media/cdm/aes_decryptor.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/cdm/aes_decryptor.h"
   6
   7 #include <list>
   8 #include <vector>
   9
  10 #include "base/logging.h"
  11 #include "base/stl_util.h"
  12 #include "base/strings/string_number_conversions.h"
  13 #include "crypto/encryptor.h"
  14 #include "crypto/symmetric_key.h"
  15 #include "media/base/audio_decoder_config.h"
  16 #include "media/base/cdm_key_information.h"
  17 #include "media/base/cdm_promise.h"
  18 #include "media/base/decoder_buffer.h"
  19 #include "media/base/decrypt_config.h"
  20 #include "media/base/video_decoder_config.h"
  21 #include "media/base/video_frame.h"
  22 #include "media/cdm/cenc_utils.h"
  23 #include "media/cdm/json_web_key.h"
  24
  25 namespace media {
  26
  27 // Keeps track of the session IDs and DecryptionKeys. The keys are ordered by
  28 // insertion time (last insertion is first). It takes ownership of the
  29 // DecryptionKeys.
  30 class AesDecryptor::SessionIdDecryptionKeyMap {
  31   // Use a std::list to actually hold the data. Insertion is always done
  32   // at the front, so the "latest" decryption key is always the first one
  33   // in the list.
  34   typedef std::list<std::pair<std::string, DecryptionKey*> > KeyList;
  35
  36  public:
  37   SessionIdDecryptionKeyMap() {}
  38   ~SessionIdDecryptionKeyMap() { STLDeleteValues(&key_list_); }
  39
  40   // Replaces value if |session_id| is already present, or adds it if not.
  41   // This |decryption_key| becomes the latest until another insertion or
  42   // |session_id| is erased.
  43   void Insert(const std::string& session_id,
  44               scoped_ptr<DecryptionKey> decryption_key);
  45
  46   // Deletes the entry for |session_id| if present.
  47   void Erase(const std::string& session_id);
  48
  49   // Returns whether the list is empty
  50   bool Empty() const { return key_list_.empty(); }
  51
  52   // Returns the last inserted DecryptionKey.
  53   DecryptionKey* LatestDecryptionKey() {
  54     DCHECK(!key_list_.empty());
  55     return key_list_.begin()->second;
  56   }
  57
  58   bool Contains(const std::string& session_id) {
  59     return Find(session_id) != key_list_.end();
  60   }
  61
  62  private:
  63   // Searches the list for an element with |session_id|.
  64   KeyList::iterator Find(const std::string& session_id);
  65
  66   // Deletes the entry pointed to by |position|.
  67   void Erase(KeyList::iterator position);
  68
  69   KeyList key_list_;
  70
  71   DISALLOW_COPY_AND_ASSIGN(SessionIdDecryptionKeyMap);
  72 };
  73
  74 void AesDecryptor::SessionIdDecryptionKeyMap::Insert(
  75     const std::string& session_id,
  76     scoped_ptr<DecryptionKey> decryption_key) {
  77   KeyList::iterator it = Find(session_id);
  78   if (it != key_list_.end())
  79     Erase(it);
  80   DecryptionKey* raw_ptr = decryption_key.release();
  81   key_list_.push_front(std::make_pair(session_id, raw_ptr));
  82 }
  83
  84 void AesDecryptor::SessionIdDecryptionKeyMap::Erase(
  85     const std::string& session_id) {
  86   KeyList::iterator it = Find(session_id);
  87   if (it == key_list_.end())
  88     return;
  89   Erase(it);
  90 }
  91
  92 AesDecryptor::SessionIdDecryptionKeyMap::KeyList::iterator
  93 AesDecryptor::SessionIdDecryptionKeyMap::Find(const std::string& session_id) {
  94   for (KeyList::iterator it = key_list_.begin(); it != key_list_.end(); ++it) {
  95     if (it->first == session_id)
  96       return it;
  97   }
  98   return key_list_.end();
  99 }
 100
 101 void AesDecryptor::SessionIdDecryptionKeyMap::Erase(
 102     KeyList::iterator position) {
 103   DCHECK(position->second);
 104   delete position->second;
 105   key_list_.erase(position);
 106 }
 107
 108 uint32 AesDecryptor::next_session_id_ = 1;
 109
 110 enum ClearBytesBufferSel {
 111   kSrcContainsClearBytes,
 112   kDstContainsClearBytes
 113 };
 114
 115 static void CopySubsamples(const std::vector<SubsampleEntry>& subsamples,
 116                            const ClearBytesBufferSel sel,
 117                            const uint8* src,
 118                            uint8* dst) {
 119   for (size_t i = 0; i < subsamples.size(); i++) {
 120     const SubsampleEntry& subsample = subsamples[i];
 121     if (sel == kSrcContainsClearBytes) {
 122       src += subsample.clear_bytes;
 123     } else {
 124       dst += subsample.clear_bytes;
 125     }
 126     memcpy(dst, src, subsample.cypher_bytes);
 127     src += subsample.cypher_bytes;
 128     dst += subsample.cypher_bytes;
 129   }
 130 }
 131
 132 // Decrypts |input| using |key|.  Returns a DecoderBuffer with the decrypted
 133 // data if decryption succeeded or NULL if decryption failed.
