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 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)
170 return state_machine(s, 0);
173 int ossl_statem_accept(SSL *s)
175 return state_machine(s, 1);
178 typedef void (*info_cb) (const SSL *, int, int);
180 static info_cb get_callback(SSL *s)
182 if (s->info_callback != NULL)
183 return s->info_callback;
184 else if (s->ctx->info_callback != NULL)
185 return s->ctx->info_callback;
191 * The main message flow state machine. We start in the MSG_FLOW_UNINITED or
192 * MSG_FLOW_FINISHED state and finish in MSG_FLOW_FINISHED. Valid states and
193 * transitions are as follows:
195 * MSG_FLOW_UNINITED MSG_FLOW_FINISHED
197 * +-----------------------+
199 * MSG_FLOW_WRITING <---> MSG_FLOW_READING
207 * We may exit at any point due to an error or NBIO event. If an NBIO event
208 * occurs then we restart at the point we left off when we are recalled.
209 * MSG_FLOW_WRITING and MSG_FLOW_READING have sub-state machines associated with them.
211 * In addition to the above there is also the MSG_FLOW_ERROR state. We can move
212 * into that state at any point in the event that an irrecoverable error occurs.
214 * Valid return values are:
218 static int state_machine(SSL *s, int server)
221 unsigned long Time = (unsigned long)time(NULL);
222 void (*cb) (const SSL *ssl, int type, int val) = NULL;
223 OSSL_STATEM *st = &s->statem;
227 if (st->state == MSG_FLOW_ERROR) {
228 /* Shouldn't have been called if we're already in the error state */
232 RAND_add(&Time, sizeof(Time), 0);
236 cb = get_callback(s);
239 if (!SSL_in_init(s) || SSL_in_before(s)) {
243 #ifndef OPENSSL_NO_SCTP
244 if (SSL_IS_DTLS(s)) {
246 * Notify SCTP BIO socket to enter handshake mode and prevent stream
247 * identifier other than 0. Will be ignored if no SCTP is used.
249 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
250 st->in_handshake, NULL);
254 /* Initialise state machine */
255 if (st->state == MSG_FLOW_UNINITED
256 || st->state == MSG_FLOW_FINISHED) {
257 if (st->state == MSG_FLOW_UNINITED) {
258 st->hand_state = TLS_ST_BEFORE;
259 st->request_state = TLS_ST_BEFORE;
264 cb(s, SSL_CB_HANDSHAKE_START, 1);
266 if (SSL_IS_DTLS(s)) {
267 if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00) &&
268 (server || (s->version & 0xff00) != (DTLS1_BAD_VER & 0xff00))) {
269 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
273 if ((s->version >> 8) != SSL3_VERSION_MAJOR) {
274 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
279 if (!ssl_security(s, SSL_SECOP_VERSION, 0, s->version, NULL)) {
280 SSLerr(SSL_F_STATE_MACHINE, SSL_R_VERSION_TOO_LOW);
284 if (s->init_buf == NULL) {
285 if ((buf = BUF_MEM_new()) == NULL) {
288 if (!BUF_MEM_grow(buf, SSL3_RT_MAX_PLAIN_LENGTH)) {
295 if (!ssl3_setup_buffers(s)) {
301 * Should have been reset by tls_process_finished, too.
303 s->s3->change_cipher_spec = 0;
306 * Ok, we now need to push on a buffering BIO ...but not with
309 #ifndef OPENSSL_NO_SCTP
310 if (!SSL_IS_DTLS(s) || !BIO_dgram_is_sctp(SSL_get_wbio(s)))
312 if (!ssl_init_wbio_buffer(s)) {
316 if (SSL_IS_FIRST_HANDSHAKE(s) || s->renegotiate) {
317 if (!tls_setup_handshake(s)) {
318 ossl_statem_set_error(s);
322 if (SSL_IS_FIRST_HANDSHAKE(s))
323 st->read_state_first_init = 1;
326 st->state = MSG_FLOW_WRITING;
327 init_write_state_machine(s);
330 while (st->state != MSG_FLOW_FINISHED) {
331 if (st->state == MSG_FLOW_READING) {
332 ssret = read_state_machine(s);
333 if (ssret == SUB_STATE_FINISHED) {
334 st->state = MSG_FLOW_WRITING;
335 init_write_state_machine(s);
340 } else if (st->state == MSG_FLOW_WRITING) {
341 ssret = write_state_machine(s);
342 if (ssret == SUB_STATE_FINISHED) {
343 st->state = MSG_FLOW_READING;
344 init_read_state_machine(s);
345 } else if (ssret == SUB_STATE_END_HANDSHAKE) {
346 st->state = MSG_FLOW_FINISHED;
353 ossl_statem_set_error(s);
363 #ifndef OPENSSL_NO_SCTP
364 if (SSL_IS_DTLS(s)) {
366 * Notify SCTP BIO socket to leave handshake mode and allow stream
367 * identifier other than 0. Will be ignored if no SCTP is used.
