Handle compression methods correctly with SSLv2 compat ClientHello
[openssl.git] / ssl / statem / statem_srvr.c
index 03d75d0c88fc1fcb64ecd12aebc202b9b4dfe3a0..c7841ac48efdb841383386c9537d5827b6dfba23 100644 (file)
@@ -613,13 +613,15 @@ WORK_STATE ossl_statem_server_post_work(SSL *s, WORK_STATE wst)
 }
 
 /*
- * Construct a message to be sent from the server to the client.
+ * Get the message construction function and message type for sending from the
+ * server
  *
  * Valid return values are:
  *   1: Success
  *   0: Error
  */
-int ossl_statem_server_construct_message(SSL *s)
+int ossl_statem_server_construct_message(SSL *s, WPACKET *pkt,
+                                         confunc_f *confunc, int *mt)
 {
     OSSL_STATEM *st = &s->statem;
 
@@ -628,46 +630,67 @@ int ossl_statem_server_construct_message(SSL *s)
         /* Shouldn't happen */
         return 0;
 
+    case TLS_ST_SW_CHANGE:
+        if (SSL_IS_DTLS(s))
+            *confunc = dtls_construct_change_cipher_spec;
+        else
+            *confunc = tls_construct_change_cipher_spec;
+        *mt = SSL3_MT_CHANGE_CIPHER_SPEC;
+        break;
+
     case DTLS_ST_SW_HELLO_VERIFY_REQUEST:
-        return dtls_construct_hello_verify_request(s);
+        *confunc = dtls_construct_hello_verify_request;
+        *mt = DTLS1_MT_HELLO_VERIFY_REQUEST;
+        break;
 
     case TLS_ST_SW_HELLO_REQ:
-        return tls_construct_hello_request(s);
+        /* No construction function needed */
+        *confunc = NULL;
+        *mt = SSL3_MT_HELLO_REQUEST;
+        break;
 
     case TLS_ST_SW_SRVR_HELLO:
-        return tls_construct_server_hello(s);
+        *confunc = tls_construct_server_hello;
+        *mt = SSL3_MT_SERVER_HELLO;
+        break;
 
     case TLS_ST_SW_CERT:
-        return tls_construct_server_certificate(s);
+        *confunc = tls_construct_server_certificate;
+        *mt = SSL3_MT_CERTIFICATE;
+        break;
 
     case TLS_ST_SW_KEY_EXCH:
-        return tls_construct_server_key_exchange(s);
+        *confunc = tls_construct_server_key_exchange;
+        *mt = SSL3_MT_SERVER_KEY_EXCHANGE;
+        break;
 
     case TLS_ST_SW_CERT_REQ:
-        return tls_construct_certificate_request(s);
+        *confunc = tls_construct_certificate_request;
+        *mt = SSL3_MT_CERTIFICATE_REQUEST;
+        break;
 
     case TLS_ST_SW_SRVR_DONE:
-        return tls_construct_server_done(s);
+        *confunc = tls_construct_server_done;
+        *mt = SSL3_MT_SERVER_DONE;
+        break;
 
     case TLS_ST_SW_SESSION_TICKET:
-        return tls_construct_new_session_ticket(s);
+        *confunc = tls_construct_new_session_ticket;
+        *mt = SSL3_MT_NEWSESSION_TICKET;
+        break;
 
     case TLS_ST_SW_CERT_STATUS:
-        return tls_construct_cert_status(s);
-
-    case TLS_ST_SW_CHANGE:
-        if (SSL_IS_DTLS(s))
-            return dtls_construct_change_cipher_spec(s);
-        else
-            return tls_construct_change_cipher_spec(s);
+        *confunc = tls_construct_cert_status;
+        *mt = SSL3_MT_CERTIFICATE_STATUS;
+        break;
 
     case TLS_ST_SW_FINISHED:
-        return tls_construct_finished(s,
-                                      s->method->
-                                      ssl3_enc->server_finished_label,
-                                      s->method->
-                                      ssl3_enc->server_finished_label_len);
+        *confunc = tls_construct_finished;
+        *mt = SSL3_MT_FINISHED;
+        break;
     }
+
+    return 1;
 }
 
 /*
@@ -694,7 +717,7 @@ int ossl_statem_server_construct_message(SSL *s)
  * Returns the maximum allowed length for the current message that we are
  * reading. Excludes the message header.
  */
-unsigned long ossl_statem_server_max_message_size(SSL *s)
+size_t ossl_statem_server_max_message_size(SSL *s)
 {
     OSSL_STATEM *st = &s->statem;
 
@@ -829,19 +852,8 @@ static int ssl_check_srp_ext_ClientHello(SSL *s, int *al)
 }
 #endif
 
-int tls_construct_hello_request(SSL *s)
-{
-    if (!ssl_set_handshake_header(s, SSL3_MT_HELLO_REQUEST, 0)) {
-        SSLerr(SSL_F_TLS_CONSTRUCT_HELLO_REQUEST, ERR_R_INTERNAL_ERROR);
-        ossl_statem_set_error(s);
-        return 0;
-    }
-
-    return 1;
-}
-
 int dtls_raw_hello_verify_request(WPACKET *pkt, unsigned char *cookie,
-                                  unsigned char cookie_len)
+                                  size_t cookie_len)
 {
     /* Always use DTLS 1.0 version: see RFC 6347 */
     if (!WPACKET_put_bytes_u16(pkt, DTLS1_VERSION)
@@ -851,50 +863,33 @@ int dtls_raw_hello_verify_request(WPACKET *pkt, unsigned char *cookie,
     return 1;
 }
 
-int dtls_construct_hello_verify_request(SSL *s)
+int dtls_construct_hello_verify_request(SSL *s, WPACKET *pkt)
 {
-    size_t msglen;
-    WPACKET pkt;
-
+    unsigned int cookie_leni;
     if (s->ctx->app_gen_cookie_cb == NULL ||
         s->ctx->app_gen_cookie_cb(s, s->d1->cookie,
-                                  &(s->d1->cookie_len)) == 0 ||
-        s->d1->cookie_len > 255) {
+                                  &cookie_leni) == 0 ||
+        cookie_leni > 255) {
         SSLerr(SSL_F_DTLS_CONSTRUCT_HELLO_VERIFY_REQUEST,
                SSL_R_COOKIE_GEN_CALLBACK_FAILURE);
-        ossl_statem_set_error(s);
         return 0;
     }
+    s->d1->cookie_len = cookie_leni;
 
-    if (!WPACKET_init(&pkt, s->init_buf)
-            || !ssl_set_handshake_header2(s, &pkt,
-                                          DTLS1_MT_HELLO_VERIFY_REQUEST)
-            || !dtls_raw_hello_verify_request(&pkt, s->d1->cookie,
-                                              s->d1->cookie_len)
-               /*
-                * We don't call close_construct_packet() because we don't want
-                * to buffer this message
-                */
-            || !WPACKET_close(&pkt)
-            || !WPACKET_get_length(&pkt, &msglen)
-            || !WPACKET_finish(&pkt)) {
+    if (!dtls_raw_hello_verify_request(pkt, s->d1->cookie,
+                                              s->d1->cookie_len)) {
         SSLerr(SSL_F_DTLS_CONSTRUCT_HELLO_VERIFY_REQUEST, ERR_R_INTERNAL_ERROR);
-        WPACKET_cleanup(&pkt);
-        ossl_statem_set_error(s);
         return 0;
     }
 
-    /* number of bytes to write */
-    s->init_num = (int)msglen;
-    s->init_off = 0;
-
     return 1;
 }
 
 MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
 {
     int i, al = SSL_AD_INTERNAL_ERROR;
-    unsigned int j, complen = 0;
+    unsigned int j;
+    size_t loop;
     unsigned long id;
     const SSL_CIPHER *c;
 #ifndef OPENSSL_NO_COMP
@@ -903,16 +898,20 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
     STACK_OF(SSL_CIPHER) *ciphers = NULL;
     int protverr;
     /* |cookie| will only be initialized for DTLS. */
-    PACKET session_id, cipher_suites, compression, extensions, cookie;
-    int is_v2_record;
+    PACKET session_id, compression, extensions, cookie;
     static const unsigned char null_compression = 0;
+    CLIENTHELLO_MSG clienthello;
+
+    /*
+     * First step is to parse the raw ClientHello data into the CLIENTHELLO_MSG
+     * structure.
+     */
 
-    is_v2_record = RECORD_LAYER_is_sslv2_record(&s->rlayer);
+    clienthello.isv2 = RECORD_LAYER_is_sslv2_record(&s->rlayer);
 
     PACKET_null_init(&cookie);
-    /* First lets get s->client_version set correctly */
-    if (is_v2_record) {
-        unsigned int version;
+
+    if (clienthello.isv2) {
         unsigned int mt;
         /*-
          * An SSLv3/TLSv1 backwards-compatible CLIENT-HELLO in an SSLv2
@@ -939,73 +938,25 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
             SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, ERR_R_INTERNAL_ERROR);
             goto err;
         }
-
-        if (!PACKET_get_net_2(pkt, &version)) {
-            /* No protocol version supplied! */
-            SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_UNKNOWN_PROTOCOL);
-            goto err;
-        }
-        if (version == 0x0002) {
-            /* This is real SSLv2. We don't support it. */
-            SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_UNKNOWN_PROTOCOL);
-            goto err;
-        } else if ((version & 0xff00) == (SSL3_VERSION_MAJOR << 8)) {
-            /* SSLv3/TLS */
-            s->client_version = version;
-        } else {
-            /* No idea what protocol this is */
-            SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_UNKNOWN_PROTOCOL);
-            goto err;
-        }
-    } else {
-        /*
-         * use version from inside client hello, not from record header (may
-         * differ: see RFC 2246, Appendix E, second paragraph)
-         */
-        if (!PACKET_get_net_2(pkt, (unsigned int *)&s->client_version)) {
-            al = SSL_AD_DECODE_ERROR;
-            SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);
-            goto f_err;
-        }
-    }
-
-    /*
-     * Do SSL/TLS version negotiation if applicable. For DTLS we just check
-     * versions are potentially compatible. Version negotiation comes later.
-     */
-    if (!SSL_IS_DTLS(s)) {
-        protverr = ssl_choose_server_version(s);
-    } else if (s->method->version != DTLS_ANY_VERSION &&
-               DTLS_VERSION_LT(s->client_version, s->version)) {
-        protverr = SSL_R_VERSION_TOO_LOW;
-    } else {
-        protverr = 0;
     }
 
-    if (protverr) {
-        SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, protverr);
-        if ((!s->enc_write_ctx && !s->write_hash)) {
-            /*
-             * similar to ssl3_get_record, send alert using remote version
-             * number
-             */
-            s->version = s->client_version;
-        }
-        al = SSL_AD_PROTOCOL_VERSION;
-        goto f_err;
+    if (!PACKET_get_net_2(pkt, &clienthello.version)) {
+        al = SSL_AD_DECODE_ERROR;
+        SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);
+        goto err;
     }
 
     /* Parse the message and load client random. */
-    if (is_v2_record) {
+    if (clienthello.isv2) {
         /*
          * Handle an SSLv2 backwards compatible ClientHello
          * Note, this is only for SSLv3+ using the backward compatible format.
          * Real SSLv2 is not supported, and is rejected above.
          */
-        unsigned int cipher_len, session_id_len, challenge_len;
+        unsigned int ciphersuite_len, session_id_len, challenge_len;
         PACKET challenge;
 
-        if (!PACKET_get_net_2(pkt, &cipher_len)
+        if (!PACKET_get_net_2(pkt, &ciphersuite_len)
             || !PACKET_get_net_2(pkt, &session_id_len)
             || !PACKET_get_net_2(pkt, &challenge_len)) {
             SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO,
@@ -1013,6 +964,7 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
             al = SSL_AD_DECODE_ERROR;
             goto f_err;
         }
+        clienthello.session_id_len = session_id_len;
 
         if (session_id_len > SSL_MAX_SSL_SESSION_ID_LENGTH) {
             al = SSL_AD_DECODE_ERROR;
@@ -1020,8 +972,10 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
             goto f_err;
         }
 
-        if (!PACKET_get_sub_packet(pkt, &cipher_suites, cipher_len)
-            || !PACKET_get_sub_packet(pkt, &session_id, session_id_len)
+        if (!PACKET_get_sub_packet(pkt, &clienthello.ciphersuites,
+                                   ciphersuite_len)
+            || !PACKET_get_sub_packet(pkt, &session_id,
+                                      clienthello.session_id_len)
             || !PACKET_get_sub_packet(pkt, &challenge, challenge_len)
             /* No extensions. */
             || PACKET_remaining(pkt) != 0) {
@@ -1034,9 +988,9 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
         /* Load the client random and compression list. */
         challenge_len = challenge_len > SSL3_RANDOM_SIZE ? SSL3_RANDOM_SIZE :
             challenge_len;
-        memset(s->s3->client_random, 0, SSL3_RANDOM_SIZE);
+        memset(clienthello.random, 0, SSL3_RANDOM_SIZE);
         if (!PACKET_copy_bytes(&challenge,
-                               s->s3->client_random + SSL3_RANDOM_SIZE -
+                               clienthello.random + SSL3_RANDOM_SIZE -
                                challenge_len, challenge_len)
             /* Advertise only null compression. */
             || !PACKET_buf_init(&compression, &null_compression, 1)) {
@@ -1045,56 +999,135 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
             goto f_err;
         }
 
-        PACKET_null_init(&extensions);
+        PACKET_null_init(&clienthello.extensions);
     } else {
         /* Regular ClientHello. */
-        if (!PACKET_copy_bytes(pkt, s->s3->client_random, SSL3_RANDOM_SIZE)
+        if (!PACKET_copy_bytes(pkt, clienthello.random, SSL3_RANDOM_SIZE)
             || !PACKET_get_length_prefixed_1(pkt, &session_id)) {
             al = SSL_AD_DECODE_ERROR;
             SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
             goto f_err;
         }
 
-        if (PACKET_remaining(&session_id) > SSL_MAX_SSL_SESSION_ID_LENGTH) {
-            al = SSL_AD_DECODE_ERROR;
-            SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
-            goto f_err;
-        }
-
         if (SSL_IS_DTLS(s)) {
             if (!PACKET_get_length_prefixed_1(pkt, &cookie)) {
                 al = SSL_AD_DECODE_ERROR;
                 SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
                 goto f_err;
             }
+            if (!PACKET_copy_all(&cookie, clienthello.dtls_cookie,
+                                 DTLS1_COOKIE_LENGTH,
+                                 &clienthello.dtls_cookie_len)) {
+                al = SSL_AD_DECODE_ERROR;
+                SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
+                goto f_err;
+            }
             /*
              * If we require cookies and this ClientHello doesn't contain one,
              * just return since we do not want to allocate any memory yet.
              * So check cookie length...
              */
             if (SSL_get_options(s) & SSL_OP_COOKIE_EXCHANGE) {
-                if (PACKET_remaining(&cookie) == 0)
+                if (clienthello.dtls_cookie_len == 0)
                     return 1;
             }
         }
 
