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 if (init_data_type == "keyids") {
 277       std::string init_data_string(init_data, init_data + init_data_length);
 278       std::string error_message;
 279       if (!ExtractKeyIdsFromKeyIdsInitData(init_data_string, &keys,
 280                                            &error_message)) {
 281         promise->reject(NOT_SUPPORTED_ERROR, 0, error_message);
 282         return;
 283       }
 284     } else {
 285       promise->reject(NOT_SUPPORTED_ERROR, 0, "init_data_type not supported.");
 286       return;
 287     }
 288     CreateLicenseRequest(keys, session_type, &message);
 289   }
 290
 291   promise->resolve(session_id);
 292
 293   // No URL needed for license requests.
 294   session_message_cb_.Run(session_id, LICENSE_REQUEST, message,
 295                           GURL::EmptyGURL());
 296 }
 297
 298 void AesDecryptor::LoadSession(SessionType session_type,
 299                                const std::string& session_id,
 300                                scoped_ptr<NewSessionCdmPromise> promise) {
 301   // TODO(xhwang): Change this to NOTREACHED() when blink checks for key systems
 302   // that do not support loadSession. See http://crbug.com/342481
 303   promise->reject(NOT_SUPPORTED_ERROR, 0, "LoadSession() is not supported.");
 304 }
 305
 306 void AesDecryptor::UpdateSession(const std::string& session_id,
 307                                  const uint8* response,
 308                                  int response_length,
 309                                  scoped_ptr<SimpleCdmPromise> promise) {
 310   CHECK(response);
 311   CHECK_GT(response_length, 0);
 312
 313   // TODO(jrummell): Convert back to a DCHECK once prefixed EME is removed.
 314   if (valid_sessions_.find(session_id) == valid_sessions_.end()) {
 315     promise->reject(INVALID_ACCESS_ERROR, 0, "Session does not exist.");
 316     return;
 317   }
 318
 319   std::string key_string(reinterpret_cast<const char*>(response),
 320                          response_length);
 321
 322   KeyIdAndKeyPairs keys;
 323   SessionType session_type = MediaKeys::TEMPORARY_SESSION;
 324   if (!ExtractKeysFromJWKSet(key_string, &keys, &session_type)) {
 325     promise->reject(
 326         INVALID_ACCESS_ERROR, 0, "Response is not a valid JSON Web Key Set.");
 327     return;
 328   }
 329
 330   // Make sure that at least one key was extracted.
 331   if (keys.empty()) {
 332     promise->reject(
 333         INVALID_ACCESS_ERROR, 0, "Response does not contain any keys.");
 334     return;
 335   }
 336
 337   for (KeyIdAndKeyPairs::iterator it = keys.begin(); it != keys.end(); ++it) {
 338     if (it->second.length() !=
 339         static_cast<size_t>(DecryptConfig::kDecryptionKeySize)) {
 340       DVLOG(1) << "Invalid key length: " << it->second.length();
 341       promise->reject(INVALID_ACCESS_ERROR, 0, "Invalid key length.");
 342       return;
 343     }
 344     if (!AddDecryptionKey(session_id, it->first, it->second)) {
 345       promise->reject(INVALID_ACCESS_ERROR, 0, "Unable to add key.");
 346       return;
 347     }
 348   }
 349
 350   {
 351     base::AutoLock auto_lock(new_key_cb_lock_);
 352
 353     if (!new_audio_key_cb_.is_null())
 354       new_audio_key_cb_.Run();
 355
 356     if (!new_video_key_cb_.is_null())
 357       new_video_key_cb_.Run();
 358   }
 359
 360   promise->resolve();
 361
 362   // Create the list of all available keys for this session.
 363   CdmKeysInfo keys_info;
 364   {
 365     base::AutoLock auto_lock(key_map_lock_);
 366     for (const auto& item : key_map_) {
 367       if (item.second->Contains(session_id)) {
 368         scoped_ptr<CdmKeyInformation> key_info(new CdmKeyInformation);
 369         key_info->key_id.assign(item.first.begin(), item.first.end());
 370         key_info->status = CdmKeyInformation::USABLE;
 371         key_info->system_code = 0;
 372         keys_info.push_back(key_info.release());
 373       }
 374     }
 375   }
 376
 377   // Assume that at least 1 new key has been successfully added and thus
 378   // sending true for |has_additional_usable_key|. http://crbug.com/448219.