 134 static scoped_refptr<DecoderBuffer> DecryptData(const DecoderBuffer& input,
 135                                                 crypto::SymmetricKey* key) {
 136   CHECK(input.data_size());
 137   CHECK(input.decrypt_config());
 138   CHECK(key);
 139
 140   crypto::Encryptor encryptor;
 141   if (!encryptor.Init(key, crypto::Encryptor::CTR, "")) {
 142     DVLOG(1) << "Could not initialize decryptor.";
 143     return NULL;
 144   }
 145
 146   DCHECK_EQ(input.decrypt_config()->iv().size(),
 147             static_cast<size_t>(DecryptConfig::kDecryptionKeySize));
 148   if (!encryptor.SetCounter(input.decrypt_config()->iv())) {
 149     DVLOG(1) << "Could not set counter block.";
 150     return NULL;
 151   }
 152
 153   const char* sample = reinterpret_cast<const char*>(input.data());
 154   size_t sample_size = static_cast<size_t>(input.data_size());
 155
 156   DCHECK_GT(sample_size, 0U) << "No sample data to be decrypted.";
 157   if (sample_size == 0)
 158     return NULL;
 159
 160   if (input.decrypt_config()->subsamples().empty()) {
 161     std::string decrypted_text;
 162     base::StringPiece encrypted_text(sample, sample_size);
 163     if (!encryptor.Decrypt(encrypted_text, &decrypted_text)) {
 164       DVLOG(1) << "Could not decrypt data.";
 165       return NULL;
 166     }
 167
 168     // TODO(xhwang): Find a way to avoid this data copy.
 169     return DecoderBuffer::CopyFrom(
 170         reinterpret_cast<const uint8*>(decrypted_text.data()),
 171         decrypted_text.size());
 172   }
 173
 174   const std::vector<SubsampleEntry>& subsamples =
 175       input.decrypt_config()->subsamples();
 176
 177   size_t total_clear_size = 0;
 178   size_t total_encrypted_size = 0;
 179   for (size_t i = 0; i < subsamples.size(); i++) {
 180     total_clear_size += subsamples[i].clear_bytes;
 181     total_encrypted_size += subsamples[i].cypher_bytes;
 182     // Check for overflow. This check is valid because *_size is unsigned.
 183     DCHECK(total_clear_size >= subsamples[i].clear_bytes);
 184     if (total_encrypted_size < subsamples[i].cypher_bytes)
 185       return NULL;
 186   }
 187   size_t total_size = total_clear_size + total_encrypted_size;
 188   if (total_size < total_clear_size || total_size != sample_size) {
 189     DVLOG(1) << "Subsample sizes do not equal input size";
 190     return NULL;
 191   }
 192
 193   // No need to decrypt if there is no encrypted data.
 194   if (total_encrypted_size <= 0) {
 195     return DecoderBuffer::CopyFrom(reinterpret_cast<const uint8*>(sample),
 196                                    sample_size);
 197   }
 198
 199   // The encrypted portions of all subsamples must form a contiguous block,
 200   // such that an encrypted subsample that ends away from a block boundary is
 201   // immediately followed by the start of the next encrypted subsample. We
 202   // copy all encrypted subsamples to a contiguous buffer, decrypt them, then
 203   // copy the decrypted bytes over the encrypted bytes in the output.
