| 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 | BSSL_NAMESPACE_BEGIN |
| 34 | |
| 35 | static bool init_key_schedule(SSL_HANDSHAKE *hs, uint16_t version, |
| 36 | const SSL_CIPHER *cipher) { |
| 37 | if (!hs->transcript.InitHash(version, cipher)) { |
| 38 | return false; |
| 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 true; |
| 47 | } |
| 48 | |
| 49 | bool 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 false; |
| 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 | bool 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.get()), |
| 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 bool 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, |
| 73 | size_t len) { |
| 74 | static const char kTLS13ProtocolLabel[] = "tls13 " ; |
| 75 | |
| 76 | ScopedCBB cbb; |
| 77 | CBB child; |
| 78 | Array<uint8_t> hkdf_label; |
| 79 | if (!CBB_init(cbb.get(), 2 + 1 + strlen(kTLS13ProtocolLabel) + 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 *)kTLS13ProtocolLabel, |
| 84 | strlen(kTLS13ProtocolLabel)) || |
| 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 | !CBBFinishArray(cbb.get(), &hkdf_label)) { |
| 89 | return false; |
| 90 | } |
| 91 | |
| 92 | return HKDF_expand(out, len, digest, secret, secret_len, hkdf_label.data(), |
| 93 | hkdf_label.size()); |
| 94 | } |
| 95 | |
| 96 | static const char kTLS13LabelDerived[] = "derived" ; |
| 97 | |
| 98 | bool tls13_advance_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *in, |
| 99 | size_t len) { |
| 100 | uint8_t derive_context[EVP_MAX_MD_SIZE]; |
| 101 | unsigned derive_context_len; |
| 102 | if (!EVP_Digest(nullptr, 0, derive_context, &derive_context_len, |
| 103 | hs->transcript.Digest(), nullptr)) { |
| 104 | return false; |
| 105 | } |
| 106 | |
| 107 | if (!hkdf_expand_label(hs->secret, hs->transcript.Digest(), hs->secret, |
| 108 | hs->hash_len, kTLS13LabelDerived, |
| 109 | strlen(kTLS13LabelDerived), derive_context, |
| 110 | derive_context_len, hs->hash_len)) { |
| 111 | return false; |
| 112 | } |
| 113 | |
| 114 | return HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), in, |
| 115 | len, hs->secret, hs->hash_len); |
| 116 | } |
| 117 | |
| 118 | // derive_secret derives a secret of length |len| and writes the result in |out| |
| 119 | // with the given label and the current base secret and most recently-saved |
| 120 | // handshake context. It returns true on success and false on error. |
| 121 | static bool derive_secret(SSL_HANDSHAKE *hs, uint8_t *out, size_t len, |
| 122 | const char *label, size_t label_len) { |
| 123 | uint8_t context_hash[EVP_MAX_MD_SIZE]; |
| 124 | size_t context_hash_len; |
| 125 | if (!hs->transcript.GetHash(context_hash, &context_hash_len)) { |
| 126 | return false; |
| 127 | } |
| 128 | |
| 129 | return hkdf_expand_label(out, hs->transcript.Digest(), hs->secret, |
| 130 | hs->hash_len, label, label_len, context_hash, |
| 131 | context_hash_len, len); |
| 132 | } |
| 133 | |
| 134 | bool tls13_set_traffic_key(SSL *ssl, enum ssl_encryption_level_t level, |
| 135 | enum evp_aead_direction_t direction, |
| 136 | const uint8_t *traffic_secret, |
| 137 | size_t traffic_secret_len) { |
| 138 | const SSL_SESSION *session = SSL_get_session(ssl); |
| 139 | uint16_t version = ssl_session_protocol_version(session); |
| 140 | |
| 141 | if (traffic_secret_len > 0xff) { |
| 142 | OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW); |
| 143 | return false; |
