public static object readMessage(WebMessage message, RSACryptoServiceProvider sender_rsa)
{
//VUNERABILTY
//IN CASE OF client restart the fake server can resend the message, the token is still valid
//sol: on boot reset all client token
//this solve also reply attack as the message would all change token, so I need only 1 session message id
//if the message id buffer if full receiver shall send an authentication request along with the correct answer (to avoid answer to be to different from normal message)
if (message == null)
{
return(null);
}
byte[] signature = message.Signature;
RSACryptoServiceProvider my_rsa = message.getGlobalObject <IMyRsaProvider>().getMySra();
//checking unique id
byte[] message_id_bytes = my_rsa.Decrypt(message.MessageID, false);
if (!sender_rsa.VerifyData(message_id_bytes, new SHA1CryptoServiceProvider(), message.MessageIDSignaure))
{
return(null);
}
string message_id = message_id_bytes.getString();
if (message_ids.Contains(message_id))
{
return(null);
}
//replay attack!!!
if (message_ids.Count > replay_store_size)
{
message_ids = new HashSet <string>();
}
message_ids.Add(message_id);
byte[] Key = my_rsa.Decrypt(message.Key, false);
byte[] IV = my_rsa.Decrypt(message.IV, false);
//Create a new instance of the RijndaelManaged class
//and decrypt the stream.
RijndaelManaged RMCrypto = new RijndaelManaged();
//Create an instance of the CryptoStream class, pass it the NetworkStream, and decrypt
//it with the Rijndael class using the key and IV.
MemoryStream ms = new MemoryStream(message.Message);
CryptoStream CryptStream = new CryptoStream(ms, RMCrypto.CreateDecryptor(Key, IV), CryptoStreamMode.Read);
MemoryStream output = new MemoryStream();
byte[] buffer = new byte[1024];
int read = CryptStream.Read(buffer, 0, buffer.Length);
while (read > 0)
{
output.Write(buffer, 0, read);
read = CryptStream.Read(buffer, 0, buffer.Length);
}
CryptStream.Flush();
CryptStream.Dispose();
ms.Dispose();
byte[] received_message = output.ToArray();
if (!sender_rsa.VerifyData(received_message, new SHA1CryptoServiceProvider(), signature))
{
return(null);
}
//OK message verified and decrypted!
IFormatter formatter = new BinaryFormatter();
ms = new MemoryStream(received_message);
object message_object = formatter.Deserialize(ms);
ms.Dispose();
return(message_object);
}
