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