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