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Posted to commits@mynewt.apache.org by st...@apache.org on 2016/09/28 00:43:45 UTC

[19/51] [abbrv] [partial] incubator-mynewt-core git commit: directory re-org, part 1

http://git-wip-us.apache.org/repos/asf/incubator-mynewt-core/blob/0216c73e/crypto/mbedtls/src/ssl_tls.c
----------------------------------------------------------------------
diff --git a/crypto/mbedtls/src/ssl_tls.c b/crypto/mbedtls/src/ssl_tls.c
new file mode 100644
index 0000000..4424f56
--- /dev/null
+++ b/crypto/mbedtls/src/ssl_tls.c
@@ -0,0 +1,7602 @@
+/*
+ *  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.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+/*
+ *  The SSL 3.0 specification was drafted by Netscape in 1996,
+ *  and became an IETF standard in 1999.
+ *
+ *  http://wp.netscape.com/eng/ssl3/
+ *  http://www.ietf.org/rfc/rfc2246.txt
+ *  http://www.ietf.org/rfc/rfc4346.txt
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_SSL_TLS_C)
+
+#include "mbedtls/debug.h"
+#include "mbedtls/ssl.h"
+#include "mbedtls/ssl_internal.h"
+
+#include <string.h>
+
+#if defined(MBEDTLS_X509_CRT_PARSE_C) && \
+    defined(MBEDTLS_X509_CHECK_EXTENDED_KEY_USAGE)
+#include "mbedtls/oid.h"
+#endif
+
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdlib.h>
+#define mbedtls_calloc    calloc
+#define mbedtls_free       free
+#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;
+}
+
+/* Length of the "epoch" field in the record header */
+static inline size_t ssl_ep_len( const mbedtls_ssl_context *ssl )
+{
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+        return( 2 );
+#else
+    ((void) ssl);
+#endif
+    return( 0 );
+}
+
+/*
+ * Start a timer.
+ * Passing millisecs = 0 cancels a running timer.
+ */
+static void ssl_set_timer( mbedtls_ssl_context *ssl, uint32_t millisecs )
+{
+    if( ssl->f_set_timer == NULL )
+        return;
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "set_timer to %d ms", (int) millisecs ) );
+    ssl->f_set_timer( ssl->p_timer, millisecs / 4, millisecs );
+}
+
+/*
+ * Return -1 is timer is expired, 0 if it isn't.
+ */
+static int ssl_check_timer( mbedtls_ssl_context *ssl )
+{
+    if( ssl->f_get_timer == NULL )
+        return( 0 );
+
+    if( ssl->f_get_timer( ssl->p_timer ) == 2 )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "timer expired" ) );
+        return( -1 );
+    }
+
+    return( 0 );
+}
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+/*
+ * Double the retransmit timeout value, within the allowed range,
+ * returning -1 if the maximum value has already been reached.
+ */
+static int ssl_double_retransmit_timeout( mbedtls_ssl_context *ssl )
+{
+    uint32_t new_timeout;
+
+    if( ssl->handshake->retransmit_timeout >= ssl->conf->hs_timeout_max )
+        return( -1 );
+
+    new_timeout = 2 * ssl->handshake->retransmit_timeout;
+
+    /* Avoid arithmetic overflow and range overflow */
+    if( new_timeout < ssl->handshake->retransmit_timeout ||
+        new_timeout > ssl->conf->hs_timeout_max )
+    {
+        new_timeout = ssl->conf->hs_timeout_max;
+    }
+
+    ssl->handshake->retransmit_timeout = new_timeout;
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "update timeout value to %d millisecs",
+                        ssl->handshake->retransmit_timeout ) );
+
+    return( 0 );
+}
+
+static void ssl_reset_retransmit_timeout( mbedtls_ssl_context *ssl )
+{
+    ssl->handshake->retransmit_timeout = ssl->conf->hs_timeout_min;
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "update timeout value to %d millisecs",
+                        ssl->handshake->retransmit_timeout ) );
+}
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
+/*
+ * Convert max_fragment_length codes to length.
+ * RFC 6066 says:
+ *    enum{
+ *        2^9(1), 2^10(2), 2^11(3), 2^12(4), (255)
+ *    } MaxFragmentLength;
+ * and we add 0 -> extension unused
+ */
+static unsigned int mfl_code_to_length[MBEDTLS_SSL_MAX_FRAG_LEN_INVALID] =
+{
+    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 */
+};
+#endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
+
+#if defined(MBEDTLS_SSL_CLI_C)
+static int ssl_session_copy( mbedtls_ssl_session *dst, const mbedtls_ssl_session *src )
+{
+    mbedtls_ssl_session_free( dst );
+    memcpy( dst, src, sizeof( mbedtls_ssl_session ) );
+
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+    if( src->peer_cert != NULL )
+    {
+        int ret;
+
+        dst->peer_cert = mbedtls_calloc( 1, sizeof(mbedtls_x509_crt) );
+        if( dst->peer_cert == NULL )
+            return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+
+        mbedtls_x509_crt_init( dst->peer_cert );
+
+        if( ( ret = mbedtls_x509_crt_parse_der( dst->peer_cert, src->peer_cert->raw.p,
+                                        src->peer_cert->raw.len ) ) != 0 )
+        {
+            mbedtls_free( dst->peer_cert );
+            dst->peer_cert = NULL;
+            return( ret );
+        }
+    }
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
+
+#if defined(MBEDTLS_SSL_SESSION_TICKETS) && defined(MBEDTLS_SSL_CLI_C)
+    if( src->ticket != NULL )
+    {
+        dst->ticket = mbedtls_calloc( 1, src->ticket_len );
+        if( dst->ticket == NULL )
+            return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+
+        memcpy( dst->ticket, src->ticket, src->ticket_len );
+    }
+#endif /* MBEDTLS_SSL_SESSION_TICKETS && MBEDTLS_SSL_CLI_C */
+
+    return( 0 );
+}
+#endif /* MBEDTLS_SSL_CLI_C */
+
+#if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
+int (*mbedtls_ssl_hw_record_init)( mbedtls_ssl_context *ssl,
+                     const unsigned char *key_enc, const unsigned char *key_dec,
+                     size_t keylen,
+                     const unsigned char *iv_enc,  const unsigned char *iv_dec,
+                     size_t ivlen,
+                     const unsigned char *mac_enc, const unsigned char *mac_dec,
+                     size_t maclen ) = NULL;
+int (*mbedtls_ssl_hw_record_activate)( mbedtls_ssl_context *ssl, int direction) = NULL;
+int (*mbedtls_ssl_hw_record_reset)( mbedtls_ssl_context *ssl ) = NULL;
+int (*mbedtls_ssl_hw_record_write)( mbedtls_ssl_context *ssl ) = NULL;
+int (*mbedtls_ssl_hw_record_read)( mbedtls_ssl_context *ssl ) = NULL;
+int (*mbedtls_ssl_hw_record_finish)( mbedtls_ssl_context *ssl ) = NULL;
+#endif /* MBEDTLS_SSL_HW_RECORD_ACCEL */
+
+/*
+ * Key material generation
+ */
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+static int ssl3_prf( const unsigned char *secret, size_t slen,
+                     const char *label,
+                     const unsigned char *random, size_t rlen,
+                     unsigned char *dstbuf, size_t dlen )
+{
+    size_t i;
+    mbedtls_md5_context md5;
+    mbedtls_sha1_context sha1;
+    unsigned char padding[16];
+    unsigned char sha1sum[20];
+    ((void)label);
+
+    mbedtls_md5_init(  &md5  );
+    mbedtls_sha1_init( &sha1 );
+
+    /*
+     *  SSLv3:
+     *    block =
+     *      MD5( secret + SHA1( 'A'    + secret + random ) ) +
+     *      MD5( secret + SHA1( 'BB'   + secret + random ) ) +
+     *      MD5( secret + SHA1( 'CCC'  + secret + random ) ) +
+     *      ...
