Import mbedtls-2.16.0

Imports mbedTLS 2.16.0 from https://github.com/ARMmbed/mbedtls.git
commit fb1972db23da ("Merge pull request #544 from ARMmbed/version-2.16")
(tag mbedtls-2.16.0).

Certain files will never be needed and are thus removed (reducing number
of lines to almost 50%):
rm -f circle.yml CMakeLists.txt DartConfiguration.tcl Makefile
rm -f .gitignore .travis.yml .pylint
rm -f include/.gitignore include/CMakeLists.txt library/.gitignore
rm -f library/CMakeLists.txt library/Makefile
rm -rf .git .github doxygen configs programs scripts tests visualc yotta

This is a complete overwrite of previous code so earlier changes in the
branch import/mbedtls-2.6.1 will be added on top of this commit to bring
the changes forward.

Acked-by: Jerome Forissier <jerome.forissier@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/lib/libmbedtls/mbedtls/library/ssl_tls.c b/lib/libmbedtls/mbedtls/library/ssl_tls.c
index ee7c882..38690fa 100644
--- a/lib/libmbedtls/mbedtls/library/ssl_tls.c
+++ b/lib/libmbedtls/mbedtls/library/ssl_tls.c
@@ -1,8 +1,8 @@
-// SPDX-License-Identifier: Apache-2.0
 /*
  *  SSLv3/TLSv1 shared functions
  *
  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
  *  not use this file except in compliance with the License.
@@ -46,6 +46,7 @@
 #include "mbedtls/debug.h"
 #include "mbedtls/ssl.h"
 #include "mbedtls/ssl_internal.h"
+#include "mbedtls/platform_util.h"
 
 #include <string.h>
 
@@ -53,10 +54,8 @@
 #include "mbedtls/oid.h"
 #endif
 
-/* Implementation that should never be optimized out by the compiler */
-static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
-}
+static void ssl_reset_in_out_pointers( mbedtls_ssl_context *ssl );
+static uint32_t ssl_get_hs_total_len( mbedtls_ssl_context const *ssl );
 
 /* Length of the "epoch" field in the record header */
 static inline size_t ssl_ep_len( const mbedtls_ssl_context *ssl )
@@ -100,7 +99,101 @@
     return( 0 );
 }
 
+static void ssl_update_out_pointers( mbedtls_ssl_context *ssl,
+                                     mbedtls_ssl_transform *transform );
+static void ssl_update_in_pointers( mbedtls_ssl_context *ssl,
+                                    mbedtls_ssl_transform *transform );
+
+#define SSL_DONT_FORCE_FLUSH 0
+#define SSL_FORCE_FLUSH      1
+
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
+
+/* Forward declarations for functions related to message buffering. */
+static void ssl_buffering_free( mbedtls_ssl_context *ssl );
+static void ssl_buffering_free_slot( mbedtls_ssl_context *ssl,
+                                     uint8_t slot );
+static void ssl_free_buffered_record( mbedtls_ssl_context *ssl );
+static int ssl_load_buffered_message( mbedtls_ssl_context *ssl );
+static int ssl_load_buffered_record( mbedtls_ssl_context *ssl );
+static int ssl_buffer_message( mbedtls_ssl_context *ssl );
+static int ssl_buffer_future_record( mbedtls_ssl_context *ssl );
+static int ssl_next_record_is_in_datagram( mbedtls_ssl_context *ssl );
+
+static size_t ssl_get_current_mtu( const mbedtls_ssl_context *ssl );
+static size_t ssl_get_maximum_datagram_size( mbedtls_ssl_context const *ssl )
+{
+    size_t mtu = ssl_get_current_mtu( ssl );
+
+    if( mtu != 0 && mtu < MBEDTLS_SSL_OUT_BUFFER_LEN )
+        return( mtu );
+
+    return( MBEDTLS_SSL_OUT_BUFFER_LEN );
+}
+
+static int ssl_get_remaining_space_in_datagram( mbedtls_ssl_context const *ssl )
+{
+    size_t const bytes_written = ssl->out_left;
+    size_t const mtu           = ssl_get_maximum_datagram_size( ssl );
+
+    /* Double-check that the write-index hasn't gone
+     * past what we can transmit in a single datagram. */
+    if( bytes_written > mtu )
+    {
+        /* Should never happen... */
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    return( (int) ( mtu - bytes_written ) );
+}
+
+static int ssl_get_remaining_payload_in_datagram( mbedtls_ssl_context const *ssl )
+{
+    int ret;
+    size_t remaining, expansion;
+    size_t max_len = MBEDTLS_SSL_OUT_CONTENT_LEN;
+
+#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
+    const size_t mfl = mbedtls_ssl_get_max_frag_len( ssl );
+
+    if( max_len > mfl )
+        max_len = mfl;
+
+    /* By the standard (RFC 6066 Sect. 4), the MFL extension
+     * only limits the maximum record payload size, so in theory
+     * we would be allowed to pack multiple records of payload size
+     * MFL into a single datagram. However, this would mean that there's
+     * no way to explicitly communicate MTU restrictions to the peer.
+     *
+     * The following reduction of max_len makes sure that we never
+     * write datagrams larger than MFL + Record Expansion Overhead.
+     */
+    if( max_len <= ssl->out_left )
+        return( 0 );
+
+    max_len -= ssl->out_left;
+#endif
+
+    ret = ssl_get_remaining_space_in_datagram( ssl );
+    if( ret < 0 )
+        return( ret );
+    remaining = (size_t) ret;
+
+    ret = mbedtls_ssl_get_record_expansion( ssl );
+    if( ret < 0 )
+        return( ret );
+    expansion = (size_t) ret;
+
+    if( remaining <= expansion )
+        return( 0 );
+
+    remaining -= expansion;
+    if( remaining >= max_len )
+        remaining = max_len;
+
+    return( (int) remaining );
+}
+
 /*
  * Double the retransmit timeout value, within the allowed range,
  * returning -1 if the maximum value has already been reached.
@@ -112,6 +205,18 @@
     if( ssl->handshake->retransmit_timeout >= ssl->conf->hs_timeout_max )
         return( -1 );
 
+    /* Implement the final paragraph of RFC 6347 section 4.1.1.1
+     * in the following way: after the initial transmission and a first
+     * retransmission, back off to a temporary estimated MTU of 508 bytes.
+     * This value is guaranteed to be deliverable (if not guaranteed to be
+     * delivered) of any compliant IPv4 (and IPv6) network, and should work
+     * on most non-IP stacks too. */
+    if( ssl->handshake->retransmit_timeout != ssl->conf->hs_timeout_min )
+    {
+        ssl->handshake->mtu = 508;
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "mtu autoreduction to %d bytes", ssl->handshake->mtu ) );
+    }
+
     new_timeout = 2 * ssl->handshake->retransmit_timeout;
 
     /* Avoid arithmetic overflow and range overflow */
@@ -145,14 +250,24 @@
  *    } MaxFragmentLength;
  * and we add 0 -> extension unused
  */
-static unsigned int mfl_code_to_length[MBEDTLS_SSL_MAX_FRAG_LEN_INVALID] =
+static unsigned int ssl_mfl_code_to_length( int mfl )
 {
-    MBEDTLS_SSL_MAX_CONTENT_LEN,    /* MBEDTLS_SSL_MAX_FRAG_LEN_NONE */
-    512,                    /* MBEDTLS_SSL_MAX_FRAG_LEN_512  */
-    1024,                   /* MBEDTLS_SSL_MAX_FRAG_LEN_1024 */
-    2048,                   /* MBEDTLS_SSL_MAX_FRAG_LEN_2048 */
-    4096,                   /* MBEDTLS_SSL_MAX_FRAG_LEN_4096 */
-};
+    switch( mfl )
+    {
+    case MBEDTLS_SSL_MAX_FRAG_LEN_NONE:
+        return ( MBEDTLS_TLS_EXT_ADV_CONTENT_LEN );
+    case MBEDTLS_SSL_MAX_FRAG_LEN_512:
+        return 512;
+    case MBEDTLS_SSL_MAX_FRAG_LEN_1024:
+        return 1024;
+    case MBEDTLS_SSL_MAX_FRAG_LEN_2048:
+        return 2048;
+    case MBEDTLS_SSL_MAX_FRAG_LEN_4096:
+        return 4096;
+    default:
+        return ( MBEDTLS_TLS_EXT_ADV_CONTENT_LEN );
+    }
+}
 #endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
 
 #if defined(MBEDTLS_SSL_CLI_C)
@@ -221,6 +336,7 @@
                      const unsigned char *random, size_t rlen,
                      unsigned char *dstbuf, size_t dlen )
 {
+    int ret = 0;
     size_t i;
     mbedtls_md5_context md5;
     mbedtls_sha1_context sha1;
@@ -243,25 +359,35 @@
     {
         memset( padding, (unsigned char) ('A' + i), 1 + i );
 
-        mbedtls_sha1_starts( &sha1 );
-        mbedtls_sha1_update( &sha1, padding, 1 + i );
-        mbedtls_sha1_update( &sha1, secret, slen );
-        mbedtls_sha1_update( &sha1, random, rlen );
-        mbedtls_sha1_finish( &sha1, sha1sum );
+        if( ( ret = mbedtls_sha1_starts_ret( &sha1 ) ) != 0 )
+            goto exit;
+        if( ( ret = mbedtls_sha1_update_ret( &sha1, padding, 1 + i ) ) != 0 )
+            goto exit;
+        if( ( ret = mbedtls_sha1_update_ret( &sha1, secret, slen ) ) != 0 )
+            goto exit;
+        if( ( ret = mbedtls_sha1_update_ret( &sha1, random, rlen ) ) != 0 )
+            goto exit;
+        if( ( ret = mbedtls_sha1_finish_ret( &sha1, sha1sum ) ) != 0 )
+            goto exit;
 
-        mbedtls_md5_starts( &md5 );
-        mbedtls_md5_update( &md5, secret, slen );
-        mbedtls_md5_update( &md5, sha1sum, 20 );
-        mbedtls_md5_finish( &md5, dstbuf + i * 16 );
+        if( ( ret = mbedtls_md5_starts_ret( &md5 ) ) != 0 )
+            goto exit;
+        if( ( ret = mbedtls_md5_update_ret( &md5, secret, slen ) ) != 0 )
+            goto exit;
+        if( ( ret = mbedtls_md5_update_ret( &md5, sha1sum, 20 ) ) != 0 )
+            goto exit;
+        if( ( ret = mbedtls_md5_finish_ret( &md5, dstbuf + i * 16 ) ) != 0 )
+            goto exit;
     }
 
+exit:
     mbedtls_md5_free(  &md5  );
     mbedtls_sha1_free( &sha1 );
 
-    mbedtls_zeroize( padding, sizeof( padding ) );
-    mbedtls_zeroize( sha1sum, sizeof( sha1sum ) );
+    mbedtls_platform_zeroize( padding, sizeof( padding ) );
+    mbedtls_platform_zeroize( sha1sum, sizeof( sha1sum ) );
 
-    return( 0 );
+    return( ret );
 }
 #endif /* MBEDTLS_SSL_PROTO_SSL3 */
 
@@ -356,8 +482,8 @@
 
     mbedtls_md_free( &md_ctx );
 
-    mbedtls_zeroize( tmp, sizeof( tmp ) );
-    mbedtls_zeroize( h_i, sizeof( h_i ) );
+    mbedtls_platform_zeroize( tmp, sizeof( tmp ) );
+    mbedtls_platform_zeroize( h_i, sizeof( h_i ) );
 
     return( 0 );
 }
@@ -421,8 +547,8 @@
 
     mbedtls_md_free( &md_ctx );
 
-    mbedtls_zeroize( tmp, sizeof( tmp ) );
-    mbedtls_zeroize( h_i, sizeof( h_i ) );
+    mbedtls_platform_zeroize( tmp, sizeof( tmp ) );
+    mbedtls_platform_zeroize( h_i, sizeof( h_i ) );
 
     return( 0 );
 }
@@ -490,6 +616,7 @@
     unsigned char *key2;
     unsigned char *mac_enc;
     unsigned char *mac_dec;
+    size_t mac_key_len;
     size_t iv_copy_len;
     const mbedtls_cipher_info_t *cipher_info;
     const mbedtls_md_info_t *md_info;
@@ -630,7 +757,8 @@
             return( ret );
         }
 
-        mbedtls_zeroize( handshake->premaster, sizeof(handshake->premaster) );
+        mbedtls_platform_zeroize( handshake->premaster,
+                                  sizeof(handshake->premaster) );
     }
     else
         MBEDTLS_SSL_DEBUG_MSG( 3, ( "no premaster (session resumed)" ) );
@@ -641,7 +769,7 @@
     memcpy( tmp, handshake->randbytes, 64 );
     memcpy( handshake->randbytes, tmp + 32, 32 );
     memcpy( handshake->randbytes + 32, tmp, 32 );
-    mbedtls_zeroize( tmp, sizeof( tmp ) );
+    mbedtls_platform_zeroize( tmp, sizeof( tmp ) );
 
     /*
      *  SSLv3:
@@ -669,7 +797,8 @@
     MBEDTLS_SSL_DEBUG_BUF( 4, "random bytes", handshake->randbytes, 64 );
     MBEDTLS_SSL_DEBUG_BUF( 4, "key block", keyblk, 256 );
 
-    mbedtls_zeroize( handshake->randbytes, sizeof( handshake->randbytes ) );
+    mbedtls_platform_zeroize( handshake->randbytes,
+                              sizeof( handshake->randbytes ) );
 
     /*
      * Determine the appropriate key, IV and MAC length.
@@ -678,17 +807,32 @@
     transform->keylen = cipher_info->key_bitlen / 8;
 
     if( cipher_info->mode == MBEDTLS_MODE_GCM ||
-        cipher_info->mode == MBEDTLS_MODE_CCM )
+        cipher_info->mode == MBEDTLS_MODE_CCM ||
+        cipher_info->mode == MBEDTLS_MODE_CHACHAPOLY )
     {
+        size_t taglen, explicit_ivlen;
+
         transform->maclen = 0;
+        mac_key_len = 0;
 
+        /* All modes haves 96-bit IVs;
+         * GCM and CCM has 4 implicit and 8 explicit bytes
+         * ChachaPoly has all 12 bytes implicit
+         */
         transform->ivlen = 12;
-        transform->fixed_ivlen = 4;
+        if( cipher_info->mode == MBEDTLS_MODE_CHACHAPOLY )
+            transform->fixed_ivlen = 12;
+        else
+            transform->fixed_ivlen = 4;
 
-        /* Minimum length is expicit IV + tag */
-        transform->minlen = transform->ivlen - transform->fixed_ivlen
-                            + ( transform->ciphersuite_info->flags &
-                                MBEDTLS_CIPHERSUITE_SHORT_TAG ? 8 : 16 );
+        /* All modes have 128-bit tags, except CCM_8 (ciphersuite flag) */
+        taglen = transform->ciphersuite_info->flags &
+                  MBEDTLS_CIPHERSUITE_SHORT_TAG ? 8 : 16;
+
+
+        /* Minimum length of encrypted record */
+        explicit_ivlen = transform->ivlen - transform->fixed_ivlen;
+        transform->minlen = explicit_ivlen + taglen;
     }
     else
     {
@@ -701,7 +845,8 @@
         }
 
         /* Get MAC length */
-        transform->maclen = mbedtls_md_get_size( md_info );
+        mac_key_len = mbedtls_md_get_size( md_info );
+        transform->maclen = mac_key_len;
 
 #if defined(MBEDTLS_SSL_TRUNCATED_HMAC)
         /*
@@ -710,7 +855,16 @@
          * so we only need to adjust the length here.
          */
         if( session->trunc_hmac == MBEDTLS_SSL_TRUNC_HMAC_ENABLED )
+        {
             transform->maclen = MBEDTLS_SSL_TRUNCATED_HMAC_LEN;
+
+#if defined(MBEDTLS_SSL_TRUNCATED_HMAC_COMPAT)
+            /* Fall back to old, non-compliant version of the truncated
+             * HMAC implementation which also truncates the key
+             * (Mbed TLS versions from 1.3 to 2.6.0) */
+            mac_key_len = transform->maclen;
+#endif
+        }
 #endif /* MBEDTLS_SSL_TRUNCATED_HMAC */
 
         /* IV length */
@@ -772,11 +926,11 @@
 #if defined(MBEDTLS_SSL_CLI_C)
     if( ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT )
     {
-        key1 = keyblk + transform->maclen * 2;
-        key2 = keyblk + transform->maclen * 2 + transform->keylen;
+        key1 = keyblk + mac_key_len * 2;
+        key2 = keyblk + mac_key_len * 2 + transform->keylen;
 
         mac_enc = keyblk;
-        mac_dec = keyblk + transform->maclen;
+        mac_dec = keyblk + mac_key_len;
 
         /*
          * This is not used in TLS v1.1.
@@ -792,10 +946,10 @@
 #if defined(MBEDTLS_SSL_SRV_C)
     if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER )
     {
-        key1 = keyblk + transform->maclen * 2 + transform->keylen;
-        key2 = keyblk + transform->maclen * 2;
+        key1 = keyblk + mac_key_len * 2 + transform->keylen;
+        key2 = keyblk + mac_key_len * 2;
 
-        mac_enc = keyblk + transform->maclen;
+        mac_enc = keyblk + mac_key_len;
         mac_dec = keyblk;
 
         /*
@@ -817,14 +971,14 @@
 #if defined(MBEDTLS_SSL_PROTO_SSL3)
     if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
     {
-        if( transform->maclen > sizeof transform->mac_enc )
+        if( mac_key_len > sizeof transform->mac_enc )
         {
             MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
             return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
         }
 
-        memcpy( transform->mac_enc, mac_enc, transform->maclen );
-        memcpy( transform->mac_dec, mac_dec, transform->maclen );
+        memcpy( transform->mac_enc, mac_enc, mac_key_len );
+        memcpy( transform->mac_dec, mac_dec, mac_key_len );
     }
     else
 #endif /* MBEDTLS_SSL_PROTO_SSL3 */
@@ -832,8 +986,13 @@
     defined(MBEDTLS_SSL_PROTO_TLS1_2)
     if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 )
     {
-        mbedtls_md_hmac_starts( &transform->md_ctx_enc, mac_enc, transform->maclen );
-        mbedtls_md_hmac_starts( &transform->md_ctx_dec, mac_dec, transform->maclen );
+        /* For HMAC-based ciphersuites, initialize the HMAC transforms.
+           For AEAD-based ciphersuites, there is nothing to do here. */
+        if( mac_key_len != 0 )
+        {
+            mbedtls_md_hmac_starts( &transform->md_ctx_enc, mac_enc, mac_key_len );
+            mbedtls_md_hmac_starts( &transform->md_ctx_dec, mac_dec, mac_key_len );
+        }
     }
     else
 #endif
@@ -853,7 +1012,7 @@
                                         transform->iv_enc, transform->iv_dec,
                                         iv_copy_len,
                                         mac_enc, mac_dec,
-                                        transform->maclen ) ) != 0 )
+                                        mac_key_len ) ) != 0 )
         {
             MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_hw_record_init", ret );
             return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
@@ -866,7 +1025,7 @@
     {
         ssl->conf->f_export_keys( ssl->conf->p_export_keys,
                                   session->master, keyblk,
-                                  transform->maclen, transform->keylen,
+                                  mac_key_len, transform->keylen,
                                   iv_copy_len );
     }
 #endif
@@ -920,7 +1079,7 @@
     }
 #endif /* MBEDTLS_CIPHER_MODE_CBC */
 
-    mbedtls_zeroize( keyblk, sizeof( keyblk ) );
+    mbedtls_platform_zeroize( keyblk, sizeof( keyblk ) );
 
 #if defined(MBEDTLS_ZLIB_SUPPORT)
     // Initialize compression
@@ -930,11 +1089,11 @@
         if( ssl->compress_buf == NULL )
         {
             MBEDTLS_SSL_DEBUG_MSG( 3, ( "Allocating compression buffer" ) );
-            ssl->compress_buf = mbedtls_calloc( 1, MBEDTLS_SSL_BUFFER_LEN );
+            ssl->compress_buf = mbedtls_calloc( 1, MBEDTLS_SSL_COMPRESS_BUFFER_LEN );
             if( ssl->compress_buf == NULL )
             {
                 MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed",
-                                    MBEDTLS_SSL_BUFFER_LEN ) );
+                                    MBEDTLS_SSL_COMPRESS_BUFFER_LEN ) );
                 return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
             }
         }
@@ -978,25 +1137,25 @@
     memset( pad_1, 0x36, 48 );
     memset( pad_2, 0x5C, 48 );
 
-    mbedtls_md5_update( &md5, ssl->session_negotiate->master, 48 );
-    mbedtls_md5_update( &md5, pad_1, 48 );
-    mbedtls_md5_finish( &md5, hash );
+    mbedtls_md5_update_ret( &md5, ssl->session_negotiate->master, 48 );
+    mbedtls_md5_update_ret( &md5, pad_1, 48 );
+    mbedtls_md5_finish_ret( &md5, hash );
 
-    mbedtls_md5_starts( &md5 );
-    mbedtls_md5_update( &md5, ssl->session_negotiate->master, 48 );
-    mbedtls_md5_update( &md5, pad_2, 48 );
-    mbedtls_md5_update( &md5, hash,  16 );
-    mbedtls_md5_finish( &md5, hash );
+    mbedtls_md5_starts_ret( &md5 );
+    mbedtls_md5_update_ret( &md5, ssl->session_negotiate->master, 48 );
+    mbedtls_md5_update_ret( &md5, pad_2, 48 );
+    mbedtls_md5_update_ret( &md5, hash,  16 );
+    mbedtls_md5_finish_ret( &md5, hash );
 
-    mbedtls_sha1_update( &sha1, ssl->session_negotiate->master, 48 );
-    mbedtls_sha1_update( &sha1, pad_1, 40 );
-    mbedtls_sha1_finish( &sha1, hash + 16 );
+    mbedtls_sha1_update_ret( &sha1, ssl->session_negotiate->master, 48 );
+    mbedtls_sha1_update_ret( &sha1, pad_1, 40 );
+    mbedtls_sha1_finish_ret( &sha1, hash + 16 );
 
-    mbedtls_sha1_starts( &sha1 );
-    mbedtls_sha1_update( &sha1, ssl->session_negotiate->master, 48 );
-    mbedtls_sha1_update( &sha1, pad_2, 40 );
-    mbedtls_sha1_update( &sha1, hash + 16, 20 );
-    mbedtls_sha1_finish( &sha1, hash + 16 );
+    mbedtls_sha1_starts_ret( &sha1 );
+    mbedtls_sha1_update_ret( &sha1, ssl->session_negotiate->master, 48 );
+    mbedtls_sha1_update_ret( &sha1, pad_2, 40 );
+    mbedtls_sha1_update_ret( &sha1, hash + 16, 20 );
+    mbedtls_sha1_finish_ret( &sha1, hash + 16 );
 
     MBEDTLS_SSL_DEBUG_BUF( 3, "calculated verify result", hash, 36 );
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc verify" ) );
@@ -1022,8 +1181,8 @@
     mbedtls_md5_clone( &md5, &ssl->handshake->fin_md5 );
     mbedtls_sha1_clone( &sha1, &ssl->handshake->fin_sha1 );
 
-     mbedtls_md5_finish( &md5,  hash );
-    mbedtls_sha1_finish( &sha1, hash + 16 );
+     mbedtls_md5_finish_ret( &md5,  hash );
+    mbedtls_sha1_finish_ret( &sha1, hash + 16 );
 
     MBEDTLS_SSL_DEBUG_BUF( 3, "calculated verify result", hash, 36 );
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc verify" ) );
@@ -1046,7 +1205,7 @@
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> calc verify sha256" ) );
 
     mbedtls_sha256_clone( &sha256, &ssl->handshake->fin_sha256 );
-    mbedtls_sha256_finish( &sha256, hash );
+    mbedtls_sha256_finish_ret( &sha256, hash );
 
     MBEDTLS_SSL_DEBUG_BUF( 3, "calculated verify result", hash, 32 );
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc verify" ) );
@@ -1067,7 +1226,7 @@
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> calc verify sha384" ) );
 
     mbedtls_sha512_clone( &sha512, &ssl->handshake->fin_sha512 );
-    mbedtls_sha512_finish( &sha512, hash );
+    mbedtls_sha512_finish_ret( &sha512, hash );
 
     MBEDTLS_SSL_DEBUG_BUF( 3, "calculated verify result", hash, 48 );
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc verify" ) );
@@ -1125,6 +1284,9 @@
          * other_secret already set by the ClientKeyExchange message,
          * and is 48 bytes long
          */
+        if( end - p < 2 )
+            return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
         *p++ = 0;
         *p++ = 48;
         p += 48;
@@ -1171,7 +1333,8 @@
         *(p++) = (unsigned char)( zlen      );
         p += zlen;
 
