public Packet ChannelDecrypt(ICipherSetRemoteInfo channelInfo, Packet outer)
{
// We gotta have the primary components and something to decrypt
if (outer.Body.Length < 25)
{
return(null);
}
var ci = (CS1ARemoteInfo)channelInfo;
// Rip apart our packet
byte[] token = outer.Body.Take(16).ToArray();
byte[] iv = outer.Body.Skip(16).Take(4).ToArray();
byte[] encryptedData = outer.Body.Skip(20).Take(outer.Body.Length - 24).ToArray();
byte[] dataMac = outer.Body.Skip(outer.Body.Length - 4).Take(4).ToArray();
// Make sure we're on the right channel
if (!token.SequenceEqual(ci.Token))
{
return(null);
}
// Validate us some hmac
byte[] hmacKey = new byte[20];
Buffer.BlockCopy(ci.DecryptionKey, 0, hmacKey, 0, 16);
Buffer.BlockCopy(iv, 0, hmacKey, 16, 4);
var hmac = new HMac(new Sha256Digest());
hmac.Init(new KeyParameter(hmacKey));
hmac.BlockUpdate(encryptedData, 0, encryptedData.Length);
byte[] mac = new byte[hmac.GetMacSize()];
hmac.DoFinal(mac, 0);
var foldedMac = Helpers.Fold(mac, 3);
if (!foldedMac.SequenceEqual(dataMac))
{
// Get out of here with your bad data
return(null);
}
// Everything seems ok. Get it decrypted
byte[] aesIV = new byte[16];
Buffer.BlockCopy(iv, 0, aesIV, 0, 4);
Array.Clear(aesIV, 4, 12);
var cipher = new SicBlockCipher(new AesFastEngine());
var parameters = new ParametersWithIV(new KeyParameter(ci.DecryptionKey), aesIV);
cipher.Init(false, parameters);
var decryptedData = new byte[encryptedData.Length];
BufferedBlockCipher bufferCipher = new BufferedBlockCipher(cipher);
var offset = bufferCipher.ProcessBytes(encryptedData, decryptedData, 0);
bufferCipher.DoFinal(decryptedData, offset);
// Build a packet and ship it off
return(Packet.DecodePacket(decryptedData));
}
public Packet MessageDecrypt(Packet outer)
{
byte[] remoteKeyData = outer.Body.Take(21).ToArray();
byte[] ivData = outer.Body.Skip(21).Take(4).ToArray();
byte[] innerEncryptedData = outer.Body.Skip(25).Take(outer.Body.Length - 29).ToArray();
// Decode the body
ECKeyPair remoteEphemeralKeys = ECKeyPair.LoadKeys(SecNamedCurves.GetByName("secp160r1"), remoteKeyData, null);
var idAgreement = ECDHAgree(remoteEphemeralKeys.PublicKey, Key.PrivateKey);
var agreedHash = Helpers.SHA256Hash(Helpers.ToByteArray(idAgreement, 20));
var aesKey = Helpers.FoldOnce(agreedHash);
// Pad out the IV
byte[] aesIV = new byte[16];
Array.Clear(aesIV, 0, 16);
Buffer.BlockCopy(ivData, 0, aesIV, 0, 4);
// Decrypt it
var cipher = new BufferedBlockCipher(new SicBlockCipher(new AesFastEngine()));
var parameters = new ParametersWithIV(new KeyParameter(aesKey), aesIV);
cipher.Init(false, parameters);
byte[] decryptedBody = new byte[innerEncryptedData.Length];
var offset = cipher.ProcessBytes(innerEncryptedData, decryptedBody, 0);
cipher.DoFinal(decryptedBody, offset);
Packet outPacket = Packet.DecodePacket(decryptedBody);
return(outPacket);
}
/// <summary>
/// Decloak the given buffer and return the valid Packet from it
/// </summary>
/// <param name="buffer">A cloaked packet buffer.</param>
static public Packet Decloak(byte[] buffer)
{
if (buffer.Length < 8 || buffer [0] == 0)
{
return(Packet.DecodePacket(buffer));
}
byte[] nonce = buffer.Take(8).ToArray();
var parms = new ParametersWithIV(new KeyParameter(cloakKey), nonce);
var chacha = new ChaChaEngine(20);
chacha.Init(false, parms);
byte[] outBuff = new byte[buffer.Length - 8];
chacha.ProcessBytes(buffer, 8, buffer.Length - 8, outBuff, 0);
return(Decloak(outBuff));
}