Remove the checksum/HMAC code from the decryptor.

media/crypto/aes_decryptor.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_CRYPTO_AES_DECRYPTOR_H_
 #define MEDIA_CRYPTO_AES_DECRYPTOR_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/string_piece.h"
 #include "base/synchronization/lock.h"
 #include "media/base/decryptor.h"
 #include "media/base/media_export.h"
 
 namespace crypto {
 class SymmetricKey;
 }
 
 namespace media {
 
 class DecryptorClient;
 
 // Decrypts an AES encrypted buffer into an unencrypted buffer. The AES
-// encryption must be CTR with a key size of 128bits. Optionally checks the
-// integrity of the encrypted data.
+// encryption must be CTR with a key size of 128bits.
 class MEDIA_EXPORT AesDecryptor : public Decryptor {
  public:
   // The AesDecryptor does not take ownership of the |client|. The |client|
   // must be valid throughout the lifetime of the AesDecryptor.
   explicit AesDecryptor(DecryptorClient* client);
   virtual ~AesDecryptor();
 
   // Decryptor implementation.
   virtual bool GenerateKeyRequest(const std::string& key_system,
                                   const uint8* init_data,
                                   int init_data_length) OVERRIDE;
   virtual void AddKey(const std::string& key_system,
                       const uint8* key,
                       int key_length,
                       const uint8* init_data,
                       int init_data_length,
                       const std::string& session_id) OVERRIDE;
   virtual void CancelKeyRequest(const std::string& key_system,
                                 const std::string& session_id) OVERRIDE;
-  // Decrypts |encrypted| buffer. |encrypted| should not be NULL. |encrypted|
-  // will signal if an integrity check must be performed before decryption.
-  // Returns a DecoderBuffer with the decrypted data if the decryption
-  // succeeded through |decrypt_cb|.
+  // Decrypts |encrypted| buffer. |encrypted| should not be NULL. Returns a
+  // DecoderBuffer with the decrypted data if the decryption succeeded through
+  // |decrypt_cb|.
   virtual void Decrypt(const scoped_refptr<DecoderBuffer>& encrypted,
                        const DecryptCB& decrypt_cb) OVERRIDE;
   virtual void Stop() OVERRIDE;
 
  private:
-  // Helper class that manages the decryption key and HMAC key. The HMAC key
-  // may be NULL.
+  // TODO(fgalligan): Remove this and change KeyMap to use crypto::SymmetricKey
+  // as there are no decryptors that are performing an integrity check.
+  // Helper class that manages the decryption key.
   class DecryptionKey {
    public:
     explicit DecryptionKey(const std::string& secret);
     ~DecryptionKey();
 
-    // Creates the encryption key, and derives the WebM decryption key and HMAC.
+    // Creates the encryption key.
     bool Init();
 
     crypto::SymmetricKey* decryption_key() { return decryption_key_.get(); }
-    crypto::SymmetricKey* webm_decryption_key()
-      { return webm_decryption_key_.get(); }
-    base::StringPiece hmac_key() { return base::StringPiece(hmac_key_); }
 
    private:
-    // The base secret that is used to derive the decryption key and optionally
-    // the HMAC key.
+    // The base secret that is used to create the decryption key.
     const std::string secret_;
 
     // The key used to decrypt the data.
     scoped_ptr<crypto::SymmetricKey> decryption_key_;
 
-    // The key used for decryption of WebM media, derived from the secret.
-    scoped_ptr<crypto::SymmetricKey> webm_decryption_key_;
-
-    // The key used to perform the integrity check.  Currently the HMAC key is
-    // defined by the WebM encrypted specification. Current encrypted WebM
-    // request for comments specification is here
-    // http://wiki.webmproject.org/encryption/webm-encryption-rfc
-    std::string hmac_key_;
-
     DISALLOW_COPY_AND_ASSIGN(DecryptionKey);
   };
 
   // Sets |key| for |key_id|. The AesDecryptor takes the ownership of the |key|.
   void SetKey(const std::string& key_id, scoped_ptr<DecryptionKey> key);
 
   // Gets a DecryptionKey associated with |key_id|. The AesDecryptor still owns
   // the key. Returns NULL if no key is associated with |key_id|.
   DecryptionKey* GetKey(const std::string& key_id) const;
 
@@ skipping 13 matching lines @@
   static uint32 next_session_id_;
 
   DecryptorClient* const client_;
 
   DISALLOW_COPY_AND_ASSIGN(AesDecryptor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_CRYPTO_AES_DECRYPTOR_H_