84 lines
3.2 KiB
C++
84 lines
3.2 KiB
C++
// Copyright 2016 Google Inc. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file or at
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// https://developers.google.com/open-source/licenses/bsd
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#include "packager/media/base/aes_cryptor.h"
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#include "packager/base/macros.h"
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#include "packager/base/memory/scoped_ptr.h"
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namespace shaka {
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namespace media {
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/// Implements pattern-based encryption/decryption.
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class AesPatternCryptor : public AesCryptor {
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public:
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/// Enumerator for controling encrytion/decryption mode for the last
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/// encryption/decrytion block(s).
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enum PatternEncryptionMode {
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/// Use kEncryptIfCryptByteBlockRemaining if the last blocks is exactly the
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/// same as the number of remaining bytes. IOW
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/// if (remaining_bytes == encryption_block_bytes)
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/// encrypt(remaining_data)
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kEncryptIfCryptByteBlockRemaining,
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/// Use kSkipIfCryptByteBlockRemaining to not encrypt/decrypt the last
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/// clocks if it is exactly the same as the number of remaining bytes.
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/// if (remaining_bytes > encryption_block_bytes) {
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/// // Since this is the last blocks, this is effectively the same
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/// // condition as remaining_bytes != encryption_block_bytes.
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/// encrypt().
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/// }
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/// Use this mode for HLS SAMPLE-AES.
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kSkipIfCryptByteBlockRemaining,
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};
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/// @param crypt_byte_block indicates number of encrypted blocks (16-byte) in
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/// pattern based encryption.
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/// @param skip_byte_block indicates number of unencrypted blocks (16-byte)
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/// in pattern based encryption.
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/// @param encryption_mode is used to determine the behavior for the last
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/// block.
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/// @param constant_iv_flag indicates whether a constant iv is used,
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/// kUseConstantIv means that the same iv is used for all Crypt calls
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/// until iv is changed via SetIv; otherwise, iv can be incremented
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/// (for counter mode) or chained (for cipher block chaining mode)
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/// internally inside Crypt call, i.e. iv will be updated across Crypt
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/// calls.
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/// @param cryptor points to an AesCryptor instance which performs the actual
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/// encryption/decryption. Note that @a cryptor shall not use constant
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/// iv.
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AesPatternCryptor(uint8_t crypt_byte_block,
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uint8_t skip_byte_block,
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PatternEncryptionMode encryption_mode,
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ConstantIvFlag constant_iv_flag,
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scoped_ptr<AesCryptor> cryptor);
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~AesPatternCryptor() override;
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/// @name AesCryptor implementation overrides.
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/// @{
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bool InitializeWithIv(const std::vector<uint8_t>& key,
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const std::vector<uint8_t>& iv) override;
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/// @}
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private:
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bool CryptInternal(const uint8_t* text,
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size_t text_size,
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uint8_t* crypt_text,
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size_t* crypt_text_size) override;
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void SetIvInternal() override;
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bool NeedEncrypt(size_t input_size, size_t target_data_size);
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const uint8_t crypt_byte_block_;
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const uint8_t skip_byte_block_;
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const PatternEncryptionMode encryption_mode_;
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scoped_ptr<AesCryptor> cryptor_;
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DISALLOW_COPY_AND_ASSIGN(AesPatternCryptor);
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};
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} // namespace media
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} // namespace shaka
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