+     */
+    for( i = 0; i < dlen / 16; i++ )
+    {
+        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 );
+
+        mbedtls_md5_starts( &md5 );
+        mbedtls_md5_update( &md5, secret, slen );
+        mbedtls_md5_update( &md5, sha1sum, 20 );
+        mbedtls_md5_finish( &md5, dstbuf + i * 16 );
+    }
+
+    mbedtls_md5_free(  &md5  );
+    mbedtls_sha1_free( &sha1 );
+
+    mbedtls_zeroize( padding, sizeof( padding ) );
+    mbedtls_zeroize( sha1sum, sizeof( sha1sum ) );
+
+    return( 0 );
+}
+#endif /* MBEDTLS_SSL_PROTO_SSL3 */
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1)
+static int tls1_prf( const unsigned char *secret, size_t slen,
+                     const char *label,
+                     const unsigned char *random, size_t rlen,
+                     unsigned char *dstbuf, size_t dlen )
+{
+    size_t nb, hs;
+    size_t i, j, k;
+    const unsigned char *S1, *S2;
+    unsigned char tmp[128];
+    unsigned char h_i[20];
+    const mbedtls_md_info_t *md_info;
+    mbedtls_md_context_t md_ctx;
+    int ret;
+
+    mbedtls_md_init( &md_ctx );
+
+    if( sizeof( tmp ) < 20 + strlen( label ) + rlen )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    hs = ( slen + 1 ) / 2;
+    S1 = secret;
+    S2 = secret + slen - hs;
+
+    nb = strlen( label );
+    memcpy( tmp + 20, label, nb );
+    memcpy( tmp + 20 + nb, random, rlen );
+    nb += rlen;
+
+    /*
+     * First compute P_md5(secret,label+random)[0..dlen]
+     */
+    if( ( md_info = mbedtls_md_info_from_type( MBEDTLS_MD_MD5 ) ) == NULL )
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+
+    if( ( ret = mbedtls_md_setup( &md_ctx, md_info, 1 ) ) != 0 )
+        return( ret );
+
+    mbedtls_md_hmac_starts( &md_ctx, S1, hs );
+    mbedtls_md_hmac_update( &md_ctx, tmp + 20, nb );
+    mbedtls_md_hmac_finish( &md_ctx, 4 + tmp );
+
+    for( i = 0; i < dlen; i += 16 )
+    {
+        mbedtls_md_hmac_reset ( &md_ctx );
+        mbedtls_md_hmac_update( &md_ctx, 4 + tmp, 16 + nb );
+        mbedtls_md_hmac_finish( &md_ctx, h_i );
+
+        mbedtls_md_hmac_reset ( &md_ctx );
+        mbedtls_md_hmac_update( &md_ctx, 4 + tmp, 16 );
+        mbedtls_md_hmac_finish( &md_ctx, 4 + tmp );
+
+        k = ( i + 16 > dlen ) ? dlen % 16 : 16;
+
+        for( j = 0; j < k; j++ )
+            dstbuf[i + j]  = h_i[j];
+    }
+
+    mbedtls_md_free( &md_ctx );
+
+    /*
+     * XOR out with P_sha1(secret,label+random)[0..dlen]
+     */
+    if( ( md_info = mbedtls_md_info_from_type( MBEDTLS_MD_SHA1 ) ) == NULL )
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+
+    if( ( ret = mbedtls_md_setup( &md_ctx, md_info, 1 ) ) != 0 )
+        return( ret );
+
+    mbedtls_md_hmac_starts( &md_ctx, S2, hs );
+    mbedtls_md_hmac_update( &md_ctx, tmp + 20, nb );
+    mbedtls_md_hmac_finish( &md_ctx, tmp );
+
+    for( i = 0; i < dlen; i += 20 )
+    {
+        mbedtls_md_hmac_reset ( &md_ctx );
+        mbedtls_md_hmac_update( &md_ctx, tmp, 20 + nb );
+        mbedtls_md_hmac_finish( &md_ctx, h_i );
+
+        mbedtls_md_hmac_reset ( &md_ctx );
+        mbedtls_md_hmac_update( &md_ctx, tmp, 20 );
+        mbedtls_md_hmac_finish( &md_ctx, tmp );
+
+        k = ( i + 20 > dlen ) ? dlen % 20 : 20;
+
+        for( j = 0; j < k; j++ )
+            dstbuf[i + j] = (unsigned char)( dstbuf[i + j] ^ h_i[j] );
+    }
+
+    mbedtls_md_free( &md_ctx );
+
+    mbedtls_zeroize( tmp, sizeof( tmp ) );
+    mbedtls_zeroize( h_i, sizeof( h_i ) );
+
+    return( 0 );
+}
+#endif /* MBEDTLS_SSL_PROTO_TLS1) || MBEDTLS_SSL_PROTO_TLS1_1 */
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
+static int tls_prf_generic( mbedtls_md_type_t md_type,
+                            const unsigned char *secret, size_t slen,
+                            const char *label,
+                            const unsigned char *random, size_t rlen,
+                            unsigned char *dstbuf, size_t dlen )
+{
+    size_t nb;
+    size_t i, j, k, md_len;
+    unsigned char tmp[128];
+    unsigned char h_i[MBEDTLS_MD_MAX_SIZE];
+    const mbedtls_md_info_t *md_info;
+    mbedtls_md_context_t md_ctx;
+    int ret;
+
+    mbedtls_md_init( &md_ctx );
+
+    if( ( md_info = mbedtls_md_info_from_type( md_type ) ) == NULL )
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+
+    md_len = mbedtls_md_get_size( md_info );
+
+    if( sizeof( tmp ) < md_len + strlen( label ) + rlen )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    nb = strlen( label );
+    memcpy( tmp + md_len, label, nb );
+    memcpy( tmp + md_len + nb, random, rlen );
+    nb += rlen;
+
+    /*
+     * Compute P_<hash>(secret, label + random)[0..dlen]
+     */
+    if ( ( ret = mbedtls_md_setup( &md_ctx, md_info, 1 ) ) != 0 )
+        return( ret );
+
+    mbedtls_md_hmac_starts( &md_ctx, secret, slen );
+    mbedtls_md_hmac_update( &md_ctx, tmp + md_len, nb );
+    mbedtls_md_hmac_finish( &md_ctx, tmp );
+
+    for( i = 0; i < dlen; i += md_len )
+    {
+        mbedtls_md_hmac_reset ( &md_ctx );
+        mbedtls_md_hmac_update( &md_ctx, tmp, md_len + nb );
+        mbedtls_md_hmac_finish( &md_ctx, h_i );
+
+        mbedtls_md_hmac_reset ( &md_ctx );
+        mbedtls_md_hmac_update( &md_ctx, tmp, md_len );
+        mbedtls_md_hmac_finish( &md_ctx, tmp );
+
+        k = ( i + md_len > dlen ) ? dlen % md_len : md_len;
+
+        for( j = 0; j < k; j++ )
+            dstbuf[i + j]  = h_i[j];
+    }
+
+    mbedtls_md_free( &md_ctx );
+
+    mbedtls_zeroize( tmp, sizeof( tmp ) );
+    mbedtls_zeroize( h_i, sizeof( h_i ) );
+
+    return( 0 );
+}
+
+#if defined(MBEDTLS_SHA256_C)
+static int tls_prf_sha256( const unsigned char *secret, size_t slen,
+                           const char *label,
+                           const unsigned char *random, size_t rlen,
+                           unsigned char *dstbuf, size_t dlen )
+{
+    return( tls_prf_generic( MBEDTLS_MD_SHA256, secret, slen,
+                             label, random, rlen, dstbuf, dlen ) );
+}
+#endif /* MBEDTLS_SHA256_C */
+
+#if defined(MBEDTLS_SHA512_C)
+static int tls_prf_sha384( const unsigned char *secret, size_t slen,
+                           const char *label,
+                           const unsigned char *random, size_t rlen,
+                           unsigned char *dstbuf, size_t dlen )
+{
+    return( tls_prf_generic( MBEDTLS_MD_SHA384, secret, slen,
+                             label, random, rlen, dstbuf, dlen ) );
+}
+#endif /* MBEDTLS_SHA512_C */
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
+
+static void ssl_update_checksum_start( mbedtls_ssl_context *, const unsigned char *, size_t );
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) || \
+    defined(MBEDTLS_SSL_PROTO_TLS1_1)
+static void ssl_update_checksum_md5sha1( mbedtls_ssl_context *, const unsigned char *, size_t );
+#endif
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+static void ssl_calc_verify_ssl( mbedtls_ssl_context *, unsigned char * );
+static void ssl_calc_finished_ssl( mbedtls_ssl_context *, unsigned char *, int );
+#endif
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1)
+static void ssl_calc_verify_tls( mbedtls_ssl_context *, unsigned char * );
+static void ssl_calc_finished_tls( mbedtls_ssl_context *, unsigned char *, int );
+#endif
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
+#if defined(MBEDTLS_SHA256_C)
+static void ssl_update_checksum_sha256( mbedtls_ssl_context *, const unsigned char *, size_t );
+static void ssl_calc_verify_tls_sha256( mbedtls_ssl_context *,unsigned char * );
+static void ssl_calc_finished_tls_sha256( mbedtls_ssl_context *,unsigned char *, int );
+#endif
+
+#if defined(MBEDTLS_SHA512_C)
+static void ssl_update_checksum_sha384( mbedtls_ssl_context *, const unsigned char *, size_t );
+static void ssl_calc_verify_tls_sha384( mbedtls_ssl_context *, unsigned char * );
+static void ssl_calc_finished_tls_sha384( mbedtls_ssl_context *, unsigned char *, int );
+#endif
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
+
+int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl )
+{
+    int ret = 0;
+    unsigned char tmp[64];
+    unsigned char keyblk[256];
+    unsigned char *key1;
+    unsigned char *key2;
+    unsigned char *mac_enc;
+    unsigned char *mac_dec;
+    size_t iv_copy_len;
+    const mbedtls_cipher_info_t *cipher_info;
+    const mbedtls_md_info_t *md_info;
+
+    mbedtls_ssl_session *session = ssl->session_negotiate;
+    mbedtls_ssl_transform *transform = ssl->transform_negotiate;
+    mbedtls_ssl_handshake_params *handshake = ssl->handshake;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> derive keys" ) );
+
+    cipher_info = mbedtls_cipher_info_from_type( transform->ciphersuite_info->cipher );
+    if( cipher_info == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "cipher info for %d not found",
+                            transform->ciphersuite_info->cipher ) );
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+    }
+
+    md_info = mbedtls_md_info_from_type( transform->ciphersuite_info->mac );
+    if( md_info == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "mbedtls_md info for %d not found",
+                            transform->ciphersuite_info->mac ) );
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+    }