-        MBEDTLS_SSL_DEBUG_MPI( 3, "ECDH: z", &ssl->handshake->ecdh_ctx.z );
+        MBEDTLS_SSL_DEBUG_ECDH( 3, &ssl->handshake->ecdh_ctx,
+                                MBEDTLS_DEBUG_ECDH_Z );
     }
     else
 #endif /* MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED */
@@ -1203,9 +1366,12 @@
 /*
  * SSLv3.0 MAC functions
  */
-static void ssl_mac( mbedtls_md_context_t *md_ctx, unsigned char *secret,
-                     unsigned char *buf, size_t len,
-                     unsigned char *ctr, int type )
+#define SSL_MAC_MAX_BYTES   20  /* MD-5 or SHA-1 */
+static void ssl_mac( mbedtls_md_context_t *md_ctx,
+                     const unsigned char *secret,
+                     const unsigned char *buf, size_t len,
+                     const unsigned char *ctr, int type,
+                     unsigned char out[SSL_MAC_MAX_BYTES] )
 {
     unsigned char header[11];
     unsigned char padding[48];
@@ -1230,23 +1396,44 @@
     mbedtls_md_update( md_ctx, padding, padlen  );
     mbedtls_md_update( md_ctx, header,  11      );
     mbedtls_md_update( md_ctx, buf,     len     );
-    mbedtls_md_finish( md_ctx, buf +    len     );
+    mbedtls_md_finish( md_ctx, out              );
 
     memset( padding, 0x5C, padlen );
     mbedtls_md_starts( md_ctx );
     mbedtls_md_update( md_ctx, secret,    md_size );
     mbedtls_md_update( md_ctx, padding,   padlen  );
-    mbedtls_md_update( md_ctx, buf + len, md_size );
-    mbedtls_md_finish( md_ctx, buf + len          );
+    mbedtls_md_update( md_ctx, out,       md_size );
+    mbedtls_md_finish( md_ctx, out                );
 }
 #endif /* MBEDTLS_SSL_PROTO_SSL3 */
 
 #if defined(MBEDTLS_ARC4_C) || defined(MBEDTLS_CIPHER_NULL_CIPHER) ||     \
     ( defined(MBEDTLS_CIPHER_MODE_CBC) &&                                  \
-      ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_CAMELLIA_C) ) )
+      ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_CAMELLIA_C) || defined(MBEDTLS_ARIA_C)) )
 #define SSL_SOME_MODES_USE_MAC
 #endif
 
+/* The function below is only used in the Lucky 13 counter-measure in
+ * ssl_decrypt_buf(). These are the defines that guard the call site. */
+#if defined(SSL_SOME_MODES_USE_MAC) && \
+    ( defined(MBEDTLS_SSL_PROTO_TLS1) || \
+      defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
+      defined(MBEDTLS_SSL_PROTO_TLS1_2) )
+/* This function makes sure every byte in the memory region is accessed
+ * (in ascending addresses order) */
+static void ssl_read_memory( unsigned char *p, size_t len )
+{
+    unsigned char acc = 0;
+    volatile unsigned char force;
+
+    for( ; len != 0; p++, len-- )
+        acc ^= *p;
+
+    force = acc;
+    (void) force;
+}
+#endif /* SSL_SOME_MODES_USE_MAC && ( TLS1 || TLS1_1 || TLS1_2 ) */
+
 /*
  * Encryption/decryption functions
  */
@@ -1282,10 +1469,15 @@
 #if defined(MBEDTLS_SSL_PROTO_SSL3)
         if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
         {
+            unsigned char mac[SSL_MAC_MAX_BYTES];
+
             ssl_mac( &ssl->transform_out->md_ctx_enc,
                       ssl->transform_out->mac_enc,
                       ssl->out_msg, ssl->out_msglen,
-                      ssl->out_ctr, ssl->out_msgtype );
+                      ssl->out_ctr, ssl->out_msgtype,
+                      mac );
+
+            memcpy( ssl->out_msg + ssl->out_msglen, mac, ssl->transform_out->maclen );
         }
         else
 #endif
@@ -1293,14 +1485,17 @@
         defined(MBEDTLS_SSL_PROTO_TLS1_2)
         if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 )
         {
+            unsigned char mac[MBEDTLS_SSL_MAC_ADD];
+
             mbedtls_md_hmac_update( &ssl->transform_out->md_ctx_enc, ssl->out_ctr, 8 );
             mbedtls_md_hmac_update( &ssl->transform_out->md_ctx_enc, ssl->out_hdr, 3 );
             mbedtls_md_hmac_update( &ssl->transform_out->md_ctx_enc, ssl->out_len, 2 );
             mbedtls_md_hmac_update( &ssl->transform_out->md_ctx_enc,
                              ssl->out_msg, ssl->out_msglen );
-            mbedtls_md_hmac_finish( &ssl->transform_out->md_ctx_enc,
-                             ssl->out_msg + ssl->out_msglen );
+            mbedtls_md_hmac_finish( &ssl->transform_out->md_ctx_enc, mac );
             mbedtls_md_hmac_reset( &ssl->transform_out->md_ctx_enc );
+
+            memcpy( ssl->out_msg + ssl->out_msglen, mac, ssl->transform_out->maclen );
         }
         else
 #endif
@@ -1349,17 +1544,26 @@
     }
     else
 #endif /* MBEDTLS_ARC4_C || MBEDTLS_CIPHER_NULL_CIPHER */
-#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CCM_C)
+#if defined(MBEDTLS_GCM_C) || \
+    defined(MBEDTLS_CCM_C) || \
+    defined(MBEDTLS_CHACHAPOLY_C)
     if( mode == MBEDTLS_MODE_GCM ||
-        mode == MBEDTLS_MODE_CCM )
+        mode == MBEDTLS_MODE_CCM ||
+        mode == MBEDTLS_MODE_CHACHAPOLY )
     {
         int ret;
         size_t enc_msglen, olen;
         unsigned char *enc_msg;
         unsigned char add_data[13];
-        unsigned char taglen = ssl->transform_out->ciphersuite_info->flags &
+        unsigned char iv[12];
+        mbedtls_ssl_transform *transform = ssl->transform_out;
+        unsigned char taglen = transform->ciphersuite_info->flags &
                                MBEDTLS_CIPHERSUITE_SHORT_TAG ? 8 : 16;
+        size_t explicit_ivlen = transform->ivlen - transform->fixed_ivlen;
 
+        /*
+         * Prepare additional authenticated data
+         */
         memcpy( add_data, ssl->out_ctr, 8 );
         add_data[8]  = ssl->out_msgtype;
         mbedtls_ssl_write_version( ssl->major_ver, ssl->minor_ver,
@@ -1367,44 +1571,57 @@
         add_data[11] = ( ssl->out_msglen >> 8 ) & 0xFF;
         add_data[12] = ssl->out_msglen & 0xFF;
 
-        MBEDTLS_SSL_DEBUG_BUF( 4, "additional data used for AEAD",
-                       add_data, 13 );
+        MBEDTLS_SSL_DEBUG_BUF( 4, "additional data for AEAD", add_data, 13 );
 
         /*
          * Generate IV
          */
-        if( ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen != 8 )
+        if( transform->ivlen == 12 && transform->fixed_ivlen == 4 )
+        {
+            /* GCM and CCM: fixed || explicit (=seqnum) */
+            memcpy( iv, transform->iv_enc, transform->fixed_ivlen );
+            memcpy( iv + transform->fixed_ivlen, ssl->out_ctr, 8 );
+            memcpy( ssl->out_iv, ssl->out_ctr, 8 );
+
+        }
+        else if( transform->ivlen == 12 && transform->fixed_ivlen == 12 )
+        {
+            /* ChachaPoly: fixed XOR sequence number */
+            unsigned char i;
+
+            memcpy( iv, transform->iv_enc, transform->fixed_ivlen );
+
+            for( i = 0; i < 8; i++ )
+                iv[i+4] ^= ssl->out_ctr[i];
+        }
+        else
         {
             /* Reminder if we ever add an AEAD mode with a different size */
             MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
             return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
         }
 
-        memcpy( ssl->transform_out->iv_enc + ssl->transform_out->fixed_ivlen,
-                             ssl->out_ctr, 8 );
-        memcpy( ssl->out_iv, ssl->out_ctr, 8 );
-
-        MBEDTLS_SSL_DEBUG_BUF( 4, "IV used", ssl->out_iv,
-                ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen );
+        MBEDTLS_SSL_DEBUG_BUF( 4, "IV used (internal)",
+                                  iv, transform->ivlen );
+        MBEDTLS_SSL_DEBUG_BUF( 4, "IV used (transmitted)",
+                                  ssl->out_iv, explicit_ivlen );
 
         /*
-         * Fix pointer positions and message length with added IV
+         * Fix message length with added IV
          */
         enc_msg = ssl->out_msg;
         enc_msglen = ssl->out_msglen;
-        ssl->out_msglen += ssl->transform_out->ivlen -
-                           ssl->transform_out->fixed_ivlen;
+        ssl->out_msglen += explicit_ivlen;
 
         MBEDTLS_SSL_DEBUG_MSG( 3, ( "before encrypt: msglen = %d, "
-                            "including %d bytes of padding",
-                       ssl->out_msglen, 0 ) );
+                                    "including 0 bytes of padding",
+                                    ssl->out_msglen ) );
 
         /*
          * Encrypt and authenticate
          */
-        if( ( ret = mbedtls_cipher_auth_encrypt( &ssl->transform_out->cipher_ctx_enc,
-                                         ssl->transform_out->iv_enc,
-                                         ssl->transform_out->ivlen,
+        if( ( ret = mbedtls_cipher_auth_encrypt( &transform->cipher_ctx_enc,
+                                         iv, transform->ivlen,
                                          add_data, 13,
                                          enc_msg, enc_msglen,
                                          enc_msg, &olen,
@@ -1428,7 +1645,7 @@
     else
 #endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C */
 #if defined(MBEDTLS_CIPHER_MODE_CBC) &&                                    \
-    ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_CAMELLIA_C) )
+    ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_CAMELLIA_C) || defined(MBEDTLS_ARIA_C) )
     if( mode == MBEDTLS_MODE_CBC )
     {
         int ret;
@@ -1511,6 +1728,8 @@
 #if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
         if( auth_done == 0 )
         {
+            unsigned char mac[MBEDTLS_SSL_MAC_ADD];
+
             /*
              * MAC(MAC_write_key, seq_num +
              *     TLSCipherText.type +
@@ -1533,10 +1752,12 @@
             mbedtls_md_hmac_update( &ssl->transform_out->md_ctx_enc, pseudo_hdr, 13 );
             mbedtls_md_hmac_update( &ssl->transform_out->md_ctx_enc,
                              ssl->out_iv, ssl->out_msglen );
-            mbedtls_md_hmac_finish( &ssl->transform_out->md_ctx_enc,
-                             ssl->out_iv + ssl->out_msglen );
+            mbedtls_md_hmac_finish( &ssl->transform_out->md_ctx_enc, mac );
             mbedtls_md_hmac_reset( &ssl->transform_out->md_ctx_enc );
 
+            memcpy( ssl->out_iv + ssl->out_msglen, mac,
+                    ssl->transform_out->maclen );
+
             ssl->out_msglen += ssl->transform_out->maclen;
             auth_done++;
         }
@@ -1544,7 +1765,7 @@
     }
     else
 #endif /* MBEDTLS_CIPHER_MODE_CBC &&
-          ( MBEDTLS_AES_C || MBEDTLS_CAMELLIA_C ) */
+          ( MBEDTLS_AES_C || MBEDTLS_CAMELLIA_C || MBEDTLS_ARIA_C ) */
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
         return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
@@ -1562,11 +1783,8 @@
     return( 0 );
 }
 
-#define SSL_MAX_MAC_SIZE   48
-
 static int ssl_decrypt_buf( mbedtls_ssl_context *ssl )
 {
-    size_t i;
     mbedtls_cipher_mode_t mode;
     int auth_done = 0;
 #if defined(SSL_SOME_MODES_USE_MAC)
@@ -1616,20 +1834,27 @@
     }
     else
 #endif /* MBEDTLS_ARC4_C || MBEDTLS_CIPHER_NULL_CIPHER */
-#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CCM_C)
+#if defined(MBEDTLS_GCM_C) || \
+    defined(MBEDTLS_CCM_C) || \
+    defined(MBEDTLS_CHACHAPOLY_C)
     if( mode == MBEDTLS_MODE_GCM ||
-        mode == MBEDTLS_MODE_CCM )
+        mode == MBEDTLS_MODE_CCM ||
+        mode == MBEDTLS_MODE_CHACHAPOLY )
     {
         int ret;
         size_t dec_msglen, olen;
         unsigned char *dec_msg;
         unsigned char *dec_msg_result;
         unsigned char add_data[13];
-        unsigned char taglen = ssl->transform_in->ciphersuite_info->flags &
+        unsigned char iv[12];
+        mbedtls_ssl_transform *transform = ssl->transform_in;
+        unsigned char taglen = transform->ciphersuite_info->flags &
                                MBEDTLS_CIPHERSUITE_SHORT_TAG ? 8 : 16;
-        size_t explicit_iv_len = ssl->transform_in->ivlen -
-                                 ssl->transform_in->fixed_ivlen;
+        size_t explicit_iv_len = transform->ivlen - transform->fixed_ivlen;
 
+        /*
+         * Compute and update sizes
+         */
         if( ssl->in_msglen < explicit_iv_len + taglen )
         {
             MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%d) < explicit_iv_len (%d) "
@@ -1643,6 +1868,9 @@
         dec_msg_result = ssl->in_msg;
         ssl->in_msglen = dec_msglen;
 
+        /*
+         * Prepare additional authenticated data
+         */
         memcpy( add_data, ssl->in_ctr, 8 );
         add_data[8]  = ssl->in_msgtype;
         mbedtls_ssl_write_version( ssl->major_ver, ssl->minor_ver,
@@ -1650,23 +1878,43 @@
         add_data[11] = ( ssl->in_msglen >> 8 ) & 0xFF;
         add_data[12] = ssl->in_msglen & 0xFF;
 
-        MBEDTLS_SSL_DEBUG_BUF( 4, "additional data used for AEAD",
-                       add_data, 13 );
+        MBEDTLS_SSL_DEBUG_BUF( 4, "additional data for AEAD", add_data, 13 );
 
-        memcpy( ssl->transform_in->iv_dec + ssl->transform_in->fixed_ivlen,
-                ssl->in_iv,
-                ssl->transform_in->ivlen - ssl->transform_in->fixed_ivlen );
+        /*
+         * Prepare IV
+         */
+        if( transform->ivlen == 12 && transform->fixed_ivlen == 4 )
+        {
+            /* GCM and CCM: fixed || explicit (transmitted) */
+            memcpy( iv, transform->iv_dec, transform->fixed_ivlen );
+            memcpy( iv + transform->fixed_ivlen, ssl->in_iv, 8 );
 
-        MBEDTLS_SSL_DEBUG_BUF( 4, "IV used", ssl->transform_in->iv_dec,
-                                     ssl->transform_in->ivlen );
+        }
+        else if( transform->ivlen == 12 && transform->fixed_ivlen == 12 )
+        {
+            /* ChachaPoly: fixed XOR sequence number */
+            unsigned char i;
+
+            memcpy( iv, transform->iv_dec, transform->fixed_ivlen );
+
+            for( i = 0; i < 8; i++ )
+                iv[i+4] ^= ssl->in_ctr[i];
+        }
+        else
+        {
+            /* Reminder if we ever add an AEAD mode with a different size */
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
+        MBEDTLS_SSL_DEBUG_BUF( 4, "IV used", iv, transform->ivlen );
         MBEDTLS_SSL_DEBUG_BUF( 4, "TAG used", dec_msg + dec_msglen, taglen );
 
         /*
          * Decrypt and authenticate
          */
         if( ( ret = mbedtls_cipher_auth_decrypt( &ssl->transform_in->cipher_ctx_dec,
-                                         ssl->transform_in->iv_dec,
-                                         ssl->transform_in->ivlen,
+                                         iv, transform->ivlen,
                                          add_data, 13,
                                          dec_msg, dec_msglen,
                                          dec_msg_result, &olen,
@@ -1690,7 +1938,7 @@
     else
 #endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C */
 #if defined(MBEDTLS_CIPHER_MODE_CBC) &&                                    \
-    ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_CAMELLIA_C) )
+    ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_CAMELLIA_C) || defined(MBEDTLS_ARIA_C) )
     if( mode == MBEDTLS_MODE_CBC )
     {
         /*
@@ -1731,7 +1979,7 @@
 #if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
         if( ssl->session_in->encrypt_then_mac == MBEDTLS_SSL_ETM_ENABLED )
         {
-            unsigned char computed_mac[SSL_MAX_MAC_SIZE];
+            unsigned char mac_expect[MBEDTLS_SSL_MAC_ADD];
             unsigned char pseudo_hdr[13];
 
             MBEDTLS_SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) );
@@ -1749,16 +1997,16 @@
             mbedtls_md_hmac_update( &ssl->transform_in->md_ctx_dec, pseudo_hdr, 13 );
             mbedtls_md_hmac_update( &ssl->transform_in->md_ctx_dec,
                              ssl->in_iv, ssl->in_msglen );
-            mbedtls_md_hmac_finish( &ssl->transform_in->md_ctx_dec, computed_mac );
+            mbedtls_md_hmac_finish( &ssl->transform_in->md_ctx_dec, mac_expect );
             mbedtls_md_hmac_reset( &ssl->transform_in->md_ctx_dec );
 
             MBEDTLS_SSL_DEBUG_BUF( 4, "message  mac", ssl->in_iv + ssl->in_msglen,
                                               ssl->transform_in->maclen );
-            MBEDTLS_SSL_DEBUG_BUF( 4, "computed mac", computed_mac,
+            MBEDTLS_SSL_DEBUG_BUF( 4, "expected mac", mac_expect,
                                               ssl->transform_in->maclen );
 
-            if( mbedtls_ssl_safer_memcmp( ssl->in_iv + ssl->in_msglen, computed_mac,
-                              ssl->transform_in->maclen ) != 0 )
+            if( mbedtls_ssl_safer_memcmp( ssl->in_iv + ssl->in_msglen, mac_expect,
+                                          ssl->transform_in->maclen ) != 0 )
             {
                 MBEDTLS_SSL_DEBUG_MSG( 1, ( "message mac does not match" ) );
 
@@ -1784,6 +2032,7 @@
          */
         if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
         {
+            unsigned char i;
             dec_msglen -= ssl->transform_in->ivlen;
             ssl->in_msglen -= ssl->transform_in->ivlen;
 
@@ -1857,27 +2106,28 @@
              * and fake check up to 256 bytes of padding
              */
             size_t pad_count = 0, real_count = 1;
-            size_t padding_idx = ssl->in_msglen - padlen - 1;
+            size_t padding_idx = ssl->in_msglen - padlen;
+            size_t i;
 
             /*
              * Padding is guaranteed to be incorrect if:
-             *   1. padlen >= ssl->in_msglen
+             *   1. padlen > ssl->in_msglen
              *
-             *   2. padding_idx >= MBEDTLS_SSL_MAX_CONTENT_LEN +
+             *   2. padding_idx > MBEDTLS_SSL_IN_CONTENT_LEN +
              *                     ssl->transform_in->maclen
              *
              * In both cases we reset padding_idx to a safe value (0) to
              * prevent out-of-buffer reads.
              */
-            correct &= ( ssl->in_msglen >= padlen + 1 );
-            correct &= ( padding_idx < MBEDTLS_SSL_MAX_CONTENT_LEN +
+            correct &= ( padlen <= ssl->in_msglen );
+            correct &= ( padding_idx <= MBEDTLS_SSL_IN_CONTENT_LEN +
                                        ssl->transform_in->maclen );
 
             padding_idx *= correct;
 
-            for( i = 1; i <= 256; i++ )
+            for( i = 0; i < 256; i++ )
             {
-                real_count &= ( i <= padlen );
+                real_count &= ( i < padlen );
                 pad_count += real_count *
                              ( ssl->in_msg[padding_idx + i] == padlen - 1 );
             }
@@ -1902,14 +2152,16 @@
     }
     else
 #endif /* MBEDTLS_CIPHER_MODE_CBC &&
-          ( MBEDTLS_AES_C || MBEDTLS_CAMELLIA_C ) */
+          ( MBEDTLS_AES_C || MBEDTLS_CAMELLIA_C || MBEDTLS_ARIA_C ) */
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
         return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
     }
 
+#if defined(MBEDTLS_SSL_DEBUG_ALL)
     MBEDTLS_SSL_DEBUG_BUF( 4, "raw buffer after decryption",
                    ssl->in_msg, ssl->in_msglen );
+#endif
 
     /*
      * Authenticate if not done yet.
@@ -1918,22 +2170,21 @@
 #if defined(SSL_SOME_MODES_USE_MAC)
     if( auth_done == 0 )
     {
-        unsigned char tmp[SSL_MAX_MAC_SIZE];
+        unsigned char mac_expect[MBEDTLS_SSL_MAC_ADD];
 
         ssl->in_msglen -= ssl->transform_in->maclen;
 
         ssl->in_len[0] = (unsigned char)( ssl->in_msglen >> 8 );
         ssl->in_len[1] = (unsigned char)( ssl->in_msglen      );
 
-        memcpy( tmp, ssl->in_msg + ssl->in_msglen, ssl->transform_in->maclen );
-
 #if defined(MBEDTLS_SSL_PROTO_SSL3)
         if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
         {
             ssl_mac( &ssl->transform_in->md_ctx_dec,
                       ssl->transform_in->mac_dec,
                       ssl->in_msg, ssl->in_msglen,
-                      ssl->in_ctr, ssl->in_msgtype );
+                      ssl->in_ctr, ssl->in_msgtype,
+                      mac_expect );
         }
         else
 #endif /* MBEDTLS_SSL_PROTO_SSL3 */
@@ -1943,20 +2194,69 @@
         {
             /*
              * Process MAC and always update for padlen afterwards to make
-             * total time independent of padlen
-             *
-             * extra_run compensates MAC check for padlen
+             * total time independent of padlen.
              *
              * Known timing attacks:
              *  - Lucky Thirteen (http://www.isg.rhul.ac.uk/tls/TLStiming.pdf)
              *
-             * We use ( ( Lx + 8 ) / 64 ) to handle 'negative Lx' values
-             * correctly. (We round down instead of up, so -56 is the correct
-             * value for our calculations instead of -55)
+             * To compensate for different timings for the MAC calculation
+             * depending on how much padding was removed (which is determined
+             * by padlen), process extra_run more blocks through the hash
+             * function.
+             *
+             * The formula in the paper is
+             *   extra_run = ceil( (L1-55) / 64 ) - ceil( (L2-55) / 64 )
+             * where L1 is the size of the header plus the decrypted message
+             * plus CBC padding and L2 is the size of the header plus the
+             * decrypted message. This is for an underlying hash function
+             * with 64-byte blocks.
+             * We use ( (Lx+8) / 64 ) to handle 'negative Lx' values
+             * correctly. We round down instead of up, so -56 is the correct
+             * value for our calculations instead of -55.
+             *
+             * Repeat the formula rather than defining a block_size variable.
+             * This avoids requiring division by a variable at runtime
+             * (which would be marginally less efficient and would require
+             * linking an extra division function in some builds).
              */
             size_t j, extra_run = 0;
-            extra_run = ( 13 + ssl->in_msglen + padlen + 8 ) / 64 -
-                        ( 13 + ssl->in_msglen          + 8 ) / 64;
+
+            /*
+             * The next two sizes are the minimum and maximum values of
+             * in_msglen over all padlen values.
+             *
+             * They're independent of padlen, since we previously did
+             * in_msglen -= padlen.
+             *
+             * Note that max_len + maclen is never more than the buffer
+             * length, as we previously did in_msglen -= maclen too.
+             */
+            const size_t max_len = ssl->in_msglen + padlen;
+            const size_t min_len = ( max_len > 256 ) ? max_len - 256 : 0;
+
+            switch( ssl->transform_in->ciphersuite_info->mac )
+            {
+#if defined(MBEDTLS_MD5_C) || defined(MBEDTLS_SHA1_C) || \
+    defined(MBEDTLS_SHA256_C)
+                case MBEDTLS_MD_MD5:
+                case MBEDTLS_MD_SHA1:
+                case MBEDTLS_MD_SHA256:
+                    /* 8 bytes of message size, 64-byte compression blocks */
+                    extra_run = ( 13 + ssl->in_msglen + padlen + 8 ) / 64 -
+                                ( 13 + ssl->in_msglen          + 8 ) / 64;
+                    break;
+#endif
+#if defined(MBEDTLS_SHA512_C)
+                case MBEDTLS_MD_SHA384:
+                    /* 16 bytes of message size, 128-byte compression blocks */
+                    extra_run = ( 13 + ssl->in_msglen + padlen + 16 ) / 128 -
+                                ( 13 + ssl->in_msglen          + 16 ) / 128;
+                    break;
+#endif
+                default:
+                    MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+                    return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+            }
 
             extra_run &= correct * 0xFF;
 
