aes_cbc_crypto.cc | Explore in Territory

// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/cdm/aes_cbc_crypto.h"

#include "base/logging.h"
#include "base/numerics/safe_conversions.h"
#include "crypto/openssl_util.h"
#include "crypto/symmetric_key.h"
#include "third_party/boringssl/src/include/openssl/aes.h"
#include "third_party/boringssl/src/include/openssl/err.h"
#include "third_party/boringssl/src/include/openssl/evp.h"

// Notes on using OpenSSL:
// https://www.openssl.org/docs/man1.1.0/crypto/EVP_DecryptUpdate.html
// The documentation for EVP_DecryptUpdate() only states
//   "EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex()
//   are the corresponding decryption operations. EVP_DecryptFinal() will
//   return an error code if padding is enabled and the final block is not
//   correctly formatted. The parameters and restrictions are identical
//   to the encryption operations except that if padding is enabled ..."
// As this implementation does not use padding, the last part should not be
// an issue. However, there is no mention whether data can be decrypted
// block-by-block or if all the data must be unencrypted at once.
//
// The documentation for EVP_EncryptUpdate() (same page as above) states
//   "EVP_EncryptUpdate() encrypts inl bytes from the buffer in and writes
//   the encrypted version to out. This function can be called multiple times
//   to encrypt successive blocks of data."
// Given that the EVP_Decrypt* methods have the same restrictions, the code
// below assumes that EVP_DecryptUpdate() can be called on a block-by-block
// basis. A test in aes_cbc_crypto_unittest.cc verifies this.

namespace media {

AesCbcCrypto::AesCbcCrypto() = default;
AesCbcCrypto::~AesCbcCrypto() = default;

bool AesCbcCrypto::Initialize(const crypto::SymmetricKey& key,
                              base::span<const uint8_t> iv) { … }

bool AesCbcCrypto::Decrypt(base::span<const uint8_t> encrypted_data,
                           uint8_t* decrypted_data) { … }

}  // namespace media
chromium/media/cdm/aes_cbc_crypto.cc
