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
->statem
.hand_state
!= TLS_ST_SW_FINISHED
)
166 void ossl_statem_set_hello_verify_done(SSL
*s
)
168 s
->statem
.state
= MSG_FLOW_UNINITED
;
169 s
->statem
.in_init
= 1;
171 * This will get reset (briefly) back to TLS_ST_BEFORE when we enter
172 * state_machine() because |state| is MSG_FLOW_UNINITED, but until then any
173 * calls to SSL_in_before() will return false. Also calls to
174 * SSL_state_string() and SSL_state_string_long() will return something
177 s
->statem
.hand_state
= TLS_ST_SR_CLNT_HELLO
;
180 int ossl_statem_connect(SSL
*s
)
182 return state_machine(s
, 0);
185 int ossl_statem_accept(SSL
*s
)
187 return state_machine(s
, 1);
190 typedef void (*info_cb
) (const SSL
*, int, int);
192 static info_cb
get_callback(SSL
*s
)
194 if (s
->info_callback
!= NULL
)
195 return s
->info_callback
;
196 else if (s
->ctx
->info_callback
!= NULL
)
197 return s
->ctx
->info_callback
;
203 * The main message flow state machine. We start in the MSG_FLOW_UNINITED or
204 * MSG_FLOW_FINISHED state and finish in MSG_FLOW_FINISHED. Valid states and
205 * transitions are as follows:
207 * MSG_FLOW_UNINITED MSG_FLOW_FINISHED
209 * +-----------------------+
211 * MSG_FLOW_WRITING <---> MSG_FLOW_READING
219 * We may exit at any point due to an error or NBIO event. If an NBIO event
220 * occurs then we restart at the point we left off when we are recalled.
221 * MSG_FLOW_WRITING and MSG_FLOW_READING have sub-state machines associated with them.
223 * In addition to the above there is also the MSG_FLOW_ERROR state. We can move
224 * into that state at any point in the event that an irrecoverable error occurs.
226 * Valid return values are:
230 static int state_machine(SSL
*s
, int server
)
233 unsigned long Time
= (unsigned long)time(NULL
);
234 void (*cb
) (const SSL
*ssl
, int type
, int val
) = NULL
;
235 OSSL_STATEM
*st
= &s
->statem
;
239 if (st
->state
== MSG_FLOW_ERROR
) {
240 /* Shouldn't have been called if we're already in the error state */
244 RAND_add(&Time
, sizeof(Time
), 0);
248 cb
= get_callback(s
);
251 if (!SSL_in_init(s
) || SSL_in_before(s
)) {
255 #ifndef OPENSSL_NO_SCTP
256 if (SSL_IS_DTLS(s
)) {
258 * Notify SCTP BIO socket to enter handshake mode and prevent stream
259 * identifier other than 0. Will be ignored if no SCTP is used.
261 BIO_ctrl(SSL_get_wbio(s
), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE
,
262 st
->in_handshake
, NULL
);
266 /* Initialise state machine */
267 if (st
->state
== MSG_FLOW_UNINITED
268 || st
->state
== MSG_FLOW_FINISHED
) {
269 if (st
->state
== MSG_FLOW_UNINITED
) {
270 st
->hand_state
= TLS_ST_BEFORE
;
271 st
->request_state
= TLS_ST_BEFORE
;
276 cb(s
, SSL_CB_HANDSHAKE_START
, 1);
278 if (SSL_IS_DTLS(s
)) {
279 if ((s
->version
& 0xff00) != (DTLS1_VERSION
& 0xff00) &&
280 (server
|| (s
->version
& 0xff00) != (DTLS1_BAD_VER
& 0xff00))) {
281 SSLerr(SSL_F_STATE_MACHINE
, ERR_R_INTERNAL_ERROR
);
285 if ((s
->version
>> 8) != SSL3_VERSION_MAJOR
) {
286 SSLerr(SSL_F_STATE_MACHINE
, ERR_R_INTERNAL_ERROR
);
291 if (!ssl_security(s
, SSL_SECOP_VERSION
, 0, s
->version
, NULL
)) {
292 SSLerr(SSL_F_STATE_MACHINE
, SSL_R_VERSION_TOO_LOW
);
296 if (s
->init_buf
== NULL
) {
297 if ((buf
= BUF_MEM_new()) == NULL
) {
300 if (!BUF_MEM_grow(buf
, SSL3_RT_MAX_PLAIN_LENGTH
)) {
307 if (!ssl3_setup_buffers(s
)) {
313 * Should have been reset by tls_process_finished, too.