@@ -1965,13 +2265,25 @@
             mbedtls_md_hmac_update( &ssl->transform_in->md_ctx_dec, ssl->in_len, 2 );
             mbedtls_md_hmac_update( &ssl->transform_in->md_ctx_dec, ssl->in_msg,
                              ssl->in_msglen );
-            mbedtls_md_hmac_finish( &ssl->transform_in->md_ctx_dec,
-                             ssl->in_msg + ssl->in_msglen );
-            /* Call mbedtls_md_process at least once due to cache attacks */
+            /* Make sure we access everything even when padlen > 0. This
+             * makes the synchronisation requirements for just-in-time
+             * Prime+Probe attacks much tighter and hopefully impractical. */
+            ssl_read_memory( ssl->in_msg + ssl->in_msglen, padlen );
+            mbedtls_md_hmac_finish( &ssl->transform_in->md_ctx_dec, mac_expect );
+
+            /* Call mbedtls_md_process at least once due to cache attacks
+             * that observe whether md_process() was called of not */
             for( j = 0; j < extra_run + 1; j++ )
                 mbedtls_md_process( &ssl->transform_in->md_ctx_dec, ssl->in_msg );
 
             mbedtls_md_hmac_reset( &ssl->transform_in->md_ctx_dec );
+
+            /* Make sure we access all the memory that could contain the MAC,
+             * before we check it in the next code block. This makes the
+             * synchronisation requirements for just-in-time Prime+Probe
+             * attacks much tighter and hopefully impractical. */
+            ssl_read_memory( ssl->in_msg + min_len,
+                                 max_len - min_len + ssl->transform_in->maclen );
         }
         else
 #endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 || \
@@ -1981,12 +2293,14 @@
             return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
         }
 
-        MBEDTLS_SSL_DEBUG_BUF( 4, "message  mac", tmp, ssl->transform_in->maclen );
-        MBEDTLS_SSL_DEBUG_BUF( 4, "computed mac", ssl->in_msg + ssl->in_msglen,
-                       ssl->transform_in->maclen );
+#if defined(MBEDTLS_SSL_DEBUG_ALL)
+        MBEDTLS_SSL_DEBUG_BUF( 4, "expected mac", mac_expect, ssl->transform_in->maclen );
+        MBEDTLS_SSL_DEBUG_BUF( 4, "message  mac", ssl->in_msg + ssl->in_msglen,
+                               ssl->transform_in->maclen );
+#endif
 
-        if( mbedtls_ssl_safer_memcmp( tmp, ssl->in_msg + ssl->in_msglen,
-                         ssl->transform_in->maclen ) != 0 )
+        if( mbedtls_ssl_safer_memcmp( ssl->in_msg + ssl->in_msglen, mac_expect,
+                                      ssl->transform_in->maclen ) != 0 )
         {
 #if defined(MBEDTLS_SSL_DEBUG_ALL)
             MBEDTLS_SSL_DEBUG_MSG( 1, ( "message mac does not match" ) );
@@ -1994,13 +2308,13 @@
             correct = 0;
         }
         auth_done++;
-
-        /*
-         * Finally check the correct flag
-         */
-        if( correct == 0 )
-            return( MBEDTLS_ERR_SSL_INVALID_MAC );
     }
+
+    /*
+     * Finally check the correct flag
+     */
+    if( correct == 0 )
+        return( MBEDTLS_ERR_SSL_INVALID_MAC );
 #endif /* SSL_SOME_MODES_USE_MAC */
 
     /* Make extra sure authentication was performed, exactly once */
@@ -2012,6 +2326,16 @@
 
     if( ssl->in_msglen == 0 )
     {
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
+        if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_3
+            && ssl->in_msgtype != MBEDTLS_SSL_MSG_APPLICATION_DATA )
+        {
+            /* TLS v1.2 explicitly disallows zero-length messages which are not application data */
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid zero-length message type: %d", ssl->in_msgtype ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
+
         ssl->nb_zero++;
 
         /*
@@ -2036,6 +2360,7 @@
     else
 #endif
     {
+        unsigned char i;
         for( i = 8; i > ssl_ep_len( ssl ); i-- )
             if( ++ssl->in_ctr[i - 1] != 0 )
                 break;
@@ -2065,6 +2390,7 @@
 {
     int ret;
     unsigned char *msg_post = ssl->out_msg;
+    ptrdiff_t bytes_written = ssl->out_msg - ssl->out_buf;
     size_t len_pre = ssl->out_msglen;
     unsigned char *msg_pre = ssl->compress_buf;
 
@@ -2084,7 +2410,7 @@
     ssl->transform_out->ctx_deflate.next_in = msg_pre;
     ssl->transform_out->ctx_deflate.avail_in = len_pre;
     ssl->transform_out->ctx_deflate.next_out = msg_post;
-    ssl->transform_out->ctx_deflate.avail_out = MBEDTLS_SSL_BUFFER_LEN;
+    ssl->transform_out->ctx_deflate.avail_out = MBEDTLS_SSL_OUT_BUFFER_LEN - bytes_written;
 
     ret = deflate( &ssl->transform_out->ctx_deflate, Z_SYNC_FLUSH );
     if( ret != Z_OK )
@@ -2093,8 +2419,8 @@
         return( MBEDTLS_ERR_SSL_COMPRESSION_FAILED );
     }
 
-    ssl->out_msglen = MBEDTLS_SSL_BUFFER_LEN -
-                      ssl->transform_out->ctx_deflate.avail_out;
+    ssl->out_msglen = MBEDTLS_SSL_OUT_BUFFER_LEN -
+                      ssl->transform_out->ctx_deflate.avail_out - bytes_written;
 
     MBEDTLS_SSL_DEBUG_MSG( 3, ( "after compression: msglen = %d, ",
                    ssl->out_msglen ) );
@@ -2111,6 +2437,7 @@
 {
     int ret;
     unsigned char *msg_post = ssl->in_msg;
+    ptrdiff_t header_bytes = ssl->in_msg - ssl->in_buf;
     size_t len_pre = ssl->in_msglen;
     unsigned char *msg_pre = ssl->compress_buf;
 
@@ -2130,7 +2457,8 @@
     ssl->transform_in->ctx_inflate.next_in = msg_pre;
     ssl->transform_in->ctx_inflate.avail_in = len_pre;
     ssl->transform_in->ctx_inflate.next_out = msg_post;
-    ssl->transform_in->ctx_inflate.avail_out = MBEDTLS_SSL_MAX_CONTENT_LEN;
+    ssl->transform_in->ctx_inflate.avail_out = MBEDTLS_SSL_IN_BUFFER_LEN -
+                                               header_bytes;
 
     ret = inflate( &ssl->transform_in->ctx_inflate, Z_SYNC_FLUSH );
     if( ret != Z_OK )
@@ -2139,8 +2467,8 @@
         return( MBEDTLS_ERR_SSL_COMPRESSION_FAILED );
     }
 
-    ssl->in_msglen = MBEDTLS_SSL_MAX_CONTENT_LEN -
-                     ssl->transform_in->ctx_inflate.avail_out;
+    ssl->in_msglen = MBEDTLS_SSL_IN_BUFFER_LEN -
+                     ssl->transform_in->ctx_inflate.avail_out - header_bytes;
 
     MBEDTLS_SSL_DEBUG_MSG( 3, ( "after decompression: msglen = %d, ",
                    ssl->in_msglen ) );
@@ -2214,7 +2542,7 @@
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
     }
 
-    if( nb_want > MBEDTLS_SSL_BUFFER_LEN - (size_t)( ssl->in_hdr - ssl->in_buf ) )
+    if( nb_want > MBEDTLS_SSL_IN_BUFFER_LEN - (size_t)( ssl->in_hdr - ssl->in_buf ) )
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "requesting more data than fits" ) );
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
@@ -2294,10 +2622,13 @@
          * that will end up being dropped.
          */
         if( ssl_check_timer( ssl ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "timer has expired" ) );
             ret = MBEDTLS_ERR_SSL_TIMEOUT;
+        }
         else
         {
-            len = MBEDTLS_SSL_BUFFER_LEN - ( ssl->in_hdr - ssl->in_buf );
+            len = MBEDTLS_SSL_IN_BUFFER_LEN - ( ssl->in_hdr - ssl->in_buf );
 
             if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER )
                 timeout = ssl->handshake->retransmit_timeout;
@@ -2396,6 +2727,14 @@
             if( ret < 0 )
                 return( ret );
 
+            if ( (size_t)ret > len || ( INT_MAX > SIZE_MAX && ret > SIZE_MAX ) )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1,
+                    ( "f_recv returned %d bytes but only %lu were requested",
+                    ret, (unsigned long)len ) );
+                return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+            }
+
             ssl->in_left += ret;
         }
     }
@@ -2411,7 +2750,7 @@
 int mbedtls_ssl_flush_output( mbedtls_ssl_context *ssl )
 {
     int ret;
-    unsigned char *buf, i;
+    unsigned char *buf;
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> flush output" ) );
 
@@ -2434,8 +2773,7 @@
         MBEDTLS_SSL_DEBUG_MSG( 2, ( "message length: %d, out_left: %d",
                        mbedtls_ssl_hdr_len( ssl ) + ssl->out_msglen, ssl->out_left ) );
 
-        buf = ssl->out_hdr + mbedtls_ssl_hdr_len( ssl ) +
-              ssl->out_msglen - ssl->out_left;
+        buf = ssl->out_hdr - ssl->out_left;
         ret = ssl->f_send( ssl->p_bio, buf, ssl->out_left );
 
         MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_send", ret );
@@ -2443,19 +2781,28 @@
         if( ret <= 0 )
             return( ret );
 
+        if( (size_t)ret > ssl->out_left || ( INT_MAX > SIZE_MAX && ret > SIZE_MAX ) )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1,
+                ( "f_send returned %d bytes but only %lu bytes were sent",
+                ret, (unsigned long)ssl->out_left ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
         ssl->out_left -= ret;
     }
 
-    for( i = 8; i > ssl_ep_len( ssl ); i-- )
-        if( ++ssl->out_ctr[i - 1] != 0 )
-            break;
-
-    /* The loop goes to its end iff the counter is wrapping */
-    if( i == ssl_ep_len( ssl ) )
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
     {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "outgoing message counter would wrap" ) );
-        return( MBEDTLS_ERR_SSL_COUNTER_WRAPPING );
+        ssl->out_hdr = ssl->out_buf;
     }
+    else
+#endif
+    {
+        ssl->out_hdr = ssl->out_buf + 8;
+    }
+    ssl_update_out_pointers( ssl, ssl->transform_out );
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= flush output" ) );
 
@@ -2472,6 +2819,9 @@
 static int ssl_flight_append( mbedtls_ssl_context *ssl )
 {
     mbedtls_ssl_flight_item *msg;
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_flight_append" ) );
+    MBEDTLS_SSL_DEBUG_BUF( 4, "message appended to flight",
+                           ssl->out_msg, ssl->out_msglen );
 
     /* Allocate space for current message */
     if( ( msg = mbedtls_calloc( 1, sizeof(  mbedtls_ssl_flight_item ) ) ) == NULL )
@@ -2505,6 +2855,7 @@
         cur->next = msg;
     }
 
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_flight_append" ) );
     return( 0 );
 }
 
@@ -2553,19 +2904,12 @@
     ssl->handshake->alt_transform_out = tmp_transform;
 
     /* Swap epoch + sequence_number */
-    memcpy( tmp_out_ctr,                 ssl->out_ctr,                8 );
-    memcpy( ssl->out_ctr,                ssl->handshake->alt_out_ctr, 8 );
+    memcpy( tmp_out_ctr,                 ssl->cur_out_ctr,            8 );
+    memcpy( ssl->cur_out_ctr,            ssl->handshake->alt_out_ctr, 8 );
     memcpy( ssl->handshake->alt_out_ctr, tmp_out_ctr,                 8 );
 
     /* Adjust to the newly activated transform */
-    if( ssl->transform_out != NULL &&
-        ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
-    {
-        ssl->out_msg = ssl->out_iv + ssl->transform_out->ivlen -
-                                     ssl->transform_out->fixed_ivlen;
-    }
-    else
-        ssl->out_msg = ssl->out_iv;
+    ssl_update_out_pointers( ssl, ssl->transform_out );
 
 #if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
     if( mbedtls_ssl_hw_record_activate != NULL )
@@ -2581,20 +2925,38 @@
 
 /*
  * Retransmit the current flight of messages.
+ */
+int mbedtls_ssl_resend( mbedtls_ssl_context *ssl )
+{
+    int ret = 0;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_resend" ) );
+
+    ret = mbedtls_ssl_flight_transmit( ssl );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_resend" ) );
+
+    return( ret );
+}
+
+/*
+ * Transmit or retransmit the current flight of messages.
  *
  * Need to remember the current message in case flush_output returns
  * WANT_WRITE, causing us to exit this function and come back later.
  * This function must be called until state is no longer SENDING.
  */
-int mbedtls_ssl_resend( mbedtls_ssl_context *ssl )
+int mbedtls_ssl_flight_transmit( mbedtls_ssl_context *ssl )
 {
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_resend" ) );
+    int ret;
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_flight_transmit" ) );
 
     if( ssl->handshake->retransmit_state != MBEDTLS_SSL_RETRANS_SENDING )
     {
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialise resending" ) );
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialise flight transmission" ) );
 
         ssl->handshake->cur_msg = ssl->handshake->flight;
+        ssl->handshake->cur_msg_p = ssl->handshake->flight->p + 12;
         ssl_swap_epochs( ssl );
 
         ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_SENDING;
@@ -2602,33 +2964,129 @@
 
     while( ssl->handshake->cur_msg != NULL )
     {
-        int ret;
-        mbedtls_ssl_flight_item *cur = ssl->handshake->cur_msg;
+        size_t max_frag_len;
+        const mbedtls_ssl_flight_item * const cur = ssl->handshake->cur_msg;
+
+        int const is_finished =
+            ( cur->type == MBEDTLS_SSL_MSG_HANDSHAKE &&
+              cur->p[0] == MBEDTLS_SSL_HS_FINISHED );
+
+        uint8_t const force_flush = ssl->disable_datagram_packing == 1 ?
+            SSL_FORCE_FLUSH : SSL_DONT_FORCE_FLUSH;
 
         /* Swap epochs before sending Finished: we can't do it after
          * sending ChangeCipherSpec, in case write returns WANT_READ.
          * Must be done before copying, may change out_msg pointer */
-        if( cur->type == MBEDTLS_SSL_MSG_HANDSHAKE &&
-            cur->p[0] == MBEDTLS_SSL_HS_FINISHED )
+        if( is_finished && ssl->handshake->cur_msg_p == ( cur->p + 12 ) )
         {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "swap epochs to send finished message" ) );
             ssl_swap_epochs( ssl );
         }
 
-        memcpy( ssl->out_msg, cur->p, cur->len );
-        ssl->out_msglen = cur->len;
-        ssl->out_msgtype = cur->type;
+        ret = ssl_get_remaining_payload_in_datagram( ssl );
+        if( ret < 0 )
+            return( ret );
+        max_frag_len = (size_t) ret;
 
-        ssl->handshake->cur_msg = cur->next;
+        /* CCS is copied as is, while HS messages may need fragmentation */
+        if( cur->type == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC )
+        {
+            if( max_frag_len == 0 )
+            {
+                if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
+                    return( ret );
 
-        MBEDTLS_SSL_DEBUG_BUF( 3, "resent handshake message header", ssl->out_msg, 12 );
+                continue;
+            }
 
-        if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+            memcpy( ssl->out_msg, cur->p, cur->len );
+            ssl->out_msglen  = cur->len;
+            ssl->out_msgtype = cur->type;
+
+            /* Update position inside current message */
+            ssl->handshake->cur_msg_p += cur->len;
+        }
+        else
+        {
+            const unsigned char * const p = ssl->handshake->cur_msg_p;
+            const size_t hs_len = cur->len - 12;
+            const size_t frag_off = p - ( cur->p + 12 );
+            const size_t rem_len = hs_len - frag_off;
+            size_t cur_hs_frag_len, max_hs_frag_len;
+
+            if( ( max_frag_len < 12 ) || ( max_frag_len == 12 && hs_len != 0 ) )
+            {
+                if( is_finished )
+                    ssl_swap_epochs( ssl );
+
+                if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
+                    return( ret );
+
+                continue;
+            }
+            max_hs_frag_len = max_frag_len - 12;
+
+            cur_hs_frag_len = rem_len > max_hs_frag_len ?
+                max_hs_frag_len : rem_len;
+
+            if( frag_off == 0 && cur_hs_frag_len != hs_len )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "fragmenting handshake message (%u > %u)",
+                                            (unsigned) cur_hs_frag_len,
+                                            (unsigned) max_hs_frag_len ) );
+            }
+
+            /* Messages are stored with handshake headers as if not fragmented,
+             * copy beginning of headers then fill fragmentation fields.
+             * Handshake headers: type(1) len(3) seq(2) f_off(3) f_len(3) */
+            memcpy( ssl->out_msg, cur->p, 6 );
+
+            ssl->out_msg[6] = ( ( frag_off >> 16 ) & 0xff );
+            ssl->out_msg[7] = ( ( frag_off >>  8 ) & 0xff );
+            ssl->out_msg[8] = ( ( frag_off       ) & 0xff );
+
+            ssl->out_msg[ 9] = ( ( cur_hs_frag_len >> 16 ) & 0xff );
+            ssl->out_msg[10] = ( ( cur_hs_frag_len >>  8 ) & 0xff );
+            ssl->out_msg[11] = ( ( cur_hs_frag_len       ) & 0xff );
+
+            MBEDTLS_SSL_DEBUG_BUF( 3, "handshake header", ssl->out_msg, 12 );
+
+            /* Copy the handshake message content and set records fields */
+            memcpy( ssl->out_msg + 12, p, cur_hs_frag_len );
+            ssl->out_msglen = cur_hs_frag_len + 12;
+            ssl->out_msgtype = cur->type;
+
+            /* Update position inside current message */
+            ssl->handshake->cur_msg_p += cur_hs_frag_len;
+        }
+
+        /* If done with the current message move to the next one if any */
+        if( ssl->handshake->cur_msg_p >= cur->p + cur->len )
+        {
+            if( cur->next != NULL )
+            {
+                ssl->handshake->cur_msg = cur->next;
+                ssl->handshake->cur_msg_p = cur->next->p + 12;
+            }
+            else
+            {
+                ssl->handshake->cur_msg = NULL;
+                ssl->handshake->cur_msg_p = NULL;
+            }
+        }
+
+        /* Actually send the message out */
+        if( ( ret = mbedtls_ssl_write_record( ssl, force_flush ) ) != 0 )
         {
             MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
             return( ret );
         }
     }
 
+    if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
+        return( ret );
+
+    /* Update state and set timer */
     if( ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER )
         ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_FINISHED;
     else
@@ -2637,7 +3095,7 @@
         ssl_set_timer( ssl, ssl->handshake->retransmit_timeout );
     }
 
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_resend" ) );
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_flight_transmit" ) );
 
     return( 0 );
 }
@@ -2655,6 +3113,12 @@
     /* The next incoming flight will start with this msg_seq */
     ssl->handshake->in_flight_start_seq = ssl->handshake->in_msg_seq;
 
+    /* We don't want to remember CCS's across flight boundaries. */
+    ssl->handshake->buffering.seen_ccs = 0;
+
+    /* Clear future message buffering structure. */
+    ssl_buffering_free( ssl );
+
     /* Cancel timer */
     ssl_set_timer( ssl, 0 );
 
@@ -2686,43 +3150,102 @@
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
 /*
- * Record layer functions
+ * Handshake layer functions
  */
 
 /*
- * Write current record.
- * Uses ssl->out_msgtype, ssl->out_msglen and bytes at ssl->out_msg.
+ * Write (DTLS: or queue) current handshake (including CCS) message.
+ *
+ *  - fill in handshake headers
+ *  - update handshake checksum
+ *  - DTLS: save message for resending
+ *  - then pass to the record layer
+ *
+ * DTLS: except for HelloRequest, messages are only queued, and will only be
+ * actually sent when calling flight_transmit() or resend().
+ *
+ * Inputs:
+ *  - ssl->out_msglen: 4 + actual handshake message len
+ *      (4 is the size of handshake headers for TLS)
+ *  - ssl->out_msg[0]: the handshake type (ClientHello, ServerHello, etc)
+ *  - ssl->out_msg + 4: the handshake message body
+ *
+ * Outputs, ie state before passing to flight_append() or write_record():
+ *   - ssl->out_msglen: the length of the record contents
+ *      (including handshake headers but excluding record headers)
+ *   - ssl->out_msg: the record contents (handshake headers + content)
  */
-int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl )
+int mbedtls_ssl_write_handshake_msg( mbedtls_ssl_context *ssl )
 {
-    int ret, done = 0, out_msg_type;
-    size_t len = ssl->out_msglen;
+    int ret;
+    const size_t hs_len = ssl->out_msglen - 4;
+    const unsigned char hs_type = ssl->out_msg[0];
 
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write record" ) );
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write handshake message" ) );
+
+    /*
+     * Sanity checks
+     */
+    if( ssl->out_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE          &&
+        ssl->out_msgtype != MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC )
+    {
+        /* In SSLv3, the client might send a NoCertificate alert. */
+#if defined(MBEDTLS_SSL_PROTO_SSL3) && defined(MBEDTLS_SSL_CLI_C)
+        if( ! ( ssl->minor_ver      == MBEDTLS_SSL_MINOR_VERSION_0 &&
+                ssl->out_msgtype    == MBEDTLS_SSL_MSG_ALERT       &&
+                ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT ) )
+#endif /* MBEDTLS_SSL_PROTO_SSL3 && MBEDTLS_SSL_SRV_C */
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+    }
+
+    /* Whenever we send anything different from a
+     * HelloRequest we should be in a handshake - double check. */
+    if( ! ( ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE &&
+            hs_type          == MBEDTLS_SSL_HS_HELLO_REQUEST ) &&
+        ssl->handshake == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
         ssl->handshake != NULL &&
         ssl->handshake->retransmit_state == MBEDTLS_SSL_RETRANS_SENDING )
     {
-        ; /* Skip special handshake treatment when resending */
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
     }
-    else
 #endif
+
+    /* Double-check that we did not exceed the bounds
+     * of the outgoing record buffer.
+     * This should never fail as the various message
+     * writing functions must obey the bounds of the
+     * outgoing record buffer, but better be safe.
+     *
+     * Note: We deliberately do not check for the MTU or MFL here.
+     */
+    if( ssl->out_msglen > MBEDTLS_SSL_OUT_CONTENT_LEN )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "Record too large: "
+                                    "size %u, maximum %u",
+                                    (unsigned) ssl->out_msglen,
+                                    (unsigned) MBEDTLS_SSL_OUT_CONTENT_LEN ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    /*
+     * Fill handshake headers
+     */
     if( ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE )
     {
-        out_msg_type = ssl->out_msg[0];
-
-        if( out_msg_type != MBEDTLS_SSL_HS_HELLO_REQUEST &&
-            ssl->handshake == NULL )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
-            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
-        }
-
-        ssl->out_msg[1] = (unsigned char)( ( len - 4 ) >> 16 );
-        ssl->out_msg[2] = (unsigned char)( ( len - 4 ) >>  8 );
-        ssl->out_msg[3] = (unsigned char)( ( len - 4 )       );
+        ssl->out_msg[1] = (unsigned char)( hs_len >> 16 );
+        ssl->out_msg[2] = (unsigned char)( hs_len >>  8 );
+        ssl->out_msg[3] = (unsigned char)( hs_len       );
 
         /*
          * DTLS has additional fields in the Handshake layer,
@@ -2735,12 +3258,20 @@
         if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
         {
             /* Make room for the additional DTLS fields */
-            memmove( ssl->out_msg + 12, ssl->out_msg + 4, len - 4 );
+            if( MBEDTLS_SSL_OUT_CONTENT_LEN - ssl->out_msglen < 8 )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "DTLS handshake message too large: "
+                              "size %u, maximum %u",
+                               (unsigned) ( hs_len ),
+                               (unsigned) ( MBEDTLS_SSL_OUT_CONTENT_LEN - 12 ) ) );
+                return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+            }
+
+            memmove( ssl->out_msg + 12, ssl->out_msg + 4, hs_len );
             ssl->out_msglen += 8;
-            len += 8;
 
