/* * Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the OpenSSL license (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy * in the file LICENSE in the source distribution or at * https://www.openssl.org/source/license.html */ #include #include "../ssl_locl.h" #include "statem_locl.h" /* * This file implements the SSL/TLS/DTLS state machines. * * There are two primary state machines: * * 1) Message flow state machine * 2) Handshake state machine * * The Message flow state machine controls the reading and sending of messages * including handling of non-blocking IO events, flushing of the underlying * write BIO, handling unexpected messages, etc. It is itself broken into two * separate sub-state machines which control reading and writing respectively. * * The Handshake state machine keeps track of the current SSL/TLS handshake * state. Transitions of the handshake state are the result of events that * occur within the Message flow state machine. * * Overall it looks like this: * * --------------------------------------------- ------------------- * | | | | * | Message flow state machine | | | * | | | | * | -------------------- -------------------- | Transition | Handshake state | * | | MSG_FLOW_READING | | MSG_FLOW_WRITING | | Event | machine | * | | sub-state | | sub-state | |----------->| | * | | machine for | | machine for | | | | * | | reading messages | | writing messages | | | | * | -------------------- -------------------- | | | * | | | | * --------------------------------------------- ------------------- * */ /* Sub state machine return values */ typedef enum { /* Something bad happened or NBIO */ SUB_STATE_ERROR, /* Sub state finished go to the next sub state */ SUB_STATE_FINISHED, /* Sub state finished and handshake was completed */ SUB_STATE_END_HANDSHAKE } SUB_STATE_RETURN; static int state_machine(SSL *s, int server); static void init_read_state_machine(SSL *s); static SUB_STATE_RETURN read_state_machine(SSL *s); static void init_write_state_machine(SSL *s); static SUB_STATE_RETURN write_state_machine(SSL *s); OSSL_HANDSHAKE_STATE SSL_get_state(const SSL *ssl) { return ssl->statem.hand_state; } int SSL_in_init(SSL *s) { return s->statem.in_init; } int SSL_is_init_finished(SSL *s) { return !(s->statem.in_init) && (s->statem.hand_state == TLS_ST_OK); } int SSL_in_before(SSL *s) { /* * Historically being "in before" meant before anything had happened. In the * current code though we remain in the "before" state for a while after we * have started the handshake process (e.g. as a server waiting for the * first message to arrive). There "in before" is taken to mean "in before" * and not started any handshake process yet. */ return (s->statem.hand_state == TLS_ST_BEFORE) && (s->statem.state == MSG_FLOW_UNINITED); } /* * Clear the state machine state and reset back to MSG_FLOW_UNINITED */ void ossl_statem_clear(SSL *s) { s->statem.state = MSG_FLOW_UNINITED; s->statem.hand_state = TLS_ST_BEFORE; s->statem.in_init = 1; s->statem.no_cert_verify = 0; } /* * Set the state machine up ready for a renegotiation handshake */ void ossl_statem_set_renegotiate(SSL *s) { s->statem.state = MSG_FLOW_RENEGOTIATE; s->statem.in_init = 1; } /* * Put the state machine into an error state. This is a permanent error for * the current connection. */ void ossl_statem_set_error(SSL *s) { s->statem.state = MSG_FLOW_ERROR; } /* * Discover whether the current connection