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// Copyright 2012 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/encryptor.h"
#include <stddef.h>
#include <stdint.h>
#include "base/logging.h"
#include "base/strings/string_util.h"
#include "base/sys_byteorder.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/evp.h"
namespace crypto {
namespace {
const EVP_CIPHER* GetCipherForKey(const SymmetricKey* key) {
switch (key->key().length()) {
case 16: return EVP_aes_128_cbc();
case 32: return EVP_aes_256_cbc();
default:
return nullptr;
}
}
} // namespace
/////////////////////////////////////////////////////////////////////////////
// Encryptor Implementation.
Encryptor::Encryptor() : key_(nullptr), mode_(CBC) {}
Encryptor::~Encryptor() = default;
bool Encryptor::Init(const SymmetricKey* key, Mode mode, std::string_view iv) {
return Init(key, mode, base::as_bytes(base::make_span(iv)));
}
bool Encryptor::Init(const SymmetricKey* key,
Mode mode,
base::span<const uint8_t> iv) {
DCHECK(key);
DCHECK(mode == CBC || mode == CTR);
EnsureOpenSSLInit();
if (mode == CBC && iv.size() != AES_BLOCK_SIZE)
return false;
// CTR mode passes the starting counter separately, via SetCounter().
if (mode == CTR && !iv.empty())
return false;
if (GetCipherForKey(key) == nullptr)
return false;
key_ = key;
mode_ = mode;
iv_.assign(iv.begin(), iv.end());
return true;
}
bool Encryptor::Encrypt(std::string_view plaintext, std::string* ciphertext) {
return CryptString(/*do_encrypt=*/true, plaintext, ciphertext);
}
bool Encryptor::Encrypt(base::span<const uint8_t> plaintext,
std::vector<uint8_t>* ciphertext) {
return CryptBytes(/*do_encrypt=*/true, plaintext, ciphertext);
}
bool Encryptor::Decrypt(std::string_view ciphertext, std::string* plaintext) {
return CryptString(/*do_encrypt=*/false, ciphertext, plaintext);
}
bool Encryptor::Decrypt(base::span<const uint8_t> ciphertext,
std::vector<uint8_t>* plaintext) {
return CryptBytes(/*do_encrypt=*/false, ciphertext, plaintext);
}
bool Encryptor::SetCounter(std::string_view counter) {
return SetCounter(base::as_bytes(base::make_span(counter)));
}
bool Encryptor::SetCounter(base::span<const uint8_t> counter) {
if (mode_ != CTR)
return false;
if (counter.size() != 16u)
return false;
iv_.assign(counter.begin(), counter.end());
return true;
}
bool Encryptor::CryptString(bool do_encrypt,
std::string_view input,
std::string* output) {
std::string result(MaxOutput(do_encrypt, input.size()), '\0');
absl::optional<size_t> len =
(mode_ == CTR)
? CryptCTR(do_encrypt, base::as_bytes(base::make_span(input)),
base::as_writable_bytes(base::make_span(result)))
: Crypt(do_encrypt, base::as_bytes(base::make_span(input)),
base::as_writable_bytes(base::make_span(result)));
if (!len)
return false;
result.resize(*len);
*output = std::move(result);
return true;
}
bool Encryptor::CryptBytes(bool do_encrypt,
base::span<const uint8_t> input,
std::vector<uint8_t>* output) {
std::vector<uint8_t> result(MaxOutput(do_encrypt, input.size()));
absl::optional<size_t> len = (mode_ == CTR)
? CryptCTR(do_encrypt, input, result)
: Crypt(do_encrypt, input, result);
if (!len)
return false;
result.resize(*len);
*output = std::move(result);
return true;
}
size_t Encryptor::MaxOutput(bool do_encrypt, size_t length) {
size_t result = length + ((do_encrypt && mode_ == CBC) ? 16 : 0);
CHECK_GE(result, length); // Overflow
return result;
}
absl::optional<size_t> Encryptor::Crypt(bool do_encrypt,
base::span<const uint8_t> input,
base::span<uint8_t> output) {
DCHECK(key_); // Must call Init() before En/De-crypt.
const EVP_CIPHER* cipher = GetCipherForKey(key_);
DCHECK(cipher); // Already handled in Init();
const std::string& key = key_->key();
DCHECK_EQ(EVP_CIPHER_iv_length(cipher), iv_.size());
DCHECK_EQ(EVP_CIPHER_key_length(cipher), key.size());
OpenSSLErrStackTracer err_tracer(FROM_HERE);
bssl::ScopedEVP_CIPHER_CTX ctx;
if (!EVP_CipherInit_ex(ctx.get(), cipher, nullptr,
reinterpret_cast<const uint8_t*>(key.data()),
iv_.data(), do_encrypt)) {
return absl::nullopt;
}
// Encrypting needs a block size of space to allow for any padding.
CHECK_GE(output.size(), input.size() + (do_encrypt ? iv_.size() : 0));
int out_len;
if (!EVP_CipherUpdate(ctx.get(), output.data(), &out_len, input.data(),
input.size()))
return absl::nullopt;
// Write out the final block plus padding (if any) to the end of the data
// just written.
int tail_len;
if (!EVP_CipherFinal_ex(ctx.get(), output.data() + out_len, &tail_len))
return absl::nullopt;
out_len += tail_len;
DCHECK_LE(out_len, static_cast<int>(output.size()));
return out_len;
}
absl::optional<size_t> Encryptor::CryptCTR(bool do_encrypt,
base::span<const uint8_t> input,
base::span<uint8_t> output) {
if (iv_.size() != AES_BLOCK_SIZE) {
LOG(ERROR) << "Counter value not set in CTR mode.";
return absl::nullopt;
}
AES_KEY aes_key;
if (AES_set_encrypt_key(reinterpret_cast<const uint8_t*>(key_->key().data()),
key_->key().size() * 8, &aes_key) != 0) {
return absl::nullopt;
}
uint8_t ecount_buf[AES_BLOCK_SIZE] = { 0 };
unsigned int block_offset = 0;
// |output| must have room for |input|.
CHECK_GE(output.size(), input.size());
// Note AES_ctr128_encrypt() will update |iv_|. However, this method discards
// |ecount_buf| and |block_offset|, so this is not quite a streaming API.
AES_ctr128_encrypt(input.data(), output.data(), input.size(), &aes_key,
iv_.data(), ecount_buf, &block_offset);
return input.size();
}
} // namespace crypto
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