-        if (!PACKET_get_length_prefixed_2(pkt, &cipher_suites)
-            || !PACKET_get_length_prefixed_1(pkt, &compression)) {
+        if (!PACKET_get_length_prefixed_2(pkt, &clienthello.ciphersuites)) {
+            al = SSL_AD_DECODE_ERROR;
+            SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
+            goto f_err;
+        }
+
+        if (!PACKET_get_length_prefixed_1(pkt, &compression)) {
             al = SSL_AD_DECODE_ERROR;
             SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
             goto f_err;
         }
+
         /* Could be empty. */
-        extensions = *pkt;
+        if (PACKET_remaining(pkt) == 0) {
+            PACKET_null_init(&clienthello.extensions);
+        } else {
+            if (!PACKET_get_length_prefixed_2(pkt, &clienthello.extensions)) {
+                al = SSL_AD_DECODE_ERROR;
+                SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
+                goto f_err;
+            }
+        }
+    }
+
+    if (!PACKET_copy_all(&compression, clienthello.compressions,
+                         MAX_COMPRESSIONS_SIZE, &clienthello.compressions_len)
+            || !PACKET_copy_all(&session_id, clienthello.session_id,
+                                SSL_MAX_SSL_SESSION_ID_LENGTH,
+                                &clienthello.session_id_len)) {
+        al = SSL_AD_DECODE_ERROR;
+        SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
+        goto f_err;
+    }
+
+    /* We preserve the raw extensions PACKET for later use */
+    extensions = clienthello.extensions;
+    if (!tls_parse_raw_extensions(&extensions, &clienthello.pre_proc_exts,
+                                  &clienthello.num_extensions, &al)) {
+        /* SSLerr already been called */
+        goto f_err;
+    }
+
+    /* Finished parsing the ClientHello, now we can start processing it */
+
+    /* Set up the client_random */
+    memcpy(s->s3->client_random, clienthello.random, SSL3_RANDOM_SIZE);
+
+    /* Choose the version */
+
+    if (clienthello.isv2) {
+        if (clienthello.version == 0x0002) {
+            /* This is real SSLv2. We don't support it. */
+            SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_UNKNOWN_PROTOCOL);
+            goto err;
+        } else if ((clienthello.version & 0xff00) == (SSL3_VERSION_MAJOR << 8)) {
+            /* SSLv3/TLS */
+            s->client_version = clienthello.version;
+        } else {
+            /* No idea what protocol this is */
+            SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_UNKNOWN_PROTOCOL);
+            goto err;
+        }
+    }
+    /*
+     * Do SSL/TLS version negotiation if applicable. For DTLS we just check
+     * versions are potentially compatible. Version negotiation comes later.
+     */
+    if (!SSL_IS_DTLS(s)) {
+        protverr = ssl_choose_server_version(s, &clienthello);
+    } else if (s->method->version != DTLS_ANY_VERSION &&
+               DTLS_VERSION_LT((int)clienthello.version, s->version)) {
+        protverr = SSL_R_VERSION_TOO_LOW;
+    } else {
+        protverr = 0;
+    }
+
+    if (protverr) {
+        SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, protverr);
+        if ((!s->enc_write_ctx && !s->write_hash)) {
+            /*
+             * similar to ssl3_get_record, send alert using remote version
+             * number
+             */
+            s->version = s->client_version = clienthello.version;
+        }
+        al = SSL_AD_PROTOCOL_VERSION;
+        goto f_err;
     }
 
     if (SSL_IS_DTLS(s)) {
         /* Empty cookie was already handled above by returning early. */
         if (SSL_get_options(s) & SSL_OP_COOKIE_EXCHANGE) {
             if (s->ctx->app_verify_cookie_cb != NULL) {
-                if (s->ctx->app_verify_cookie_cb(s, PACKET_data(&cookie),
-                                                 PACKET_remaining(&cookie)) ==
-                    0) {
+                if (s->ctx->app_verify_cookie_cb(s, clienthello.dtls_cookie,
+                        clienthello.dtls_cookie_len) == 0) {
                     al = SSL_AD_HANDSHAKE_FAILURE;
                     SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO,
                            SSL_R_COOKIE_MISMATCH);
@@ -1102,7 +1135,9 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
                     /* else cookie verification succeeded */
                 }
                 /* default verification */
-            } else if (!PACKET_equal(&cookie, s->d1->cookie, s->d1->cookie_len)) {
+            } else if (s->d1->cookie_len != clienthello.dtls_cookie_len
+                    || memcmp(clienthello.dtls_cookie, s->d1->cookie,
+                              s->d1->cookie_len) != 0) {
                 al = SSL_AD_HANDSHAKE_FAILURE;
                 SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_COOKIE_MISMATCH);
                 goto f_err;
@@ -1110,7 +1145,7 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
             s->d1->cookie_verified = 1;
         }
         if (s->method->version == DTLS_ANY_VERSION) {
-            protverr = ssl_choose_server_version(s);
+            protverr = ssl_choose_server_version(s, &clienthello);
             if (protverr != 0) {
                 SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, protverr);
                 s->version = s->client_version;
@@ -1122,6 +1157,15 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
 
     s->hit = 0;
 
+    /* We need to do this before getting the session */
+    if (!tls_check_client_ems_support(s, &clienthello))
+    {
+        /* Only fails if the extension is malformed */
+        al = SSL_AD_DECODE_ERROR;
+        SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_CLIENTHELLO_TLSEXT);
+        goto f_err;
+    }
+
     /*
      * We don't allow resumption in a backwards compatible ClientHello.
      * TODO(openssl-team): in TLS1.1+, session_id MUST be empty.
@@ -1138,13 +1182,13 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
      * SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION setting will be
      * ignored.
      */
-    if (is_v2_record ||
+    if (clienthello.isv2 ||
         (s->new_session &&
          (s->options & SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION))) {
         if (!ssl_get_new_session(s, 1))
             goto err;
     } else {
-        i = ssl_get_prev_session(s, &extensions, &session_id);
+        i = ssl_get_prev_session(s, &clienthello);
         /*
          * Only resume if the session's version matches the negotiated
          * version.
@@ -1166,8 +1210,8 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
         }
     }
 
-    if (ssl_bytes_to_cipher_list(s, &cipher_suites, &(ciphers),
-                                 is_v2_record, &al) == NULL) {
+    if (ssl_bytes_to_cipher_list(s, &clienthello.ciphersuites, &(ciphers),
+                                 clienthello.isv2, &al) == NULL) {
         goto f_err;
     }
 
@@ -1202,13 +1246,12 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
         }
     }
 
-    complen = PACKET_remaining(&compression);
-    for (j = 0; j < complen; j++) {
-        if (PACKET_data(&compression)[j] == 0)
+    for (loop = 0; loop < clienthello.compressions_len; loop++) {
+        if (clienthello.compressions[loop] == 0)
             break;
     }
 
-    if (j >= complen) {
+    if (loop >= clienthello.compressions_len) {
         /* no compress */
         al = SSL_AD_DECODE_ERROR;
         SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_NO_COMPRESSION_SPECIFIED);
@@ -1216,11 +1259,9 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
     }
 