+
+    /*
+     * Set appropriate PRF function and other SSL / TLS / TLS1.2 functions
+     */
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+    if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
+    {
+        handshake->tls_prf = ssl3_prf;
+        handshake->calc_verify = ssl_calc_verify_ssl;
+        handshake->calc_finished = ssl_calc_finished_ssl;
+    }
+    else
+#endif
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1)
+    if( ssl->minor_ver < MBEDTLS_SSL_MINOR_VERSION_3 )
+    {
+        handshake->tls_prf = tls1_prf;
+        handshake->calc_verify = ssl_calc_verify_tls;
+        handshake->calc_finished = ssl_calc_finished_tls;
+    }
+    else
+#endif
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
+#if defined(MBEDTLS_SHA512_C)
+    if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_3 &&
+        transform->ciphersuite_info->mac == MBEDTLS_MD_SHA384 )
+    {
+        handshake->tls_prf = tls_prf_sha384;
+        handshake->calc_verify = ssl_calc_verify_tls_sha384;
+        handshake->calc_finished = ssl_calc_finished_tls_sha384;
+    }
+    else
+#endif
+#if defined(MBEDTLS_SHA256_C)
+    if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_3 )
+    {
+        handshake->tls_prf = tls_prf_sha256;
+        handshake->calc_verify = ssl_calc_verify_tls_sha256;
+        handshake->calc_finished = ssl_calc_finished_tls_sha256;
+    }
+    else
+#endif
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    /*
+     * SSLv3:
+     *   master =
+     *     MD5( premaster + SHA1( 'A'   + premaster + randbytes ) ) +
+     *     MD5( premaster + SHA1( 'BB'  + premaster + randbytes ) ) +
+     *     MD5( premaster + SHA1( 'CCC' + premaster + randbytes ) )
+     *
+     * TLSv1+:
+     *   master = PRF( premaster, "master secret", randbytes )[0..47]
+     */
+    if( handshake->resume == 0 )
+    {
+        MBEDTLS_SSL_DEBUG_BUF( 3, "premaster secret", handshake->premaster,
+                       handshake->pmslen );
+
+#if defined(MBEDTLS_SSL_EXTENDED_MASTER_SECRET)
+        if( ssl->handshake->extended_ms == MBEDTLS_SSL_EXTENDED_MS_ENABLED )
+        {
+            unsigned char session_hash[48];
+            size_t hash_len;
+
+            MBEDTLS_SSL_DEBUG_MSG( 3, ( "using extended master secret" ) );
+
+            ssl->handshake->calc_verify( ssl, session_hash );
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
+            if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_3 )
+            {
+#if defined(MBEDTLS_SHA512_C)
+                if( ssl->transform_negotiate->ciphersuite_info->mac ==
+                    MBEDTLS_MD_SHA384 )
+                {
+                    hash_len = 48;
+                }
+                else
+#endif
+                    hash_len = 32;
+            }
+            else
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
+                hash_len = 36;
+
+            MBEDTLS_SSL_DEBUG_BUF( 3, "session hash", session_hash, hash_len );
+
+            ret = handshake->tls_prf( handshake->premaster, handshake->pmslen,
+                                      "extended master secret",
+                                      session_hash, hash_len,
+                                      session->master, 48 );
+            if( ret != 0 )
+            {
+                MBEDTLS_SSL_DEBUG_RET( 1, "prf", ret );
+                return( ret );
+            }
+
+        }
+        else
+#endif
+        ret = handshake->tls_prf( handshake->premaster, handshake->pmslen,
+                                  "master secret",
+                                  handshake->randbytes, 64,
+                                  session->master, 48 );
+        if( ret != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "prf", ret );
+            return( ret );
+        }
+
+        mbedtls_zeroize( handshake->premaster, sizeof(handshake->premaster) );
+    }
+    else
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "no premaster (session resumed)" ) );
+
+    /*
+     * Swap the client and server random values.
+     */
+    memcpy( tmp, handshake->randbytes, 64 );
+    memcpy( handshake->randbytes, tmp + 32, 32 );
+    memcpy( handshake->randbytes + 32, tmp, 32 );
+    mbedtls_zeroize( tmp, sizeof( tmp ) );
+
+    /*
+     *  SSLv3:
+     *    key block =
+     *      MD5( master + SHA1( 'A'    + master + randbytes ) ) +
+     *      MD5( master + SHA1( 'BB'   + master + randbytes ) ) +
+     *      MD5( master + SHA1( 'CCC'  + master + randbytes ) ) +
+     *      MD5( master + SHA1( 'DDDD' + master + randbytes ) ) +
+     *      ...
+     *
+     *  TLSv1:
+     *    key block = PRF( master, "key expansion", randbytes )
+     */
+    ret = handshake->tls_prf( session->master, 48, "key expansion",
+                              handshake->randbytes, 64, keyblk, 256 );
+    if( ret != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "prf", ret );
+        return( ret );
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "ciphersuite = %s",
+                   mbedtls_ssl_get_ciphersuite_name( session->ciphersuite ) ) );
+    MBEDTLS_SSL_DEBUG_BUF( 3, "master secret", session->master, 48 );
+    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 ) );
+
+    /*
+     * Determine the appropriate key, IV and MAC length.
+     */
+
+    transform->keylen = cipher_info->key_bitlen / 8;
+
+    if( cipher_info->mode == MBEDTLS_MODE_GCM ||
+        cipher_info->mode == MBEDTLS_MODE_CCM )
+    {
+        transform->maclen = 0;
+
+        transform->ivlen = 12;
+        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 );
+    }
+    else
+    {
+        /* Initialize HMAC contexts */
+        if( ( ret = mbedtls_md_setup( &transform->md_ctx_enc, md_info, 1 ) ) != 0 ||
+            ( ret = mbedtls_md_setup( &transform->md_ctx_dec, md_info, 1 ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_md_setup", ret );
+            return( ret );
+        }
+
+        /* Get MAC length */
+        transform->maclen = mbedtls_md_get_size( md_info );
+
+#if defined(MBEDTLS_SSL_TRUNCATED_HMAC)
+        /*
+         * If HMAC is to be truncated, we shall keep the leftmost bytes,
+         * (rfc 6066 page 13 or rfc 2104 section 4),
+         * 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;
+#endif /* MBEDTLS_SSL_TRUNCATED_HMAC */
+
+        /* IV length */
+        transform->ivlen = cipher_info->iv_size;
+
+        /* Minimum length */
+        if( cipher_info->mode == MBEDTLS_MODE_STREAM )
+            transform->minlen = transform->maclen;
+        else
+        {
+            /*
+             * GenericBlockCipher:
+             * 1. if EtM is in use: one block plus MAC
+             *    otherwise: * first multiple of blocklen greater than maclen
+             * 2. IV except for SSL3 and TLS 1.0
+             */
+#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
+            if( session->encrypt_then_mac == MBEDTLS_SSL_ETM_ENABLED )
+            {
+                transform->minlen = transform->maclen
+                                  + cipher_info->block_size;
+            }
+            else
+#endif
+            {
+                transform->minlen = transform->maclen
+                                  + cipher_info->block_size
+                                  - transform->maclen % cipher_info->block_size;
+            }
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1)
+            if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 ||
+                ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_1 )
+                ; /* No need to adjust minlen */
+            else
+#endif
+#if defined(MBEDTLS_SSL_PROTO_TLS1_1) || defined(MBEDTLS_SSL_PROTO_TLS1_2)
+            if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_2 ||
+                ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_3 )
+            {
+                transform->minlen += transform->ivlen;
+            }
+            else
+#endif
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+                return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+            }
+        }
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "keylen: %d, minlen: %d, ivlen: %d, maclen: %d",
+                   transform->keylen, transform->minlen, transform->ivlen,
+                   transform->maclen ) );
+
+    /*
+     * Finally setup the cipher contexts, IVs and MAC secrets.
+     */
+#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;
+
+        mac_enc = keyblk;
+        mac_dec = keyblk + transform->maclen;
+
+        /*
+         * This is not used in TLS v1.1.
+         */
+        iv_copy_len = ( transform->fixed_ivlen ) ?
+                            transform->fixed_ivlen : transform->ivlen;
+        memcpy( transform->iv_enc, key2 + transform->keylen,  iv_copy_len );
+        memcpy( transform->iv_dec, key2 + transform->keylen + iv_copy_len,
+                iv_copy_len );
+    }
+    else
+#endif /* MBEDTLS_SSL_CLI_C */
+#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;
+
+        mac_enc = keyblk + transform->maclen;
+        mac_dec = keyblk;
+
+        /*
+         * This is not used in TLS v1.1.
+         */
+        iv_copy_len = ( transform->fixed_ivlen ) ?