315 s
->s3
->change_cipher_spec
= 0;
318 * Ok, we now need to push on a buffering BIO ...but not with
321 #ifndef OPENSSL_NO_SCTP
322 if (!SSL_IS_DTLS(s
) || !BIO_dgram_is_sctp(SSL_get_wbio(s
)))
324 if (!ssl_init_wbio_buffer(s
)) {
328 if ((SSL_IS_FIRST_HANDSHAKE(s
)
329 && s
->early_data_state
!= SSL_EARLY_DATA_FINISHED_WRITING
330 && s
->early_data_state
!= SSL_EARLY_DATA_FINISHED_READING
)
332 if (!tls_setup_handshake(s
)) {
333 ossl_statem_set_error(s
);
337 if (SSL_IS_FIRST_HANDSHAKE(s
))
338 st
->read_state_first_init
= 1;
341 st
->state
= MSG_FLOW_WRITING
;
342 init_write_state_machine(s
);
345 while (st
->state
!= MSG_FLOW_FINISHED
) {
346 if (st
->state
== MSG_FLOW_READING
) {
347 ssret
= read_state_machine(s
);
348 if (ssret
== SUB_STATE_FINISHED
) {
349 st
->state
= MSG_FLOW_WRITING
;
350 init_write_state_machine(s
);
355 } else if (st
->state
== MSG_FLOW_WRITING
) {
356 ssret
= write_state_machine(s
);
357 if (ssret
== SUB_STATE_FINISHED
) {
358 st
->state
= MSG_FLOW_READING
;
359 init_read_state_machine(s
);
360 } else if (ssret
== SUB_STATE_END_HANDSHAKE
) {
361 st
->state
= MSG_FLOW_FINISHED
;
368 ossl_statem_set_error(s
);
378 #ifndef OPENSSL_NO_SCTP
379 if (SSL_IS_DTLS(s
)) {
381 * Notify SCTP BIO socket to leave handshake mode and allow stream
382 * identifier other than 0. Will be ignored if no SCTP is used.
384 BIO_ctrl(SSL_get_wbio(s
), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE
,
385 st
->in_handshake
, NULL
);
392 cb(s
, SSL_CB_ACCEPT_EXIT
, ret
);
394 cb(s
, SSL_CB_CONNECT_EXIT
, ret
);
400 * Initialise the MSG_FLOW_READING sub-state machine
402 static void init_read_state_machine(SSL
*s
)
404 OSSL_STATEM
*st
= &s
->statem
;
406 st
->read_state
= READ_STATE_HEADER
;
409 static int grow_init_buf(SSL
*s
, size_t size
) {
411 size_t msg_offset
= (char *)s
->init_msg
- s
->init_buf
->data
;
413 if (!BUF_MEM_grow_clean(s
->init_buf
, (int)size
))
416 if (size
< msg_offset
)
419 s
->init_msg
= s
->init_buf
->data
+ msg_offset
;
425 * This function implements the sub-state machine when the message flow is in
426 * MSG_FLOW_READING. The valid sub-states and transitions are:
428 * READ_STATE_HEADER <--+<-------------+
431 * READ_STATE_BODY -----+-->READ_STATE_POST_PROCESS
433 * +----------------------------+
435 * [SUB_STATE_FINISHED]
437 * READ_STATE_HEADER has the responsibility for reading in the message header
438 * and transitioning the state of the handshake state machine.
440 * READ_STATE_BODY reads in the rest of the message and then subsequently
443 * READ_STATE_POST_PROCESS is an optional step that may occur if some post
444 * processing activity performed on the message may block.
446 * Any of the above states could result in an NBIO event occurring in which case
447 * control returns to the calling application. When this function is recalled we
448 * will resume in the same state where we left off.
