_flush(s->wbio) <= 0) {
804 s->rwstate = SSL_NOTHING;
810 * Called by the record layer to determine whether application data is
811 * allowed to be received in the current handshake state or not.
814 * 1: Yes (application data allowed)
815 * 0: No (application data not allowed)
817 int ossl_statem_app_data_allowed(SSL *s)
819 OSSL_STATEM *st = &s->statem;
821 if (st->state == MSG_FLOW_UNINITED)
824 if (!s->s3->in_read_app_data || (s->s3->total_renegotiations == 0))
829 * If we're a server and we haven't got as far as writing our
830 * ServerHello yet then we allow app data
832 if (st->hand_state == TLS_ST_BEFORE
833 || st->hand_state == TLS_ST_SR_CLNT_HELLO)
837 * If we're a client and we haven't read the ServerHello yet then we
840 if (st->hand_state == TLS_ST_CW_CLNT_HELLO)
847 #ifndef OPENSSL_NO_SCTP
849 * Set flag used by SCTP to determine whether we are in the read sock state
851 void ossl_statem_set_sctp_read_sock(SSL *s, int read_sock)
853 s->statem.in_sctp_read_sock = read_sock;
857 * Called by the record layer to determine whether we are in the read sock
861 * 1: Yes (we are in the read sock state)
862 * 0: No (we are not in the read sock state)
864 int ossl_statem_in_sctp_read_sock(SSL *s)
866 return s->statem.in_sctp_read_sock;