Import OpenSSL 1.1.0f

ssl/statem/README

@@ -0,0 +1,63 @@
+State Machine Design
+====================
+
+This file provides some guidance on the thinking behind the design of the
+state machine code to aid future maintenance.
+
+The state machine code replaces an older state machine present in OpenSSL
+versions 1.0.2 and below. The new state machine has the following objectives:
+    - Remove duplication of state code between client and server
+    - Remove duplication of state code between TLS and DTLS
+    - Simplify transitions and bring the logic together in a single location
+      so that it is easier to validate
+    - Remove duplication of code between each of the message handling functions
+    - Receive a message first and then work out whether that is a valid
+      transition - not the other way around (the other way causes lots of issues
+      where we are expecting one type of message next but actually get something
+      else)
+    - Separate message flow state from handshake state (in order to better
+      understand each)
+      - message flow state = when to flush buffers; handling restarts in the
+        event of NBIO events; handling the common flow of steps for reading a
+        message and the common flow of steps for writing a message etc
+      - handshake state = what handshake message are we working on now
+    - Control complexity: only the state machine can change state: keep all
+      the state changes local to the state machine component
+
+The message flow state machine is divided into a reading sub-state machine and a
+writing sub-state machine. See the source comments in statem.c for a more
+detailed description of the various states and transitions possible.
+
+Conceptually the state machine component is designed as follows:
+
+                        libssl
+                           |
+---------------------------|-----statem.h--------------------------------------
+                           |
+                    _______V____________________
+                   |                            |
+                   |    statem.c                |
+                   |                            |
+                   |    Core state machine code |
+                   |____________________________|
+        statem_locl.h     ^          ^
+                 _________|          |_______
+                |                            |
+   _____________|____________   _____________|____________
+  |                          | |                          |
+  | statem_clnt.c            | | statem_srvr.c            |
+  |                          | |                          |
+  | TLS/DTLS client specific | | TLS/DTLS server specific |
+  | state machine code       | | state machine code       |
+  |__________________________| |__________________________|
+               |        |_______________|__       |
+               |        ________________|  |      |
+               |       |                   |      |
+   ____________V_______V________   ________V______V_______________
+  |                             | |                               |
+  | statem_both.c               | | statem_dtls.c                 |
+  |                             | |                               |
+  | Non core functions common   | | Non core functions common to  |
+  | to both servers and clients | | both DTLS servers and clients |
+  |_____________________________| |_______________________________|
+

ssl/statem/statem.c

@@ -0,0 +1,852 @@
+/*
+ * 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);
+}
+
+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++;
+            }
+
+            s->s3->tmp.cert_request = 0;
+        } 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_req = 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) {
+            default:
+                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);
+    void (*cb) (const SSL *ssl, int type, int val) = NULL;
+
+    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;
+
+            default:
+                return SUB_STATE_ERROR;
+            }
+            break;
+
+        case WRITE_STATE_PRE_WORK:
+            switch (st->write_state_work = pre_work(s, st->write_state_work)) {
+            default:
+                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 (construct_message(s) == 0)
+                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)) {
+            default:
+                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;
+}

