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// SPDX-FileCopyrightText: 2024 Tobias Fella <tobias.fella@kde.org>
// SPDX-License-Identifier: LGPL-2.0-or-later
#include "keyimport.h"
#include <ranges>
#include <QtEndian>
#include <QDebug>
#include "e2ee/cryptoutils.h"
#include "connection.h"
#include "room.h"
#include "logging_categories_p.h"
using namespace Quotient;
using namespace Qt::Literals::StringLiterals;
const auto VersionLength = 1;
const auto SaltOffset = VersionLength;
const auto IvOffset = SaltOffset + AesBlockSize;
const auto RoundsOffset = IvOffset + AesBlockSize;
const auto RoundsLength = 4;
const auto PayloadOffset = RoundsOffset + RoundsLength;
const auto MacLength = 32;
const auto HeaderLength = VersionLength + AesBlockSize + AesBlockSize + RoundsLength + MacLength;
Expected<QJsonArray, KeyImport::Error> KeyImport::decrypt(QString data, const QString& passphrase)
{
data.remove("-----BEGIN MEGOLM SESSION DATA-----"_L1);
data.remove("-----END MEGOLM SESSION DATA-----"_L1);
data.remove(u'\n');
auto decoded = QByteArray::fromBase64(data.toLatin1());
if (decoded[0] != 1) {
qCWarning(E2EE) << "Wrong version byte";
return InvalidData;
}
if (decoded.size() < HeaderLength) {
qCWarning(E2EE) << "Data not long enough";
return InvalidData;
}
const auto salt = decoded.mid(SaltOffset, AesBlockSize);
const auto iv = decoded.mid(IvOffset, AesBlockSize);
const auto rounds = qFromBigEndian<uint32_t>(decoded.mid(RoundsOffset, RoundsLength).data());
const auto payload = decoded.mid(PayloadOffset, decoded.size() - HeaderLength);
const auto expectedMac = decoded.right(MacLength);
auto keys = pbkdf2HmacSha512<64>(passphrase.toLatin1(), salt, rounds);
if (!keys.has_value()) {
qCWarning(E2EE) << "Failed to calculate pbkdf:" << keys.error();
return OtherError;
}
auto actualMac = hmacSha256(key_view_t(keys.value().begin() + 32, 32), decoded.left(decoded.size() - MacLength));
if (!actualMac.has_value()) {
qCWarning(E2EE) << "Failed to calculate hmac:" << actualMac.error();
return OtherError;
}
if (actualMac.value() != expectedMac) {
qCWarning(E2EE) << "Mac incorrect";
return InvalidPassphrase;
}
auto plain = aesCtr256Decrypt(payload, byte_view_t<Aes256KeySize>(keys.value().begin(), Aes256KeySize), asCBytes<AesBlockSize>(iv));
if (!plain.has_value()) {
qCWarning(E2EE) << "Failed to decrypt data";
return OtherError;
}
return QJsonDocument::fromJson(plain.value()).array();
}
KeyImport::Error KeyImport::importKeys(QString data, const QString& passphrase, const Connection* connection)
{
auto result = decrypt(std::move(data), passphrase);
if (!result.has_value()) {
return result.error();
}
for (const auto& key : result.value()) {
const auto& keyObject = key.toObject();
const auto& room = connection->room(keyObject[RoomIdKey].toString());
if (!room) {
continue;
}
// We don't know the session index for these sessions here. We just pretend it's 0, it's not terribly important.
room->addMegolmSessionFromBackup(
keyObject["session_id"_L1].toString().toLatin1(),
keyObject["session_key"_L1].toString().toLatin1(), 0,
keyObject[SenderKeyKey].toVariant().toByteArray(),
keyObject["sender_claimed_keys"_L1]["ed25519"_L1].toString().toLatin1()
);
}
return Success;
}
inline QByteArray lineWrapped(QByteArray text, int wrapAt)
{
#if defined(__cpp_lib_ranges_chunk) && defined(__cpp_lib_ranges_join_with) \
&& defined(__cpp_lib_ranges_to_container)
using namespace std::ranges;
return views::chunk(std::move(text), wrapAt) | views::join_with('\n') | to<QByteArray>();
#else // Xcode 15 and older; libc++ 17 and older
for (auto i = wrapAt; i < text.size(); i += wrapAt) {
text.insert(i, '\n');
i++;
}
return text;
#endif
}
Quotient::Expected<QByteArray, KeyImport::Error> KeyImport::encrypt(QJsonArray sessions, const QString& passphrase)
{
auto plainText = QJsonDocument(sessions).toJson(QJsonDocument::Compact);
auto salt = getRandom<AesBlockSize>();
auto iv = getRandom<AesBlockSize>();
quint32 rounds = 200'000; // spec: "N should be at least 100,000";
auto keys = pbkdf2HmacSha512<64>(passphrase.toLatin1(), salt.viewAsByteArray(), rounds);
if (!keys.has_value()) {
qCWarning(E2EE) << "Failed to calculate pbkdf:" << keys.error();
return OtherError;
}
auto result = aesCtr256Encrypt(plainText, byte_view_t<Aes256KeySize>(keys.value().begin(), Aes256KeySize), asCBytes<AesBlockSize>(iv.viewAsByteArray()));
if (!result.has_value()) {
qCWarning(E2EE) << "Failed to encrypt export" << result.error();
return OtherError;
}
QByteArray data;
data.append("\x01");
data.append(salt.viewAsByteArray());
data.append(iv.viewAsByteArray());
QByteArray roundsData(4, u'\x0');
qToBigEndian<quint32>(rounds, roundsData.data());
data.append(roundsData);
data.append(result.value());
auto mac = hmacSha256(key_view_t(keys.value().begin() + 32, 32), data);
if (!mac.has_value()) {
qCWarning(E2EE) << "Failed to calculate MAC" << mac.error();
return OtherError;
}
data.append(mac.value());
// TODO: use std::ranges::to() once it's available from all stdlibs Quotient builds with
return "-----BEGIN MEGOLM SESSION DATA-----\n"_ba % lineWrapped(data.toBase64(), 96)
% "\n-----END MEGOLM SESSION DATA-----\n"_ba;
}
Quotient::Expected<QByteArray, KeyImport::Error> KeyImport::exportKeys(const QString& passphrase, const Connection* connection)
{
QJsonArray sessions;
for (const auto& room : connection->allRooms()) {
for (const auto &session : room->exportMegolmSessions()) {
sessions += session;
}
}
return encrypt(sessions, passphrase);
}
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