     /* TLS extensions */
-    if (s->version >= SSL3_VERSION) {
-        if (!ssl_parse_clienthello_tlsext(s, &extensions)) {
-            SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_PARSE_TLSEXT);
-            goto err;
-        }
+    if (!ssl_parse_clienthello_tlsext(s, &clienthello)) {
+        SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO, SSL_R_PARSE_TLSEXT);
+        goto err;
     }
 
     /*
@@ -1239,12 +1280,19 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
 
     if (!s->hit && s->version >= TLS1_VERSION && s->tls_session_secret_cb) {
         const SSL_CIPHER *pref_cipher = NULL;
+        /*
+         * s->session->master_key_length is a size_t, but this is an int for
+         * backwards compat reasons
+         */
+        int master_key_length;
 
-        s->session->master_key_length = sizeof(s->session->master_key);
+        master_key_length = sizeof(s->session->master_key);
         if (s->tls_session_secret_cb(s, s->session->master_key,
-                                     &s->session->master_key_length, ciphers,
+                                     &master_key_length, ciphers,
                                      &pref_cipher,
-                                     s->tls_session_secret_cb_arg)) {
+                                     s->tls_session_secret_cb_arg)
+                && master_key_length > 0) {
+            s->session->master_key_length = master_key_length;
             s->hit = 1;
             s->session->ciphers = ciphers;
             s->session->verify_result = X509_V_OK;
@@ -1304,11 +1352,11 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
             goto f_err;
         }
         /* Look for resumed method in compression list */
-        for (k = 0; k < complen; k++) {
-            if (PACKET_data(&compression)[k] == comp_id)
+        for (k = 0; k < clienthello.compressions_len; k++) {
+            if (clienthello.compressions[k] == comp_id)
                 break;
         }
-        if (k >= complen) {
+        if (k >= clienthello.compressions_len) {
             al = SSL_AD_ILLEGAL_PARAMETER;
             SSLerr(SSL_F_TLS_PROCESS_CLIENT_HELLO,
                    SSL_R_REQUIRED_COMPRESSION_ALGORITHM_MISSING);
@@ -1325,8 +1373,8 @@ MSG_PROCESS_RETURN tls_process_client_hello(SSL *s, PACKET *pkt)
         for (m = 0; m < nn; m++) {
             comp = sk_SSL_COMP_value(s->ctx->comp_methods, m);
             v = comp->id;
-            for (o = 0; o < complen; o++) {
-                if (v == PACKET_data(&compression)[o]) {
+            for (o = 0; o < clienthello.compressions_len; o++) {
+                if (v == clienthello.compressions[o]) {
                     done = 1;
                     break;
                 }
@@ -1490,28 +1538,20 @@ WORK_STATE tls_post_process_client_hello(SSL *s, WORK_STATE wst)
     return WORK_ERROR;
 }
 
-int tls_construct_server_hello(SSL *s)
+int tls_construct_server_hello(SSL *s, WPACKET *pkt)
 {
-    unsigned char *buf;
-    unsigned char *p, *d;
-    int i, sl;
-    int al = 0;
-    unsigned long l;
-
-    buf = (unsigned char *)s->init_buf->data;
+    int compm, al = SSL_AD_INTERNAL_ERROR;
+    size_t sl, len;
 
-    /* Do the message type and length last */
-    d = p = ssl_handshake_start(s);
-
-    *(p++) = s->version >> 8;
-    *(p++) = s->version & 0xff;
-
-    /*
-     * Random stuff. Filling of the server_random takes place in
-     * tls_process_client_hello()
-     */
-    memcpy(p, s->s3->server_random, SSL3_RANDOM_SIZE);
-    p += SSL3_RANDOM_SIZE;
+    if (!WPACKET_put_bytes_u16(pkt, s->version)
+               /*
+                * Random stuff. Filling of the server_random takes place in
+                * tls_process_client_hello()
+                */
+            || !WPACKET_memcpy(pkt, s->s3->server_random, SSL3_RANDOM_SIZE)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_HELLO, ERR_R_INTERNAL_ERROR);
+        goto err;
+    }
 
     /*-
      * There are several cases for the session ID to send
@@ -1535,114 +1575,79 @@ int tls_construct_server_hello(SSL *s)
         s->session->session_id_length = 0;
 
     sl = s->session->session_id_length;
-    if (sl > (int)sizeof(s->session->session_id)) {
+    if (sl > sizeof(s->session->session_id)) {
         SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_HELLO, ERR_R_INTERNAL_ERROR);
-        ossl_statem_set_error(s);
-        return 0;
+        goto err;
     }
-    *(p++) = sl;
-    memcpy(p, s->session->session_id, sl);
-    p += sl;
-
-    /* put the cipher */
-    i = ssl3_put_cipher_by_char_old(s->s3->tmp.new_cipher, p);
-    p += i;
 
-    /* put the compression method */
+    /* set up the compression method */
 #ifdef OPENSSL_NO_COMP
-    *(p++) = 0;
+    compm = 0;
 #else
     if (s->s3->tmp.new_compression == NULL)
-        *(p++) = 0;
+        compm = 0;
     else
-        *(p++) = s->s3->tmp.new_compression->id;
+        compm = s->s3->tmp.new_compression->id;
 #endif
 
-    if (ssl_prepare_serverhello_tlsext(s) <= 0) {
-        SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_HELLO, SSL_R_SERVERHELLO_TLSEXT);
-        ossl_statem_set_error(s);
-        return 0;
-    }
-    if ((p =
-         ssl_add_serverhello_tlsext(s, p, buf + SSL3_RT_MAX_PLAIN_LENGTH,
-                                    &al)) == NULL) {
-        ssl3_send_alert(s, SSL3_AL_FATAL, al);
-        SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_HELLO, ERR_R_INTERNAL_ERROR);
-        ossl_statem_set_error(s);
-        return 0;
-    }
-
-    /* do the header */
-    l = (p - d);
-    if (!ssl_set_handshake_header(s, SSL3_MT_SERVER_HELLO, l)) {
+    if (!WPACKET_sub_memcpy_u8(pkt, s->session->session_id, sl)
+            || !s->method->put_cipher_by_char(s->s3->tmp.new_cipher, pkt, &len)
+            || !WPACKET_put_bytes_u8(pkt, compm)
+            || !ssl_prepare_serverhello_tlsext(s)
+            || !ssl_add_serverhello_tlsext(s, pkt, &al)) {
         SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_HELLO, ERR_R_INTERNAL_ERROR);
-        ossl_statem_set_error(s);
-        return 0;
+        goto err;
     }
 
     return 1;
+ err:
+    ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
+    return 0;
 }
 
-int tls_construct_server_done(SSL *s)
+int tls_construct_server_done(SSL *s, WPACKET *pkt)
 {
-    if (!ssl_set_handshake_header(s, SSL3_MT_SERVER_DONE, 0)) {
-        SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_DONE, ERR_R_INTERNAL_ERROR);
-        ossl_statem_set_error(s);
-        return 0;
-    }
-
     if (!s->s3->tmp.cert_request) {
         if (!ssl3_digest_cached_records(s, 0)) {
-            ossl_statem_set_error(s);
+            ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
+            return 0;
         }
     }
-
     return 1;
 }
 
