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;
323 if (!server
|| st
->state
!= MSG_FLOW_RENEGOTIATE
) {
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
, server
? 1 : 0)) {
335 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
;