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	/*
	* Copyright (C) 2020-2021 Tusooa Zhu <tusooa@kazv.moe>
	*
	* This file is part of libkazv.
	*
	* libkazv is free software: you can redistribute it and/or modify
	* it under the terms of the GNU Affero General Public License as
	* published by the Free Software Foundation, either version 3 of the
	* License, or (at your option) any later version.
	*
	* libkazv 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 Affero General Public License for more details.
	*
	* You should have received a copy of the GNU Affero General Public License
	* along with libkazv. If not, see <https://www.gnu.org/licenses/>.
	*/

	#include <libkazv-config.hpp>

	#include <vector>

	#include <zug/transducer/filter.hpp>

	#include <olm/olm.h>

	#include <nlohmann/json.hpp>

	#include <debug.hpp>
	#include <event.hpp>
	#include <cursorutil.hpp>
	#include <types.hpp>

	#include "crypto-p.hpp"
	#include "session-p.hpp"

	#include "crypto-util.hpp"
	#include "time-util.hpp"

	namespace Kazv
	{
	using namespace CryptoConstants;

	CryptoPrivate::CryptoPrivate()
	: accountData(olm_account_size(), 0)
	, account(olm_account(accountData.data()))
	, utilityData(olm_utility_size(), '\0')
	, utility(olm_utility(utilityData.data()))
	{
	auto randLen = Crypto::constructRandomSize();
	auto randomData = genRandom(randLen);
	checkError(olm_create_account(account, randomData.data(), randLen));
	}

	CryptoPrivate::CryptoPrivate(RandomTag, RandomData data)
	: accountData(olm_account_size(), 0)
	, account(olm_account(accountData.data()))
	, utilityData(olm_utility_size(), '\0')
	, utility(olm_utility(utilityData.data()))
	{
	auto randLenNeeded = Crypto::constructRandomSize();
	checkError(olm_create_account(account, data.data(), randLenNeeded));
	}


	CryptoPrivate::~CryptoPrivate()
	{
	olm_clear_account(account);
	}

	CryptoPrivate::CryptoPrivate(const CryptoPrivate &that)
	: accountData(olm_account_size(), 0)
	, account(olm_account(accountData.data()))
	, uploadedOneTimeKeysCount(that.uploadedOneTimeKeysCount)
	, numUnpublishedKeys(that.numUnpublishedKeys)
	, knownSessions(that.knownSessions)
	, inboundGroupSessions(that.inboundGroupSessions)
	, outboundGroupSessions(that.outboundGroupSessions)
	, utilityData(olm_utility_size(), '\0')
	, utility(olm_utility(utilityData.data()))
	{
	unpickle(that.pickle());
	}

	std::string CryptoPrivate::pickle() const
	{
	auto key = ByteArray(3, 'x');
	auto pickleData = std::string(olm_pickle_account_length(account), '\0');
	checkError(olm_pickle_account(account, key.data(), key.size(),
	pickleData.data(), pickleData.size()));
	return pickleData;
	}

	void CryptoPrivate::unpickle(std::string pickleData)
	{
	auto key = ByteArray(3, 'x');
	checkError(olm_unpickle_account(account, key.data(), key.size(),
	pickleData.data(), pickleData.size()));
	}

	std::size_t CryptoPrivate::checkError(std::size_t code) const
	{
	if (code == olm_error()) {
	kzo.crypto.warn() << "Olm error: " << olm_account_last_error(account) << std::endl;
	}
	return code;
	}

	std::size_t CryptoPrivate::checkUtilError(std::size_t code) const
	{
	if (code == olm_error()) {
	kzo.crypto.warn() << "Olm utility error: " << olm_utility_last_error(utility) << std::endl;
	}
	return code;
	}


