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 <utility> 21 22 #include <openssl/aead.h> 23 #include <openssl/bytestring.h> 24 #include <openssl/digest.h> 25 #include <openssl/hkdf.h> 26 #include <openssl/hmac.h> 27 #include <openssl/mem.h> 28 29 #include "../crypto/internal.h" 30 #include "internal.h" 31 32 33 namespace bssl { 34 35 static int init_key_schedule(SSL_HANDSHAKE *hs, uint16_t version, 36 const SSL_CIPHER *cipher) { 37 if (!hs->transcript.InitHash(version, cipher)) { 38 return 0; 39 } 40 41 hs->hash_len = hs->transcript.DigestLen(); 42 43 // Initialize the secret to the zero key. 44 OPENSSL_memset(hs->secret, 0, hs->hash_len); 45 46 return 1; 47 } 48 49 int tls13_init_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *psk, 50 size_t psk_len) { 51 if (!init_key_schedule(hs, ssl_protocol_version(hs->ssl), hs->new_cipher)) { 52 return 0; 53 } 54 55 hs->transcript.FreeBuffer(); 56 return HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), psk, 57 psk_len, hs->secret, hs->hash_len); 58 } 59 60 int tls13_init_early_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *psk, 61 size_t psk_len) { 62 SSL *const ssl = hs->ssl; 63 return init_key_schedule(hs, ssl_session_protocol_version(ssl->session), 64 ssl->session->cipher) && 65 HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), psk, 66 psk_len, hs->secret, hs->hash_len); 67 } 68 69 static int hkdf_expand_label(uint8_t *out, const EVP_MD *digest, 70 const uint8_t *secret, size_t secret_len, 71 const char *label, size_t label_len, 72 const uint8_t *hash, size_t hash_len, size_t len) { 73 static const char kTLS13LabelVersion[] = "tls13 "; 74 75 ScopedCBB cbb; 76 CBB child; 77 uint8_t *hkdf_label; 78 size_t hkdf_label_len; 79 if (!CBB_init(cbb.get(), 2 + 1 + strlen(kTLS13LabelVersion) + label_len + 1 + 80 hash_len) || 81 !CBB_add_u16(cbb.get(), len) || 82 !CBB_add_u8_length_prefixed(cbb.get(), &child) || 83 !CBB_add_bytes(&child, (const uint8_t *)kTLS13LabelVersion, 84 strlen(kTLS13LabelVersion)) || 85 !CBB_add_bytes(&child, (const uint8_t *)label, label_len) || 86 !CBB_add_u8_length_prefixed(cbb.get(), &child) || 87 !CBB_add_bytes(&child, hash, hash_len) || 88 !CBB_finish(cbb.get(), &hkdf_label, &hkdf_label_len)) { 89 return 0; 90 } 91 92 int ret = HKDF_expand(out, len, digest, secret, secret_len, hkdf_label, 93 hkdf_label_len); 94 OPENSSL_free(hkdf_label); 95 return ret; 96 } 97 98 static const char kTLS13LabelDerived[] = "derived"; 99 100 int tls13_advance_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *in, 101 size_t len) { 102 uint8_t derive_context[EVP_MAX_MD_SIZE]; 103 unsigned derive_context_len; 104 if (!EVP_Digest(nullptr, 0, derive_context, &derive_context_len, 105 hs->transcript.Digest(), nullptr)) { 106 return 0; 107 } 108 109 if (!hkdf_expand_label(hs->secret, hs->transcript.Digest(), hs->secret, 110 hs->hash_len, kTLS13LabelDerived, 111 strlen(kTLS13LabelDerived), derive_context, 112 derive_context_len, hs->hash_len)) { 113 return 0; 114 } 115 116 return HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), in, 117 len, hs->secret, hs->hash_len); 118 } 119 120 // derive_secret derives a secret of length |len| and writes the result in |out| 121 // with the given label and the current base secret and most recently-saved 122 // handshake context. It returns one on success and zero on error. 