 379   session_keys_change_cb_.Run(session_id, true, keys_info.Pass());
 380 }
 381
 382 void AesDecryptor::CloseSession(const std::string& session_id,
 383                                 scoped_ptr<SimpleCdmPromise> promise) {
 384   // Validate that this is a reference to an active session and then forget it.
 385   std::set<std::string>::iterator it = valid_sessions_.find(session_id);
 386   DCHECK(it != valid_sessions_.end());
 387
 388   valid_sessions_.erase(it);
 389
 390   // Close the session.
 391   DeleteKeysForSession(session_id);
 392   promise->resolve();
 393   session_closed_cb_.Run(session_id);
 394 }
 395
 396 void AesDecryptor::RemoveSession(const std::string& session_id,
 397                                  scoped_ptr<SimpleCdmPromise> promise) {
 398   // AesDecryptor doesn't keep any persistent data, so this should be
 399   // NOT_REACHED().
 400   // TODO(jrummell): Make sure persistent session types are rejected.
 401   // http://crbug.com/384152.
 402   //
 403   // However, v0.1b calls to CancelKeyRequest() will call this, so close the
 404   // session, if it exists.
 405   // TODO(jrummell): Remove the close() call when prefixed EME is removed.
 406   // http://crbug.com/249976.
 407   if (valid_sessions_.find(session_id) != valid_sessions_.end()) {
 408     CloseSession(session_id, promise.Pass());
 409     return;
 410   }
 411
 412   promise->reject(INVALID_ACCESS_ERROR, 0, "Session does not exist.");
 413 }
 414
 415 CdmContext* AesDecryptor::GetCdmContext() {
 416   return this;
 417 }
 418
 419 Decryptor* AesDecryptor::GetDecryptor() {
 420   return this;
 421 }
 422
 423 #if defined(ENABLE_BROWSER_CDMS)
 424 int AesDecryptor::GetCdmId() const {
 425   return kInvalidCdmId;
 426 }
 427 #endif  // defined(ENABLE_BROWSER_CDMS)
 428
 429 void AesDecryptor::RegisterNewKeyCB(StreamType stream_type,
 430                                     const NewKeyCB& new_key_cb) {
 431   base::AutoLock auto_lock(new_key_cb_lock_);
 432
 433   switch (stream_type) {
 434     case kAudio:
 435       new_audio_key_cb_ = new_key_cb;
 436       break;
 437     case kVideo:
 438       new_video_key_cb_ = new_key_cb;
 439       break;
 440     default:
 441       NOTREACHED();
 442   }
 443 }
 444
 445 void AesDecryptor::Decrypt(StreamType stream_type,
 446                            const scoped_refptr<DecoderBuffer>& encrypted,
 447                            const DecryptCB& decrypt_cb) {
 448   CHECK(encrypted->decrypt_config());
 449
 450   scoped_refptr<DecoderBuffer> decrypted;
 451   // An empty iv string signals that the frame is unencrypted.
 452   if (encrypted->decrypt_config()->iv().empty()) {
 453     decrypted = DecoderBuffer::CopyFrom(encrypted->data(),
 454                                         encrypted->data_size());
 455   } else {
 456     const std::string& key_id = encrypted->decrypt_config()->key_id();
 457     DecryptionKey* key = GetKey(key_id);
 458     if (!key) {
 459       DVLOG(1) << "Could not find a matching key for the given key ID.";
 460       decrypt_cb.Run(kNoKey, NULL);
 461       return;
 462     }
 463
 464     crypto::SymmetricKey* decryption_key = key->decryption_key();
 465     decrypted = DecryptData(*encrypted.get(), decryption_key);
 466     if (!decrypted.get()) {
 467       DVLOG(1) << "Decryption failed.";
 468       decrypt_cb.Run(kError, NULL);
 469       return;
 470     }
 471   }
 472
 473   decrypted->set_timestamp(encrypted->timestamp());
 474   decrypted->set_duration(encrypted->duration());
 475   decrypt_cb.Run(kSuccess, decrypted);
 476 }
 477
 478 void AesDecryptor::CancelDecrypt(StreamType stream_type) {
 479   // Decrypt() calls the DecryptCB synchronously so there's nothing to cancel.
 480 }
 481
 482 void AesDecryptor::InitializeAudioDecoder(const AudioDecoderConfig& config,
 483                                           const DecoderInitCB& init_cb) {
 484   // AesDecryptor does not support audio decoding.