	MaybeString CryptoPrivate::decryptOlm(nlohmann::json content)
	{
	auto theirCurve25519IdentityKey = content.at("sender_key").get<std::string>();

	auto ourCurve25519IdentityKey = curve25519IdentityKey();

	if (! content.at("ciphertext").contains(ourCurve25519IdentityKey)) {
	return NotBut("Message not intended for us");
	}

	auto type = content.at("ciphertext").at(ourCurve25519IdentityKey).at("type").get<int>();
	auto body = content.at("ciphertext").at(ourCurve25519IdentityKey).at("body").get<std::string>();

	auto hasKnownSession = knownSessions.find(theirCurve25519IdentityKey) != knownSessions.end();

	if (type == 0) { // pre-key message
	bool shouldCreateNewSession =
	// there is no possible session
	(! hasKnownSession)
	// the possible session does not match this message
	\|\| (! knownSessions.at(theirCurve25519IdentityKey).matches(body));

	if (shouldCreateNewSession) {
	auto created = createInboundSession(theirCurve25519IdentityKey, body);
	if (! created) { // cannot create session, thus cannot decrypt
	return NotBut("Cannot create session");
	}
	}

	auto &session = knownSessions.at(theirCurve25519IdentityKey);

	return session.decrypt(type, body);
	} else {
	if (! hasKnownSession) {
	return NotBut("No available session");
	}

	auto &session = knownSessions.at(theirCurve25519IdentityKey);
	return session.decrypt(type, body);
	}
	}

	MaybeString CryptoPrivate::decryptMegOlm(nlohmann::json eventJson)
	{
	auto content = eventJson.at("content");

	auto senderKey = content.at("sender_key").get<std::string>();
	auto sessionId = content.at("session_id").get<std::string>();
	auto roomId = eventJson.at("room_id").get<std::string>();

	auto k = KeyOfGroupSession{roomId, senderKey, sessionId};

	if (inboundGroupSessions.find(k) == inboundGroupSessions.end()) {
	return NotBut("We do not have the keys for this");
	} else {
	auto msg = content.at("ciphertext").get<std::string>();
	auto eventId = eventJson.at("event_id").get<std::string>();
	auto originServerTs = eventJson.at("origin_server_ts").get<Timestamp>();
	auto &session = inboundGroupSessions.at(k);

	return session.decrypt(msg, eventId, originServerTs);
	}
	}

	bool CryptoPrivate::createInboundSession(std::string theirCurve25519IdentityKey,
	std::string message)
	{
	auto s = Session(InboundSessionTag{}, account,
	theirCurve25519IdentityKey, message);

	if (s.valid()) {
	checkError(olm_remove_one_time_keys(account, s.m_d->session));
	knownSessions.insert_or_assign(theirCurve25519IdentityKey, std::move(s));
	return true;
	}

	return false;
	}

	bool CryptoPrivate::reuseOrCreateOutboundGroupSession(
	RandomData random, Timestamp timeMs,
	std::string roomId, std::optional<MegOlmSessionRotateDesc> desc)
	{
	bool valid = true;
	if (! desc.has_value()) { // force rotate
	valid = false;
	} else {
	auto it = outboundGroupSessions.find(roomId);
	if (it == outboundGroupSessions.end()) {
	valid = false;
	} else {
	auto &session = it->second;
	if (timeMs - session.creationTimeMs() >= desc.value().ms) {
	valid = false;
	} else if (session.messageIndex() >= desc.value().messages) {
	valid = false;
	}
	}
	}

	if (! valid) {
	outboundGroupSessions.insert_or_assign(roomId, OutboundGroupSession(RandomTag{}, random, timeMs));
	auto &session = outboundGroupSessions.at(roomId);
	auto sessionId = session.sessionId();
	auto sessionKey = session.sessionKey();
	auto senderKey = curve25519IdentityKey();

	auto k = KeyOfGroupSession{roomId, senderKey, sessionId};

	if (! createInboundGroupSession(k, sessionKey, ed25519IdentityKey())) {
	kzo.client.warn() << "Create inbound group session from outbound group session failed. We may not be able to read our own messages." << std::endl;
	}
	}
	return valid;
	}


	std::size_t Crypto::constructRandomSize()
	{
	static std::size_t s =
	[] {
	std::vector<char> acc(olm_account_size(), 0);
	OlmAccount *account = olm_account(acc.data());
	return olm_create_account_random_length(account);
	}();
	return s;
	}

	Crypto::Crypto()
	: m_d(new CryptoPrivate{})
	{
	}

	Crypto::Crypto(RandomTag, RandomData data)
	: m_d(new CryptoPrivate(RandomTag{}, std::move(data)))
	{
	}

	Crypto::~Crypto() = default;

	Crypto::Crypto(const Crypto &that)
	: m_d(new CryptoPrivate(*that.m_d))
	{
	}

	Crypto::Crypto(Crypto &&that)
	: m_d(std::move(that.m_d))
	{
	}

	Crypto &Crypto::operator=(const Crypto &that)
	{
	m_d.reset(new CryptoPrivate(*that.m_d));
	return *this;
	}

