1 /* Copyright (c) 2016, Google Inc. 2 * 3 * Permission to use, copy, modify, and/or distribute this software for any 4 * purpose with or without fee is hereby granted, provided that the above 5 * copyright notice and this permission notice appear in all copies. 6 * 7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION 12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN 13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ 14 15 #include <openssl/ssl.h> 16 17 #include <assert.h> 18 #include <string.h> 19 20 #include <openssl/aead.h> 21 #include <openssl/bytestring.h> 22 #include <openssl/digest.h> 23 #include <openssl/hkdf.h> 24 #include <openssl/hmac.h> 25 #include <openssl/mem.h> 26 27 #include "../crypto/internal.h" 28 #include "internal.h" 29 30 31 static int init_key_schedule(SSL_HANDSHAKE *hs, uint16_t version, 32 int algorithm_prf) { 33 if (!SSL_TRANSCRIPT_init_hash(&hs->transcript, version, algorithm_prf)) { 34 return 0; 35 } 36 37 hs->hash_len = SSL_TRANSCRIPT_digest_len(&hs->transcript); 38 39 /* Initialize the secret to the zero key. */ 40 OPENSSL_memset(hs->secret, 0, hs->hash_len); 41 42 return 1; 43 } 44 45 int tls13_init_key_schedule(SSL_HANDSHAKE *hs) { 46 if (!init_key_schedule(hs, ssl3_protocol_version(hs->ssl), 47 hs->new_cipher->algorithm_prf)) { 48 return 0; 49 } 50 51 SSL_TRANSCRIPT_free_buffer(&hs->transcript); 52 return 1; 53 } 54 55 int tls13_init_early_key_schedule(SSL_HANDSHAKE *hs) { 56 SSL *const ssl = hs->ssl; 57 uint16_t session_version; 58 if (!ssl->method->version_from_wire(&session_version, 59 ssl->session->ssl_version) || 60 !init_key_schedule(hs, session_version, 61 ssl->session->cipher->algorithm_prf)) { 62 return 0; 63 } 64 65 return 1; 66 } 67 68 int tls13_advance_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *in, 69 size_t len) { 70 return HKDF_extract(hs->secret, &hs->hash_len, 71 SSL_TRANSCRIPT_md(&hs->transcript), in, len, hs->secret, 72 hs->hash_len); 73 } 74 75 static int hkdf_expand_label(uint8_t *out, const EVP_MD *digest, 76 const uint8_t *secret, size_t secret_len, 77 const uint8_t *label, size_t label_len, 78 const uint8_t *hash, size_t hash_len, size_t len) { 79 static const char kTLS13LabelVersion[] = "TLS 1.3, "; 80 81 CBB cbb, child; 82 uint8_t *hkdf_label; 83 size_t hkdf_label_len; 84 if (!CBB_init(&cbb, 2 + 1 + strlen(kTLS13LabelVersion) + label_len + 1 + 85 hash_len) || 86 !CBB_add_u16(&cbb, len) || 87 !CBB_add_u8_length_prefixed(&cbb, &child) || 88 !CBB_add_bytes(&child, (const uint8_t *)kTLS13LabelVersion, 89 strlen(kTLS13LabelVersion)) || 90 !CBB_add_bytes(&child, label, label_len) || 91 !CBB_add_u8_length_prefixed(&cbb, &child) || 92 !CBB_add_bytes(&child, hash, hash_len) || 93 !CBB_finish(&cbb, &hkdf_label, &hkdf_label_len)) { 94 CBB_cleanup(&cbb); 95 return 0; 96 } 97 98 int ret = HKDF_expand(out, len, digest, secret, secret_len, hkdf_label, 99 hkdf_label_len); 100 OPENSSL_free(hkdf_label); 101 return ret; 102 } 103 104 /* derive_secret derives a secret of length |len| and writes the result in |out| 105 * with the given label and the current base secret and most recently-saved 106 * handshake context. It returns one on success and zero on error. */ 107 static int derive_secret(SSL_HANDSHAKE *hs, uint8_t *out, size_t len, 108 const uint8_t *label, size_t label_len) { 109 uint8_t context_hash[EVP_MAX_MD_SIZE]; 110 size_t context_hash_len; 111 if (!SSL_TRANSCRIPT_get_hash(&hs->transcript, context_hash, 112 &context_hash_len)) { 113 return 0; 114 } 115 116 return hkdf_expand_label(out, SSL_TRANSCRIPT_md(&hs->transcript), hs->secret, 117 hs->hash_len, label, label_len, context_hash, 118 context_hash_len, len); 119 } 120 121 int tls13_set_traffic_key(SSL *ssl, enum evp_aead_direction_t direction, 122 const uint8_t *traffic_secret, 123 size_t traffic_secret_len) { 124 const SSL_SESSION *session = SSL_get_session(ssl); 125 uint16_t version; 126 if (!ssl->method->version_from_wire(&version, session->ssl_version)) { 127 