             /* Write message_seq and update it, except for HelloRequest */
-            if( out_msg_type != MBEDTLS_SSL_HS_HELLO_REQUEST )
+            if( hs_type != MBEDTLS_SSL_HS_HELLO_REQUEST )
             {
                 ssl->out_msg[4] = ( ssl->handshake->out_msg_seq >> 8 ) & 0xFF;
                 ssl->out_msg[5] = ( ssl->handshake->out_msg_seq      ) & 0xFF;
@@ -2752,23 +3283,23 @@
                 ssl->out_msg[5] = 0;
             }
 
-            /* We don't fragment, so frag_offset = 0 and frag_len = len */
+            /* Handshake hashes are computed without fragmentation,
+             * so set frag_offset = 0 and frag_len = hs_len for now */
             memset( ssl->out_msg + 6, 0x00, 3 );
             memcpy( ssl->out_msg + 9, ssl->out_msg + 1, 3 );
         }
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
-        if( out_msg_type != MBEDTLS_SSL_HS_HELLO_REQUEST )
-            ssl->handshake->update_checksum( ssl, ssl->out_msg, len );
+        /* Update running hashes of handshake messages seen */
+        if( hs_type != MBEDTLS_SSL_HS_HELLO_REQUEST )
+            ssl->handshake->update_checksum( ssl, ssl->out_msg, ssl->out_msglen );
     }
 
-    /* Save handshake and CCS messages for resending */
+    /* Either send now, or just save to be sent (and resent) later */
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
-        ssl->handshake != NULL &&
-        ssl->handshake->retransmit_state != MBEDTLS_SSL_RETRANS_SENDING &&
-        ( ssl->out_msgtype == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC ||
-          ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE ) )
+        ! ( ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE &&
+            hs_type          == MBEDTLS_SSL_HS_HELLO_REQUEST ) )
     {
         if( ( ret = ssl_flight_append( ssl ) ) != 0 )
         {
@@ -2776,7 +3307,40 @@
             return( ret );
         }
     }
+    else
 #endif
+    {
+        if( ( ret = mbedtls_ssl_write_record( ssl, SSL_FORCE_FLUSH ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "ssl_write_record", ret );
+            return( ret );
+        }
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write handshake message" ) );
+
+    return( 0 );
+}
+
+/*
+ * Record layer functions
+ */
+
+/*
+ * Write current record.
+ *
+ * Uses:
+ *  - ssl->out_msgtype: type of the message (AppData, Handshake, Alert, CCS)
+ *  - ssl->out_msglen: length of the record content (excl headers)
+ *  - ssl->out_msg: record content
+ */
+int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl, uint8_t force_flush )
+{
+    int ret, done = 0;
+    size_t len = ssl->out_msglen;
+    uint8_t flush = force_flush;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write record" ) );
 
 #if defined(MBEDTLS_ZLIB_SUPPORT)
     if( ssl->transform_out != NULL &&
@@ -2810,10 +3374,14 @@
 #endif /* MBEDTLS_SSL_HW_RECORD_ACCEL */
     if( !done )
     {
+        unsigned i;
+        size_t protected_record_size;
+
         ssl->out_hdr[0] = (unsigned char) ssl->out_msgtype;
         mbedtls_ssl_write_version( ssl->major_ver, ssl->minor_ver,
                            ssl->conf->transport, ssl->out_hdr + 1 );
 
+        memcpy( ssl->out_ctr, ssl->cur_out_ctr, 8 );
         ssl->out_len[0] = (unsigned char)( len >> 8 );
         ssl->out_len[1] = (unsigned char)( len      );
 
@@ -2830,18 +3398,76 @@
             ssl->out_len[1] = (unsigned char)( len      );
         }
 
-        ssl->out_left = mbedtls_ssl_hdr_len( ssl ) + ssl->out_msglen;
+        protected_record_size = len + mbedtls_ssl_hdr_len( ssl );
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+        /* In case of DTLS, double-check that we don't exceed
+         * the remaining space in the datagram. */
+        if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+        {
+            ret = ssl_get_remaining_space_in_datagram( ssl );
+            if( ret < 0 )
+                return( ret );
+
+            if( protected_record_size > (size_t) ret )
+            {
+                /* Should never happen */
+                return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+            }
+        }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 
         MBEDTLS_SSL_DEBUG_MSG( 3, ( "output record: msgtype = %d, "
-                            "version = [%d:%d], msglen = %d",
-                       ssl->out_hdr[0], ssl->out_hdr[1], ssl->out_hdr[2],
-                     ( ssl->out_len[0] << 8 ) | ssl->out_len[1] ) );
+                                    "version = [%d:%d], msglen = %d",
+                                    ssl->out_hdr[0], ssl->out_hdr[1],
+                                    ssl->out_hdr[2], len ) );
 
         MBEDTLS_SSL_DEBUG_BUF( 4, "output record sent to network",
-                       ssl->out_hdr, mbedtls_ssl_hdr_len( ssl ) + ssl->out_msglen );
+                               ssl->out_hdr, protected_record_size );
+
+        ssl->out_left += protected_record_size;
+        ssl->out_hdr  += protected_record_size;
+        ssl_update_out_pointers( ssl, ssl->transform_out );
+
+        for( i = 8; i > ssl_ep_len( ssl ); i-- )
+            if( ++ssl->cur_out_ctr[i - 1] != 0 )
+                break;
+
+        /* The loop goes to its end iff the counter is wrapping */
+        if( i == ssl_ep_len( ssl ) )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "outgoing message counter would wrap" ) );
+            return( MBEDTLS_ERR_SSL_COUNTER_WRAPPING );
+        }
     }
 
-    if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+        flush == SSL_DONT_FORCE_FLUSH )
+    {
+        size_t remaining;
+        ret = ssl_get_remaining_payload_in_datagram( ssl );
+        if( ret < 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "ssl_get_remaining_payload_in_datagram",
+                                   ret );
+            return( ret );
+        }
+
+        remaining = (size_t) ret;
+        if( remaining == 0 )
+        {
+            flush = SSL_FORCE_FLUSH;
+        }
+        else
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "Still %u bytes available in current datagram", (unsigned) remaining ) );
+        }
+    }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+    if( ( flush == SSL_FORCE_FLUSH ) &&
+        ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flush_output", ret );
         return( ret );
@@ -2853,6 +3479,52 @@
 }
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
+
+static int ssl_hs_is_proper_fragment( mbedtls_ssl_context *ssl )
+{
+    if( ssl->in_msglen < ssl->in_hslen ||
+        memcmp( ssl->in_msg + 6, "\0\0\0",        3 ) != 0 ||
+        memcmp( ssl->in_msg + 9, ssl->in_msg + 1, 3 ) != 0 )
+    {
+        return( 1 );
+    }
+    return( 0 );
+}
+
+static uint32_t ssl_get_hs_frag_len( mbedtls_ssl_context const *ssl )
+{
+    return( ( ssl->in_msg[9] << 16  ) |
+            ( ssl->in_msg[10] << 8  ) |
+              ssl->in_msg[11] );
+}
+
+static uint32_t ssl_get_hs_frag_off( mbedtls_ssl_context const *ssl )
+{
+    return( ( ssl->in_msg[6] << 16 ) |
+            ( ssl->in_msg[7] << 8  ) |
+              ssl->in_msg[8] );
+}
+
+static int ssl_check_hs_header( mbedtls_ssl_context const *ssl )
+{
+    uint32_t msg_len, frag_off, frag_len;
+
+    msg_len  = ssl_get_hs_total_len( ssl );
+    frag_off = ssl_get_hs_frag_off( ssl );
+    frag_len = ssl_get_hs_frag_len( ssl );
+
+    if( frag_off > msg_len )
+        return( -1 );
+
+    if( frag_len > msg_len - frag_off )
+        return( -1 );
+
+    if( frag_len + 12 > ssl->in_msglen )
+        return( -1 );
+
+    return( 0 );
+}
+
 /*
  * Mark bits in bitmask (used for DTLS HS reassembly)
  */
@@ -2914,162 +3586,30 @@
     return( 0 );
 }
 
-/*
- * Reassemble fragmented DTLS handshake messages.
- *
- * Use a temporary buffer for reassembly, divided in two parts:
- * - the first holds the reassembled message (including handshake header),
- * - the second holds a bitmask indicating which parts of the message
- *   (excluding headers) have been received so far.
- */
-static int ssl_reassemble_dtls_handshake( mbedtls_ssl_context *ssl )
+/* msg_len does not include the handshake header */
+static size_t ssl_get_reassembly_buffer_size( size_t msg_len,
+                                              unsigned add_bitmap )
 {
-    unsigned char *msg, *bitmask;
-    size_t frag_len, frag_off;
-    size_t msg_len = ssl->in_hslen - 12; /* Without headers */
+    size_t alloc_len;
 
-    if( ssl->handshake == NULL )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "not supported outside handshake (for now)" ) );
-        return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
-    }
+    alloc_len  = 12;                                 /* Handshake header */
+    alloc_len += msg_len;                            /* Content buffer   */
 
-    /*
-     * For first fragment, check size and allocate buffer
-     */
-    if( ssl->handshake->hs_msg == NULL )
-    {
-        size_t alloc_len;
+    if( add_bitmap )
+        alloc_len += msg_len / 8 + ( msg_len % 8 != 0 ); /* Bitmap       */
 
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialize reassembly, total length = %d",
-                            msg_len ) );
-
-        if( ssl->in_hslen > MBEDTLS_SSL_MAX_CONTENT_LEN )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake message too large" ) );
-            return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
-        }
-
-        /* The bitmask needs one bit per byte of message excluding header */
-        alloc_len = 12 + msg_len + msg_len / 8 + ( msg_len % 8 != 0 );
-
-        ssl->handshake->hs_msg = mbedtls_calloc( 1, alloc_len );
-        if( ssl->handshake->hs_msg == NULL )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc failed (%d bytes)", alloc_len ) );
-            return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
-        }
-
-        /* Prepare final header: copy msg_type, length and message_seq,
-         * then add standardised fragment_offset and fragment_length */
-        memcpy( ssl->handshake->hs_msg, ssl->in_msg, 6 );
-        memset( ssl->handshake->hs_msg + 6, 0, 3 );
-        memcpy( ssl->handshake->hs_msg + 9,
-                ssl->handshake->hs_msg + 1, 3 );
-    }
-    else
-    {
-        /* Make sure msg_type and length are consistent */
-        if( memcmp( ssl->handshake->hs_msg, ssl->in_msg, 4 ) != 0 )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "fragment header mismatch" ) );
-            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-        }
-    }
-
-    msg = ssl->handshake->hs_msg + 12;
-    bitmask = msg + msg_len;
-
-    /*
-     * Check and copy current fragment
-     */
-    frag_off = ( ssl->in_msg[6]  << 16 ) |
-               ( ssl->in_msg[7]  << 8  ) |
-                 ssl->in_msg[8];
-    frag_len = ( ssl->in_msg[9]  << 16 ) |
-               ( ssl->in_msg[10] << 8  ) |
-                 ssl->in_msg[11];
-
-    if( frag_off + frag_len > msg_len )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid fragment offset/len: %d + %d > %d",
-                          frag_off, frag_len, msg_len ) );
-        return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-    }
-
-    if( frag_len + 12 > ssl->in_msglen )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid fragment length: %d + 12 > %d",
-                          frag_len, ssl->in_msglen ) );
-        return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-    }
-
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "adding fragment, offset = %d, length = %d",
-                        frag_off, frag_len ) );
-
-    memcpy( msg + frag_off, ssl->in_msg + 12, frag_len );
-    ssl_bitmask_set( bitmask, frag_off, frag_len );
-
-    /*
-     * Do we have the complete message by now?
-     * If yes, finalize it, else ask to read the next record.
-     */
-    if( ssl_bitmask_check( bitmask, msg_len ) != 0 )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "message is not complete yet" ) );
-        return( MBEDTLS_ERR_SSL_WANT_READ );
-    }
-
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "handshake message completed" ) );
-
-    if( frag_len + 12 < ssl->in_msglen )
-    {
-        /*
-         * We'got more handshake messages in the same record.
-         * This case is not handled now because no know implementation does
-         * that and it's hard to test, so we prefer to fail cleanly for now.
-         */
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "last fragment not alone in its record" ) );
-        return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
-    }
-
-    if( ssl->in_left > ssl->next_record_offset )
-    {
-        /*
-         * We've got more data in the buffer after the current record,
-         * that we don't want to overwrite. Move it before writing the
-         * reassembled message, and adjust in_left and next_record_offset.
-         */
-        unsigned char *cur_remain = ssl->in_hdr + ssl->next_record_offset;
-        unsigned char *new_remain = ssl->in_msg + ssl->in_hslen;
-        size_t remain_len = ssl->in_left - ssl->next_record_offset;
-
-        /* First compute and check new lengths */
-        ssl->next_record_offset = new_remain - ssl->in_hdr;
-        ssl->in_left = ssl->next_record_offset + remain_len;
-
-        if( ssl->in_left > MBEDTLS_SSL_BUFFER_LEN -
-                           (size_t)( ssl->in_hdr - ssl->in_buf ) )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "reassembled message too large for buffer" ) );
-            return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
-        }
-
-        memmove( new_remain, cur_remain, remain_len );
-    }
-
-    memcpy( ssl->in_msg, ssl->handshake->hs_msg, ssl->in_hslen );
-
-    mbedtls_free( ssl->handshake->hs_msg );
-    ssl->handshake->hs_msg = NULL;
-
-    MBEDTLS_SSL_DEBUG_BUF( 3, "reassembled handshake message",
-                   ssl->in_msg, ssl->in_hslen );
-
-    return( 0 );
+    return( alloc_len );
 }
+
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
+static uint32_t ssl_get_hs_total_len( mbedtls_ssl_context const *ssl )
+{
+    return( ( ssl->in_msg[1] << 16 ) |
+            ( ssl->in_msg[2] << 8  ) |
+              ssl->in_msg[3] );
+}
+
 int mbedtls_ssl_prepare_handshake_record( mbedtls_ssl_context *ssl )
 {
     if( ssl->in_msglen < mbedtls_ssl_hs_hdr_len( ssl ) )
@@ -3079,10 +3619,7 @@
         return( MBEDTLS_ERR_SSL_INVALID_RECORD );
     }
 
-    ssl->in_hslen = mbedtls_ssl_hs_hdr_len( ssl ) + (
-                    ( ssl->in_msg[1] << 16 ) |
-                    ( ssl->in_msg[2] << 8  ) |
-                      ssl->in_msg[3] );
+    ssl->in_hslen = mbedtls_ssl_hs_hdr_len( ssl ) + ssl_get_hs_total_len( ssl );
 
     MBEDTLS_SSL_DEBUG_MSG( 3, ( "handshake message: msglen ="
                         " %d, type = %d, hslen = %d",
@@ -3094,10 +3631,26 @@
         int ret;
         unsigned int recv_msg_seq = ( ssl->in_msg[4] << 8 ) | ssl->in_msg[5];
 
-        /* ssl->handshake is NULL when receiving ClientHello for renego */
-        if( ssl->handshake != NULL &&
-            recv_msg_seq != ssl->handshake->in_msg_seq )
+        if( ssl_check_hs_header( ssl ) != 0 )
         {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid handshake header" ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
+        if( ssl->handshake != NULL &&
+            ( ( ssl->state   != MBEDTLS_SSL_HANDSHAKE_OVER &&
+                recv_msg_seq != ssl->handshake->in_msg_seq ) ||
+              ( ssl->state  == MBEDTLS_SSL_HANDSHAKE_OVER &&
+                ssl->in_msg[0] != MBEDTLS_SSL_HS_CLIENT_HELLO ) ) )
+        {
+            if( recv_msg_seq > ssl->handshake->in_msg_seq )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "received future handshake message of sequence number %u (next %u)",
+                                            recv_msg_seq,
+                                            ssl->handshake->in_msg_seq ) );
+                return( MBEDTLS_ERR_SSL_EARLY_MESSAGE );
+            }
+
             /* Retransmit only on last message from previous flight, to avoid
              * too many retransmissions.
              * Besides, No sane server ever retransmits HelloVerifyRequest */
@@ -3123,24 +3676,18 @@
                                     ssl->handshake->in_msg_seq ) );
             }
 
-            return( MBEDTLS_ERR_SSL_WANT_READ );
+            return( MBEDTLS_ERR_SSL_CONTINUE_PROCESSING );
         }
         /* Wait until message completion to increment in_msg_seq */
 
-        /* Reassemble if current message is fragmented or reassembly is
-         * already in progress */
-        if( ssl->in_msglen < ssl->in_hslen ||
-            memcmp( ssl->in_msg + 6, "\0\0\0",        3 ) != 0 ||
-            memcmp( ssl->in_msg + 9, ssl->in_msg + 1, 3 ) != 0 ||
-            ( ssl->handshake != NULL && ssl->handshake->hs_msg != NULL ) )
+        /* Message reassembly is handled alongside buffering of future
+         * messages; the commonality is that both handshake fragments and
+         * future messages cannot be forwarded immediately to the
+         * handshake logic layer. */
+        if( ssl_hs_is_proper_fragment( ssl ) == 1 )
         {
             MBEDTLS_SSL_DEBUG_MSG( 2, ( "found fragmented DTLS handshake message" ) );
-
-            if( ( ret = ssl_reassemble_dtls_handshake( ssl ) ) != 0 )
-            {
-                MBEDTLS_SSL_DEBUG_RET( 1, "ssl_reassemble_dtls_handshake", ret );
-                return( ret );
-            }
+            return( MBEDTLS_ERR_SSL_EARLY_MESSAGE );
         }
     }
     else
@@ -3157,9 +3704,9 @@
 
 void mbedtls_ssl_update_handshake_status( mbedtls_ssl_context *ssl )
 {
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
 
-    if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER &&
-        ssl->handshake != NULL )
+    if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER && hs != NULL )
     {
         ssl->handshake->update_checksum( ssl, ssl->in_msg, ssl->in_hslen );
     }
@@ -3169,7 +3716,29 @@
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
         ssl->handshake != NULL )
     {
-        ssl->handshake->in_msg_seq++;
+        unsigned offset;
+        mbedtls_ssl_hs_buffer *hs_buf;
+
+        /* Increment handshake sequence number */
+        hs->in_msg_seq++;
+
+        /*
+         * Clear up handshake buffering and reassembly structure.
+         */
+
+        /* Free first entry */
+        ssl_buffering_free_slot( ssl, 0 );
+
+        /* Shift all other entries */
+        for( offset = 0, hs_buf = &hs->buffering.hs[0];
+             offset + 1 < MBEDTLS_SSL_MAX_BUFFERED_HS;
+             offset++, hs_buf++ )
+        {
+            *hs_buf = *(hs_buf + 1);
+        }
+
+        /* Create a fresh last entry */
+        memset( hs_buf, 0, sizeof( mbedtls_ssl_hs_buffer ) );
     }
 #endif
 }
@@ -3422,7 +3991,7 @@
             ssl->conf->p_cookie,
             ssl->cli_id, ssl->cli_id_len,
             ssl->in_buf, ssl->in_left,
-            ssl->out_buf, MBEDTLS_SSL_MAX_CONTENT_LEN, &len );
+            ssl->out_buf, MBEDTLS_SSL_OUT_CONTENT_LEN, &len );
 
     MBEDTLS_SSL_DEBUG_RET( 2, "ssl_check_dtls_clihlo_cookie", ret );
 
@@ -3493,8 +4062,15 @@
         ssl->in_msgtype != MBEDTLS_SSL_MSG_APPLICATION_DATA )
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "unknown record type" ) );
-        mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
-                                        MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE );
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+        /* Silently ignore invalid DTLS records as recommended by RFC 6347
+         * Section 4.1.2.7 */
+        if( ssl->conf->transport != MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+            mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+                                    MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE );
+
         return( MBEDTLS_ERR_SSL_INVALID_RECORD );
     }
 
@@ -3512,88 +4088,30 @@
     }
 
     /* Check length against the size of our buffer */
-    if( ssl->in_msglen > MBEDTLS_SSL_BUFFER_LEN
+    if( ssl->in_msglen > MBEDTLS_SSL_IN_BUFFER_LEN
                          - (size_t)( ssl->in_msg - ssl->in_buf ) )
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
         return( MBEDTLS_ERR_SSL_INVALID_RECORD );
     }
 
-    /* Check length against bounds of the current transform and version */
-    if( ssl->transform_in == NULL )
-    {
-        if( ssl->in_msglen < 1 ||
-            ssl->in_msglen > MBEDTLS_SSL_MAX_CONTENT_LEN )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
-            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-        }
-    }
-    else
-    {
-        if( ssl->in_msglen < ssl->transform_in->minlen )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
-            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-        }
-
-#if defined(MBEDTLS_SSL_PROTO_SSL3)
-        if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 &&
-            ssl->in_msglen > ssl->transform_in->minlen + MBEDTLS_SSL_MAX_CONTENT_LEN )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
-            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-        }
-#endif
-#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
-    defined(MBEDTLS_SSL_PROTO_TLS1_2)
-        /*
-         * TLS encrypted messages can have up to 256 bytes of padding
-         */
-        if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 &&
-            ssl->in_msglen > ssl->transform_in->minlen +
-                             MBEDTLS_SSL_MAX_CONTENT_LEN + 256 )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
-            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-        }
-#endif
-    }
-
     /*
-     * DTLS-related tests done last, because most of them may result in
-     * silently dropping the record (but not the whole datagram), and we only
-     * want to consider that after ensuring that the "basic" fields (type,
-     * version, length) are sane.
+     * DTLS-related tests.
+     * Check epoch before checking length constraint because
+     * the latter varies with the epoch. E.g., if a ChangeCipherSpec
+     * message gets duplicated before the corresponding Finished message,
+     * the second ChangeCipherSpec should be discarded because it belongs
+     * to an old epoch, but not because its length is shorter than
+     * the minimum record length for packets using the new record transform.
+     * Note that these two kinds of failures are handled differently,
+     * as an unexpected record is silently skipped but an invalid
+     * record leads to the entire datagram being dropped.
      */
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
     {
         unsigned int rec_epoch = ( ssl->in_ctr[0] << 8 ) | ssl->in_ctr[1];
 
-        /* Drop unexpected ChangeCipherSpec messages */
-        if( ssl->in_msgtype == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC &&
-            ssl->state != MBEDTLS_SSL_CLIENT_CHANGE_CIPHER_SPEC &&
-            ssl->state != MBEDTLS_SSL_SERVER_CHANGE_CIPHER_SPEC )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "dropping unexpected ChangeCipherSpec" ) );
-            return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD );
-        }
-
-        /* Drop unexpected ApplicationData records,
-         * except at the beginning of renegotiations */
-        if( ssl->in_msgtype == MBEDTLS_SSL_MSG_APPLICATION_DATA &&
-            ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER
-#if defined(MBEDTLS_SSL_RENEGOTIATION)
-            && ! ( ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_IN_PROGRESS &&
-                   ssl->state == MBEDTLS_SSL_SERVER_HELLO )
-#endif
-            )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "dropping unexpected ApplicationData" ) );
-            return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD );
-        }
-
         /* Check epoch (and sequence number) with DTLS */
         if( rec_epoch != ssl->in_epoch )
         {
@@ -3621,7 +4139,16 @@
             }
             else
 #endif /* MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE && MBEDTLS_SSL_SRV_C */
+            {
+                /* Consider buffering the record. */
+                if( rec_epoch == (unsigned int) ssl->in_epoch + 1 )
+                {
+                    MBEDTLS_SSL_DEBUG_MSG( 2, ( "Consider record for buffering" ) );
+                    return( MBEDTLS_ERR_SSL_EARLY_MESSAGE );
+                }
+
                 return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD );
+            }
         }
 
