68 lines
2.8 KiB
C++
68 lines
2.8 KiB
C++
// Copyright 2019 Google LLC. All Rights Reserved. This file and proprietary
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// source code may only be used and distributed under the Widevine
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// License Agreement.
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#ifndef CDM_OEC_DECRYPT_FALLBACK_CHAIN_H_
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#define CDM_OEC_DECRYPT_FALLBACK_CHAIN_H_
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#include "OEMCryptoCENC.h"
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#include "disallow_copy_and_assign.h"
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#include "oemcrypto_fuzz_structs.h"
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namespace wvoec {
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// This class groups static methods relating to providing proper fallback
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// behavior when calling DecryptCENC in OEMCrypto v16. Outside code can leverage
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// this behavior by passing the samples to be decrypted to Decrypt(), which will
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// set off the chain of fallback functions as needed.
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//
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// The behavior of this class is pathological. For each block of data, it will
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// greedily try every possible way of passing data to OEMCrypto until one works.
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// In the order tried, the ways to send data are:
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// 1) Multiple Samples at once
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// 2) Individual Samples one at a time
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// 3) Individual Subsamples one at a time
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// 4) Individual Half-Subsamples one at a time
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// On a device that only accepts half-subsamples, the way OEMCrypto v15 did,
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// this results in many needless roundtrips to OEMCrypto. This would be
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// inefficient behavior for a real CDM, but for the sake of testing, we want to
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// use the maximal way the OEMCrypto implementation will accept the data. And,
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// for implementations that do not accept multiple samples or subsamples per
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// call, we want to test that they correctly reject larger calls.
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class DecryptFallbackChain {
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public:
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static OEMCryptoResult Decrypt(
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OEMCrypto_SESSION session_id, const OEMCrypto_SampleDescription* samples,
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size_t samples_length, OEMCryptoCipherMode cipher_mode,
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const OEMCrypto_CENCEncryptPatternDesc* pattern);
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private:
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static OEMCryptoResult DecryptSample(
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OEMCrypto_SESSION session_id, const OEMCrypto_SampleDescription& sample,
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OEMCryptoCipherMode cipher_mode,
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const OEMCrypto_CENCEncryptPatternDesc* pattern);
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static OEMCryptoResult DecryptSubsample(
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OEMCrypto_SESSION session_id, const OEMCrypto_SampleDescription& sample,
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const OEMCrypto_CENCEncryptPatternDesc* pattern,
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OEMCryptoCipherMode cipher_mode);
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static OEMCryptoResult DecryptSubsampleHalf(
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OEMCrypto_SESSION session_id, const OEMCrypto_SampleDescription& sample,
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const OEMCrypto_CENCEncryptPatternDesc* pattern,
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OEMCryptoCipherMode cipher_mode);
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// There is no reason to have an instance of this class.
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DecryptFallbackChain() = delete;
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CORE_DISALLOW_COPY_AND_ASSIGN(DecryptFallbackChain);
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};
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void WriteDecryptCencCorpus(OEMCryptoCipherMode cipher_mode,
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const OEMCrypto_SampleDescription* samples,
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const OEMCrypto_CENCEncryptPatternDesc* pattern,
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size_t samples_length);
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} // namespace wvoec
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#endif // CDM_OEC_DECRYPT_FALLBACK_CHAIN_H_
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