media/crypto/aes_decryptor.h

   1 // Copyright (c) 2012 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/hash_tables.h"
  12 #include "base/memory/ref_counted.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/string_piece.h"
  15 #include "base/synchronization/lock.h"
  16 #include "media/base/decryptor.h"
  17 #include "media/base/media_export.h"
  18
  19 namespace crypto {
  20 class SymmetricKey;
  21 }
  22
  23 namespace media {
  24
  25 class DecryptorClient;
  26
  27 // Decrypts an AES encrypted buffer into an unencrypted buffer. The AES
  28 // encryption must be CTR with a key size of 128bits.
  29 class MEDIA_EXPORT AesDecryptor : public Decryptor {
  30  public:
  31   // The AesDecryptor does not take ownership of the |client|. The |client|
  32   // must be valid throughout the lifetime of the AesDecryptor.
  33   explicit AesDecryptor(DecryptorClient* client);
  34   virtual ~AesDecryptor();
  35
  36   // Decryptor implementation.
  37   virtual bool GenerateKeyRequest(const std::string& key_system,
  38                                   const std::string& type,
  39                                   const uint8* init_data,
  40                                   int init_data_length) OVERRIDE;
  41   virtual void AddKey(const std::string& key_system,
  42                       const uint8* key,
  43                       int key_length,
  44                       const uint8* init_data,
  45                       int init_data_length,
  46                       const std::string& session_id) OVERRIDE;
  47   virtual void CancelKeyRequest(const std::string& key_system,
  48                                 const std::string& session_id) OVERRIDE;
  49   virtual void Decrypt(StreamType stream_type,
  50                        const scoped_refptr<DecoderBuffer>& encrypted,
  51                        const DecryptCB& decrypt_cb) OVERRIDE;
  52   virtual void CancelDecrypt(StreamType stream_type) OVERRIDE;
  53   virtual void InitializeAudioDecoder(scoped_ptr<AudioDecoderConfig> config,
  54                                       const DecoderInitCB& init_cb,
  55                                       const KeyAddedCB& key_added_cb) OVERRIDE;
  56   virtual void InitializeVideoDecoder(scoped_ptr<VideoDecoderConfig> config,
  57                                       const DecoderInitCB& init_cb,
  58                                       const KeyAddedCB& key_added_cb) OVERRIDE;
  59   virtual void DecryptAndDecodeAudio(
  60       const scoped_refptr<DecoderBuffer>& encrypted,
  61       const AudioDecodeCB& audio_decode_cb) OVERRIDE;
  62   virtual void DecryptAndDecodeVideo(
  63       const scoped_refptr<DecoderBuffer>& encrypted,
  64       const VideoDecodeCB& video_decode_cb) OVERRIDE;
  65   virtual void ResetDecoder(StreamType stream_type) OVERRIDE;
  66   virtual void DeinitializeDecoder(StreamType stream_type) OVERRIDE;
  67
  68  private:
  69   // TODO(fgalligan): Remove this and change KeyMap to use crypto::SymmetricKey
  70   // as there are no decryptors that are performing an integrity check.
  71   // Helper class that manages the decryption key.
  72   class DecryptionKey {
  73    public:
  74     explicit DecryptionKey(const std::string& secret);
  75     ~DecryptionKey();
  76
  77     // Creates the encryption key.
  78     bool Init();
  79
  80     crypto::SymmetricKey* decryption_key() { return decryption_key_.get(); }
  81
  82    private:
  83     // The base secret that is used to create the decryption key.
  84     const std::string secret_;
  85
  86     // The key used to decrypt the data.
  87     scoped_ptr<crypto::SymmetricKey> decryption_key_;
  88
  89     DISALLOW_COPY_AND_ASSIGN(DecryptionKey);
  90   };
  91
  92   // Sets |key| for |key_id|. The AesDecryptor takes the ownership of the |key|.
  93   void SetKey(const std::string& key_id, scoped_ptr<DecryptionKey> key);
  94
  95   // Gets a DecryptionKey associated with |key_id|. The AesDecryptor still owns
  96   // the key. Returns NULL if no key is associated with |key_id|.
  97   DecryptionKey* GetKey(const std::string& key_id) const;
  98
  99   // KeyMap owns the DecryptionKey* and must delete them when they are
 100   // not needed any more.
 101   typedef base::hash_map<std::string, DecryptionKey*> KeyMap;
 102
 103   // Since only Decrypt() is called off the renderer thread, we only need to
 104   // protect |key_map_|, the only member variable that is shared between
 105   // Decrypt() and other methods.
 106   KeyMap key_map_;  // Protected by the |key_map_lock_|.
 107   mutable base::Lock key_map_lock_;  // Protects the |key_map_|.
 108
 109   // Make session ID unique per renderer by making it static.
 110   // TODO(xhwang): Make session ID more strictly defined if needed:
 111   // https://www.w3.org/Bugs/Public/show_bug.cgi?id=16739#c0
 112   static uint32 next_session_id_;
 113
 114   DecryptorClient* const client_;
 115
 116   DISALLOW_COPY_AND_ASSIGN(AesDecryptor);
 117 };
 118
 119 }  // namespace media
 120
 121 #endif  // MEDIA_CRYPTO_AES_DECRYPTOR_H_