490 lines
13 KiB
C
490 lines
13 KiB
C
/*
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* TLS server tickets callbacks implementation
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*
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* Copyright (C) 2015, ARM Limited, All Rights Reserved
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#if !defined(MBEDTLS_CONFIG_FILE)
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#include "mbedtls/config.h"
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#else
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#include MBEDTLS_CONFIG_FILE
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#endif
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#if defined(MBEDTLS_SSL_TICKET_C)
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#include "mbedtls/ssl_ticket.h"
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#if defined(MBEDTLS_PLATFORM_C)
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#include "mbedtls/platform.h"
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#else
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#include <stdlib.h>
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#define mbedtls_calloc calloc
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#define mbedtls_free free
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#endif
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#include <string.h>
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/* Implementation that should never be optimized out by the compiler */
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static void mbedtls_zeroize( void *v, size_t n ) {
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volatile unsigned char *p = v; while( n-- ) *p++ = 0;
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}
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/*
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* Initialze context
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*/
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void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx )
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{
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memset( ctx, 0, sizeof( mbedtls_ssl_ticket_context ) );
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#if defined(MBEDTLS_THREADING_C)
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mbedtls_mutex_init( &ctx->mutex );
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#endif
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}
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#define MAX_KEY_BYTES 32 /* 256 bits */
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/*
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* Generate/update a key
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*/
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static int ssl_ticket_gen_key( mbedtls_ssl_ticket_context *ctx,
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unsigned char index )
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{
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int ret;
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unsigned char buf[MAX_KEY_BYTES];
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mbedtls_ssl_ticket_key *key = ctx->keys + index;
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#if defined(MBEDTLS_HAVE_TIME)
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key->generation_time = (uint32_t) time( NULL );
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#endif
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if( ( ret = ctx->f_rng( ctx->p_rng, key->name, sizeof( key->name ) ) ) != 0 )
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return( ret );
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if( ( ret = ctx->f_rng( ctx->p_rng, buf, sizeof( buf ) ) ) != 0 )
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return( ret );
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/* With GCM and CCM, same context can encrypt & decrypt */
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ret = mbedtls_cipher_setkey( &key->ctx, buf,
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mbedtls_cipher_get_key_size( &key->ctx ),
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MBEDTLS_ENCRYPT );
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mbedtls_zeroize( buf, sizeof( buf ) );
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return( ret );
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}
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/*
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* Rotate/generate keys if necessary
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*/
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static int ssl_ticket_update_keys( mbedtls_ssl_ticket_context *ctx )
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{
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#if !defined(MBEDTLS_HAVE_TIME)
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((void) ctx);
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#else
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if( ctx->ticket_lifetime != 0 )
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{
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uint32_t current_time = (uint32_t) time( NULL );
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uint32_t key_time = ctx->keys[ctx->active].generation_time;
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if( current_time > key_time &&
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current_time - key_time < ctx->ticket_lifetime )
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{
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return( 0 );
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}
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ctx->active = 1 - ctx->active;
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return( ssl_ticket_gen_key( ctx, ctx->active ) );
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}
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else
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#endif /* MBEDTLS_HAVE_TIME */
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return( 0 );
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}
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/*
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* Setup context for actual use
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*/
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int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx,
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int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
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mbedtls_cipher_type_t cipher,
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uint32_t lifetime )
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{
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int ret;
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const mbedtls_cipher_info_t *cipher_info;
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ctx->f_rng = f_rng;
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ctx->p_rng = p_rng;
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ctx->ticket_lifetime = lifetime;
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cipher_info = mbedtls_cipher_info_from_type( cipher);
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if( cipher_info == NULL )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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if( cipher_info->mode != MBEDTLS_MODE_GCM &&
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cipher_info->mode != MBEDTLS_MODE_CCM )
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{
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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}
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if( cipher_info->key_length > 8 * MAX_KEY_BYTES )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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if( ( ret = mbedtls_cipher_setup( &ctx->keys[0].ctx, cipher_info ) ) != 0 ||
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( ret = mbedtls_cipher_setup( &ctx->keys[1].ctx, cipher_info ) ) != 0 )