369 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
370 st->in_handshake, NULL);
377 cb(s, SSL_CB_ACCEPT_EXIT, ret);
379 cb(s, SSL_CB_CONNECT_EXIT, ret);
385 * Initialise the MSG_FLOW_READING sub-state machine
387 static void init_read_state_machine(SSL *s)
389 OSSL_STATEM *st = &s->statem;
391 st->read_state = READ_STATE_HEADER;
394 static int grow_init_buf(SSL *s, size_t size) {
396 size_t msg_offset = (char *)s->init_msg - s->init_buf->data;
398 if (!BUF_MEM_grow_clean(s->init_buf, (int)size))
401 if (size < msg_offset)
404 s->init_msg = s->init_buf->data + msg_offset;
410 * This function implements the sub-state machine when the message flow is in
411 * MSG_FLOW_READING. The valid sub-states and transitions are:
413 * READ_STATE_HEADER <--+<-------------+
416 * READ_STATE_BODY -----+-->READ_STATE_POST_PROCESS
418 * +----------------------------+
420 * [SUB_STATE_FINISHED]
422 * READ_STATE_HEADER has the responsibility for reading in the message header
423 * and transitioning the state of the handshake state machine.
425 * READ_STATE_BODY reads in the rest of the message and then subsequently
428 * READ_STATE_POST_PROCESS is an optional step that may occur if some post
429 * processing activity performed on the message may block.
431 * Any of the above states could result in an NBIO event occurring in which case
432 * control returns to the calling application. When this function is recalled we
433 * will resume in the same state where we left off.
435 static SUB_STATE_RETURN read_state_machine(SSL *s)
437 OSSL_STATEM *st = &s->statem;
440 int (*transition) (SSL *s, int mt);
442 MSG_PROCESS_RETURN(*process_message) (SSL *s, PACKET *pkt);
443 WORK_STATE(*post_process_message) (SSL *s, WORK_STATE wst);
444 size_t (*max_message_size) (SSL *s);
445 void (*cb) (const SSL *ssl, int type, int val) = NULL;
447 cb = get_callback(s);
450 transition = ossl_statem_server_read_transition;
451 process_message = ossl_statem_server_process_message;
452 max_message_size = ossl_statem_server_max_message_size;
453 post_process_message = ossl_statem_server_post_process_message;
455 transition = ossl_statem_client_read_transition;
456 process_message = ossl_statem_client_process_message;
457 max_message_size = ossl_statem_client_max_message_size;
458 post_process_message = ossl_statem_client_post_process_message;
461 if (st->read_state_first_init) {
463 st->read_state_first_init = 0;
467 switch (st->read_state) {
468 case READ_STATE_HEADER:
469 /* Get the state the peer wants to move to */
470 if (SSL_IS_DTLS(s)) {
472 * In DTLS we get the whole message in one go - header and body
474 ret = dtls_get_message(s, &mt, &len);
476 ret = tls_get_message_header(s, &mt);
480 /* Could be non-blocking IO */
481 return SUB_STATE_ERROR;
485 /* Notify callback of an impending state change */
487 cb(s, SSL_CB_ACCEPT_LOOP, 1);
489 cb(s, SSL_CB_CONNECT_LOOP, 1);
492 * Validate that we are allowed to move to the new state and move
493 * to that state if so
495 if (!transition(s, mt)) {
496 ossl_statem_set_error(s);
497 return SUB_STATE_ERROR;
500 if (s->s3->tmp.message_size > max_message_size(s)) {
501 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
502 SSLerr(SSL_F_READ_STATE_MACHINE, SSL_R_EXCESSIVE_MESSAGE_SIZE);