+                            transform->fixed_ivlen : transform->ivlen;
+        memcpy( transform->iv_dec, key1 + transform->keylen,  iv_copy_len );
+        memcpy( transform->iv_enc, key1 + transform->keylen + iv_copy_len,
+                iv_copy_len );
+    }
+    else
+#endif /* MBEDTLS_SSL_SRV_C */
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+    if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
+    {
+        if( transform->maclen > 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 );
+    }
+    else
+#endif /* MBEDTLS_SSL_PROTO_SSL3 */
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
+    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 );
+    }
+    else
+#endif
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+#if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
+    if( mbedtls_ssl_hw_record_init != NULL )
+    {
+        int ret = 0;
+
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "going for mbedtls_ssl_hw_record_init()" ) );
+
+        if( ( ret = mbedtls_ssl_hw_record_init( ssl, key1, key2, transform->keylen,
+                                        transform->iv_enc, transform->iv_dec,
+                                        iv_copy_len,
+                                        mac_enc, mac_dec,
+                                        transform->maclen ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_hw_record_init", ret );
+            return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
+        }
+    }
+#endif /* MBEDTLS_SSL_HW_RECORD_ACCEL */
+
+#if defined(MBEDTLS_SSL_EXPORT_KEYS)
+    if( ssl->conf->f_export_keys != NULL )
+    {
+        ssl->conf->f_export_keys( ssl->conf->p_export_keys,
+                                  session->master, keyblk,
+                                  transform->maclen, transform->keylen,
+                                  iv_copy_len );
+    }
+#endif
+
+    if( ( ret = mbedtls_cipher_setup( &transform->cipher_ctx_enc,
+                                 cipher_info ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setup", ret );
+        return( ret );
+    }
+
+    if( ( ret = mbedtls_cipher_setup( &transform->cipher_ctx_dec,
+                                 cipher_info ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setup", ret );
+        return( ret );
+    }
+
+    if( ( ret = mbedtls_cipher_setkey( &transform->cipher_ctx_enc, key1,
+                               cipher_info->key_bitlen,
+                               MBEDTLS_ENCRYPT ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setkey", ret );
+        return( ret );
+    }
+
+    if( ( ret = mbedtls_cipher_setkey( &transform->cipher_ctx_dec, key2,
+                               cipher_info->key_bitlen,
+                               MBEDTLS_DECRYPT ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setkey", ret );
+        return( ret );
+    }
+
+#if defined(MBEDTLS_CIPHER_MODE_CBC)
+    if( cipher_info->mode == MBEDTLS_MODE_CBC )
+    {
+        if( ( ret = mbedtls_cipher_set_padding_mode( &transform->cipher_ctx_enc,
+                                             MBEDTLS_PADDING_NONE ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_set_padding_mode", ret );
+            return( ret );
+        }
+
+        if( ( ret = mbedtls_cipher_set_padding_mode( &transform->cipher_ctx_dec,
+                                             MBEDTLS_PADDING_NONE ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_set_padding_mode", ret );
+            return( ret );
+        }
+    }
+#endif /* MBEDTLS_CIPHER_MODE_CBC */
+
+    mbedtls_zeroize( keyblk, sizeof( keyblk ) );
+
+#if defined(MBEDTLS_ZLIB_SUPPORT)
+    // Initialize compression
+    //
+    if( session->compression == MBEDTLS_SSL_COMPRESS_DEFLATE )
+    {
+        if( ssl->compress_buf == NULL )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 3, ( "Allocating compression buffer" ) );
+            ssl->compress_buf = mbedtls_calloc( 1, MBEDTLS_SSL_BUFFER_LEN );
+            if( ssl->compress_buf == NULL )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed",
+                                    MBEDTLS_SSL_BUFFER_LEN ) );
+                return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+            }
+        }
+
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "Initializing zlib states" ) );
+
+        memset( &transform->ctx_deflate, 0, sizeof( transform->ctx_deflate ) );
+        memset( &transform->ctx_inflate, 0, sizeof( transform->ctx_inflate ) );
+
+        if( deflateInit( &transform->ctx_deflate,
+                         Z_DEFAULT_COMPRESSION )   != Z_OK ||
+            inflateInit( &transform->ctx_inflate ) != Z_OK )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "Failed to initialize compression" ) );
+            return( MBEDTLS_ERR_SSL_COMPRESSION_FAILED );
+        }
+    }
+#endif /* MBEDTLS_ZLIB_SUPPORT */
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= derive keys" ) );
+
+    return( 0 );
+}
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+void ssl_calc_verify_ssl( mbedtls_ssl_context *ssl, unsigned char hash[36] )
+{
+    mbedtls_md5_context md5;
+    mbedtls_sha1_context sha1;
+    unsigned char pad_1[48];
+    unsigned char pad_2[48];
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> calc verify ssl" ) );
+
+    mbedtls_md5_init( &md5 );
+    mbedtls_sha1_init( &sha1 );
+
+    mbedtls_md5_clone( &md5, &ssl->handshake->fin_md5 );
+    mbedtls_sha1_clone( &sha1, &ssl->handshake->fin_sha1 );
+
+    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_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_sha1_update( &sha1, ssl->session_negotiate->master, 48 );
+    mbedtls_sha1_update( &sha1, pad_1, 40 );
+    mbedtls_sha1_finish( &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_SSL_DEBUG_BUF( 3, "calculated verify result", hash, 36 );
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc verify" ) );
+
+    mbedtls_md5_free(  &md5  );
+    mbedtls_sha1_free( &sha1 );
+
+    return;
+}
+#endif /* MBEDTLS_SSL_PROTO_SSL3 */
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1)
+void ssl_calc_verify_tls( mbedtls_ssl_context *ssl, unsigned char hash[36] )
+{
+    mbedtls_md5_context md5;
+    mbedtls_sha1_context sha1;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> calc verify tls" ) );
+
+    mbedtls_md5_init( &md5 );
+    mbedtls_sha1_init( &sha1 );
+
+    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_SSL_DEBUG_BUF( 3, "calculated verify result", hash, 36 );
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc verify" ) );
+
+    mbedtls_md5_free(  &md5  );
+    mbedtls_sha1_free( &sha1 );
+
+    return;
+}
+#endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 */
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
+#if defined(MBEDTLS_SHA256_C)
+void ssl_calc_verify_tls_sha256( mbedtls_ssl_context *ssl, unsigned char hash[32] )
+{
+    mbedtls_sha256_context sha256;
+
+    mbedtls_sha256_init( &sha256 );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> calc verify sha256" ) );
+
+    mbedtls_sha256_clone( &sha256, &ssl->handshake->fin_sha256 );
+    mbedtls_sha256_finish( &sha256, hash );
+
+    MBEDTLS_SSL_DEBUG_BUF( 3, "calculated verify result", hash, 32 );
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc verify" ) );
+
+    mbedtls_sha256_free( &sha256 );
+
+    return;
+}
+#endif /* MBEDTLS_SHA256_C */
+
+#if defined(MBEDTLS_SHA512_C)
+void ssl_calc_verify_tls_sha384( mbedtls_ssl_context *ssl, unsigned char hash[48] )
+{
+    mbedtls_sha512_context sha512;
+
+    mbedtls_sha512_init( &sha512 );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> calc verify sha384" ) );
+
+    mbedtls_sha512_clone( &sha512, &ssl->handshake->fin_sha512 );
+    mbedtls_sha512_finish( &sha512, hash );
+
+    MBEDTLS_SSL_DEBUG_BUF( 3, "calculated verify result", hash, 48 );
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= calc verify" ) );
+
+    mbedtls_sha512_free( &sha512 );
+
+    return;
+}
+#endif /* MBEDTLS_SHA512_C */
+#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
+
+#if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
+int mbedtls_ssl_psk_derive_premaster( mbedtls_ssl_context *ssl, mbedtls_key_exchange_type_t key_ex )
+{
+    unsigned char *p = ssl->handshake->premaster;
+    unsigned char *end = p + sizeof( ssl->handshake->premaster );
+    const unsigned char *psk = ssl->conf->psk;
+    size_t psk_len = ssl->conf->psk_len;
+
+    /* If the psk callback was called, use its result */
+    if( ssl->handshake->psk != NULL )
+    {
+        psk = ssl->handshake->psk;
+        psk_len = ssl->handshake->psk_len;
+    }
+
+    /*
+     * PMS = struct {
+     *     opaque other_secret<0..2^16-1>;
+     *     opaque psk<0..2^16-1>;
+     * };
+     * with "other_secret" depending on the particular key exchange
+     */
+#if defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED)
+    if( key_ex == MBEDTLS_KEY_EXCHANGE_PSK )
+    {
+        if( end - p < 2 )
+            return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+        *(p++) = (unsigned char)( psk_len >> 8 );
+        *(p++) = (unsigned char)( psk_len      );
+
+        if( end < p || (size_t)( end - p ) < psk_len )
+            return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+        memset( p, 0, psk_len );
+        p += psk_len;
+    }
+    else
+#endif /* MBEDTLS_KEY_EXCHANGE_PSK_ENABLED */
+#if defined(MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED)
+    if( key_ex == MBEDTLS_KEY_EXCHANGE_RSA_PSK )
+    {
+        /*
+         * other_secret already set by the ClientKeyExchange message,
+         * and is 48 bytes long
+         */
+        *p++ = 0;
+        *p++ = 48;
+        p += 48;
+    }
+    else
+#endif /* MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED */
+#if defined(MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED)
+    if( key_ex == MBEDTLS_KEY_EXCHANGE_DHE_PSK )
+    {
+        int ret;
+        size_t len;
+
+        /* Write length only when we know the actual value */
+        if( ( ret = mbedtls_dhm_calc_secret( &ssl->handshake->dhm_ctx,
+                                      p + 2, end - ( p + 2 ), &len,
+                                      ssl->conf->f_rng, ssl->conf->p_rng ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_dhm_calc_secret", ret );
+            return( ret );
+        }
+        *(p++) = (unsigned char)( len >> 8 );
+        *(p++) = (unsigned char)( len );
+        p += len;
+
+        MBEDTLS_SSL_DEBUG_MPI( 3, "DHM: K ", &ssl->handshake->dhm_ctx.K  );
+    }
+    else
+#endif /* MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED */
+#if defined(MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED)
+    if( key_ex == MBEDTLS_KEY_EXCHANGE_ECDHE_PSK )
+    {
+        int ret;
+        size_t zlen;
+
+        if( ( ret = mbedtls_ecdh_calc_secret( &ssl->handshake->ecdh_ctx, &zlen,
+                                       p + 2, end - ( p + 2 ),
+                                       ssl->conf->f_rng, ssl->conf->p_rng ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecdh_calc_secret", ret );
+            return( ret );
+        }
+
+        *(p++) = (unsigned char)( zlen >> 8 );