450 static SUB_STATE_RETURN
read_state_machine(SSL
*s
)
452 OSSL_STATEM
*st
= &s
->statem
;
455 int (*transition
) (SSL
*s
, int mt
);
457 MSG_PROCESS_RETURN(*process_message
) (SSL
*s
, PACKET
*pkt
);
458 WORK_STATE(*post_process_message
) (SSL
*s
, WORK_STATE wst
);
459 size_t (*max_message_size
) (SSL
*s
);
460 void (*cb
) (const SSL
*ssl
, int type
, int val
) = NULL
;
462 cb
= get_callback(s
);
465 transition
= ossl_statem_server_read_transition
;
466 process_message
= ossl_statem_server_process_message
;
467 max_message_size
= ossl_statem_server_max_message_size
;
468 post_process_message
= ossl_statem_server_post_process_message
;
470 transition
= ossl_statem_client_read_transition
;
471 process_message
= ossl_statem_client_process_message
;
472 max_message_size
= ossl_statem_client_max_message_size
;
473 post_process_message
= ossl_statem_client_post_process_message
;
476 if (st
->read_state_first_init
) {
478 st
->read_state_first_init
= 0;
482 switch (st
->read_state
) {
483 case READ_STATE_HEADER
:
484 /* Get the state the peer wants to move to */
485 if (SSL_IS_DTLS(s
)) {
487 * In DTLS we get the whole message in one go - header and body
489 ret
= dtls_get_message(s
, &mt
, &len
);
491 ret
= tls_get_message_header(s
, &mt
);
495 /* Could be non-blocking IO */
496 return SUB_STATE_ERROR
;
500 /* Notify callback of an impending state change */
502 cb(s
, SSL_CB_ACCEPT_LOOP
, 1);
504 cb(s
, SSL_CB_CONNECT_LOOP
, 1);
507 * Validate that we are allowed to move to the new state and move
508 * to that state if so
510 if (!transition(s
, mt
)) {
511 ossl_statem_set_error(s
);
512 return SUB_STATE_ERROR
;
515 if (s
->s3
->tmp
.message_size
> max_message_size(s
)) {
516 ssl3_send_alert(s
, SSL3_AL_FATAL
, SSL_AD_ILLEGAL_PARAMETER
);
517 SSLerr(SSL_F_READ_STATE_MACHINE
, SSL_R_EXCESSIVE_MESSAGE_SIZE
);
518 return SUB_STATE_ERROR
;
521 /* dtls_get_message already did this */
523 && s
->s3
->tmp
.message_size
> 0
524 && !grow_init_buf(s
, s
->s3
->tmp
.message_size
525 + SSL3_HM_HEADER_LENGTH
)) {
526 ssl3_send_alert(s
, SSL3_AL_FATAL
, SSL_AD_INTERNAL_ERROR
);
527 SSLerr(SSL_F_READ_STATE_MACHINE
, ERR_R_BUF_LIB
);
528 return SUB_STATE_ERROR
;
531 st
->read_state
= READ_STATE_BODY
;
534 case READ_STATE_BODY
:
535 if (!SSL_IS_DTLS(s
)) {
536 /* We already got this above for DTLS */
537 ret
= tls_get_message_body(s
, &len
);
539 /* Could be non-blocking IO */
540 return SUB_STATE_ERROR
;
545 if (!PACKET_buf_init(&pkt
, s
->init_msg
, len
)) {
546 ssl3_send_alert(s
, SSL3_AL_FATAL
, SSL_AD_INTERNAL_ERROR
);
547 SSLerr(SSL_F_READ_STATE_MACHINE
, ERR_R_INTERNAL_ERROR
);
548 return SUB_STATE_ERROR
;
550 ret
= process_message(s
, &pkt
);
552 /* Discard the packet data */
556 case MSG_PROCESS_ERROR
:
557 return SUB_STATE_ERROR
;
559 case MSG_PROCESS_FINISHED_READING
:
560 if (SSL_IS_DTLS(s
)) {
563 return SUB_STATE_FINISHED
;
565 case MSG_PROCESS_CONTINUE_PROCESSING
:
566 st
->read_state
= READ_STATE_POST_PROCESS
;
567 st
->read_state_work
= WORK_MORE_A
;
571 st
->read_state
= READ_STATE_HEADER
;
576 case READ_STATE_POST_PROCESS
:
577 st
->read_state_work
= post_process_message(s
, st
->read_state_work
);
578 switch (st
->read_state_work
) {
583 return SUB_STATE_ERROR
;
585 case WORK_FINISHED_CONTINUE
:
586 st
->read_state
= READ_STATE_HEADER
;
589 case WORK_FINISHED_STOP
:
590 if (SSL_IS_DTLS(s
)) {
593 return SUB_STATE_FINISHED
;
598 /* Shouldn't happen */
599 ssl3_send_alert(s
, SSL3_AL_FATAL
, SSL_AD_INTERNAL_ERROR
);
600 SSLerr(SSL_F_READ_STATE_MACHINE
, ERR_R_INTERNAL_ERROR
);
601 ossl_statem_set_error(s
);
602 return SUB_STATE_ERROR
;
608 * Send a previously constructed message to the peer.
