How to write a reverse proxy using Titanium-Web-Proxy?

Question

I recently wrote a reverse proxy using Titanium-Web-Proxy.

The browser accesses the reverse proxy through IP 127.0.0.1, port 80, and the reverse proxy forwards the browser's request to the IIS server at IP 127.0.0.1, port 2366.

+---------+    Request    +---------------+                 +------------+
|         +-------------> |               |     Request     |            |
|         |               | Reverse Proxy +---------------> | Web Server |
|         |               |               |                 |            |
| Browser |               | 127.0.0.1     |                 | 127.0.0.1  |
|         |               |               |    Response     |            |
|         |    Response   | 80            | <---------------+ 2366       |
|         | <-------------+               |                 |            |
+---------+               +---------------+                 +------------+

When I tested it, the reverse proxy did not work as I expected, and the browser returned an HTTP 400 error.

Bad Request - Invalid Hostname

HTTP Error 400. The request hostname is invalid.

I tried rewriting 127.0.0.1:2366 as localhost:2366 and retesting, and the error was the same.

Later I tried to change modifiedUri to http://example.com but got a 404 Not Found error.

var modifiedUri = new UriBuilder("http://example.com/");

This is my code, please do not mind my poor coding level.

public class Startup
{
    private readonly ProxyServer proxyServer;

    private readonly IDictionary<Guid, HeaderCollection> requestHeaderHistory = new ConcurrentDictionary<Guid, HeaderCollection>();

    private readonly IDictionary<Guid, HeaderCollection> responseHeaderHistory = new ConcurrentDictionary<Guid, HeaderCollection>();

    public Startup()
    {
        proxyServer = new ProxyServer()
        {
            TrustRootCertificate = true,
            ForwardToUpstreamGateway = true,
        };
    }

    public void Start()
    {
        proxyServer.BeforeRequest += OnRequest;
        proxyServer.BeforeResponse += OnResponse;

        var transparentProxyEndPoint = new TransparentProxyEndPoint(IPAddress.Loopback, 80, false)
        {

        };

        proxyServer.AddEndPoint(transparentProxyEndPoint);
        proxyServer.Start();
    }

    public void Stop()
    {
        proxyServer.BeforeRequest -= OnRequest;
        proxyServer.BeforeResponse -= OnResponse;
        proxyServer.Stop();
    }

    public async Task OnRequest(object sender, SessionEventArgs e)
    {
        var requestUri = e.WebSession.Request.RequestUri;
        var modifiedUri = new UriBuilder("http", "127.0.0.1", 2366, requestUri.AbsolutePath);

        e.WebSession.Request.RequestUri = modifiedUri.Uri;

        requestHeaderHistory[e.Id] = e.WebSession.Request.RequestHeaders;

        if (e.WebSession.Request.HasBody)
        {
            var bodyBytes = await e.GetRequestBody();
            await e.SetRequestBody(bodyBytes);

            string bodyString = await e.GetRequestBodyAsString();
            await e.SetRequestBodyString(bodyString);
        }
    }

    public async Task OnResponse(object sender, SessionEventArgs e)
    {
        responseHeaderHistory[e.Id] = e.WebSession.Response.ResponseHeaders;

        if (e.WebSession.Request.Method == "GET" || e.WebSession.Request.Method == "POST")
        {
            if (e.WebSession.Response.ResponseStatusCode == (int)HttpStatusCode.OK)
            {
                if (e.WebSession.Response.ContentType != null && e.WebSession.Response.ContentType.Trim().ToLower().Contains("text/html"))
                {
                    var bodyBytes = await e.GetResponseBody();
                    await e.SetResponseBody(bodyBytes);

                    string body = await e.GetResponseBodyAsString();
                    await e.SetResponseBodyString(body);
                }
            }
        }
    }
}

Answer 1

Solved!

I need rewrite the request hostname.

See Titanium-Web-Proxy issues #344.