-int tls_construct_server_key_exchange(SSL *s)
+int tls_construct_server_key_exchange(SSL *s, WPACKET *pkt)
 {
 #ifndef OPENSSL_NO_DH
     EVP_PKEY *pkdh = NULL;
-    int j;
 #endif
 #ifndef OPENSSL_NO_EC
     unsigned char *encodedPoint = NULL;
-    int encodedlen = 0;
+    size_t encodedlen = 0;
     int curve_id = 0;
 #endif
     EVP_PKEY *pkey;
     const EVP_MD *md = NULL;
-    unsigned char *p, *d;
-    int al, i;
+    int al = SSL_AD_INTERNAL_ERROR, i;
     unsigned long type;
-    int n;
     const BIGNUM *r[4];
-    int nr[4], kn;
-    BUF_MEM *buf;
     EVP_MD_CTX *md_ctx = EVP_MD_CTX_new();
+    size_t paramlen, paramoffset;
+
+    if (!WPACKET_get_total_written(pkt, &paramoffset)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE, ERR_R_INTERNAL_ERROR);
+        goto f_err;
+    }
 
     if (md_ctx == NULL) {
         SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE, ERR_R_MALLOC_FAILURE);
-        al = SSL_AD_INTERNAL_ERROR;
         goto f_err;
     }
 
     type = s->s3->tmp.new_cipher->algorithm_mkey;
 
-    buf = s->init_buf;
-
     r[0] = r[1] = r[2] = r[3] = NULL;
-    n = 0;
 #ifndef OPENSSL_NO_PSK
-    if (type & SSL_PSK) {
-        /*
-         * reserve size for record length and PSK identity hint
-         */
-        n += 2;
-        if (s->cert->psk_identity_hint)
-            n += strlen(s->cert->psk_identity_hint);
-    }
     /* Plain PSK or RSAPSK nothing to do */
     if (type & (SSL_kPSK | SSL_kRSAPSK)) {
     } else
@@ -1659,7 +1664,6 @@ int tls_construct_server_key_exchange(SSL *s)
             pkdh = EVP_PKEY_new();
             if (pkdh == NULL || dhp == NULL) {
                 DH_free(dhp);
-                al = SSL_AD_INTERNAL_ERROR;
                 SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
                        ERR_R_INTERNAL_ERROR);
                 goto f_err;
@@ -1673,7 +1677,6 @@ int tls_construct_server_key_exchange(SSL *s)
             DH *dhp = s->cert->dh_tmp_cb(s, 0, 1024);
             pkdh = ssl_dh_to_pkey(dhp);
             if (pkdh == NULL) {
-                al = SSL_AD_INTERNAL_ERROR;
                 SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
                        ERR_R_INTERNAL_ERROR);
                 goto f_err;
@@ -1736,7 +1739,6 @@ int tls_construct_server_key_exchange(SSL *s)
         s->s3->tmp.pkey = ssl_generate_pkey_curve(curve_id);
         /* Generate a new key for this curve */
         if (s->s3->tmp.pkey == NULL) {
-            al = SSL_AD_INTERNAL_ERROR;
             SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE, ERR_R_EVP_LIB);
             goto f_err;
         }
@@ -1749,13 +1751,6 @@ int tls_construct_server_key_exchange(SSL *s)
             goto err;
         }
 
-        /*
-         * We only support named (not generic) curves in ECDH ephemeral key
-         * exchanges. In this situation, we need four additional bytes to
-         * encode the entire ServerECDHParams structure.
-         */
-        n += 4 + encodedlen;
-
         /*
          * We'll generate the serverKeyExchange message explicitly so we
          * can set these to NULLs
@@ -1787,25 +1782,6 @@ int tls_construct_server_key_exchange(SSL *s)
                SSL_R_UNKNOWN_KEY_EXCHANGE_TYPE);
         goto f_err;
     }
-    for (i = 0; i < 4 && r[i] != NULL; i++) {
-        nr[i] = BN_num_bytes(r[i]);
-#ifndef OPENSSL_NO_SRP
-        if ((i == 2) && (type & SSL_kSRP))
-            n += 1 + nr[i];
-        else
-#endif
-#ifndef OPENSSL_NO_DH
-        /*-
-         * for interoperability with some versions of the Microsoft TLS
-         * stack, we need to zero pad the DHE pub key to the same length
-         * as the prime, so use the length of the prime here
-         */
-        if ((i == 2) && (type & (SSL_kDHE | SSL_kDHEPSK)))
-            n += 2 + nr[0];
-        else
-#endif
-            n += 2 + nr[i];
-    }
 
     if (!(s->s3->tmp.new_cipher->algorithm_auth & (SSL_aNULL | SSL_aSRP))
         && !(s->s3->tmp.new_cipher->algorithm_mkey & SSL_PSK)) {
@@ -1814,53 +1790,46 @@ int tls_construct_server_key_exchange(SSL *s)
             al = SSL_AD_DECODE_ERROR;
             goto f_err;
         }
-        kn = EVP_PKEY_size(pkey);
-        /* Allow space for signature algorithm */
-        if (SSL_USE_SIGALGS(s))
-            kn += 2;
-        /* Allow space for signature length */
-        kn += 2;
     } else {
         pkey = NULL;
-        kn = 0;
-    }
-
-    if (!BUF_MEM_grow_clean(buf, n + SSL_HM_HEADER_LENGTH(s) + kn)) {
-        SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE, ERR_LIB_BUF);
-        goto err;
     }
-    d = p = ssl_handshake_start(s);
 
 #ifndef OPENSSL_NO_PSK
     if (type & SSL_PSK) {
-        /* copy PSK identity hint */
-        if (s->cert->psk_identity_hint) {
-            size_t len = strlen(s->cert->psk_identity_hint);
-            if (len > PSK_MAX_IDENTITY_LEN) {
-                /*
-                 * Should not happen - we already checked this when we set
-                 * the identity hint
-                 */
-                SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
-                       ERR_R_INTERNAL_ERROR);
-                goto err;
-            }
-            s2n(len, p);
-            memcpy(p, s->cert->psk_identity_hint, len);
-            p += len;
-        } else {
-            s2n(0, p);
+        size_t len = (s->cert->psk_identity_hint == NULL)
+                        ? 0 : strlen(s->cert->psk_identity_hint);
+
+        /*
+         * It should not happen that len > PSK_MAX_IDENTITY_LEN - we already
+         * checked this when we set the identity hint - but just in case
+         */
+        if (len > PSK_MAX_IDENTITY_LEN
+                || !WPACKET_sub_memcpy_u16(pkt, s->cert->psk_identity_hint,
+                                           len)) {
+            SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
+                   ERR_R_INTERNAL_ERROR);
+            goto f_err;
         }
     }
 #endif
 
     for (i = 0; i < 4 && r[i] != NULL; i++) {
+        unsigned char *binval;
+        int res;
+
 #ifndef OPENSSL_NO_SRP
         if ((i == 2) && (type & SSL_kSRP)) {
-            *p = nr[i];
-            p++;
+            res = WPACKET_start_sub_packet_u8(pkt);
         } else
 #endif
+            res = WPACKET_start_sub_packet_u16(pkt);
+
+        if (!res) {
+            SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
+                   ERR_R_INTERNAL_ERROR);
+            goto f_err;
+        }
+
 #ifndef OPENSSL_NO_DH
         /*-
          * for interoperability with some versions of the Microsoft TLS
@@ -1868,38 +1837,46 @@ int tls_construct_server_key_exchange(SSL *s)
          * as the prime
          */
         if ((i == 2) && (type & (SSL_kDHE | SSL_kDHEPSK))) {
-            s2n(nr[0], p);
-            for (j = 0; j < (nr[0] - nr[2]); ++j) {
-                *p = 0;
-                ++p;
+            size_t len = BN_num_bytes(r[0]) - BN_num_bytes(r[2]);
+
+            if (len > 0) {
+                if (!WPACKET_allocate_bytes(pkt, len, &binval)) {
+                    SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
+                           ERR_R_INTERNAL_ERROR);
+                    goto f_err;
+                }
+                memset(binval, 0, len);
             }
-        } else
+        }
 #endif
-            s2n(nr[i], p);
-        BN_bn2bin(r[i], p);
-        p += nr[i];
+        if (!WPACKET_allocate_bytes(pkt, BN_num_bytes(r[i]), &binval)
+                || !WPACKET_close(pkt)) {
+            SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
+                   ERR_R_INTERNAL_ERROR);
+            goto f_err;
+        }
+
+        BN_bn2bin(r[i], binval);
     }
 
