Connect to SOCKS proxy that requires authentication

Question

I'm using Fiddler Core in my project and have had success routing requests through a SOCKS proxy that does not require authentication.

oS["x-OverrideGateway"] = string.Format("socks={0}:{1}", ProxyHost, ProxyPort);

Now I'm trying to connect to a SOCKS proxy that requires authentication. I've tried adding the below, per this non-SOCKS guide: Authenticate With CBT .

oS["X-AutoAuth"] = Auth;

Where Auth is a string containing the credentials in the form username:password . But the connection always fails with a Bad Gateway exception. I've been successful connecting to the same SOCKS proxy using curl and following it's guidelines for an authenticated SOCKS proxy.

After X-AutoAuth didn't work I reflected some of the code and found that this authentication mechanism is not used for SOCKS.

Answer 1

Rather unfortunately, Fiddler (and FiddlerCore) does not support SOCKS5 as of yet.

You could, however, request this at https://fiddler.ideas.aha.io/ .

Answer 2

We faced a similar issue and created a NuGet library which helps you "transform" SOCKS v4 traffic to SOCKS v5, and we added authentication support as well.

This small example shows how can you hook up FiddlerCore and a SOCKS5 proxy with username and password:

var localEndpoint = new IPEndPoint(IPAddress.Loopback, 4321);
var remoteEndpoint = new IPEndPoint(IPAddress.Parse("remote proxy IP"), 8080);
ISocksRelayServer relay = new SocksRelayServer.SocksRelayServer(localEndpoint, remoteEndpoint)
{
    Username = "...",
    Password = "..."
};

// Debug to console
relay.OnLogMessage += (sender, s) => Console.WriteLine($"OnLogMessage: {s}");
relay.OnLocalConnect += (sender, endpoint) => Console.WriteLine($"OnLocalConnect: {endpoint}");
relay.OnRemoteConnect += (sender, endpoint) => Console.WriteLine($"OnRemoteConnect: {endpoint}");

// Start relay server
relay.Start();

// Start FiddlerCore
FiddlerApplication.Startup(...);

// Set upstream gateway before requests
FiddlerApplication.BeforeRequest += session =>
{
    session["x-OverrideGateway"] = relay.LocalEndPoint.ToString();
}