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)
174 if ((send && s->statem.hand_state == TLS_ST_PENDING_EARLY_DATA_END)
175 || (!send && s->statem.hand_state == TLS_ST_EARLY_DATA))
176 ossl_statem_set_in_init(s, 1);
180 void ossl_statem_set_hello_verify_done(SSL *s)
182 s->statem.state = MSG_FLOW_UNINITED;
183 s->statem.in_init = 1;
185 * This will get reset (briefly) back to TLS_ST_BEFORE when we enter
186 * state_machine() because |state| is MSG_FLOW_UNINITED, but until then any
187 * calls to SSL_in_before() will return false. Also calls to
188 * SSL_state_string() and SSL_state_string_long() will return something
191 s->statem.hand_state = TLS_ST_SR_CLNT_HELLO;
194 int ossl_statem_connect(SSL *s)
196 return state_machine(s, 0);
199 int ossl_statem_accept(SSL *s)
201 return state_machine(s, 1);
204 typedef void (*info_cb) (const SSL *, int, int);
206 static info_cb get_callback(SSL *s)
208 if (s->info_callback != NULL)
209 return s->info_callback;
210 else if (s->ctx->info_callback != NULL)
211 return s->ctx->info_callback;
217 * The main message flow state machine. We start in the MSG_FLOW_UNINITED or
218 * MSG_FLOW_FINISHED state and finish in MSG_FLOW_FINISHED. Valid states and
219 * transitions are as follows:
221 * MSG_FLOW_UNINITED MSG_FLOW_FINISHED
223 * +-----------------------+
225 * MSG_FLOW_WRITING <---> MSG_FLOW_READING
233 * We may exit at any point due to an error or NBIO event. If an NBIO event
234 * occurs then we restart at the point we left off when we are recalled.
235 * MSG_FLOW_WRITING and MSG_FLOW_READING have sub-state machines associated with them.
237 * In addition to the above there is also the MSG_FLOW_ERROR state. We can move
238 * into that state at any point in the event that an irrecoverable error occurs.
240 * Valid return values are:
244 static int state_machine(SSL *s, int server)
247 unsigned long Time = (unsigned long)time(NULL);
248 void (*cb) (const SSL *ssl, int type, int val) = NULL;
249 OSSL_STATEM *st = &s->statem;
253 if (st->state == MSG_FLOW_ERROR) {
254 /* Shouldn't have been called if we're already in the error state */
258 RAND_add(&Time, sizeof(Time), 0);
262 cb = get_callback(s);
265 if (!SSL_in_init(s) || SSL_in_before(s)) {
269 #ifndef OPENSSL_NO_SCTP
270 if (SSL_IS_DTLS(s)) {
272 * Notify SCTP BIO socket to enter handshake mode and prevent stream
273 * identifier other than 0. Will be ignored if no SCTP is used.
275 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
276 st->in_handshake, NULL);
280 /* Initialise state machine */
281 if (st->state == MSG_FLOW_UNINITED
282 || st->state == MSG_FLOW_FINISHED) {
283 if (st->state == MSG_FLOW_UNINITED) {
284 st->hand_state = TLS_ST_BEFORE;
285 st->request_state = TLS_ST_BEFORE;
290 cb(s, SSL_CB_HANDSHAKE_START, 1);
292 if (SSL_IS_DTLS(s)) {
293 if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00) &&
294 (server || (s->version & 0xff00) != (DTLS1_BAD_VER & 0xff00))) {
295 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
299 if ((s->version >> 8) != SSL3_VERSION_MAJOR) {
300 SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
305 if (!ssl_security(s, SSL_SECOP_VERSION, 0, s->version, NULL)) {
306 SSLerr(SSL_F_STATE_MACHINE, SSL_R_VERSION_TOO_LOW);
310 if (s->init_buf == NULL) {
311 if ((buf = BUF_MEM_new()) == NULL) {
314 if (!BUF_MEM_grow(buf, SSL3_RT_MAX_PLAIN_LENGTH)) {
321 if (!ssl3_setup_buffers(s)) {
327 * Should have been reset by tls_process_finished, too.
