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 return init_key_schedule(hs, SSL_SESSION_protocol_version(ssl->session), 58 ssl->session->cipher->algorithm_prf); 59 } 60 61 int tls13_advance_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *in, 62 size_t len) { 63 return HKDF_extract(hs->secret, &hs->hash_len, 64 SSL_TRANSCRIPT_md(&hs->transcript), in, len, hs->secret, 65 hs->hash_len); 66 } 67 68 static int hkdf_expand_label(uint8_t *out, const EVP_MD *digest, 69 const uint8_t *secret, size_t secret_len, 70 const uint8_t *label, size_t label_len, 71 const uint8_t *hash, size_t hash_len, size_t len) { 72 static const char kTLS13LabelVersion[] = "TLS 1.3, "; 73 74 CBB cbb, child; 75 uint8_t *hkdf_label; 76 size_t hkdf_label_len; 77 if (!CBB_init(&cbb, 2 + 1 + strlen(kTLS13LabelVersion) + label_len + 1 + 78 hash_len) || 79 !CBB_add_u16(&cbb, len) || 80 !CBB_add_u8_length_prefixed(&cbb, &child) || 81 !CBB_add_bytes(&child, (const uint8_t *)kTLS13LabelVersion, 82 strlen(kTLS13LabelVersion)) || 83 !CBB_add_bytes(&child, label, label_len) || 84 !CBB_add_u8_length_prefixed(&cbb, &child) || 85 !CBB_add_bytes(&child, hash, hash_len) || 86 !CBB_finish(&cbb, &hkdf_label, &hkdf_label_len)) { 87 CBB_cleanup(&cbb); 88 return 0; 89 } 90 91 int ret = HKDF_expand(out, len, digest, secret, secret_len, hkdf_label, 92 hkdf_label_len); 93 OPENSSL_free(hkdf_label); 94 return ret; 95 } 96 97 /* derive_secret derives a secret of length |len| and writes the result in |out| 98 * with the given label and the current base secret and most recently-saved 99 * handshake context. It returns one on success and zero on error. */ 100 static int derive_secret(SSL_HANDSHAKE *hs, uint8_t *out, size_t len, 101 const uint8_t *label, size_t label_len) { 102 uint8_t context_hash[EVP_MAX_MD_SIZE]; 103 size_t context_hash_len; 104 if (!SSL_TRANSCRIPT_get_hash(&hs->transcript, context_hash, 105 &context_hash_len)) { 106 return 0; 107 } 108 109 return hkdf_expand_label(out, SSL_TRANSCRIPT_md(&hs->transcript), hs->secret, 110 hs->hash_len, label, label_len, context_hash, 111 context_hash_len, len); 112 } 113 114 int tls13_set_traffic_key(SSL *ssl, enum evp_aead_direction_t direction, 115 const uint8_t *traffic_secret, 116 size_t traffic_secret_len) { 117 const SSL_SESSION *session = SSL_get_session(ssl); 118 uint16_t version = SSL_SESSION_protocol_version(session); 119 120 if (traffic_secret_len > 0xff) { 121 OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW); 122 return 0; 123 } 124 125 /* Look up cipher suite properties. */ 126 const EVP_AEAD *aead; 127 size_t discard; 128 if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, session->cipher, 129 version, SSL_is_dtls(ssl))) { 130 return 0; 131 } 132 133 const EVP_MD *digest = SSL_SESSION_get_digest(session); 134 135 /* Derive the key. */ 136 size_t key_len = EVP_AEAD_key_length(aead); 137 uint8_t key[EVP_AEAD_MAX_KEY_LENGTH]; 138 if (!hkdf_expand_label(key, digest, traffic_secret, traffic_secret_len, 139 (const uint8_t *)"key", 3, NULL, 0, key_len)) { 140 return 0; 141 } 142 143 /* Derive the IV. */ 144 size_t iv_len = EVP_AEAD_nonce_length(aead); 145 uint8_t iv[EVP_AEAD_MAX_NONCE_LENGTH]; 146 if (!hkdf_expand_label(iv, digest, traffic_secret, traffic_secret_len, 147 (const uint8_t *)"iv", 2, NULL, 0, iv_len)) { 148 return 0; 149 } 150 151 SSL_AEAD_CTX *traffic_aead = 152 SSL_AEAD_CTX_new(direction, version, SSL_is_dtls(ssl), session->cipher, 153 key, key_len, NULL, 0, iv, iv_len); 154 if (traffic_aead == NULL) { 155 return 0; 156 } 157 158 if (direction == evp_aead_open) { 159 if (!ssl->method->set_read_state(ssl, traffic_aead)) { 160 return 0; 161 } 162 } else { 163 if (!ssl->method->set_write_state(ssl, traffic_aead)) { 164 return 0; 165 } 166 } 167 168 /* Save the traffic secret. */ 169 if (direction == evp_aead_open) { 170 OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret, 171 traffic_secret_len); 172 ssl->s3->read_traffic_secret_len = traffic_secret_len; 173 } else { 174 OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret, 175 traffic_secret_len); 176 ssl->s3->write_traffic_secret_len = traffic_secret_len; 177 } 178 179 return 1; 180 } 181 182 static const char kTLS13LabelExporter[] = "exporter master secret"; 183 static const char kTLS13LabelEarlyExporter[] = "early exporter master secret"; 184 185 static const char kTLS13LabelClientEarlyTraffic[] = 186 "client early traffic secret"; 187 static const char kTLS13LabelClientHandshakeTraffic[] = 188 "client handshake traffic secret"; 189 static const char kTLS13LabelServerHandshakeTraffic[] = 190 "server handshake traffic secret"; 191 static const char kTLS13LabelClientApplicationTraffic[] = 192 "client application traffic secret"; 193 static const char kTLS13LabelServerApplicationTraffic[] = 194 "server application traffic secret"; 195 196 int tls13_derive_early_secrets(SSL_HANDSHAKE *hs) { 197 SSL *const ssl = hs->ssl; 198 return derive_secret(hs, hs->early_traffic_secret, hs->hash_len, 199 (const uint8_t *)kTLS13LabelClientEarlyTraffic, 200 strlen(kTLS13LabelClientEarlyTraffic)) && 201 ssl_log_secret(ssl, "CLIENT_EARLY_TRAFFIC_SECRET", 202 hs->early_traffic_secret, hs->hash_len) && 203 derive_secret(hs, ssl->s3->early_exporter_secret, hs->hash_len, 204 (const uint8_t *)kTLS13LabelEarlyExporter, 205 strlen(kTLS13LabelEarlyExporter)); 206 } 207 208 int tls13_derive_handshake_secrets(SSL_HANDSHAKE *hs) { 209 SSL *const ssl = hs->ssl; 210 return derive_secret(hs, hs->client_handshake_secret, hs->hash_len, 211 (const uint8_t *)kTLS13LabelClientHandshakeTraffic, 212 strlen(kTLS13LabelClientHandshakeTraffic)) && 213 ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET", 214 hs->client_handshake_secret, hs->hash_len) && 215 derive_secret(hs, hs->server_handshake_secret, hs->hash_len, 216 (const uint8_t *)kTLS13LabelServerHandshakeTraffic, 217 strlen(kTLS13LabelServerHandshakeTraffic)) && 218 ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET", 219 hs->server_handshake_secret, hs->hash_len); 220 } 221 222 int tls13_derive_application_secrets(SSL_HANDSHAKE *hs) { 223 SSL *const ssl = hs->ssl; 224 ssl->s3->exporter_secret_len = hs->hash_len; 225 return derive_secret(hs, hs->client_traffic_secret_0, hs->hash_len, 226 (const uint8_t *)kTLS13LabelClientApplicationTraffic, 227 strlen(kTLS13LabelClientApplicationTraffic)) && 228 ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0", 229 hs->client_traffic_secret_0, hs->hash_len) && 230 derive_secret(hs, hs->server_traffic_secret_0, hs->hash_len, 231 (const uint8_t *)kTLS13LabelServerApplicationTraffic, 232 strlen(kTLS13LabelServerApplicationTraffic)) && 233 ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0", 234 hs->server_traffic_secret_0, hs->hash_len) && 235 derive_secret(hs, ssl->s3->exporter_secret, hs->hash_len, 236 (const uint8_t *)kTLS13LabelExporter, 237 strlen(kTLS13LabelExporter)); 238 } 239 240 static const char kTLS13LabelApplicationTraffic[] = 241 "application traffic secret"; 242 243 int tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) { 244 