kepka/Telegram/SourceFiles/mtproto/auth_key.h

//
// This file is part of Kepka,
// an unofficial desktop version of Telegram messaging app,
// see https://github.com/procxx/kepka
//
// Kepka is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// It is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// In addition, as a special exception, the copyright holders give permission
// to link the code of portions of this program with the OpenSSL library.
//
// Full license: https://github.com/procxx/kepka/blob/master/LICENSE
// Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
// Copyright (c) 2017- Kepka Contributors, https://github.com/procxx
//
#pragma once

#include <array>
#include <memory>

#include "mtproto/core_types.h"
#include <QDataStream>
#include <QtGlobal>
#include <gsl/gsl_byte>

namespace MTP {

class AuthKey {
public:
	static constexpr auto kSize = 256; // 2048 bits.
	using Data = std::array<gsl::byte, kSize>;
	using KeyId = quint64;

	enum class Type {
		Generated,
		ReadFromFile,
		Local,
	};
	AuthKey(Type type, DcId dcId, const Data &data)
	    : _type(type)
	    , _dcId(dcId)
	    , _key(data) {
		countKeyId();
	}
	AuthKey(const Data &data)
	    : _type(Type::Local)
	    , _key(data) {
		countKeyId();
	}

	AuthKey(const AuthKey &other) = delete;
	AuthKey &operator=(const AuthKey &other) = delete;

	Type type() const {
		return _type;
	}

	int dcId() const {
		return _dcId;
	}

	KeyId keyId() const {
		return _keyId;
	}

	void prepareAES_oldmtp(const MTPint128 &msgKey, MTPint256 &aesKey, MTPint256 &aesIV, bool send) const;
	void prepareAES(const MTPint128 &msgKey, MTPint256 &aesKey, MTPint256 &aesIV, bool send) const;

	const void *partForMsgKey(bool send) const {
		return _key.data() + 88 + (send ? 0 : 8);
	}

	void write(QDataStream &to) const {
		to.writeRawData(reinterpret_cast<const char *>(_key.data()), static_cast<int>(_key.size()));
	}

	bool equals(const std::shared_ptr<AuthKey> &other) const {
		return other ? (_key == other->_key) : false;
	}

	static void FillData(Data &authKey, base::const_byte_span computedAuthKey) {
		auto computedAuthKeySize = computedAuthKey.size();
		Assert(computedAuthKeySize <= kSize);
		auto authKeyBytes = gsl::make_span(authKey);
		if (computedAuthKeySize < kSize) {
			base::set_bytes(authKeyBytes.subspan(0, kSize - computedAuthKeySize), gsl::byte());
			base::copy_bytes(authKeyBytes.subspan(kSize - computedAuthKeySize), computedAuthKey);
		} else {
			base::copy_bytes(authKeyBytes, computedAuthKey);
		}
	}

private:
	void countKeyId() {
		auto sha1 = hashSha1(_key.data(), _key.size());

		// Lower 64 bits = 8 bytes of 20 byte SHA1 hash.
		_keyId = *reinterpret_cast<KeyId *>(sha1.data() + 12);
	}

	Type _type = Type::Generated;
	DcId _dcId = 0;
	Data _key = {{gsl::byte{}}};
	KeyId _keyId = 0;
};

using AuthKeyPtr = std::shared_ptr<AuthKey>;
using AuthKeysList = std::vector<AuthKeyPtr>;

void aesIgeEncryptRaw(const void *src, void *dst, quint32 len, const void *key, const void *iv);
void aesIgeDecryptRaw(const void *src, void *dst, quint32 len, const void *key, const void *iv);

inline void aesIgeEncrypt_oldmtp(const void *src, void *dst, quint32 len, const AuthKeyPtr &authKey,
                                 const MTPint128 &msgKey) {
	MTPint256 aesKey, aesIV;
	authKey->prepareAES_oldmtp(msgKey, aesKey, aesIV, true);

	return aesIgeEncryptRaw(src, dst, len, static_cast<const void *>(&aesKey), static_cast<const void *>(&aesIV));
}

inline void aesIgeEncrypt(const void *src, void *dst, quint32 len, const AuthKeyPtr &authKey, const MTPint128 &msgKey) {
	MTPint256 aesKey, aesIV;
	authKey->prepareAES(msgKey, aesKey, aesIV, true);

	return aesIgeEncryptRaw(src, dst, len, static_cast<const void *>(&aesKey), static_cast<const void *>(&aesIV));
}

inline void aesEncryptLocal(const void *src, void *dst, quint32 len, const AuthKeyPtr &authKey, const void *key128) {
	MTPint256 aesKey, aesIV;
	authKey->prepareAES_oldmtp(*(const MTPint128 *)key128, aesKey, aesIV, false);

	return aesIgeEncryptRaw(src, dst, len, static_cast<const void *>(&aesKey), static_cast<const void *>(&aesIV));
}

inline void aesIgeDecrypt_oldmtp(const void *src, void *dst, quint32 len, const AuthKeyPtr &authKey,
                                 const MTPint128 &msgKey) {
	MTPint256 aesKey, aesIV;
	authKey->prepareAES_oldmtp(msgKey, aesKey, aesIV, false);

	return aesIgeDecryptRaw(src, dst, len, static_cast<const void *>(&aesKey), static_cast<const void *>(&aesIV));
}

inline void aesIgeDecrypt(const void *src, void *dst, quint32 len, const AuthKeyPtr &authKey, const MTPint128 &msgKey) {
	MTPint256 aesKey, aesIV;
	authKey->prepareAES(msgKey, aesKey, aesIV, false);

	return aesIgeDecryptRaw(src, dst, len, static_cast<const void *>(&aesKey), static_cast<const void *>(&aesIV));
}

inline void aesDecryptLocal(const void *src, void *dst, quint32 len, const AuthKeyPtr &authKey, const void *key128) {
	MTPint256 aesKey, aesIV;
	authKey->prepareAES_oldmtp(*(const MTPint128 *)key128, aesKey, aesIV, false);

	return aesIgeDecryptRaw(src, dst, len, static_cast<const void *>(&aesKey), static_cast<const void *>(&aesIV));
}

// ctr used inplace, encrypt the data and leave it at the same place
struct CTRState {
	static constexpr int KeySize = 32;
	static constexpr int IvecSize = 16;
	static constexpr int EcountSize = 16;

	uchar ivec[IvecSize] = {0};
	quint32 num = 0;
	uchar ecount[EcountSize] = {0};
};
void aesCtrEncrypt(void *data, quint32 len, const void *key, CTRState *state);

} // namespace MTP