329 s->s3->change_cipher_spec = 0;
332 * Ok, we now need to push on a buffering BIO ...but not with
335 #ifndef OPENSSL_NO_SCTP
336 if (!SSL_IS_DTLS(s) || !BIO_dgram_is_sctp(SSL_get_wbio(s)))
338 if (!ssl_init_wbio_buffer(s)) {
342 if ((SSL_IS_FIRST_HANDSHAKE(s)
343 && s->early_data_state != SSL_EARLY_DATA_FINISHED_WRITING
344 && s->early_data_state != SSL_EARLY_DATA_FINISHED_READING)
346 if (!tls_setup_handshake(s)) {
347 ossl_statem_set_error(s);
351 if (SSL_IS_FIRST_HANDSHAKE(s))
352 st->read_state_first_init = 1;
355 st->state = MSG_FLOW_WRITING;
356 init_write_state_machine(s);
359 while (st->state != MSG_FLOW_FINISHED) {
360 if (st->state == MSG_FLOW_READING) {
361 ssret = read_state_machine(s);
362 if (ssret == SUB_STATE_FINISHED) {
363 st->state = MSG_FLOW_WRITING;
364 init_write_state_machine(s);
369 } else if (st->state == MSG_FLOW_WRITING) {
370 ssret = write_state_machine(s);
371 if (ssret == SUB_STATE_FINISHED) {
372 st->state = MSG_FLOW_READING;
373 init_read_state_machine(s);
374 } else if (ssret == SUB_STATE_END_HANDSHAKE) {
375 st->state = MSG_FLOW_FINISHED;
382 ossl_statem_set_error(s);
392 #ifndef OPENSSL_NO_SCTP
393 if (SSL_IS_DTLS(s)) {
395 * Notify SCTP BIO socket to leave handshake mode and allow stream
396 * identifier other than 0. Will be ignored if no SCTP is used.
398 BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
399 st->in_handshake, NULL);
406 cb(s, SSL_CB_ACCEPT_EXIT, ret);
408 cb(s, SSL_CB_CONNECT_EXIT, ret);
414 * Initialise the MSG_FLOW_READING sub-state machine
416 static void init_read_state_machine(SSL *s)
418 OSSL_STATEM *st = &s->statem;
420 st->read_state = READ_STATE_HEADER;
423 static int grow_init_buf(SSL *s, size_t size) {
425 size_t msg_offset = (char *)s->init_msg - s->init_buf->data;
427 if (!BUF_MEM_grow_clean(s->init_buf, (int)size))
430 if (size < msg_offset)
433 s->init_msg = s->init_buf->data + msg_offset;
439 * This function implements the sub-state machine when the message flow is in
440 * MSG_FLOW_READING. The valid sub-states and transitions are:
442 * READ_STATE_HEADER <--+<-------------+
445 * READ_STATE_BODY -----+-->READ_STATE_POST_PROCESS
447 * +----------------------------+
449 * [SUB_STATE_FINISHED]
451 * READ_STATE_HEADER has the responsibility for reading in the message header
452 * and transitioning the state of the handshake state machine.
454 * READ_STATE_BODY reads in the rest of the message and then subsequently
457 * READ_STATE_POST_PROCESS is an optional step that may occur if some post
458 * processing activity performed on the message may block.
460 * Any of the above states could result in an NBIO event occurring in which case
461 * control returns to the calling application. When this function is recalled we
462 * will resume in the same state where we left off.
464 static SUB_STATE_RETURN read_state_machine(SSL *s)
466 OSSL_STATEM *st = &s->statem;
469 int (*transition) (SSL *s, int mt);
471 MSG_PROCESS_RETURN(*process_message) (SSL *s, PACKET *pkt);
472 WORK_STATE(*post_process_message) (SSL *s, WORK_STATE wst);
473 size_t (*max_message_size) (SSL *s);
474 void (*cb) (const SSL *ssl, int type, int val) = NULL;
476 cb = get_callback(s);
479 transition = ossl_statem_server_read_transition;
480 process_message = ossl_statem_server_process_message;
481 max_message_size = ossl_statem_server_max_message_size;
482 post_process_message = ossl_statem_server_post_process_message;
484 transition = ossl_statem_client_read_transition;
485 process_message = ossl_statem_client_process_message;
486 max_message_size = ossl_statem_client_max_message_size;
487 post_process_message = ossl_statem_client_post_process_message;
490 if (st->read_state_first_init) {
492 st->read_state_first_init = 0;
496 switch (st->read_state) {
497 case READ_STATE_HEADER:
498 /* Get the state the peer wants to move to */
499 if (SSL_IS_DTLS(s)) {
501 * In DTLS we get the whole message in one go - header and body