 #ifndef OPENSSL_NO_EC
     if (type & (SSL_kECDHE | SSL_kECDHEPSK)) {
         /*
-         * XXX: For now, we only support named (not generic) curves. In
-         * this situation, the serverKeyExchange message has: [1 byte
-         * CurveType], [2 byte CurveName] [1 byte length of encoded
-         * point], followed by the actual encoded point itself
+         * We only support named (not generic) curves. In this situation, the
+         * ServerKeyExchange message has: [1 byte CurveType], [2 byte CurveName]
+         * [1 byte length of encoded point], followed by the actual encoded
+         * point itself
          */
-        *p = NAMED_CURVE_TYPE;
-        p += 1;
-        *p = 0;
-        p += 1;
-        *p = curve_id;
-        p += 1;
-        *p = encodedlen;
-        p += 1;
-        memcpy(p, encodedPoint, encodedlen);
+        if (!WPACKET_put_bytes_u8(pkt, NAMED_CURVE_TYPE)
+                || !WPACKET_put_bytes_u8(pkt, 0)
+                || !WPACKET_put_bytes_u8(pkt, curve_id)
+                || !WPACKET_sub_memcpy_u8(pkt, encodedPoint, encodedlen)) {
+            SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
+                   ERR_R_INTERNAL_ERROR);
+            goto f_err;
+        }
         OPENSSL_free(encodedPoint);
         encodedPoint = NULL;
-        p += encodedlen;
     }
 #endif
 
@@ -1910,36 +1887,49 @@ int tls_construct_server_key_exchange(SSL *s)
          * points to the space at the end.
          */
         if (md) {
+            unsigned char *sigbytes1, *sigbytes2;
+            unsigned int siglen;
+
+            /* Get length of the parameters we have written above */
+            if (!WPACKET_get_length(pkt, &paramlen)) {
+                SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
+                       ERR_R_INTERNAL_ERROR);
+                goto f_err;
+            }
             /* send signature algorithm */
             if (SSL_USE_SIGALGS(s)) {
-                if (!tls12_get_sigandhash_old(p, pkey, md)) {
+                if (!tls12_get_sigandhash(pkt, pkey, md)) {
                     /* Should never happen */
-                    al = SSL_AD_INTERNAL_ERROR;
                     SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
                            ERR_R_INTERNAL_ERROR);
                     goto f_err;
                 }
-                p += 2;
             }
 #ifdef SSL_DEBUG
             fprintf(stderr, "Using hash %s\n", EVP_MD_name(md));
 #endif
-            if (EVP_SignInit_ex(md_ctx, md, NULL) <= 0
-                || EVP_SignUpdate(md_ctx, &(s->s3->client_random[0]),
-                                  SSL3_RANDOM_SIZE) <= 0
-                || EVP_SignUpdate(md_ctx, &(s->s3->server_random[0]),
-                                  SSL3_RANDOM_SIZE) <= 0
-                || EVP_SignUpdate(md_ctx, d, n) <= 0
-                || EVP_SignFinal(md_ctx, &(p[2]),
-                                 (unsigned int *)&i, pkey) <= 0) {
-                SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE, ERR_LIB_EVP);
-                al = SSL_AD_INTERNAL_ERROR;
+            /*
+             * Create the signature. We don't know the actual length of the sig
+             * until after we've created it, so we reserve enough bytes for it
+             * up front, and then properly allocate them in the WPACKET
+             * afterwards.
+             */
+            if (!WPACKET_sub_reserve_bytes_u16(pkt, EVP_PKEY_size(pkey),
+                                               &sigbytes1)
+                    || EVP_SignInit_ex(md_ctx, md, NULL) <= 0
+                    || EVP_SignUpdate(md_ctx, &(s->s3->client_random[0]),
+                                      SSL3_RANDOM_SIZE) <= 0
+                    || EVP_SignUpdate(md_ctx, &(s->s3->server_random[0]),
+                                      SSL3_RANDOM_SIZE) <= 0
+                    || EVP_SignUpdate(md_ctx, s->init_buf->data + paramoffset,
+                                      paramlen) <= 0
+                    || EVP_SignFinal(md_ctx, sigbytes1, &siglen, pkey) <= 0
+                    || !WPACKET_sub_allocate_bytes_u16(pkt, siglen, &sigbytes2)
+                    || sigbytes1 != sigbytes2) {
+                SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE,
+                       ERR_R_INTERNAL_ERROR);
                 goto f_err;
             }
-            s2n(i, p);
-            n += i + 2;
-            if (SSL_USE_SIGALGS(s))
-                n += 2;
         } else {
             /* Is this error check actually needed? */
             al = SSL_AD_HANDSHAKE_FAILURE;
@@ -1949,12 +1939,6 @@ int tls_construct_server_key_exchange(SSL *s)
         }
     }
 
-    if (!ssl_set_handshake_header(s, SSL3_MT_SERVER_KEY_EXCHANGE, n)) {
-        al = SSL_AD_HANDSHAKE_FAILURE;
-        SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_KEY_EXCHANGE, ERR_R_INTERNAL_ERROR);
-        goto f_err;
-    }
-
     EVP_MD_CTX_free(md_ctx);
     return 1;
  f_err:
@@ -1967,68 +1951,61 @@ int tls_construct_server_key_exchange(SSL *s)
     OPENSSL_free(encodedPoint);
 #endif
     EVP_MD_CTX_free(md_ctx);
-    ossl_statem_set_error(s);
     return 0;
 }
 
-int tls_construct_certificate_request(SSL *s)
+int tls_construct_certificate_request(SSL *s, WPACKET *pkt)
 {
-    unsigned char *p, *d;
-    int i, j, nl, off, n;
+    int i;
     STACK_OF(X509_NAME) *sk = NULL;
-    X509_NAME *name;
-    BUF_MEM *buf;
-
-    buf = s->init_buf;
-
-    d = p = ssl_handshake_start(s);
 
     /* get the list of acceptable cert types */
-    p++;
-    n = ssl3_get_req_cert_type(s, p);
-    d[0] = n;
-    p += n;
-    n++;
+    if (!WPACKET_start_sub_packet_u8(pkt)
+            || !ssl3_get_req_cert_type(s, pkt)
+            || !WPACKET_close(pkt)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_CERTIFICATE_REQUEST, ERR_R_INTERNAL_ERROR);
+        goto err;
+    }
 
     if (SSL_USE_SIGALGS(s)) {
         const unsigned char *psigs;
-        unsigned char *etmp = p;
-        nl = tls12_get_psigalgs(s, &psigs);
-        /* Skip over length for now */
-        p += 2;
-        nl = tls12_copy_sigalgs_old(s, p, psigs, nl);
-        /* Now fill in length */
-        s2n(nl, etmp);
-        p += nl;
-        n += nl + 2;
+        size_t nl = tls12_get_psigalgs(s, &psigs);
+        if (!WPACKET_start_sub_packet_u16(pkt)
+                || !tls12_copy_sigalgs(s, pkt, psigs, nl)
+                || !WPACKET_close(pkt)) {
+            SSLerr(SSL_F_TLS_CONSTRUCT_CERTIFICATE_REQUEST,
+                   ERR_R_INTERNAL_ERROR);
+            goto err;
+        }
     }
 
