path: root/contrib/libs/openssl/ssl/statem/statem.c

/* 
 * Copyright 2015-2019 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 "internal/cryptlib.h" 
#include <openssl/rand.h> 
#include "../ssl_local.h"
#include "statem_local.h"
#include <assert.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(const SSL *s) 
{ 
    return s->statem.in_init; 
} 
 
int SSL_is_init_finished(const SSL *s) 
{ 
    return !(s->statem.in_init) && (s->statem.hand_state == TLS_ST_OK); 
} 
 
int SSL_in_before(const 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.in_init = 1; 
    s->statem.request_state = TLS_ST_SW_HELLO_REQ; 
} 
 
/* 
 * Put the state machine into an error state and send an alert if appropriate. 
 * This is a permanent error for the current connection. 
 */ 
void ossl_statem_fatal(SSL *s, int al, int func, int reason, const char *file, 
                       int line) 
{ 
    ERR_put_error(ERR_LIB_SSL, func, reason, file, line); 
    /* We shouldn't call SSLfatal() twice. Once is enough */ 
    if (s->statem.in_init && s->statem.state == MSG_FLOW_ERROR) 
      return; 
    s->statem.in_init = 1; 
    s->statem.state = MSG_FLOW_ERROR; 
    if (al != SSL_AD_NO_ALERT 
            && s->statem.enc_write_state != ENC_WRITE_STATE_INVALID) 
        ssl3_send_alert(s, SSL3_AL_FATAL, al); 
} 
 
/* 
 * This macro should only be called if we are already expecting to be in 
 * a fatal error state. We verify that we are, and set it if not (this would 
 * indicate a bug). 
 */ 
#define check_fatal(s, f) \ 
    do { \ 
        if (!ossl_assert((s)->statem.in_init \ 
                         && (s)->statem.state == MSG_FLOW_ERROR)) \ 
            SSLfatal(s, SSL_AD_INTERNAL_ERROR, (f), \ 
                     SSL_R_MISSING_FATAL); \ 
    } while (0) 
 
/* 
 * 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--; 
} 
 
/* Are we in a sensible state to skip over unreadable early data? */ 
int ossl_statem_skip_early_data(SSL *s) 
{ 
    if (s->ext.early_data != SSL_EARLY_DATA_REJECTED) 
        return 0; 
 
    if (!s->server 
            || s->statem.hand_state != TLS_ST_EARLY_DATA 
            || s->hello_retry_request == SSL_HRR_COMPLETE) 
        return 0; 
 
    return 1; 
} 
 
/* 
 * Called when we are in SSL_read*(), SSL_write*(), or SSL_accept() 
 * /SSL_connect()/SSL_do_handshake(). Used to test whether we are in an early 
 * data state and whether we should attempt to move the handshake on if so. 
 * |sending| is 1 if we are attempting to send data (SSL_write*()), 0 if we are 
 * attempting to read data (SSL_read*()), or -1 if we are in SSL_do_handshake() 
 * or similar. 
 */ 
void ossl_statem_check_finish_init(SSL *s, int sending) 
{ 
    if (sending == -1) { 
        if (s->statem.hand_state == TLS_ST_PENDING_EARLY_DATA_END 
                || s->statem.hand_state == TLS_ST_EARLY_DATA) { 
            ossl_statem_set_in_init(s, 1); 
            if (s->early_data_state == SSL_EARLY_DATA_WRITE_RETRY) { 
                /* 
                 * SSL_connect() or SSL_do_handshake() has been called directly. 
                 * We don't allow any more writing of early data. 
                 */ 
                s->early_data_state = SSL_EARLY_DATA_FINISHED_WRITING; 
            } 
        } 
    } else if (!s->server) { 
        if ((sending && (s->statem.hand_state == TLS_ST_PENDING_EARLY_DATA_END 
                      || s->statem.hand_state == TLS_ST_EARLY_DATA) 
                  && s->early_data_state != SSL_EARLY_DATA_WRITING) 
                || (!sending && s->statem.hand_state == TLS_ST_EARLY_DATA)) { 
            ossl_statem_set_in_init(s, 1); 
            /* 
             * SSL_write() has been called directly. We don't allow any more 
             * writing of early data. 
             */ 
            if (sending && s->early_data_state == SSL_EARLY_DATA_WRITE_RETRY) 
                s->early_data_state = SSL_EARLY_DATA_FINISHED_WRITING; 
        } 
    } else { 
        if (s->early_data_state == SSL_EARLY_DATA_FINISHED_READING 
                && s->statem.hand_state == TLS_ST_EARLY_DATA) 
            ossl_statem_set_in_init(s, 1); 
    } 
} 
 