ssl/statem/statem.h

@@ -0,0 +1,116 @@
+/*
+ * 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
+ */
+
+/*****************************************************************************
+ *                                                                           *
+ * These enums should be considered PRIVATE to the state machine. No         *
+ * non-state machine code should need to use these                           *
+ *                                                                           *
+ *****************************************************************************/
+/*
+ * Valid return codes used for functions performing work prior to or after
+ * sending or receiving a message
+ */
+typedef enum {
+    /* Something went wrong */
+    WORK_ERROR,
+    /* We're done working and there shouldn't be anything else to do after */
+    WORK_FINISHED_STOP,
+    /* We're done working move onto the next thing */
+    WORK_FINISHED_CONTINUE,
+    /* We're working on phase A */
+    WORK_MORE_A,
+    /* We're working on phase B */
+    WORK_MORE_B
+} WORK_STATE;
+
+/* Write transition return codes */
+typedef enum {
+    /* Something went wrong */
+    WRITE_TRAN_ERROR,
+    /* A transition was successfully completed and we should continue */
+    WRITE_TRAN_CONTINUE,
+    /* There is no more write work to be done */
+    WRITE_TRAN_FINISHED
+} WRITE_TRAN;
+
+/* Message flow states */
+typedef enum {
+    /* No handshake in progress */
+    MSG_FLOW_UNINITED,
+    /* A permanent error with this connection */
+    MSG_FLOW_ERROR,
+    /* We are about to renegotiate */
+    MSG_FLOW_RENEGOTIATE,
+    /* We are reading messages */
+    MSG_FLOW_READING,
+    /* We are writing messages */
+    MSG_FLOW_WRITING,
+    /* Handshake has finished */
+    MSG_FLOW_FINISHED
+} MSG_FLOW_STATE;
+
+/* Read states */
+typedef enum {
+    READ_STATE_HEADER,
+    READ_STATE_BODY,
+    READ_STATE_POST_PROCESS
+} READ_STATE;
+
+/* Write states */
+typedef enum {
+    WRITE_STATE_TRANSITION,
+    WRITE_STATE_PRE_WORK,
+    WRITE_STATE_SEND,
+    WRITE_STATE_POST_WORK
+} WRITE_STATE;
+
+/*****************************************************************************
+ *                                                                           *
+ * This structure should be considered "opaque" to anything outside of the   *
+ * state machine. No non-state machine code should be accessing the members  *
+ * of this structure.                                                        *
+ *                                                                           *
+ *****************************************************************************/
+
+struct ossl_statem_st {
+    MSG_FLOW_STATE state;
+    WRITE_STATE write_state;
+    WORK_STATE write_state_work;
+    READ_STATE read_state;
+    WORK_STATE read_state_work;
+    OSSL_HANDSHAKE_STATE hand_state;
+    int in_init;
+    int read_state_first_init;
+    /* true when we are actually in SSL_accept() or SSL_connect() */
+    int in_handshake;
+    /* Should we skip the CertificateVerify message? */
+    unsigned int no_cert_verify;
+    int use_timer;
+};
+typedef struct ossl_statem_st OSSL_STATEM;
+
+/*****************************************************************************
+ *                                                                           *
+ * The following macros/functions represent the libssl internal API to the   *
+ * state machine. Any libssl code may call these functions/macros            *
+ *                                                                           *
+ *****************************************************************************/
+
+__owur int ossl_statem_accept(SSL *s);
+__owur int ossl_statem_connect(SSL *s);
+void ossl_statem_clear(SSL *s);
+void ossl_statem_set_renegotiate(SSL *s);
+void ossl_statem_set_error(SSL *s);
+int ossl_statem_in_error(const SSL *s);
+void ossl_statem_set_in_init(SSL *s, int init);
+int ossl_statem_get_in_handshake(SSL *s);
+void ossl_statem_set_in_handshake(SSL *s, int inhand);
+void ossl_statem_set_hello_verify_done(SSL *s);
+__owur int ossl_statem_app_data_allowed(SSL *s);

