media/cdm/aes_decryptor.h

   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 #ifndef MEDIA_CRYPTO_AES_DECRYPTOR_H_
   6 #define MEDIA_CRYPTO_AES_DECRYPTOR_H_
   7
   8 #include <string>
   9
  10 #include "base/basictypes.h"
  11 #include "base/containers/hash_tables.h"
  12 #include "base/memory/ref_counted.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/strings/string_piece.h"
  15 #include "base/synchronization/lock.h"
  16 #include "media/base/decryptor.h"
  17 #include "media/base/media_export.h"
  18 #include "media/base/media_keys.h"
  19
  20 namespace crypto {
  21 class SymmetricKey;
  22 }
  23
  24 namespace media {
  25
  26 // Decrypts an AES encrypted buffer into an unencrypted buffer. The AES
  27 // encryption must be CTR with a key size of 128bits.
  28 class MEDIA_EXPORT AesDecryptor : public MediaKeys, public Decryptor {
  29  public:
  30   AesDecryptor(const KeyAddedCB& key_added_cb,
  31                const KeyErrorCB& key_error_cb,
  32                const KeyMessageCB& key_message_cb);
  33   virtual ~AesDecryptor();
  34
  35   // MediaKeys implementation.
  36   virtual bool GenerateKeyRequest(const std::string& type,
  37                                   const uint8* init_data,
  38                                   int init_data_length) OVERRIDE;
  39   virtual void AddKey(const uint8* key, int key_length,
  40                       const uint8* init_data, int init_data_length,
  41                       const std::string& session_id) OVERRIDE;
  42   virtual void CancelKeyRequest(const std::string& session_id) OVERRIDE;
  43   virtual Decryptor* GetDecryptor() OVERRIDE;
  44
  45   // Decryptor implementation.
  46   virtual void RegisterNewKeyCB(StreamType stream_type,
  47                                 const NewKeyCB& key_added_cb) OVERRIDE;
  48   virtual void Decrypt(StreamType stream_type,
  49                        const scoped_refptr<DecoderBuffer>& encrypted,
  50                        const DecryptCB& decrypt_cb) OVERRIDE;
  51   virtual void CancelDecrypt(StreamType stream_type) OVERRIDE;
  52   virtual void InitializeAudioDecoder(const AudioDecoderConfig& config,
  53                                       const DecoderInitCB& init_cb) OVERRIDE;
  54   virtual void InitializeVideoDecoder(const VideoDecoderConfig& config,
  55                                       const DecoderInitCB& init_cb) OVERRIDE;
  56   virtual void DecryptAndDecodeAudio(
  57       const scoped_refptr<DecoderBuffer>& encrypted,
  58       const AudioDecodeCB& audio_decode_cb) OVERRIDE;
  59   virtual void DecryptAndDecodeVideo(
  60       const scoped_refptr<DecoderBuffer>& encrypted,
  61       const VideoDecodeCB& video_decode_cb) OVERRIDE;
  62   virtual void ResetDecoder(StreamType stream_type) OVERRIDE;
  63   virtual void DeinitializeDecoder(StreamType stream_type) OVERRIDE;
  64
  65  private:
  66   // TODO(fgalligan): Remove this and change KeyMap to use crypto::SymmetricKey
  67   // as there are no decryptors that are performing an integrity check.
  68   // Helper class that manages the decryption key.
  69   class DecryptionKey {
  70    public:
  71     explicit DecryptionKey(const std::string& secret);
  72     ~DecryptionKey();
  73
  74     // Creates the encryption key.
  75     bool Init();
  76
  77     crypto::SymmetricKey* decryption_key() { return decryption_key_.get(); }
  78
  79    private:
  80     // The base secret that is used to create the decryption key.
  81     const std::string secret_;
  82
  83     // The key used to decrypt the data.
  84     scoped_ptr<crypto::SymmetricKey> decryption_key_;
  85
  86     DISALLOW_COPY_AND_ASSIGN(DecryptionKey);
  87   };
  88
  89   // Creates a DecryptionKey using |key_string| and associates it with |key_id|.
  90   // Returns true if successful.
  91   bool AddDecryptionKey(const std::string& key_id,
  92                         const std::string& key_string);
  93
  94   // Gets a DecryptionKey associated with |key_id|. The AesDecryptor still owns
  95   // the key. Returns NULL if no key is associated with |key_id|.
  96   DecryptionKey* GetKey(const std::string& key_id) const;
  97
  98   // Callbacks for firing key events.
  99   KeyAddedCB key_added_cb_;
 100   KeyErrorCB key_error_cb_;
 101   KeyMessageCB key_message_cb_;
 102
 103   // KeyMap owns the DecryptionKey* and must delete them when they are
 104   // not needed any more.
 105   typedef base::hash_map<std::string, DecryptionKey*> KeyMap;
 106
 107   // Since only Decrypt() is called off the renderer thread, we only need to
 108   // protect |key_map_|, the only member variable that is shared between
 109   // Decrypt() and other methods.
 110   KeyMap key_map_;  // Protected by the |key_map_lock_|.
 111   mutable base::Lock key_map_lock_;  // Protects the |key_map_|.
 112
 113   // Make session ID unique per renderer by making it static.
 114   // TODO(xhwang): Make session ID more strictly defined if needed:
 115   // https://www.w3.org/Bugs/Public/show_bug.cgi?id=16739#c0
 116   static uint32 next_session_id_;
 117
 118   NewKeyCB new_audio_key_cb_;
 119   NewKeyCB new_video_key_cb_;
 120
 121   DISALLOW_COPY_AND_ASSIGN(AesDecryptor);
 122 };
 123
 124 }  // namespace media
 125
 126 #endif  // MEDIA_CRYPTO_AES_DECRYPTOR_H_