Crypto Stream bad usage

Question

I'm trying to implement encryption on my client - server application, but since I implemented it I can't communicate between the applications.

Server:

private void CommsHandler(object client)
    {

        TcpClient tcpClient = (TcpClient)client;

        StreamWriter writer;
        StreamReader reader;
        using (RijndaelManaged myRijindel = new RijndaelManaged())
        {
            myRijindel.GenerateKey();
            myRijindel.GenerateIV();
            ICryptoTransform encryptor = myRijindel.CreateEncryptor(myRijindel.Key, myRijindel.IV);

            byte[] Key = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,  
                0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16};
            byte[] IV = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,  
               0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16};  

            CryptoStream secureStreamRead = new CryptoStream(tcpClient.GetStream(), myRijindel.CreateDecryptor(Key,IV), CryptoStreamMode.Read);
            CryptoStream secureStreamWrite = new CryptoStream(tcpClient.GetStream(), myRijindel.CreateEncryptor(Key, IV), CryptoStreamMode.Write);

            reader = new StreamReader(secureStreamRead);
            writer = new StreamWriter(secureStreamWrite);
        }

        NetworkStream network = tcpClient.GetStream();


        char[] buffer = new char[4096];

        while (true)
        {
            try
            {
                reader.Read(buffer, 0, buffer.Length);
            }
            catch (Exception)
            {
                InsertLog(2, "Communication with client closed");
                break;
            }
            string message = new string(buffer);
            Debug.Write(message);

            doJob(message, writer, network);

            for (int i = 0; i < buffer.Length; i++)
            {
                buffer[i] = (char)0;
            }
        }

        tcpClient.Close();
    }

Client:

private void button1_Click(object sender, EventArgs e)
{
    try
    {
        client.Connect(textBox1.Text, Convert.ToInt16(textBox2.Text));


        using (RijndaelManaged myRijindel = new RijndaelManaged())
        {
            myRijindel.GenerateKey();
            myRijindel.GenerateIV();
            ICryptoTransform encryptor = myRijindel.CreateEncryptor(myRijindel.Key, myRijindel.IV);

            byte[] Key = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,  
                0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16};
            byte[] IV = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,  
                0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16};

            CryptoStream secureStreamRead = new CryptoStream(client.GetStream(), myRijindel.CreateDecryptor(Key, IV), CryptoStreamMode.Read);
            CryptoStream secureStreamWrite = new CryptoStream(client.GetStream(), myRijindel.CreateEncryptor(Key, IV), CryptoStreamMode.Write);

            reader = new StreamReader(secureStreamRead);
            writer = new StreamWriter(secureStreamWrite);
        }

        network = client.GetStream();
        connected = true;
        MessageBox.Show("Connected successfully", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information);
    }
    catch (Exception ex)
    {
        MessageBox.Show("Could not connect to server:" + Environment.NewLine + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
    }
}

Is there anything wrong with my implementation? Especially on the StreamWriter and StreamReader parts. Or is the problem elsewhere?

What's the error? What's the symptom? You cannot debug something by just staring at the code. — usr, Feb 06 '13 at 19:43

score 2 · Answer 1 · answered Feb 06 '13 at 19:37

A using block always calls IDisposable.Dispose() at the end of the block.

So if you say:

using (RijndaelManaged myRijindel = new RijndaelManaged())
{
    ...
}

Your crypto-provider is closed once you end the block. I would imagine that is part of your problem.

Crypto Stream bad usage

1 Answers1