//--------------------------------------------------------Misc Methods:---------------------------------------------------------------\\
#region --Misc Methods (Public)--
/// <summary>
/// Encrypts the content of MESSAGE with the given SessionCipher and saves the result in BASE_64_PAYLOAD.
/// </summary>
/// <param name="omemoSession">A storage object containing all SessionCipher for the target OMEMO devices.</param>
/// <param name="sourceDeviceId">The sender OMEMO device id.</param>
public void encrypt(OmemoSession omemoSession, uint sourceDeviceId)
{
SOURCE_DEVICE_ID = sourceDeviceId;
// 1. Generate a new AES-128 GCM key/iv:
Aes128Gcm aes128Gcm = new Aes128Gcm();
aes128Gcm.generateKey();
aes128Gcm.generateIv();
// 2. Encrypt the message using the Aes128Gcm instance:
byte[] encryptedData = aes128Gcm.encrypt(Encoding.Unicode.GetBytes(MESSAGE));
BASE_64_PAYLOAD = Convert.ToBase64String(encryptedData);
BASE_64_IV = Convert.ToBase64String(aes128Gcm.iv);
// 3. Concatenate key and authentication tag:
byte[] keyAuthTag = new byte[aes128Gcm.authTag.Length + aes128Gcm.key.Length];
Buffer.BlockCopy(aes128Gcm.key, 0, keyAuthTag, 0, aes128Gcm.key.Length);
Buffer.BlockCopy(aes128Gcm.authTag, 0, keyAuthTag, aes128Gcm.key.Length, aes128Gcm.authTag.Length);
// 4. Encrypt the key/authTag pair with libsignal for each deviceId:
KEYS = new List <OmemoKey>();
CiphertextMessage ciphertextMessage;
foreach (KeyValuePair <uint, SessionCipher> pair in omemoSession.DEVICE_SESSIONS)
{
ciphertextMessage = pair.Value.encrypt(keyAuthTag);
// Create a new OmemoKey object with the target device id, whether it's the first time the session got established and the encrypted key:
OmemoKey key = new OmemoKey(pair.Key, ciphertextMessage is PreKeySignalMessage, Convert.ToBase64String(ciphertextMessage.serialize()));
KEYS.Add(key);
}
ENCRYPTED = true;
}
private void encryptForDevices(Dictionary <uint, SessionCipher> devices, byte[] keyAuthTag)
{
CiphertextMessage ciphertextMessage;
foreach (KeyValuePair <uint, SessionCipher> pair in devices)
{
Logger.Debug("[OmemoMessageMessage]: Encrypting for deviceId: " + pair.Key);
ciphertextMessage = pair.Value.encrypt(keyAuthTag);
// Create a new OmemoKey object with the target device id, whether it's the first time the session got established and the encrypted key:
OmemoKey key = new OmemoKey(pair.Key, ciphertextMessage is PreKeySignalMessage, Convert.ToBase64String(ciphertextMessage.serialize()));
KEYS.Add(key);
}
}
/// <summary>
/// Decrypts the content of BASE_64_PAYLOAD with the given SessionCipher and saves the result in MESSAGE.
/// Sets ENCRYPTED to false.
/// </summary>
/// <param name="cipher">The SessionCipher for decrypting the content of BASE_64_PAYLOAD.</param>
/// <param name="remoteAddress">The SignalProtocolAddress of the sender.</param>
/// <param name="localeDeciceId">The local device id.</param>
/// <param name="helper">The current OmemoHelper object of the current account. If null, won't remove used PreKey.</param>
/// <returns>True on success.</returns>
public async Task <bool> decryptAsync(SessionCipher cipher, SignalProtocolAddress remoteAddress, uint localeDeciceId, OmemoHelper helper)
{
try
{
// 1. Check if the message contains a key for the local device:
OmemoKey key = getOmemoKey(localeDeciceId);
if (key is null)
{
Logger.Info("Discarded received OMEMO message - doesn't contain device id!");
return(false);
}
// 2. Load the cipher:
SignalProtocolAddress address = new SignalProtocolAddress(Utils.getBareJidFromFullJid(FROM), SOURCE_DEVICE_ID);
byte[] encryptedKeyAuthTag = Convert.FromBase64String(key.BASE_64_KEY);
byte[] decryptedKeyAuthTag = null;
if (key.IS_PRE_KEY)
