1 /* 2 * TLS server tickets callbacks implementation 3 * 4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved 5 * SPDX-License-Identifier: Apache-2.0 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 #if !defined(MBEDTLS_CONFIG_FILE) 23 #include "mbedtls/config.h" 24 #else 25 #include MBEDTLS_CONFIG_FILE 26 #endif 27 28 #if defined(MBEDTLS_SSL_TICKET_C) 29 30 #if defined(MBEDTLS_PLATFORM_C) 31 #include "mbedtls/platform.h" 32 #else 33 #include <stdlib.h> 34 #define mbedtls_calloc calloc 35 #define mbedtls_free free 36 #endif 37 38 #include "mbedtls/ssl_ticket.h" 39 40 #include <string.h> 41 42 /* Implementation that should never be optimized out by the compiler */ 43 static void mbedtls_zeroize( void *v, size_t n ) { 44 volatile unsigned char *p = v; while( n-- ) *p++ = 0; 45 } 46 47 /* 48 * Initialze context 49 */ 50 void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx ) 51 { 52 memset( ctx, 0, sizeof( mbedtls_ssl_ticket_context ) ); 53 54 #if defined(MBEDTLS_THREADING_C) 55 mbedtls_mutex_init( &ctx->mutex ); 56 #endif 57 } 58 59 #define MAX_KEY_BYTES 32 /* 256 bits */ 60 61 /* 62 * Generate/update a key 63 */ 64 static int ssl_ticket_gen_key( mbedtls_ssl_ticket_context *ctx, 65 unsigned char index ) 66 { 67 int ret; 68 unsigned char buf[MAX_KEY_BYTES]; 69 mbedtls_ssl_ticket_key *key = ctx->keys + index; 70 71 #if defined(MBEDTLS_HAVE_TIME) 72 key->generation_time = (uint32_t) mbedtls_time( NULL ); 73 #endif 74 75 if( ( ret = ctx->f_rng( ctx->p_rng, key->name, sizeof( key->name ) ) ) != 0 ) 76 return( ret ); 77 78 if( ( ret = ctx->f_rng( ctx->p_rng, buf, sizeof( buf ) ) ) != 0 ) 79 return( ret ); 80 81 /* With GCM and CCM, same context can encrypt & decrypt */ 82 ret = mbedtls_cipher_setkey( &key->ctx, buf, 83 mbedtls_cipher_get_key_bitlen( &key->ctx ), 84 MBEDTLS_ENCRYPT ); 85 86 mbedtls_zeroize( buf, sizeof( buf ) ); 87 88 return( ret ); 89 } 90 91 /* 92 * Rotate/generate keys if necessary 93 */ 94 static int ssl_ticket_update_keys( mbedtls_ssl_ticket_context *ctx ) 95 { 96 #if !defined(MBEDTLS_HAVE_TIME) 97 ((void) ctx); 98 #else 99 if( ctx->ticket_lifetime != 0 ) 100 { 101 uint32_t current_time = (uint32_t) mbedtls_time( NULL ); 102 uint32_t key_time = ctx->keys[ctx->active].generation_time; 103 104 if( current_time > key_time && 105 current_time - key_time < ctx->ticket_lifetime ) 106 { 107 return( 0 ); 108 } 109 110 ctx->active = 1 - ctx->active; 111 112 return( ssl_ticket_gen_key( ctx, ctx->active ) ); 113 } 114 else 115 #endif /* MBEDTLS_HAVE_TIME */ 116 return( 0 ); 117 } 118 119 /* 120 * Setup context for actual use 121 */ 122 int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx, 123 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, 124 mbedtls_cipher_type_t cipher, 125 uint32_t lifetime ) 126 { 127 int ret; 128 const mbedtls_cipher_info_t *cipher_info; 129 130 ctx->f_rng = f_rng; 131 ctx->p_rng = p_rng; 132 133 ctx->ticket_lifetime = lifetime; 134 135 cipher_info = mbedtls_cipher_info_from_type( cipher); 136 if( cipher_info == NULL ) 137 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 138 139 if( cipher_info->mode != MBEDTLS_MODE_GCM && 140 cipher_info->mode != MBEDTLS_MODE_CCM ) 141 { 142 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 143 } 144 145 if( cipher_info->key_bitlen > 8 * MAX_KEY_BYTES ) 146 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 147 148 if( ( ret = mbedtls_cipher_setup( &ctx->keys[0].ctx, cipher_info ) ) != 0 || 149 ( ret = mbedtls_cipher_setup( &ctx->keys[1].ctx, cipher_info ) ) != 0 ) 150 { 151 return( ret ); 152 } 153 154 if( ( ret = ssl_ticket_gen_key( ctx, 0 ) ) != 0 || 155 ( ret = ssl_ticket_gen_key( ctx, 1 ) ) != 0 ) 156 { 157 return( ret ); 158 } 159 160 return( 0 ); 161 } 162 163 /* 164 * Serialize a session in the following format: 165 * 0 . n-1 session structure, n = sizeof(mbedtls_ssl_session) 166 * n . n+2 peer_cert length = m (0 if no certificate) 167 * n+3 . n+2+m peer cert ASN.1 168 */ 169 static int ssl_save_session( const mbedtls_ssl_session *session, 170 unsigned char *buf, size_t buf_len, 171 size_t *olen ) 172 { 173 unsigned char *p = buf; 174 size_t left = buf_len; 175 #if defined(MBEDTLS_X509_CRT_PARSE_C) 176 size_t cert_len; 177 #endif /* MBEDTLS_X509_CRT_PARSE_C */ 178 179 