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Improve error handling
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@TobiasFella
TobiasFella committed Mar 2, 2024
1 parent f9a1a79 commit ee319bc
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Showing 2 changed files with 53 additions and 15 deletions.
54 changes: 41 additions & 13 deletions Quotient/e2ee/sssshandler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24,39 +24,47 @@ DEFINE_SIMPLE_EVENT(CrossSigningUserSigningKey, Event, "m.cross_signing.user_sig
DEFINE_SIMPLE_EVENT(MegolmBackupKey, Event, "m.megolm_backup.v1", QJsonObject, encrypted, "encrypted")

template<EventClass EventType>
QByteArray SSSSHandler::decryptKey(const QByteArray& decryptionKey) const
QByteArray SSSSHandler::decryptKey(const QByteArray& decryptionKey)
{
Q_ASSERT(m_connection);
if (!m_connection->hasAccountData(SecretStorageDefaultKeyEvent::TypeId)) {
qCWarning(E2EE) << "No default secret storage key";
emit error(NoKeyError);
return {};
}
const auto defaultKey = m_connection->accountData<SecretStorageDefaultKeyEvent>()->key();
if (!m_connection->hasAccountData(EventType::TypeId)) {
qWarning() << "No account data for key" << EventType::TypeId;
emit error(NoKeyError);
return {};
}
const auto& encrypted = m_connection->accountData<EventType>()->encrypted().value(defaultKey).toObject();

auto hkdfResult = hkdfSha256(decryptionKey, QByteArray(32, u'\0'), EventType::TypeId.data());
if (!hkdfResult.has_value()) {
//TODO: Error
qCWarning(E2EE) << "Failed to calculate HKDF for" << EventType::TypeId;
emit error(DecryptionError);
}
const auto& keys = hkdfResult.value();

auto rawCipher = QByteArray::fromBase64(encrypted["ciphertext"_ls].toString().toLatin1());
auto result = hmacSha256(keys.mac(), rawCipher);
if (!result.has_value()) {
//TODO: Error
qCWarning(E2EE) << "Failed to calculate HMAC for" << EventType::TypeId;
emit error(DecryptionError);
}
if (QString::fromLatin1(result.value().toBase64()) != encrypted["mac"_ls].toString()) {
qCWarning(E2EE) << "MAC mismatch for" << EventType::TypeId;
emit error(DecryptionError);
return {};
}
auto decryptResult =
aesCtr256Decrypt(rawCipher, keys.aes(),
asCBytes<AesBlockSize>(QByteArray::fromBase64(
encrypted["iv"_ls].toString().toLatin1())));
if (!decryptResult.has_value()) {
//TODO: Error
qCWarning(E2EE) << "Failed to decrypt for" << EventType::TypeId;
emit error(DecryptionError);
}
auto key = QByteArray::fromBase64(decryptResult.value());
m_connection->database()->storeEncrypted(EventType::TypeId, key);
Expand Down Expand Up @@ -132,6 +140,7 @@ void SSSSHandler::loadMegolmBackup(const QByteArray& megolmDecryptionKey)
const auto& signature = authData["signatures"_ls].toObject()[m_connection->userId()].toObject()[key].toString();
if (!ed25519VerifySignature(edKey, authData, signature)) {
qCWarning(E2EE) << "Signature mismatch for" << edKey;
emit error(InvalidSignatureError);
return;
}
}
Expand All @@ -150,7 +159,8 @@ void SSSSHandler::loadMegolmBackup(const QByteArray& megolmDecryptionKey)
const auto &sessionData = session["session_data"_ls].toObject();
auto result = curve25519AesSha2Decrypt(sessionData["ciphertext"_ls].toString().toLatin1(), megolmDecryptionKey, sessionData["ephemeral"_ls].toString().toLatin1(), sessionData["mac"_ls].toString().toLatin1());
if (!result.has_value()) {
//TODO: Error
qCWarning(E2EE) << "Failed to decrypt session" << sessionId;
emit error(DecryptionError);
}
auto data = QJsonDocument::fromJson(result.value()).object();
m_connection->room(roomId)->addMegolmSessionFromBackup(sessionId.toLatin1(), data["session_key"_ls].toString().toLatin1(), session["first_message_index"_ls].toInt());
Expand All @@ -165,51 +175,64 @@ void SSSSHandler::calculateDefaultKey(const QByteArray& secret,
{
auto key = secret;
if (!m_connection->hasAccountData(SecretStorageDefaultKeyEvent::TypeId)) {
qCWarning(E2EE) << "No default secret storage key";
emit error(NoKeyError);
return;
}
const auto defaultKey = m_connection->accountData<SecretStorageDefaultKeyEvent>()->key();
if (!m_connection->hasAccountData("m.secret_storage.key."_ls + defaultKey)) {
qCWarning(E2EE) << "No account data for key" << ("m.secret_storage.key."_ls + defaultKey);
emit error(NoKeyError);
return;
}
const auto &keyEvent = m_connection->accountData("m.secret_storage.key."_ls + defaultKey);
if (keyEvent->contentPart<QString>("algorithm"_ls) != "m.secret_storage.v1.aes-hmac-sha2"_ls) {
qCWarning(E2EE) << "Unsupported SSSS key algorithm" << keyEvent->contentPart<QString>("algorithm"_ls) << " - aborting.";
emit error(UnsupportedAlgorithmError);
return;
}

