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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "crypto/aes_cbc.h"
#include "base/check.h"
#include "base/check_op.h"
#include "crypto/openssl_util.h"
#include "third_party/boringssl/src/include/openssl/aes.h"
#include "third_party/boringssl/src/include/openssl/evp.h"
namespace crypto::aes_cbc {
std::vector<uint8_t> Encrypt(base::span<const uint8_t> key,
base::span<const uint8_t, kBlockSize> iv,
base::span<const uint8_t> plaintext) {
const EVP_CIPHER* cipher =
key.size() == 32 ? EVP_aes_256_cbc() : EVP_aes_128_cbc();
CHECK_EQ(EVP_CIPHER_key_length(cipher), key.size());
OpenSSLErrStackTracer err_tracer(FROM_HERE);
bssl::ScopedEVP_CIPHER_CTX ctx;
CHECK(EVP_EncryptInit_ex(ctx.get(), cipher, nullptr, key.data(), iv.data()));
std::vector<uint8_t> ciphertext(plaintext.size() + kBlockSize);
int out_len;
CHECK(EVP_EncryptUpdate(ctx.get(), ciphertext.data(), &out_len,
plaintext.data(), plaintext.size()));
int tail_len;
CHECK(EVP_EncryptFinal_ex(ctx.get(),
// SAFETY: boringssl guarantees out_len is still
// inside ciphertext.
UNSAFE_BUFFERS(ciphertext.data() + out_len),
&tail_len));
ciphertext.resize(out_len + tail_len);
return ciphertext;
}
std::optional<std::vector<uint8_t>> Decrypt(
base::span<const uint8_t> key,
base::span<const uint8_t, kBlockSize> iv,
base::span<const uint8_t> ciphertext) {
const EVP_CIPHER* cipher =
key.size() == 32 ? EVP_aes_256_cbc() : EVP_aes_128_cbc();
OpenSSLErrStackTracer err_tracer(FROM_HERE);
bssl::ScopedEVP_CIPHER_CTX ctx;
CHECK(EVP_DecryptInit_ex(ctx.get(), cipher, nullptr, key.data(), iv.data()));
std::vector<uint8_t> plaintext(ciphertext.size());
int out_len;
CHECK(EVP_DecryptUpdate(ctx.get(), plaintext.data(), &out_len,
ciphertext.data(), ciphertext.size()));
int tail_len;
if (!EVP_DecryptFinal_ex(ctx.get(),
// SAFETY: boringssl guarantees out_len is still
// inside ciphertext.
UNSAFE_BUFFERS(plaintext.data() + out_len),
&tail_len)) {
return std::nullopt;
}
plaintext.resize(out_len + tail_len);
return plaintext;
}
} // namespace crypto::aes_cbc
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