 #if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY)
@@ -3633,9 +4160,65 @@
             return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD );
         }
 #endif
+
+        /* Drop unexpected ApplicationData records,
+         * except at the beginning of renegotiations */
+        if( ssl->in_msgtype == MBEDTLS_SSL_MSG_APPLICATION_DATA &&
+            ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER
+#if defined(MBEDTLS_SSL_RENEGOTIATION)
+            && ! ( ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_IN_PROGRESS &&
+                   ssl->state == MBEDTLS_SSL_SERVER_HELLO )
+#endif
+            )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "dropping unexpected ApplicationData" ) );
+            return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD );
+        }
     }
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
+
+    /* Check length against bounds of the current transform and version */
+    if( ssl->transform_in == NULL )
+    {
+        if( ssl->in_msglen < 1 ||
+            ssl->in_msglen > MBEDTLS_SSL_IN_CONTENT_LEN )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+    }
+    else
+    {
+        if( ssl->in_msglen < ssl->transform_in->minlen )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+        if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 &&
+            ssl->in_msglen > ssl->transform_in->minlen + MBEDTLS_SSL_IN_CONTENT_LEN )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+#endif
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
+    defined(MBEDTLS_SSL_PROTO_TLS1_2)
+        /*
+         * TLS encrypted messages can have up to 256 bytes of padding
+         */
+        if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 &&
+            ssl->in_msglen > ssl->transform_in->minlen +
+                             MBEDTLS_SSL_IN_CONTENT_LEN + 256 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+#endif
+    }
+
     return( 0 );
 }
 
@@ -3676,7 +4259,7 @@
         MBEDTLS_SSL_DEBUG_BUF( 4, "input payload after decrypt",
                        ssl->in_msg, ssl->in_msglen );
 
-        if( ssl->in_msglen > MBEDTLS_SSL_MAX_CONTENT_LEN )
+        if( ssl->in_msglen > MBEDTLS_SSL_IN_CONTENT_LEN )
         {
             MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) );
             return( MBEDTLS_ERR_SSL_INVALID_RECORD );
@@ -3714,7 +4297,14 @@
  * RFC 6347 4.1.2.7) and continue reading until a valid record is found.
  *
  */
-int mbedtls_ssl_read_record( mbedtls_ssl_context *ssl )
+
+/* Helper functions for mbedtls_ssl_read_record(). */
+static int ssl_consume_current_message( mbedtls_ssl_context *ssl );
+static int ssl_get_next_record( mbedtls_ssl_context *ssl );
+static int ssl_record_is_in_progress( mbedtls_ssl_context *ssl );
+
+int mbedtls_ssl_read_record( mbedtls_ssl_context *ssl,
+                             unsigned update_hs_digest )
 {
     int ret;
 
@@ -3724,30 +4314,71 @@
     {
         do {
 
-            if( ( ret = mbedtls_ssl_read_record_layer( ssl ) ) != 0 )
-            {
-                MBEDTLS_SSL_DEBUG_RET( 1, ( "mbedtls_ssl_read_record_layer" ), ret );
+            ret = ssl_consume_current_message( ssl );
+            if( ret != 0 )
                 return( ret );
+
+            if( ssl_record_is_in_progress( ssl ) == 0 )
+            {
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+                int have_buffered = 0;
+
+                /* We only check for buffered messages if the
+                 * current datagram is fully consumed. */
+                if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+                    ssl_next_record_is_in_datagram( ssl ) == 0 )
+                {
+                    if( ssl_load_buffered_message( ssl ) == 0 )
+                        have_buffered = 1;
+                }
+
+                if( have_buffered == 0 )
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+                {
+                    ret = ssl_get_next_record( ssl );
+                    if( ret == MBEDTLS_ERR_SSL_CONTINUE_PROCESSING )
+                        continue;
+
+                    if( ret != 0 )
+                    {
+                        MBEDTLS_SSL_DEBUG_RET( 1, ( "ssl_get_next_record" ), ret );
+                        return( ret );
+                    }
+                }
             }
 
             ret = mbedtls_ssl_handle_message_type( ssl );
 
-        } while( MBEDTLS_ERR_SSL_NON_FATAL == ret );
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+            if( ret == MBEDTLS_ERR_SSL_EARLY_MESSAGE )
+            {
+                /* Buffer future message */
+                ret = ssl_buffer_message( ssl );
+                if( ret != 0 )
+                    return( ret );
+
+                ret = MBEDTLS_ERR_SSL_CONTINUE_PROCESSING;
+            }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+        } while( MBEDTLS_ERR_SSL_NON_FATAL           == ret  ||
+                 MBEDTLS_ERR_SSL_CONTINUE_PROCESSING == ret );
 
         if( 0 != ret )
         {
-            MBEDTLS_SSL_DEBUG_RET( 1, ( "mbedtls_ssl_read_record_layer" ), ret );
+            MBEDTLS_SSL_DEBUG_RET( 1, ( "mbedtls_ssl_handle_message_type" ), ret );
             return( ret );
         }
 
-        if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE )
+        if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE &&
+            update_hs_digest == 1 )
         {
             mbedtls_ssl_update_handshake_status( ssl );
         }
     }
     else
     {
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= reuse previously read message" ) );
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "reuse previously read message" ) );
         ssl->keep_current_message = 0;
     }
 
@@ -3756,13 +4387,350 @@
     return( 0 );
 }
 
-int mbedtls_ssl_read_record_layer( mbedtls_ssl_context *ssl )
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+static int ssl_next_record_is_in_datagram( mbedtls_ssl_context *ssl )
 {
-    int ret;
+    if( ssl->in_left > ssl->next_record_offset )
+        return( 1 );
 
+    return( 0 );
+}
+
+static int ssl_load_buffered_message( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    mbedtls_ssl_hs_buffer * hs_buf;
+    int ret = 0;
+
+    if( hs == NULL )
+        return( -1 );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_load_buffered_messsage" ) );
+
+    if( ssl->state == MBEDTLS_SSL_CLIENT_CHANGE_CIPHER_SPEC ||
+        ssl->state == MBEDTLS_SSL_SERVER_CHANGE_CIPHER_SPEC )
+    {
+        /* Check if we have seen a ChangeCipherSpec before.
+         * If yes, synthesize a CCS record. */
+        if( !hs->buffering.seen_ccs )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "CCS not seen in the current flight" ) );
+            ret = -1;
+            goto exit;
+        }
+
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Injecting buffered CCS message" ) );
+        ssl->in_msgtype = MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC;
+        ssl->in_msglen = 1;
+        ssl->in_msg[0] = 1;
+
+        /* As long as they are equal, the exact value doesn't matter. */
+        ssl->in_left            = 0;
+        ssl->next_record_offset = 0;
+
+        hs->buffering.seen_ccs = 0;
+        goto exit;
+    }
+
+#if defined(MBEDTLS_DEBUG_C)
+    /* Debug only */
+    {
+        unsigned offset;
+        for( offset = 1; offset < MBEDTLS_SSL_MAX_BUFFERED_HS; offset++ )
+        {
+            hs_buf = &hs->buffering.hs[offset];
+            if( hs_buf->is_valid == 1 )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "Future message with sequence number %u %s buffered.",
+                            hs->in_msg_seq + offset,
+                            hs_buf->is_complete ? "fully" : "partially" ) );
+            }
+        }
+    }
+#endif /* MBEDTLS_DEBUG_C */
+
+    /* Check if we have buffered and/or fully reassembled the
+     * next handshake message. */
+    hs_buf = &hs->buffering.hs[0];
+    if( ( hs_buf->is_valid == 1 ) && ( hs_buf->is_complete == 1 ) )
+    {
+        /* Synthesize a record containing the buffered HS message. */
+        size_t msg_len = ( hs_buf->data[1] << 16 ) |
+                         ( hs_buf->data[2] << 8  ) |
+                           hs_buf->data[3];
+
+        /* Double-check that we haven't accidentally buffered
+         * a message that doesn't fit into the input buffer. */
+        if( msg_len + 12 > MBEDTLS_SSL_IN_CONTENT_LEN )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Next handshake message has been buffered - load" ) );
+        MBEDTLS_SSL_DEBUG_BUF( 3, "Buffered handshake message (incl. header)",
+                               hs_buf->data, msg_len + 12 );
+
+        ssl->in_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;
+        ssl->in_hslen   = msg_len + 12;
+        ssl->in_msglen  = msg_len + 12;
+        memcpy( ssl->in_msg, hs_buf->data, ssl->in_hslen );
+
+        ret = 0;
+        goto exit;
+    }
+    else
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Next handshake message %u not or only partially bufffered",
+                                    hs->in_msg_seq ) );
+    }
+
+    ret = -1;
+
+exit:
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_load_buffered_message" ) );
+    return( ret );
+}
+
+static int ssl_buffer_make_space( mbedtls_ssl_context *ssl,
+                                  size_t desired )
+{
+    int offset;
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "Attempt to free buffered messages to have %u bytes available",
+                                (unsigned) desired ) );
+
+    /* Get rid of future records epoch first, if such exist. */
+    ssl_free_buffered_record( ssl );
+
+    /* Check if we have enough space available now. */
+    if( desired <= ( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
+                     hs->buffering.total_bytes_buffered ) )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Enough space available after freeing future epoch record" ) );
+        return( 0 );
+    }
+
+    /* We don't have enough space to buffer the next expected handshake
+     * message. Remove buffers used for future messages to gain space,
+     * starting with the most distant one. */
+    for( offset = MBEDTLS_SSL_MAX_BUFFERED_HS - 1;
+         offset >= 0; offset-- )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Free buffering slot %d to make space for reassembly of next handshake message",
+                                    offset ) );
+
+        ssl_buffering_free_slot( ssl, (uint8_t) offset );
+
+        /* Check if we have enough space available now. */
+        if( desired <= ( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
+                         hs->buffering.total_bytes_buffered ) )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "Enough space available after freeing buffered HS messages" ) );
+            return( 0 );
+        }
+    }
+
+    return( -1 );
+}
+
+static int ssl_buffer_message( mbedtls_ssl_context *ssl )
+{
+    int ret = 0;
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+
+    if( hs == NULL )
+        return( 0 );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_buffer_message" ) );
+
+    switch( ssl->in_msgtype )
+    {
+        case MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC:
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "Remember CCS message" ) );
+
+            hs->buffering.seen_ccs = 1;
+            break;
+
+        case MBEDTLS_SSL_MSG_HANDSHAKE:
+        {
+            unsigned recv_msg_seq_offset;
+            unsigned recv_msg_seq = ( ssl->in_msg[4] << 8 ) | ssl->in_msg[5];
+            mbedtls_ssl_hs_buffer *hs_buf;
+            size_t msg_len = ssl->in_hslen - 12;
+
+            /* We should never receive an old handshake
+             * message - double-check nonetheless. */
+            if( recv_msg_seq < ssl->handshake->in_msg_seq )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+                return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+            }
+
+            recv_msg_seq_offset = recv_msg_seq - ssl->handshake->in_msg_seq;
+            if( recv_msg_seq_offset >= MBEDTLS_SSL_MAX_BUFFERED_HS )
+            {
+                /* Silently ignore -- message too far in the future */
+                MBEDTLS_SSL_DEBUG_MSG( 2,
+                 ( "Ignore future HS message with sequence number %u, "
+                   "buffering window %u - %u",
+                   recv_msg_seq, ssl->handshake->in_msg_seq,
+                   ssl->handshake->in_msg_seq + MBEDTLS_SSL_MAX_BUFFERED_HS - 1 ) );
+
+                goto exit;
+            }
+
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering HS message with sequence number %u, offset %u ",
+                                        recv_msg_seq, recv_msg_seq_offset ) );
+
+            hs_buf = &hs->buffering.hs[ recv_msg_seq_offset ];
+
+            /* Check if the buffering for this seq nr has already commenced. */
+            if( !hs_buf->is_valid )
+            {
+                size_t reassembly_buf_sz;
+
+                hs_buf->is_fragmented =
+                    ( ssl_hs_is_proper_fragment( ssl ) == 1 );
+
+                /* We copy the message back into the input buffer
+                 * after reassembly, so check that it's not too large.
+                 * This is an implementation-specific limitation
+                 * and not one from the standard, hence it is not
+                 * checked in ssl_check_hs_header(). */
+                if( msg_len + 12 > MBEDTLS_SSL_IN_CONTENT_LEN )
+                {
+                    /* Ignore message */
+                    goto exit;
+                }
+
+                /* Check if we have enough space to buffer the message. */
+                if( hs->buffering.total_bytes_buffered >
+                    MBEDTLS_SSL_DTLS_MAX_BUFFERING )
+                {
+                    MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+                    return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+                }
+
+                reassembly_buf_sz = ssl_get_reassembly_buffer_size( msg_len,
+                                                       hs_buf->is_fragmented );
+
+                if( reassembly_buf_sz > ( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
+                                          hs->buffering.total_bytes_buffered ) )
+                {
+                    if( recv_msg_seq_offset > 0 )
+                    {
+                        /* If we can't buffer a future message because
+                         * of space limitations -- ignore. */
+                        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering of future message of size %u would exceed the compile-time limit %u (already %u bytes buffered) -- ignore\n",
+                             (unsigned) msg_len, MBEDTLS_SSL_DTLS_MAX_BUFFERING,
+                             (unsigned) hs->buffering.total_bytes_buffered ) );
+                        goto exit;
+                    }
+                    else
+                    {
+                        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering of future message of size %u would exceed the compile-time limit %u (already %u bytes buffered) -- attempt to make space by freeing buffered future messages\n",
+                             (unsigned) msg_len, MBEDTLS_SSL_DTLS_MAX_BUFFERING,
+                             (unsigned) hs->buffering.total_bytes_buffered ) );
+                    }
+
+                    if( ssl_buffer_make_space( ssl, reassembly_buf_sz ) != 0 )
+                    {
+                        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Reassembly of next message of size %u (%u with bitmap) would exceed the compile-time limit %u (already %u bytes buffered) -- fail\n",
+                             (unsigned) msg_len,
+                             (unsigned) reassembly_buf_sz,
+                             MBEDTLS_SSL_DTLS_MAX_BUFFERING,
+                             (unsigned) hs->buffering.total_bytes_buffered ) );
+                        ret = MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL;
+                        goto exit;
+                    }
+                }
+
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialize reassembly, total length = %d",
+                                            msg_len ) );
+
+                hs_buf->data = mbedtls_calloc( 1, reassembly_buf_sz );
+                if( hs_buf->data == NULL )
+                {
+                    ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
+                    goto exit;
+                }
+                hs_buf->data_len = reassembly_buf_sz;
+
+                /* Prepare final header: copy msg_type, length and message_seq,
+                 * then add standardised fragment_offset and fragment_length */
+                memcpy( hs_buf->data, ssl->in_msg, 6 );
+                memset( hs_buf->data + 6, 0, 3 );
+                memcpy( hs_buf->data + 9, hs_buf->data + 1, 3 );
+
+                hs_buf->is_valid = 1;
+
+                hs->buffering.total_bytes_buffered += reassembly_buf_sz;
+            }
+            else
+            {
+                /* Make sure msg_type and length are consistent */
+                if( memcmp( hs_buf->data, ssl->in_msg, 4 ) != 0 )
+                {
+                    MBEDTLS_SSL_DEBUG_MSG( 1, ( "Fragment header mismatch - ignore" ) );
+                    /* Ignore */
+                    goto exit;
+                }
+            }
+
+            if( !hs_buf->is_complete )
+            {
+                size_t frag_len, frag_off;
+                unsigned char * const msg = hs_buf->data + 12;
+
+                /*
+                 * Check and copy current fragment
+                 */
+
+                /* Validation of header fields already done in
+                 * mbedtls_ssl_prepare_handshake_record(). */
+                frag_off = ssl_get_hs_frag_off( ssl );
+                frag_len = ssl_get_hs_frag_len( ssl );
+
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "adding fragment, offset = %d, length = %d",
+                                            frag_off, frag_len ) );
+                memcpy( msg + frag_off, ssl->in_msg + 12, frag_len );
+
+                if( hs_buf->is_fragmented )
+                {
+                    unsigned char * const bitmask = msg + msg_len;
+                    ssl_bitmask_set( bitmask, frag_off, frag_len );
+                    hs_buf->is_complete = ( ssl_bitmask_check( bitmask,
+                                                               msg_len ) == 0 );
+                }
+                else
+                {
+                    hs_buf->is_complete = 1;
+                }
+
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "message %scomplete",
+                                   hs_buf->is_complete ? "" : "not yet " ) );
+            }
+
+            break;
+        }
+
+        default:
+            /* We don't buffer other types of messages. */
+            break;
+    }
+
+exit:
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_buffer_message" ) );
+    return( ret );
+}
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+static int ssl_consume_current_message( mbedtls_ssl_context *ssl )
+{
     /*
-     * Step A
-     *
      * Consume last content-layer message and potentially
      * update in_msglen which keeps track of the contents'
      * consumption state.
@@ -3774,11 +4742,6 @@
      * (2) Alert messages:
      *     Consume whole record content, in_msglen = 0.
      *
-     *     NOTE: This needs to be fixed, since like for
-     *     handshake messages it is allowed to have
-     *     multiple alerts witin a single record.
-     *     Internal reference IOTSSL-1321.
-     *
      * (3) Change cipher spec:
      *     Consume whole record content, in_msglen = 0.
      *
@@ -3806,12 +4769,12 @@
          */
 
         /* Notes:
-         * (1) in_hslen is *NOT* necessarily the size of the
+         * (1) in_hslen is not necessarily the size of the
          *     current handshake content: If DTLS handshake
          *     fragmentation is used, that's the fragment
          *     size instead. Using the total handshake message
-         *     size here is FAULTY and should be changed at
-         *     some point. Internal reference IOTSSL-1414.
+         *     size here is faulty and should be changed at
+         *     some point.
          * (2) While it doesn't seem to cause problems, one
          *     has to be very careful not to assume that in_hslen
          *     is always <= in_msglen in a sensible communication.
@@ -3849,26 +4812,161 @@
         ssl->in_msglen = 0;
     }
 
-    /*
-     * Step B
-     *
-     * Fetch and decode new record if current one is fully consumed.
-     *
-     */
+    return( 0 );
+}
 
+static int ssl_record_is_in_progress( mbedtls_ssl_context *ssl )
+{
     if( ssl->in_msglen > 0 )
+        return( 1 );
+
+    return( 0 );
+}
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+
+static void ssl_free_buffered_record( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    if( hs == NULL )
+        return;
+
+    if( hs->buffering.future_record.data != NULL )
     {
-        /* There's something left to be processed in the current record. */
+        hs->buffering.total_bytes_buffered -=
+            hs->buffering.future_record.len;
+
+        mbedtls_free( hs->buffering.future_record.data );
+        hs->buffering.future_record.data = NULL;
+    }
+}
+
+static int ssl_load_buffered_record( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    unsigned char * rec;
+    size_t rec_len;
+    unsigned rec_epoch;
+
+    if( ssl->conf->transport != MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+        return( 0 );
+
+    if( hs == NULL )
+        return( 0 );
+
+    rec       = hs->buffering.future_record.data;
+    rec_len   = hs->buffering.future_record.len;
+    rec_epoch = hs->buffering.future_record.epoch;
+
+    if( rec == NULL )
+        return( 0 );
+
+    /* Only consider loading future records if the
+     * input buffer is empty. */
+    if( ssl_next_record_is_in_datagram( ssl ) == 1 )
+        return( 0 );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_load_buffered_record" ) );
+
+    if( rec_epoch != ssl->in_epoch )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffered record not from current epoch." ) );
+        goto exit;
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "Found buffered record from current epoch - load" ) );
+
+    /* Double-check that the record is not too large */
+    if( rec_len > MBEDTLS_SSL_IN_BUFFER_LEN -
+        (size_t)( ssl->in_hdr - ssl->in_buf ) )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    memcpy( ssl->in_hdr, rec, rec_len );
+    ssl->in_left = rec_len;
+    ssl->next_record_offset = 0;
+
+    ssl_free_buffered_record( ssl );
+
+exit:
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_load_buffered_record" ) );
+    return( 0 );
+}
+
+static int ssl_buffer_future_record( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    size_t const rec_hdr_len = 13;
+    size_t const total_buf_sz = rec_hdr_len + ssl->in_msglen;
+
+    /* Don't buffer future records outside handshakes. */
+    if( hs == NULL )
+        return( 0 );
+
+    /* Only buffer handshake records (we are only interested
+     * in Finished messages). */
+    if( ssl->in_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE )
+        return( 0 );
+
+    /* Don't buffer more than one future epoch record. */
+    if( hs->buffering.future_record.data != NULL )
+        return( 0 );
+
+    /* Don't buffer record if there's not enough buffering space remaining. */
+    if( total_buf_sz > ( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
+                         hs->buffering.total_bytes_buffered ) )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering of future epoch record of size %u would exceed the compile-time limit %u (already %u bytes buffered) -- ignore\n",
+                        (unsigned) total_buf_sz, MBEDTLS_SSL_DTLS_MAX_BUFFERING,
+                        (unsigned) hs->buffering.total_bytes_buffered ) );
         return( 0 );
     }
 
-    /* Need to fetch a new record */
+    /* Buffer record */
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffer record from epoch %u",
+                                ssl->in_epoch + 1 ) );
+    MBEDTLS_SSL_DEBUG_BUF( 3, "Buffered record", ssl->in_hdr,
+                           rec_hdr_len + ssl->in_msglen );
+
+    /* ssl_parse_record_header() only considers records
+     * of the next epoch as candidates for buffering. */
+    hs->buffering.future_record.epoch = ssl->in_epoch + 1;
+    hs->buffering.future_record.len   = total_buf_sz;
+
+    hs->buffering.future_record.data =
+        mbedtls_calloc( 1, hs->buffering.future_record.len );
+    if( hs->buffering.future_record.data == NULL )
+    {
+        /* If we run out of RAM trying to buffer a
+         * record from the next epoch, just ignore. */
+        return( 0 );
+    }
+
+    memcpy( hs->buffering.future_record.data, ssl->in_hdr, total_buf_sz );
+
+    hs->buffering.total_bytes_buffered += total_buf_sz;
+    return( 0 );
+}
+
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+static int ssl_get_next_record( mbedtls_ssl_context *ssl )
+{
+    int ret;
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
-read_record_header:
-#endif
-
-    /* Current record either fully processed or to be discarded. */
+    /* We might have buffered a future record; if so,
+     * and if the epoch matches now, load it.
+     * On success, this call will set ssl->in_left to
+     * the length of the buffered record, so that
+     * the calls to ssl_fetch_input() below will
+     * essentially be no-ops. */
+    ret = ssl_load_buffered_record( ssl );
+    if( ret != 0 )
+        return( ret );
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     if( ( ret = mbedtls_ssl_fetch_input( ssl, mbedtls_ssl_hdr_len( ssl ) ) ) != 0 )
     {
@@ -3882,6 +4980,16 @@
         if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
             ret != MBEDTLS_ERR_SSL_CLIENT_RECONNECT )
         {
+            if( ret == MBEDTLS_ERR_SSL_EARLY_MESSAGE )
+            {
+                ret = ssl_buffer_future_record( ssl );
+                if( ret != 0 )
+                    return( ret );
+
+                /* Fall through to handling of unexpected records */
+                ret = MBEDTLS_ERR_SSL_UNEXPECTED_RECORD;
+            }
+
             if( ret == MBEDTLS_ERR_SSL_UNEXPECTED_RECORD )
             {
                 /* Skip unexpected record (but not whole datagram) */
@@ -3902,7 +5010,7 @@
             }
 
             /* Get next record */
-            goto read_record_header;
+            return( MBEDTLS_ERR_SSL_CONTINUE_PROCESSING );
         }
 #endif
         return( ret );
@@ -3921,7 +5029,13 @@
     /* Done reading this record, get ready for the next one */
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    {
         ssl->next_record_offset = ssl->in_msglen + mbedtls_ssl_hdr_len( ssl );
+        if( ssl->next_record_offset < ssl->in_left )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 3, ( "more than one record within datagram" ) );
+        }
+    }
     else
 #endif
         ssl->in_left = 0;
@@ -3968,7 +5082,7 @@
                 ssl->in_left = 0;
 
                 MBEDTLS_SSL_DEBUG_MSG( 1, ( "discarding invalid record (mac)" ) );
-                goto read_record_header;
+                return( MBEDTLS_ERR_SSL_CONTINUE_PROCESSING );
             }
 
             return( ret );
@@ -3989,46 +5103,6 @@
         }
     }
 
-    /*
-     * When we sent the last flight of the handshake, we MUST respond to a
-     * retransmit of the peer's previous flight with a retransmit. (In
-     * practice, only the Finished message will make it, other messages
-     * including CCS use the old transform so they're dropped as invalid.)
-     *
-     * If the record we received is not a handshake message, however, it
-     * means the peer received our last flight so we can clean up
-     * handshake info.
-     *
-     * This check needs to be done before prepare_handshake() due to an edge
-     * case: if the client immediately requests renegotiation, this
-     * finishes the current handshake first, avoiding the new ClientHello
-     * being mistaken for an ancient message in the current handshake.
-     */
-#if defined(MBEDTLS_SSL_PROTO_DTLS)
-    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
-        ssl->handshake != NULL &&
-        ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER )
-    {
-        if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE &&
-                ssl->in_msg[0] == MBEDTLS_SSL_HS_FINISHED )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 2, ( "received retransmit of last flight" ) );
-
-            if( ( ret = mbedtls_ssl_resend( ssl ) ) != 0 )
-            {
-                MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_resend", ret );
-                return( ret );
-            }
-
-            return( MBEDTLS_ERR_SSL_WANT_READ );
-        }
-        else
-        {
-            ssl_handshake_wrapup_free_hs_transform( ssl );
-        }
-    }
-#endif
-
     return( 0 );
 }
 