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 128 return 0; 129 } 130 131 if (traffic_secret_len > 0xff) { 132 OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW); 133 return 0; 134 } 135 136 /* Look up cipher suite properties. */ 137 const EVP_AEAD *aead; 138 size_t discard; 139 if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, session->cipher, 140 version)) { 141 return 0; 142 } 143 144 const EVP_MD *digest = ssl_get_handshake_digest( 145 session->cipher->algorithm_prf, version); 146 147 /* Derive the key. */ 148 size_t key_len = EVP_AEAD_key_length(aead); 149 uint8_t key[EVP_AEAD_MAX_KEY_LENGTH]; 150 if (!hkdf_expand_label(key, digest, traffic_secret, traffic_secret_len, 151 (const uint8_t *)"key", 3, NULL, 0, key_len)) { 152 return 0; 153 } 154 155 /* Derive the IV. */ 156 size_t iv_len = EVP_AEAD_nonce_length(aead); 157 uint8_t iv[EVP_AEAD_MAX_NONCE_LENGTH]; 158 if (!hkdf_expand_label(iv, digest, traffic_secret, traffic_secret_len, 159 (const uint8_t *)"iv", 2, NULL, 0, iv_len)) { 160 return 0; 161 } 162 163 SSL_AEAD_CTX *traffic_aead = SSL_AEAD_CTX_new( 164 direction, version, session->cipher, key, key_len, NULL, 0, iv, iv_len); 165 if (traffic_aead == NULL) { 166 return 0; 167 } 168 169 if (direction == evp_aead_open) { 170 if (!ssl->method->set_read_state(ssl, traffic_aead)) { 171 return 0; 172 } 173 } else { 174 if (!ssl->method->set_write_state(ssl, traffic_aead)) { 175 return 0; 176 } 177 } 178 179 /* Save the traffic secret. */ 180 if (direction == evp_aead_open) { 181 OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret, 182 traffic_secret_len); 183 ssl->s3->read_traffic_secret_len = traffic_secret_len; 184 } else { 185 OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret, 186 traffic_secret_len); 187 ssl->s3->write_traffic_secret_len = traffic_secret_len; 188 } 189 190 return 1; 191 } 192 193 static const char kTLS13LabelExporter[] = "exporter master secret"; 194 static const char kTLS13LabelEarlyExporter[] = "early exporter master secret"; 195 196 static const char kTLS13LabelClientEarlyTraffic[] = 197 "client early traffic secret"; 198 static const char kTLS13LabelClientHandshakeTraffic[] = 199 "client handshake traffic secret"; 200 static const char kTLS13LabelServerHandshakeTraffic[] = 201 "server handshake traffic secret"; 202 static const char kTLS13LabelClientApplicationTraffic[] = 203 "client application traffic secret"; 204 static const char kTLS13LabelServerApplicationTraffic[] = 205 "server application traffic secret"; 206 207 int tls13_derive_early_secrets(SSL_HANDSHAKE *hs) { 208 SSL *const ssl = hs->ssl; 209 return derive_secret(hs, hs->early_traffic_secret, hs->hash_len, 210 (const uint8_t *)kTLS13LabelClientEarlyTraffic, 211 strlen(kTLS13LabelClientEarlyTraffic)) && 212 ssl_log_secret(ssl, "CLIENT_EARLY_TRAFFIC_SECRET", 213 hs->early_traffic_secret, hs->hash_len) && 214 derive_secret(hs, ssl->s3->early_exporter_secret, hs->hash_len, 215 (const uint8_t *)kTLS13LabelEarlyExporter, 216 strlen(kTLS13LabelEarlyExporter)); 217 } 218 219 int tls13_derive_handshake_secrets(SSL_HANDSHAKE *hs) { 220 SSL *const ssl = hs->ssl; 221 return derive_secret(hs, hs->client_handshake_secret, hs->hash_len, 222 (const uint8_t *)kTLS13LabelClientHandshakeTraffic, 223 strlen(kTLS13LabelClientHandshakeTraffic)) && 224 ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET", 225 hs->client_handshake_secret, hs->hash_len) && 226 derive_secret(hs, hs->server_handshake_secret, hs->hash_len, 227 (const uint8_t *)kTLS13LabelServerHandshakeTraffic, 228 strlen(kTLS13LabelServerHandshakeTraffic)) && 229 ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET", 230 hs->server_handshake_secret, hs->hash_len); 231 } 232 233 int tls13_derive_application_secrets(SSL_HANDSHAKE *hs) { 234 SSL *const ssl = hs->ssl; 235 ssl->s3->exporter_secret_len = hs->hash_len; 236 return derive_secret(hs, hs->client_traffic_secret_0, hs->hash_len, 237 (const uint8_t *)kTLS13LabelClientApplicationTraffic, 