1 // SPDX-License-Identifier: Apache-2.0 2 /* 3 * DTLS cookie callbacks implementation 4 * 5 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved 6 * 7 * Licensed under the Apache License, Version 2.0 (the "License"); you may 8 * not use this file except in compliance with the License. 9 * You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 * 19 * This file is part of mbed TLS (https://tls.mbed.org) 20 */ 21 /* 22 * These session callbacks use a simple chained list 23 * to store and retrieve the session information. 24 */ 25 26 #if !defined(MBEDTLS_CONFIG_FILE) 27 #include "mbedtls/config.h" 28 #else 29 #include MBEDTLS_CONFIG_FILE 30 #endif 31 32 #if defined(MBEDTLS_SSL_COOKIE_C) 33 34 #if defined(MBEDTLS_PLATFORM_C) 35 #include "mbedtls/platform.h" 36 #else 37 #define mbedtls_calloc calloc 38 #define mbedtls_free free 39 #endif 40 41 #include "mbedtls/ssl_cookie.h" 42 #include "mbedtls/ssl_internal.h" 43 #include "mbedtls/error.h" 44 #include "mbedtls/platform_util.h" 45 46 #include <string.h> 47 48 /* 49 * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is 50 * available. Try SHA-256 first, 512 wastes resources since we need to stay 51 * with max 32 bytes of cookie for DTLS 1.0 52 */ 53 #if defined(MBEDTLS_SHA256_C) 54 #define COOKIE_MD MBEDTLS_MD_SHA224 55 #define COOKIE_MD_OUTLEN 32 56 #define COOKIE_HMAC_LEN 28 57 #elif defined(MBEDTLS_SHA512_C) 58 #define COOKIE_MD MBEDTLS_MD_SHA384 59 #define COOKIE_MD_OUTLEN 48 60 #define COOKIE_HMAC_LEN 28 61 #elif defined(MBEDTLS_SHA1_C) 62 #define COOKIE_MD MBEDTLS_MD_SHA1 63 #define COOKIE_MD_OUTLEN 20 64 #define COOKIE_HMAC_LEN 20 65 #else 66 #error "DTLS hello verify needs SHA-1 or SHA-2" 67 #endif 68 69 /* 70 * Cookies are formed of a 4-bytes timestamp (or serial number) and 71 * an HMAC of timestemp and client ID. 72 */ 73 #define COOKIE_LEN ( 4 + COOKIE_HMAC_LEN ) 74 75 void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx ) 76 { 77 mbedtls_md_init( &ctx->hmac_ctx ); 78 #if !defined(MBEDTLS_HAVE_TIME) 79 ctx->serial = 0; 80 #endif 81 ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT; 82 83 #if defined(MBEDTLS_THREADING_C) 84 mbedtls_mutex_init( &ctx->mutex ); 85 #endif 86 } 87 88 void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay ) 89 { 90 ctx->timeout = delay; 91 } 92 93 void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx ) 94 { 95 mbedtls_md_free( &ctx->hmac_ctx ); 96 97 #if defined(MBEDTLS_THREADING_C) 98 mbedtls_mutex_free( &ctx->mutex ); 99 #endif 100 101 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) ); 102 } 103 104 int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx, 105 int (*f_rng)(void *, unsigned char *, size_t), 106 void *p_rng ) 107 { 108 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 109 unsigned char key[COOKIE_MD_OUTLEN]; 110 111 if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 ) 112 return( ret ); 113 114 ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 ); 115 if( ret != 0 ) 116 return( ret ); 117 118 ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) ); 119 if( ret != 0 ) 120 return( ret ); 121 122 mbedtls_platform_zeroize( key, sizeof( key ) ); 123 124 return( 0 ); 125 } 126 127 /* 128 * Generate the HMAC part of a cookie 129 */ 130 static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx, 131 const unsigned char time[4], 132 unsigned char **p, unsigned char *end, 133 const unsigned char *cli_id, size_t cli_id_len ) 134 { 135 unsigned char hmac_out[COOKIE_MD_OUTLEN]; 136 137 if( (size_t)( end - *p ) < COOKIE_HMAC_LEN ) 138 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); 139 140 if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 || 141 mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 || 142 mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 || 143 mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 ) 144 { 145 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); 146 } 147 148 memcpy( *p, hmac_out, COOKIE_HMAC_LEN ); 149 *p += COOKIE_HMAC_LEN; 150 151 return( 0 ); 152 } 153 154 /* 155 * Generate cookie for DTLS ClientHello verification 156 */ 157 int mbedtls_ssl_cookie_write( void *p_ctx, 158 unsigned char **p, unsigned char *end, 159 const unsigned char *cli_id, size_t cli_id_len ) 160 { 161 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 162 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx; 163 unsigned long t; 164 165 if( ctx == NULL || cli_id == NULL ) 166 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 167 168 if( (size_t)( end - *p ) < COOKIE_LEN ) 169 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); 170 171 #if defined(MBEDTLS_HAVE_TIME) 172 t = (unsigned long) mbedtls_time( NULL ); 173 #else 174 t = ctx->serial++; 175 #endif 176 177 (*p)[0] = (unsigned char)( t >> 24 ); 178 (*p)[1] = (unsigned char)( t >> 16 ); 179 (*p)[2] = (unsigned char)( t >> 8 ); 180 (*p)[3] = (unsigned char)( t ); 181 *p += 4; 182 183 #if defined(MBEDTLS_THREADING_C) 184 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) 185 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret ); 186 #endif 187 188 ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4, 189 p, end, cli_id, cli_id_len ); 190 191 #if defined(MBEDTLS_THREADING_C) 192 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 ) 193 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + 194 MBEDTLS_ERR_THREADING_MUTEX_ERROR ); 195 #endif 196 197 return( ret ); 198 } 199 200 /* 201 * Check a cookie 202 */ 203 int mbedtls_ssl_cookie_check( void *p_ctx, 204 const unsigned char *cookie, size_t cookie_len, 205 const unsigned char *cli_id, size_t cli_id_len ) 206 { 207 unsigned char ref_hmac[COOKIE_HMAC_LEN]; 208 int ret = 0; 209 unsigned char *p = ref_hmac; 210 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx; 211 unsigned long cur_time, cookie_time; 212 213 if( ctx == NULL || cli_id == NULL ) 214 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 215 216 if( cookie_len != COOKIE_LEN ) 217 return( -1 ); 218 219 #if defined(MBEDTLS_THREADING_C) 220 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) 221 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret ); 222 #endif 223 224 if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie, 225 &p, p + sizeof( ref_hmac ), 226 cli_id, cli_id_len ) != 0 ) 227 ret = -1; 228 229 #if defined(MBEDTLS_THREADING_C) 230 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 ) 231 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + 232 MBEDTLS_ERR_THREADING_MUTEX_ERROR ); 233 #endif 234 235 if( ret != 0 ) 236 return( ret ); 237 238 if( mbedtls_ssl_safer_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 ) 239 return( -1 ); 240 241 #if defined(MBEDTLS_HAVE_TIME) 242 cur_time = (unsigned long) mbedtls_time( NULL ); 243 #else 244 cur_time = ctx->serial; 245 #endif 246 247 cookie_time = ( (unsigned long) cookie[0] << 24 ) | 248 ( (unsigned long) cookie[1] << 16 ) | 249 ( (unsigned long) cookie[2] << 8 ) | 250 ( (unsigned long) cookie[3] ); 251 252 if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout ) 253 return( -1 ); 254 255 return( 0 ); 256 } 257 #endif /* MBEDTLS_SSL_COOKIE_C */ 258