public void Test_OmemoMessage()
{
Random rand = new Random();
byte[] sessionKey = new byte[32];
rand.NextBytes(sessionKey);
IdentityKeyPairModel identityKey = KeyHelper.GenerateIdentityKeyPair();
SignedPreKeyModel signedPreKey = KeyHelper.GenerateSignedPreKey(0, identityKey.privKey);
OmemoSessionModel refOmemoSession = new OmemoSessionModel(new Bundle()
{
identityKey = identityKey.pubKey,
preKeys = KeyHelper.GeneratePreKeys(0, 10),
preKeySignature = signedPreKey.signature,
signedPreKey = signedPreKey.preKey.pubKey,
signedPreKeyId = signedPreKey.preKey.keyId
}, 0, KeyHelper.GenerateIdentityKeyPair())
{
ek = KeyHelper.GenerateKeyPair().pubKey
};
OmemoMessage refOmemoMessage = new OmemoMessage(refOmemoSession);
byte[] data = refOmemoMessage.ToByteArray();
Assert.IsTrue(data.Length > 0);
OmemoMessage omemoMessage = new OmemoMessage(data);
Assert.IsTrue(omemoMessage.Equals(refOmemoMessage));
}
/// <summary>
/// Decrypts the key and HMAC concatenation (<see cref="OmemoMessage.cipherText"/>) with the given <paramref name="mk"/> and returns the result.
/// </summary>
/// <param name="mk">The message key that should be used for decryption.</param>
/// <param name="msg">The <see cref="OmemoMessage"/> containing the key and HMAC concatenation (<see cref="OmemoMessage.cipherText"/>).</param>
/// <param name="msgHmac">The HMAC of the <paramref name="msg"/>.</param>
/// <param name="assData">Encode(IK_A) || Encode(IK_B) => Concatenation of Alices and Bobs public part of their identity key.</param>
/// <returns>key || HMAC</returns>
private byte[] DecryptKeyHmacForDevice(byte[] mk, OmemoMessage msg, byte[] msgHmac, byte[] assData)
{
// 32 byte (256 bit) of salt. Initialized with 0s.
byte[] hkdfOutput = CryptoUtils.HkdfSha256(mk, new byte[32], "OMEMO Message Key Material", 80);
CryptoUtils.SplitKey(hkdfOutput, out byte[] encKey, out byte[] authKey, out byte[] iv);
byte[] hmacInput = CryptoUtils.Concat(assData, msg.ToByteArray());
byte[] hmacResult = CryptoUtils.HmacSha256(authKey, hmacInput);
byte[] hmacTruncated = CryptoUtils.Truncate(hmacResult, 16);
// Debug trace output:
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(mk) + ": " + CryptoUtils.ToHexString(mk));
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(msgHmac) + ": " + CryptoUtils.ToHexString(msgHmac));
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(assData) + ": " + CryptoUtils.ToHexString(assData));
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(hkdfOutput) + ": " + CryptoUtils.ToHexString(hkdfOutput));
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(encKey) + ": " + CryptoUtils.ToHexString(encKey));
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(authKey) + ": " + CryptoUtils.ToHexString(authKey));
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(iv) + ": " + CryptoUtils.ToHexString(iv));
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(hmacInput) + ": " + CryptoUtils.ToHexString(hmacInput));
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(hmacResult) + ": " + CryptoUtils.ToHexString(hmacResult));
Logger.Trace("[" + nameof(DecryptKeyHmacForDevice) + "] " + nameof(hmacTruncated) + ": " + CryptoUtils.ToHexString(hmacTruncated));
if (!hmacTruncated.SequenceEqual(msgHmac))
{
throw new OmemoException("Failed to decrypt. HMAC of OmemoMessage does not match.");
}
return(CryptoUtils.Aes256CbcDecrypt(encKey, iv, msg.cipherText));
}
/// <summary>
/// Encrypts the given key and HMAC concatenation and returns the result.
