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aes-256-ctr.hpp
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aes-256-ctr.hpp
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/*
* This file is part of libkazv.
* SPDX-FileCopyrightText: 2020-2021 Tusooa Zhu <tusooa@kazv.moe>
* SPDX-License-Identifier: AGPL-3.0-or-later
*/
#pragma once
#include <libkazv-config.hpp>
#include <memory>
#include <copy-helper.hpp>
#include "crypto-util.hpp"
namespace Kazv
{
namespace
{
using std::begin;
using std::end;
}
class AES256CTRDesc
{
public:
/// The optimal block size for this cipher.
inline static const int optimalBlockSize{16};
/// The key size for this cipher.
inline static const int keySize{32};
/// The iv size for this cipher.
inline static const int ivSize{16}; // AES block size
/// Random size to generate a new cipher, provided in fromRandom().
inline static const int randomSize{keySize + ivSize};
using DataT = std::string;
private:
struct RawTag {};
/**
* Constructs an AES-256-CTR cipher using `key` and `iv`.
*
* `key` and `iv` are provided as-is.
*
* `key` must be of size `keySize` and `iv` must be of size `ivSize`.
* Otherwise, the constructed cipher is invalid.
*/
AES256CTRDesc(RawTag, DataT key, DataT iv);
public:
/**
* Constructs an AES-256-CTR cipher using `key` and `iv`.
*
* `key` is provided as urlsafe unpadded base64.
* `iv` is provided as unpadded base64.
*
* One must check with `valid()` before actual processing with
* the object if the key and iv comes from a remote Matrix event.
*/
AES256CTRDesc(std::string key, std::string iv);
/**
* Generate a new AES-256-CTR cipher from random data.
*
* @param random The random data provided as-is. `random.size()`
* must be at least `randomSize`.
*
* The first keySize bytes will be used as the key, and the
* next ivSize bytes will be used as the iv.
*
* @return An AES-256-CTR cipher generated with the random data.
*/
template<class RangeT>
static AES256CTRDesc fromRandom(RangeT random) {
if (random.size() < randomSize) {
// Not enough random, return an invalid one
return AES256CTRDesc(RawTag{}, DataT(), DataT());
}
return AES256CTRDesc(RawTag{},
DataT(random.begin(), random.begin() + keySize),
DataT(random.begin() + keySize, random.begin() + keySize + ivSize));
}
KAZV_DECLARE_COPYABLE(AES256CTRDesc)
~AES256CTRDesc();
/**
* @return whether this cipher is valid. If the cipher is invalid, you
* must not use any method except destructor or operator=().
*/
bool valid() const;
/// @return The key encoded as urlsafe unpadded base64.
std::string key() const;
/// @return The iv encoded as unpadded base64.
std::string iv() const;
template<class RangeT>
using ResultBase = std::pair<AES256CTRDesc, RangeT>;
using Result = ResultBase<DataT>;
/**
* Encrypts or decrypts `data` and derives the next cipher state.
*
* @param data The data to encrypt or decrypt.
*
* Example:
*
* auto cipher = Kazv::AES256CTRDesc(
* Kazv::genRandom(Kazv::AES256CTRDesc::keySize),
* Kazv::genRandom(Kazv::AES256CTRDesc::ivSize)
* );
* std::string original = "Some test here";
* auto [next, encrypted] = cipher.process(original);
* auto [next2, encrypted2] = cipher.process(original);
* REQUIRE(encrypted == encrypted2);
*
* @return an object that can be destructured into the next cipher state
* (as AES256CTRDesc) and the encrypted or decrypted data (as DataT).
*/
Result process(DataT data) const &;
/**
* Encrypts or decrypts `data` and derives the next cipher state.
*
* This function only differs from the above in that it takes any range type
* and the second component of returned object is of the same type as the argument.
*/
template<class RangeT,
class = std::enable_if_t<!std::is_same_v<std::decay_t<RangeT>, DataT>, int>>
ResultBase<std::decay_t<RangeT>> process(RangeT data) const & {
using ActualRangeT = std::decay_t<RangeT>;
auto [next, res] = process(DataT(begin(data), end(data)));
return { next, ActualRangeT(res.begin(), res.end()) };
}
/**
* Encrypts or decrypts `data` and derives the next cipher state.
*
* This function differs from the above two only in that its calling object
* is an rvalue reference (a.k.a casted using std::move()).
*/
Result process(DataT data) &&;
/**
* Encrypts or decrypts `data` and derives the next cipher state.
*
* This function differs from the above only in that it takes any range type
* and the second component of returned object is of the same type as the argument.
*/
template<class RangeT,
class = std::enable_if_t<!std::is_same_v<std::decay_t<RangeT>, DataT>, int>>
ResultBase<std::decay_t<RangeT>> process(RangeT data) && {
using ActualRangeT = std::decay_t<RangeT>;
auto [next, res] = std::move(*this).process(DataT(begin(data), end(data)));
return { next, ActualRangeT(res.begin(), res.end()) };
}
/**
* Encrypt or decrypt `data` and modify the state of the cipher in-place.
*
* @param data The data to encrypt or decrypt.
*/
DataT processInPlace(DataT data);
/**
* Encrypt or decrypt `data` and modify the state of the cipher in-place.
*
* This function differs from the above only in that it takes any range type
* and returns the processed data as the same range type.
*/
template<class RangeT,
class = std::enable_if_t<!std::is_same_v<std::decay_t<RangeT>, DataT>, int>>
std::decay_t<RangeT> processInPlace(RangeT data) {
using ActualRangeT = std::decay_t<RangeT>;
auto res = processInPlace(DataT(begin(data), end(data)));
return ActualRangeT(res.begin(), res.end());
}
private:
struct Private;
std::unique_ptr<Private> m_d;
};
}

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