@@ -4047,8 +5121,51 @@
         }
     }
 
+    if( ssl->in_msgtype == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC )
+    {
+        if( ssl->in_msglen != 1 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid CCS message, len: %d",
+                           ssl->in_msglen ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
+        if( ssl->in_msg[0] != 1 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid CCS message, content: %02x",
+                                        ssl->in_msg[0] ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+        if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+            ssl->state != MBEDTLS_SSL_CLIENT_CHANGE_CIPHER_SPEC    &&
+            ssl->state != MBEDTLS_SSL_SERVER_CHANGE_CIPHER_SPEC )
+        {
+            if( ssl->handshake == NULL )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "dropping ChangeCipherSpec outside handshake" ) );
+                return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD );
+            }
+
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "received out-of-order ChangeCipherSpec - remember" ) );
+            return( MBEDTLS_ERR_SSL_EARLY_MESSAGE );
+        }
+#endif
+    }
+
     if( ssl->in_msgtype == MBEDTLS_SSL_MSG_ALERT )
     {
+        if( ssl->in_msglen != 2 )
+        {
+            /* Note: Standard allows for more than one 2 byte alert
+               to be packed in a single message, but Mbed TLS doesn't
+               currently support this. */
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid alert message, len: %d",
+                           ssl->in_msglen ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
         MBEDTLS_SSL_DEBUG_MSG( 2, ( "got an alert message, type: [%d:%d]",
                        ssl->in_msg[0], ssl->in_msg[1] ) );
 
@@ -4073,7 +5190,7 @@
         if( ssl->in_msg[0] == MBEDTLS_SSL_ALERT_LEVEL_WARNING &&
             ssl->in_msg[1] == MBEDTLS_SSL_ALERT_MSG_NO_RENEGOTIATION )
         {
-            MBEDTLS_SSL_DEBUG_MSG( 2, ( "is a SSLv3 no_cert" ) );
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "is a SSLv3 no renegotiation alert" ) );
             /* Will be handled when trying to parse ServerHello */
             return( 0 );
         }
@@ -4095,6 +5212,15 @@
         return MBEDTLS_ERR_SSL_NON_FATAL;
     }
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+        ssl->handshake != NULL &&
+        ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER  )
+    {
+        ssl_handshake_wrapup_free_hs_transform( ssl );
+    }
+#endif
+
     return( 0 );
 }
 
@@ -4129,7 +5255,7 @@
     ssl->out_msg[0] = level;
     ssl->out_msg[1] = message;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_record( ssl, SSL_FORCE_FLUSH ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
         return( ret );
@@ -4269,10 +5395,10 @@
     while( crt != NULL )
     {
         n = crt->raw.len;
-        if( n > MBEDTLS_SSL_MAX_CONTENT_LEN - 3 - i )
+        if( n > MBEDTLS_SSL_OUT_CONTENT_LEN - 3 - i )
         {
             MBEDTLS_SSL_DEBUG_MSG( 1, ( "certificate too large, %d > %d",
-                           i + 3 + n, MBEDTLS_SSL_MAX_CONTENT_LEN ) );
+                           i + 3 + n, MBEDTLS_SSL_OUT_CONTENT_LEN ) );
             return( MBEDTLS_ERR_SSL_CERTIFICATE_TOO_LARGE );
         }
 
@@ -4298,9 +5424,9 @@
 
     ssl->state++;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -4309,60 +5435,16 @@
     return( ret );
 }
 
-int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
+/*
+ * Once the certificate message is read, parse it into a cert chain and
+ * perform basic checks, but leave actual verification to the caller
+ */
+static int ssl_parse_certificate_chain( mbedtls_ssl_context *ssl )
 {
-    int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
+    int ret;
     size_t i, n;
-    const mbedtls_ssl_ciphersuite_t *ciphersuite_info = ssl->transform_negotiate->ciphersuite_info;
-    int authmode = ssl->conf->authmode;
     uint8_t alert;
 
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse certificate" ) );
-
-    if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_PSK ||
-        ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_PSK ||
-        ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK ||
-        ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECJPAKE )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
-        ssl->state++;
-        return( 0 );
-    }
-
-#if defined(MBEDTLS_SSL_SRV_C)
-    if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER &&
-        ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_RSA_PSK )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
-        ssl->state++;
-        return( 0 );
-    }
-
-#if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
-    if( ssl->handshake->sni_authmode != MBEDTLS_SSL_VERIFY_UNSET )
-        authmode = ssl->handshake->sni_authmode;
-#endif
-
-    if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER &&
-        authmode == MBEDTLS_SSL_VERIFY_NONE )
-    {
-        ssl->session_negotiate->verify_result = MBEDTLS_X509_BADCERT_SKIP_VERIFY;
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
-        ssl->state++;
-        return( 0 );
-    }
-#endif
-
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
-    {
-        /* mbedtls_ssl_read_record may have sent an alert already. We
-           let it decide whether to alert. */
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
-        return( ret );
-    }
-
-    ssl->state++;
-
 #if defined(MBEDTLS_SSL_SRV_C)
 #if defined(MBEDTLS_SSL_PROTO_SSL3)
     /*
@@ -4382,10 +5464,7 @@
                one. The client should know what's going on, so we
                don't send an alert. */
             ssl->session_negotiate->verify_result = MBEDTLS_X509_BADCERT_MISSING;
-            if( authmode == MBEDTLS_SSL_VERIFY_OPTIONAL )
-                return( 0 );
-            else
-                return( MBEDTLS_ERR_SSL_NO_CLIENT_CERTIFICATE );
+            return( MBEDTLS_ERR_SSL_NO_CLIENT_CERTIFICATE );
         }
     }
 #endif /* MBEDTLS_SSL_PROTO_SSL3 */
@@ -4406,10 +5485,7 @@
                one. The client should know what's going on, so we
                don't send an alert. */
             ssl->session_negotiate->verify_result = MBEDTLS_X509_BADCERT_MISSING;
-            if( authmode == MBEDTLS_SSL_VERIFY_OPTIONAL )
-                return( 0 );
-            else
-                return( MBEDTLS_ERR_SSL_NO_CLIENT_CERTIFICATE );
+            return( MBEDTLS_ERR_SSL_NO_CLIENT_CERTIFICATE );
         }
     }
 #endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 || \
@@ -4472,6 +5548,12 @@
 
     while( i < ssl->in_hslen )
     {
+        if ( i + 3 > ssl->in_hslen ) {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate message" ) );
+            mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+                                           MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
+            return( MBEDTLS_ERR_SSL_BAD_HS_CERTIFICATE );
+        }
         if( ssl->in_msg[i] != 0 )
         {
             MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate message" ) );
@@ -4553,6 +5635,94 @@
     }
 #endif /* MBEDTLS_SSL_RENEGOTIATION && MBEDTLS_SSL_CLI_C */
 
+    return( 0 );
+}
+
+int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl )
+{
+    int ret;
+    const mbedtls_ssl_ciphersuite_t * const ciphersuite_info =
+          ssl->transform_negotiate->ciphersuite_info;
+#if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
+    const int authmode = ssl->handshake->sni_authmode != MBEDTLS_SSL_VERIFY_UNSET
+                       ? ssl->handshake->sni_authmode
+                       : ssl->conf->authmode;
+#else
+    const int authmode = ssl->conf->authmode;
+#endif
+    void *rs_ctx = NULL;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse certificate" ) );
+
+    if( ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_PSK ||
+        ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_DHE_PSK ||
+        ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK ||
+        ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_ECJPAKE )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
+        ssl->state++;
+        return( 0 );
+    }
+
+#if defined(MBEDTLS_SSL_SRV_C)
+    if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER &&
+        ciphersuite_info->key_exchange == MBEDTLS_KEY_EXCHANGE_RSA_PSK )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
+        ssl->state++;
+        return( 0 );
+    }
+
+    if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER &&
+        authmode == MBEDTLS_SSL_VERIFY_NONE )
+    {
+        ssl->session_negotiate->verify_result = MBEDTLS_X509_BADCERT_SKIP_VERIFY;
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate" ) );
+
+        ssl->state++;
+        return( 0 );
+    }
+#endif
+
+#if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
+    if( ssl->handshake->ecrs_enabled &&
+        ssl->handshake->ecrs_state == ssl_ecrs_crt_verify )
+    {
+        goto crt_verify;
+    }
+#endif
+
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
+    {
+        /* mbedtls_ssl_read_record may have sent an alert already. We
+           let it decide whether to alert. */
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
+        return( ret );
+    }
+
+    if( ( ret = ssl_parse_certificate_chain( ssl ) ) != 0 )
+    {
+#if defined(MBEDTLS_SSL_SRV_C)
+        if( ret == MBEDTLS_ERR_SSL_NO_CLIENT_CERTIFICATE &&
+            authmode == MBEDTLS_SSL_VERIFY_OPTIONAL )
+        {
+            ret = 0;
+        }
+#endif
+
+        ssl->state++;
+        return( ret );
+    }
+
+#if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
+    if( ssl->handshake->ecrs_enabled)
+        ssl->handshake->ecrs_state = ssl_ecrs_crt_verify;
+
+crt_verify:
+    if( ssl->handshake->ecrs_enabled)
+        rs_ctx = &ssl->handshake->ecrs_ctx;
+#endif
+
     if( authmode != MBEDTLS_SSL_VERIFY_NONE )
     {
         mbedtls_x509_crt *ca_chain;
@@ -4574,19 +5744,24 @@
         /*
          * Main check: verify certificate
          */
-        ret = mbedtls_x509_crt_verify_with_profile(
+        ret = mbedtls_x509_crt_verify_restartable(
                                 ssl->session_negotiate->peer_cert,
                                 ca_chain, ca_crl,
                                 ssl->conf->cert_profile,
                                 ssl->hostname,
                                &ssl->session_negotiate->verify_result,
-                                ssl->conf->f_vrfy, ssl->conf->p_vrfy );
+                                ssl->conf->f_vrfy, ssl->conf->p_vrfy, rs_ctx );
 
         if( ret != 0 )
         {
             MBEDTLS_SSL_DEBUG_RET( 1, "x509_verify_cert", ret );
         }
 
+#if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
+        if( ret == MBEDTLS_ERR_ECP_IN_PROGRESS )
+            return( MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS );
+#endif
+
         /*
          * Secondary checks: always done, but change 'ret' only if it was 0
          */
@@ -4639,6 +5814,8 @@
 
         if( ret != 0 )
         {
+            uint8_t alert;
+
             /* The certificate may have been rejected for several reasons.
                Pick one and send the corresponding alert. Which alert to send
                may be a subject of debate in some cases. */
@@ -4681,6 +5858,8 @@
 #endif /* MBEDTLS_DEBUG_C */
     }
 
+    ssl->state++;
+
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse certificate" ) );
 
     return( ret );
@@ -4705,9 +5884,9 @@
 
     ssl->state++;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -4722,7 +5901,7 @@
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse change cipher spec" ) );
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
         return( ret );
@@ -4736,13 +5915,8 @@
         return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
     }
 
-    if( ssl->in_msglen != 1 || ssl->in_msg[0] != 1 )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad change cipher spec message" ) );
-        mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
-                                        MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
-        return( MBEDTLS_ERR_SSL_BAD_HS_CHANGE_CIPHER_SPEC );
-    }
+    /* CCS records are only accepted if they have length 1 and content '1',
+     * so we don't need to check this here. */
 
     /*
      * Switch to our negotiated transform and session parameters for inbound
@@ -4772,16 +5946,7 @@
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
     memset( ssl->in_ctr, 0, 8 );
 
-    /*
-     * Set the in_msg pointer to the correct location based on IV length
-     */
-    if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
-    {
-        ssl->in_msg = ssl->in_iv + ssl->transform_negotiate->ivlen -
-                      ssl->transform_negotiate->fixed_ivlen;
-    }
-    else
-        ssl->in_msg = ssl->in_iv;
+    ssl_update_in_pointers( ssl, ssl->transform_negotiate );
 
 #if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
     if( mbedtls_ssl_hw_record_activate != NULL )
@@ -4836,15 +6001,15 @@
 {
 #if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) || \
     defined(MBEDTLS_SSL_PROTO_TLS1_1)
-     mbedtls_md5_starts( &ssl->handshake->fin_md5  );
-    mbedtls_sha1_starts( &ssl->handshake->fin_sha1 );
+     mbedtls_md5_starts_ret( &ssl->handshake->fin_md5  );
+    mbedtls_sha1_starts_ret( &ssl->handshake->fin_sha1 );
 #endif
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2)
 #if defined(MBEDTLS_SHA256_C)
-    mbedtls_sha256_starts( &ssl->handshake->fin_sha256, 0 );
+    mbedtls_sha256_starts_ret( &ssl->handshake->fin_sha256, 0 );
 #endif
 #if defined(MBEDTLS_SHA512_C)
-    mbedtls_sha512_starts( &ssl->handshake->fin_sha512, 1 );
+    mbedtls_sha512_starts_ret( &ssl->handshake->fin_sha512, 1 );
 #endif
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
 }
@@ -4854,15 +6019,15 @@
 {
 #if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) || \
     defined(MBEDTLS_SSL_PROTO_TLS1_1)
-     mbedtls_md5_update( &ssl->handshake->fin_md5 , buf, len );
-    mbedtls_sha1_update( &ssl->handshake->fin_sha1, buf, len );
+     mbedtls_md5_update_ret( &ssl->handshake->fin_md5 , buf, len );
+    mbedtls_sha1_update_ret( &ssl->handshake->fin_sha1, buf, len );
 #endif
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2)
 #if defined(MBEDTLS_SHA256_C)
-    mbedtls_sha256_update( &ssl->handshake->fin_sha256, buf, len );
+    mbedtls_sha256_update_ret( &ssl->handshake->fin_sha256, buf, len );
 #endif
 #if defined(MBEDTLS_SHA512_C)
-    mbedtls_sha512_update( &ssl->handshake->fin_sha512, buf, len );
+    mbedtls_sha512_update_ret( &ssl->handshake->fin_sha512, buf, len );
 #endif
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
 }
@@ -4872,8 +6037,8 @@
 static void ssl_update_checksum_md5sha1( mbedtls_ssl_context *ssl,
                                          const unsigned char *buf, size_t len )
 {
-     mbedtls_md5_update( &ssl->handshake->fin_md5 , buf, len );
-    mbedtls_sha1_update( &ssl->handshake->fin_sha1, buf, len );
+     mbedtls_md5_update_ret( &ssl->handshake->fin_md5 , buf, len );
+    mbedtls_sha1_update_ret( &ssl->handshake->fin_sha1, buf, len );
 }
 #endif
 
@@ -4882,7 +6047,7 @@
 static void ssl_update_checksum_sha256( mbedtls_ssl_context *ssl,
                                         const unsigned char *buf, size_t len )
 {
-    mbedtls_sha256_update( &ssl->handshake->fin_sha256, buf, len );
+    mbedtls_sha256_update_ret( &ssl->handshake->fin_sha256, buf, len );
 }
 #endif
 
@@ -4890,7 +6055,7 @@
 static void ssl_update_checksum_sha384( mbedtls_ssl_context *ssl,
                                         const unsigned char *buf, size_t len )
 {
-    mbedtls_sha512_update( &ssl->handshake->fin_sha512, buf, len );
+    mbedtls_sha512_update_ret( &ssl->handshake->fin_sha512, buf, len );
 }
 #endif
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
@@ -4943,38 +6108,38 @@
 
     memset( padbuf, 0x36, 48 );
 
-    mbedtls_md5_update( &md5, (const unsigned char *) sender, 4 );
-    mbedtls_md5_update( &md5, session->master, 48 );
-    mbedtls_md5_update( &md5, padbuf, 48 );
-    mbedtls_md5_finish( &md5, md5sum );
+    mbedtls_md5_update_ret( &md5, (const unsigned char *) sender, 4 );
+    mbedtls_md5_update_ret( &md5, session->master, 48 );
+    mbedtls_md5_update_ret( &md5, padbuf, 48 );
+    mbedtls_md5_finish_ret( &md5, md5sum );
 
-    mbedtls_sha1_update( &sha1, (const unsigned char *) sender, 4 );
-    mbedtls_sha1_update( &sha1, session->master, 48 );
-    mbedtls_sha1_update( &sha1, padbuf, 40 );
-    mbedtls_sha1_finish( &sha1, sha1sum );
+    mbedtls_sha1_update_ret( &sha1, (const unsigned char *) sender, 4 );
+    mbedtls_sha1_update_ret( &sha1, session->master, 48 );
+    mbedtls_sha1_update_ret( &sha1, padbuf, 40 );
+    mbedtls_sha1_finish_ret( &sha1, sha1sum );
 
     memset( padbuf, 0x5C, 48 );
 
-    mbedtls_md5_starts( &md5 );
-    mbedtls_md5_update( &md5, session->master, 48 );
-    mbedtls_md5_update( &md5, padbuf, 48 );
-    mbedtls_md5_update( &md5, md5sum, 16 );
-    mbedtls_md5_finish( &md5, buf );
+    mbedtls_md5_starts_ret( &md5 );
+    mbedtls_md5_update_ret( &md5, session->master, 48 );
+    mbedtls_md5_update_ret( &md5, padbuf, 48 );
+    mbedtls_md5_update_ret( &md5, md5sum, 16 );
+    mbedtls_md5_finish_ret( &md5, buf );
 
-    mbedtls_sha1_starts( &sha1 );
-    mbedtls_sha1_update( &sha1, session->master, 48 );
-    mbedtls_sha1_update( &sha1, padbuf , 40 );
-    mbedtls_sha1_update( &sha1, sha1sum, 20 );
-    mbedtls_sha1_finish( &sha1, buf + 16 );
+    mbedtls_sha1_starts_ret( &sha1 );
+    mbedtls_sha1_update_ret( &sha1, session->master, 48 );
+    mbedtls_sha1_update_ret( &sha1, padbuf , 40 );
+    mbedtls_sha1_update_ret( &sha1, sha1sum, 20 );
+    mbedtls_sha1_finish_ret( &sha1, buf + 16 );
 
     MBEDTLS_SSL_DEBUG_BUF( 3, "calc finished result", buf, 36 );
 
     mbedtls_md5_free(  &md5  );
     mbedtls_sha1_free( &sha1 );
 
-    mbedtls_zeroize(  padbuf, sizeof(  padbuf ) );
-    mbedtls_zeroize(  md5sum, sizeof(  md5sum ) );
-    mbedtls_zeroize( sha1sum, sizeof( sha1sum ) );
+    mbedtls_platform_zeroize(  padbuf, sizeof(  padbuf ) );
+    mbedtls_platform_zeroize(  md5sum, sizeof(  md5sum ) );
+    mbedtls_platform_zeroize( sha1sum, sizeof( sha1sum ) );
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc  finished" ) );
 }
@@ -5022,8 +6187,8 @@
              ? "client finished"
              : "server finished";
 
-    mbedtls_md5_finish(  &md5, padbuf );
-    mbedtls_sha1_finish( &sha1, padbuf + 16 );
+    mbedtls_md5_finish_ret(  &md5, padbuf );
+    mbedtls_sha1_finish_ret( &sha1, padbuf + 16 );
 
     ssl->handshake->tls_prf( session->master, 48, sender,
                              padbuf, 36, buf, len );
@@ -5033,7 +6198,7 @@
     mbedtls_md5_free(  &md5  );
     mbedtls_sha1_free( &sha1 );
 
-    mbedtls_zeroize(  padbuf, sizeof(  padbuf ) );
+    mbedtls_platform_zeroize(  padbuf, sizeof(  padbuf ) );
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc  finished" ) );
 }
@@ -5074,7 +6239,7 @@
              ? "client finished"
              : "server finished";
 
-    mbedtls_sha256_finish( &sha256, padbuf );
+    mbedtls_sha256_finish_ret( &sha256, padbuf );
 
     ssl->handshake->tls_prf( session->master, 48, sender,
                              padbuf, 32, buf, len );
@@ -5083,7 +6248,7 @@
 
     mbedtls_sha256_free( &sha256 );
 
-    mbedtls_zeroize(  padbuf, sizeof(  padbuf ) );
+    mbedtls_platform_zeroize(  padbuf, sizeof(  padbuf ) );
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc  finished" ) );
 }
@@ -5123,7 +6288,7 @@
              ? "client finished"
              : "server finished";
 
-    mbedtls_sha512_finish( &sha512, padbuf );
+    mbedtls_sha512_finish_ret( &sha512, padbuf );
 
     ssl->handshake->tls_prf( session->master, 48, sender,
                              padbuf, 48, buf, len );
@@ -5132,7 +6297,7 @@
 
     mbedtls_sha512_free( &sha512 );
 
-    mbedtls_zeroize(  padbuf, sizeof( padbuf ) );
+    mbedtls_platform_zeroize(  padbuf, sizeof( padbuf ) );
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc  finished" ) );
 }
@@ -5146,7 +6311,7 @@
     /*
      * Free our handshake params
      */
-    mbedtls_ssl_handshake_free( ssl->handshake );
+    mbedtls_ssl_handshake_free( ssl );
     mbedtls_free( ssl->handshake );
     ssl->handshake = NULL;
 
@@ -5232,16 +6397,7 @@
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write finished" ) );
 
-    /*
-     * Set the out_msg pointer to the correct location based on IV length
-     */
-    if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
-    {
-        ssl->out_msg = ssl->out_iv + ssl->transform_negotiate->ivlen -
-                       ssl->transform_negotiate->fixed_ivlen;
-    }
-    else
-        ssl->out_msg = ssl->out_iv;
+    ssl_update_out_pointers( ssl, ssl->transform_negotiate );
 
     ssl->handshake->calc_finished( ssl, ssl->out_msg + 4, ssl->conf->endpoint );
 
@@ -5293,14 +6449,14 @@
 
         /* Remember current epoch settings for resending */
         ssl->handshake->alt_transform_out = ssl->transform_out;
-        memcpy( ssl->handshake->alt_out_ctr, ssl->out_ctr, 8 );
+        memcpy( ssl->handshake->alt_out_ctr, ssl->cur_out_ctr, 8 );
 
         /* Set sequence_number to zero */
-        memset( ssl->out_ctr + 2, 0, 6 );
+        memset( ssl->cur_out_ctr + 2, 0, 6 );
 
         /* Increment epoch */
         for( i = 2; i > 0; i-- )
-            if( ++ssl->out_ctr[i - 1] != 0 )
+            if( ++ssl->cur_out_ctr[i - 1] != 0 )
                 break;
 
         /* The loop goes to its end iff the counter is wrapping */
@@ -5312,7 +6468,7 @@
     }
     else
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
-    memset( ssl->out_ctr, 0, 8 );
+    memset( ssl->cur_out_ctr, 0, 8 );
 
     ssl->transform_out = ssl->transform_negotiate;
     ssl->session_out = ssl->session_negotiate;
@@ -5333,12 +6489,21 @@
         mbedtls_ssl_send_flight_completed( ssl );
 #endif
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+        ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flight_transmit", ret );
+        return( ret );
+    }
+#endif
+
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write finished" ) );
 
     return( 0 );
@@ -5360,7 +6525,7 @@
 
     ssl->handshake->calc_finished( ssl, buf, ssl->conf->endpoint ^ 1 );
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
         return( ret );
@@ -5437,17 +6602,17 @@
     defined(MBEDTLS_SSL_PROTO_TLS1_1)
      mbedtls_md5_init(   &handshake->fin_md5  );
     mbedtls_sha1_init(   &handshake->fin_sha1 );
-     mbedtls_md5_starts( &handshake->fin_md5  );
-    mbedtls_sha1_starts( &handshake->fin_sha1 );
+     mbedtls_md5_starts_ret( &handshake->fin_md5  );
+    mbedtls_sha1_starts_ret( &handshake->fin_sha1 );
 #endif
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2)
 #if defined(MBEDTLS_SHA256_C)
     mbedtls_sha256_init(   &handshake->fin_sha256    );
-    mbedtls_sha256_starts( &handshake->fin_sha256, 0 );
+    mbedtls_sha256_starts_ret( &handshake->fin_sha256, 0 );
 #endif
 #if defined(MBEDTLS_SHA512_C)
     mbedtls_sha512_init(   &handshake->fin_sha512    );
-    mbedtls_sha512_starts( &handshake->fin_sha512, 1 );
+    mbedtls_sha512_starts_ret( &handshake->fin_sha512, 1 );
 #endif
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
 