+        *(p++) = (unsigned char)( zlen      );
+        p += zlen;
+
+        MBEDTLS_SSL_DEBUG_MPI( 3, "ECDH: z", &ssl->handshake->ecdh_ctx.z );
+    }
+    else
+#endif /* MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED */
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    /* opaque psk<0..2^16-1>; */
+    if( end - p < 2 )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    *(p++) = (unsigned char)( psk_len >> 8 );
+    *(p++) = (unsigned char)( psk_len      );
+
+    if( end < p || (size_t)( end - p ) < psk_len )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    memcpy( p, psk, psk_len );
+    p += psk_len;
+
+    ssl->handshake->pmslen = p - ssl->handshake->premaster;
+
+    return( 0 );
+}
+#endif /* MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED */
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+/*
+ * 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 )
+{
+    unsigned char header[11];
+    unsigned char padding[48];
+    int padlen;
+    int md_size = mbedtls_md_get_size( md_ctx->md_info );
+    int md_type = mbedtls_md_get_type( md_ctx->md_info );
+
+    /* Only MD5 and SHA-1 supported */
+    if( md_type == MBEDTLS_MD_MD5 )
+        padlen = 48;
+    else
+        padlen = 40;
+
+    memcpy( header, ctr, 8 );
+    header[ 8] = (unsigned char)  type;
+    header[ 9] = (unsigned char)( len >> 8 );
+    header[10] = (unsigned char)( len      );
+
+    memset( padding, 0x36, 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, header,  11      );
+    mbedtls_md_update( md_ctx, buf,     len     );
+    mbedtls_md_finish( md_ctx, buf +    len     );
+
+    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          );
+}
+#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) ) )
+#define SSL_SOME_MODES_USE_MAC
+#endif
+
+/*
+ * Encryption/decryption functions
+ */
+static int ssl_encrypt_buf( mbedtls_ssl_context *ssl )
+{
+    mbedtls_cipher_mode_t mode;
+    int auth_done = 0;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> encrypt buf" ) );
+
+    if( ssl->session_out == NULL || ssl->transform_out == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    mode = mbedtls_cipher_get_cipher_mode( &ssl->transform_out->cipher_ctx_enc );
+
+    MBEDTLS_SSL_DEBUG_BUF( 4, "before encrypt: output payload",
+                      ssl->out_msg, ssl->out_msglen );
+
+    /*
+     * Add MAC before if needed
+     */
+#if defined(SSL_SOME_MODES_USE_MAC)
+    if( mode == MBEDTLS_MODE_STREAM ||
+        ( mode == MBEDTLS_MODE_CBC
+#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
+          && ssl->session_out->encrypt_then_mac == MBEDTLS_SSL_ETM_DISABLED
+#endif
+        ) )
+    {
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+        if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
+        {
+            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 );
+        }
+        else
+#endif
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
+        defined(MBEDTLS_SSL_PROTO_TLS1_2)
+        if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 )
+        {
+            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_reset( &ssl->transform_out->md_ctx_enc );
+        }
+        else
+#endif
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
+        MBEDTLS_SSL_DEBUG_BUF( 4, "computed mac",
+                       ssl->out_msg + ssl->out_msglen,
+                       ssl->transform_out->maclen );
+
+        ssl->out_msglen += ssl->transform_out->maclen;
+        auth_done++;
+    }
+#endif /* AEAD not the only option */
+
+    /*
+     * Encrypt
+     */
+#if defined(MBEDTLS_ARC4_C) || defined(MBEDTLS_CIPHER_NULL_CIPHER)
+    if( mode == MBEDTLS_MODE_STREAM )
+    {
+        int ret;
+        size_t olen = 0;
+
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "before encrypt: msglen = %d, "
+                            "including %d bytes of padding",
+                       ssl->out_msglen, 0 ) );
+
+        if( ( ret = mbedtls_cipher_crypt( &ssl->transform_out->cipher_ctx_enc,
+                                   ssl->transform_out->iv_enc,
+                                   ssl->transform_out->ivlen,
+                                   ssl->out_msg, ssl->out_msglen,
+                                   ssl->out_msg, &olen ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_crypt", ret );
+            return( ret );
+        }
+
+        if( ssl->out_msglen != olen )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+    }
+    else
+#endif /* MBEDTLS_ARC4_C || MBEDTLS_CIPHER_NULL_CIPHER */
+#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CCM_C)
+    if( mode == MBEDTLS_MODE_GCM ||
+        mode == MBEDTLS_MODE_CCM )
+    {
+        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 &
+                               MBEDTLS_CIPHERSUITE_SHORT_TAG ? 8 : 16;
+
+        memcpy( add_data, ssl->out_ctr, 8 );
+        add_data[8]  = ssl->out_msgtype;
+        mbedtls_ssl_write_version( ssl->major_ver, ssl->minor_ver,
+                           ssl->conf->transport, add_data + 9 );
+        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 );
+
+        /*
+         * Generate IV
+         */
+#if defined(MBEDTLS_SSL_AEAD_RANDOM_IV)
+        ret = ssl->conf->f_rng( ssl->conf->p_rng,
+                ssl->transform_out->iv_enc + ssl->transform_out->fixed_ivlen,
+                ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen );
+        if( ret != 0 )
+            return( ret );
+
+        memcpy( ssl->out_iv,
+                ssl->transform_out->iv_enc + ssl->transform_out->fixed_ivlen,
+                ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen );
+#else
+        if( ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen != 8 )
+        {
+            /* 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 );
+#endif
+
+        MBEDTLS_SSL_DEBUG_BUF( 4, "IV used", ssl->out_iv,
+                ssl->transform_out->ivlen - ssl->transform_out->fixed_ivlen );
+
+        /*
+         * Fix pointer positions and 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;
+
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "before encrypt: msglen = %d, "
+                            "including %d bytes of padding",
+                       ssl->out_msglen, 0 ) );
+
+        /*
+         * Encrypt and authenticate
+         */
+        if( ( ret = mbedtls_cipher_auth_encrypt( &ssl->transform_out->cipher_ctx_enc,
+                                         ssl->transform_out->iv_enc,
+                                         ssl->transform_out->ivlen,
+                                         add_data, 13,
+                                         enc_msg, enc_msglen,
+                                         enc_msg, &olen,
+                                         enc_msg + enc_msglen, taglen ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_auth_encrypt", ret );
+            return( ret );
+        }
+
+        if( olen != enc_msglen )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
+        ssl->out_msglen += taglen;
+        auth_done++;
+
+        MBEDTLS_SSL_DEBUG_BUF( 4, "after encrypt: tag", enc_msg + enc_msglen, taglen );
+    }
+    else
+#endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C */
+#if defined(MBEDTLS_CIPHER_MODE_CBC) &&                                    \
+    ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_CAMELLIA_C) )
+    if( mode == MBEDTLS_MODE_CBC )
+    {
+        int ret;
+        unsigned char *enc_msg;
+        size_t enc_msglen, padlen, olen = 0, i;
+
+        padlen = ssl->transform_out->ivlen - ( ssl->out_msglen + 1 ) %
+                 ssl->transform_out->ivlen;
+        if( padlen == ssl->transform_out->ivlen )
+            padlen = 0;
+
+        for( i = 0; i <= padlen; i++ )
+            ssl->out_msg[ssl->out_msglen + i] = (unsigned char) padlen;
+
+        ssl->out_msglen += padlen + 1;
+
+        enc_msglen = ssl->out_msglen;
+        enc_msg = ssl->out_msg;
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_1) || defined(MBEDTLS_SSL_PROTO_TLS1_2)
+        /*
+         * Prepend per-record IV for block cipher in TLS v1.1 and up as per
+         * Method 1 (6.2.3.2. in RFC4346 and RFC5246)
+         */
+        if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
+        {
+            /*
+             * Generate IV
+             */
+            ret = ssl->conf->f_rng( ssl->conf->p_rng, ssl->transform_out->iv_enc,
+                                  ssl->transform_out->ivlen );
+            if( ret != 0 )
+                return( ret );
+
+            memcpy( ssl->out_iv, ssl->transform_out->iv_enc,
+                    ssl->transform_out->ivlen );
+
+            /*
+             * Fix pointer positions and message length with added IV
+             */
+            enc_msg = ssl->out_msg;
+            enc_msglen = ssl->out_msglen;
+            ssl->out_msglen += ssl->transform_out->ivlen;
+        }
+#endif /* MBEDTLS_SSL_PROTO_TLS1_1 || MBEDTLS_SSL_PROTO_TLS1_2 */
+
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "before encrypt: msglen = %d, "
+                            "including %d bytes of IV and %d bytes of padding",
+                            ssl->out_msglen, ssl->transform_out->ivlen,
+                            padlen + 1 ) );
+
+        if( ( ret = mbedtls_cipher_crypt( &ssl->transform_out->cipher_ctx_enc,
+                                   ssl->transform_out->iv_enc,
+                                   ssl->transform_out->ivlen,
+                                   enc_msg, enc_msglen,
+                                   enc_msg, &olen ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_crypt", ret );
+            return( ret );
+        }
+
+        if( enc_msglen != olen )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1)
+        if( ssl->minor_ver < MBEDTLS_SSL_MINOR_VERSION_2 )
+        {
+            /*
+             * Save IV in SSL3 and TLS1
+             */
+            memcpy( ssl->transform_out->iv_enc,
+                    ssl->transform_out->cipher_ctx_enc.iv,
+                    ssl->transform_out->ivlen );
+        }
+#endif
+
+#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
+        if( auth_done == 0 )
+        {
+            /*
+             * MAC(MAC_write_key, seq_num +
+             *     TLSCipherText.type +
+             *     TLSCipherText.version +
+             *     length_of( (IV +) ENC(...) ) +
+             *     IV + // except for TLS 1.0
+             *     ENC(content + padding + padding_length));
+             */
+            unsigned char pseudo_hdr[13];
+
+            MBEDTLS_SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) );
+
+            memcpy( pseudo_hdr +  0, ssl->out_ctr, 8 );
+            memcpy( pseudo_hdr +  8, ssl->out_hdr, 3 );
+            pseudo_hdr[11] = (unsigned char)( ( ssl->out_msglen >> 8 ) & 0xFF );
+            pseudo_hdr[12] = (unsigned char)( ( ssl->out_msglen      ) & 0xFF );
+
+            MBEDTLS_SSL_DEBUG_BUF( 4, "MAC'd meta-data", pseudo_hdr, 13 );
+
+            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_reset( &ssl->transform_out->md_ctx_enc );
+
+            ssl->out_msglen += ssl->transform_out->maclen;