 204   // TODO(strobe): attempt to reduce number of memory copies
 205   scoped_ptr<uint8[]> encrypted_bytes(new uint8[total_encrypted_size]);
 206   CopySubsamples(subsamples, kSrcContainsClearBytes,
 207                  reinterpret_cast<const uint8*>(sample), encrypted_bytes.get());
 208
 209   base::StringPiece encrypted_text(
 210       reinterpret_cast<const char*>(encrypted_bytes.get()),
 211       total_encrypted_size);
 212   std::string decrypted_text;
 213   if (!encryptor.Decrypt(encrypted_text, &decrypted_text)) {
 214     DVLOG(1) << "Could not decrypt data.";
 215     return NULL;
 216   }
 217   DCHECK_EQ(decrypted_text.size(), encrypted_text.size());
 218
 219   scoped_refptr<DecoderBuffer> output = DecoderBuffer::CopyFrom(
 220       reinterpret_cast<const uint8*>(sample), sample_size);
 221   CopySubsamples(subsamples, kDstContainsClearBytes,
 222                  reinterpret_cast<const uint8*>(decrypted_text.data()),
 223                  output->writable_data());
 224   return output;
 225 }
 226
 227 AesDecryptor::AesDecryptor(const SessionMessageCB& session_message_cb,
 228                            const SessionClosedCB& session_closed_cb,
 229                            const SessionKeysChangeCB& session_keys_change_cb)
 230     : session_message_cb_(session_message_cb),
 231       session_closed_cb_(session_closed_cb),
 232       session_keys_change_cb_(session_keys_change_cb) {
 233   DCHECK(!session_message_cb_.is_null());
 234   DCHECK(!session_closed_cb_.is_null());
 235   DCHECK(!session_keys_change_cb_.is_null());
 236 }
 237
 238 AesDecryptor::~AesDecryptor() {
 239   key_map_.clear();
 240 }
 241
 242 void AesDecryptor::SetServerCertificate(const uint8* certificate_data,
 243                                         int certificate_data_length,
 244                                         scoped_ptr<SimpleCdmPromise> promise) {
 245   promise->reject(
 246       NOT_SUPPORTED_ERROR, 0, "SetServerCertificate() is not supported.");
 247 }
 248
 249 void AesDecryptor::CreateSessionAndGenerateRequest(
 250     SessionType session_type,
 251     const std::string& init_data_type,
 252     const uint8* init_data,
 253     int init_data_length,
 254     scoped_ptr<NewSessionCdmPromise> promise) {
 255   std::string session_id(base::UintToString(next_session_id_++));
 256   valid_sessions_.insert(session_id);
 257
 258   // For now, the AesDecryptor does not care about |session_type|.
 259   // TODO(jrummell): Validate |session_type|.
 260
 261   std::vector<uint8> message;
 262   // TODO(jrummell): Since unprefixed will never send NULL, remove this check
 263   // when prefixed EME is removed (http://crbug.com/249976).
 264   if (init_data && init_data_length) {
 265     std::vector<std::vector<uint8>> keys;
 266     if (init_data_type == "webm") {
 267       // |init_data| is simply the key needed.
 268       keys.push_back(
 269           std::vector<uint8>(init_data, init_data + init_data_length));
 270     } else if (init_data_type == "cenc") {
 271       // |init_data| is a set of 0 or more concatenated 'pssh' boxes.
 272       if (!GetKeyIdsForCommonSystemId(init_data, init_data_length, &keys)) {
 273         promise->reject(NOT_SUPPORTED_ERROR, 0, "No supported PSSH box found.");
 274         return;
 275       }
 276     } else {
 277       // TODO(jrummell): Support init_data_type == "keyids".
 278       promise->reject(NOT_SUPPORTED_ERROR, 0, "init_data_type not supported.");
 279       return;
 280     }
 281     CreateLicenseRequest(keys, session_type, &message);
 282   }
 283
 284   promise->resolve(session_id);
 285
 286   // No URL needed for license requests.
