Add support for encrypted WebM files as defined in the RFC.

media/base/decrypt_config.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_BASE_DECRYPT_CONFIG_H_
 #define MEDIA_BASE_DECRYPT_CONFIG_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
-// Contains all information that a decryptor needs to decrypt.
+// Contains all information that a decryptor needs to decrypt a frame.
 class MEDIA_EXPORT DecryptConfig {
  public:
-  explicit DecryptConfig(const uint8* key_id, int key_id_size);
+  // Keys are always 128 bits.
+  static const int kDecryptionKeySize = 16;
+
+  // |key_id| is the ID that references the decryption key for this frame. |iv|
+  // is the initialization vector defined by the encrypted format. Currently
+  // |iv_size| must be 16 bytes as defined by WebM and ISO. |checksum| is the
+  // hash value of the encrypted buffer. |checksum| is defined by the
+  // encrypted format and may be NULL. |encrypted_frame_offset| is the offset
+  // into the encrypted buffer that the encrypted frame starts. The class
+  // will copy the data from |key_id|, |iv|, and |checksum|.
+  DecryptConfig(const uint8* key_id, int key_id_size,
+                const uint8* iv, int iv_size,
+                const uint8* checksum, int checksum_size,
+                int encrypted_frame_offset);
   ~DecryptConfig();
 
   const uint8* key_id() const { return key_id_.get(); }
   int key_id_size() const { return key_id_size_; }
+  const uint8* iv() const { return iv_.get(); }
+  int iv_size() const { return iv_size_; }
+  const uint8* checksum() const { return checksum_.get(); }
+  int checksum_size() const { return checksum_size_; }
+  int encrypted_frame_offset() const { return encrypted_frame_offset_; }
 
  private:
-  scoped_array<uint8> key_id_;
-  int key_id_size_;
+  const scoped_array<uint8> key_id_;
+  const int key_id_size_;
+
+  // Initialization vector.
+  const scoped_array<uint8> iv_;
+  const int iv_size_;
+
+  // Checksum of the data to be verified before decrypting the data. This may
+  // be NULL for some formats.
+  const scoped_array<uint8> checksum_;
+  const int checksum_size_;
+
+  // This is the offset in bytes to where the encrypted data starts within
+  // the input buffer.
+  const int encrypted_frame_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(DecryptConfig);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_DECRYPT_CONFIG_H_