610 static int statem_do_write(SSL
*s
)
612 OSSL_STATEM
*st
= &s
->statem
;
614 if (st
->hand_state
== TLS_ST_CW_CHANGE
615 || st
->hand_state
== TLS_ST_SW_CHANGE
) {
617 return dtls1_do_write(s
, SSL3_RT_CHANGE_CIPHER_SPEC
);
619 return ssl3_do_write(s
, SSL3_RT_CHANGE_CIPHER_SPEC
);
621 return ssl_do_write(s
);
626 * Initialise the MSG_FLOW_WRITING sub-state machine
628 static void init_write_state_machine(SSL
*s
)
630 OSSL_STATEM
*st
= &s
->statem
;
632 st
->write_state
= WRITE_STATE_TRANSITION
;
636 * This function implements the sub-state machine when the message flow is in
637 * MSG_FLOW_WRITING. The valid sub-states and transitions are:
639 * +-> WRITE_STATE_TRANSITION ------> [SUB_STATE_FINISHED]
642 * | WRITE_STATE_PRE_WORK -----> [SUB_STATE_END_HANDSHAKE]
648 * | WRITE_STATE_POST_WORK
652 * WRITE_STATE_TRANSITION transitions the state of the handshake state machine
654 * WRITE_STATE_PRE_WORK performs any work necessary to prepare the later
655 * sending of the message. This could result in an NBIO event occurring in
656 * which case control returns to the calling application. When this function
657 * is recalled we will resume in the same state where we left off.
659 * WRITE_STATE_SEND sends the message and performs any work to be done after
662 * WRITE_STATE_POST_WORK performs any work necessary after the sending of the
663 * message has been completed. As for WRITE_STATE_PRE_WORK this could also
664 * result in an NBIO event.
666 static SUB_STATE_RETURN
write_state_machine(SSL
*s
)
668 OSSL_STATEM
*st
= &s
->statem
;
670 WRITE_TRAN(*transition
) (SSL
*s
);
671 WORK_STATE(*pre_work
) (SSL
*s
, WORK_STATE wst
);
672 WORK_STATE(*post_work
) (SSL
*s
, WORK_STATE wst
);
673 int (*get_construct_message_f
) (SSL
*s
, WPACKET
*pkt
,
674 int (**confunc
) (SSL
*s
, WPACKET
*pkt
),
676 void (*cb
) (const SSL
*ssl
, int type
, int val
) = NULL
;
677 int (*confunc
) (SSL
*s
, WPACKET
*pkt
);
681 cb
= get_callback(s
);
684 transition
= ossl_statem_server_write_transition
;
685 pre_work
= ossl_statem_server_pre_work
;
686 post_work
= ossl_statem_server_post_work
;
687 get_construct_message_f
= ossl_statem_server_construct_message
;
689 transition
= ossl_statem_client_write_transition
;
690 pre_work
= ossl_statem_client_pre_work
;
691 post_work
= ossl_statem_client_post_work
;
692 get_construct_message_f
= ossl_statem_client_construct_message
;
696 switch (st
->write_state
) {
697 case WRITE_STATE_TRANSITION
:
699 /* Notify callback of an impending state change */
701 cb(s
, SSL_CB_ACCEPT_LOOP
, 1);
703 cb(s
, SSL_CB_CONNECT_LOOP
, 1);
705 switch (transition(s
)) {
706 case WRITE_TRAN_CONTINUE
:
707 st
->write_state
= WRITE_STATE_PRE_WORK
;
708 st
->write_state_work
= WORK_MORE_A