 287   session_message_cb_.Run(session_id, LICENSE_REQUEST, message,
 288                           GURL::EmptyGURL());
 289 }
 290
 291 void AesDecryptor::LoadSession(SessionType session_type,
 292                                const std::string& session_id,
 293                                scoped_ptr<NewSessionCdmPromise> promise) {
 294   // TODO(xhwang): Change this to NOTREACHED() when blink checks for key systems
 295   // that do not support loadSession. See http://crbug.com/342481
 296   promise->reject(NOT_SUPPORTED_ERROR, 0, "LoadSession() is not supported.");
 297 }
 298
 299 void AesDecryptor::UpdateSession(const std::string& session_id,
 300                                  const uint8* response,
 301                                  int response_length,
 302                                  scoped_ptr<SimpleCdmPromise> promise) {
 303   CHECK(response);
 304   CHECK_GT(response_length, 0);
 305
 306   // TODO(jrummell): Convert back to a DCHECK once prefixed EME is removed.
 307   if (valid_sessions_.find(session_id) == valid_sessions_.end()) {
 308     promise->reject(INVALID_ACCESS_ERROR, 0, "Session does not exist.");
 309     return;
 310   }
 311
 312   std::string key_string(reinterpret_cast<const char*>(response),
 313                          response_length);
 314
 315   KeyIdAndKeyPairs keys;
 316   SessionType session_type = MediaKeys::TEMPORARY_SESSION;
 317   if (!ExtractKeysFromJWKSet(key_string, &keys, &session_type)) {
 318     promise->reject(
 319         INVALID_ACCESS_ERROR, 0, "Response is not a valid JSON Web Key Set.");
 320     return;
 321   }
 322
 323   // Make sure that at least one key was extracted.
 324   if (keys.empty()) {
 325     promise->reject(
 326         INVALID_ACCESS_ERROR, 0, "Response does not contain any keys.");
 327     return;
 328   }
 329
 330   for (KeyIdAndKeyPairs::iterator it = keys.begin(); it != keys.end(); ++it) {
 331     if (it->second.length() !=
 332         static_cast<size_t>(DecryptConfig::kDecryptionKeySize)) {
 333       DVLOG(1) << "Invalid key length: " << it->second.length();
 334       promise->reject(INVALID_ACCESS_ERROR, 0, "Invalid key length.");
 335       return;
 336     }
 337     if (!AddDecryptionKey(session_id, it->first, it->second)) {
 338       promise->reject(INVALID_ACCESS_ERROR, 0, "Unable to add key.");
 339       return;
 340     }
 341   }
 342
 343   {
 344     base::AutoLock auto_lock(new_key_cb_lock_);
 345
 346     if (!new_audio_key_cb_.is_null())
 347       new_audio_key_cb_.Run();
 348
 349     if (!new_video_key_cb_.is_null())
 350       new_video_key_cb_.Run();
 351   }
 352
 353   promise->resolve();
 354
 355   // Create the list of all available keys for this session.
 356   CdmKeysInfo keys_info;
 357   {
 358     base::AutoLock auto_lock(key_map_lock_);
 359     for (const auto& item : key_map_) {
 360       if (item.second->Contains(session_id)) {
 361         scoped_ptr<CdmKeyInformation> key_info(new CdmKeyInformation);
 362         key_info->key_id.assign(item.first.begin(), item.first.end());
 363         key_info->status = CdmKeyInformation::USABLE;
 364         key_info->system_code = 0;
 365         keys_info.push_back(key_info.release());
 366       }
 367     }
 368   }
 369
 370   // Assume that at least 1 new key has been successfully added and thus
 371   // sending true for |has_additional_usable_key|. http://crbug.com/448219.
 372   session_keys_change_cb_.Run(session_id, true, keys_info.Pass());
 373 }
 374
 375 void AesDecryptor::CloseSession(const std::string& session_id,
 376                                 scoped_ptr<SimpleCdmPromise> promise) {
 377   // Validate that this is a reference to an active session and then forget it.