 485   init_cb.Run(false);
 486 }
 487
 488 void AesDecryptor::InitializeVideoDecoder(const VideoDecoderConfig& config,
 489                                           const DecoderInitCB& init_cb) {
 490   // AesDecryptor does not support video decoding.
 491   init_cb.Run(false);
 492 }
 493
 494 void AesDecryptor::DecryptAndDecodeAudio(
 495     const scoped_refptr<DecoderBuffer>& encrypted,
 496     const AudioDecodeCB& audio_decode_cb) {
 497   NOTREACHED() << "AesDecryptor does not support audio decoding";
 498 }
 499
 500 void AesDecryptor::DecryptAndDecodeVideo(
 501     const scoped_refptr<DecoderBuffer>& encrypted,
 502     const VideoDecodeCB& video_decode_cb) {
 503   NOTREACHED() << "AesDecryptor does not support video decoding";
 504 }
 505
 506 void AesDecryptor::ResetDecoder(StreamType stream_type) {
 507   NOTREACHED() << "AesDecryptor does not support audio/video decoding";
 508 }
 509
 510 void AesDecryptor::DeinitializeDecoder(StreamType stream_type) {
 511   NOTREACHED() << "AesDecryptor does not support audio/video decoding";
 512 }
 513
 514 bool AesDecryptor::AddDecryptionKey(const std::string& session_id,
 515                                     const std::string& key_id,
 516                                     const std::string& key_string) {
 517   scoped_ptr<DecryptionKey> decryption_key(new DecryptionKey(key_string));
 518   if (!decryption_key->Init()) {
 519     DVLOG(1) << "Could not initialize decryption key.";
 520     return false;
 521   }
 522
 523   base::AutoLock auto_lock(key_map_lock_);
 524   KeyIdToSessionKeysMap::iterator key_id_entry = key_map_.find(key_id);
 525   if (key_id_entry != key_map_.end()) {
 526     key_id_entry->second->Insert(session_id, decryption_key.Pass());
 527     return true;
 528   }
 529
 530   // |key_id| not found, so need to create new entry.
 531   scoped_ptr<SessionIdDecryptionKeyMap> inner_map(
 532       new SessionIdDecryptionKeyMap());
 533   inner_map->Insert(session_id, decryption_key.Pass());
 534   key_map_.add(key_id, inner_map.Pass());
 535   return true;
 536 }
 537
 538 AesDecryptor::DecryptionKey* AesDecryptor::GetKey(
 539     const std::string& key_id) const {
 540   base::AutoLock auto_lock(key_map_lock_);
 541   KeyIdToSessionKeysMap::const_iterator key_id_found = key_map_.find(key_id);
 542   if (key_id_found == key_map_.end())
 543     return NULL;
 544
 545   // Return the key from the "latest" session_id entry.
 546   return key_id_found->second->LatestDecryptionKey();
 547 }
 548
 549 void AesDecryptor::DeleteKeysForSession(const std::string& session_id) {
 550   base::AutoLock auto_lock(key_map_lock_);
 551
 552   // Remove all keys associated with |session_id|. Since the data is
 553   // optimized for access in GetKey(), we need to look at each entry in
 554   // |key_map_|.
 555   KeyIdToSessionKeysMap::iterator it = key_map_.begin();
 556   while (it != key_map_.end()) {
 557     it->second->Erase(session_id);
 558     if (it->second->Empty()) {
 559       // Need to get rid of the entry for this key_id. This will mess up the
 560       // iterator, so we need to increment it first.
 561       KeyIdToSessionKeysMap::iterator current = it;
 562       ++it;
 563       key_map_.erase(current);
 564     } else {
 565       ++it;
 566     }
 567   }
 568 }
 569
 570 AesDecryptor::DecryptionKey::DecryptionKey(const std::string& secret)
 571     : secret_(secret) {
 572 }
 573
 574 AesDecryptor::DecryptionKey::~DecryptionKey() {}
 575
 576 bool AesDecryptor::DecryptionKey::Init() {
 577   CHECK(!secret_.empty());
 578   decryption_key_.reset(crypto::SymmetricKey::Import(
 579       crypto::SymmetricKey::AES, secret_));
 580   if (!decryption_key_)
 581     return false;
 582   return true;
 583 }
 584
 585 }  // namespace media