ssl/statem/statem_locl.h

@@ -0,0 +1,124 @@
+/*
+ * 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
+ */
+
+/*****************************************************************************
+ *                                                                           *
+ * The following definitions are PRIVATE to the state machine. They should   *
+ * NOT be used outside of the state machine.                                 *
+ *                                                                           *
+ *****************************************************************************/
+
+/* Max message length definitions */
+
+/* The spec allows for a longer length than this, but we limit it */
+#define HELLO_VERIFY_REQUEST_MAX_LENGTH 258
+#define SERVER_HELLO_MAX_LENGTH         20000
+#define SERVER_KEY_EXCH_MAX_LENGTH      102400
+#define SERVER_HELLO_DONE_MAX_LENGTH    0
+#define CCS_MAX_LENGTH                  1
+/* Max should actually be 36 but we are generous */
+#define FINISHED_MAX_LENGTH             64
+
+/* Message processing return codes */
+typedef enum {
+    /* Something bad happened */
+    MSG_PROCESS_ERROR,
+    /* We've finished reading - swap to writing */
+    MSG_PROCESS_FINISHED_READING,
+    /*
+     * We've completed the main processing of this message but there is some
+     * post processing to be done.
+     */
+    MSG_PROCESS_CONTINUE_PROCESSING,
+    /* We've finished this message - read the next message */
+    MSG_PROCESS_CONTINUE_READING
+} MSG_PROCESS_RETURN;
+
+/* Flush the write BIO */
+int statem_flush(SSL *s);
+
+/*
+ * TLS/DTLS client state machine functions
+ */
+int ossl_statem_client_read_transition(SSL *s, int mt);
+WRITE_TRAN ossl_statem_client_write_transition(SSL *s);
+WORK_STATE ossl_statem_client_pre_work(SSL *s, WORK_STATE wst);
+WORK_STATE ossl_statem_client_post_work(SSL *s, WORK_STATE wst);
+int ossl_statem_client_construct_message(SSL *s);
+unsigned long ossl_statem_client_max_message_size(SSL *s);
+MSG_PROCESS_RETURN ossl_statem_client_process_message(SSL *s, PACKET *pkt);
+WORK_STATE ossl_statem_client_post_process_message(SSL *s, WORK_STATE wst);
+
+/*
+ * TLS/DTLS server state machine functions
+ */
+int ossl_statem_server_read_transition(SSL *s, int mt);
+WRITE_TRAN ossl_statem_server_write_transition(SSL *s);
+WORK_STATE ossl_statem_server_pre_work(SSL *s, WORK_STATE wst);
+WORK_STATE ossl_statem_server_post_work(SSL *s, WORK_STATE wst);
+int ossl_statem_server_construct_message(SSL *s);
+unsigned long ossl_statem_server_max_message_size(SSL *s);
+MSG_PROCESS_RETURN ossl_statem_server_process_message(SSL *s, PACKET *pkt);
+WORK_STATE ossl_statem_server_post_process_message(SSL *s, WORK_STATE wst);
+
+/* Functions for getting new message data */
+__owur int tls_get_message_header(SSL *s, int *mt);
+__owur int tls_get_message_body(SSL *s, unsigned long *len);
+__owur int dtls_get_message(SSL *s, int *mt, unsigned long *len);
+
+/* Message construction and processing functions */
+__owur MSG_PROCESS_RETURN tls_process_change_cipher_spec(SSL *s, PACKET *pkt);
+__owur MSG_PROCESS_RETURN tls_process_finished(SSL *s, PACKET *pkt);
+__owur int tls_construct_change_cipher_spec(SSL *s);
+__owur int dtls_construct_change_cipher_spec(SSL *s);
+
+__owur int tls_construct_finished(SSL *s, const char *sender, int slen);
+__owur WORK_STATE tls_finish_handshake(SSL *s, WORK_STATE wst);
+__owur WORK_STATE dtls_wait_for_dry(SSL *s);
+
+/* some client-only functions */
+__owur int tls_construct_client_hello(SSL *s);
+__owur MSG_PROCESS_RETURN tls_process_server_hello(SSL *s, PACKET *pkt);
+__owur MSG_PROCESS_RETURN tls_process_certificate_request(SSL *s, PACKET *pkt);
+__owur MSG_PROCESS_RETURN tls_process_new_session_ticket(SSL *s, PACKET *pkt);
+__owur MSG_PROCESS_RETURN tls_process_cert_status(SSL *s, PACKET *pkt);
+__owur MSG_PROCESS_RETURN tls_process_server_done(SSL *s, PACKET *pkt);
+__owur int tls_construct_client_verify(SSL *s);
+__owur WORK_STATE tls_prepare_client_certificate(SSL *s, WORK_STATE wst);
+__owur int tls_construct_client_certificate(SSL *s);
+__owur int ssl_do_client_cert_cb(SSL *s, X509 **px509, EVP_PKEY **ppkey);
+__owur int tls_construct_client_key_exchange(SSL *s);
+__owur int tls_client_key_exchange_post_work(SSL *s);
+__owur int tls_construct_cert_status(SSL *s);
+__owur MSG_PROCESS_RETURN tls_process_key_exchange(SSL *s, PACKET *pkt);
+__owur MSG_PROCESS_RETURN tls_process_server_certificate(SSL *s, PACKET *pkt);
+__owur int ssl3_check_cert_and_algorithm(SSL *s);
+#ifndef OPENSSL_NO_NEXTPROTONEG
+__owur int tls_construct_next_proto(SSL *s);
+#endif
+__owur MSG_PROCESS_RETURN dtls_process_hello_verify(SSL *s, PACKET *pkt);
+
+/* some server-only functions */
+__owur MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt);
+__owur WORK_STATE tls_post_process_client_hello(SSL *s, WORK_STATE wst);
+__owur int tls_construct_server_hello(SSL *s);
+__owur int tls_construct_hello_request(SSL *s);
+__owur int dtls_construct_hello_verify_request(SSL *s);
+__owur int tls_construct_server_certificate(SSL *s);
+__owur int tls_construct_server_key_exchange(SSL *s);
+__owur int tls_construct_certificate_request(SSL *s);
+__owur int tls_construct_server_done(SSL *s);
+__owur MSG_PROCESS_RETURN tls_process_client_certificate(SSL *s, PACKET *pkt);
+__owur MSG_PROCESS_RETURN tls_process_client_key_exchange(SSL *s, PACKET *pkt);
+__owur WORK_STATE tls_post_process_client_key_exchange(SSL *s, WORK_STATE wst);
+__owur MSG_PROCESS_RETURN tls_process_cert_verify(SSL *s, PACKET *pkt);
+#ifndef OPENSSL_NO_NEXTPROTONEG
+__owur MSG_PROCESS_RETURN tls_process_next_proto(SSL *s, PACKET *pkt);
+#endif
+__owur int tls_construct_new_session_ticket(SSL *s);