private static async Task HandleForwarderAsync(TcpClientWrapper client, TcpClientWrapper forwarder, CancellationToken token)
{
while (!token.IsCancellationRequested && forwarder.IsConnected)
{
var data = await forwarder.Read();
if (data == null)
{
break;
}
// Write the raw bytes received from the forwarder to the client.
client.Write(data.RawBytes);
// Important Note:
// Attempting to use encoding to convert the data to a string will seemingly
// result in some data being lost as the proxy no longer function.
}
}
public async Task HandleClientAsync(TcpClientWrapper client, CancellationToken token)
{
var forwarder = new TcpClientWrapper();
while (!token.IsCancellationRequested && client.IsConnected)
{
var data = await client.Read();
if (data == null)
{
break;
}
// If the forwarder has a connection to a server
// forward the data from to the server.
if (forwarder.IsConnected)
{
forwarder.Write(data.RawBytes);
continue;
}
// If the forwarder is not connected, we are receiving headers.
// TODO: Ensure that all the header data has been received by constantly reading until encountering "\r\n\r\n" - the header terminator.
// TODO: This also means that the buffer size can be reduced etc.
// Otherwise, parse the headers from the client.
var headers = HttpHeader.Parse(data.ToString());
// Extract the remote address.
var hasHostField = headers.Fields.ContainsKey("Host");
var hostArray = hasHostField ? headers.Fields["Host"].Split(':')
: ParseUri(headers.RequestLine.Uri);
var host = hostArray[0];
var port = Convert.ToInt32(hostArray.Length == 1 ? "80" : hostArray[1]);
// Output the request received.
Console.WriteLine($"Received {headers.RequestLine.Method} request for {host}:{port}.");
// Try connect to the server.
var connectionResponse = await forwarder.Connect(host, port);
// If the forwarder fails to connect to the server.
// Send a bad gateway response and break out of the loop.
if (!connectionResponse.Success)
{
var exceptionMessage = connectionResponse.Message;
client.WriteHeaders("HTTP/1.1 502 Bad Gateway", $"Content-Length: {exceptionMessage.Length}", "Connection: close");
client.WriteLine(exceptionMessage);
break;
}
// If the method of the request is a connect request.
// Send a connection established response to the client.
if (headers.RequestLine.Method == "CONNECT")
{
client.WriteHeaders("HTTP/1.1 200 Connection Established");
// TODO: We may need to check if the port is 443 here. As it could be possible that the connection doesn't involve SSL.
if (_decryptHttpsTraffic)
{
await DecryptHttpsTrafficAsync(client, forwarder, host);
}
}
// Otherwise, forward the data sent by the client to the server.
else
{
forwarder.Write(data.RawBytes);
}
// Start handling the forwarder.
var task = HandleForwarderAsync(client, forwarder, token)
.ContinueWith(precursorTask => forwarder.Close(), token);
}
}
