80 lines
3.0 KiB
C++
80 lines
3.0 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef MEDIA_BASE_DECRYPT_CONFIG_H_
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#define MEDIA_BASE_DECRYPT_CONFIG_H_
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#include <string>
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#include <vector>
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#include "base/basictypes.h"
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#include "base/memory/scoped_ptr.h"
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namespace media {
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// The Common Encryption spec provides for subsample encryption, where portions
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// of a sample are set in cleartext. A SubsampleEntry specifies the number of
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// clear and encrypted bytes in each subsample. For decryption, all of the
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// encrypted bytes in a sample should be considered a single logical stream,
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// regardless of how they are divided into subsamples, and the clear bytes
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// should not be considered as part of decryption. This is logically equivalent
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// to concatenating all 'cypher_bytes' portions of subsamples, decrypting that
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// result, and then copying each byte from the decrypted block over the
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// position of the corresponding encrypted byte.
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struct SubsampleEntry {
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uint32 clear_bytes;
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uint32 cypher_bytes;
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};
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// Contains all information that a decryptor needs to decrypt a media sample.
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class DecryptConfig {
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public:
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// Keys are always 128 bits.
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static const int kDecryptionKeySize = 16;
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// |key_id| is the ID that references the decryption key for this sample.
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// |iv| is the initialization vector defined by the encrypted format.
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// Currently |iv| must be 16 bytes as defined by WebM and ISO. Or must be
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// empty which signals an unencrypted frame.
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// |data_offset| is the amount of data that should be discarded from the
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// head of the sample buffer before applying subsample information. A
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// decrypted buffer will be shorter than an encrypted buffer by this amount.
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// |subsamples| defines the clear and encrypted portions of the sample as
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// described above. A decrypted buffer will be equal in size to the sum
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// of the subsample sizes.
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//
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// |data_offset| is applied before |subsamples|.
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DecryptConfig(const std::string& key_id,
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const std::string& iv,
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const int data_offset,
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const std::vector<SubsampleEntry>& subsamples);
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~DecryptConfig();
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const std::string& key_id() const { return key_id_; }
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const std::string& iv() const { return iv_; }
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int data_offset() const { return data_offset_; }
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const std::vector<SubsampleEntry>& subsamples() const { return subsamples_; }
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private:
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const std::string key_id_;
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// Initialization vector.
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const std::string iv_;
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// TODO(fgalligan): Remove |data_offset_| if there is no plan to use it in
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// the future.
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// Amount of data to be discarded before applying subsample information.
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const int data_offset_;
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// Subsample information. May be empty for some formats, meaning entire frame
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// (less data ignored by data_offset_) is encrypted.
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const std::vector<SubsampleEntry> subsamples_;
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DISALLOW_COPY_AND_ASSIGN(DecryptConfig);
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};
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} // namespace media
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#endif // MEDIA_BASE_DECRYPT_CONFIG_H_
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