media/base/decrypt_config.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_BASE_DECRYPT_CONFIG_H_
   6 #define MEDIA_BASE_DECRYPT_CONFIG_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "media/base/media_export.h"
  14
  15 namespace media {
  16
  17 // The Common Encryption spec provides for subsample encryption, where portions
  18 // of a sample are set in cleartext. A SubsampleEntry specifies the number of
  19 // clear and encrypted bytes in each subsample. For decryption, all of the
  20 // encrypted bytes in a sample should be considered a single logical stream,
  21 // regardless of how they are divided into subsamples, and the clear bytes
  22 // should not be considered as part of decryption. This is logically equivalent
  23 // to concatenating all 'cypher_bytes' portions of subsamples, decrypting that
  24 // result, and then copying each byte from the decrypted block over the
  25 // position of the corresponding encrypted byte.
  26 struct SubsampleEntry {
  27   SubsampleEntry() : clear_bytes(0), cypher_bytes(0) {}
  28   SubsampleEntry(uint32 clear_bytes, uint32 cypher_bytes)
  29       : clear_bytes(clear_bytes), cypher_bytes(cypher_bytes) {}
  30   uint32 clear_bytes;
  31   uint32 cypher_bytes;
  32 };
  33
  34 // Contains all information that a decryptor needs to decrypt a media sample.
  35 class MEDIA_EXPORT DecryptConfig {
  36  public:
  37   // Keys are always 128 bits.
  38   static const int kDecryptionKeySize = 16;
  39
  40   // |key_id| is the ID that references the decryption key for this sample.
  41   // |iv| is the initialization vector defined by the encrypted format.
  42   //   Currently |iv| must be 16 bytes as defined by WebM and ISO. Or must be
  43   //   empty which signals an unencrypted frame.
  44   // |subsamples| defines the clear and encrypted portions of the sample as
  45   //   described above. A decrypted buffer will be equal in size to the sum
  46   //   of the subsample sizes.
  47   DecryptConfig(const std::string& key_id,
  48                 const std::string& iv,
  49                 const std::vector<SubsampleEntry>& subsamples);
  50   ~DecryptConfig();
  51
  52   const std::string& key_id() const { return key_id_; }
  53   const std::string& iv() const { return iv_; }
  54   const std::vector<SubsampleEntry>& subsamples() const { return subsamples_; }
  55
  56   // Returns true if all fields in |config| match this config.
  57   bool Matches(const DecryptConfig& config) const;
  58
  59  private:
  60   const std::string key_id_;
  61
  62   // Initialization vector.
  63   const std::string iv_;
  64
  65   // Subsample information. May be empty for some formats, meaning entire frame
  66   // (less data ignored by data_offset_) is encrypted.
  67   const std::vector<SubsampleEntry> subsamples_;
  68
  69   DISALLOW_COPY_AND_ASSIGN(DecryptConfig);
  70 };
  71
  72 }  // namespace media
  73
  74 #endif  // MEDIA_BASE_DECRYPT_CONFIG_H_