| 144 | } |
| 145 | |
| 146 | UniquePtr<SSLAEADContext> traffic_aead; |
| 147 | if (ssl->quic_method == nullptr) { |
| 148 | // Look up cipher suite properties. |
| 149 | const EVP_AEAD *aead; |
| 150 | size_t discard; |
| 151 | if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, session->cipher, |
| 152 | version, SSL_is_dtls(ssl))) { |
| 153 | return false; |
| 154 | } |
| 155 | |
| 156 | const EVP_MD *digest = ssl_session_get_digest(session); |
| 157 | |
| 158 | // Derive the key. |
| 159 | size_t key_len = EVP_AEAD_key_length(aead); |
| 160 | uint8_t key[EVP_AEAD_MAX_KEY_LENGTH]; |
| 161 | if (!hkdf_expand_label(key, digest, traffic_secret, traffic_secret_len, |
| 162 | "key" , 3, NULL, 0, key_len)) { |
| 163 | return false; |
| 164 | } |
| 165 | |
| 166 | // Derive the IV. |
| 167 | size_t iv_len = EVP_AEAD_nonce_length(aead); |
| 168 | uint8_t iv[EVP_AEAD_MAX_NONCE_LENGTH]; |
| 169 | if (!hkdf_expand_label(iv, digest, traffic_secret, traffic_secret_len, "iv" , |
| 170 | 2, NULL, 0, iv_len)) { |
| 171 | return false; |
| 172 | } |
| 173 | |
| 174 | |
| 175 | traffic_aead = SSLAEADContext::Create( |
| 176 | direction, session->ssl_version, SSL_is_dtls(ssl), session->cipher, |
| 177 | MakeConstSpan(key, key_len), Span<const uint8_t>(), |
| 178 | MakeConstSpan(iv, iv_len)); |
| 179 | } else { |
| 180 | // Install a placeholder SSLAEADContext so that SSL accessors work. The |
| 181 | // encryption itself will be handled by the SSL_QUIC_METHOD. |
| 182 | traffic_aead = |
| 183 | SSLAEADContext::CreatePlaceholderForQUIC(version, session->cipher); |
| 184 | } |
| 185 | |
| 186 | if (!traffic_aead) { |
| 187 | return false; |
| 188 | } |
| 189 | |
| 190 | if (direction == evp_aead_open) { |
| 191 | if (!ssl->method->set_read_state(ssl, std::move(traffic_aead))) { |
| 192 | return false; |
| 193 | } |
| 194 | } else { |
| 195 | if (!ssl->method->set_write_state(ssl, std::move(traffic_aead))) { |
| 196 | return false; |
| 197 | } |
| 198 | } |
| 199 | |
| 200 | // Save the traffic secret. |
| 201 | if (direction == evp_aead_open) { |
| 202 | OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret, |
| 203 | traffic_secret_len); |
| 204 | ssl->s3->read_traffic_secret_len = traffic_secret_len; |
| 205 | ssl->s3->read_level = level; |
| 206 | } else { |
| 207 | OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret, |
| 208 | traffic_secret_len); |
| 209 | ssl->s3->write_traffic_secret_len = traffic_secret_len; |
| 210 | ssl->s3->write_level = level; |
| 211 | } |
| 212 | |
| 213 | return true; |
| 214 | } |
| 215 | |
| 216 | |
| 217 | static const char kTLS13LabelExporter[] = "exp master" ; |
| 218 | static const char kTLS13LabelEarlyExporter[] = "e exp master" ; |
| 219 | |
| 220 | static const char kTLS13LabelClientEarlyTraffic[] = "c e traffic" ; |
| 221 | static const char kTLS13LabelClientHandshakeTraffic[] = "c hs traffic" ; |
| 222 | static const char kTLS13LabelServerHandshakeTraffic[] = "s hs traffic" ; |
| 223 | static const char kTLS13LabelClientApplicationTraffic[] = "c ap traffic" ; |
| 224 | static const char kTLS13LabelServerApplicationTraffic[] = "s ap traffic" ; |
| 225 | |
| 226 | bool tls13_derive_early_secrets(SSL_HANDSHAKE *hs) { |
| 227 | SSL *const ssl = hs->ssl; |
| 228 | if (!derive_secret(hs, hs->early_traffic_secret, hs->hash_len, |
| 229 | kTLS13LabelClientEarlyTraffic, |
| 230 | strlen(kTLS13LabelClientEarlyTraffic)) || |
| 231 | !ssl_log_secret(ssl, "CLIENT_EARLY_TRAFFIC_SECRET" , |