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{
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return( ret );
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}
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if( ( ret = ssl_ticket_gen_key( ctx, 0 ) ) != 0 ||
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( ret = ssl_ticket_gen_key( ctx, 1 ) ) != 0 )
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{
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return( ret );
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}
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return( 0 );
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}
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/*
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* Serialize a session in the following format:
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* 0 . n-1 session structure, n = sizeof(mbedtls_ssl_session)
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* n . n+2 peer_cert length = m (0 if no certificate)
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* n+3 . n+2+m peer cert ASN.1
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*/
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static int ssl_save_session( const mbedtls_ssl_session *session,
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unsigned char *buf, size_t buf_len,
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size_t *olen )
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{
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unsigned char *p = buf;
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size_t left = buf_len;
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#if defined(MBEDTLS_X509_CRT_PARSE_C)
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size_t cert_len;
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#endif /* MBEDTLS_X509_CRT_PARSE_C */
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if( left < sizeof( mbedtls_ssl_session ) )
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return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
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memcpy( p, session, sizeof( mbedtls_ssl_session ) );
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p += sizeof( mbedtls_ssl_session );
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left -= sizeof( mbedtls_ssl_session );
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#if defined(MBEDTLS_X509_CRT_PARSE_C)
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if( session->peer_cert == NULL )
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cert_len = 0;
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else
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cert_len = session->peer_cert->raw.len;
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if( left < 3 + cert_len )
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return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
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*p++ = (unsigned char)( cert_len >> 16 & 0xFF );
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*p++ = (unsigned char)( cert_len >> 8 & 0xFF );
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*p++ = (unsigned char)( cert_len & 0xFF );
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if( session->peer_cert != NULL )
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memcpy( p, session->peer_cert->raw.p, cert_len );
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p += cert_len;
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#endif /* MBEDTLS_X509_CRT_PARSE_C */
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*olen = p - buf;
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return( 0 );
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}
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/*
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* Unserialise session, see ssl_save_session()
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*/
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static int ssl_load_session( mbedtls_ssl_session *session,
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const unsigned char *buf, size_t len )
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{
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const unsigned char *p = buf;
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const unsigned char * const end = buf + len;
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#if defined(MBEDTLS_X509_CRT_PARSE_C)
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size_t cert_len;
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#endif /* MBEDTLS_X509_CRT_PARSE_C */
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if( p + sizeof( mbedtls_ssl_session ) > end )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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memcpy( session, p, sizeof( mbedtls_ssl_session ) );
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p += sizeof( mbedtls_ssl_session );
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#if defined(MBEDTLS_X509_CRT_PARSE_C)
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if( p + 3 > end )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2];
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p += 3;
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if( cert_len == 0 )
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{
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session->peer_cert = NULL;
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}
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else
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{
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int ret;
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if( p + cert_len > end )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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session->peer_cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) );
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if( session->peer_cert == NULL )
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return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
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mbedtls_x509_crt_init( session->peer_cert );
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if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert,
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p, cert_len ) ) != 0 )
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{
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mbedtls_x509_crt_free( session->peer_cert );
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mbedtls_free( session->peer_cert );
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session->peer_cert = NULL;
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return( ret );
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}
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p += cert_len;
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}
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#endif /* MBEDTLS_X509_CRT_PARSE_C */
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if( p != end )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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return( 0 );
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}
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/*
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* Create session ticket, with the following structure:
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*
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* struct {
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* opaque key_name[4];
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* opaque iv[12];
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* opaque encrypted_state<0..2^16-1>;
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* opaque tag[16];
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* } ticket;
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*
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* The key_name, iv, and length of encrypted_state are the additional
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* authenticated data.