	Crypto &Crypto::operator=(Crypto &&that)
	{
	m_d = std::move(that.m_d);
	return *this;
	}

	ByteArray CryptoPrivate::identityKeys()
	{
	auto ret = ByteArray(olm_account_identity_keys_length(account), '\0');
	checkError(olm_account_identity_keys(account, ret.data(), ret.size()));
	return ret;
	}

	std::string CryptoPrivate::ed25519IdentityKey()
	{
	auto keys = identityKeys();
	auto keyStr = std::string(keys.begin(), keys.end());
	auto keyJson = nlohmann::json::parse(keyStr);
	return keyJson.at(ed25519);
	}

	std::string CryptoPrivate::curve25519IdentityKey()
	{
	auto keys = identityKeys();
	auto keyStr = std::string(keys.begin(), keys.end());
	auto keyJson = nlohmann::json::parse(keyStr);
	return keyJson.at(curve25519);
	}

	std::string Crypto::ed25519IdentityKey()
	{
	return m_d->ed25519IdentityKey();
	}

	std::string Crypto::curve25519IdentityKey()
	{
	return m_d->curve25519IdentityKey();
	}

	std::string Crypto::sign(nlohmann::json j)
	{
	j.erase("signatures");
	j.erase("unsigned");

	auto str = j.dump();

	auto ret = ByteArray(olm_account_signature_length(m_d->account), '\0');

	kzo.crypto.dbg() << "We are about to sign: " << str << std::endl;

	m_d->checkError(olm_account_sign(m_d->account,
	str.data(), str.size(),
	ret.data(), ret.size()));

	return std::string{ret.begin(), ret.end()};
	}

	void Crypto::setUploadedOneTimeKeysCount(immer::map<std::string /* algorithm */, int> uploadedOneTimeKeysCount)
	{
	m_d->uploadedOneTimeKeysCount = uploadedOneTimeKeysCount;
	}

	int Crypto::maxNumberOfOneTimeKeys()
	{
	return olm_account_max_number_of_one_time_keys(m_d->account);
	}

	std::size_t Crypto::genOneTimeKeysRandomSize(int num)
	{
	static std::size_t oneKeyRandomSize =
	[] {
	std::vector<char> acc(olm_account_size(), 0);
	OlmAccount *account = olm_account(acc.data());
	return olm_account_generate_one_time_keys_random_length(account, 1);
	}();

	return oneKeyRandomSize * num;
	}

	void Crypto::genOneTimeKeys(int num)
	{
	auto random = genRandomData(genOneTimeKeysRandomSize(num));
	genOneTimeKeysWithRandom(std::move(random), num);
	}

	void Crypto::genOneTimeKeysWithRandom(RandomData random, int num)
	{
	assert(random.size() >= genOneTimeKeysRandomSize(num));

	auto res = m_d->checkError(
	olm_account_generate_one_time_keys(
	m_d->account,
	num,
	random.data(), random.size()));

	if (res != olm_error()) {
	m_d->numUnpublishedKeys += num;
	}
	}


	nlohmann::json Crypto::unpublishedOneTimeKeys()
	{
	auto keys = ByteArray(olm_account_one_time_keys_length(m_d->account), '\0');
	m_d->checkError(olm_account_one_time_keys(m_d->account, keys.data(), keys.size()));

	return nlohmann::json::parse(std::string(keys.begin(), keys.end()));
	}

	void Crypto::markOneTimeKeysAsPublished()
	{
	auto ret = m_d->checkError(olm_account_mark_keys_as_published(m_d->account));
	if (ret != olm_error()) {
	m_d->numUnpublishedKeys = 0;
	}
	}

	int Crypto::numUnpublishedOneTimeKeys() const
	{
	return m_d->numUnpublishedKeys;
	}

	int Crypto::uploadedOneTimeKeysCount(std::string algorithm) const
	{
	return m_d->uploadedOneTimeKeysCount[algorithm];
	}