+            auth_done++;
+        }
+#endif /* MBEDTLS_SSL_ENCRYPT_THEN_MAC */
+    }
+    else
+#endif /* MBEDTLS_CIPHER_MODE_CBC &&
+          ( MBEDTLS_AES_C || MBEDTLS_CAMELLIA_C ) */
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    /* Make extra sure authentication was performed, exactly once */
+    if( auth_done != 1 )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= encrypt buf" ) );
+
+    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)
+    size_t padlen = 0, correct = 1;
+#endif
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> decrypt buf" ) );
+
+    if( ssl->session_in == NULL || ssl->transform_in == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    mode = mbedtls_cipher_get_cipher_mode( &ssl->transform_in->cipher_ctx_dec );
+
+    if( ssl->in_msglen < ssl->transform_in->minlen )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "in_msglen (%d) < minlen (%d)",
+                       ssl->in_msglen, ssl->transform_in->minlen ) );
+        return( MBEDTLS_ERR_SSL_INVALID_MAC );
+    }
+
+#if defined(MBEDTLS_ARC4_C) || defined(MBEDTLS_CIPHER_NULL_CIPHER)
+    if( mode == MBEDTLS_MODE_STREAM )
+    {
+        int ret;
+        size_t olen = 0;
+
+        padlen = 0;
+
+        if( ( ret = mbedtls_cipher_crypt( &ssl->transform_in->cipher_ctx_dec,
+                                   ssl->transform_in->iv_dec,
+                                   ssl->transform_in->ivlen,
+                                   ssl->in_msg, ssl->in_msglen,
+                                   ssl->in_msg, &olen ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_crypt", ret );
+            return( ret );
+        }
+
+        if( ssl->in_msglen != olen )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+    }
+    else
+#endif /* MBEDTLS_ARC4_C || MBEDTLS_CIPHER_NULL_CIPHER */
+#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CCM_C)
+    if( mode == MBEDTLS_MODE_GCM ||
+        mode == MBEDTLS_MODE_CCM )
+    {
+        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 &
+                               MBEDTLS_CIPHERSUITE_SHORT_TAG ? 8 : 16;
+        size_t explicit_iv_len = ssl->transform_in->ivlen -
+                                 ssl->transform_in->fixed_ivlen;
+
+        if( ssl->in_msglen < explicit_iv_len + taglen )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%d) < explicit_iv_len (%d) "
+                                "+ taglen (%d)", ssl->in_msglen,
+                                explicit_iv_len, taglen ) );
+            return( MBEDTLS_ERR_SSL_INVALID_MAC );
+        }
+        dec_msglen = ssl->in_msglen - explicit_iv_len - taglen;
+
+        dec_msg = ssl->in_msg;
+        dec_msg_result = ssl->in_msg;
+        ssl->in_msglen = dec_msglen;
+
+        memcpy( add_data, ssl->in_ctr, 8 );
+        add_data[8]  = ssl->in_msgtype;
+        mbedtls_ssl_write_version( ssl->major_ver, ssl->minor_ver,
+                           ssl->conf->transport, add_data + 9 );
+        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 );
+
+        memcpy( ssl->transform_in->iv_dec + ssl->transform_in->fixed_ivlen,
+                ssl->in_iv,
+                ssl->transform_in->ivlen - ssl->transform_in->fixed_ivlen );
+
+        MBEDTLS_SSL_DEBUG_BUF( 4, "IV used", ssl->transform_in->iv_dec,
+                                     ssl->transform_in->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,
+                                         add_data, 13,
+                                         dec_msg, dec_msglen,
+                                         dec_msg_result, &olen,
+                                         dec_msg + dec_msglen, taglen ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_auth_decrypt", ret );
+
+            if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED )
+                return( MBEDTLS_ERR_SSL_INVALID_MAC );
+
+            return( ret );
+        }
+        auth_done++;
+
+        if( olen != dec_msglen )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+    }
+    else
+#endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C */
+#if defined(MBEDTLS_CIPHER_MODE_CBC) &&                                    \
+    ( defined(MBEDTLS_AES_C) || defined(MBEDTLS_CAMELLIA_C) )
+    if( mode == MBEDTLS_MODE_CBC )
+    {
+        /*
+         * Decrypt and check the padding
+         */
+        int ret;
+        unsigned char *dec_msg;
+        unsigned char *dec_msg_result;
+        size_t dec_msglen;
+        size_t minlen = 0;
+        size_t olen = 0;
+
+        /*
+         * Check immediate ciphertext sanity
+         */
+#if defined(MBEDTLS_SSL_PROTO_TLS1_1) || defined(MBEDTLS_SSL_PROTO_TLS1_2)
+        if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
+            minlen += ssl->transform_in->ivlen;
+#endif
+
+        if( ssl->in_msglen < minlen + ssl->transform_in->ivlen ||
+            ssl->in_msglen < minlen + ssl->transform_in->maclen + 1 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%d) < max( ivlen(%d), maclen (%d) "
+                                "+ 1 ) ( + expl IV )", ssl->in_msglen,
+                                ssl->transform_in->ivlen,
+                                ssl->transform_in->maclen ) );
+            return( MBEDTLS_ERR_SSL_INVALID_MAC );
+        }
+
+        dec_msglen = ssl->in_msglen;
+        dec_msg = ssl->in_msg;
+        dec_msg_result = ssl->in_msg;
+
+        /*
+         * Authenticate before decrypt if enabled
+         */
+#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 pseudo_hdr[13];
+
+            MBEDTLS_SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) );
+
+            dec_msglen -= ssl->transform_in->maclen;
+            ssl->in_msglen -= ssl->transform_in->maclen;
+
+            memcpy( pseudo_hdr +  0, ssl->in_ctr, 8 );
+            memcpy( pseudo_hdr +  8, ssl->in_hdr, 3 );
+            pseudo_hdr[11] = (unsigned char)( ( ssl->in_msglen >> 8 ) & 0xFF );
+            pseudo_hdr[12] = (unsigned char)( ( ssl->in_msglen      ) & 0xFF );
+
+            MBEDTLS_SSL_DEBUG_BUF( 4, "MAC'd meta-data", pseudo_hdr, 13 );
+
+            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_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,
+                                              ssl->transform_in->maclen );
+
+            if( mbedtls_ssl_safer_memcmp( ssl->in_iv + ssl->in_msglen, computed_mac,
+                              ssl->transform_in->maclen ) != 0 )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "message mac does not match" ) );
+
+                return( MBEDTLS_ERR_SSL_INVALID_MAC );
+            }
+            auth_done++;
+        }
+#endif /* MBEDTLS_SSL_ENCRYPT_THEN_MAC */
+
+        /*
+         * Check length sanity
+         */
+        if( ssl->in_msglen % ssl->transform_in->ivlen != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%d) %% ivlen (%d) != 0",
+                           ssl->in_msglen, ssl->transform_in->ivlen ) );
+            return( MBEDTLS_ERR_SSL_INVALID_MAC );
+        }
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_1) || defined(MBEDTLS_SSL_PROTO_TLS1_2)
+        /*
+         * Initialize for prepended IV for block cipher in TLS v1.1 and up
+         */
+        if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
+        {
+            dec_msglen -= ssl->transform_in->ivlen;
+            ssl->in_msglen -= ssl->transform_in->ivlen;
+
+            for( i = 0; i < ssl->transform_in->ivlen; i++ )
+                ssl->transform_in->iv_dec[i] = ssl->in_iv[i];
+        }
+#endif /* MBEDTLS_SSL_PROTO_TLS1_1 || MBEDTLS_SSL_PROTO_TLS1_2 */
+
+        if( ( ret = mbedtls_cipher_crypt( &ssl->transform_in->cipher_ctx_dec,
+                                   ssl->transform_in->iv_dec,
+                                   ssl->transform_in->ivlen,
+                                   dec_msg, dec_msglen,
+                                   dec_msg_result, &olen ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_crypt", ret );
+            return( ret );
+        }
+
+        if( dec_msglen != olen )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1)
+        if( ssl->minor_ver < MBEDTLS_SSL_MINOR_VERSION_2 )
+        {
+            /*
+             * Save IV in SSL3 and TLS1
+             */
+            memcpy( ssl->transform_in->iv_dec,
+                    ssl->transform_in->cipher_ctx_dec.iv,
+                    ssl->transform_in->ivlen );
+        }
+#endif
+
+        padlen = 1 + ssl->in_msg[ssl->in_msglen - 1];
+
+        if( ssl->in_msglen < ssl->transform_in->maclen + padlen &&
+            auth_done == 0 )
+        {
+#if defined(MBEDTLS_SSL_DEBUG_ALL)
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%d) < maclen (%d) + padlen (%d)",
+                        ssl->in_msglen, ssl->transform_in->maclen, padlen ) );
+#endif
+            padlen = 0;
+            correct = 0;
+        }
+
+#if defined(MBEDTLS_SSL_PROTO_SSL3)
+        if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
+        {
+            if( padlen > ssl->transform_in->ivlen )
+            {
+#if defined(MBEDTLS_SSL_DEBUG_ALL)
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad padding length: is %d, "
+                                    "should be no more than %d",
+                               padlen, ssl->transform_in->ivlen ) );
+#endif
+                correct = 0;
+            }
+        }
+        else
+#endif /* MBEDTLS_SSL_PROTO_SSL3 */
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
+    defined(MBEDTLS_SSL_PROTO_TLS1_2)
+        if( ssl->minor_ver > MBEDTLS_SSL_MINOR_VERSION_0 )
+        {
+            /*
+             * TLSv1+: always check the padding up to the first failure
+             * 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;
+
+            /*
+             * Padding is guaranteed to be incorrect if:
+             *   1. padlen >= ssl->in_msglen
+             *
+             *   2. padding_idx >= MBEDTLS_SSL_MAX_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 +
+                                       ssl->transform_in->maclen );
+
+            padding_idx *= correct;
+
+            for( i = 1; i <= 256; i++ )
+            {
+                real_count &= ( i <= padlen );
+                pad_count += real_count *
+                             ( ssl->in_msg[padding_idx + i] == padlen - 1 );
+            }
+
+            correct &= ( pad_count == padlen ); /* Only 1 on correct padding */
+
+#if defined(MBEDTLS_SSL_DEBUG_ALL)
+            if( padlen > 0 && correct == 0 )
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad padding byte detected" ) );
+#endif
+            padlen &= correct * 0x1FF;
+        }
+        else
+#endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 || \
+          MBEDTLS_SSL_PROTO_TLS1_2 */
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
+        ssl->in_msglen -= padlen;
+    }
+    else
+#endif /* MBEDTLS_CIPHER_MODE_CBC &&
+          ( MBEDTLS_AES_C || MBEDTLS_CAMELLIA_C ) */
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    MBEDTLS_SSL_DEBUG_BUF( 4, "raw buffer after decryption",
+                   ssl->in_msg, ssl->in_msglen );
+
+    /*
+     * Authenticate if not done yet.