503 ret = dtls_get_message(s, &mt, &len);
505 ret = tls_get_message_header(s, &mt);
509 /* Could be non-blocking IO */
510 return SUB_STATE_ERROR;
514 /* Notify callback of an impending state change */
516 cb(s, SSL_CB_ACCEPT_LOOP, 1);
518 cb(s, SSL_CB_CONNECT_LOOP, 1);
521 * Validate that we are allowed to move to the new state and move
522 * to that state if so
524 if (!transition(s, mt)) {
525 ossl_statem_set_error(s);
526 return SUB_STATE_ERROR;
529 if (s->s3->tmp.message_size > max_message_size(s)) {
530 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
531 SSLerr(SSL_F_READ_STATE_MACHINE, SSL_R_EXCESSIVE_MESSAGE_SIZE);
532 return SUB_STATE_ERROR;
535 /* dtls_get_message already did this */
537 && s->s3->tmp.message_size > 0
538 && !grow_init_buf(s, s->s3->tmp.message_size
539 + SSL3_HM_HEADER_LENGTH)) {
540 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
541 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_BUF_LIB);
542 return SUB_STATE_ERROR;
545 st->read_state = READ_STATE_BODY;
548 case READ_STATE_BODY:
549 if (!SSL_IS_DTLS(s)) {
550 /* We already got this above for DTLS */
551 ret = tls_get_message_body(s, &len);
553 /* Could be non-blocking IO */
554 return SUB_STATE_ERROR;
559 if (!PACKET_buf_init(&pkt, s->init_msg, len)) {
560 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
561 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
562 return SUB_STATE_ERROR;
564 ret = process_message(s, &pkt);
566 /* Discard the packet data */
570 case MSG_PROCESS_ERROR:
571 return SUB_STATE_ERROR;
573 case MSG_PROCESS_FINISHED_READING:
574 if (SSL_IS_DTLS(s)) {
577 return SUB_STATE_FINISHED;
579 case MSG_PROCESS_CONTINUE_PROCESSING:
580 st->read_state = READ_STATE_POST_PROCESS;
581 st->read_state_work = WORK_MORE_A;
585 st->read_state = READ_STATE_HEADER;
590 case READ_STATE_POST_PROCESS:
591 st->read_state_work = post_process_message(s, st->read_state_work);
592 switch (st->read_state_work) {
597 return SUB_STATE_ERROR;
599 case WORK_FINISHED_CONTINUE:
600 st->read_state = READ_STATE_HEADER;
603 case WORK_FINISHED_STOP:
604 if (SSL_IS_DTLS(s)) {
607 return SUB_STATE_FINISHED;
612 /* Shouldn't happen */
613 ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
614 SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR);
615 ossl_statem_set_error(s);
616 return SUB_STATE_ERROR;
622 * Send a previously constructed message to the peer.
624 static int statem_do_write(SSL *s)
626 OSSL_STATEM *st = &s->statem;
628 if (st->hand_state == TLS_ST_CW_CHANGE
629 || st->hand_state == TLS_ST_SW_CHANGE) {
631 return dtls1_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
633 return ssl3_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC);
635 return ssl_do_write(s);
640 * Initialise the MSG_FLOW_WRITING sub-state machine
642 static void init_write_state_machine(SSL *s)
644 OSSL_STATEM *st = &s->statem;
646 st->write_state = WRITE_STATE_TRANSITION;
650 * This function implements the sub-state machine when the message flow is in
651 * MSG_FLOW_WRITING. The valid sub-states and transitions are:
653 * +-> WRITE_STATE_TRANSITION ------> [SUB_STATE_FINISHED]
656 * | WRITE_STATE_PRE_WORK -----> [SUB_STATE_END_HANDSHAKE]
662 * | WRITE_STATE_POST_WORK
666 * WRITE_STATE_TRANSITION transitions the state of the handshake state machine
668 * WRITE_STATE_PRE_WORK performs any work necessary to prepare the later
669 * sending of the message. This could result in an NBIO event occurring in
670 * which case control returns to the calling application. When this function
671 * is recalled we will resume in the same state where we left off.
673 * WRITE_STATE_SEND sends the message and performs any work to be done after
676 * WRITE_STATE_POST_WORK performs any work necessary after the sending of the
677 * message has been completed. As for WRITE_STATE_PRE_WORK this could also
678 * result in an NBIO event.