	MaybeString Crypto::decrypt(nlohmann::json eventJson)
	{
	auto content = eventJson.at("content");
	auto algo = content.at("algorithm").get<std::string>();
	if (algo == olmAlgo) {
	return m_d->decryptOlm(std::move(content));
	} else if (algo == megOlmAlgo) {
	return m_d->decryptMegOlm(eventJson);
	}
	return NotBut("Algorithm " + algo + " not supported");
	}

	bool Crypto::createInboundGroupSession(KeyOfGroupSession k, std::string sessionKey, std::string ed25519Key)
	{
	return m_d->createInboundGroupSession(std::move(k), std::move(sessionKey), std::move(ed25519Key));
	}

	bool CryptoPrivate::createInboundGroupSession(KeyOfGroupSession k, std::string sessionKey, std::string ed25519Key)
	{
	auto session = InboundGroupSession(sessionKey, ed25519Key);
	if (session.valid()) {
	inboundGroupSessions.insert_or_assign(k, std::move(session));
	return true;
	}
	return false;
	}

	bool Crypto::verify(nlohmann::json object, std::string userId, std::string deviceId, std::string ed25519Key)
	{
	if (! object.contains("signatures")) {
	return false;
	}
	std::string signature;
	try {
	signature = object.at("signatures").at(userId).at(ed25519 + ":" + deviceId);
	} catch(const std::exception &) {
	return false;
	}
	object.erase("signatures");
	object.erase("unsigned");

	auto message = object.dump();

	auto res = m_d->checkUtilError(
	olm_ed25519_verify(m_d->utility,
	ed25519Key.c_str(), ed25519Key.size(),
	message.c_str(), message.size(),
	signature.data(), signature.size()));

	return res != olm_error();
	}

	MaybeString Crypto::getInboundGroupSessionEd25519KeyFromEvent(const nlohmann::json &eventJson) const
	{
	auto content = eventJson.at("content");

	auto senderKey = content.at("sender_key").get<std::string>();
	auto sessionId = content.at("session_id").get<std::string>();
	auto roomId = eventJson.at("room_id").get<std::string>();

	auto k = KeyOfGroupSession{roomId, senderKey, sessionId};

	if (m_d->inboundGroupSessions.find(k) == m_d->inboundGroupSessions.end()) {
	return NotBut("We do not have the keys for this");
	} else {
	auto &session = m_d->inboundGroupSessions.at(k);
	return session.ed25519Key();
	}
	}

	nlohmann::json Crypto::encryptOlm(nlohmann::json eventJson, std::string theirCurve25519IdentityKey)
	{
	try {
	auto &session = m_d->knownSessions.at(theirCurve25519IdentityKey);
	auto [type, body] = session.encrypt(eventJson.dump());
	return nlohmann::json{
	{
	theirCurve25519IdentityKey, {
	{"type", type},
	{"body", body}
	}
	}
	};
	} catch (const std::exception &) {
	return nlohmann::json::object();
	}
	}

	nlohmann::json Crypto::encryptMegOlm(nlohmann::json eventJson)
	{
	auto roomId = eventJson.at("room_id").get<std::string>();
	auto content = eventJson.at("content");
	auto type = eventJson.at("type").get<std::string>();

	auto jsonToEncrypt = nlohmann::json::object();
	jsonToEncrypt["room_id"] = roomId;
	jsonToEncrypt["content"] = std::move(content);
	jsonToEncrypt["type"] = type;

	auto textToEncrypt = std::move(jsonToEncrypt).dump();

	auto &session = m_d->outboundGroupSessions.at(roomId);

	auto ciphertext = session.encrypt(std::move(textToEncrypt));

	return
	json{
	{"algorithm", CryptoConstants::megOlmAlgo},
	{"sender_key", curve25519IdentityKey()},
	{"ciphertext", ciphertext},
	{"session_id", session.sessionId()},
	};
	}

	std::size_t Crypto::rotateMegOlmSessionRandomSize()
	{
	return OutboundGroupSession::constructRandomSize();
	}

	std::string Crypto::rotateMegOlmSession(std::string roomId)
	{
	return rotateMegOlmSessionWithRandom(genRandomData(rotateMegOlmSessionRandomSize()), currentTimeMs(), roomId);
	}

	std::string Crypto::rotateMegOlmSessionWithRandom(RandomData random, Timestamp timeMs, std::string roomId)
	{
	m_d->reuseOrCreateOutboundGroupSession(
	random, timeMs,
	roomId, std::nullopt);
	return outboundGroupSessionCurrentKey(roomId);
	}