+     * Compute the MAC regardless of the padding result (RFC4346, CBCTIME).
+     */
+#if defined(SSL_SOME_MODES_USE_MAC)
+    if( auth_done == 0 )
+    {
+        unsigned char tmp[SSL_MAX_MAC_SIZE];
+
+        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 );
+        }
+        else
+#endif /* MBEDTLS_SSL_PROTO_SSL3 */
+#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
+        defined(MBEDTLS_SSL_PROTO_TLS1_2)
+        if( ssl->minor_ver > MBEDTLS_SSL_MINOR_VERSION_0 )
+        {
+            /*
+             * Process MAC and always update for padlen afterwards to make
+             * total time independent of padlen
+             *
+             * extra_run compensates MAC check for 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)
+             */
+            size_t j, extra_run = 0;
+            extra_run = ( 13 + ssl->in_msglen + padlen + 8 ) / 64 -
+                        ( 13 + ssl->in_msglen          + 8 ) / 64;
+
+            extra_run &= correct * 0xFF;
+
+            mbedtls_md_hmac_update( &ssl->transform_in->md_ctx_dec, ssl->in_ctr, 8 );
+            mbedtls_md_hmac_update( &ssl->transform_in->md_ctx_dec, ssl->in_hdr, 3 );
+            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 */
+            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 );
+        }
+        else
+#endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 || \
+              MBEDTLS_SSL_PROTO_TLS1_2 */
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            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( mbedtls_ssl_safer_memcmp( tmp, ssl->in_msg + ssl->in_msglen,
+                         ssl->transform_in->maclen ) != 0 )
+        {
+#if defined(MBEDTLS_SSL_DEBUG_ALL)
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "message mac does not match" ) );
+#endif
+            correct = 0;
+        }
+        auth_done++;
+
+        /*
+         * 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 */
+    if( auth_done != 1 )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    if( ssl->in_msglen == 0 )
+    {
+        ssl->nb_zero++;
+
+        /*
+         * Three or more empty messages may be a DoS attack
+         * (excessive CPU consumption).
+         */
+        if( ssl->nb_zero > 3 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "received four consecutive empty "
+                                "messages, possible DoS attack" ) );
+            return( MBEDTLS_ERR_SSL_INVALID_MAC );
+        }
+    }
+    else
+        ssl->nb_zero = 0;
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    {
+        ; /* in_ctr read from peer, not maintained internally */
+    }
+    else
+#endif
+    {
+        for( i = 8; i > ssl_ep_len( ssl ); i-- )
+            if( ++ssl->in_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, ( "incoming message counter would wrap" ) );
+            return( MBEDTLS_ERR_SSL_COUNTER_WRAPPING );
+        }
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= decrypt buf" ) );
+
+    return( 0 );
+}
+
+#undef MAC_NONE
+#undef MAC_PLAINTEXT
+#undef MAC_CIPHERTEXT
+
+#if defined(MBEDTLS_ZLIB_SUPPORT)
+/*
+ * Compression/decompression functions
+ */
+static int ssl_compress_buf( mbedtls_ssl_context *ssl )
+{
+    int ret;
+    unsigned char *msg_post = ssl->out_msg;
+    size_t len_pre = ssl->out_msglen;
+    unsigned char *msg_pre = ssl->compress_buf;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> compress buf" ) );
+
+    if( len_pre == 0 )
+        return( 0 );
+
+    memcpy( msg_pre, ssl->out_msg, len_pre );
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "before compression: msglen = %d, ",
+                   ssl->out_msglen ) );
+
+    MBEDTLS_SSL_DEBUG_BUF( 4, "before compression: output payload",
+                   ssl->out_msg, ssl->out_msglen );
+
+    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;
+
+    ret = deflate( &ssl->transform_out->ctx_deflate, Z_SYNC_FLUSH );
+    if( ret != Z_OK )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "failed to perform compression (%d)", ret ) );
+        return( MBEDTLS_ERR_SSL_COMPRESSION_FAILED );
+    }
+
+    ssl->out_msglen = MBEDTLS_SSL_BUFFER_LEN -
+                      ssl->transform_out->ctx_deflate.avail_out;
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "after compression: msglen = %d, ",
+                   ssl->out_msglen ) );
+
+    MBEDTLS_SSL_DEBUG_BUF( 4, "after compression: output payload",
+                   ssl->out_msg, ssl->out_msglen );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= compress buf" ) );
+
+    return( 0 );
+}
+
+static int ssl_decompress_buf( mbedtls_ssl_context *ssl )
+{
+    int ret;
+    unsigned char *msg_post = ssl->in_msg;
+    size_t len_pre = ssl->in_msglen;
+    unsigned char *msg_pre = ssl->compress_buf;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> decompress buf" ) );
+
+    if( len_pre == 0 )
+        return( 0 );
+
+    memcpy( msg_pre, ssl->in_msg, len_pre );
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "before decompression: msglen = %d, ",
+                   ssl->in_msglen ) );
+
+    MBEDTLS_SSL_DEBUG_BUF( 4, "before decompression: input payload",
+                   ssl->in_msg, ssl->in_msglen );
+
+    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;
+
+    ret = inflate( &ssl->transform_in->ctx_inflate, Z_SYNC_FLUSH );
+    if( ret != Z_OK )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "failed to perform decompression (%d)", ret ) );
+        return( MBEDTLS_ERR_SSL_COMPRESSION_FAILED );
+    }
+
+    ssl->in_msglen = MBEDTLS_SSL_MAX_CONTENT_LEN -
+                     ssl->transform_in->ctx_inflate.avail_out;
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "after decompression: msglen = %d, ",
+                   ssl->in_msglen ) );
+
+    MBEDTLS_SSL_DEBUG_BUF( 4, "after decompression: input payload",
+                   ssl->in_msg, ssl->in_msglen );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= decompress buf" ) );
+
+    return( 0 );
+}
+#endif /* MBEDTLS_ZLIB_SUPPORT */
+
+#if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_RENEGOTIATION)
+static int ssl_write_hello_request( mbedtls_ssl_context *ssl );
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+static int ssl_resend_hello_request( mbedtls_ssl_context *ssl )
+{
+    /* If renegotiation is not enforced, retransmit until we would reach max
+     * timeout if we were using the usual handshake doubling scheme */
+    if( ssl->conf->renego_max_records < 0 )
+    {
+        uint32_t ratio = ssl->conf->hs_timeout_max / ssl->conf->hs_timeout_min + 1;
+        unsigned char doublings = 1;
+
+        while( ratio != 0 )
+        {
+            ++doublings;
+            ratio >>= 1;
+        }
+
+        if( ++ssl->renego_records_seen > doublings )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "no longer retransmitting hello request" ) );
+            return( 0 );
+        }
+    }
+
+    return( ssl_write_hello_request( ssl ) );
+}
+#endif
+#endif /* MBEDTLS_SSL_SRV_C && MBEDTLS_SSL_RENEGOTIATION */
+
+/*
+ * Fill the input message buffer by appending data to it.
+ * The amount of data already fetched is in ssl->in_left.
+ *
+ * If we return 0, is it guaranteed that (at least) nb_want bytes are
+ * available (from this read and/or a previous one). Otherwise, an error code
+ * is returned (possibly EOF or WANT_READ).