const EVP_MD *digest = ssl_get_handshake_digest( 245 SSL_get_session(ssl)->cipher->algorithm_prf, ssl3_protocol_version(ssl)); 246 247 uint8_t *secret; 248 size_t secret_len; 249 if (direction == evp_aead_open) { 250 secret = ssl->s3->read_traffic_secret; 251 secret_len = ssl->s3->read_traffic_secret_len; 252 } else { 253 secret = ssl->s3->write_traffic_secret; 254 secret_len = ssl->s3->write_traffic_secret_len; 255 } 256 257 if (!hkdf_expand_label(secret, digest, secret, secret_len, 258 (const uint8_t *)kTLS13LabelApplicationTraffic, 259 strlen(kTLS13LabelApplicationTraffic), NULL, 0, 260 secret_len)) { 261 return 0; 262 } 263 264 return tls13_set_traffic_key(ssl, direction, secret, secret_len); 265 } 266 267 static const char kTLS13LabelResumption[] = "resumption master secret"; 268 269 int tls13_derive_resumption_secret(SSL_HANDSHAKE *hs) { 270 if (hs->hash_len > SSL_MAX_MASTER_KEY_LENGTH) { 271 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 272 return 0; 273 } 274 275 hs->new_session->master_key_length = hs->hash_len; 276 return derive_secret( 277 hs, hs->new_session->master_key, hs->new_session->master_key_length, 278 (const uint8_t *)kTLS13LabelResumption, strlen(kTLS13LabelResumption)); 279 } 280 281 static const char kTLS13LabelFinished[] = "finished"; 282 283 /* tls13_verify_data sets |out| to be the HMAC of |context| using a derived 284 * Finished key for both Finished messages and the PSK binder. */ 285 static int tls13_verify_data(const EVP_MD *digest, uint8_t *out, 286 size_t *out_len, const uint8_t *secret, 287 size_t hash_len, uint8_t *context, 288 size_t context_len) { 289 uint8_t key[EVP_MAX_MD_SIZE]; 290 unsigned len; 291 if (!hkdf_expand_label(key, digest, secret, hash_len, 292 (const uint8_t *)kTLS13LabelFinished, 293 strlen(kTLS13LabelFinished), NULL, 0, hash_len) || 294 HMAC(digest, key, hash_len, context, context_len, out, &len) == NULL) { 295 return 0; 296 } 297 *out_len = len; 298 return 1; 299 } 300 301 int tls13_finished_mac(SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len, 302 int is_server) { 303 const uint8_t *traffic_secret; 304 if (is_server) { 305 traffic_secret = hs->server_handshake_secret; 306 } else { 307 traffic_secret = hs->client_handshake_secret; 308 } 309 310 uint8_t context_hash[EVP_MAX_MD_SIZE]; 311 size_t context_hash_len; 312 if (!SSL_TRANSCRIPT_get_hash(&hs->transcript, context_hash, 313 &context_hash_len) || 314 !tls13_verify_data(SSL_TRANSCRIPT_md(&hs->transcript), out, out_len, 315 traffic_secret, hs->hash_len, context_hash, 316 context_hash_len)) { 317 return 0; 318 } 319 return 1; 320 } 321 322 int tls13_export_keying_material(SSL *ssl, uint8_t *out, size_t out_len, 323 const char *label, size_t label_len, 324 const uint8_t *context, size_t context_len, 325 int use_context) { 326 const EVP_MD *digest = ssl_get_handshake_digest( 327 SSL_get_session(ssl)->cipher->algorithm_prf, ssl3_protocol_version(ssl)); 328 329 const uint8_t *hash = NULL; 330 size_t hash_len = 0; 331 if (use_context) { 332 hash = context; 333 hash_len = context_len; 334 } 335 return hkdf_expand_label(out, digest, ssl->s3->exporter_secret, 336 ssl->s3->exporter_secret_len, (const uint8_t *)label, 337 label_len, hash, hash_len, out_len); 338 } 339 340 static const char kTLS13LabelPSKBinder[] = "resumption psk binder key"; 341 342 static int tls13_psk_binder(uint8_t *out, const EVP_MD *digest, uint8_t *psk, 343 size_t psk_len, uint8_t *context, 344 size_t context_len, size_t hash_len) { 345 uint8_t binder_context[EVP_MAX_MD_SIZE]; 