238 strlen(kTLS13LabelClientApplicationTraffic)) && 239 ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0", 240 hs->client_traffic_secret_0, hs->hash_len) && 241 derive_secret(hs, hs->server_traffic_secret_0, hs->hash_len, 242 (const uint8_t *)kTLS13LabelServerApplicationTraffic, 243 strlen(kTLS13LabelServerApplicationTraffic)) && 244 ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0", 245 hs->server_traffic_secret_0, hs->hash_len) && 246 derive_secret(hs, ssl->s3->exporter_secret, hs->hash_len, 247 (const uint8_t *)kTLS13LabelExporter, 248 strlen(kTLS13LabelExporter)); 249 } 250 251 static const char kTLS13LabelApplicationTraffic[] = 252 "application traffic secret"; 253 254 int tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) { 255 const EVP_MD *digest = ssl_get_handshake_digest( 256 SSL_get_session(ssl)->cipher->algorithm_prf, ssl3_protocol_version(ssl)); 257 258 uint8_t *secret; 259 size_t secret_len; 260 if (direction == evp_aead_open) { 261 secret = ssl->s3->read_traffic_secret; 262 secret_len = ssl->s3->read_traffic_secret_len; 263 } else { 264 secret = ssl->s3->write_traffic_secret; 265 secret_len = ssl->s3->write_traffic_secret_len; 266 } 267 268 if (!hkdf_expand_label(secret, digest, secret, secret_len, 269 (const uint8_t *)kTLS13LabelApplicationTraffic, 270 strlen(kTLS13LabelApplicationTraffic), NULL, 0, 271 secret_len)) { 272 return 0; 273 } 274 275 return tls13_set_traffic_key(ssl, direction, secret, secret_len); 276 } 277 278 static const char kTLS13LabelResumption[] = "resumption master secret"; 279 280 int tls13_derive_resumption_secret(SSL_HANDSHAKE *hs) { 281 if (hs->hash_len > SSL_MAX_MASTER_KEY_LENGTH) { 282 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 283 return 0; 284 } 285 286 hs->new_session->master_key_length = hs->hash_len; 287 return derive_secret( 288 hs, hs->new_session->master_key, hs->new_session->master_key_length, 289 (const uint8_t *)kTLS13LabelResumption, strlen(kTLS13LabelResumption)); 290 } 291 292 static const char kTLS13LabelFinished[] = "finished"; 293 294 /* tls13_verify_data sets |out| to be the HMAC of |context| using a derived 295 * Finished key for both Finished messages and the PSK binder. */ 296 static int tls13_verify_data(const EVP_MD *digest, uint8_t *out, 297 size_t *out_len, const uint8_t *secret, 298 size_t hash_len, uint8_t *context, 299 size_t context_len) { 300 uint8_t key[EVP_MAX_MD_SIZE]; 301 unsigned len; 302 if (!hkdf_expand_label(key, digest, secret, hash_len, 303 (const uint8_t *)kTLS13LabelFinished, 304 strlen(kTLS13LabelFinished), NULL, 0, hash_len) || 305 HMAC(digest, key, hash_len, context, context_len, out, &len) == NULL) { 306 return 0; 307 } 308 *out_len = len; 309 return 1; 310 } 311 312 int tls13_finished_mac(SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len, 313 int is_server) { 314 const uint8_t *traffic_secret; 315 if (is_server) { 316 traffic_secret = hs->server_handshake_secret; 317 } else { 318 traffic_secret = hs->client_handshake_secret; 319 } 320 321 uint8_t context_hash[EVP_MAX_MD_SIZE]; 322 size_t context_hash_len; 323 if (!SSL_TRANSCRIPT_get_hash(&hs->transcript, context_hash, 324 &context_hash_len) || 325 !tls13_verify_data(SSL_TRANSCRIPT_md(&hs->transcript), out, out_len, 326 traffic_secret, hs->hash_len, context_hash, 327 context_hash_len)) { 328 return 0; 329 } 330 return 1; 331 } 332 333 int tls13_export_keying_material(SSL *ssl, uint8_t *out, size_t out_len, 334 const char *label, size_t label_len, 335 const uint8_t *context, size_t context_len, 336 int use_context) { 337 const EVP_MD *digest = ssl_get_handshake_digest( 338 SSL_get_session(ssl)->cipher->algorithm_prf, ssl3_protocol_version(ssl)); 339 340 const uint8_t *hash = NULL; 341 size_t hash_len = 0; 342 if (use_context) { 343 hash = context; 344 hash_len = context_len; 345 } 346 return hkdf_expand_label(out, digest, ssl->s3->exporter_secret, 347 ssl->s3->exporter_secret_len, (const uint8_t *)label, 