The way of building a simple http proxy

Question

I'm trying to build a simple http proxy , which does four really basic things:

Accepts connection from web-browser (using TcpClient/TcpListener).
Reads request from its stream.
Reads hostname and initiates connection with host.
Loads content from webpage and forwards it back to the client.

The troubles i met with:

Sometimes page wouldn't load at all.
Sometimes browser gives me an error 'The content has wrong encryption'(in firefox).
Seldom i can see content corruption(plain text instead of HTML).

What i've done:

HttpListener class that contains methods for listening for incoming requests and invoking event OnNewRequestReceived:

        public void Listen()
        {
            Listener.Start();

            while (true)
            {
                var client = Listener.AcceptTcpClient();

                Task.Run(() => StartReceivingData(client));      
            }

        }

        public void StartReceivingData(TcpClient client)
        {
            NetworkStream clientStream = client.GetStream();

            var buffer = new byte[16000];

            while (true)
            {
                try
                {
                    if (!clientStream.CanRead)
                        return;

                    //connection is closed
                    if (clientStream.Read(buffer).Equals(0))
                        return;

                    OnNewRequestReceived?.Invoke(this, new RequestReceivedEventArgs() { User = client, Request = buffer });
                } // when clientStream is disposed, exception is thrown.
                catch { return; }
            }
        }

HttpClient class which basically contains a method that subscribes to event described above:

 private void Listener_OnNewConnectionReceived(object sender, RequestReceivedEventArgs e)
        {
            string hostname = HttpQueryParser.GetHostName(e.Request);
            NetworkStream proxyClientStream = e.User.GetStream();

            try
            {
                if (firewall.CheckIfBlocked(hostname))
                {
                    //send error page
                    e.User.GetStream().Write(Encoding.ASCII.GetBytes("<html><body style=\"padding:0; margin:0;\"><img style=\"padding:0; margin:0; width:100%; height:100%;\" src=\"https://www.hostinger.co.id/tutorial/wp-content/uploads/sites/11/2017/08/what-is-403-forbidden-error-and-how-to-fix-it.jpg\"</body></html>"));
                    return;
                }

                var targetServer = new TcpClient(hostname, 80);

                NetworkStream targetServerStream = targetServer.GetStream();

                targetServerStream.Write(e.Request);

                var responseBuffer = new byte[32];

                for (int offsetCounter = 0; true; ++offsetCounter)
                {
                    var bytesRead = targetServerStream.Read(responseBuffer, 0, responseBuffer.Length);

                  //  Console.WriteLine($"Read {bytesRead} from {hostname}.");

                    if (bytesRead.Equals(0))
                        return;


                    proxyClientStream.Write(responseBuffer, 0, responseBuffer.Length);

                    if (offsetCounter.Equals(0))
                    {
                        var headers = Encoding.UTF8.GetString(responseBuffer).Split("\r\n");

                        logger.Log(new HttpRequestEntry()
                        {
                            ResponseCode = headers[0].Substring(headers[0].IndexOf(" ") + 1),
                            Hostname = hostname
                        });
                    }
                }

            }
            catch { return; }
            finally { proxyClientStream.Dispose(); }


        }

So, i'm guessing there's a problem with my buffer size, but changing it to higher values actually doesn't change anything .

Answer 1

Ok so i don't know what's the problem with my byte arrays was, but i made it work, using Stream.CopyTo , which i was quite surprized about - it works on two NetworkStreams. Here's working method if you are curious:

 private void Listener_OnNewConnectionReceived(object sender, RequestReceivedEventArgs e)
 {
            string hostname = HttpQueryParser.GetHostName(e.Request);
            NetworkStream proxyClientStream = e.User.GetStream();

            try
            {
                if (firewall.CheckIfBlocked(hostname))
                {
                    //send error page
                    e.User.GetStream().Write(Encoding.ASCII.GetBytes("<html><body style=\"padding:0; margin:0;\"><img style=\"padding:0; margin:0; width:100%; height:100%;\" src=\"https://www.hostinger.co.id/tutorial/wp-content/uploads/sites/11/2017/08/what-is-403-forbidden-error-and-how-to-fix-it.jpg\"</body></html>"));
                    return;
                }

                var targetServer = new TcpClient(hostname, 80);

                NetworkStream targetServerStream = targetServer.GetStream();

                targetServerStream.Write(e.Request);

                var responseBuffer = new byte[32];

                //this is to capture status of http request and log it.

                targetServerStream.Read(responseBuffer, 0, responseBuffer.Length);

                proxyClientStream.Write(responseBuffer, 0, responseBuffer.Length);

                var headers = Encoding.UTF8.GetString(responseBuffer).Split("\r\n");

                logger.Log(new HttpRequestEntry()
                {
                    ResponseCode = headers[0].Substring(headers[0].IndexOf(" ") + 1),
                    Hostname = hostname
                });

                targetServerStream.CopyTo(proxyClientStream);

            }
            catch { return; }
            finally { proxyClientStream.Dispose(); }


}

The way of building a simple http proxy

Question

1 answers

solution1
0 2019-03-28 20:44:36

The way of building a simple http proxy

Question

1 answers

solution1 0 2019-03-28 20:44:36

solution1
0 2019-03-28 20:44:36