346 unsigned binder_context_len; 347 if (!EVP_Digest(NULL, 0, binder_context, &binder_context_len, digest, NULL)) { 348 return 0; 349 } 350 351 uint8_t early_secret[EVP_MAX_MD_SIZE] = {0}; 352 size_t early_secret_len; 353 if (!HKDF_extract(early_secret, &early_secret_len, digest, psk, hash_len, 354 NULL, 0)) { 355 return 0; 356 } 357 358 uint8_t binder_key[EVP_MAX_MD_SIZE] = {0}; 359 size_t len; 360 if (!hkdf_expand_label(binder_key, digest, early_secret, hash_len, 361 (const uint8_t *)kTLS13LabelPSKBinder, 362 strlen(kTLS13LabelPSKBinder), binder_context, 363 binder_context_len, hash_len) || 364 !tls13_verify_data(digest, out, &len, binder_key, hash_len, context, 365 context_len)) { 366 return 0; 367 } 368 369 return 1; 370 } 371 372 int tls13_write_psk_binder(SSL_HANDSHAKE *hs, uint8_t *msg, size_t len) { 373 SSL *const ssl = hs->ssl; 374 const EVP_MD *digest = SSL_SESSION_get_digest(ssl->session); 375 size_t hash_len = EVP_MD_size(digest); 376 377 if (len < hash_len + 3) { 378 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 379 return 0; 380 } 381 382 EVP_MD_CTX ctx; 383 EVP_MD_CTX_init(&ctx); 384 uint8_t context[EVP_MAX_MD_SIZE]; 385 unsigned context_len; 386 if (!EVP_DigestInit_ex(&ctx, digest, NULL) || 387 !EVP_DigestUpdate(&ctx, hs->transcript.buffer->data, 388 hs->transcript.buffer->length) || 389 !EVP_DigestUpdate(&ctx, msg, len - hash_len - 3) || 390 !EVP_DigestFinal_ex(&ctx, context, &context_len)) { 391 EVP_MD_CTX_cleanup(&ctx); 392 return 0; 393 } 394 395 EVP_MD_CTX_cleanup(&ctx); 396 397 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; 398 if (!tls13_psk_binder(verify_data, digest, ssl->session->master_key, 399 ssl->session->master_key_length, context, context_len, 400 hash_len)) { 401 return 0; 402 } 403 404 OPENSSL_memcpy(msg + len - hash_len, verify_data, hash_len); 405 return 1; 406 } 407 408 int tls13_verify_psk_binder(SSL_HANDSHAKE *hs, SSL_SESSION *session, 409 CBS *binders) { 410 size_t hash_len = SSL_TRANSCRIPT_digest_len(&hs->transcript); 411 412 /* Get the full ClientHello, including message header. It must be large enough 413 * to exclude the binders. */ 414 CBS message; 415 hs->ssl->method->get_current_message(hs->ssl, &message); 416 if (CBS_len(&message) < CBS_len(binders) + 2) { 417 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 418 return 0; 419 } 420 421 /* Hash a ClientHello prefix up to the binders. For now, this assumes we only 422 * ever verify PSK binders on initial ClientHellos. */ 423 uint8_t context[EVP_MAX_MD_SIZE]; 424 unsigned context_len; 425 if (!EVP_Digest(CBS_data(&message), CBS_len(&message) - CBS_len(binders) - 2, 426 context, &context_len, SSL_TRANSCRIPT_md(&hs->transcript), 427 NULL)) { 428 return 0; 429 } 430 431 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; 432 CBS binder; 433 if (!tls13_psk_binder(verify_data, SSL_TRANSCRIPT_md(&hs->transcript), 434 session->master_key, session->master_key_length, 435 context, context_len, hash_len) || 436 /* We only consider the first PSK, so compare against the first binder. */ 437 !CBS_get_u8_length_prefixed(binders, &binder)) { 438 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); 439 return 0; 440 } 441 442 int binder_ok = 443 CBS_len(&binder) == hash_len && 444 CRYPTO_memcmp(CBS_data(&binder), verify_data, hash_len) == 0; 445 #if defined(BORINGSSL_UNSAFE_FUZZER_MODE) 446 binder_ok = 1; 447 #endif 448 if (!binder_ok) { 449 OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED); 450 return 0; 451 } 452 453 return 1; 454 } 455