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*/
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int mbedtls_ssl_ticket_write( void *p_ticket,
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const mbedtls_ssl_session *session,
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unsigned char *start,
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const unsigned char *end,
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size_t *tlen,
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uint32_t *ticket_lifetime )
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{
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int ret;
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mbedtls_ssl_ticket_context *ctx = p_ticket;
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mbedtls_ssl_ticket_key *key;
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unsigned char *key_name = start;
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unsigned char *iv = start + 4;
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unsigned char *state_len_bytes = iv + 12;
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unsigned char *state = state_len_bytes + 2;
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unsigned char *tag;
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size_t clear_len, ciph_len;
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*tlen = 0;
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if( ctx == NULL || ctx->f_rng == NULL )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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/* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
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* in addition to session itself, that will be checked when writing it. */
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if( end - start < 4 + 12 + 2 + 16 )
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return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
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#if defined(MBEDTLS_THREADING_C)
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if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
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return( ret );
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#endif
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if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
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goto cleanup;
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key = &ctx->keys[ctx->active];
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*ticket_lifetime = ctx->ticket_lifetime;
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memcpy( key_name, key->name, 4 );
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if( ( ret = ctx->f_rng( ctx->p_rng, iv, 12 ) ) != 0 )
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goto cleanup;
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/* Dump session state */
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if( ( ret = ssl_save_session( session,
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state, end - state, &clear_len ) ) != 0 ||
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(unsigned long) clear_len > 65535 )
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{
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goto cleanup;
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}
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state_len_bytes[0] = ( clear_len >> 8 ) & 0xff;
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state_len_bytes[1] = ( clear_len ) & 0xff;
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/* Encrypt and authenticate */
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tag = state + clear_len;
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if( ( ret = mbedtls_cipher_auth_encrypt( &key->ctx,
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iv, 12, key_name, 4 + 12 + 2,
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state, clear_len, state, &ciph_len, tag, 16 ) ) != 0 )
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{
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goto cleanup;
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}
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if( ciph_len != clear_len )
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{
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ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
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goto cleanup;
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}
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*tlen = 4 + 12 + 2 + 16 + ciph_len;
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cleanup:
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#if defined(MBEDTLS_THREADING_C)
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if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
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return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
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#endif
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return( ret );
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}
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/*
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* Select key based on name
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*/
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static mbedtls_ssl_ticket_key *ssl_ticket_select_key(
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mbedtls_ssl_ticket_context *ctx,
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const unsigned char name[4] )
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{
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unsigned char i;
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for( i = 0; i < sizeof( ctx->keys ) / sizeof( *ctx->keys ); i++ )
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if( memcmp( name, ctx->keys[i].name, 4 ) == 0 )
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return( &ctx->keys[i] );
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return( NULL );
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}
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/*
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* Load session ticket (see mbedtls_ssl_ticket_write for structure)
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*/
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int mbedtls_ssl_ticket_parse( void *p_ticket,
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mbedtls_ssl_session *session,
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unsigned char *buf,
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size_t len )
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{
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int ret;
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mbedtls_ssl_ticket_context *ctx = p_ticket;
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mbedtls_ssl_ticket_key *key;
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unsigned char *key_name = buf;
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unsigned char *iv = buf + 4;
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unsigned char *enc_len_p = iv + 12;
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unsigned char *ticket = enc_len_p + 2;
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unsigned char *tag;
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size_t enc_len, clear_len;
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if( ctx == NULL || ctx->f_rng == NULL )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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/* See mbedtls_ssl_ticket_write() */
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if( len < 4 + 12 + 2 + 16 )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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#if defined(MBEDTLS_THREADING_C)
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if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
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return( ret );
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#endif
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if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
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goto cleanup;
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enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
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tag = ticket + enc_len;
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if( len != 4 + 12 + 2 + enc_len + 16 )
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{
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ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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goto cleanup;
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}
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/* Select key */
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if( ( key = ssl_ticket_select_key( ctx, key_name ) ) == NULL )
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{
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/* We can't know for sure but this is a likely option unless we're
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* under attack - this is only informative anyway */
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ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
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goto cleanup;
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}
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/* Decrypt and authenticate */
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if( ( ret = mbedtls_cipher_auth_decrypt( &key->ctx, iv, 12,
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key_name, 4 + 12 + 2, ticket, enc_len,
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ticket, &clear_len, tag, 16 ) ) != 0 )
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{
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if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED )
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ret = MBEDTLS_ERR_SSL_INVALID_MAC;
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goto cleanup;
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}
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if( clear_len != enc_len )
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{
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ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
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goto cleanup;
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}
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/* Actually load session */
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if( ( ret = ssl_load_session( session, ticket, clear_len ) ) != 0 )
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goto cleanup;
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#if defined(MBEDTLS_HAVE_TIME)
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{
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/* Check for expiration */
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time_t current_time = time( NULL );
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if( current_time < session->start ||
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(uint32_t)( current_time - session->start ) > ctx->ticket_lifetime )
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{
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ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
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goto cleanup;
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}
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}
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#endif
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cleanup:
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#if defined(MBEDTLS_THREADING_C)
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if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
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return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
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#endif
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return( ret );
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}
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/*
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* Free context
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*/
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void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx )
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{
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mbedtls_cipher_free( &ctx->keys[0].ctx );
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mbedtls_cipher_free( &ctx->keys[1].ctx );
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#if defined(MBEDTLS_THREADING_C)
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mbedtls_mutex_free( &ctx->mutex );
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#endif
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mbedtls_zeroize( ctx, sizeof( mbedtls_ssl_ticket_context ) );
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}
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#endif /* MBEDTLS_SSL_TICKET_C */
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