if (requirePassphrase) {
const auto &passphraseJson = keyEvent->contentPart<QJsonObject>("passphrase"_ls);
if (passphraseJson["algorithm"_ls].toString() != "m.pbkdf2"_ls) {
qCWarning(E2EE) << "Unsupported SSSS passphrase algorithm" << passphraseJson["algorithm"_ls].toString() << " - aborting.";
emit error(UnsupportedAlgorithmError);
return;
}

auto result = pbkdf2HmacSha512(secret, passphraseJson["salt"_ls].toString().toLatin1(), passphraseJson["iterations"_ls].toInt(), 32);
if (result.has_value()) {
key = result.value();
} else {
//TODO: Error
if (!result.has_value()) {
qCWarning(E2EE) << "Failed to calculate pbkdf";
emit error(DecryptionError);
return;
}
key = result.value();
}

const auto &testKeys = hkdfSha256(key, QByteArray(32, u'\0'), {});
if (!testKeys.has_value()) {
//TODO: Error
qCWarning(E2EE) << "Failed to calculate hkdf";
emit error(DecryptionError);
return;
}
const auto& encrypted = aesCtr256Encrypt(
QByteArray(32, u'\0'), testKeys.value().aes(),
asCBytes<AesBlockSize>(QByteArray::fromBase64(
keyEvent->contentPart<QString>("iv"_ls).toLatin1())));
if (!encrypted.has_value()) {
//TODO: Error
qCWarning(E2EE) << "Failed to encrypt test keys";
emit error(DecryptionError);
return;
}
const auto &result = hmacSha256(testKeys.value().mac(), encrypted.value());
if (!result.has_value()) {
//TODO: Error
qCWarning(E2EE) << "Failed to calculate hmac";
emit error(DecryptionError);
return;
}
if (result.value() != QByteArray::fromBase64(keyEvent->contentPart<QString>("mac"_ls).toLatin1())) {
qCWarning(E2EE) << "MAC mismatch for secret storage key";
emit keyBackupKeyWrong();
emit error(WrongKeyError);
return;
}

Expand All @@ -222,6 +245,8 @@ void SSSSHandler::calculateDefaultKey(const QByteArray& secret,
decryptKey<CrossSigningUserSigningKey>(key);
decryptKey<CrossSigningMasterKey>(key);
if (megolmDecryptionKey.isEmpty()) {
qCWarning(E2EE) << "No megolm decryption key";
emit error(NoKeyError);
return;
}
loadMegolmBackup(megolmDecryptionKey);
Expand All @@ -238,14 +263,17 @@ void SSSSHandler::unlockSSSSFromSecurityKey(const QString& key)
}
if (parity != 0) {
qCWarning(E2EE) << "Invalid parity byte";
emit error(WrongKeyError);
return;
}
if (static_cast<uint8_t>(decoded[0]) != 0x8B || static_cast<uint8_t>(decoded[1]) != 0x01) {
qCWarning(E2EE) << "Invalid prefix";
emit error(WrongKeyError);
return;
}
if (decoded.length() != 32 + 3) {
qCWarning(E2EE) << "Incorrect length";
emit error(WrongKeyError);
return;
}
decoded = decoded.mid(2);
Expand Down
14 changes: 12 additions & 2 deletions Quotient/e2ee/sssshandler.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,16 @@ class QUOTIENT_API SSSSHandler : public QObject
Q_PROPERTY(Quotient::Connection* connection READ connection WRITE setConnection NOTIFY connectionChanged)

public:
enum Error
{
WrongKeyError,
NoKeyError,
DecryptionError,
InvalidSignatureError,
UnsupportedAlgorithmError,
};
Q_ENUM(Error);

using QObject::QObject;

//! \brief Unlock the secret backup from the given password
Expand All @@ -31,14 +41,14 @@ class QUOTIENT_API SSSSHandler : public QObject

Q_SIGNALS:
void keyBackupUnlocked();
void keyBackupKeyWrong();
void error(Error error);
void connectionChanged();

private:
QPointer<Quotient::Connection> m_connection;

//! \brief Decrypt the key with this name from the account data
template<Quotient::EventClass EventType> QByteArray decryptKey(const QByteArray& decryptionKey) const;
template<Quotient::EventClass EventType> QByteArray decryptKey(const QByteArray& decryptionKey);

void loadMegolmBackup(const QByteArray& megolmDecryptionKey);
void calculateDefaultKey(const QByteArray& secret, bool requirePassphrase);
Expand Down

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