123 static int derive_secret(SSL_HANDSHAKE *hs, uint8_t *out, size_t len, 124 const char *label, size_t label_len) { 125 uint8_t context_hash[EVP_MAX_MD_SIZE]; 126 size_t context_hash_len; 127 if (!hs->transcript.GetHash(context_hash, &context_hash_len)) { 128 return 0; 129 } 130 131 return hkdf_expand_label(out, hs->transcript.Digest(), hs->secret, 132 hs->hash_len, label, label_len, context_hash, 133 context_hash_len, len); 134 } 135 136 int tls13_set_traffic_key(SSL *ssl, enum evp_aead_direction_t direction, 137 const uint8_t *traffic_secret, 138 size_t traffic_secret_len) { 139 const SSL_SESSION *session = SSL_get_session(ssl); 140 uint16_t version = ssl_session_protocol_version(session); 141 142 if (traffic_secret_len > 0xff) { 143 OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW); 144 return 0; 145 } 146 147 // Look up cipher suite properties. 148 const EVP_AEAD *aead; 149 size_t discard; 150 if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, session->cipher, 151 version, SSL_is_dtls(ssl))) { 152 return 0; 153 } 154 155 const EVP_MD *digest = ssl_session_get_digest(session); 156 157 // Derive the key. 158 size_t key_len = EVP_AEAD_key_length(aead); 159 uint8_t key[EVP_AEAD_MAX_KEY_LENGTH]; 160 if (!hkdf_expand_label(key, digest, traffic_secret, traffic_secret_len, "key", 161 3, NULL, 0, key_len)) { 162 return 0; 163 } 164 165 // Derive the IV. 166 size_t iv_len = EVP_AEAD_nonce_length(aead); 167 uint8_t iv[EVP_AEAD_MAX_NONCE_LENGTH]; 168 if (!hkdf_expand_label(iv, digest, traffic_secret, traffic_secret_len, "iv", 169 2, NULL, 0, iv_len)) { 170 return 0; 171 } 172 173 UniquePtr<SSLAEADContext> traffic_aead = 174 SSLAEADContext::Create(direction, session->ssl_version, SSL_is_dtls(ssl), 175 session->cipher, MakeConstSpan(key, key_len), 176 Span<const uint8_t>(), MakeConstSpan(iv, iv_len)); 177 if (!traffic_aead) { 178 return 0; 179 } 180 181 if (direction == evp_aead_open) { 182 if (!ssl->method->set_read_state(ssl, std::move(traffic_aead))) { 183 return 0; 184 } 185 } else { 186 if (!ssl->method->set_write_state(ssl, std::move(traffic_aead))) { 187 return 0; 188 } 189 } 190 191 // Save the traffic secret. 192 if (direction == evp_aead_open) { 193 OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret, 194 traffic_secret_len); 195 ssl->s3->read_traffic_secret_len = traffic_secret_len; 196 } else { 197 OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret, 198 traffic_secret_len); 199 ssl->s3->write_traffic_secret_len = traffic_secret_len; 200 } 201 202 return 1; 203 } 204 205 206 static const char kTLS13LabelExporter[] = "exp master"; 207 static const char kTLS13LabelEarlyExporter[] = "e exp master"; 208 209 static const char kTLS13LabelClientEarlyTraffic[] = "c e traffic"; 210 static const char kTLS13LabelClientHandshakeTraffic[] = "c hs traffic"; 211 static const char kTLS13LabelServerHandshakeTraffic[] = "s hs traffic"; 212 static const char kTLS13LabelClientApplicationTraffic[] = "c ap traffic"; 213 static const char kTLS13LabelServerApplicationTraffic[] = "s ap traffic"; 214 215 int tls13_derive_early_secrets(SSL_HANDSHAKE *hs) { 216 SSL *const ssl = hs->ssl; 217 if (!derive_secret(hs, hs->early_traffic_secret, hs->hash_len, 218 kTLS13LabelClientEarlyTraffic, 