/// </summary>
/// <param name="keyHmac">The key, HMAC concatenation result.</param>
/// <param name="session">The <see cref="OmemoSessionModel"/> between the sender and receiver.</param>
/// <param name="assData">Encode(IK_A) || Encode(IK_B) => Concatenation of Alices and Bobs public part of their identity key.</param>
private OmemoAuthenticatedMessage EncryptKeyHmacForDevices(byte[] keyHmac, OmemoSessionModel session, byte[] assData)
{
byte[] mk = LibSignalUtils.KDF_CK(session.ckS, 0x01);
session.ckS = LibSignalUtils.KDF_CK(session.ckS, 0x02);
OmemoMessage omemoMessage = new OmemoMessage(session);
++session.nS;
// 32 byte (256 bit) of salt. Initialized with 0s.
byte[] hkdfOutput = CryptoUtils.HkdfSha256(mk, new byte[32], "OMEMO Message Key Material", 80);
CryptoUtils.SplitKey(hkdfOutput, out byte[] encKey, out byte[] authKey, out byte[] iv);
omemoMessage.cipherText = CryptoUtils.Aes256CbcEncrypt(encKey, iv, keyHmac);
byte[] omemoMessageBytes = omemoMessage.ToByteArray();
byte[] hmacInput = CryptoUtils.Concat(assData, omemoMessageBytes);
byte[] hmacResult = CryptoUtils.HmacSha256(authKey, hmacInput);
byte[] hmacTruncated = CryptoUtils.Truncate(hmacResult, 16);
return(new OmemoAuthenticatedMessage(hmacTruncated, omemoMessageBytes));
}
/// <summary>
/// Encrypts the given key and HMAC concatenation and returns the result.
/// </summary>
/// <param name="keyHmac">The key, HMAC concatenation result.</param>
/// <param name="session">The <see cref="OmemoSessionModel"/> between the sender and receiver.</param>
/// <param name="assData">Encode(IK_A) || Encode(IK_B) => Concatenation of Alices and Bobs public part of their identity key.</param>
private OmemoAuthenticatedMessage EncryptKeyHmacForDevices(byte[] keyHmac, OmemoSessionModel session, byte[] assData)
{
byte[] mk = LibSignalUtils.KDF_CK(session.ckS, 0x01);
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(session.ckS) + ": " + CryptoUtils.ToHexString(session.ckS));
session.ckS = LibSignalUtils.KDF_CK(session.ckS, 0x02);
OmemoMessage omemoMessage = new OmemoMessage(session);
++session.nS;
// 32 byte (256 bit) of salt. Initialized with 0s.
byte[] hkdfOutput = CryptoUtils.HkdfSha256(mk, new byte[32], "OMEMO Message Key Material", 80);
CryptoUtils.SplitKey(hkdfOutput, out byte[] encKey, out byte[] authKey, out byte[] iv);
omemoMessage.cipherText = CryptoUtils.Aes256CbcEncrypt(encKey, iv, keyHmac);
byte[] omemoMessageBytes = omemoMessage.ToByteArray();
byte[] hmacInput = CryptoUtils.Concat(assData, omemoMessageBytes);
byte[] hmacResult = CryptoUtils.HmacSha256(authKey, hmacInput);
byte[] hmacTruncated = CryptoUtils.Truncate(hmacResult, 16);
// Update the session state:
if (session.state == SessionState.RECEIVED)
{
session.state = SessionState.READY;
}
// Debug trace output:
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(mk) + ": " + CryptoUtils.ToHexString(mk));
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(assData) + ": " + CryptoUtils.ToHexString(assData));
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(hkdfOutput) + ": " + CryptoUtils.ToHexString(hkdfOutput));
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(encKey) + ": " + CryptoUtils.ToHexString(encKey));
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(authKey) + ": " + CryptoUtils.ToHexString(authKey));
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(iv) + ": " + CryptoUtils.ToHexString(iv));
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(hmacInput) + ": " + CryptoUtils.ToHexString(hmacInput));
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(hmacResult) + ": " + CryptoUtils.ToHexString(hmacResult));
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(hmacTruncated) + ": " + CryptoUtils.ToHexString(hmacTruncated));
Logger.Trace("[" + nameof(EncryptKeyHmacForDevices) + "] " + nameof(session.state) + ": " + session.state);
return(new OmemoAuthenticatedMessage(hmacTruncated, omemoMessageBytes));
}