@@ -5472,6 +6637,10 @@
 #endif
 #endif
 
+#if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
+    mbedtls_x509_crt_restart_init( &handshake->ecrs_ctx );
+#endif
+
 #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
     handshake->sni_authmode = MBEDTLS_SSL_VERIFY_UNSET;
 #endif
@@ -5501,7 +6670,7 @@
     if( ssl->session_negotiate )
         mbedtls_ssl_session_free( ssl->session_negotiate );
     if( ssl->handshake )
-        mbedtls_ssl_handshake_free( ssl->handshake );
+        mbedtls_ssl_handshake_free( ssl );
 
     /*
      * Either the pointers are now NULL or cleared properly and can be freed.
@@ -5591,6 +6760,78 @@
 }
 #endif /* MBEDTLS_SSL_DTLS_HELLO_VERIFY && MBEDTLS_SSL_SRV_C */
 
+/* Once ssl->out_hdr as the address of the beginning of the
+ * next outgoing record is set, deduce the other pointers.
+ *
+ * Note: For TLS, we save the implicit record sequence number
+ *       (entering MAC computation) in the 8 bytes before ssl->out_hdr,
+ *       and the caller has to make sure there's space for this.
+ */
+
+static void ssl_update_out_pointers( mbedtls_ssl_context *ssl,
+                                     mbedtls_ssl_transform *transform )
+{
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    {
+        ssl->out_ctr = ssl->out_hdr +  3;
+        ssl->out_len = ssl->out_hdr + 11;
+        ssl->out_iv  = ssl->out_hdr + 13;
+    }
+    else
+#endif
+    {
+        ssl->out_ctr = ssl->out_hdr - 8;
+        ssl->out_len = ssl->out_hdr + 3;
+        ssl->out_iv  = ssl->out_hdr + 5;
+    }
+
+    /* Adjust out_msg to make space for explicit IV, if used. */
+    if( transform != NULL &&
+        ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
+    {
+        ssl->out_msg = ssl->out_iv + transform->ivlen - transform->fixed_ivlen;
+    }
+    else
+        ssl->out_msg = ssl->out_iv;
+}
+
+/* Once ssl->in_hdr as the address of the beginning of the
+ * next incoming record is set, deduce the other pointers.
+ *
+ * Note: For TLS, we save the implicit record sequence number
+ *       (entering MAC computation) in the 8 bytes before ssl->in_hdr,
+ *       and the caller has to make sure there's space for this.
+ */
+
+static void ssl_update_in_pointers( mbedtls_ssl_context *ssl,
+                                    mbedtls_ssl_transform *transform )
+{
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    {
+        ssl->in_ctr = ssl->in_hdr +  3;
+        ssl->in_len = ssl->in_hdr + 11;
+        ssl->in_iv  = ssl->in_hdr + 13;
+    }
+    else
+#endif
+    {
+        ssl->in_ctr = ssl->in_hdr - 8;
+        ssl->in_len = ssl->in_hdr + 3;
+        ssl->in_iv  = ssl->in_hdr + 5;
+    }
+
+    /* Offset in_msg from in_iv to allow space for explicit IV, if used. */
+    if( transform != NULL &&
+        ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
+    {
+        ssl->in_msg = ssl->in_iv + transform->ivlen - transform->fixed_ivlen;
+    }
+    else
+        ssl->in_msg = ssl->in_iv;
+}
+
 /*
  * Initialize an SSL context
  */
@@ -5602,61 +6843,87 @@
 /*
  * Setup an SSL context
  */
+
+static void ssl_reset_in_out_pointers( mbedtls_ssl_context *ssl )
+{
+    /* Set the incoming and outgoing record pointers. */
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    {
+        ssl->out_hdr = ssl->out_buf;
+        ssl->in_hdr  = ssl->in_buf;
+    }
+    else
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+    {
+        ssl->out_hdr = ssl->out_buf + 8;
+        ssl->in_hdr  = ssl->in_buf  + 8;
+    }
+
+    /* Derive other internal pointers. */
+    ssl_update_out_pointers( ssl, NULL /* no transform enabled */ );
+    ssl_update_in_pointers ( ssl, NULL /* no transform enabled */ );
+}
+
 int mbedtls_ssl_setup( mbedtls_ssl_context *ssl,
                        const mbedtls_ssl_config *conf )
 {
     int ret;
-    const size_t len = MBEDTLS_SSL_BUFFER_LEN;
 
     ssl->conf = conf;
 
     /*
      * Prepare base structures
      */
-    if( ( ssl-> in_buf = mbedtls_calloc( 1, len ) ) == NULL ||
-        ( ssl->out_buf = mbedtls_calloc( 1, len ) ) == NULL )
+
+    /* Set to NULL in case of an error condition */
+    ssl->out_buf = NULL;
+
+    ssl->in_buf = mbedtls_calloc( 1, MBEDTLS_SSL_IN_BUFFER_LEN );
+    if( ssl->in_buf == NULL )
     {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed", len ) );
-        mbedtls_free( ssl->in_buf );
-        ssl->in_buf = NULL;
-        return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed", MBEDTLS_SSL_IN_BUFFER_LEN) );
+        ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
+        goto error;
     }
 
-#if defined(MBEDTLS_SSL_PROTO_DTLS)
-    if( conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    ssl->out_buf = mbedtls_calloc( 1, MBEDTLS_SSL_OUT_BUFFER_LEN );
+    if( ssl->out_buf == NULL )
     {
-        ssl->out_hdr = ssl->out_buf;
-        ssl->out_ctr = ssl->out_buf +  3;
-        ssl->out_len = ssl->out_buf + 11;
-        ssl->out_iv  = ssl->out_buf + 13;
-        ssl->out_msg = ssl->out_buf + 13;
-
-        ssl->in_hdr = ssl->in_buf;
-        ssl->in_ctr = ssl->in_buf +  3;
-        ssl->in_len = ssl->in_buf + 11;
-        ssl->in_iv  = ssl->in_buf + 13;
-        ssl->in_msg = ssl->in_buf + 13;
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed", MBEDTLS_SSL_OUT_BUFFER_LEN) );
+        ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
+        goto error;
     }
-    else
-#endif
-    {
-        ssl->out_ctr = ssl->out_buf;
-        ssl->out_hdr = ssl->out_buf +  8;
-        ssl->out_len = ssl->out_buf + 11;
-        ssl->out_iv  = ssl->out_buf + 13;
-        ssl->out_msg = ssl->out_buf + 13;
 
-        ssl->in_ctr = ssl->in_buf;
-        ssl->in_hdr = ssl->in_buf +  8;
-        ssl->in_len = ssl->in_buf + 11;
-        ssl->in_iv  = ssl->in_buf + 13;
-        ssl->in_msg = ssl->in_buf + 13;
-    }
+    ssl_reset_in_out_pointers( ssl );
 
     if( ( ret = ssl_handshake_init( ssl ) ) != 0 )
-        return( ret );
+        goto error;
 
     return( 0 );
+
+error:
+    mbedtls_free( ssl->in_buf );
+    mbedtls_free( ssl->out_buf );
+
+    ssl->conf = NULL;
+
+    ssl->in_buf = NULL;
+    ssl->out_buf = NULL;
+
+    ssl->in_hdr = NULL;
+    ssl->in_ctr = NULL;
+    ssl->in_len = NULL;
+    ssl->in_iv = NULL;
+    ssl->in_msg = NULL;
+
+    ssl->out_hdr = NULL;
+    ssl->out_ctr = NULL;
+    ssl->out_len = NULL;
+    ssl->out_iv = NULL;
+    ssl->out_msg = NULL;
+
+    return( ret );
 }
 
 /*
@@ -5670,6 +6937,11 @@
 {
     int ret;
 
+#if !defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE) ||     \
+    !defined(MBEDTLS_SSL_SRV_C)
+    ((void) partial);
+#endif
+
     ssl->state = MBEDTLS_SSL_HELLO_REQUEST;
 
     /* Cancel any possibly running timer */
@@ -5686,12 +6958,10 @@
     ssl->secure_renegotiation = MBEDTLS_SSL_LEGACY_RENEGOTIATION;
 
     ssl->in_offt = NULL;
+    ssl_reset_in_out_pointers( ssl );
 
-    ssl->in_msg = ssl->in_buf + 13;
     ssl->in_msgtype = 0;
     ssl->in_msglen = 0;
-    if( partial == 0 )
-        ssl->in_left = 0;
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     ssl->next_record_offset = 0;
     ssl->in_epoch = 0;
@@ -5705,7 +6975,6 @@
 
     ssl->keep_current_message = 0;
 
-    ssl->out_msg = ssl->out_buf + 13;
     ssl->out_msgtype = 0;
     ssl->out_msglen = 0;
     ssl->out_left = 0;
@@ -5714,12 +6983,23 @@
         ssl->split_done = 0;
 #endif
 
+    memset( ssl->cur_out_ctr, 0, sizeof( ssl->cur_out_ctr ) );
+
     ssl->transform_in = NULL;
     ssl->transform_out = NULL;
 
-    memset( ssl->out_buf, 0, MBEDTLS_SSL_BUFFER_LEN );
+    ssl->session_in = NULL;
+    ssl->session_out = NULL;
+
+    memset( ssl->out_buf, 0, MBEDTLS_SSL_OUT_BUFFER_LEN );
+
+#if defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE) && defined(MBEDTLS_SSL_SRV_C)
     if( partial == 0 )
-        memset( ssl->in_buf, 0, MBEDTLS_SSL_BUFFER_LEN );
+#endif /* MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE && MBEDTLS_SSL_SRV_C */
+    {
+        ssl->in_left = 0;
+        memset( ssl->in_buf, 0, MBEDTLS_SSL_IN_BUFFER_LEN );
+    }
 
 #if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
     if( mbedtls_ssl_hw_record_reset != NULL )
@@ -5752,7 +7032,9 @@
 #endif
 
 #if defined(MBEDTLS_SSL_DTLS_HELLO_VERIFY) && defined(MBEDTLS_SSL_SRV_C)
+#if defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE)
     if( partial == 0 )
+#endif
     {
         mbedtls_free( ssl->cli_id );
         ssl->cli_id = NULL;
@@ -5803,7 +7085,15 @@
 #endif
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
-void mbedtls_ssl_conf_handshake_timeout( mbedtls_ssl_config *conf, uint32_t min, uint32_t max )
+
+void mbedtls_ssl_set_datagram_packing( mbedtls_ssl_context *ssl,
+                                       unsigned allow_packing )
+{
+    ssl->disable_datagram_packing = !allow_packing;
+}
+
+void mbedtls_ssl_conf_handshake_timeout( mbedtls_ssl_config *conf,
+                                         uint32_t min, uint32_t max )
 {
     conf->hs_timeout_min = min;
     conf->hs_timeout_max = max;
@@ -5853,6 +7143,13 @@
     ssl->f_recv_timeout = f_recv_timeout;
 }
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+void mbedtls_ssl_set_mtu( mbedtls_ssl_context *ssl, uint16_t mtu )
+{
+    ssl->mtu = mtu;
+}
+#endif
+
 void mbedtls_ssl_conf_read_timeout( mbedtls_ssl_config *conf, uint32_t timeout )
 {
     conf->read_timeout   = timeout;
@@ -5939,27 +7236,27 @@
                                 mbedtls_x509_crt *cert,
                                 mbedtls_pk_context *key )
 {
-    mbedtls_ssl_key_cert *new;
+    mbedtls_ssl_key_cert *new_cert;
 
-    new = mbedtls_calloc( 1, sizeof( mbedtls_ssl_key_cert ) );
-    if( new == NULL )
+    new_cert = mbedtls_calloc( 1, sizeof( mbedtls_ssl_key_cert ) );
+    if( new_cert == NULL )
         return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
 
-    new->cert = cert;
-    new->key  = key;
-    new->next = NULL;
+    new_cert->cert = cert;
+    new_cert->key  = key;
+    new_cert->next = NULL;
 
     /* Update head is the list was null, else add to the end */
     if( *head == NULL )
     {
-        *head = new;
+        *head = new_cert;
     }
     else
     {
         mbedtls_ssl_key_cert *cur = *head;
         while( cur->next != NULL )
             cur = cur->next;
-        cur->next = new;
+        cur->next = new_cert;
     }
 
     return( 0 );
@@ -6044,17 +7341,24 @@
 
     /* Identity len will be encoded on two bytes */
     if( ( psk_identity_len >> 16 ) != 0 ||
-        psk_identity_len > MBEDTLS_SSL_MAX_CONTENT_LEN )
+        psk_identity_len > MBEDTLS_SSL_OUT_CONTENT_LEN )
     {
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
     }
 
-    if( conf->psk != NULL || conf->psk_identity != NULL )
+    if( conf->psk != NULL )
     {
+        mbedtls_platform_zeroize( conf->psk, conf->psk_len );
+
         mbedtls_free( conf->psk );
-        mbedtls_free( conf->psk_identity );
         conf->psk = NULL;
+        conf->psk_len = 0;
+    }
+    if( conf->psk_identity != NULL )
+    {
+        mbedtls_free( conf->psk_identity );
         conf->psk_identity = NULL;
+        conf->psk_identity_len = 0;
     }
 
     if( ( conf->psk = mbedtls_calloc( 1, psk_len ) ) == NULL ||
@@ -6086,7 +7390,12 @@
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
 
     if( ssl->handshake->psk != NULL )
+    {
+        mbedtls_platform_zeroize( ssl->handshake->psk,
+                                  ssl->handshake->psk_len );
         mbedtls_free( ssl->handshake->psk );
+        ssl->handshake->psk_len = 0;
+    }
 
     if( ( ssl->handshake->psk = mbedtls_calloc( 1, psk_len ) ) == NULL )
         return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
@@ -6108,6 +7417,8 @@
 #endif /* MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED */
 
 #if defined(MBEDTLS_DHM_C) && defined(MBEDTLS_SSL_SRV_C)
+
+#if !defined(MBEDTLS_DEPRECATED_REMOVED)
 int mbedtls_ssl_conf_dh_param( mbedtls_ssl_config *conf, const char *dhm_P, const char *dhm_G )
 {
     int ret;
@@ -6122,6 +7433,24 @@
 
     return( 0 );
 }
+#endif /* MBEDTLS_DEPRECATED_REMOVED */
+
+int mbedtls_ssl_conf_dh_param_bin( mbedtls_ssl_config *conf,
+                                   const unsigned char *dhm_P, size_t P_len,
+                                   const unsigned char *dhm_G, size_t G_len )
+{
+    int ret;
+
+    if( ( ret = mbedtls_mpi_read_binary( &conf->dhm_P, dhm_P, P_len ) ) != 0 ||
+        ( ret = mbedtls_mpi_read_binary( &conf->dhm_G, dhm_G, G_len ) ) != 0 )
+    {
+        mbedtls_mpi_free( &conf->dhm_P );
+        mbedtls_mpi_free( &conf->dhm_G );
+        return( ret );
+    }
+
+    return( 0 );
+}
 
 int mbedtls_ssl_conf_dh_param_ctx( mbedtls_ssl_config *conf, mbedtls_dhm_context *dhm_ctx )
 {
@@ -6159,7 +7488,7 @@
 {
     conf->sig_hashes = hashes;
 }
-#endif
+#endif /* MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED */
 
 #if defined(MBEDTLS_ECP_C)
 /*
@@ -6170,36 +7499,53 @@
 {
     conf->curve_list = curve_list;
 }
-#endif
+#endif /* MBEDTLS_ECP_C */
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
 int mbedtls_ssl_set_hostname( mbedtls_ssl_context *ssl, const char *hostname )
 {
-    size_t hostname_len;
+    /* Initialize to suppress unnecessary compiler warning */
+    size_t hostname_len = 0;
+
+    /* Check if new hostname is valid before
+     * making any change to current one */
+    if( hostname != NULL )
+    {
+        hostname_len = strlen( hostname );
+
+        if( hostname_len > MBEDTLS_SSL_MAX_HOST_NAME_LEN )
+            return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+    }
+
+    /* Now it's clear that we will overwrite the old hostname,
+     * so we can free it safely */
+
+    if( ssl->hostname != NULL )
+    {
+        mbedtls_platform_zeroize( ssl->hostname, strlen( ssl->hostname ) );
+        mbedtls_free( ssl->hostname );
+    }
+
+    /* Passing NULL as hostname shall clear the old one */
 
     if( hostname == NULL )
-        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+    {
+        ssl->hostname = NULL;
+    }
+    else
+    {
+        ssl->hostname = mbedtls_calloc( 1, hostname_len + 1 );
+        if( ssl->hostname == NULL )
+            return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
 
-    hostname_len = strlen( hostname );
+        memcpy( ssl->hostname, hostname, hostname_len );
 
-    if( hostname_len + 1 == 0 )
-        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
-
-    if( hostname_len > MBEDTLS_SSL_MAX_HOST_NAME_LEN )
-        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
-
-    ssl->hostname = mbedtls_calloc( 1, hostname_len + 1 );
-
-    if( ssl->hostname == NULL )
-        return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
-
-    memcpy( ssl->hostname, hostname, hostname_len );
-
-    ssl->hostname[hostname_len] = '\0';
+        ssl->hostname[hostname_len] = '\0';
+    }
 
     return( 0 );
 }
-#endif
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
 
 #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
 void mbedtls_ssl_conf_sni( mbedtls_ssl_config *conf,
@@ -6296,7 +7642,7 @@
 int mbedtls_ssl_conf_max_frag_len( mbedtls_ssl_config *conf, unsigned char mfl_code )
 {
     if( mfl_code >= MBEDTLS_SSL_MAX_FRAG_LEN_INVALID ||
-        mfl_code_to_length[mfl_code] > MBEDTLS_SSL_MAX_CONTENT_LEN )
+        ssl_mfl_code_to_length( mfl_code ) > MBEDTLS_TLS_EXT_ADV_CONTENT_LEN )
     {
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
     }
@@ -6375,6 +7721,43 @@
 }
 #endif
 
+#if defined(MBEDTLS_SSL_ASYNC_PRIVATE)
+void mbedtls_ssl_conf_async_private_cb(
+    mbedtls_ssl_config *conf,
+    mbedtls_ssl_async_sign_t *f_async_sign,
+    mbedtls_ssl_async_decrypt_t *f_async_decrypt,
+    mbedtls_ssl_async_resume_t *f_async_resume,
+    mbedtls_ssl_async_cancel_t *f_async_cancel,
+    void *async_config_data )
+{
+    conf->f_async_sign_start = f_async_sign;
+    conf->f_async_decrypt_start = f_async_decrypt;
+    conf->f_async_resume = f_async_resume;
+    conf->f_async_cancel = f_async_cancel;
+    conf->p_async_config_data = async_config_data;
+}
+
+void *mbedtls_ssl_conf_get_async_config_data( const mbedtls_ssl_config *conf )
+{
+    return( conf->p_async_config_data );
+}
+
+void *mbedtls_ssl_get_async_operation_data( const mbedtls_ssl_context *ssl )
+{
+    if( ssl->handshake == NULL )
+        return( NULL );
+    else
+        return( ssl->handshake->user_async_ctx );
+}
+
+void mbedtls_ssl_set_async_operation_data( mbedtls_ssl_context *ssl,
+                                 void *ctx )
+{
+    if( ssl->handshake != NULL )
+        ssl->handshake->user_async_ctx = ctx;
+}
+#endif /* MBEDTLS_SSL_ASYNC_PRIVATE */
+
 /*
  * SSL get accessors
  */
@@ -6383,6 +7766,61 @@
     return( ssl->in_offt == NULL ? 0 : ssl->in_msglen );
 }
 
+int mbedtls_ssl_check_pending( const mbedtls_ssl_context *ssl )
+{
+    /*
+     * Case A: We're currently holding back
+     * a message for further processing.
+     */
+
+    if( ssl->keep_current_message == 1 )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: record held back for processing" ) );
+        return( 1 );
+    }
+
+    /*
+     * Case B: Further records are pending in the current datagram.
+     */
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+        ssl->in_left > ssl->next_record_offset )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: more records within current datagram" ) );
+        return( 1 );
+    }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+    /*
+     * Case C: A handshake message is being processed.
+     */
+
+    if( ssl->in_hslen > 0 && ssl->in_hslen < ssl->in_msglen )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: more handshake messages within current record" ) );
+        return( 1 );
+    }
+
+    /*
+     * Case D: An application data message is being processed
+     */
+    if( ssl->in_offt != NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: application data record is being processed" ) );
+        return( 1 );
+    }
+
+    /*
+     * In all other cases, the rest of the message can be dropped.
+     * As in ssl_get_next_record, this needs to be adapted if
+     * we implement support for multiple alerts in single records.
+     */
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: nothing pending" ) );
+    return( 0 );
+}
+
 uint32_t mbedtls_ssl_get_verify_result( const mbedtls_ssl_context *ssl )
 {
     if( ssl->session != NULL )
@@ -6442,28 +7880,47 @@
 
 int mbedtls_ssl_get_record_expansion( const mbedtls_ssl_context *ssl )
 {
-    size_t transform_expansion;
+    size_t transform_expansion = 0;
     const mbedtls_ssl_transform *transform = ssl->transform_out;
+    unsigned block_size;
+
+    if( transform == NULL )
+        return( (int) mbedtls_ssl_hdr_len( ssl ) );
 
 #if defined(MBEDTLS_ZLIB_SUPPORT)
     if( ssl->session_out->compression != MBEDTLS_SSL_COMPRESS_NULL )
         return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
 #endif
 
-    if( transform == NULL )
-        return( (int) mbedtls_ssl_hdr_len( ssl ) );
-
     switch( mbedtls_cipher_get_cipher_mode( &transform->cipher_ctx_enc ) )
     {
         case MBEDTLS_MODE_GCM:
         case MBEDTLS_MODE_CCM:
+        case MBEDTLS_MODE_CHACHAPOLY:
         case MBEDTLS_MODE_STREAM:
             transform_expansion = transform->minlen;
             break;
 
         case MBEDTLS_MODE_CBC:
-            transform_expansion = transform->maclen
-                      + mbedtls_cipher_get_block_size( &transform->cipher_ctx_enc );
+
+            block_size = mbedtls_cipher_get_block_size(
+                &transform->cipher_ctx_enc );
+
+            /* Expansion due to the addition of the MAC. */
+            transform_expansion += transform->maclen;
+
+            /* Expansion due to the addition of CBC padding;
+             * Theoretically up to 256 bytes, but we never use
+             * more than the block size of the underlying cipher. */
+            transform_expansion += block_size;
+
+            /* For TLS 1.1 or higher, an explicit IV is added
+             * after the record header. */
+#if defined(MBEDTLS_SSL_PROTO_TLS1_1) || defined(MBEDTLS_SSL_PROTO_TLS1_2)
+            if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
+                transform_expansion += block_size;
+#endif /* MBEDTLS_SSL_PROTO_TLS1_1 || MBEDTLS_SSL_PROTO_TLS1_2 */
+
             break;
 
         default:
@@ -6482,21 +7939,91 @@
     /*
      * Assume mfl_code is correct since it was checked when set
      */
-    max_len = mfl_code_to_length[ssl->conf->mfl_code];
+    max_len = ssl_mfl_code_to_length( ssl->conf->mfl_code );
 
-    /*
-     * Check if a smaller max length was negotiated
-     */
+    /* Check if a smaller max length was negotiated */
     if( ssl->session_out != NULL &&
-        mfl_code_to_length[ssl->session_out->mfl_code] < max_len )
+        ssl_mfl_code_to_length( ssl->session_out->mfl_code ) < max_len )
     {
-        max_len = mfl_code_to_length[ssl->session_out->mfl_code];
+        max_len = ssl_mfl_code_to_length( ssl->session_out->mfl_code );
     }
 