219 strlen(kTLS13LabelClientEarlyTraffic)) || 220 !ssl_log_secret(ssl, "CLIENT_EARLY_TRAFFIC_SECRET", 221 hs->early_traffic_secret, hs->hash_len) || 222 !derive_secret(hs, ssl->s3->early_exporter_secret, hs->hash_len, 223 kTLS13LabelEarlyExporter, 224 strlen(kTLS13LabelEarlyExporter))) { 225 return 0; 226 } 227 ssl->s3->early_exporter_secret_len = hs->hash_len; 228 return 1; 229 } 230 231 int tls13_derive_handshake_secrets(SSL_HANDSHAKE *hs) { 232 SSL *const ssl = hs->ssl; 233 return derive_secret(hs, hs->client_handshake_secret, hs->hash_len, 234 kTLS13LabelClientHandshakeTraffic, 235 strlen(kTLS13LabelClientHandshakeTraffic)) && 236 ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET", 237 hs->client_handshake_secret, hs->hash_len) && 238 derive_secret(hs, hs->server_handshake_secret, hs->hash_len, 239 kTLS13LabelServerHandshakeTraffic, 240 strlen(kTLS13LabelServerHandshakeTraffic)) && 241 ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET", 242 hs->server_handshake_secret, hs->hash_len); 243 } 244 245 int tls13_derive_application_secrets(SSL_HANDSHAKE *hs) { 246 SSL *const ssl = hs->ssl; 247 ssl->s3->exporter_secret_len = hs->hash_len; 248 return derive_secret(hs, hs->client_traffic_secret_0, hs->hash_len, 249 kTLS13LabelClientApplicationTraffic, 250 strlen(kTLS13LabelClientApplicationTraffic)) && 251 ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0", 252 hs->client_traffic_secret_0, hs->hash_len) && 253 derive_secret(hs, hs->server_traffic_secret_0, hs->hash_len, 254 kTLS13LabelServerApplicationTraffic, 255 strlen(kTLS13LabelServerApplicationTraffic)) && 256 ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0", 257 hs->server_traffic_secret_0, hs->hash_len) && 258 derive_secret(hs, ssl->s3->exporter_secret, hs->hash_len, 259 kTLS13LabelExporter, strlen(kTLS13LabelExporter)) && 260 ssl_log_secret(ssl, "EXPORTER_SECRET", ssl->s3->exporter_secret, 261 hs->hash_len); 262 } 263 264 static const char kTLS13LabelApplicationTraffic[] = "traffic upd"; 265 266 int tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) { 267 uint8_t *secret; 268 size_t secret_len; 269 if (direction == evp_aead_open) { 270 secret = ssl->s3->read_traffic_secret; 271 secret_len = ssl->s3->read_traffic_secret_len; 272 } else { 273 secret = ssl->s3->write_traffic_secret; 274 secret_len = ssl->s3->write_traffic_secret_len; 275 } 276 277 const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl)); 278 if (!hkdf_expand_label( 279 secret, digest, secret, secret_len, kTLS13LabelApplicationTraffic, 280 strlen(kTLS13LabelApplicationTraffic), NULL, 0, secret_len)) { 281 return 0; 282 } 283 284 return tls13_set_traffic_key(ssl, direction, secret, secret_len); 285 } 286 287 static const char kTLS13LabelResumption[] = "res master"; 288 289 int tls13_derive_resumption_secret(SSL_HANDSHAKE *hs) { 290 if (hs->hash_len > SSL_MAX_MASTER_KEY_LENGTH) { 291 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 292 return 0; 293 } 294 hs->new_session->master_key_length = hs->hash_len; 295 return derive_secret(hs, hs->new_session->master_key, 296 hs->new_session->master_key_length, 297 kTLS13LabelResumption, strlen(kTLS13LabelResumption)); 298 } 299 300 static const char kTLS13LabelFinished[] = "finished"; 301 302 // tls13_verify_data sets |out| to be the HMAC of |context| using a derived 303 // Finished key for both Finished messages and the PSK binder. 