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/platform_util.h" 44 45 #include <string.h> 46 47 /* 48 * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is 49 * available. Try SHA-256 first, 512 wastes resources since we need to stay 50 * with max 32 bytes of cookie for DTLS 1.0 51 */ 52 #if defined(MBEDTLS_SHA256_C) 53 #define COOKIE_MD MBEDTLS_MD_SHA224 54 #define COOKIE_MD_OUTLEN 32 55 #define COOKIE_HMAC_LEN 28 56 #elif defined(MBEDTLS_SHA512_C) 57 #define COOKIE_MD MBEDTLS_MD_SHA384 58 #define COOKIE_MD_OUTLEN 48 59 #define COOKIE_HMAC_LEN 28 60 #elif defined(MBEDTLS_SHA1_C) 61 #define COOKIE_MD MBEDTLS_MD_SHA1 62 #define COOKIE_MD_OUTLEN 20 63 #define COOKIE_HMAC_LEN 20 64 #else 65 #error "DTLS hello verify needs SHA-1 or SHA-2" 66 #endif 67 68 /* 69 * Cookies are formed of a 4-bytes timestamp (or serial number) and 70 * an HMAC of timestemp and client ID. 71 */ 72 #define COOKIE_LEN ( 4 + COOKIE_HMAC_LEN ) 73 74 void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx ) 75 { 76 mbedtls_md_init( &ctx->hmac_ctx ); 77 #if !defined(MBEDTLS_HAVE_TIME) 78 ctx->serial = 0; 79 #endif 80 ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT; 81 82 #if defined(MBEDTLS_THREADING_C) 83 mbedtls_mutex_init( &ctx->mutex ); 84 #endif 85 } 86 87 void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay ) 88 { 89 ctx->timeout = delay; 90 } 91 92 void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx ) 93 { 94 mbedtls_md_free( &ctx->hmac_ctx ); 95 96 #if defined(MBEDTLS_THREADING_C) 97 mbedtls_mutex_free( &ctx->mutex ); 98 #endif 99 100 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) ); 101 } 102 103 int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx, 104 int (*f_rng)(void *, unsigned char *, size_t), 105 void *p_rng ) 106 { 107 int ret; 108 unsigned char key[COOKIE_MD_OUTLEN]; 109 110 if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 ) 111 return( ret ); 112 113 ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 ); 114 if( ret != 0 ) 115 return( ret ); 116 117 ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) ); 118 if( ret != 0 ) 119 return( ret ); 120 121 mbedtls_platform_zeroize( key, sizeof( key ) ); 122 123 return( 0 ); 124 } 125 126 /* 127 * Generate the HMAC part of a cookie 128 */ 129 static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx, 130 const unsigned char time[4], 131 unsigned char **p, unsigned char *end, 132 const unsigned char *cli_id, size_t cli_id_len ) 133 { 134 unsigned char hmac_out[COOKIE_MD_OUTLEN]; 135 136 if( (size_t)( end - *p ) < COOKIE_HMAC_LEN ) 137 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); 138 139 if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 || 140 mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 || 141 mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 || 142 mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 ) 143 { 144 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); 145 } 146 147 memcpy( *p, hmac_out, COOKIE_HMAC_LEN ); 148 *p += COOKIE_HMAC_LEN; 149 150 return( 0 ); 151 } 152 153 /* 154 * Generate cookie for DTLS ClientHello verification 155 */ 156 int mbedtls_ssl_cookie_write( void *p_ctx, 157 unsigned char **p, unsigned char *end, 158 const unsigned char *cli_id, size_t cli_id_len ) 159 { 160 int ret; 161 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx; 162 unsigned long t; 163 164 if( ctx == NULL || cli_id == NULL ) 165 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 166 167 if( (size_t)( end - *p ) < COOKIE_LEN ) 168 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); 169 170 #if defined(MBEDTLS_HAVE_TIME) 171 t = (unsigned long) mbedtls_time( NULL ); 172 #else 173 t = ctx->serial++; 174 #endif 175 176 (*p)[0] = (unsigned char)( t >> 24 ); 177 (*p)[1] = (unsigned char)( t >> 16 ); 178 (*p)[2] = (unsigned char)( t >> 8 ); 179 (*p)[3] = (unsigned char)( t ); 180 *p += 4; 181 182 #if defined(MBEDTLS_THREADING_C) 183 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) 184 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret ); 185 #endif 186 187 ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4, 188 p, end, cli_id, cli_id_len ); 189 190 #if defined(MBEDTLS_THREADING_C) 191 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 ) 192 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + 193 MBEDTLS_ERR_THREADING_MUTEX_ERROR ); 194 #endif 195 196 return( ret ); 197 } 198 199 /* 200 * Check a cookie 201 */ 202 int mbedtls_ssl_cookie_check( void *p_ctx, 203 const unsigned char *cookie, size_t cookie_len, 204 const unsigned char *cli_id, size_t cli_id_len ) 205 { 206 unsigned char ref_hmac[COOKIE_HMAC_LEN]; 207 int ret = 0; 208 unsigned char *p = ref_hmac; 209 mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx; 210 unsigned long cur_time, cookie_time; 211 212 if( ctx == NULL || cli_id == NULL ) 213 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 214 215 if( cookie_len != COOKIE_LEN ) 216 return( -1 ); 217 218 #if defined(MBEDTLS_THREADING_C) 219 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) 220 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret ); 221 #endif 222 223 if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie, 224 &p, p + sizeof( ref_hmac ), 225 cli_id, cli_id_len ) != 0 ) 226 ret = -1; 227 228 #if defined(MBEDTLS_THREADING_C) 229 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 ) 230 return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + 231 MBEDTLS_ERR_THREADING_MUTEX_ERROR ); 232 #endif 233 234 if( ret != 0 ) 235 return( ret ); 236 237 if( mbedtls_ssl_safer_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 ) 238 return( -1 ); 239 240 #if defined(MBEDTLS_HAVE_TIME) 241 cur_time = (unsigned long) mbedtls_time( NULL ); 242 #else 243 cur_time = ctx->serial; 244 #endif 245 246 cookie_time = ( (unsigned long) cookie[0] << 24 ) | 247 ( (unsigned long) cookie[1] << 16 ) | 248 ( (unsigned long) cookie[2] << 8 ) | 249 ( (unsigned long) cookie[3] ); 250 251 if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout ) 252 return( -1 ); 253 254 return( 0 ); 255 } 256 #endif /* MBEDTLS_SSL_COOKIE_C */ 257