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 <set>
   9 #include <string>
  10
  11 #include "base/basictypes.h"
  12 #include "base/containers/scoped_ptr_hash_map.h"
  13 #include "base/memory/ref_counted.h"
  14 #include "base/memory/scoped_ptr.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 SessionCreatedCB& session_created_cb,
  31                const SessionMessageCB& session_message_cb,
  32                const SessionReadyCB& session_ready_cb,
  33                const SessionClosedCB& session_closed_cb,
  34                const SessionErrorCB& session_error_cb);
  35   virtual ~AesDecryptor();
  36
  37   // MediaKeys implementation.
  38   virtual bool CreateSession(uint32 session_id,
  39                              const std::string& type,
  40                              const uint8* init_data,
  41                              int init_data_length) OVERRIDE;
  42   virtual void UpdateSession(uint32 session_id,
  43                              const uint8* response,
  44                              int response_length) OVERRIDE;
  45   virtual void ReleaseSession(uint32 session_id) OVERRIDE;
  46   virtual Decryptor* GetDecryptor() OVERRIDE;
  47
  48   // Decryptor implementation.
  49   virtual void RegisterNewKeyCB(StreamType stream_type,
  50                                 const NewKeyCB& key_added_cb) OVERRIDE;
  51   virtual void Decrypt(StreamType stream_type,
  52                        const scoped_refptr<DecoderBuffer>& encrypted,
  53                        const DecryptCB& decrypt_cb) OVERRIDE;
  54   virtual void CancelDecrypt(StreamType stream_type) OVERRIDE;
  55   virtual void InitializeAudioDecoder(const AudioDecoderConfig& config,
  56                                       const DecoderInitCB& init_cb) OVERRIDE;
  57   virtual void InitializeVideoDecoder(const VideoDecoderConfig& config,
  58                                       const DecoderInitCB& init_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   // Keep track of the keys for a key ID. If multiple sessions specify keys
  93   // for the same key ID, then the last key inserted is used. The structure is
  94   // optimized so that Decrypt() has fast access, at the cost of slow deletion
  95   // of keys when a session is released.
  96   class SessionIdDecryptionKeyMap;
  97
  98   // Key ID <-> SessionIdDecryptionKeyMap map.
  99   typedef base::ScopedPtrHashMap<std::string, SessionIdDecryptionKeyMap>
 100       KeyIdToSessionKeysMap;
 101
 102   // Creates a DecryptionKey using |key_string| and associates it with |key_id|.
 103   // Returns true if successful.
 104   bool AddDecryptionKey(const uint32 session_id,
 105                         const std::string& key_id,
 106                         const std::string& key_string);
 107
 108   // Gets a DecryptionKey associated with |key_id|. The AesDecryptor still owns
 109   // the key. Returns NULL if no key is associated with |key_id|.
 110   DecryptionKey* GetKey(const std::string& key_id) const;
 111
 112   // Deletes all keys associated with |session_id|.
 113   void DeleteKeysForSession(const uint32 session_id);
 114
 115   // Callbacks for firing session events.
 116   SessionCreatedCB session_created_cb_;
 117   SessionMessageCB session_message_cb_;
 118   SessionReadyCB session_ready_cb_;
 119   SessionClosedCB session_closed_cb_;
 120   SessionErrorCB session_error_cb_;
 121
 122   // Since only Decrypt() is called off the renderer thread, we only need to
 123   // protect |key_map_|, the only member variable that is shared between
 124   // Decrypt() and other methods.
 125   KeyIdToSessionKeysMap key_map_;  // Protected by |key_map_lock_|.
 126   mutable base::Lock key_map_lock_;  // Protects the |key_map_|.
 127
 128   // Keeps track of current valid session IDs.
 129   std::set<uint32> valid_sessions_;
 130
 131   // Make web session ID unique per renderer by making it static. Web session
 132   // IDs seen by the app will be "1", "2", etc.
 133   static uint32 next_web_session_id_;
 134
 135   NewKeyCB new_audio_key_cb_;
 136   NewKeyCB new_video_key_cb_;
 137
 138   // Protect |new_audio_key_cb_| and |new_video_key_cb_| as they are set on the
 139   // main thread but called on the media thread.
 140   mutable base::Lock new_key_cb_lock_;
 141
 142   DISALLOW_COPY_AND_ASSIGN(AesDecryptor);
 143 };
 144
 145 }  // namespace media
 146
 147 #endif  // MEDIA_CRYPTO_AES_DECRYPTOR_H_