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_FINISHED state and finish in MSG_FLOW_FINISHED. Valid states and 
 * transitions are as follows: 
 * 
 * MSG_FLOW_UNINITED     MSG_FLOW_FINISHED 
 *        |                       | 
 *        +-----------------------+ 
 *        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; 
    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; 
    } 
 
    ERR_clear_error(); 
    clear_sys_error(); 
 
    cb = get_callback(s); 
 
    st->in_handshake++; 
    if (!SSL_in_init(s) || SSL_in_before(s)) { 
        /* 
         * If we are stateless then we already called SSL_clear() - don't do 
         * it again and clear the STATELESS flag itself. 
         */ 
        if ((s->s3->flags & TLS1_FLAGS_STATELESS) == 0 && !SSL_clear(s)) 
            return -1; 
    } 
#ifndef OPENSSL_NO_SCTP 
    if (SSL_IS_DTLS(s) && BIO_dgram_is_sctp(SSL_get_wbio(s))) { 
        /* 
         * Notify SCTP BIO socket to enter handshake mode and prevent stream 
         * identifier other than 0. 
         */ 
        BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE, 
                 st->in_handshake, NULL); 
    } 
#endif 
 
    /* Initialise state machine */ 
    if (st->state == MSG_FLOW_UNINITED 
            || st->state == MSG_FLOW_FINISHED) { 
        if (st->state == MSG_FLOW_UNINITED) { 
            st->hand_state = TLS_ST_BEFORE; 
            st->request_state = TLS_ST_BEFORE; 
        } 
 
        s->server = server; 
        if (cb != NULL) { 
            if (SSL_IS_FIRST_HANDSHAKE(s) || !SSL_IS_TLS13(s)) 
                cb(s, SSL_CB_HANDSHAKE_START, 1); 
        } 
 
        /* 
         * Fatal errors in this block don't send an alert because we have 
         * failed to even initialise properly. Sending an alert is probably 
         * doomed to failure. 
         */ 
 
        if (SSL_IS_DTLS(s)) { 
            if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00) && 
                (server || (s->version & 0xff00) != (DTLS1_BAD_VER & 0xff00))) { 
                SSLfatal(s, SSL_AD_NO_ALERT, SSL_F_STATE_MACHINE, 
                         ERR_R_INTERNAL_ERROR); 
                goto end; 
            } 
        } else { 
            if ((s->version >> 8) != SSL3_VERSION_MAJOR) { 
                SSLfatal(s, SSL_AD_NO_ALERT, SSL_F_STATE_MACHINE, 
                         ERR_R_INTERNAL_ERROR); 
                goto end; 
            } 
        } 
 
        if (!ssl_security(s, SSL_SECOP_VERSION, 0, s->version, NULL)) { 
            SSLfatal(s, SSL_AD_NO_ALERT, SSL_F_STATE_MACHINE, 
                     ERR_R_INTERNAL_ERROR); 
            goto end; 
        } 
 
        if (s->init_buf == NULL) { 
            if ((buf = BUF_MEM_new()) == NULL) { 
                SSLfatal(s, SSL_AD_NO_ALERT, SSL_F_STATE_MACHINE, 
                         ERR_R_INTERNAL_ERROR); 
                goto end; 
            } 
            if (!BUF_MEM_grow(buf, SSL3_RT_MAX_PLAIN_LENGTH)) { 
                SSLfatal(s, SSL_AD_NO_ALERT, SSL_F_STATE_MACHINE, 
                         ERR_R_INTERNAL_ERROR); 
                goto end; 
            } 
            s->init_buf = buf; 
            buf = NULL; 
        } 
 
        if (!ssl3_setup_buffers(s)) { 
            SSLfatal(s, SSL_AD_NO_ALERT, SSL_F_STATE_MACHINE, 
                     ERR_R_INTERNAL_ERROR); 
            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)) { 
                SSLfatal(s, SSL_AD_NO_ALERT, SSL_F_STATE_MACHINE, 
                         ERR_R_INTERNAL_ERROR); 
                goto end; 
            } 
 
        if ((SSL_in_before(s)) 
                || s->renegotiate) { 
            if (!tls_setup_handshake(s)) { 
                /* SSLfatal() already called */ 
                goto end; 
            } 
 
            if (SSL_IS_FIRST_HANDSHAKE(s)) 
                st->read_state_first_init = 1; 
        } 
 
        st->state = MSG_FLOW_WRITING; 
        init_write_state_machine(s); 
    } 
 
    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 */ 
            check_fatal(s, SSL_F_STATE_MACHINE); 
            SSLerr(SSL_F_STATE_MACHINE, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED); 
            goto end; 
        } 
    } 
 
    ret = 1; 
 
 end: 
    st->in_handshake--; 
 