| 232 | hs->early_traffic_secret, hs->hash_len) || |
| 233 | !derive_secret(hs, ssl->s3->early_exporter_secret, hs->hash_len, |
| 234 | kTLS13LabelEarlyExporter, |
| 235 | strlen(kTLS13LabelEarlyExporter))) { |
| 236 | return false; |
| 237 | } |
| 238 | ssl->s3->early_exporter_secret_len = hs->hash_len; |
| 239 | |
| 240 | if (ssl->quic_method != nullptr) { |
| 241 | if (ssl->server) { |
| 242 | if (!ssl->quic_method->set_encryption_secrets( |
| 243 | ssl, ssl_encryption_early_data, nullptr, hs->early_traffic_secret, |
| 244 | hs->hash_len)) { |
| 245 | OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR); |
| 246 | return false; |
| 247 | } |
| 248 | } else { |
| 249 | if (!ssl->quic_method->set_encryption_secrets( |
| 250 | ssl, ssl_encryption_early_data, hs->early_traffic_secret, nullptr, |
| 251 | hs->hash_len)) { |
| 252 | OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR); |
| 253 | return false; |
| 254 | } |
| 255 | } |
| 256 | } |
| 257 | |
| 258 | return true; |
| 259 | } |
| 260 | |
| 261 | bool tls13_derive_handshake_secrets(SSL_HANDSHAKE *hs) { |
| 262 | SSL *const ssl = hs->ssl; |
| 263 | if (!derive_secret(hs, hs->client_handshake_secret, hs->hash_len, |
| 264 | kTLS13LabelClientHandshakeTraffic, |
| 265 | strlen(kTLS13LabelClientHandshakeTraffic)) || |
| 266 | !ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET" , |
| 267 | hs->client_handshake_secret, hs->hash_len) || |
| 268 | !derive_secret(hs, hs->server_handshake_secret, hs->hash_len, |
| 269 | kTLS13LabelServerHandshakeTraffic, |
| 270 | strlen(kTLS13LabelServerHandshakeTraffic)) || |
| 271 | !ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET" , |
| 272 | hs->server_handshake_secret, hs->hash_len)) { |
| 273 | return false; |
| 274 | } |
| 275 | |
| 276 | if (ssl->quic_method != nullptr) { |
| 277 | if (ssl->server) { |
| 278 | if (!ssl->quic_method->set_encryption_secrets( |
| 279 | ssl, ssl_encryption_handshake, hs->client_handshake_secret, |
| 280 | hs->server_handshake_secret, hs->hash_len)) { |
| 281 | OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR); |
| 282 | return false; |
| 283 | } |
| 284 | } else { |
| 285 | if (!ssl->quic_method->set_encryption_secrets( |
| 286 | ssl, ssl_encryption_handshake, hs->server_handshake_secret, |
| 287 | hs->client_handshake_secret, hs->hash_len)) { |
| 288 | OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR); |
| 289 | return false; |
| 290 | } |
| 291 | } |
| 292 | } |
| 293 | |
| 294 | return true; |
| 295 | } |
| 296 | |
| 297 | bool tls13_derive_application_secrets(SSL_HANDSHAKE *hs) { |
| 298 | SSL *const ssl = hs->ssl; |
| 299 | ssl->s3->exporter_secret_len = hs->hash_len; |
| 300 | if (!derive_secret(hs, hs->client_traffic_secret_0, hs->hash_len, |
| 301 | kTLS13LabelClientApplicationTraffic, |
| 302 | strlen(kTLS13LabelClientApplicationTraffic)) || |
| 303 | !ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0" , |
| 304 | hs->client_traffic_secret_0, hs->hash_len) || |
| 305 | !derive_secret(hs, hs->server_traffic_secret_0, hs->hash_len, |
| 306 | kTLS13LabelServerApplicationTraffic, |
| 307 | strlen(kTLS13LabelServerApplicationTraffic)) || |
| 308 | !ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0" , |
| 309 | hs->server_traffic_secret_0, hs->hash_len) || |
| 310 | !derive_secret(hs, ssl->s3->exporter_secret, hs->hash_len, |
| 311 | kTLS13LabelExporter, strlen(kTLS13LabelExporter)) || |
