[398] | 1 | /*
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| 2 | * DTLS cookie callbacks implementation
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| 3 | *
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| 4 | * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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| 5 | * SPDX-License-Identifier: Apache-2.0
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| 6 | *
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| 7 | * Licensed under the Apache License, Version 2.0 (the "License"); you may
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| 8 | * not use this file except in compliance with the License.
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| 9 | * You may obtain a copy of the License at
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| 10 | *
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| 11 | * http://www.apache.org/licenses/LICENSE-2.0
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| 12 | *
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| 13 | * Unless required by applicable law or agreed to in writing, software
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| 14 | * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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| 15 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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| 16 | * See the License for the specific language governing permissions and
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| 17 | * limitations under the License.
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| 18 | *
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| 19 | * This file is part of mbed TLS (https://tls.mbed.org)
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| 20 | */
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| 21 | /*
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| 22 | * These session callbacks use a simple chained list
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| 23 | * to store and retrieve the session information.
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| 24 | */
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| 25 |
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| 26 | #if !defined(MBEDTLS_CONFIG_FILE)
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| 27 | #include "mbedtls/config.h"
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| 28 | #else
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| 29 | #include MBEDTLS_CONFIG_FILE
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| 30 | #endif
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| 31 |
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| 32 | #if defined(MBEDTLS_SSL_COOKIE_C)
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| 33 |
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| 34 | #if defined(MBEDTLS_PLATFORM_C)
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| 35 | #include "mbedtls/platform.h"
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| 36 | #else
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| 37 | #define mbedtls_calloc calloc
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| 38 | #define mbedtls_free free
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| 39 | #endif
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| 40 |
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| 41 | #include "mbedtls/ssl_cookie.h"
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| 42 | #include "mbedtls/ssl_internal.h"
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| 43 | #include "mbedtls/platform_util.h"
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| 44 |
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| 45 | #include <string.h>
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| 46 |
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| 47 | /*
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| 48 | * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is
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| 49 | * available. Try SHA-256 first, 512 wastes resources since we need to stay
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| 50 | * with max 32 bytes of cookie for DTLS 1.0
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| 51 | */
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| 52 | #if defined(MBEDTLS_SHA256_C)
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| 53 | #define COOKIE_MD MBEDTLS_MD_SHA224
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| 54 | #define COOKIE_MD_OUTLEN 32
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| 55 | #define COOKIE_HMAC_LEN 28
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| 56 | #elif defined(MBEDTLS_SHA512_C)
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| 57 | #define COOKIE_MD MBEDTLS_MD_SHA384
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| 58 | #define COOKIE_MD_OUTLEN 48
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| 59 | #define COOKIE_HMAC_LEN 28
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| 60 | #elif defined(MBEDTLS_SHA1_C)
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| 61 | #define COOKIE_MD MBEDTLS_MD_SHA1
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| 62 | #define COOKIE_MD_OUTLEN 20
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| 63 | #define COOKIE_HMAC_LEN 20
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| 64 | #else
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| 65 | #error "DTLS hello verify needs SHA-1 or SHA-2"
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| 66 | #endif
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| 67 |
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| 68 | /*
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| 69 | * Cookies are formed of a 4-bytes timestamp (or serial number) and
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| 70 | * an HMAC of timestemp and client ID.
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| 71 | */
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| 72 | #define COOKIE_LEN ( 4 + COOKIE_HMAC_LEN )
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| 73 |
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| 74 | void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx )
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| 75 | {
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| 76 | mbedtls_md_init( &ctx->hmac_ctx );
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| 77 | #if !defined(MBEDTLS_HAVE_TIME)
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| 78 | ctx->serial = 0;
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| 79 | #endif
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| 80 | ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;
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| 81 |
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| 82 | #if defined(MBEDTLS_THREADING_C)
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| 83 | mbedtls_mutex_init( &ctx->mutex );
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| 84 | #endif
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| 85 | }
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| 86 |
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| 87 | void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay )
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| 88 | {
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| 89 | ctx->timeout = delay;
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| 90 | }
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| 91 |
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| 92 | void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx )
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| 93 | {
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| 94 | mbedtls_md_free( &ctx->hmac_ctx );
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| 95 |
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| 96 | #if defined(MBEDTLS_THREADING_C)
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| 97 | mbedtls_mutex_free( &ctx->mutex );
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| 98 | #endif
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| 99 |
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| 100 | mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) );
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| 101 | }
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| 102 |
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| 103 | int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx,
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| 104 | int (*f_rng)(void *, unsigned char *, size_t),
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| 105 | void *p_rng )
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| 106 | {
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| 107 | int ret;
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| 108 | unsigned char key[COOKIE_MD_OUTLEN];
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| 109 |
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| 110 | if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 )
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| 111 | return( ret );
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| 112 |
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| 113 | ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 );
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| 114 | if( ret != 0 )
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| 115 | return( ret );
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| 116 |
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| 117 | ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) );
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| 118 | if( ret != 0 )
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| 119 | return( ret );
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| 120 |
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| 121 | mbedtls_platform_zeroize( key, sizeof( key ) );
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| 122 |
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| 123 | return( 0 );
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| 124 | }
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| 125 |
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| 126 | /*
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| 127 | * Generate the HMAC part of a cookie
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| 128 | */
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| 129 | static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,
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| 130 | const unsigned char time[4],
