256 lines
7 KiB
C
256 lines
7 KiB
C
/*
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* DTLS cookie callbacks implementation
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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* These session callbacks use a simple chained list
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* to store and retrieve the session information.
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*/
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#include "common.h"
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#if defined(MBEDTLS_SSL_COOKIE_C)
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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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#define mbedtls_calloc calloc
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#define mbedtls_free free
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#endif
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#include "mbedtls/ssl_cookie.h"
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#include "ssl_misc.h"
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#include "mbedtls/error.h"
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#include "mbedtls/platform_util.h"
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#include "mbedtls/constant_time.h"
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#include <string.h>
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/*
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* If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is
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* available. Try SHA-256 first, 512 wastes resources
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*/
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#if defined(MBEDTLS_SHA224_C)
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#define COOKIE_MD MBEDTLS_MD_SHA224
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#define COOKIE_MD_OUTLEN 32
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#define COOKIE_HMAC_LEN 28
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#elif defined(MBEDTLS_SHA384_C)
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#define COOKIE_MD MBEDTLS_MD_SHA384
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#define COOKIE_MD_OUTLEN 48
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#define COOKIE_HMAC_LEN 28
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#elif defined(MBEDTLS_SHA1_C)
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#define COOKIE_MD MBEDTLS_MD_SHA1
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#define COOKIE_MD_OUTLEN 20
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#define COOKIE_HMAC_LEN 20
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#else
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#error "DTLS hello verify needs SHA-1 or SHA-2"
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#endif
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/*
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* Cookies are formed of a 4-bytes timestamp (or serial number) and
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* an HMAC of timestemp and client ID.
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*/
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#define COOKIE_LEN ( 4 + COOKIE_HMAC_LEN )
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void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx )
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{
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mbedtls_md_init( &ctx->hmac_ctx );
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#if !defined(MBEDTLS_HAVE_TIME)
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ctx->serial = 0;
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#endif
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ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;
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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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void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay )
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{
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ctx->timeout = delay;
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}
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void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx )
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{
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mbedtls_md_free( &ctx->hmac_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_platform_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) );
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}
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int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng )
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{
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int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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unsigned char key[COOKIE_MD_OUTLEN];
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if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 )
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return( ret );
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ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 );
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if( ret != 0 )
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return( ret );
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ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) );
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if( ret != 0 )
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return( ret );
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mbedtls_platform_zeroize( key, sizeof( key ) );
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return( 0 );
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}
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/*
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* Generate the HMAC part of a cookie
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*/
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static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,
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const unsigned char time[4],
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unsigned char **p, unsigned char *end,
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const unsigned char *cli_id, size_t cli_id_len )
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{
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unsigned char hmac_out[COOKIE_MD_OUTLEN];
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MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_HMAC_LEN );
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if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 ||
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mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
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mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 ||
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mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 )
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{
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return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
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}
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memcpy( *p, hmac_out, COOKIE_HMAC_LEN );
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*p += COOKIE_HMAC_LEN;
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return( 0 );
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}
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/*
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* Generate cookie for DTLS ClientHello verification
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*/
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int mbedtls_ssl_cookie_write( void *p_ctx,
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unsigned char **p, unsigned char *end,
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const unsigned char *cli_id, size_t cli_id_len )
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{
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int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
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unsigned long t;
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if( ctx == NULL || cli_id == NULL )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_LEN );
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#if defined(MBEDTLS_HAVE_TIME)
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t = (unsigned long) mbedtls_time( NULL );
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#else
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t = ctx->serial++;
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#endif
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MBEDTLS_PUT_UINT32_BE(t, *p, 0);
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*p += 4;
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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( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR, ret ) );
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#endif
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ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4,
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p, end, cli_id, cli_id_len );
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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_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR,
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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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* Check a cookie
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*/
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int mbedtls_ssl_cookie_check( void *p_ctx,
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const unsigned char *cookie, size_t cookie_len,
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const unsigned char *cli_id, size_t cli_id_len )
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{
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unsigned char ref_hmac[COOKIE_HMAC_LEN];
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int ret = 0;
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unsigned char *p = ref_hmac;
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mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
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unsigned long cur_time, cookie_time;
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if( ctx == NULL || cli_id == NULL )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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if( cookie_len != COOKIE_LEN )
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return( -1 );
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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( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR, ret ) );
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#endif
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if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie,
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&p, p + sizeof( ref_hmac ),
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cli_id, cli_id_len ) != 0 )
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ret = -1;
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#if defined(MBEDTLS_THREADING_C)
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if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
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{
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ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_SSL_INTERNAL_ERROR,
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MBEDTLS_ERR_THREADING_MUTEX_ERROR );
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}
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#endif
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if( ret != 0 )
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goto exit;
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if( mbedtls_ct_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 )
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{
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ret = -1;
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goto exit;
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}
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#if defined(MBEDTLS_HAVE_TIME)
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cur_time = (unsigned long) mbedtls_time( NULL );
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#else
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cur_time = ctx->serial;
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#endif
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cookie_time = ( (unsigned long) cookie[0] << 24 ) |
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( (unsigned long) cookie[1] << 16 ) |
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( (unsigned long) cookie[2] << 8 ) |
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( (unsigned long) cookie[3] );
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if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout )
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{
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ret = -1;
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goto exit;
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}
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exit:
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mbedtls_platform_zeroize( ref_hmac, sizeof( ref_hmac ) );
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return( ret );
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}
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#endif /* MBEDTLS_SSL_COOKIE_C */
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