+ *
+ * With stream transport (TLS) on success ssl->in_left == nb_want, but
+ * with datagram transport (DTLS) on success ssl->in_left >= nb_want,
+ * since we always read a whole datagram at once.
+ *
+ * For DTLS, it is up to the caller to set ssl->next_record_offset when
+ * they're done reading a record.
+ */
+int mbedtls_ssl_fetch_input( mbedtls_ssl_context *ssl, size_t nb_want )
+{
+    int ret;
+    size_t len;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> fetch input" ) );
+
+    if( ssl->f_recv == NULL && ssl->f_recv_timeout == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "Bad usage of mbedtls_ssl_set_bio() "
+                            "or mbedtls_ssl_set_bio()" ) );
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+    }
+
+    if( nb_want > MBEDTLS_SSL_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 );
+    }
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    {
+        uint32_t timeout;
+
+        /* Just to be sure */
+        if( ssl->f_set_timer == NULL || ssl->f_get_timer == NULL )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "You must use "
+                        "mbedtls_ssl_set_timer_cb() for DTLS" ) );
+            return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+        }
+
+        /*
+         * The point is, we need to always read a full datagram at once, so we
+         * sometimes read more then requested, and handle the additional data.
+         * It could be the rest of the current record (while fetching the
+         * header) and/or some other records in the same datagram.
+         */
+
+        /*
+         * Move to the next record in the already read datagram if applicable
+         */
+        if( ssl->next_record_offset != 0 )
+        {
+            if( ssl->in_left < ssl->next_record_offset )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+                return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+            }
+
+            ssl->in_left -= ssl->next_record_offset;
+
+            if( ssl->in_left != 0 )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "next record in same datagram, offset: %d",
+                                    ssl->next_record_offset ) );
+                memmove( ssl->in_hdr,
+                         ssl->in_hdr + ssl->next_record_offset,
+                         ssl->in_left );
+            }
+
+            ssl->next_record_offset = 0;
+        }
+
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "in_left: %d, nb_want: %d",
+                       ssl->in_left, nb_want ) );
+
+        /*
+         * Done if we already have enough data.
+         */
+        if( nb_want <= ssl->in_left)
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= fetch input" ) );
+            return( 0 );
+        }
+
+        /*
+         * A record can't be split accross datagrams. If we need to read but
+         * are not at the beginning of a new record, the caller did something
+         * wrong.
+         */
+        if( ssl->in_left != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
+        /*
+         * Don't even try to read if time's out already.
+         * This avoids by-passing the timer when repeatedly receiving messages
+         * that will end up being dropped.
+         */
+        if( ssl_check_timer( ssl ) != 0 )
+            ret = MBEDTLS_ERR_SSL_TIMEOUT;
+        else
+        {
+            len = MBEDTLS_SSL_BUFFER_LEN - ( ssl->in_hdr - ssl->in_buf );
+
+            if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER )
+                timeout = ssl->handshake->retransmit_timeout;
+            else
+                timeout = ssl->conf->read_timeout;
+
+            MBEDTLS_SSL_DEBUG_MSG( 3, ( "f_recv_timeout: %u ms", timeout ) );
+
+            if( ssl->f_recv_timeout != NULL )
+                ret = ssl->f_recv_timeout( ssl->p_bio, ssl->in_hdr, len,
+                                                                    timeout );
+            else
+                ret = ssl->f_recv( ssl->p_bio, ssl->in_hdr, len );
+
+            MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_recv(_timeout)", ret );
+
+            if( ret == 0 )
+                return( MBEDTLS_ERR_SSL_CONN_EOF );
+        }
+
+        if( ret == MBEDTLS_ERR_SSL_TIMEOUT )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "timeout" ) );
+            ssl_set_timer( ssl, 0 );
+
+            if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER )
+            {
+                if( ssl_double_retransmit_timeout( ssl ) != 0 )
+                {
+                    MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake timeout" ) );
+                    return( MBEDTLS_ERR_SSL_TIMEOUT );
+                }
+
+                if( ( ret = mbedtls_ssl_resend( ssl ) ) != 0 )
+                {
+                    MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_resend", ret );
+                    return( ret );
+                }
+
+                return( MBEDTLS_ERR_SSL_WANT_READ );
+            }
+#if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_RENEGOTIATION)
+            else if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER &&
+                     ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_PENDING )
+            {
+                if( ( ret = ssl_resend_hello_request( ssl ) ) != 0 )
+                {
+                    MBEDTLS_SSL_DEBUG_RET( 1, "ssl_resend_hello_request", ret );
+                    return( ret );
+                }
+
+                return( MBEDTLS_ERR_SSL_WANT_READ );
+            }
+#endif /* MBEDTLS_SSL_SRV_C && MBEDTLS_SSL_RENEGOTIATION */
+        }
+
+        if( ret < 0 )
+            return( ret );
+
+        ssl->in_left = ret;
+    }
+    else
+#endif
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "in_left: %d, nb_want: %d",
+                       ssl->in_left, nb_want ) );
+
+        while( ssl->in_left < nb_want )
+        {
+            len = nb_want - ssl->in_left;
+
+            if( ssl_check_timer( ssl ) != 0 )
+                ret = MBEDTLS_ERR_SSL_TIMEOUT;
+            else
+            {
+                if( ssl->f_recv_timeout != NULL )
+                {
+                    ret = ssl->f_recv_timeout( ssl->p_bio,
+                                               ssl->in_hdr + ssl->in_left, len,
+                                               ssl->conf->read_timeout );
+                }
+                else
+                {
+                    ret = ssl->f_recv( ssl->p_bio,
+                                       ssl->in_hdr + ssl->in_left, len );
+                }
+            }
+
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "in_left: %d, nb_want: %d",
+                                        ssl->in_left, nb_want ) );
+            MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_recv(_timeout)", ret );
+
+            if( ret == 0 )
+                return( MBEDTLS_ERR_SSL_CONN_EOF );
+
+            if( ret < 0 )
+                return( ret );
+
+            ssl->in_left += ret;
+        }
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= fetch input" ) );
+
+    return( 0 );
+}
+
+/*
+ * Flush any data not yet written
+ */
+int mbedtls_ssl_flush_output( mbedtls_ssl_context *ssl )
+{
+    int ret;
+    unsigned char *buf, i;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> flush output" ) );
+
+    if( ssl->f_send == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "Bad usage of mbedtls_ssl_set_bio() "
+                            "or mbedtls_ssl_set_bio()" ) );
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+    }
+
+    /* Avoid incrementing counter if data is flushed */
+    if( ssl->out_left == 0 )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= flush output" ) );
+        return( 0 );
+    }
+
+    while( ssl->out_left > 0 )
+    {
+        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;
+        ret = ssl->f_send( ssl->p_bio, buf, ssl->out_left );
+
+        MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_send", ret );
+
+        if( ret <= 0 )
+            return( ret );
+
+        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 ) )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "outgoing message counter would wrap" ) );
+        return( MBEDTLS_ERR_SSL_COUNTER_WRAPPING );
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= flush output" ) );
+
+    return( 0 );
+}
+
+/*
+ * Functions to handle the DTLS retransmission state machine
+ */
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+/*
+ * Append current handshake message to current outgoing flight
+ */
+static int ssl_flight_append( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_flight_item *msg;
+
+    /* Allocate space for current message */
+    if( ( msg = mbedtls_calloc( 1, sizeof(  mbedtls_ssl_flight_item ) ) ) == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc %d bytes failed",
+                            sizeof( mbedtls_ssl_flight_item ) ) );
+        return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+    }
+
+    if( ( msg->p = mbedtls_calloc( 1, ssl->out_msglen ) ) == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc %d bytes failed", ssl->out_msglen ) );
+        mbedtls_free( msg );
+        return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+    }
+
+    /* Copy current handshake message with headers */
+    memcpy( msg->p, ssl->out_msg, ssl->out_msglen );
+    msg->len = ssl->out_msglen;
+    msg->type = ssl->out_msgtype;
+    msg->next = NULL;
+
+    /* Append to the current flight */
+    if( ssl->handshake->flight == NULL )
+        ssl->handshake->flight = msg;
+    else
+    {
+        mbedtls_ssl_flight_item *cur = ssl->handshake->flight;
+        while( cur->next != NULL )
+            cur = cur->next;
+        cur->next = msg;
+    }
+
+    return( 0 );
+}
+
+/*
+ * Free the current flight of handshake messages
+ */
+static void ssl_flight_free( mbedtls_ssl_flight_item *flight )
+{
+    mbedtls_ssl_flight_item *cur = flight;
+    mbedtls_ssl_flight_item *next;
+
+    while( cur != NULL )
+    {
+        next = cur->next;
+
+        mbedtls_free( cur->p );
+        mbedtls_free( cur );
+
+        cur = next;
+    }
+}
+
+#if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY)
+static void ssl_dtls_replay_reset( mbedtls_ssl_context *ssl );
+#endif
+
+/*
+ * Swap transform_out and out_ctr with the alternative ones
+ */
+static void ssl_swap_epochs( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_transform *tmp_transform;
+    unsigned char tmp_out_ctr[8];
+
+    if( ssl->transform_out == ssl->handshake->alt_transform_out )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 3, ( "skip swap epochs" ) );
+        return;
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 3, ( "swap epochs" ) );
+
+    /* Swap transforms */
+    tmp_transform                     = ssl->transform_out;
+    ssl->transform_out                = ssl->handshake->alt_transform_out;
+    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( ssl->handshake->alt_out_ctr, tmp_out_ctr,                 8 );
+
+    /* Adjust to the newly activated transform */
+    if( ssl->transform_out != NULL &&
+     

<TRUNCATED>