503 return SUB_STATE_ERROR;
506 /* dtls_get_message already did this */
508 && s->s3->tmp.message_size > 0
509 && !grow_init_buf(s, s->s3->tmp.message_size
510 + SSL3_HM_HEADER_LENGTH)) {
511 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
512 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_BUF_LIB);
513 return SUB_STATE_ERROR;
516 st->read_state = READ_STATE_BODY;
519 case READ_STATE_BODY:
520 if (!SSL_IS_DTLS(s)) {
521 /* We already got this above for DTLS */
522 ret = tls_get_message_body(s, &len);
524 /* Could be non-blocking IO */
525 return SUB_STATE_ERROR;
530 if (!PACKET_buf_init(&pkt, s->init_msg, len)) {
531 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
532 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
533 return SUB_STATE_ERROR;
535 ret = process_message(s, &pkt);
537 /* Discard the packet data */
541 case MSG_PROCESS_ERROR:
542 return SUB_STATE_ERROR;
544 case MSG_PROCESS_FINISHED_READING:
545 if (SSL_IS_DTLS(s)) {
548 return SUB_STATE_FINISHED;
550 case MSG_PROCESS_CONTINUE_PROCESSING:
551 st->read_state = READ_STATE_POST_PROCESS;
552 st->read_state_work = WORK_MORE_A;
556 st->read_state = READ_STATE_HEADER;
561 case READ_STATE_POST_PROCESS:
562 st->read_state_work = post_process_message(s, st->read_state_work);
563 switch (st->read_state_work) {
567 return SUB_STATE_ERROR;
569 case WORK_FINISHED_CONTINUE:
570 st->read_state = READ_STATE_HEADER;
573 case WORK_FINISHED_STOP:
574 if (SSL_IS_DTLS(s)) {
577 return SUB_STATE_FINISHED;
582 /* Shouldn't happen */
583 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
584 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
585 ossl_statem_set_error(s);
586 return SUB_STATE_ERROR;
592 * Send a previously constructed message to the peer.
594 static int statem_do_write(SSL *s)
596 OSSL_STATEM *st = &s->statem;
598 if (st->hand_state == TLS_ST_CW_CHANGE
599 || st->hand_state == TLS_ST_SW_CHANGE) {
601 return dtls1_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
603 return ssl3_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
605 return ssl_do_write(s);
610 * Initialise the MSG_FLOW_WRITING sub-state machine
612 static void init_write_state_machine(SSL *s)
614 OSSL_STATEM *st = &s->statem;
616 st->write_state = WRITE_STATE_TRANSITION;
620 * This function implements the sub-state machine when the message flow is in
621 * MSG_FLOW_WRITING. The valid sub-states and transitions are:
623 * +-> WRITE_STATE_TRANSITION ------> [SUB_STATE_FINISHED]
626 * | WRITE_STATE_PRE_WORK -----> [SUB_STATE_END_HANDSHAKE]
632 * | WRITE_STATE_POST_WORK
636 * WRITE_STATE_TRANSITION transitions the state of the handshake state machine
638 * WRITE_STATE_PRE_WORK performs any work necessary to prepare the later
639 * sending of the message. This could result in an NBIO event occurring in
640 * which case control returns to the calling application. When this function
641 * is recalled we will resume in the same state where we left off.
643 * WRITE_STATE_SEND sends the message and performs any work to be done after
646 * WRITE_STATE_POST_WORK performs any work necessary after the sending of the
647 * message has been completed. As for WRITE_STATE_PRE_WORK this could also
648 * result in an NBIO event.