#ifndef OPENSSL_NO_SCTP 
    if (SSL_IS_DTLS(s) && BIO_dgram_is_sctp(SSL_get_wbio(s))) { 
        /* 
         * Notify SCTP BIO socket to leave handshake mode and allow stream 
         * identifier other than 0. 
         */ 
        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; 
    size_t 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); 
    size_t (*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)) 
                return SUB_STATE_ERROR; 
 
            if (s->s3->tmp.message_size > max_message_size(s)) { 
                SSLfatal(s, SSL_AD_ILLEGAL_PARAMETER, 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)) { 
                SSLfatal(s, SSL_AD_INTERNAL_ERROR, 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)) { 
                SSLfatal(s, SSL_AD_INTERNAL_ERROR, 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: 
                check_fatal(s, SSL_F_READ_STATE_MACHINE); 
                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: 
                check_fatal(s, SSL_F_READ_STATE_MACHINE); 
                /* Fall through */ 
            case WORK_MORE_A: 
            case WORK_MORE_B: 
            case WORK_MORE_C: 
                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 */ 
            SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_READ_STATE_MACHINE, 
                     ERR_R_INTERNAL_ERROR); 
            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 (*get_construct_message_f) (SSL *s, WPACKET *pkt, 
                                    int (**confunc) (SSL *s, WPACKET *pkt), 
                                    int *mt); 
    void (*cb) (const SSL *ssl, int type, int val) = NULL; 
    int (*confunc) (SSL *s, WPACKET *pkt); 
    int mt; 
    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; 
        get_construct_message_f = 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; 
        get_construct_message_f = 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: 
                check_fatal(s, SSL_F_WRITE_STATE_MACHINE); 
                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: 
                check_fatal(s, SSL_F_WRITE_STATE_MACHINE); 
                /* Fall through */ 
            case WORK_MORE_A: 
            case WORK_MORE_B: 
            case WORK_MORE_C: 
                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 (!get_construct_message_f(s, &pkt, &confunc, &mt)) { 
                /* SSLfatal() already called */ 
                return SUB_STATE_ERROR; 
            } 
            if (mt == SSL3_MT_DUMMY) { 
                /* Skip construction and sending. This isn't a "real" state */ 
                st->write_state = WRITE_STATE_POST_WORK; 
                st->write_state_work = WORK_MORE_A; 
                break; 
            } 
            if (!WPACKET_init(&pkt, s->init_buf) 
                    || !ssl_set_handshake_header(s, &pkt, mt)) { 
                WPACKET_cleanup(&pkt); 
                SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_WRITE_STATE_MACHINE, 
                         ERR_R_INTERNAL_ERROR); 
                return SUB_STATE_ERROR; 
            } 
            if (confunc != NULL && !confunc(s, &pkt)) { 
                WPACKET_cleanup(&pkt); 
                check_fatal(s, SSL_F_WRITE_STATE_MACHINE); 
                return SUB_STATE_ERROR; 
            } 
            if (!ssl_close_construct_packet(s, &pkt, mt) 
                    || !WPACKET_finish(&pkt)) { 
                WPACKET_cleanup(&pkt); 
                SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_WRITE_STATE_MACHINE, 
                         ERR_R_INTERNAL_ERROR); 
                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: 
                check_fatal(s, SSL_F_WRITE_STATE_MACHINE); 
                /* Fall through */ 
            case WORK_MORE_A: 
            case WORK_MORE_B: 
            case WORK_MORE_C: 
                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: 
            SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_WRITE_STATE_MACHINE, 
                     ERR_R_INTERNAL_ERROR); 
            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 received 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) 
        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; 
} 
 
/* 
 * This function returns 1 if TLS exporter is ready to export keying 
 * material, or 0 if otherwise. 
 */ 
int ossl_statem_export_allowed(SSL *s) 
{ 
    return s->s3->previous_server_finished_len != 0 
           && s->statem.hand_state != TLS_ST_SW_FINISHED; 
} 
 
/* 
 * Return 1 if early TLS exporter is ready to export keying material, 
 * or 0 if otherwise. 
 */ 
int ossl_statem_export_early_allowed(SSL *s) 
{ 
    /* 
     * The early exporter secret is only present on the server if we 
     * have accepted early_data. It is present on the client as long 
     * as we have sent early_data. 
     */ 
    return s->ext.early_data == SSL_EARLY_DATA_ACCEPTED 
           || (!s->server && s->ext.early_data != SSL_EARLY_DATA_NOT_SENT); 
}