304 static int tls13_verify_data(const EVP_MD *digest, uint16_t version, 305 uint8_t *out, size_t *out_len, 306 const uint8_t *secret, size_t hash_len, 307 uint8_t *context, size_t context_len) { 308 uint8_t key[EVP_MAX_MD_SIZE]; 309 unsigned len; 310 if (!hkdf_expand_label(key, digest, secret, hash_len, kTLS13LabelFinished, 311 strlen(kTLS13LabelFinished), NULL, 0, hash_len) || 312 HMAC(digest, key, hash_len, context, context_len, out, &len) == NULL) { 313 return 0; 314 } 315 *out_len = len; 316 return 1; 317 } 318 319 int tls13_finished_mac(SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len, 320 int is_server) { 321 const uint8_t *traffic_secret; 322 if (is_server) { 323 traffic_secret = hs->server_handshake_secret; 324 } else { 325 traffic_secret = hs->client_handshake_secret; 326 } 327 328 uint8_t context_hash[EVP_MAX_MD_SIZE]; 329 size_t context_hash_len; 330 if (!hs->transcript.GetHash(context_hash, &context_hash_len) || 331 !tls13_verify_data(hs->transcript.Digest(), hs->ssl->version, out, 332 out_len, traffic_secret, hs->hash_len, context_hash, 333 context_hash_len)) { 334 return 0; 335 } 336 return 1; 337 } 338 339 static const char kTLS13LabelResumptionPSK[] = "resumption"; 340 341 bool tls13_derive_session_psk(SSL_SESSION *session, Span<const uint8_t> nonce) { 342 const EVP_MD *digest = ssl_session_get_digest(session); 343 return hkdf_expand_label(session->master_key, digest, session->master_key, 344 session->master_key_length, kTLS13LabelResumptionPSK, 345 strlen(kTLS13LabelResumptionPSK), nonce.data(), 346 nonce.size(), session->master_key_length); 347 } 348 349 static const char kTLS13LabelExportKeying[] = "exporter"; 350 351 int tls13_export_keying_material(SSL *ssl, Span<uint8_t> out, 352 Span<const uint8_t> secret, 353 Span<const char> label, 354 Span<const uint8_t> context) { 355 if (secret.empty()) { 356 assert(0); 357 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 358 return 0; 359 } 360 361 const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl)); 362 363 uint8_t hash[EVP_MAX_MD_SIZE]; 364 uint8_t export_context[EVP_MAX_MD_SIZE]; 365 uint8_t derived_secret[EVP_MAX_MD_SIZE]; 366 unsigned hash_len; 367 unsigned export_context_len; 368 unsigned derived_secret_len = EVP_MD_size(digest); 369 return EVP_Digest(context.data(), context.size(), hash, &hash_len, digest, 370 nullptr) && 371 EVP_Digest(nullptr, 0, export_context, &export_context_len, digest, 372 nullptr) && 373 hkdf_expand_label(derived_secret, digest, secret.data(), secret.size(), 374 label.data(), label.size(), export_context, 375 export_context_len, derived_secret_len) && 376 hkdf_expand_label(out.data(), digest, derived_secret, 377 derived_secret_len, kTLS13LabelExportKeying, 378 strlen(kTLS13LabelExportKeying), hash, hash_len, 379 out.size()); 380 } 381 382 static const char kTLS13LabelPSKBinder[] = "res binder"; 383 384 static int tls13_psk_binder(uint8_t *out, uint16_t version, 385 const EVP_MD *digest, uint8_t *psk, size_t psk_len, 386 uint8_t *context, size_t context_len, 387 size_t hash_len) { 388 uint8_t binder_context[EVP_MAX_MD_SIZE]; 389 unsigned binder_context_len; 390 if (!EVP_Digest(NULL, 0, binder_context, &binder_context_len, digest, NULL)) { 