legacy-libs/grpc/deps/grpc/third_party/boringssl/ssl/tls13_enc.cc

   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