-    return max_len;
+    /* During a handshake, use the value being negotiated */
+    if( ssl->session_negotiate != NULL &&
+        ssl_mfl_code_to_length( ssl->session_negotiate->mfl_code ) < max_len )
+    {
+        max_len = ssl_mfl_code_to_length( ssl->session_negotiate->mfl_code );
+    }
+
+    return( max_len );
 }
 #endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+static size_t ssl_get_current_mtu( const mbedtls_ssl_context *ssl )
+{
+    /* Return unlimited mtu for client hello messages to avoid fragmentation. */
+    if( ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT &&
+        ( ssl->state == MBEDTLS_SSL_CLIENT_HELLO ||
+          ssl->state == MBEDTLS_SSL_SERVER_HELLO ) )
+        return ( 0 );
+
+    if( ssl->handshake == NULL || ssl->handshake->mtu == 0 )
+        return( ssl->mtu );
+
+    if( ssl->mtu == 0 )
+        return( ssl->handshake->mtu );
+
+    return( ssl->mtu < ssl->handshake->mtu ?
+            ssl->mtu : ssl->handshake->mtu );
+}
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+int mbedtls_ssl_get_max_out_record_payload( const mbedtls_ssl_context *ssl )
+{
+    size_t max_len = MBEDTLS_SSL_OUT_CONTENT_LEN;
+
+#if !defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH) && \
+    !defined(MBEDTLS_SSL_PROTO_DTLS)
+    (void) ssl;
+#endif
+
+#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
+    const size_t mfl = mbedtls_ssl_get_max_frag_len( ssl );
+
+    if( max_len > mfl )
+        max_len = mfl;
+#endif
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl_get_current_mtu( ssl ) != 0 )
+    {
+        const size_t mtu = ssl_get_current_mtu( ssl );
+        const int ret = mbedtls_ssl_get_record_expansion( ssl );
+        const size_t overhead = (size_t) ret;
+
+        if( ret < 0 )
+            return( ret );
+
+        if( mtu <= overhead )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "MTU too low for record expansion" ) );
+            return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
+        }
+
+        if( max_len > mtu - overhead )
+            max_len = mtu - overhead;
+    }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+#if !defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH) &&        \
+    !defined(MBEDTLS_SSL_PROTO_DTLS)
+    ((void) ssl);
+#endif
+
+    return( (int) max_len );
+}
+
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
 const mbedtls_x509_crt *mbedtls_ssl_get_peer_cert( const mbedtls_ssl_context *ssl )
 {
@@ -6584,9 +8111,9 @@
     ssl->out_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;
     ssl->out_msg[0]  = MBEDTLS_SSL_HS_HELLO_REQUEST;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -6716,7 +8243,7 @@
 
     in_ctr_cmp = memcmp( ssl->in_ctr + ep_len,
                         ssl->conf->renego_period + ep_len, 8 - ep_len );
-    out_ctr_cmp = memcmp( ssl->out_ctr + ep_len,
+    out_ctr_cmp = memcmp( ssl->cur_out_ctr + ep_len,
                           ssl->conf->renego_period + ep_len, 8 - ep_len );
 
     if( in_ctr_cmp <= 0 && out_ctr_cmp <= 0 )
@@ -6751,7 +8278,7 @@
         if( ssl->handshake != NULL &&
             ssl->handshake->retransmit_state == MBEDTLS_SSL_RETRANS_SENDING )
         {
-            if( ( ret = mbedtls_ssl_resend( ssl ) ) != 0 )
+            if( ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
                 return( ret );
         }
     }
@@ -6790,42 +8317,8 @@
         }
     }
 
-    /*
-     * TODO
-     *
-     * The logic should be streamlined here:
-     *
-     * Instead of
-     *
-     * - Manually checking whether ssl->in_offt is NULL
-     * - Fetching a new record if yes
-     * - Setting ssl->in_offt if one finds an application record
-     * - Resetting keep_current_message after handling the application data
-     *
-     * one should
-     *
-     * - Adapt read_record to set ssl->in_offt automatically
-     *   when a new application data record is processed.
-     * - Always call mbedtls_ssl_read_record here.
-     *
-     * This way, the logic of ssl_read would be much clearer:
-     *
-     * (1) Always call record layer and see what kind of record is on
-     *     and have it ready for consumption (in particular, in_offt
-     *     properly set for application data records).
-     * (2) If it's application data (either freshly fetched
-     *     or something already being partially processed),
-     *     serve the read request from it.
-     * (3) If it's something different from application data,
-     *     handle it accordingly, e.g. potentially start a
-     *     renegotiation.
-     *
-     * This will also remove the need to manually reset
-     * ssl->keep_current_message = 0 below.
-     *
-     */
-
-    if( ssl->in_offt == NULL )
+    /* Loop as long as no application data record is available */
+    while( ssl->in_offt == NULL )
     {
         /* Start timer if not already running */
         if( ssl->f_get_timer != NULL &&
@@ -6834,7 +8327,7 @@
             ssl_set_timer( ssl, ssl->conf->read_timeout );
         }
 
-        if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+        if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
         {
             if( ret == MBEDTLS_ERR_SSL_CONN_EOF )
                 return( 0 );
@@ -6849,7 +8342,7 @@
             /*
              * OpenSSL sends empty messages to randomize the IV
              */
-            if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+            if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
             {
                 if( ret == MBEDTLS_ERR_SSL_CONN_EOF )
                     return( 0 );
@@ -6859,7 +8352,6 @@
             }
         }
 
-#if defined(MBEDTLS_SSL_RENEGOTIATION)
         if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE )
         {
             MBEDTLS_SSL_DEBUG_MSG( 1, ( "received handshake message" ) );
@@ -6880,7 +8372,9 @@
                 /* With DTLS, drop the packet (probably from last handshake) */
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
                 if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
-                    return( MBEDTLS_ERR_SSL_WANT_READ );
+                {
+                    continue;
+                }
 #endif
                 return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
             }
@@ -6895,18 +8389,43 @@
                 /* With DTLS, drop the packet (probably from last handshake) */
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
                 if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
-                    return( MBEDTLS_ERR_SSL_WANT_READ );
+                {
+                    continue;
+                }
 #endif
                 return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
             }
 #endif /* MBEDTLS_SSL_SRV_C */
 
+#if defined(MBEDTLS_SSL_RENEGOTIATION)
             /* Determine whether renegotiation attempt should be accepted */
+            if( ! ( ssl->conf->disable_renegotiation == MBEDTLS_SSL_RENEGOTIATION_DISABLED ||
+                    ( ssl->secure_renegotiation == MBEDTLS_SSL_LEGACY_RENEGOTIATION &&
+                      ssl->conf->allow_legacy_renegotiation ==
+                                                   MBEDTLS_SSL_LEGACY_NO_RENEGOTIATION ) ) )
+            {
+                /*
+                 * Accept renegotiation request
+                 */
 
-            if( ssl->conf->disable_renegotiation == MBEDTLS_SSL_RENEGOTIATION_DISABLED ||
-                ( ssl->secure_renegotiation == MBEDTLS_SSL_LEGACY_RENEGOTIATION &&
-                  ssl->conf->allow_legacy_renegotiation ==
-                                                MBEDTLS_SSL_LEGACY_NO_RENEGOTIATION ) )
+                /* DTLS clients need to know renego is server-initiated */
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+                if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+                    ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT )
+                {
+                    ssl->renego_status = MBEDTLS_SSL_RENEGOTIATION_PENDING;
+                }
+#endif
+                ret = ssl_start_renegotiation( ssl );
+                if( ret != MBEDTLS_ERR_SSL_WAITING_SERVER_HELLO_RENEGO &&
+                    ret != 0 )
+                {
+                    MBEDTLS_SSL_DEBUG_RET( 1, "ssl_start_renegotiation", ret );
+                    return( ret );
+                }
+            }
+            else
+#endif /* MBEDTLS_SSL_RENEGOTIATION */
             {
                 /*
                  * Refuse renegotiation
@@ -6944,31 +8463,28 @@
                     return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
                 }
             }
-            else
-            {
-                /*
-                 * Accept renegotiation request
-                 */
 
-                /* DTLS clients need to know renego is server-initiated */
-#if defined(MBEDTLS_SSL_PROTO_DTLS)
-                if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
-                    ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT )
-                {
-                    ssl->renego_status = MBEDTLS_SSL_RENEGOTIATION_PENDING;
-                }
-#endif
-                ret = ssl_start_renegotiation( ssl );
-                if( ret != MBEDTLS_ERR_SSL_WAITING_SERVER_HELLO_RENEGO &&
-                    ret != 0 )
-                {
-                    MBEDTLS_SSL_DEBUG_RET( 1, "ssl_start_renegotiation", ret );
-                    return( ret );
-                }
-            }
-
-            return( MBEDTLS_ERR_SSL_WANT_READ );
+            /* At this point, we don't know whether the renegotiation has been
+             * completed or not. The cases to consider are the following:
+             * 1) The renegotiation is complete. In this case, no new record
+             *    has been read yet.
+             * 2) The renegotiation is incomplete because the client received
+             *    an application data record while awaiting the ServerHello.
+             * 3) The renegotiation is incomplete because the client received
+             *    a non-handshake, non-application data message while awaiting
+             *    the ServerHello.
+             * In each of these case, looping will be the proper action:
+             * - For 1), the next iteration will read a new record and check
+             *   if it's application data.
+             * - For 2), the loop condition isn't satisfied as application data
+             *   is present, hence continue is the same as break
+             * - For 3), the loop condition is satisfied and read_record
+             *   will re-deliver the message that was held back by the client
+             *   when expecting the ServerHello.
+             */
+            continue;
         }
+#if defined(MBEDTLS_SSL_RENEGOTIATION)
         else if( ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_PENDING )
         {
             if( ssl->conf->renego_max_records >= 0 )
@@ -7045,15 +8561,28 @@
 }
 
 /*
- * Send application data to be encrypted by the SSL layer,
- * taking care of max fragment length and buffer size
+ * Send application data to be encrypted by the SSL layer, taking care of max
+ * fragment length and buffer size.
+ *
+ * According to RFC 5246 Section 6.2.1:
+ *
+ *      Zero-length fragments of Application data MAY be sent as they are
+ *      potentially useful as a traffic analysis countermeasure.
+ *
+ * Therefore, it is possible that the input message length is 0 and the
+ * corresponding return code is 0 on success.
  */
 static int ssl_write_real( mbedtls_ssl_context *ssl,
                            const unsigned char *buf, size_t len )
 {
-    int ret;
-#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
-    size_t max_len = mbedtls_ssl_get_max_frag_len( ssl );
+    int ret = mbedtls_ssl_get_max_out_record_payload( ssl );
+    const size_t max_len = (size_t) ret;
+
+    if( ret < 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_get_max_out_record_payload", ret );
+        return( ret );
+    }
 
     if( len > max_len )
     {
@@ -7069,10 +8598,15 @@
 #endif
             len = max_len;
     }
-#endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
 
     if( ssl->out_left != 0 )
     {
+        /*
+         * The user has previously tried to send the data and
+         * MBEDTLS_ERR_SSL_WANT_WRITE or the message was only partially
+         * written. In this case, we expect the high-level write function
+         * (e.g. mbedtls_ssl_write()) to be called with the same parameters
+         */
         if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
         {
             MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flush_output", ret );
@@ -7081,11 +8615,16 @@
     }
     else
     {
+        /*
+         * The user is trying to send a message the first time, so we need to
+         * copy the data into the internal buffers and setup the data structure
+         * to keep track of partial writes
+         */
         ssl->out_msglen  = len;
         ssl->out_msgtype = MBEDTLS_SSL_MSG_APPLICATION_DATA;
         memcpy( ssl->out_msg, buf, len );
 
-        if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+        if( ( ret = mbedtls_ssl_write_record( ssl, SSL_FORCE_FLUSH ) ) != 0 )
         {
             MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
             return( ret );
@@ -7100,7 +8639,7 @@
  *
  * With non-blocking I/O, ssl_write_real() may return WANT_WRITE,
  * then the caller will call us again with the same arguments, so
- * remember wether we already did the split or not.
+ * remember whether we already did the split or not.
  */
 #if defined(MBEDTLS_SSL_CBC_RECORD_SPLITTING)
 static int ssl_write_split( mbedtls_ssl_context *ssl,
@@ -7220,7 +8759,7 @@
     mbedtls_md_free( &transform->md_ctx_enc );
     mbedtls_md_free( &transform->md_ctx_dec );
 
-    mbedtls_zeroize( transform, sizeof( mbedtls_ssl_transform ) );
+    mbedtls_platform_zeroize( transform, sizeof( mbedtls_ssl_transform ) );
 }
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
@@ -7237,11 +8776,57 @@
 }
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
 
-void mbedtls_ssl_handshake_free( mbedtls_ssl_handshake_params *handshake )
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+
+static void ssl_buffering_free( mbedtls_ssl_context *ssl )
 {
+    unsigned offset;
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+
+    if( hs == NULL )
+        return;
+
+    ssl_free_buffered_record( ssl );
+
+    for( offset = 0; offset < MBEDTLS_SSL_MAX_BUFFERED_HS; offset++ )
+        ssl_buffering_free_slot( ssl, offset );
+}
+
+static void ssl_buffering_free_slot( mbedtls_ssl_context *ssl,
+                                     uint8_t slot )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    mbedtls_ssl_hs_buffer * const hs_buf = &hs->buffering.hs[slot];
+
+    if( slot >= MBEDTLS_SSL_MAX_BUFFERED_HS )
+        return;
+
+    if( hs_buf->is_valid == 1 )
+    {
+        hs->buffering.total_bytes_buffered -= hs_buf->data_len;
+        mbedtls_platform_zeroize( hs_buf->data, hs_buf->data_len );
+        mbedtls_free( hs_buf->data );
+        memset( hs_buf, 0, sizeof( mbedtls_ssl_hs_buffer ) );
+    }
+}
+
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+void mbedtls_ssl_handshake_free( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_handshake_params *handshake = ssl->handshake;
+
     if( handshake == NULL )
         return;
 
+#if defined(MBEDTLS_SSL_ASYNC_PRIVATE)
+    if( ssl->conf->f_async_cancel != NULL && handshake->async_in_progress != 0 )
+    {
+        ssl->conf->f_async_cancel( ssl );
+        handshake->async_in_progress = 0;
+    }
+#endif /* MBEDTLS_SSL_ASYNC_PRIVATE */
+
 #if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) || \
     defined(MBEDTLS_SSL_PROTO_TLS1_1)
     mbedtls_md5_free(    &handshake->fin_md5  );
@@ -7280,7 +8865,7 @@
 #if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
     if( handshake->psk != NULL )
     {
-        mbedtls_zeroize( handshake->psk, handshake->psk_len );
+        mbedtls_platform_zeroize( handshake->psk, handshake->psk_len );
         mbedtls_free( handshake->psk );
     }
 #endif
@@ -7304,13 +8889,18 @@
     }
 #endif /* MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_SSL_SERVER_NAME_INDICATION */
 
-#if defined(MBEDTLS_SSL_PROTO_DTLS)
-    mbedtls_free( handshake->verify_cookie );
-    mbedtls_free( handshake->hs_msg );
-    ssl_flight_free( handshake->flight );
+#if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
+    mbedtls_x509_crt_restart_free( &handshake->ecrs_ctx );
 #endif
 
-    mbedtls_zeroize( handshake, sizeof( mbedtls_ssl_handshake_params ) );
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    mbedtls_free( handshake->verify_cookie );
+    ssl_flight_free( handshake->flight );
+    ssl_buffering_free( ssl );
+#endif
+
+    mbedtls_platform_zeroize( handshake,
+                              sizeof( mbedtls_ssl_handshake_params ) );
 }
 
 void mbedtls_ssl_session_free( mbedtls_ssl_session *session )
@@ -7330,7 +8920,7 @@
     mbedtls_free( session->ticket );
 #endif
 
-    mbedtls_zeroize( session, sizeof( mbedtls_ssl_session ) );
+    mbedtls_platform_zeroize( session, sizeof( mbedtls_ssl_session ) );
 }
 
 /*
@@ -7345,20 +8935,20 @@
 
     if( ssl->out_buf != NULL )
     {
-        mbedtls_zeroize( ssl->out_buf, MBEDTLS_SSL_BUFFER_LEN );
+        mbedtls_platform_zeroize( ssl->out_buf, MBEDTLS_SSL_OUT_BUFFER_LEN );
         mbedtls_free( ssl->out_buf );
     }
 
     if( ssl->in_buf != NULL )
     {
-        mbedtls_zeroize( ssl->in_buf, MBEDTLS_SSL_BUFFER_LEN );
+        mbedtls_platform_zeroize( ssl->in_buf, MBEDTLS_SSL_IN_BUFFER_LEN );
         mbedtls_free( ssl->in_buf );
     }
 
 #if defined(MBEDTLS_ZLIB_SUPPORT)
     if( ssl->compress_buf != NULL )
     {
-        mbedtls_zeroize( ssl->compress_buf, MBEDTLS_SSL_BUFFER_LEN );
+        mbedtls_platform_zeroize( ssl->compress_buf, MBEDTLS_SSL_COMPRESS_BUFFER_LEN );
         mbedtls_free( ssl->compress_buf );
     }
 #endif
@@ -7371,7 +8961,7 @@
 
     if( ssl->handshake )
     {
-        mbedtls_ssl_handshake_free( ssl->handshake );
+        mbedtls_ssl_handshake_free( ssl );
         mbedtls_ssl_transform_free( ssl->transform_negotiate );
         mbedtls_ssl_session_free( ssl->session_negotiate );
 
@@ -7389,7 +8979,7 @@
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
     if( ssl->hostname != NULL )
     {
-        mbedtls_zeroize( ssl->hostname, strlen( ssl->hostname ) );
+        mbedtls_platform_zeroize( ssl->hostname, strlen( ssl->hostname ) );
         mbedtls_free( ssl->hostname );
     }
 #endif
@@ -7409,7 +8999,7 @@
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= free" ) );
 
     /* Actually clear after last debug message */
-    mbedtls_zeroize( ssl, sizeof( mbedtls_ssl_context ) );
+    mbedtls_platform_zeroize( ssl, sizeof( mbedtls_ssl_context ) );
 }
 
 /*
@@ -7530,9 +9120,14 @@
 #if defined(MBEDTLS_DHM_C) && defined(MBEDTLS_SSL_SRV_C)
             if( endpoint == MBEDTLS_SSL_IS_SERVER )
             {
-                if( ( ret = mbedtls_ssl_conf_dh_param( conf,
-                                MBEDTLS_DHM_RFC5114_MODP_2048_P,
-                                MBEDTLS_DHM_RFC5114_MODP_2048_G ) ) != 0 )
+                const unsigned char dhm_p[] =
+                    MBEDTLS_DHM_RFC3526_MODP_2048_P_BIN;
+                const unsigned char dhm_g[] =
+                    MBEDTLS_DHM_RFC3526_MODP_2048_G_BIN;
+
+                if ( ( ret = mbedtls_ssl_conf_dh_param_bin( conf,
+                                               dhm_p, sizeof( dhm_p ),
+                                               dhm_g, sizeof( dhm_g ) ) ) != 0 )
                 {
                     return( ret );
                 }
@@ -7576,8 +9171,14 @@
          * Default
          */
         default:
-            conf->min_major_ver = MBEDTLS_SSL_MAJOR_VERSION_3;
-            conf->min_minor_ver = MBEDTLS_SSL_MINOR_VERSION_1; /* TLS 1.0 */
+            conf->min_major_ver = ( MBEDTLS_SSL_MIN_MAJOR_VERSION >
+                                    MBEDTLS_SSL_MIN_VALID_MAJOR_VERSION ) ?
+                                    MBEDTLS_SSL_MIN_MAJOR_VERSION :
+                                    MBEDTLS_SSL_MIN_VALID_MAJOR_VERSION;
+            conf->min_minor_ver = ( MBEDTLS_SSL_MIN_MINOR_VERSION >
+                                    MBEDTLS_SSL_MIN_VALID_MINOR_VERSION ) ?
+                                    MBEDTLS_SSL_MIN_MINOR_VERSION :
+                                    MBEDTLS_SSL_MIN_VALID_MINOR_VERSION;
             conf->max_major_ver = MBEDTLS_SSL_MAX_MAJOR_VERSION;
             conf->max_minor_ver = MBEDTLS_SSL_MAX_MINOR_VERSION;
 
@@ -7625,11 +9226,17 @@
 #if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
     if( conf->psk != NULL )
     {
-        mbedtls_zeroize( conf->psk, conf->psk_len );
-        mbedtls_zeroize( conf->psk_identity, conf->psk_identity_len );
+        mbedtls_platform_zeroize( conf->psk, conf->psk_len );
         mbedtls_free( conf->psk );
-        mbedtls_free( conf->psk_identity );
+        conf->psk = NULL;
         conf->psk_len = 0;
+    }
+
+    if( conf->psk_identity != NULL )
+    {
+        mbedtls_platform_zeroize( conf->psk_identity, conf->psk_identity_len );
+        mbedtls_free( conf->psk_identity );
+        conf->psk_identity = NULL;
         conf->psk_identity_len = 0;
     }
 #endif
@@ -7638,7 +9245,7 @@
     ssl_key_cert_free( conf->key_cert );
 #endif
 
-    mbedtls_zeroize( conf, sizeof( mbedtls_ssl_config ) );
+    mbedtls_platform_zeroize( conf, sizeof( mbedtls_ssl_config ) );
 }
 
 #if defined(MBEDTLS_PK_C) && \
@@ -8032,4 +9639,149 @@
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
 }
 
+#if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) || \
+    defined(MBEDTLS_SSL_PROTO_TLS1_1)
+int mbedtls_ssl_get_key_exchange_md_ssl_tls( mbedtls_ssl_context *ssl,
+                                        unsigned char *output,
+                                        unsigned char *data, size_t data_len )
+{
+    int ret = 0;
+    mbedtls_md5_context mbedtls_md5;
+    mbedtls_sha1_context mbedtls_sha1;
+
+    mbedtls_md5_init( &mbedtls_md5 );
+    mbedtls_sha1_init( &mbedtls_sha1 );
+
+    /*
+     * digitally-signed struct {
+     *     opaque md5_hash[16];
+     *     opaque sha_hash[20];
+     * };
+     *
+     * md5_hash
+     *     MD5(ClientHello.random + ServerHello.random
+     *                            + ServerParams);
+     * sha_hash
+     *     SHA(ClientHello.random + ServerHello.random
+     *                            + ServerParams);
+     */
+    if( ( ret = mbedtls_md5_starts_ret( &mbedtls_md5 ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md5_starts_ret", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_md5_update_ret( &mbedtls_md5,
+                                        ssl->handshake->randbytes, 64 ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md5_update_ret", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_md5_update_ret( &mbedtls_md5, data, data_len ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md5_update_ret", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_md5_finish_ret( &mbedtls_md5, output ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md5_finish_ret", ret );
+        goto exit;
+    }
+
+    if( ( ret = mbedtls_sha1_starts_ret( &mbedtls_sha1 ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_sha1_starts_ret", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_sha1_update_ret( &mbedtls_sha1,
+                                         ssl->handshake->randbytes, 64 ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_sha1_update_ret", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_sha1_update_ret( &mbedtls_sha1, data,
+                                         data_len ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_sha1_update_ret", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_sha1_finish_ret( &mbedtls_sha1,
+                                         output + 16 ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_sha1_finish_ret", ret );
+        goto exit;
+    }
+
+exit:
+    mbedtls_md5_free( &mbedtls_md5 );
+    mbedtls_sha1_free( &mbedtls_sha1 );
+
+    if( ret != 0 )
+        mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+                                        MBEDTLS_SSL_ALERT_MSG_INTERNAL_ERROR );
+
+    return( ret );
+
+}
+#endif /* MBEDTLS_SSL_PROTO_SSL3 || MBEDTLS_SSL_PROTO_TLS1 || \
+          MBEDTLS_SSL_PROTO_TLS1_1 */
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
+    defined(MBEDTLS_SSL_PROTO_TLS1_2)
+int mbedtls_ssl_get_key_exchange_md_tls1_2( mbedtls_ssl_context *ssl,
+                                            unsigned char *hash, size_t *hashlen,
+                                            unsigned char *data, size_t data_len,
+                                            mbedtls_md_type_t md_alg )
+{
+    int ret = 0;
+    mbedtls_md_context_t ctx;
+    const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type( md_alg );
+    *hashlen = mbedtls_md_get_size( md_info );
+
+    mbedtls_md_init( &ctx );
+
+    /*
+     * digitally-signed struct {
+     *     opaque client_random[32];
+     *     opaque server_random[32];
+     *     ServerDHParams params;
+     * };
+     */
+    if( ( ret = mbedtls_md_setup( &ctx, md_info, 0 ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md_setup", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_md_starts( &ctx ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md_starts", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_md_update( &ctx, ssl->handshake->randbytes, 64 ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md_update", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_md_update( &ctx, data, data_len ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md_update", ret );
+        goto exit;
+    }
+    if( ( ret = mbedtls_md_finish( &ctx, hash ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md_finish", ret );
+        goto exit;
+    }
+
+exit:
+    mbedtls_md_free( &ctx );
+
+    if( ret != 0 )
+        mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
+                                        MBEDTLS_SSL_ALERT_MSG_INTERNAL_ERROR );
+
+    return( ret );
+}
+#endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 || \
+          MBEDTLS_SSL_PROTO_TLS1_2 */
+
 #endif /* MBEDTLS_SSL_TLS_C */