-    off = n;
-    p += 2;
-    n += 2;
+    /* Start sub-packet for client CA list */
+    if (!WPACKET_start_sub_packet_u16(pkt)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_CERTIFICATE_REQUEST, ERR_R_INTERNAL_ERROR);
+        goto err;
+    }
 
     sk = SSL_get_client_CA_list(s);
-    nl = 0;
     if (sk != NULL) {
         for (i = 0; i < sk_X509_NAME_num(sk); i++) {
-            name = sk_X509_NAME_value(sk, i);
-            j = i2d_X509_NAME(name, NULL);
-            if (!BUF_MEM_grow_clean(buf, SSL_HM_HEADER_LENGTH(s) + n + j + 2)) {
-                SSLerr(SSL_F_TLS_CONSTRUCT_CERTIFICATE_REQUEST, ERR_R_BUF_LIB);
+            unsigned char *namebytes;
+            X509_NAME *name = sk_X509_NAME_value(sk, i);
+            int namelen;
+
+            if (name == NULL
+                    || (namelen = i2d_X509_NAME(name, NULL)) < 0
+                    || !WPACKET_sub_allocate_bytes_u16(pkt, namelen,
+                                                       &namebytes)
+                    || i2d_X509_NAME(name, &namebytes) != namelen) {
+                SSLerr(SSL_F_TLS_CONSTRUCT_CERTIFICATE_REQUEST,
+                       ERR_R_INTERNAL_ERROR);
                 goto err;
             }
-            p = ssl_handshake_start(s) + n;
-            s2n(j, p);
-            i2d_X509_NAME(name, &p);
-            n += 2 + j;
-            nl += 2 + j;
         }
     }
     /* else no CA names */
-    p = ssl_handshake_start(s) + off;
-    s2n(nl, p);
 
-    if (!ssl_set_handshake_header(s, SSL3_MT_CERTIFICATE_REQUEST, n)) {
+    if (!WPACKET_close(pkt)) {
         SSLerr(SSL_F_TLS_CONSTRUCT_CERTIFICATE_REQUEST, ERR_R_INTERNAL_ERROR);
         goto err;
     }
@@ -2037,7 +2014,7 @@ int tls_construct_certificate_request(SSL *s)
 
     return 1;
  err:
-    ossl_statem_set_error(s);
+    ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
     return 0;
 }
 
@@ -2173,9 +2150,10 @@ static int tls_process_cke_rsa(SSL *s, PACKET *pkt, int *al)
      * Decrypt with no padding. PKCS#1 padding will be removed as part of
      * the timing-sensitive code below.
      */
-    decrypt_len = RSA_private_decrypt(PACKET_remaining(&enc_premaster),
-                                      PACKET_data(&enc_premaster),
-                                      rsa_decrypt, rsa, RSA_NO_PADDING);
+     /* TODO(size_t): Convert this function */
+    decrypt_len = (int)RSA_private_decrypt((int)PACKET_remaining(&enc_premaster),
+                                           PACKET_data(&enc_premaster),
+                                           rsa_decrypt, rsa, RSA_NO_PADDING);
     if (decrypt_len < 0)
         goto err;
 
@@ -2456,7 +2434,7 @@ static int tls_process_cke_gost(SSL *s, PACKET *pkt, int *al)
     unsigned long alg_a;
     int Ttag, Tclass;
     long Tlen;
-    long sess_key_len;
+    size_t sess_key_len;
     const unsigned char *data;
     int ret = 0;
 
@@ -2506,8 +2484,9 @@ static int tls_process_cke_gost(SSL *s, PACKET *pkt, int *al)
         SSLerr(SSL_F_TLS_PROCESS_CKE_GOST, ERR_R_INTERNAL_ERROR);
         goto err;
     }
+    /* TODO(size_t): Convert this function */
     if (ASN1_get_object((const unsigned char **)&data, &Tlen, &Ttag,
-                        &Tclass, sess_key_len) != V_ASN1_CONSTRUCTED
+                        &Tclass, (long)sess_key_len) != V_ASN1_CONSTRUCTED
         || Ttag != V_ASN1_SEQUENCE || Tclass != V_ASN1_UNIVERSAL) {
         *al = SSL_AD_DECODE_ERROR;
         SSLerr(SSL_F_TLS_PROCESS_CKE_GOST, SSL_R_DECRYPTION_FAILED);
@@ -2809,7 +2788,7 @@ MSG_PROCESS_RETURN tls_process_cert_verify(SSL *s, PACKET *pkt)
 
     if (s->version == SSL3_VERSION
         && !EVP_MD_CTX_ctrl(mctx, EVP_CTRL_SSL3_MASTER_SECRET,
-                            s->session->master_key_length,
+                            (int)s->session->master_key_length,
                             s->session->master_key)) {
         SSLerr(SSL_F_TLS_PROCESS_CERT_VERIFY, ERR_R_EVP_LIB);
         al = SSL_AD_INTERNAL_ERROR;
@@ -2953,40 +2932,39 @@ MSG_PROCESS_RETURN tls_process_client_certificate(SSL *s, PACKET *pkt)
     return ret;
 }
 
-int tls_construct_server_certificate(SSL *s)
+int tls_construct_server_certificate(SSL *s, WPACKET *pkt)
 {
     CERT_PKEY *cpk;
 
     cpk = ssl_get_server_send_pkey(s);
     if (cpk == NULL) {
         SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_CERTIFICATE, ERR_R_INTERNAL_ERROR);
-        ossl_statem_set_error(s);
         return 0;
     }
 
-    if (!ssl3_output_cert_chain(s, cpk)) {
+    if (!ssl3_output_cert_chain(s, pkt, cpk)) {
         SSLerr(SSL_F_TLS_CONSTRUCT_SERVER_CERTIFICATE, ERR_R_INTERNAL_ERROR);
-        ossl_statem_set_error(s);
         return 0;
     }
 
     return 1;
 }
 
-int tls_construct_new_session_ticket(SSL *s)
+int tls_construct_new_session_ticket(SSL *s, WPACKET *pkt)
 {
     unsigned char *senc = NULL;
-    EVP_CIPHER_CTX *ctx;
+    EVP_CIPHER_CTX *ctx = NULL;
     HMAC_CTX *hctx = NULL;
-    unsigned char *p, *macstart;
+    unsigned char *p, *encdata1, *encdata2, *macdata1, *macdata2;
     const unsigned char *const_p;
-    int len, slen_full, slen;
+    int len, slen_full, slen, lenfinal;
     SSL_SESSION *sess;
     unsigned int hlen;
     SSL_CTX *tctx = s->initial_ctx;
     unsigned char iv[EVP_MAX_IV_LENGTH];
     unsigned char key_name[TLSEXT_KEYNAME_LENGTH];
     int iv_len;
+    size_t macoffset, macendoffset;
 