391 return 0; 392 } 393 394 uint8_t early_secret[EVP_MAX_MD_SIZE] = {0}; 395 size_t early_secret_len; 396 if (!HKDF_extract(early_secret, &early_secret_len, digest, psk, hash_len, 397 NULL, 0)) { 398 return 0; 399 } 400 401 uint8_t binder_key[EVP_MAX_MD_SIZE] = {0}; 402 size_t len; 403 if (!hkdf_expand_label(binder_key, digest, early_secret, hash_len, 404 kTLS13LabelPSKBinder, strlen(kTLS13LabelPSKBinder), 405 binder_context, binder_context_len, hash_len) || 406 !tls13_verify_data(digest, version, out, &len, binder_key, hash_len, 407 context, context_len)) { 408 return 0; 409 } 410 411 return 1; 412 } 413 414 int tls13_write_psk_binder(SSL_HANDSHAKE *hs, uint8_t *msg, size_t len) { 415 SSL *const ssl = hs->ssl; 416 const EVP_MD *digest = ssl_session_get_digest(ssl->session); 417 size_t hash_len = EVP_MD_size(digest); 418 419 if (len < hash_len + 3) { 420 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 421 return 0; 422 } 423 424 ScopedEVP_MD_CTX ctx; 425 uint8_t context[EVP_MAX_MD_SIZE]; 426 unsigned context_len; 427 428 if (!EVP_DigestInit_ex(ctx.get(), digest, NULL) || 429 !EVP_DigestUpdate(ctx.get(), hs->transcript.buffer().data(), 430 hs->transcript.buffer().size()) || 431 !EVP_DigestUpdate(ctx.get(), msg, len - hash_len - 3) || 432 !EVP_DigestFinal_ex(ctx.get(), context, &context_len)) { 433 return 0; 434 } 435 436 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; 437 if (!tls13_psk_binder(verify_data, ssl->session->ssl_version, digest, 438 ssl->session->master_key, 439 ssl->session->master_key_length, context, context_len, 440 hash_len)) { 441 return 0; 442 } 443 444 OPENSSL_memcpy(msg + len - hash_len, verify_data, hash_len); 445 return 1; 446 } 447 448 int tls13_verify_psk_binder(SSL_HANDSHAKE *hs, SSL_SESSION *session, 449 const SSLMessage &msg, CBS *binders) { 450 size_t hash_len = hs->transcript.DigestLen(); 451 452 // The message must be large enough to exclude the binders. 453 if (CBS_len(&msg.raw) < CBS_len(binders) + 2) { 454 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 455 return 0; 456 } 457 458 // Hash a ClientHello prefix up to the binders. This includes the header. For 459 // now, this assumes we only ever verify PSK binders on initial 460 // ClientHellos. 461 uint8_t context[EVP_MAX_MD_SIZE]; 462 unsigned context_len; 463 if (!EVP_Digest(CBS_data(&msg.raw), CBS_len(&msg.raw) - CBS_len(binders) - 2, 464 context, &context_len, hs->transcript.Digest(), NULL)) { 465 return 0; 466 } 467 468 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; 469 CBS binder; 470 if (!tls13_psk_binder(verify_data, hs->ssl->version, hs->transcript.Digest(), 471 session->master_key, session->master_key_length, 472 context, context_len, hash_len) || 473 // We only consider the first PSK, so compare against the first binder. 474 !CBS_get_u8_length_prefixed(binders, &binder)) { 475 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 476 return 0; 477 } 478 479 int binder_ok = 480 CBS_len(&binder) == hash_len && 481 CRYPTO_memcmp(CBS_data(&binder), verify_data, hash_len) == 0; 482 #if defined(BORINGSSL_UNSAFE_FUZZER_MODE) 483 binder_ok = 1; 484 #endif 485 if (!binder_ok) { 486 OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED); 487 return 0; 488 } 489 490 return 1; 491 } 492 493 } // namespace bssl 494