650 static SUB_STATE_RETURN write_state_machine(SSL *s)
652 OSSL_STATEM *st = &s->statem;
654 WRITE_TRAN(*transition) (SSL *s);
655 WORK_STATE(*pre_work) (SSL *s, WORK_STATE wst);
656 WORK_STATE(*post_work) (SSL *s, WORK_STATE wst);
657 int (*get_construct_message_f) (SSL *s, WPACKET *pkt,
658 int (**confunc) (SSL *s, WPACKET *pkt),
660 void (*cb) (const SSL *ssl, int type, int val) = NULL;
661 int (*confunc) (SSL *s, WPACKET *pkt);
665 cb = get_callback(s);
668 transition = ossl_statem_server_write_transition;
669 pre_work = ossl_statem_server_pre_work;
670 post_work = ossl_statem_server_post_work;
671 get_construct_message_f = ossl_statem_server_construct_message;
673 transition = ossl_statem_client_write_transition;
674 pre_work = ossl_statem_client_pre_work;
675 post_work = ossl_statem_client_post_work;
676 get_construct_message_f = ossl_statem_client_construct_message;
680 switch (st->write_state) {
681 case WRITE_STATE_TRANSITION:
683 /* Notify callback of an impending state change */
685 cb(s, SSL_CB_ACCEPT_LOOP, 1);
687 cb(s, SSL_CB_CONNECT_LOOP, 1);
689 switch (transition(s)) {
690 case WRITE_TRAN_CONTINUE:
691 st->write_state = WRITE_STATE_PRE_WORK;
692 st->write_state_work = WORK_MORE_A;
695 case WRITE_TRAN_FINISHED:
696 return SUB_STATE_FINISHED;
699 case WRITE_TRAN_ERROR:
700 return SUB_STATE_ERROR;
704 case WRITE_STATE_PRE_WORK:
705 switch (st->write_state_work = pre_work(s, st->write_state_work)) {
709 return SUB_STATE_ERROR;
711 case WORK_FINISHED_CONTINUE:
712 st->write_state = WRITE_STATE_SEND;
715 case WORK_FINISHED_STOP:
716 return SUB_STATE_END_HANDSHAKE;
718 if (!WPACKET_init(&pkt, s->init_buf)
719 || !get_construct_message_f(s, &pkt, &confunc, &mt)
720 || !ssl_set_handshake_header(s, &pkt, mt)
721 || (confunc != NULL && !confunc(s, &pkt))
722 || !ssl_close_construct_packet(s, &pkt, mt)
723 || !WPACKET_finish(&pkt)) {
724 WPACKET_cleanup(&pkt);
725 ossl_statem_set_error(s);
726 return SUB_STATE_ERROR;
731 case WRITE_STATE_SEND:
732 if (SSL_IS_DTLS(s) && st->use_timer) {
733 dtls1_start_timer(s);
735 ret = statem_do_write(s);
737 return SUB_STATE_ERROR;
739 st->write_state = WRITE_STATE_POST_WORK;
740 st->write_state_work = WORK_MORE_A;
743 case WRITE_STATE_POST_WORK:
744 switch (st->write_state_work = post_work(s, st->write_state_work)) {
748 return SUB_STATE_ERROR;
750 case WORK_FINISHED_CONTINUE:
751 st->write_state = WRITE_STATE_TRANSITION;
754 case WORK_FINISHED_STOP:
755 return SUB_STATE_END_HANDSHAKE;
760 return SUB_STATE_ERROR;
766 * Flush the write BIO
768 int statem_flush(SSL *s)
770 s->rwstate = SSL_WRITING;
771 if (BIO_flush(s->wbio) <= 0) {
774 s->rwstate = SSL_NOTHING;
780 * Called by the record layer to determine whether application data is
781 * allowed to be received in the current handshake state or not.
784 * 1: Yes (application data allowed)
785 * 0: No (application data not allowed)
787 int ossl_statem_app_data_allowed(SSL *s)
789 OSSL_STATEM *st = &s->statem;
791 if (st->state == MSG_FLOW_UNINITED)
794 if (!s->s3->in_read_app_data || (s->s3->total_renegotiations == 0))
799 * If we're a server and we haven't got as far as writing our
800 * ServerHello yet then we allow app data
802 if (st->hand_state == TLS_ST_BEFORE
803 || st->hand_state == TLS_ST_SR_CLNT_HELLO)
807 * If we're a client and we haven't read the ServerHello yet then we
810 if (st->hand_state == TLS_ST_CW_CLNT_HELLO)
817 #ifndef OPENSSL_NO_SCTP
819 * Set flag used by SCTP to determine whether we are in the read sock state
821 void ossl_statem_set_sctp_read_sock(SSL *s, int read_sock)
823 s->statem.in_sctp_read_sock = read_sock;
827 * Called by the record layer to determine whether we are in the read sock
831 * 1: Yes (we are in the read sock state)
832 * 0: No (we are not in the read sock state)
834 int ossl_statem_in_sctp_read_sock(SSL *s)
836 return s->statem.in_sctp_read_sock;