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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40285824): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include <stddef.h>
#include <stdint.h>
#include <memory>
#include "base/check.h"
#include "base/numerics/safe_math.h"
#include "components/webcrypto/algorithms/aes.h"
#include "components/webcrypto/algorithms/util.h"
#include "components/webcrypto/blink_key_handle.h"
#include "components/webcrypto/status.h"
#include "crypto/openssl_util.h"
#include "third_party/blink/public/platform/web_crypto_algorithm_params.h"
#include "third_party/boringssl/src/include/openssl/aes.h"
#include "third_party/boringssl/src/include/openssl/cipher.h"
namespace webcrypto {
namespace {
const EVP_CIPHER* GetAESCipherByKeyLength(size_t key_length_bytes) {
// 192-bit AES is intentionally unsupported (http://crbug.com/533699).
switch (key_length_bytes) {
case 16:
return EVP_aes_128_cbc();
case 32:
return EVP_aes_256_cbc();
default:
return nullptr;
}
}
Status AesCbcEncryptDecrypt(EncryptOrDecrypt cipher_operation,
const blink::WebCryptoAlgorithm& algorithm,
const blink::WebCryptoKey& key,
base::span<const uint8_t> data,
std::vector<uint8_t>* buffer) {
crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
const blink::WebCryptoAesCbcParams* params = algorithm.AesCbcParams();
const std::vector<uint8_t>& raw_key = GetSymmetricKeyData(key);
if (params->Iv().size() != 16)
return Status::ErrorIncorrectSizeAesCbcIv();
// According to the openssl docs, the amount of data written may be as large
// as (data_size + cipher_block_size - 1), constrained to a multiple of
// cipher_block_size.
base::CheckedNumeric<int> output_max_len = data.size();
output_max_len += AES_BLOCK_SIZE - 1;
if (!output_max_len.IsValid())
return Status::ErrorDataTooLarge();
const unsigned remainder =
base::ValueOrDieForType<unsigned>(output_max_len % AES_BLOCK_SIZE);
if (remainder != 0)
output_max_len += AES_BLOCK_SIZE - remainder;
if (!output_max_len.IsValid())
return Status::ErrorDataTooLarge();
// Note: PKCS padding is enabled by default
const EVP_CIPHER* const cipher = GetAESCipherByKeyLength(raw_key.size());
DCHECK(cipher);
bssl::ScopedEVP_CIPHER_CTX context;
if (!EVP_CipherInit_ex(context.get(), cipher, nullptr, &raw_key[0],
params->Iv().data(), cipher_operation)) {
return Status::OperationError();
}
buffer->resize(base::ValueOrDieForType<size_t>(output_max_len));
int output_len = 0;
if (!EVP_CipherUpdate(context.get(), buffer->data(), &output_len, data.data(),
base::checked_cast<int>(data.size()))) {
return Status::OperationError();
}
int final_output_chunk_len = 0;
if (!EVP_CipherFinal_ex(context.get(), buffer->data() + output_len,
&final_output_chunk_len)) {
return Status::OperationError();
}
const unsigned int final_output_len =
static_cast<unsigned int>(output_len) +
static_cast<unsigned int>(final_output_chunk_len);
buffer->resize(final_output_len);
return Status::Success();
}
class AesCbcImplementation : public AesAlgorithm {
public:
AesCbcImplementation() : AesAlgorithm("CBC") {}
Status Encrypt(const blink::WebCryptoAlgorithm& algorithm,
const blink::WebCryptoKey& key,
base::span<const uint8_t> data,
std::vector<uint8_t>* buffer) const override {
return AesCbcEncryptDecrypt(ENCRYPT, algorithm, key, data, buffer);
}
Status Decrypt(const blink::WebCryptoAlgorithm& algorithm,
const blink::WebCryptoKey& key,
base::span<const uint8_t> data,
std::vector<uint8_t>* buffer) const override {
return AesCbcEncryptDecrypt(DECRYPT, algorithm, key, data, buffer);
}
};
} // namespace
std::unique_ptr<AlgorithmImplementation> CreateAesCbcImplementation() {
return std::make_unique<AesCbcImplementation>();
}
} // namespace webcrypto
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