 378   std::set<std::string>::iterator it = valid_sessions_.find(session_id);
 379   DCHECK(it != valid_sessions_.end());
 380
 381   valid_sessions_.erase(it);
 382
 383   // Close the session.
 384   DeleteKeysForSession(session_id);
 385   promise->resolve();
 386   session_closed_cb_.Run(session_id);
 387 }
 388
 389 void AesDecryptor::RemoveSession(const std::string& session_id,
 390                                  scoped_ptr<SimpleCdmPromise> promise) {
 391   // AesDecryptor doesn't keep any persistent data, so this should be
 392   // NOT_REACHED().
 393   // TODO(jrummell): Make sure persistent session types are rejected.
 394   // http://crbug.com/384152.
 395   //
 396   // However, v0.1b calls to CancelKeyRequest() will call this, so close the
 397   // session, if it exists.
 398   // TODO(jrummell): Remove the close() call when prefixed EME is removed.
 399   // http://crbug.com/249976.
 400   if (valid_sessions_.find(session_id) != valid_sessions_.end()) {
 401     CloseSession(session_id, promise.Pass());
 402     return;
 403   }
 404
 405   promise->reject(INVALID_ACCESS_ERROR, 0, "Session does not exist.");
 406 }
 407
 408 CdmContext* AesDecryptor::GetCdmContext() {
 409   return this;
 410 }
 411
 412 Decryptor* AesDecryptor::GetDecryptor() {
 413   return this;
 414 }
 415
 416 #if defined(ENABLE_BROWSER_CDMS)
 417 int AesDecryptor::GetCdmId() const {
 418   return kInvalidCdmId;
 419 }
 420 #endif  // defined(ENABLE_BROWSER_CDMS)
 421
 422 void AesDecryptor::RegisterNewKeyCB(StreamType stream_type,
 423                                     const NewKeyCB& new_key_cb) {
 424   base::AutoLock auto_lock(new_key_cb_lock_);
 425
 426   switch (stream_type) {
 427     case kAudio:
 428       new_audio_key_cb_ = new_key_cb;
 429       break;
 430     case kVideo:
 431       new_video_key_cb_ = new_key_cb;
 432       break;
 433     default:
 434       NOTREACHED();
 435   }
 436 }
 437
 438 void AesDecryptor::Decrypt(StreamType stream_type,
 439                            const scoped_refptr<DecoderBuffer>& encrypted,
 440                            const DecryptCB& decrypt_cb) {
 441   CHECK(encrypted->decrypt_config());
 442
 443   scoped_refptr<DecoderBuffer> decrypted;
 444   // An empty iv string signals that the frame is unencrypted.
 445   if (encrypted->decrypt_config()->iv().empty()) {
 446     decrypted = DecoderBuffer::CopyFrom(encrypted->data(),
 447                                         encrypted->data_size());
 448   } else {
 449     const std::string& key_id = encrypted->decrypt_config()->key_id();
 450     DecryptionKey* key = GetKey(key_id);
 451     if (!key) {
 452       DVLOG(1) << "Could not find a matching key for the given key ID.";
 453       decrypt_cb.Run(kNoKey, NULL);
 454       return;
 455     }
 456
 457     crypto::SymmetricKey* decryption_key = key->decryption_key();
 458     decrypted = DecryptData(*encrypted.get(), decryption_key);
 459     if (!decrypted.get()) {
 460       DVLOG(1) << "Decryption failed.";
 461       decrypt_cb.Run(kError, NULL);
 462       return;
 463     }
 464   }
 465
 466   decrypted->set_timestamp(encrypted->timestamp());
 467   decrypted->set_duration(encrypted->duration());
 468   decrypt_cb.Run(kSuccess, decrypted);
 469 }
 470
 471 void AesDecryptor::CancelDecrypt(StreamType stream_type) {
 472   // Decrypt() calls the DecryptCB synchronously so there's nothing to cancel.
 473 }
 474
 475 void AesDecryptor::InitializeAudioDecoder(const AudioDecoderConfig& config,
 476                                           const DecoderInitCB& init_cb) {
 477   // AesDecryptor does not support audio decoding.
 478   init_cb.Run(false);
 479 }
 480
 481 void AesDecryptor::InitializeVideoDecoder(const VideoDecoderConfig& config,
 482                                           const DecoderInitCB& init_cb) {
 483   // AesDecryptor does not support video decoding.