| 312 | !ssl_log_secret(ssl, "EXPORTER_SECRET" , ssl->s3->exporter_secret, |
| 313 | hs->hash_len)) { |
| 314 | return false; |
| 315 | } |
| 316 | |
| 317 | if (ssl->quic_method != nullptr) { |
| 318 | if (ssl->server) { |
| 319 | if (!ssl->quic_method->set_encryption_secrets( |
| 320 | ssl, ssl_encryption_application, hs->client_traffic_secret_0, |
| 321 | hs->server_traffic_secret_0, hs->hash_len)) { |
| 322 | OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR); |
| 323 | return false; |
| 324 | } |
| 325 | } else { |
| 326 | if (!ssl->quic_method->set_encryption_secrets( |
| 327 | ssl, ssl_encryption_application, hs->server_traffic_secret_0, |
| 328 | hs->client_traffic_secret_0, hs->hash_len)) { |
| 329 | OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR); |
| 330 | return false; |
| 331 | } |
| 332 | } |
| 333 | } |
| 334 | |
| 335 | return true; |
| 336 | } |
| 337 | |
| 338 | static const char kTLS13LabelApplicationTraffic[] = "traffic upd" ; |
| 339 | |
| 340 | bool tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) { |
| 341 | uint8_t *secret; |
| 342 | size_t secret_len; |
| 343 | if (direction == evp_aead_open) { |
| 344 | secret = ssl->s3->read_traffic_secret; |
| 345 | secret_len = ssl->s3->read_traffic_secret_len; |
| 346 | } else { |
| 347 | secret = ssl->s3->write_traffic_secret; |
| 348 | secret_len = ssl->s3->write_traffic_secret_len; |
| 349 | } |
| 350 | |
| 351 | const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl)); |
| 352 | if (!hkdf_expand_label(secret, digest, secret, secret_len, |
| 353 | kTLS13LabelApplicationTraffic, |
| 354 | strlen(kTLS13LabelApplicationTraffic), NULL, 0, |
| 355 | secret_len)) { |
| 356 | return false; |
| 357 | } |
| 358 | |
| 359 | return tls13_set_traffic_key(ssl, ssl_encryption_application, direction, |
| 360 | secret, secret_len); |
| 361 | } |
| 362 | |
| 363 | static const char kTLS13LabelResumption[] = "res master" ; |
| 364 | |
| 365 | bool tls13_derive_resumption_secret(SSL_HANDSHAKE *hs) { |
| 366 | if (hs->hash_len > SSL_MAX_MASTER_KEY_LENGTH) { |
| 367 | OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| 368 | return false; |
| 369 | } |
| 370 | hs->new_session->master_key_length = hs->hash_len; |
| 371 | return derive_secret(hs, hs->new_session->master_key, |
| 372 | hs->new_session->master_key_length, |
| 373 | kTLS13LabelResumption, strlen(kTLS13LabelResumption)); |
| 374 | } |
| 375 | |
| 376 | static const char kTLS13LabelFinished[] = "finished" ; |
| 377 | |
| 378 | // tls13_verify_data sets |out| to be the HMAC of |context| using a derived |
| 379 | // Finished key for both Finished messages and the PSK binder. |
| 380 | static bool tls13_verify_data(const EVP_MD *digest, uint16_t version, |
| 381 | uint8_t *out, size_t *out_len, |
| 382 | const uint8_t *secret, size_t hash_len, |
| 383 | uint8_t *context, size_t context_len) { |
| 384 | uint8_t key[EVP_MAX_MD_SIZE]; |
| 385 | unsigned len; |
| 386 | if (!hkdf_expand_label(key, digest, secret, hash_len, kTLS13LabelFinished, |
| 387 | strlen(kTLS13LabelFinished), NULL, 0, hash_len) || |
| 388 | HMAC(digest, key, hash_len, context, context_len, out, &len) == NULL) { |
| 389 | return false; |
| 390 | } |
| 391 | *out_len = len; |
| 392 | return true; |
| 393 | } |
| 394 | |
| 395 | bool tls13_finished_mac(SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len, |
| 396 | bool is_server) { |
| 397 | const uint8_t *traffic_secret; |
| 398 | if (is_server) { |