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| 131 | unsigned char **p, unsigned char *end,
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| 132 | const unsigned char *cli_id, size_t cli_id_len )
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| 133 | {
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| 134 | unsigned char hmac_out[COOKIE_MD_OUTLEN];
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| 135 |
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| 136 | if( (size_t)( end - *p ) < COOKIE_HMAC_LEN )
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| 137 | return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
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| 138 |
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| 139 | if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 ||
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| 140 | mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
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| 141 | mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 ||
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| 142 | mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 )
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| 143 | {
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| 144 | return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
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| 145 | }
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| 146 |
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| 147 | memcpy( *p, hmac_out, COOKIE_HMAC_LEN );
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| 148 | *p += COOKIE_HMAC_LEN;
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| 149 |
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| 150 | return( 0 );
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| 151 | }
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| 152 |
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| 153 | /*
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| 154 | * Generate cookie for DTLS ClientHello verification
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| 155 | */
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| 156 | int mbedtls_ssl_cookie_write( void *p_ctx,
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| 157 | unsigned char **p, unsigned char *end,
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| 158 | const unsigned char *cli_id, size_t cli_id_len )
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| 159 | {
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| 160 | int ret;
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| 161 | mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
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| 162 | unsigned long t;
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| 163 |
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| 164 | if( ctx == NULL || cli_id == NULL )
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| 165 | return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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| 166 |
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| 167 | if( (size_t)( end - *p ) < COOKIE_LEN )
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| 168 | return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
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| 169 |
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| 170 | #if defined(MBEDTLS_HAVE_TIME)
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| 171 | t = (unsigned long) mbedtls_time( NULL );
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| 172 | #else
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| 173 | t = ctx->serial++;
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| 174 | #endif
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| 175 |
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| 176 | (*p)[0] = (unsigned char)( t >> 24 );
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| 177 | (*p)[1] = (unsigned char)( t >> 16 );
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| 178 | (*p)[2] = (unsigned char)( t >> 8 );
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| 179 | (*p)[3] = (unsigned char)( t );
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| 180 | *p += 4;
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| 181 |
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| 182 | #if defined(MBEDTLS_THREADING_C)
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| 183 | if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
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| 184 | return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );
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| 185 | #endif
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| 186 |
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| 187 | ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4,
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| 188 | p, end, cli_id, cli_id_len );
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| 189 |
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| 190 | #if defined(MBEDTLS_THREADING_C)
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| 191 | if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
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| 192 | return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +
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| 193 | MBEDTLS_ERR_THREADING_MUTEX_ERROR );
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| 194 | #endif
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| 195 |
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| 196 | return( ret );
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| 197 | }
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| 198 |
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| 199 | /*
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| 200 | * Check a cookie
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| 201 | */
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| 202 | int mbedtls_ssl_cookie_check( void *p_ctx,
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| 203 | const unsigned char *cookie, size_t cookie_len,
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| 204 | const unsigned char *cli_id, size_t cli_id_len )
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| 205 | {
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| 206 | unsigned char ref_hmac[COOKIE_HMAC_LEN];
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| 207 | int ret = 0;
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| 208 | unsigned char *p = ref_hmac;
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| 209 | mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
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| 210 | unsigned long cur_time, cookie_time;
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| 211 |
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| 212 | if( ctx == NULL || cli_id == NULL )
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| 213 | return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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| 214 |
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| 215 | if( cookie_len != COOKIE_LEN )
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| 216 | return( -1 );
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| 217 |
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| 218 | #if defined(MBEDTLS_THREADING_C)
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| 219 | if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
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| 220 | return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );
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| 221 | #endif
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| 222 |
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| 223 | if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie,
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| 224 | &p, p + sizeof( ref_hmac ),
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| 225 | cli_id, cli_id_len ) != 0 )
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| 226 | ret = -1;
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| 227 |
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| 228 | #if defined(MBEDTLS_THREADING_C)
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| 229 | if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
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| 230 | return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +
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| 231 | MBEDTLS_ERR_THREADING_MUTEX_ERROR );
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| 232 | #endif
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| 233 |
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| 234 | if( ret != 0 )
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| 235 | return( ret );
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| 236 |
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| 237 | if( mbedtls_ssl_safer_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 )
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| 238 | return( -1 );
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| 239 |
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| 240 | #if defined(MBEDTLS_HAVE_TIME)
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| 241 | cur_time = (unsigned long) mbedtls_time( NULL );
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| 242 | #else
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| 243 | cur_time = ctx->serial;
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| 244 | #endif
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| 245 |
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| 246 | cookie_time = ( (unsigned long) cookie[0] << 24 ) |
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| 247 | ( (unsigned long) cookie[1] << 16 ) |
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| 248 | ( (unsigned long) cookie[2] << 8 ) |
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| 249 | ( (unsigned long) cookie[3] );
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| 250 |
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| 251 | if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout )
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| 252 | return( -1 );
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| 253 |
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| 254 | return( 0 );
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| 255 | }
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| 256 | #endif /* MBEDTLS_SSL_COOKIE_C */
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