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/cdm_context.h"
  17 #include "media/base/decryptor.h"
  18 #include "media/base/media_export.h"
  19 #include "media/base/media_keys.h"
  20
  21 namespace crypto {
  22 class SymmetricKey;
  23 }
  24
  25 namespace media {
  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 MediaKeys,
  30                                   public CdmContext,
  31                                   public Decryptor {
  32  public:
  33   AesDecryptor(const SessionMessageCB& session_message_cb,
  34                const SessionClosedCB& session_closed_cb,
  35                const SessionKeysChangeCB& session_keys_change_cb);
  36   ~AesDecryptor() override;
  37
  38   // MediaKeys implementation.
  39   void SetServerCertificate(const uint8* certificate_data,
  40                             int certificate_data_length,
  41                             scoped_ptr<SimpleCdmPromise> promise) override;
  42   void CreateSessionAndGenerateRequest(
  43       SessionType session_type,
  44       EmeInitDataType init_data_type,
  45       const uint8* init_data,
  46       int init_data_length,
  47       scoped_ptr<NewSessionCdmPromise> promise) override;
  48   void LoadSession(SessionType session_type,
  49                    const std::string& session_id,
  50                    scoped_ptr<NewSessionCdmPromise> promise) override;
  51   void UpdateSession(const std::string& session_id,
  52                      const uint8* response,
  53                      int response_length,
  54                      scoped_ptr<SimpleCdmPromise> promise) override;
  55   void CloseSession(const std::string& session_id,
  56                     scoped_ptr<SimpleCdmPromise> promise) override;
  57   void RemoveSession(const std::string& session_id,
  58                      scoped_ptr<SimpleCdmPromise> promise) override;
  59   CdmContext* GetCdmContext() override;
  60
  61   // CdmContext implementation.
  62   Decryptor* GetDecryptor() override;
  63   int GetCdmId() const override;
  64
  65   // Decryptor implementation.
  66   void RegisterNewKeyCB(StreamType stream_type,
  67                         const NewKeyCB& key_added_cb) override;
  68   void Decrypt(StreamType stream_type,
  69                const scoped_refptr<DecoderBuffer>& encrypted,
  70                const DecryptCB& decrypt_cb) override;
  71   void CancelDecrypt(StreamType stream_type) override;
  72   void InitializeAudioDecoder(const AudioDecoderConfig& config,
  73                               const DecoderInitCB& init_cb) override;
  74   void InitializeVideoDecoder(const VideoDecoderConfig& config,
  75                               const DecoderInitCB& init_cb) override;
  76   void DecryptAndDecodeAudio(const scoped_refptr<DecoderBuffer>& encrypted,
  77                              const AudioDecodeCB& audio_decode_cb) override;
  78   void DecryptAndDecodeVideo(const scoped_refptr<DecoderBuffer>& encrypted,
  79                              const VideoDecodeCB& video_decode_cb) override;
  80   void ResetDecoder(StreamType stream_type) override;
  81   void DeinitializeDecoder(StreamType stream_type) override;
  82
  83  private:
  84   // TODO(fgalligan): Remove this and change KeyMap to use crypto::SymmetricKey
  85   // as there are no decryptors that are performing an integrity check.
  86   // Helper class that manages the decryption key.
  87   class DecryptionKey {
  88    public:
  89     explicit DecryptionKey(const std::string& secret);
  90     ~DecryptionKey();
  91
  92     // Creates the encryption key.
  93     bool Init();
  94
  95     crypto::SymmetricKey* decryption_key() { return decryption_key_.get(); }
  96
  97    private:
  98     // The base secret that is used to create the decryption key.
  99     const std::string secret_;
 100
 101     // The key used to decrypt the data.
 102     scoped_ptr<crypto::SymmetricKey> decryption_key_;
 103
 104     DISALLOW_COPY_AND_ASSIGN(DecryptionKey);
 105   };
 106
 107   // Keep track of the keys for a key ID. If multiple sessions specify keys
 108   // for the same key ID, then the last key inserted is used. The structure is
 109   // optimized so that Decrypt() has fast access, at the cost of slow deletion
 110   // of keys when a session is released.
 111   class SessionIdDecryptionKeyMap;
 112
 113   // Key ID <-> SessionIdDecryptionKeyMap map.
 114   typedef base::ScopedPtrHashMap<std::string, SessionIdDecryptionKeyMap>
 115       KeyIdToSessionKeysMap;
 116
 117   // Creates a DecryptionKey using |key_string| and associates it with |key_id|.
 118   // Returns true if successful.
 119   bool AddDecryptionKey(const std::string& session_id,
 120                         const std::string& key_id,
 121                         const std::string& key_string);
 122
 123   // Gets a DecryptionKey associated with |key_id|. The AesDecryptor still owns
 124   // the key. Returns NULL if no key is associated with |key_id|.
 125   DecryptionKey* GetKey(const std::string& key_id) const;
 126
 127   // Determines if |key_id| is already specified for |session_id|.
 128   bool HasKey(const std::string& session_id, const std::string& key_id);
 129
 130   // Deletes all keys associated with |session_id|.
 131   void DeleteKeysForSession(const std::string& session_id);
 132
 133   // Callbacks for firing session events.
 134   SessionMessageCB session_message_cb_;
 135   SessionClosedCB session_closed_cb_;
 136   SessionKeysChangeCB session_keys_change_cb_;
 137
 138   // Since only Decrypt() is called off the renderer thread, we only need to
 139   // protect |key_map_|, the only member variable that is shared between
 140   // Decrypt() and other methods.
 141   KeyIdToSessionKeysMap key_map_;  // Protected by |key_map_lock_|.
 142   mutable base::Lock key_map_lock_;  // Protects the |key_map_|.
 143
 144   // Keeps track of current valid sessions.
 145   std::set<std::string> valid_sessions_;
 146
 147   // Make session ID unique per renderer by making it static. Session
 148   // IDs seen by the app will be "1", "2", etc.
 149   static uint32 next_session_id_;
 150
 151   NewKeyCB new_audio_key_cb_;
 152   NewKeyCB new_video_key_cb_;
 153
 154   // Protect |new_audio_key_cb_| and |new_video_key_cb_| as they are set on the
 155   // main thread but called on the media thread.
 156   mutable base::Lock new_key_cb_lock_;
 157
 158   DISALLOW_COPY_AND_ASSIGN(AesDecryptor);
 159 };
 160
 161 }  // namespace media
 162
 163 #endif  // MEDIA_CRYPTO_AES_DECRYPTOR_H_