	std::optional<std::string> Crypto::rotateMegOlmSessionIfNeeded(std::string roomId, MegOlmSessionRotateDesc desc)
	{
	return rotateMegOlmSessionWithRandomIfNeeded(
	genRandomData(rotateMegOlmSessionRandomSize()), currentTimeMs(),
	roomId, desc);
	}

	std::optional<std::string> Crypto::rotateMegOlmSessionWithRandomIfNeeded(
	RandomData random, Timestamp timeMs,
	std::string roomId, MegOlmSessionRotateDesc desc)
	{
	auto oldSessionValid = m_d->reuseOrCreateOutboundGroupSession(random, timeMs, roomId, std::move(desc));
	return oldSessionValid ? std::nullopt : std::optional(outboundGroupSessionCurrentKey(roomId));
	}

	std::string Crypto::outboundGroupSessionInitialKey(std::string roomId)
	{
	auto &session = m_d->outboundGroupSessions.at(roomId);
	return session.initialSessionKey();
	}

	std::string Crypto::outboundGroupSessionCurrentKey(std::string roomId)
	{
	auto &session = m_d->outboundGroupSessions.at(roomId);
	return session.sessionKey();
	}

	auto Crypto::devicesMissingOutboundSessionKey(
	immer::map<std::string, immer::map<std::string /* deviceId */,
	std::string /* curve25519IdentityKey */>> keyMap) const -> UserIdToDeviceIdMap
	{
	auto ret = UserIdToDeviceIdMap{};
	for (auto [userId, devices] : keyMap) {
	auto unknownDevices =
	intoImmer(immer::flex_vector<std::string>{},
	zug::filter([=](auto kv) {
	auto [deviceId, theirCurve25519IdentityKey] = kv;
	return m_d->knownSessions.find(theirCurve25519IdentityKey)
	== m_d->knownSessions.end();
	})
	\| zug::map([=](auto kv) {
	auto [deviceId, key] = kv;
	return deviceId;
	}),
	devices);
	if (! unknownDevices.empty()) {
	ret = std::move(ret).set(userId, std::move(unknownDevices));
	}
	}
	return ret;
	}

	std::size_t Crypto::createOutboundSessionRandomSize()
	{
	return Session::constructOutboundRandomSize();
	}

	// TODO remove this
	void Crypto::createOutboundSession(std::string theirIdentityKey,
	std::string theirOneTimeKey)
	{
	createOutboundSessionWithRandom(
	genRandomData(createOutboundSessionRandomSize()),
	theirIdentityKey, theirOneTimeKey);
	}

	void Crypto::createOutboundSessionWithRandom(
	RandomData random,
	std::string theirIdentityKey,
	std::string theirOneTimeKey)
	{
	assert(random.size() >= createOutboundSessionRandomSize());
	auto session = Session(OutboundSessionTag{},
	RandomTag{},
	random,
	m_d->account,
	theirIdentityKey,
	theirOneTimeKey);

	if (session.valid()) {
	m_d->knownSessions.insert_or_assign(theirIdentityKey,
	std::move(session));
	}
	}

	nlohmann::json Crypto::toJson() const
	{
	std::string pickledData = m_d->pickle();
	auto j = nlohmann::json::object({
	{"account", std::move(pickledData)},
	{"uploadedOneTimeKeysCount", m_d->uploadedOneTimeKeysCount},
	{"numUnpublishedKeys", m_d->numUnpublishedKeys},
	{"knownSessions", nlohmann::json(m_d->knownSessions)},
	{"inboundGroupSessions", nlohmann::json(m_d->inboundGroupSessions)},
	{"outboundGroupSessions", nlohmann::json(m_d->outboundGroupSessions)},
	});

	return j;
	}

	void Crypto::loadJson(const nlohmann::json &j)
	{
	const auto &pickledData = j.at("account").template get<std::string>();
	m_d->unpickle(pickledData);
	m_d->uploadedOneTimeKeysCount = j.at("uploadedOneTimeKeysCount");
	m_d->numUnpublishedKeys = j.at("numUnpublishedKeys");
	m_d->knownSessions = j.at("knownSessions").template get<decltype(m_d->knownSessions)>();
	m_d->inboundGroupSessions = j.at("inboundGroupSessions").template get<decltype(m_d->inboundGroupSessions)>();
	m_d->outboundGroupSessions = j.at("outboundGroupSessions").template get<decltype(m_d->outboundGroupSessions)>();
	}
	}

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