{
PreKeySignalMessage preKeySignalMessage = new PreKeySignalMessage(encryptedKeyAuthTag);
decryptedKeyAuthTag = cipher.decrypt(preKeySignalMessage);
if (!(helper is null))
{
May <uint> preKey = preKeySignalMessage.getPreKeyId();
if (preKey.HasValue)
{
Logger.Info("Removing used PreKey.");
await helper.removePreKeyAndRepublishAsync(preKey.ForceGetValue());
}
else
{
Logger.Error("Failed to get value from PreKeySignalMessage.");
}
}
}
else
{
decryptedKeyAuthTag = cipher.decrypt(new SignalMessage(encryptedKeyAuthTag));
}
// 3. Check if the cipher got loaded successfully:
if (decryptedKeyAuthTag is null)
{
Logger.Info("Discarded received OMEMO message - failed to decrypt keyAuthTag is null!");
return(false);
}
// 4. Decrypt the payload:
byte[] aesIv = Convert.FromBase64String(BASE_64_IV);
byte[] aesKey = new byte[16];
byte[] aesAuthTag = new byte[decryptedKeyAuthTag.Length - aesKey.Length];
Buffer.BlockCopy(decryptedKeyAuthTag, 0, aesKey, 0, aesKey.Length);
Buffer.BlockCopy(decryptedKeyAuthTag, aesKey.Length, aesAuthTag, 0, aesAuthTag.Length);
Aes128GcmCpp aes128Gcm = new Aes128GcmCpp()
{
key = aesKey,
authTag = aesAuthTag,
iv = aesIv
};
byte[] encryptedData = Convert.FromBase64String(BASE_64_PAYLOAD);
byte[] decryptedData = aes128Gcm.decrypt(encryptedData);
// 5. Convert decrypted data to Unicode string:
MESSAGE = Encoding.UTF8.GetString(decryptedData);
ENCRYPTED = false;
return(true);
}
catch (Exception e)
{
Logger.Info("Discarded received OMEMO message - failed to decrypt with: " + e.Message);
}
return(false);
}
/// <summary>
/// Decrypts the content of BASE_64_PAYLOAD with the given SessionCipher and saves the result in MESSAGE.
/// Sets ENCRYPTED to false.
/// </summary>
/// <param name="cipher">The SessionCipher for decrypting the content of BASE_64_PAYLOAD.</param>
public bool decrypt(OmemoHelper omemoHelper, uint localOmemoDeviceId)
{
try
{
// 1. Check if the message contains a key for the local device:
OmemoKey key = getOmemoKey(localOmemoDeviceId);
if (key == null)
{
Logger.Info("Discarded received OMEMO message - doesn't contain device id!");
return(false);
}
// 2. Load the cipher:
SignalProtocolAddress address = new SignalProtocolAddress(Utils.getBareJidFromFullJid(FROM), SOURCE_DEVICE_ID);
SessionCipher cipher = omemoHelper.loadCipher(address);
byte[] encryptedKeyAuthTag = Convert.FromBase64String(key.BASE_64_KEY);
byte[] decryptedKeyAuthTag = null;
if (key.IS_PRE_KEY)
{
decryptedKeyAuthTag = cipher.decrypt(new PreKeySignalMessage(encryptedKeyAuthTag));
// ToDo republish the bundle info and remove used pre key
}
else
{
decryptedKeyAuthTag = cipher.decrypt(new SignalMessage(encryptedKeyAuthTag));
}
// 3. Check if the cipher got loaded successfully:
if (decryptedKeyAuthTag == null)
{
Logger.Info("Discarded received OMEMO message - failed to decrypt keyAuthTag is null!");
return(false);
}
// 4. Decrypt the payload:
byte[] aesIv = Convert.FromBase64String(BASE_64_IV);
byte[] aesKey = new byte[16];
byte[] aesAuthTag = new byte[decryptedKeyAuthTag.Length - aesKey.Length];
Buffer.BlockCopy(decryptedKeyAuthTag, 0, aesKey, 0, aesKey.Length);
Buffer.BlockCopy(decryptedKeyAuthTag, aesKey.Length, aesAuthTag, 0, aesAuthTag.Length);
Aes128Gcm aes = new Aes128Gcm()
{
key = aesKey,
authTag = aesAuthTag,
iv = aesIv
};
byte[] encryptedData = Convert.FromBase64String(BASE_64_PAYLOAD);
byte[] decryptedData = aes.decrypt(encryptedData);
// 5. Convert decrypted data to Unicode string:
MESSAGE = Encoding.Unicode.GetString(decryptedData);
ENCRYPTED = false;
return(true);
}
catch (Exception e)
{
Logger.Info("Discarded received OMEMO message - failed to decrypt with:" + e.Message);
}
return(false);
}