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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