348 label_len, hash, hash_len, out_len); 349 } 350 351 static const char kTLS13LabelPSKBinder[] = "resumption psk binder key"; 352 353 static int tls13_psk_binder(uint8_t *out, const EVP_MD *digest, uint8_t *psk, 354 size_t psk_len, uint8_t *context, 355 size_t context_len, size_t hash_len) { 356 uint8_t binder_context[EVP_MAX_MD_SIZE]; 357 unsigned binder_context_len; 358 if (!EVP_Digest(NULL, 0, binder_context, &binder_context_len, digest, NULL)) { 359 return 0; 360 } 361 362 uint8_t early_secret[EVP_MAX_MD_SIZE] = {0}; 363 size_t early_secret_len; 364 if (!HKDF_extract(early_secret, &early_secret_len, digest, psk, hash_len, 365 NULL, 0)) { 366 return 0; 367 } 368 369 uint8_t binder_key[EVP_MAX_MD_SIZE] = {0}; 370 size_t len; 371 if (!hkdf_expand_label(binder_key, digest, early_secret, hash_len, 372 (const uint8_t *)kTLS13LabelPSKBinder, 373 strlen(kTLS13LabelPSKBinder), binder_context, 374 binder_context_len, hash_len) || 375 !tls13_verify_data(digest, out, &len, binder_key, hash_len, context, 376 context_len)) { 377 return 0; 378 } 379 380 return 1; 381 } 382 383 int tls13_write_psk_binder(SSL_HANDSHAKE *hs, uint8_t *msg, size_t len) { 384 SSL *const ssl = hs->ssl; 385 const EVP_MD *digest = SSL_SESSION_get_digest(ssl->session, ssl); 386 if (digest == NULL) { 387 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 388 return 0; 389 } 390 size_t hash_len = EVP_MD_size(digest); 391 392 if (len < hash_len + 3) { 393 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 394 return 0; 395 } 396 397 EVP_MD_CTX ctx; 398 EVP_MD_CTX_init(&ctx); 399 uint8_t context[EVP_MAX_MD_SIZE]; 400 unsigned context_len; 401 if (!EVP_DigestInit_ex(&ctx, digest, NULL) || 402 !EVP_DigestUpdate(&ctx, hs->transcript.buffer->data, 403 hs->transcript.buffer->length) || 404 !EVP_DigestUpdate(&ctx, msg, len - hash_len - 3) || 405 !EVP_DigestFinal_ex(&ctx, context, &context_len)) { 406 EVP_MD_CTX_cleanup(&ctx); 407 return 0; 408 } 409 410 EVP_MD_CTX_cleanup(&ctx); 411 412 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; 413 if (!tls13_psk_binder(verify_data, digest, ssl->session->master_key, 414 ssl->session->master_key_length, context, context_len, 415 hash_len)) { 416 return 0; 417 } 418 419 OPENSSL_memcpy(msg + len - hash_len, verify_data, hash_len); 420 return 1; 421 } 422 423 int tls13_verify_psk_binder(SSL_HANDSHAKE *hs, SSL_SESSION *session, 424 CBS *binders) { 425 size_t hash_len = SSL_TRANSCRIPT_digest_len(&hs->transcript); 426 427 /* Get the full ClientHello, including message header. It must be large enough 428 * to exclude the binders. */ 429 CBS message; 430 hs->ssl->method->get_current_message(hs->ssl, &message); 431 if (CBS_len(&message) < CBS_len(binders) + 2) { 432 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 433 return 0; 434 } 435 436 /* Hash a ClientHello prefix up to the binders. For now, this assumes we only 437 * ever verify PSK binders on initial ClientHellos. */ 438 uint8_t context[EVP_MAX_MD_SIZE]; 439 unsigned context_len; 440 if (!EVP_Digest(CBS_data(&message), CBS_len(&message) - CBS_len(binders) - 2, 441 context, &context_len, SSL_TRANSCRIPT_md(&hs->transcript), 442 NULL)) { 443 return 0; 444 } 445 446 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; 447 CBS binder; 448 if (!tls13_psk_binder(verify_data, SSL_TRANSCRIPT_md(&hs->transcript), 449 session->master_key, session->master_key_length, 450 context, context_len, hash_len) || 451 /* We only consider the first PSK, so compare against the first binder. */ 452 !CBS_get_u8_length_prefixed(binders, &binder)) { 453 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 454 return 0; 455 } 456 457 int binder_ok = 458 CBS_len(&binder) == hash_len && 459 CRYPTO_memcmp(CBS_data(&binder), verify_data, hash_len) == 0; 460 #if defined(BORINGSSL_UNSAFE_FUZZER_MODE) 461 binder_ok = 1; 462 #endif 463 if (!binder_ok) { 464 OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED); 465 return 0; 466 } 467 468 return 1; 469 } 470