if( left < sizeof( mbedtls_ssl_session ) ) 180 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); 181 182 memcpy( p, session, sizeof( mbedtls_ssl_session ) ); 183 p += sizeof( mbedtls_ssl_session ); 184 left -= sizeof( mbedtls_ssl_session ); 185 186 #if defined(MBEDTLS_X509_CRT_PARSE_C) 187 if( session->peer_cert == NULL ) 188 cert_len = 0; 189 else 190 cert_len = session->peer_cert->raw.len; 191 192 if( left < 3 + cert_len ) 193 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); 194 195 *p++ = (unsigned char)( cert_len >> 16 & 0xFF ); 196 *p++ = (unsigned char)( cert_len >> 8 & 0xFF ); 197 *p++ = (unsigned char)( cert_len & 0xFF ); 198 199 if( session->peer_cert != NULL ) 200 memcpy( p, session->peer_cert->raw.p, cert_len ); 201 202 p += cert_len; 203 #endif /* MBEDTLS_X509_CRT_PARSE_C */ 204 205 *olen = p - buf; 206 207 return( 0 ); 208 } 209 210 /* 211 * Unserialise session, see ssl_save_session() 212 */ 213 static int ssl_load_session( mbedtls_ssl_session *session, 214 const unsigned char *buf, size_t len ) 215 { 216 const unsigned char *p = buf; 217 const unsigned char * const end = buf + len; 218 #if defined(MBEDTLS_X509_CRT_PARSE_C) 219 size_t cert_len; 220 #endif /* MBEDTLS_X509_CRT_PARSE_C */ 221 222 if( p + sizeof( mbedtls_ssl_session ) > end ) 223 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 224 225 memcpy( session, p, sizeof( mbedtls_ssl_session ) ); 226 p += sizeof( mbedtls_ssl_session ); 227 228 #if defined(MBEDTLS_X509_CRT_PARSE_C) 229 if( p + 3 > end ) 230 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 231 232 cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2]; 233 p += 3; 234 235 if( cert_len == 0 ) 236 { 237 session->peer_cert = NULL; 238 } 239 else 240 { 241 int ret; 242 243 if( p + cert_len > end ) 244 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 245 246 session->peer_cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) ); 247 248 if( session->peer_cert == NULL ) 249 return( MBEDTLS_ERR_SSL_ALLOC_FAILED ); 250 251 mbedtls_x509_crt_init( session->peer_cert ); 252 253 if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert, 254 p, cert_len ) ) != 0 ) 255 { 256 mbedtls_x509_crt_free( session->peer_cert ); 257 mbedtls_free( session->peer_cert ); 258 session->peer_cert = NULL; 259 return( ret ); 260 } 261 262 p += cert_len; 263 } 264 #endif /* MBEDTLS_X509_CRT_PARSE_C */ 265 266 if( p != end ) 267 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 268 269 return( 0 ); 270 } 271 272 /* 273 * Create session ticket, with the following structure: 274 * 275 * struct { 276 * opaque key_name[4]; 277 * opaque iv[12]; 278 * opaque encrypted_state<0..2^16-1>; 279 * opaque tag[16]; 280 * } ticket; 281 * 282 * The key_name, iv, and length of encrypted_state are the additional 283 * authenticated data. 284 */ 285 int mbedtls_ssl_ticket_write( void *p_ticket, 286 const mbedtls_ssl_session *session, 287 unsigned char *start, 288 const unsigned char *end, 289 size_t *tlen, 290 uint32_t *ticket_lifetime ) 291 { 292 int ret; 293 mbedtls_ssl_ticket_context *ctx = p_ticket; 294 mbedtls_ssl_ticket_key *key; 295 unsigned char *key_name = start; 296 unsigned char *iv = start + 4; 297 unsigned char *state_len_bytes = iv + 12; 298 unsigned char *state = state_len_bytes + 2; 299 unsigned char *tag; 300 size_t clear_len, ciph_len; 301 302 *tlen = 0; 303 304 if( ctx == NULL || ctx->f_rng == NULL ) 305 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 306 307 /* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag, 308 * in addition to session itself, that will be checked when writing it. */ 309 if( end - start < 4 + 12 + 2 + 16 ) 310 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); 311 312 #if defined(MBEDTLS_THREADING_C) 313 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) 314 return( ret ); 315 #endif 316 317 if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 ) 318 goto cleanup; 319 320 key = &ctx->keys[ctx->active]; 321 322 *ticket_lifetime = ctx->ticket_lifetime; 323 324 memcpy( key_name, key->name, 4 ); 325 326 if( ( ret = ctx->f_rng( ctx->p_rng, iv, 12 ) ) != 0 ) 327 goto cleanup; 328 329 /* Dump session state */ 330 if( ( ret = ssl_save_session( session, 331 state, end - state, &clear_len ) ) != 0 || 332 (unsigned