| 399 | traffic_secret = hs->server_handshake_secret; |
| 400 | } else { |
| 401 | traffic_secret = hs->client_handshake_secret; |
| 402 | } |
| 403 | |
| 404 | uint8_t context_hash[EVP_MAX_MD_SIZE]; |
| 405 | size_t context_hash_len; |
| 406 | if (!hs->transcript.GetHash(context_hash, &context_hash_len) || |
| 407 | !tls13_verify_data(hs->transcript.Digest(), hs->ssl->version, out, |
| 408 | out_len, traffic_secret, hs->hash_len, context_hash, |
| 409 | context_hash_len)) { |
| 410 | return 0; |
| 411 | } |
| 412 | return 1; |
| 413 | } |
| 414 | |
| 415 | static const char kTLS13LabelResumptionPSK[] = "resumption" ; |
| 416 | |
| 417 | bool tls13_derive_session_psk(SSL_SESSION *session, Span<const uint8_t> nonce) { |
| 418 | const EVP_MD *digest = ssl_session_get_digest(session); |
| 419 | return hkdf_expand_label(session->master_key, digest, session->master_key, |
| 420 | session->master_key_length, kTLS13LabelResumptionPSK, |
| 421 | strlen(kTLS13LabelResumptionPSK), nonce.data(), |
| 422 | nonce.size(), session->master_key_length); |
| 423 | } |
| 424 | |
| 425 | static const char kTLS13LabelExportKeying[] = "exporter" ; |
| 426 | |
| 427 | bool tls13_export_keying_material(SSL *ssl, Span<uint8_t> out, |
| 428 | Span<const uint8_t> secret, |
| 429 | Span<const char> label, |
| 430 | Span<const uint8_t> context) { |
| 431 | if (secret.empty()) { |
| 432 | assert(0); |
| 433 | OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| 434 | return false; |
| 435 | } |
| 436 | |
| 437 | const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl)); |
| 438 | |
| 439 | uint8_t hash[EVP_MAX_MD_SIZE]; |
| 440 | uint8_t export_context[EVP_MAX_MD_SIZE]; |
| 441 | uint8_t derived_secret[EVP_MAX_MD_SIZE]; |
| 442 | unsigned hash_len; |
| 443 | unsigned export_context_len; |
| 444 | unsigned derived_secret_len = EVP_MD_size(digest); |
| 445 | return EVP_Digest(context.data(), context.size(), hash, &hash_len, digest, |
| 446 | nullptr) && |
| 447 | EVP_Digest(nullptr, 0, export_context, &export_context_len, digest, |
| 448 | nullptr) && |
| 449 | hkdf_expand_label(derived_secret, digest, secret.data(), secret.size(), |
| 450 | label.data(), label.size(), export_context, |
| 451 | export_context_len, derived_secret_len) && |
| 452 | hkdf_expand_label(out.data(), digest, derived_secret, |
| 453 | derived_secret_len, kTLS13LabelExportKeying, |
| 454 | strlen(kTLS13LabelExportKeying), hash, hash_len, |
| 455 | out.size()); |
| 456 | } |
| 457 | |
| 458 | static const char kTLS13LabelPSKBinder[] = "res binder" ; |
| 459 | |
| 460 | static bool tls13_psk_binder(uint8_t *out, uint16_t version, |
| 461 | const EVP_MD *digest, uint8_t *psk, size_t psk_len, |
| 462 | uint8_t *context, size_t context_len, |
| 463 | size_t hash_len) { |
| 464 | uint8_t binder_context[EVP_MAX_MD_SIZE]; |
| 465 | unsigned binder_context_len; |
| 466 | if (!EVP_Digest(NULL, 0, binder_context, &binder_context_len, digest, NULL)) { |
| 467 | return false; |
| 468 | } |
| 469 | |
| 470 | uint8_t early_secret[EVP_MAX_MD_SIZE] = {0}; |
| 471 | size_t early_secret_len; |
| 472 | if (!HKDF_extract(early_secret, &early_secret_len, digest, psk, hash_len, |
| 473 | NULL, 0)) { |
| 474 | return false; |
| 475 | } |
| 476 | |
| 477 | uint8_t binder_key[EVP_MAX_MD_SIZE] = {0}; |
| 478 | size_t len; |
| 479 | if (!hkdf_expand_label(binder_key, digest, early_secret, hash_len, |
| 480 | kTLS13LabelPSKBinder, strlen(kTLS13LabelPSKBinder), |
