path: root/ssl/statem/statem.c

/*
 * 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 <openssl/rand.h>
#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);
}

static void (*get_callback(SSL *s))(const SSL *, int, int)
{
    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)