long) clear_len > 65535 ) 333 { 334 goto cleanup; 335 } 336 state_len_bytes[0] = ( clear_len >> 8 ) & 0xff; 337 state_len_bytes[1] = ( clear_len ) & 0xff; 338 339 /* Encrypt and authenticate */ 340 tag = state + clear_len; 341 if( ( ret = mbedtls_cipher_auth_encrypt( &key->ctx, 342 iv, 12, key_name, 4 + 12 + 2, 343 state, clear_len, state, &ciph_len, tag, 16 ) ) != 0 ) 344 { 345 goto cleanup; 346 } 347 if( ciph_len != clear_len ) 348 { 349 ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR; 350 goto cleanup; 351 } 352 353 *tlen = 4 + 12 + 2 + 16 + ciph_len; 354 355 cleanup: 356 #if defined(MBEDTLS_THREADING_C) 357 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 ) 358 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR ); 359 #endif 360 361 return( ret ); 362 } 363 364 /* 365 * Select key based on name 366 */ 367 static mbedtls_ssl_ticket_key *ssl_ticket_select_key( 368 mbedtls_ssl_ticket_context *ctx, 369 const unsigned char name[4] ) 370 { 371 unsigned char i; 372 373 for( i = 0; i < sizeof( ctx->keys ) / sizeof( *ctx->keys ); i++ ) 374 if( memcmp( name, ctx->keys[i].name, 4 ) == 0 ) 375 return( &ctx->keys[i] ); 376 377 return( NULL ); 378 } 379 380 /* 381 * Load session ticket (see mbedtls_ssl_ticket_write for structure) 382 */ 383 int mbedtls_ssl_ticket_parse( void *p_ticket, 384 mbedtls_ssl_session *session, 385 unsigned char *buf, 386 size_t len ) 387 { 388 int ret; 389 mbedtls_ssl_ticket_context *ctx = p_ticket; 390 mbedtls_ssl_ticket_key *key; 391 unsigned char *key_name = buf; 392 unsigned char *iv = buf + 4; 393 unsigned char *enc_len_p = iv + 12; 394 unsigned char *ticket = enc_len_p + 2; 395 unsigned char *tag; 396 size_t enc_len, clear_len; 397 398 if( ctx == NULL || ctx->f_rng == NULL ) 399 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 400 401 /* See mbedtls_ssl_ticket_write() */ 402 if( len < 4 + 12 + 2 + 16 ) 403 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); 404 405 #if defined(MBEDTLS_THREADING_C) 406 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) 407 return( ret ); 408 #endif 409 410 if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 ) 411 goto cleanup; 412 413 enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1]; 414 tag = ticket + enc_len; 415 416 if( len != 4 + 12 + 2 + enc_len + 16 ) 417 { 418 ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA; 419 goto cleanup; 420 } 421 422 /* Select key */ 423 if( ( key = ssl_ticket_select_key( ctx, key_name ) ) == NULL ) 424 { 425 /* We can't know for sure but this is a likely option unless we're 426 * under attack - this is only informative anyway */ 427 ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED; 428 goto cleanup; 429 } 430 431 /* Decrypt and authenticate */ 432 if( ( ret = mbedtls_cipher_auth_decrypt( &key->ctx, iv, 12, 433 key_name, 4 + 12 + 2, ticket, enc_len, 434 ticket, &clear_len, tag, 16 ) ) != 0 ) 435 { 436 if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED ) 437 ret = MBEDTLS_ERR_SSL_INVALID_MAC; 438 439 goto cleanup; 440 } 441 if( clear_len != enc_len ) 442 { 443 ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR; 444 goto cleanup; 445 } 446 447 /* Actually load session */ 448 if( ( ret = ssl_load_session( session, ticket, clear_len ) ) != 0 ) 449 goto cleanup; 450 451 #if defined(MBEDTLS_HAVE_TIME) 452 { 453 /* Check for expiration */ 454 mbedtls_time_t current_time = mbedtls_time( NULL ); 455 456 if( current_time < session->start || 457 (uint32_t)( current_time - session->start ) > ctx->ticket_lifetime ) 458 { 459 ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED; 460 goto cleanup; 461 } 462 } 463 #endif 464 465 cleanup: 466 #if defined(MBEDTLS_THREADING_C) 467 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 ) 468 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR ); 469 #endif 470 471 return( ret ); 472 } 473 474 /* 475 * Free context 476 */ 477 void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx ) 478 { 479 mbedtls_cipher_free( &ctx->keys[0].ctx ); 480 mbedtls_cipher_free( &ctx->keys[1].ctx ); 481 482 #if defined(MBEDTLS_THREADING_C) 483 mbedtls_mutex_free( &ctx->mutex ); 484 #endif 485 486 mbedtls_zeroize( ctx, sizeof( mbedtls_ssl_ticket_context ) ); 487 } 488 489 #endif /* MBEDTLS_SSL_TICKET_C */ 490