is in the error state. * * Valid return values are: * 1: Yes * 0: No */ int ossl_statem_in_error(const SSL *s) { if (s->statem.state == MSG_FLOW_ERROR) return 1; return 0; } void ossl_statem_set_in_init(SSL *s, int init) { s->statem.in_init = init; } int ossl_statem_get_in_handshake(SSL *s) { return s->statem.in_handshake; } void ossl_statem_set_in_handshake(SSL *s, int inhand) { if (inhand) s->statem.in_handshake++; else s->statem.in_handshake--; } void ossl_statem_set_hello_verify_done(SSL *s) { s->statem.state = MSG_FLOW_UNINITED; s->statem.in_init = 1; /* * This will get reset (briefly) back to TLS_ST_BEFORE when we enter * state_machine() because |state| is MSG_FLOW_UNINITED, but until then any * calls to SSL_in_before() will return false. Also calls to * SSL_state_string() and SSL_state_string_long() will return something * sensible. */ s->statem.hand_state = TLS_ST_SR_CLNT_HELLO; } int ossl_statem_connect(SSL *s) { return state_machine(s, 0); } int ossl_statem_accept(SSL *s) { return state_machine(s, 1); } typedef void (*info_cb) (const SSL *, int, int); static info_cb get_callback(SSL *s) { if (s->info_callback != NULL) return s->info_callback; else if (s->ctx->info_callback != NULL) return s->ctx->info_callback; return NULL; } /* * The main message flow state machine. We start in the MSG_FLOW_UNINITED or * MSG_FLOW_RENEGOTIATE state and finish in MSG_FLOW_FINISHED. Valid states and * transitions are as follows: * * MSG_FLOW_UNINITED MSG_FLOW_RENEGOTIATE * | | * +-----------------------+ * v * MSG_FLOW_WRITING <---> MSG_FLOW_READING * | * V * MSG_FLOW_FINISHED * | * V * [SUCCESS] * * We may exit at any point due to an error or NBIO event. If an NBIO event * occurs then we restart at the point we left off when we are recalled. * MSG_FLOW_WRITING and MSG_FLOW_READING have sub-state machines associated with them. * * In addition to the above there is also the MSG_FLOW_ERROR state. We can move * into that state at any point in the event that an irrecoverable error occurs. * * Valid return values are: * 1: Success * <=0: NBIO or error */ static int state_machine(SSL *s, int server) { BUF_MEM *buf = NULL; unsigned long Time = (unsigned long)time(NULL); void (*cb) (const SSL *ssl, int type, int val) = NULL; OSSL_STATEM *st = &s->statem; int ret = -1; int ssret; if (st->state == MSG_FLOW_ERROR) { /* Shouldn't have been called if we're already in the error state */ return -1; } RAND_add(&Time, sizeof(Time), 0); ERR_clear_error(); clear_sys_error(); cb = get_callback(s); st->in_handshake++; if (!SSL_in_init(s) || SSL_in_before(s)) { if (!SSL_clear(s)) return -1; } #ifndef OPENSSL_NO_SCTP if (SSL_IS_DTLS(s)) { /* * Notify SCTP BIO socket to enter handshake mode and prevent stream * identifier other than 0. Will be ignored if no SCTP is used. */ BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE, st->in_handshake, NULL); } #endif #ifndef OPENSSL_NO_HEARTBEATS /* * If we're awaiting a HeartbeatResponse, pretend we already got and * don't await it anymore, because Heartbeats don't make sense during * handshakes anyway. */ if (s->tlsext_hb_pending) { if (SSL_IS_DTLS(s)) dtls1_stop_timer(s); s->tlsext_hb_pending = 0; s->tlsext_hb_seq++; } #endif /* Initialise state machine */ if (st->state == MSG_FLOW_RENEGOTIATE) { s->renegotiate = 1; if (!server) s->ctx->stats.sess_connect_renegotiate++; } if (st->state == MSG_FLOW_UNINITED || st->state == MSG_FLOW_RENEGOTIATE) { if (st->state == MSG_FLOW_UNINITED) { st->hand_state = TLS_ST_BEFORE; } s->server = server; if (cb != NULL) cb(s, SSL_CB_HANDSHAKE_START, 1); if (SSL_IS_DTLS(s)) { if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00) && (server || (s->version & 0xff00) != (DTLS1_BAD_VER & 0xff00))) { SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR); goto end; } } else { if ((s->version >> 8) != SSL3_VERSION_MAJOR) { SSLerr(SSL_F_STATE_MACHINE, ERR_R_INTERNAL_ERROR); goto end; } } if (!ssl_security(s, SSL_SECOP_VERSION, 0, s->version, NULL)) { SSLerr(SSL_F_STATE_MACHINE, SSL_R_VERSION_TOO_LOW); goto end; } if (s->init_buf == NULL) { if ((buf = BUF_MEM_new()) == NULL) { goto end; } if (!BUF_MEM_grow(buf, SSL3_RT_MAX_PLAIN_LENGTH)) { goto end; } s->init_buf = buf; buf = NULL; } if (!ssl3_setup_buffers(s)) { goto end; } s->init_num = 0; /* * Should have been reset by tls_process_finished, too. */ s->s3->change_cipher_spec = 0; /* * Ok, we now need to push on a buffering BIO ...but not with * SCTP */ #ifndef OPENSSL_NO_SCTP if (!SSL_IS_DTLS(s) || !BIO_dgram_is_sctp(SSL_get_wbio(s))) #endif if (!ssl_init_wbio_buffer(s)) { goto end; } if (!server || st->state != MSG_FLOW_RENEGOTIATE) { if (!ssl3_init_finished_mac(s)) { ossl_statem_set_error(s); goto end; } } if (server) { if (st->state != MSG_FLOW_RENEGOTIATE) { s->ctx->stats.sess_accept++; } else if (!s->s3->send_connection_binding && !(s->options & SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION)) { /* * Server attempting to renegotiate with client that doesn't * support secure renegotiation. */ SSLerr(SSL_F_STATE_MACHINE, SSL_R_UNSAFE_LEGACY_RENEGOTIATION_DISABLED); ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_HANDSHAKE_FAILURE); ossl_statem_set_error(s); goto end; } else { /* * st->state == MSG_FLOW_RENEGOTIATE, we will just send a * HelloRequest */ s->ctx->stats.sess_accept_renegotiate++; } } else { s->ctx->stats.sess_connect++; /* mark client_random uninitialized */ memset(s->s3->client_random, 0, sizeof(s->s3->client_random)); s->hit = 0; s->s3->tmp.cert_request = 0; if (SSL_IS_DTLS(s)) { st->use_timer = 1; } } st->state = MSG_FLOW_WRITING; init_write_state_machine(s); st->read_state_first_init = 1; } while (st->state != MSG_FLOW_FINISHED) { if (st->state == MSG_FLOW_READING) { ssret = read_state_machine(s); if (ssret == SUB_STATE_FINISHED) { st->state = MSG_FLOW_WRITING; init_write_state_machine(s); } else { /* NBIO or error */ goto end; } } else if (st->state == MSG_FLOW_WRITING) { ssret = write_state_machine(s); if (ssret == SUB_STATE_FINISHED) { st->state = MSG_FLOW_READING; init_read_state_machine(s); } else if (ssret == SUB_STATE_END_HANDSHAKE) { st->state = MSG_FLOW_FINISHED; } else { /* NBIO or error */ goto end; } } else { /* Error */ ossl_statem_set_error(s); goto end; } } st->state = MSG_FLOW_UNINITED; ret = 1; end: st->in_handshake--; #ifndef OPENSSL_NO_SCTP if (SSL_IS_DTLS(s)) { /* * Notify SCTP BIO socket to leave handshake mode and allow stream * identifier other than 0. Will be ignored if no SCTP is used. */ BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE, st->in_handshake, NULL); } #endif BUF_MEM_free(buf); if (cb != NULL) { if (server) cb(s, SSL_CB_ACCEPT_EXIT, ret); else cb(s, SSL_CB_CONNECT_EXIT, ret); } return ret; } /* * Initialise the MSG_FLOW_READING sub-state machine */ static void init_read_state_machine(SSL *s) { OSSL_STATEM *st = &s->statem; st->read_state = READ_STATE_HEADER; } static int grow_init_buf(SSL *s, size_t size) { size_t msg_offset = (char *)s->init_msg - s->init_buf->data; if (!BUF_MEM_grow_clean(s->init_buf, (int)size)) return 0; if (size < msg_offset) return 0; s->init_msg = s->init_buf->data + msg_offset; return 1; } /* * This function implements the sub-state machine when the message flow is in * MSG_FLOW_READING. The valid sub-states and transitions are: * * READ_STATE_HEADER <--+<-------------+ * | | | * v | | * READ_STATE_BODY -----+-->READ_STATE_POST_PROCESS * | | * +----------------------------+ * v * [SUB_STATE_FINISHED] * * READ_STATE_HEADER has the responsibility for reading in the message header * and transitioning the state of the handshake state machine. * * READ_STATE_BODY reads in the rest of the message and then subsequently * processes it. * * READ_STATE_POST_PROCESS is an optional step that may occur if some post * processing activity performed on the message may block. * * Any of the above states could result in an NBIO event occurring in which case * control returns to the calling application. When this function is recalled we * will resume in the same state where we left off. */ static SUB_STATE_RETURN read_state_machine(SSL *s) { OSSL_STATEM *st = &s->statem; int ret, mt; unsigned long len = 0; int (*transition) (SSL *s, int mt); PACKET pkt; MSG_PROCESS_RETURN(*process_message) (SSL *s, PACKET *pkt); WORK_STATE(*post_process_message) (SSL *s, WORK_STATE wst); unsigned long (*max_message_size) (SSL *s); void (*cb) (const SSL *ssl, int type, int val) = NULL; cb = get_callback(s); if (s->server) { transition = ossl_statem_server_read_transition; process_message = ossl_statem_server_process_message; max_message_size = ossl_statem_server_max_message_size; post_process_message = ossl_statem_server_post_process_message; } else { transition = ossl_statem_client_read_transition; process_message = ossl_statem_client_process_message; max_message_size = ossl_statem_client_max_message_size; post_process_message = ossl_statem_client_post_process_message; } if (st->read_state_first_init) { s->first_packet = 1; st->read_state_first_init = 0; } while (1) { switch (st->read_state) { case READ_STATE_HEADER: /* Get the state the peer wants to move to */ if (SSL_IS_DTLS(s)) { /* * In DTLS we get the whole message in one go - header and body */ ret = dtls_get_message(s, &mt, &len); } else { ret = tls_get_message_header(s, &mt); } if (ret == 0) { /* Could be non-blocking IO */ return SUB_STATE_ERROR; } if (cb != NULL) { /* Notify callback of an impending state change */ if (s->server) cb(s, SSL_CB_ACCEPT_LOOP, 1); else cb(s, SSL_CB_CONNECT_LOOP, 1); } /* * Validate that we are allowed to move to the new state and move * to that state if so */ if (!transition(s, mt)) { ossl_statem_set_error(s); return SUB_STATE_ERROR; } if (s->s3->tmp.message_size > max_message_size(s)) { ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER); SSLerr(SSL_F_READ_STATE_MACHINE, SSL_R_EXCESSIVE_MESSAGE_SIZE); return SUB_STATE_ERROR; } /* dtls_get_message already did this */ if (!SSL_IS_DTLS(s) && s->s3->tmp.message_size > 0 && !grow_init_buf(s, s->s3->tmp.message_size + SSL3_HM_HEADER_LENGTH)) { ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR); SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_BUF_LIB); return SUB_STATE_ERROR; } st->read_state = READ_STATE_BODY; /* Fall through */ case READ_STATE_BODY: if (!SSL_IS_DTLS(s)) { /* We already got this above for DTLS */ ret = tls_get_message_body(s, &len); if (ret == 0) { /* Could be non-blocking IO */ return SUB_STATE_ERROR; } } s->first_packet = 0; if (!PACKET_buf_init(&pkt, s->init_msg, len)) { ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR); SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR); return SUB_STATE_ERROR; } ret = process_message(s, &pkt); /* Discard the packet data */ s->init_num = 0; switch (ret) { case MSG_PROCESS_ERROR: return SUB_STATE_ERROR; case MSG_PROCESS_FINISHED_READING: if (SSL_IS_DTLS(s)) { dtls1_stop_timer(s); } return SUB_STATE_FINISHED; case MSG_PROCESS_CONTINUE_PROCESSING: st->read_state = READ_STATE_POST_PROCESS; st->read_state_work = WORK_MORE_A; break; default: st->read_state = READ_STATE_HEADER; break; } break; case READ_STATE_POST_PROCESS: st->read_state_work = post_process_message(s, st->read_state_work); switch (st->read_state_work) { case WORK_ERROR: case WORK_MORE_A: case WORK_MORE_B: return SUB_STATE_ERROR; case WORK_FINISHED_CONTINUE: st->read_state = READ_STATE_HEADER; break; case WORK_FINISHED_STOP: if (SSL_IS_DTLS(s)) { dtls1_stop_timer(s); } return SUB_STATE_FINISHED; } break; default: /* Shouldn't happen */ ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR); SSLerr(SSL_F_READ_STATE_MACHINE, ERR_R_INTERNAL_ERROR); ossl_statem_set_error(s); return SUB_STATE_ERROR; } } } /* * Send a previously constructed message to the peer. */ static int statem_do_write(SSL *s) { OSSL_STATEM *st = &s->statem; if (st->hand_state == TLS_ST_CW_CHANGE || st->hand_state == TLS_ST_SW_CHANGE) { if (SSL_IS_DTLS(s)) return dtls1_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC); else return ssl3_do_write(s, SSL3_RT_CHANGE_CIPHER_SPEC); } else { return ssl_do_write(s); } } /* * Initialise the MSG_FLOW_WRITING sub-state machine */ static void init_write_state_machine(SSL *s) { OSSL_STATEM *st = &s->statem; st->write_state = WRITE_STATE_TRANSITION; } /* * This function implements the sub-state machine when the message flow is in * MSG_FLOW_WRITING. The valid sub-states and transitions are: * * +-> WRITE_STATE_TRANSITION ------> [SUB_STATE_FINISHED] * | | * | v * | WRITE_STATE_PRE_WORK -----> [SUB_STATE_END_HANDSHAKE] * | | * | v * | WRITE_STATE_SEND * | | * | v * | WRITE_STATE_POST_WORK * | | * +-------------+ * * WRITE_STATE_TRANSITION transitions the state of the handshake state machine * WRITE_STATE_PRE_WORK performs any work necessary to prepare the later * sending of the message. This could result in an NBIO event occurring in * which case control returns to the calling application. When this function * is recalled we will resume in the same state where we left off. * * WRITE_STATE_SEND sends the message and performs any work to be done after * sending. * * WRITE_STATE_POST_WORK performs any work necessary after the sending of the * message has been completed. As for WRITE_STATE_PRE_WORK this could also * result in an NBIO event. */ static SUB_STATE_RETURN write_state_machine(SSL *s) { OSSL_STATEM *st = &s->statem; int ret; WRITE_TRAN(*transition) (SSL *s); WORK_STATE(*pre_work) (SSL *s, WORK_STATE wst); WORK_STATE(*post_work) (SSL *s, WORK_STATE wst); int (*construct_message) (SSL *s, WPACKET *pkt); void (*cb) (const SSL *ssl, int type, int val) = NULL; WPACKET pkt; cb = get_callback(s); if (s->server) { transition = ossl_statem_server_write_transition; pre_work = ossl_statem_server_pre_work; post_work = ossl_statem_server_post_work; construct_message = ossl_statem_server_construct_message; } else { transition = ossl_statem_client_write_transition; pre_work = ossl_statem_client_pre_work; post_work = ossl_statem_client_post_work; construct_message = ossl_statem_client_construct_message; } while (1) { switch (st->write_state) { case WRITE_STATE_TRANSITION: if (cb != NULL) { /* Notify callback of an impending state change */ if (s->server) cb(s, SSL_CB_ACCEPT_LOOP, 1); else cb(s, SSL_CB_CONNECT_LOOP, 1); } switch (transition(s)) { case WRITE_TRAN_CONTINUE: st->write_state = WRITE_STATE_PRE_WORK; st->write_state_work = WORK_MORE_A; break; case WRITE_TRAN_FINISHED: return SUB_STATE_FINISHED; break; case WRITE_TRAN_ERROR: return SUB_STATE_ERROR; } break; case WRITE_STATE_PRE_WORK: switch (st->write_state_work = pre_work(s, st->write_state_work)) { case WORK_ERROR: case WORK_MORE_A: case WORK_MORE_B: return SUB_STATE_ERROR; case WORK_FINISHED_CONTINUE: st->write_state = WRITE_STATE_SEND; break; case WORK_FINISHED_STOP: return SUB_STATE_END_HANDSHAKE; } if (!WPACKET_init(&pkt, s->init_buf) || !construct_message(s, &pkt) || !WPACKET_finish(&pkt)) { WPACKET_cleanup(&pkt); ossl_statem_set_error(s); return SUB_STATE_ERROR; } /* Fall through */ case WRITE_STATE_SEND: if (SSL_IS_DTLS(s) && st->use_timer) { dtls1_start_timer(s); } ret = statem_do_write(s); if (ret <= 0) { return SUB_STATE_ERROR; } st->write_state = WRITE_STATE_POST_WORK; st->write_state_work = WORK_MORE_A; /* Fall through */ case WRITE_STATE_POST_WORK: switch (st->write_state_work = post_work(s, st->write_state_work)) { case WORK_ERROR: case WORK_MORE_A: case WORK_MORE_B: return SUB_STATE_ERROR; case WORK_FINISHED_CONTINUE: st->write_state = WRITE_STATE_TRANSITION; break; case WORK_FINISHED_STOP: return SUB_STATE_END_HANDSHAKE; } break; default: return SUB_STATE_ERROR; } } } /* * Flush the write BIO */ int statem_flush(SSL *s) { s->rwstate = SSL_WRITING; if (BIO_flush(s->wbio) <= 0) { return 0; } s->rwstate = SSL_NOTHING; return 1; } /* * Called by the record layer to determine whether application data is * allowed to be sent in the current handshake state or not. * * Return values are: * 1: Yes (application data allowed) * 0: No (application data not allowed) */ int ossl_statem_app_data_allowed(SSL *s) { OSSL_STATEM *st = &s->statem; if (st->state == MSG_FLOW_UNINITED || st->state == MSG_FLOW_RENEGOTIATE) return 0; if (!s->s3->in_read_app_data || (s->s3->total_renegotiations == 0)) return 0; if (s->server) { /* * If we're a server and we haven't got as far as writing our * ServerHello yet then we allow app data */ if (st->hand_state == TLS_ST_BEFORE || st->hand_state == TLS_ST_SR_CLNT_HELLO) return 1; } else { /* * If we're a client and we haven't read the ServerHello yet then we * allow app data */ if (st->hand_state == TLS_ST_CW_CLNT_HELLO) return 1; } return 0; } #ifndef OPENSSL_NO_SCTP /* * Set flag used by SCTP to determine whether we are in the read sock state */ void ossl_statem_set_sctp_read_sock(SSL *s, int read_sock) { s->statem.in_sctp_read_sock = read_sock; } /* * Called by the record layer to determine whether we are in the read sock * state or not. * * Return values are: * 1: Yes (we are in the read sock state) * 0: No (we are not in the read sock state) */ int ossl_statem_in_sctp_read_sock(SSL *s) { return s->statem.in_sctp_read_sock; } #endif