 484   init_cb.Run(false);
 485 }
 486
 487 void AesDecryptor::DecryptAndDecodeAudio(
 488     const scoped_refptr<DecoderBuffer>& encrypted,
 489     const AudioDecodeCB& audio_decode_cb) {
 490   NOTREACHED() << "AesDecryptor does not support audio decoding";
 491 }
 492
 493 void AesDecryptor::DecryptAndDecodeVideo(
 494     const scoped_refptr<DecoderBuffer>& encrypted,
 495     const VideoDecodeCB& video_decode_cb) {
 496   NOTREACHED() << "AesDecryptor does not support video decoding";
 497 }
 498
 499 void AesDecryptor::ResetDecoder(StreamType stream_type) {
 500   NOTREACHED() << "AesDecryptor does not support audio/video decoding";
 501 }
 502
 503 void AesDecryptor::DeinitializeDecoder(StreamType stream_type) {
 504   NOTREACHED() << "AesDecryptor does not support audio/video decoding";
 505 }
 506
 507 bool AesDecryptor::AddDecryptionKey(const std::string& session_id,
 508                                     const std::string& key_id,
 509                                     const std::string& key_string) {
 510   scoped_ptr<DecryptionKey> decryption_key(new DecryptionKey(key_string));
 511   if (!decryption_key->Init()) {
 512     DVLOG(1) << "Could not initialize decryption key.";
 513     return false;
 514   }
 515
 516   base::AutoLock auto_lock(key_map_lock_);
 517   KeyIdToSessionKeysMap::iterator key_id_entry = key_map_.find(key_id);
 518   if (key_id_entry != key_map_.end()) {
 519     key_id_entry->second->Insert(session_id, decryption_key.Pass());
 520     return true;
 521   }
 522
 523   // |key_id| not found, so need to create new entry.
 524   scoped_ptr<SessionIdDecryptionKeyMap> inner_map(
 525       new SessionIdDecryptionKeyMap());
 526   inner_map->Insert(session_id, decryption_key.Pass());
 527   key_map_.add(key_id, inner_map.Pass());
 528   return true;
 529 }
 530
 531 AesDecryptor::DecryptionKey* AesDecryptor::GetKey(
 532     const std::string& key_id) const {
 533   base::AutoLock auto_lock(key_map_lock_);
 534   KeyIdToSessionKeysMap::const_iterator key_id_found = key_map_.find(key_id);
 535   if (key_id_found == key_map_.end())
 536     return NULL;
 537
 538   // Return the key from the "latest" session_id entry.
 539   return key_id_found->second->LatestDecryptionKey();
 540 }
 541
 542 void AesDecryptor::DeleteKeysForSession(const std::string& session_id) {
 543   base::AutoLock auto_lock(key_map_lock_);
 544
 545   // Remove all keys associated with |session_id|. Since the data is
 546   // optimized for access in GetKey(), we need to look at each entry in
 547   // |key_map_|.
 548   KeyIdToSessionKeysMap::iterator it = key_map_.begin();
 549   while (it != key_map_.end()) {
 550     it->second->Erase(session_id);
 551     if (it->second->Empty()) {
 552       // Need to get rid of the entry for this key_id. This will mess up the
 553       // iterator, so we need to increment it first.
 554       KeyIdToSessionKeysMap::iterator current = it;
 555       ++it;
 556       key_map_.erase(current);
 557     } else {
 558       ++it;
 559     }
 560   }
 561 }
 562
 563 AesDecryptor::DecryptionKey::DecryptionKey(const std::string& secret)
 564     : secret_(secret) {
 565 }
 566
 567 AesDecryptor::DecryptionKey::~DecryptionKey() {}
 568
 569 bool AesDecryptor::DecryptionKey::Init() {
 570   CHECK(!secret_.empty());
 571   decryption_key_.reset(crypto::SymmetricKey::Import(
 572       crypto::SymmetricKey::AES, secret_));
 573   if (!decryption_key_)
 574     return false;
 575   return true;
 576 }
 577
 578 }  // namespace media