private static void OnConnected()
{
if (diffieHellman != null)
{
diffieHellman.Dispose();
}
diffieHellman = new ECDiffieHellmanCng();
byte[] servicePublicPart = diffieHellman.PublicKey.ToByteArray();
using (MemoryStream sendStream = new MemoryStream(servicePublicPart.Length + 2))
{
using (BinaryWriter writer = new BinaryWriter(sendStream))
{
writer.Write((ushort)servicePublicPart.Length);
writer.Write(servicePublicPart);
}
connection.SendObject <byte[]>("Handshake", sendStream.GetBuffer());
connection.AppendIncomingPacketHandler <byte[]>("HandshakeResponse", (header, connection, bytes) =>
{
connection.RemoveIncomingPacketHandler("HandshakeResponse");
using (MemoryStream receiveStream = new MemoryStream(bytes))
{
using (BinaryReader reader = new BinaryReader(receiveStream))
{
ushort saltLength = reader.ReadUInt16();
byte[] salt = reader.ReadBytes(saltLength);
ushort keyBlobLength = reader.ReadUInt16();
byte[] keyBlob = reader.ReadBytes(keyBlobLength);
ushort signatureLength = reader.ReadUInt16();
byte[] signature = reader.ReadBytes(signatureLength);
using (RSACryptoServiceProvider csp = new RSACryptoServiceProvider())
{
try
{
StringReader stringReader = new StringReader(Properties.Resources.publickey);
XmlSerializer serializer = new XmlSerializer(typeof(RSAParameters));
RSAParameters rsaParams = (RSAParameters)serializer.Deserialize(stringReader);
csp.ImportParameters(rsaParams);
if (!csp.VerifyData(keyBlob, new SHA512CryptoServiceProvider(), signature))
{
//Something is wrong here. The public blob does not match the signature. Possible MITM.
connection.CloseConnection(true);
connection = null;
}
else
{
//Connection was fine. Key exchange worked. Let's set the encryption up!
byte[] sharedMaterial = diffieHellman.DeriveKeyMaterial(CngKey.Import(keyBlob, CngKeyBlobFormat.EccPublicBlob));
using (Rfc2898DeriveBytes keyDerive = new Rfc2898DeriveBytes(sharedMaterial, salt, 1000))
{
encryptionKey = keyDerive.GetBytes(32); // 32 bytes = 256 bits, for AES encryption. Salt is generated per message
}
SetupMessageHandlers();
}
}
finally
{
csp.PersistKeyInCsp = false;
if (diffieHellman != null)
{
diffieHellman.Dispose();
diffieHellman = null;
}
}
}
}
}
});
}
}