| 481 | binder_context, binder_context_len, hash_len) || |
| 482 | !tls13_verify_data(digest, version, out, &len, binder_key, hash_len, |
| 483 | context, context_len)) { |
| 484 | return false; |
| 485 | } |
| 486 | |
| 487 | return true; |
| 488 | } |
| 489 | |
| 490 | bool tls13_write_psk_binder(SSL_HANDSHAKE *hs, uint8_t *msg, size_t len) { |
| 491 | SSL *const ssl = hs->ssl; |
| 492 | const EVP_MD *digest = ssl_session_get_digest(ssl->session.get()); |
| 493 | size_t hash_len = EVP_MD_size(digest); |
| 494 | |
| 495 | if (len < hash_len + 3) { |
| 496 | OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| 497 | return false; |
| 498 | } |
| 499 | |
| 500 | ScopedEVP_MD_CTX ctx; |
| 501 | uint8_t context[EVP_MAX_MD_SIZE]; |
| 502 | unsigned context_len; |
| 503 | |
| 504 | if (!EVP_DigestInit_ex(ctx.get(), digest, NULL) || |
| 505 | !EVP_DigestUpdate(ctx.get(), hs->transcript.buffer().data(), |
| 506 | hs->transcript.buffer().size()) || |
| 507 | !EVP_DigestUpdate(ctx.get(), msg, len - hash_len - 3) || |
| 508 | !EVP_DigestFinal_ex(ctx.get(), context, &context_len)) { |
| 509 | return false; |
| 510 | } |
| 511 | |
| 512 | uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; |
| 513 | if (!tls13_psk_binder(verify_data, ssl->session->ssl_version, digest, |
| 514 | ssl->session->master_key, |
| 515 | ssl->session->master_key_length, context, context_len, |
| 516 | hash_len)) { |
| 517 | return false; |
| 518 | } |
| 519 | |
| 520 | OPENSSL_memcpy(msg + len - hash_len, verify_data, hash_len); |
| 521 | return true; |
| 522 | } |
| 523 | |
| 524 | bool tls13_verify_psk_binder(SSL_HANDSHAKE *hs, SSL_SESSION *session, |
| 525 | const SSLMessage &msg, CBS *binders) { |
| 526 | size_t hash_len = hs->transcript.DigestLen(); |
| 527 | |
| 528 | // The message must be large enough to exclude the binders. |
| 529 | if (CBS_len(&msg.raw) < CBS_len(binders) + 2) { |
| 530 | OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| 531 | return false; |
| 532 | } |
| 533 | |
| 534 | // Hash a ClientHello prefix up to the binders. This includes the header. For |
| 535 | // now, this assumes we only ever verify PSK binders on initial |
| 536 | // ClientHellos. |
| 537 | uint8_t context[EVP_MAX_MD_SIZE]; |
| 538 | unsigned context_len; |
| 539 | if (!EVP_Digest(CBS_data(&msg.raw), CBS_len(&msg.raw) - CBS_len(binders) - 2, |
| 540 | context, &context_len, hs->transcript.Digest(), NULL)) { |
| 541 | return false; |
| 542 | } |
| 543 | |
| 544 | uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; |
| 545 | CBS binder; |
| 546 | if (!tls13_psk_binder(verify_data, hs->ssl->version, hs->transcript.Digest(), |
| 547 | session->master_key, session->master_key_length, |
| 548 | context, context_len, hash_len) || |
| 549 | // We only consider the first PSK, so compare against the first binder. |
| 550 | !CBS_get_u8_length_prefixed(binders, &binder)) { |
| 551 | OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); |
| 552 | return false; |
| 553 | } |
| 554 | |
| 555 | bool binder_ok = CBS_len(&binder) == hash_len && |
| 556 | CRYPTO_memcmp(CBS_data(&binder), verify_data, hash_len) == 0; |
| 557 | #if defined(BORINGSSL_UNSAFE_FUZZER_MODE) |
| 558 | binder_ok = true; |
| 559 | #endif |
| 560 | if (!binder_ok) { |
| 561 | OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED); |
| 562 | return false; |
| 563 | } |
| 564 | |
| 565 | return true; |
| 566 | } |
| 567 | |
| 568 | BSSL_NAMESPACE_END |
| 569 | |