     /* get session encoding length */
     slen_full = i2d_SSL_SESSION(s->session, NULL);
@@ -3006,6 +2984,10 @@ int tls_construct_new_session_ticket(SSL *s)
 
     ctx = EVP_CIPHER_CTX_new();
     hctx = HMAC_CTX_new();
+    if (ctx == NULL || hctx == NULL) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_NEW_SESSION_TICKET, ERR_R_MALLOC_FAILURE);
+        goto err;
+    }
 
     p = senc;
     if (!i2d_SSL_SESSION(s->session, &p))
@@ -3032,21 +3014,6 @@ int tls_construct_new_session_ticket(SSL *s)
     }
     SSL_SESSION_free(sess);
 
-    /*-
-     * Grow buffer if need be: the length calculation is as
-     * follows handshake_header_length +
-     * 4 (ticket lifetime hint) + 2 (ticket length) +
-     * sizeof(keyname) + max_iv_len (iv length) +
-     * max_enc_block_size (max encrypted session * length) +
-     * max_md_size (HMAC) + session_length.
-     */
-    if (!BUF_MEM_grow(s->init_buf,
-                      SSL_HM_HEADER_LENGTH(s) + 6 + sizeof(key_name) +
-                      EVP_MAX_IV_LENGTH + EVP_MAX_BLOCK_LENGTH +
-                      EVP_MAX_MD_SIZE + slen))
-        goto err;
-
-    p = ssl_handshake_start(s);
     /*
      * Initialize HMAC and cipher contexts. If callback present it does
      * all the work otherwise use generated values from parent ctx.
@@ -3057,11 +3024,14 @@ int tls_construct_new_session_ticket(SSL *s)
                                              hctx, 1);
 
         if (ret == 0) {
-            l2n(0, p);          /* timeout */
-            s2n(0, p);          /* length */
-            if (!ssl_set_handshake_header
-                (s, SSL3_MT_NEWSESSION_TICKET, p - ssl_handshake_start(s)))
+
+            /* Put timeout and length */
+            if (!WPACKET_put_bytes_u32(pkt, 0)
+                    || !WPACKET_put_bytes_u16(pkt, 0)) {
+                SSLerr(SSL_F_TLS_CONSTRUCT_NEW_SESSION_TICKET,
+                       ERR_R_INTERNAL_ERROR);
                 goto err;
+            }
             OPENSSL_free(senc);
             EVP_CIPHER_CTX_free(ctx);
             HMAC_CTX_free(hctx);
@@ -3092,44 +3062,39 @@ int tls_construct_new_session_ticket(SSL *s)
      * for resumed session (for simplicity), and guess that tickets for
      * new sessions will live as long as their sessions.
      */
-    l2n(s->hit ? 0 : s->session->timeout, p);
-
-    /* Skip ticket length for now */
-    p += 2;
-    /* Output key name */
-    macstart = p;
-    memcpy(p, key_name, sizeof(key_name));
-    p += sizeof(key_name);
-    /* output IV */
-    memcpy(p, iv, iv_len);
-    p += iv_len;
-    /* Encrypt session data */
-    if (!EVP_EncryptUpdate(ctx, p, &len, senc, slen))
-        goto err;
-    p += len;
-    if (!EVP_EncryptFinal(ctx, p, &len))
-        goto err;
-    p += len;
-
-    if (!HMAC_Update(hctx, macstart, p - macstart))
-        goto err;
-    if (!HMAC_Final(hctx, p, &hlen))
+    if (!WPACKET_put_bytes_u32(pkt, s->hit ? 0 : s->session->timeout)
+               /* Now the actual ticket data */
+            || !WPACKET_start_sub_packet_u16(pkt)
+            || !WPACKET_get_total_written(pkt, &macoffset)
+               /* Output key name */
+            || !WPACKET_memcpy(pkt, key_name, sizeof(key_name))
+               /* output IV */
+            || !WPACKET_memcpy(pkt, iv, iv_len)
+            || !WPACKET_reserve_bytes(pkt, slen + EVP_MAX_BLOCK_LENGTH,
+                                      &encdata1)
+               /* Encrypt session data */
+            || !EVP_EncryptUpdate(ctx, encdata1, &len, senc, slen)
+            || !WPACKET_allocate_bytes(pkt, len, &encdata2)
+            || encdata1 != encdata2
+            || !EVP_EncryptFinal(ctx, encdata1 + len, &lenfinal)
+            || !WPACKET_allocate_bytes(pkt, lenfinal, &encdata2)
+            || encdata1 + len != encdata2
+            || len + lenfinal > slen + EVP_MAX_BLOCK_LENGTH
+            || !WPACKET_get_total_written(pkt, &macendoffset)
+            || !HMAC_Update(hctx,
+                            (unsigned char *)s->init_buf->data + macoffset,
+                            macendoffset - macoffset)
+            || !WPACKET_reserve_bytes(pkt, EVP_MAX_MD_SIZE, &macdata1)
+            || !HMAC_Final(hctx, macdata1, &hlen)
+            || hlen > EVP_MAX_MD_SIZE
+            || !WPACKET_allocate_bytes(pkt, hlen, &macdata2)
+            || macdata1 != macdata2
+            || !WPACKET_close(pkt)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_NEW_SESSION_TICKET, ERR_R_INTERNAL_ERROR);
         goto err;
-
+    }
     EVP_CIPHER_CTX_free(ctx);
     HMAC_CTX_free(hctx);
-    ctx = NULL;
-    hctx = NULL;
-
-    p += hlen;
-    /* Now write out lengths: p points to end of data written */
-    /* Total length */
-    len = p - ssl_handshake_start(s);
-    /* Skip ticket lifetime hint */
-    p = ssl_handshake_start(s) + 4;
-    s2n(len - 6, p);
-    if (!ssl_set_handshake_header(s, SSL3_MT_NEWSESSION_TICKET, len))
-        goto err;
     OPENSSL_free(senc);
 
     return 1;
@@ -3137,42 +3102,21 @@ int tls_construct_new_session_ticket(SSL *s)
     OPENSSL_free(senc);
     EVP_CIPHER_CTX_free(ctx);
     HMAC_CTX_free(hctx);
-    ossl_statem_set_error(s);
+    ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
     return 0;
 }
 
-int tls_construct_cert_status(SSL *s)
+int tls_construct_cert_status(SSL *s, WPACKET *pkt)
 {
-    unsigned char *p;
-    size_t msglen;
-
-    /*-
-     * Grow buffer if need be: the length calculation is as
-     * follows handshake_header_length +
-     * 1 (ocsp response type) + 3 (ocsp response length)
-     * + (ocsp response)
-     */
-    msglen = 4 + s->tlsext_ocsp_resplen;
-    if (!BUF_MEM_grow(s->init_buf, SSL_HM_HEADER_LENGTH(s) + msglen))
-        goto err;
-
-    p = ssl_handshake_start(s);
-
-    /* status type */
-    *(p++) = s->tlsext_status_type;
-    /* length of OCSP response */
-    l2n3(s->tlsext_ocsp_resplen, p);
-    /* actual response */
-    memcpy(p, s->tlsext_ocsp_resp, s->tlsext_ocsp_resplen);
-
-    if (!ssl_set_handshake_header(s, SSL3_MT_CERTIFICATE_STATUS, msglen))
-        goto err;
+    if (!WPACKET_put_bytes_u8(pkt, s->tlsext_status_type)
+            || !WPACKET_sub_memcpy_u24(pkt, s->tlsext_ocsp_resp,
+                                       s->tlsext_ocsp_resplen)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_CERT_STATUS, ERR_R_INTERNAL_ERROR);
+        ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
+        return 0;
+    }
 
     return 1;
-
- err:
-    ossl_statem_set_error(s);
-    return 0;
 }
 
 #ifndef OPENSSL_NO_NEXTPROTONEG