680 static SUB_STATE_RETURN write_state_machine(SSL *s)
682 OSSL_STATEM *st = &s->statem;
684 WRITE_TRAN(*transition) (SSL *s);
685 WORK_STATE(*pre_work) (SSL *s, WORK_STATE wst);
686 WORK_STATE(*post_work) (SSL *s, WORK_STATE wst);
687 int (*get_construct_message_f) (SSL *s, WPACKET *pkt,
688 int (**confunc) (SSL *s, WPACKET *pkt),
690 void (*cb) (const SSL *ssl, int type, int val) = NULL;
691 int (*confunc) (SSL *s, WPACKET *pkt);
695 cb = get_callback(s);
698 transition = ossl_statem_server_write_transition;
699 pre_work = ossl_statem_server_pre_work;
700 post_work = ossl_statem_server_post_work;
701 get_construct_message_f = ossl_statem_server_construct_message;
703 transition = ossl_statem_client_write_transition;
704 pre_work = ossl_statem_client_pre_work;
705 post_work = ossl_statem_client_post_work;
706 get_construct_message_f = ossl_statem_client_construct_message;
710 switch (st->write_state) {
711 case WRITE_STATE_TRANSITION:
713 /* Notify callback of an impending state change */
715 cb(s, SSL_CB_ACCEPT_LOOP, 1);
717 cb(s, SSL_CB_CONNECT_LOOP, 1);
719 switch (transition(s)) {
720 case WRITE_TRAN_CONTINUE:
721 st->write_state = WRITE_STATE_PRE_WORK;
722 st->write_state_work = WORK_MORE_A;
725 case WRITE_TRAN_FINISHED:
726 return SUB_STATE_FINISHED;
729 case WRITE_TRAN_ERROR:
730 return SUB_STATE_ERROR;
734 case WRITE_STATE_PRE_WORK:
735 switch (st->write_state_work = pre_work(s, st->write_state_work)) {
740 return SUB_STATE_ERROR;
742 case WORK_FINISHED_CONTINUE:
743 st->write_state = WRITE_STATE_SEND;
746 case WORK_FINISHED_STOP:
747 return SUB_STATE_END_HANDSHAKE;
749 if (!WPACKET_init(&pkt, s->init_buf)
750 || !get_construct_message_f(s, &pkt, &confunc, &mt)
751 || !ssl_set_handshake_header(s, &pkt, mt)
752 || (confunc != NULL && !confunc(s, &pkt))
753 || !ssl_close_construct_packet(s, &pkt, mt)
754 || !WPACKET_finish(&pkt)) {
755 WPACKET_cleanup(&pkt);
756 ossl_statem_set_error(s);
757 return SUB_STATE_ERROR;
762 case WRITE_STATE_SEND:
763 if (SSL_IS_DTLS(s) && st->use_timer) {
764 dtls1_start_timer(s);
766 ret = statem_do_write(s);
768 return SUB_STATE_ERROR;
770 st->write_state = WRITE_STATE_POST_WORK;
771 st->write_state_work = WORK_MORE_A;
774 case WRITE_STATE_POST_WORK:
775 switch (st->write_state_work = post_work(s, st->write_state_work)) {
780 return SUB_STATE_ERROR;
782 case WORK_FINISHED_CONTINUE:
783 st->write_state = WRITE_STATE_TRANSITION;
786 case WORK_FINISHED_STOP:
787 return SUB_STATE_END_HANDSHAKE;
792 return SUB_STATE_ERROR;
798 * Flush the write BIO
800 int statem_flush(SSL *s)
802 s->rwstate = SSL_WRITING;
803 if (BIO_flush(s->wbio) <= 0) {
806 s->rwstate = SSL_NOTHING;
812 * Called by the record layer to determine whether application data is
813 * allowed to be received in the current handshake state or not.
816 * 1: Yes (application data allowed)
817 * 0: No (application data not allowed)
819 int ossl_statem_app_data_allowed(SSL *s)
821 OSSL_STATEM *st = &s->statem;
823 if (st->state == MSG_FLOW_UNINITED)
826 if (!s->s3->in_read_app_data || (s->s3->total_renegotiations == 0))
831 * If we're a server and we haven't got as far as writing our
832 * ServerHello yet then we allow app data
834 if (st->hand_state == TLS_ST_BEFORE
835 || st->hand_state == TLS_ST_SR_CLNT_HELLO)
839 * If we're a client and we haven't read the ServerHello yet then we
842 if (st->hand_state == TLS_ST_CW_CLNT_HELLO)
849 #ifndef OPENSSL_NO_SCTP
851 * Set flag used by SCTP to determine whether we are in the read sock state
853 void ossl_statem_set_sctp_read_sock(SSL *s, int read_sock)
855 s->statem.in_sctp_read_sock = read_sock;
859 * Called by the record layer to determine whether we are in the read sock
863 * 1: Yes (we are in the read sock state)
864 * 0: No (we are not in the read sock state)
866 int ossl_statem_in_sctp_read_sock(SSL *s)
868 return s->statem.in_sctp_read_sock;