;
711 case WRITE_TRAN_FINISHED
:
712 return SUB_STATE_FINISHED
;
715 case WRITE_TRAN_ERROR
:
716 return SUB_STATE_ERROR
;
720 case WRITE_STATE_PRE_WORK
:
721 switch (st
->write_state_work
= pre_work(s
, st
->write_state_work
)) {
726 return SUB_STATE_ERROR
;
728 case WORK_FINISHED_CONTINUE
:
729 st
->write_state
= WRITE_STATE_SEND
;
732 case WORK_FINISHED_STOP
:
733 return SUB_STATE_END_HANDSHAKE
;
735 if (!WPACKET_init(&pkt
, s
->init_buf
)
736 || !get_construct_message_f(s
, &pkt
, &confunc
, &mt
)
737 || !ssl_set_handshake_header(s
, &pkt
, mt
)
738 || (confunc
!= NULL
&& !confunc(s
, &pkt
))
739 || !ssl_close_construct_packet(s
, &pkt
, mt
)
740 || !WPACKET_finish(&pkt
)) {
741 WPACKET_cleanup(&pkt
);
742 ossl_statem_set_error(s
);
743 return SUB_STATE_ERROR
;
748 case WRITE_STATE_SEND
:
749 if (SSL_IS_DTLS(s
) && st
->use_timer
) {
750 dtls1_start_timer(s
);
752 ret
= statem_do_write(s
);
754 return SUB_STATE_ERROR
;
756 st
->write_state
= WRITE_STATE_POST_WORK
;
757 st
->write_state_work
= WORK_MORE_A
;
760 case WRITE_STATE_POST_WORK
:
761 switch (st
->write_state_work
= post_work(s
, st
->write_state_work
)) {
766 return SUB_STATE_ERROR
;
768 case WORK_FINISHED_CONTINUE
:
769 st
->write_state
= WRITE_STATE_TRANSITION
;
772 case WORK_FINISHED_STOP
:
773 return SUB_STATE_END_HANDSHAKE
;
778 return SUB_STATE_ERROR
;
784 * Flush the write BIO
786 int statem_flush(SSL
*s
)
788 s
->rwstate
= SSL_WRITING
;
789 if (BIO_flush(s
->wbio
) <= 0) {
792 s
->rwstate
= SSL_NOTHING
;
798 * Called by the record layer to determine whether application data is
799 * allowed to be received in the current handshake state or not.
802 * 1: Yes (application data allowed)
803 * 0: No (application data not allowed)
805 int ossl_statem_app_data_allowed(SSL
*s
)
807 OSSL_STATEM
*st
= &s
->statem
;
809 if (st
->state
== MSG_FLOW_UNINITED
)
812 if (!s
->s3
->in_read_app_data
|| (s
->s3
->total_renegotiations
== 0))
817 * If we're a server and we haven't got as far as writing our
818 * ServerHello yet then we allow app data
820 if (st
->hand_state
== TLS_ST_BEFORE
821 || st
->hand_state
== TLS_ST_SR_CLNT_HELLO
)
825 * If we're a client and we haven't read the ServerHello yet then we
828 if (st
->hand_state
== TLS_ST_CW_CLNT_HELLO
)
835 #ifndef OPENSSL_NO_SCTP
837 * Set flag used by SCTP to determine whether we are in the read sock state
839 void ossl_statem_set_sctp_read_sock(SSL
*s
, int read_sock
)
841 s
->statem
.in_sctp_read_sock
= read_sock
;
845 * Called by the record layer to determine whether we are in the read sock
849 * 1: Yes (we are in the read sock state)
850 * 0: No (we are not in the read sock state)
852 int ossl_statem_in_sctp_read_sock(SSL
*s
)
854 return s
->statem
.in_sctp_read_sock
;