https to http proxy using fiddlercore

[Kevin Radke]

I have been able to use fiddlercore to very easily construct an http proxy.  It works great for both http and https traffic.  I even have MITM decryption working and can see the actual https traffic decoded.  I'd now like to force all the https traffic to use http to the server.  I've tried to rewrite the connect port and/or URL in the BeforeRequest handler and it then connected to port 80 on the server, but is still trying to speak SSL.  How can I get it to not try and SSL handshake with the server?

Both these work:

  client -> http -> fiddler -> http -> server

  client -> https -> fiddler (mitm) -> https -> server

I want to do this:

client -> https -> fiddler (mitm) -> http -> server

I feel I'm missing something obvious, so any pointers would be appreciated.

Thanks!

Kevin R.

[EricLaw]

Step #1 would be to automatically reply to any HTTP CONNECT requests from the client without contacting the server. This will allow the client to believe that there's a HTTPS connection to the server. Step #2 would be to change the HTTPS requests you receive to use HTTP and pass those along to the server. I believe we concluded that the simplest way to do that is to use the BeforeRequest handler to change the Session's URL (changing the scheme, and if present, the port)

[Kevin Radke]

This seems to sorta work in the BeforeRequest handler:

if (oS.isHTTPS)

{

 oS.fullUrl = oS.fullUrl.Replace("https://", "http://").Replace("443", "80");

}

Two observed things:

1. A connection to the original port is opened to the server, but not handshaked - It is closed when the warning below happens
2. Warnings received in log: "Detaching server pipe. Had: HTTPS:server:443 but needs: server:80"

I assume there is some performance penalty in opening the original port and it also requires to original server to support both ports.

I originally tried the above when oS.HTTPMethodIs("CONNECT"), but didn't get it to work.  I may re-visit it again.

Kevin R.

[EricLaw]

Do this inside your OnBeforeRequest handler:

 

  // Handle CONNECT Tunnels

  if (oS.HTTPMethodIs("CONNECT"))

  {

    oS["x-replywithtunnel"] = "FakeTunnel";

    return;

  }

 

  // Handle HTTPS requests

  if (oS.isHTTPS)

  {

    oS.fullUrl = "http://" + oS.hostname + oS.PathAndQuery;

  }

 

[Kevin Radke]

Perfect!  I was just missing the FakeTunnel part.

Thanks!

Kevin R.

[syed khalid]

Hello Kevin,

Is this possible to achieve the same using Burp Suite proxy. I am using a linux machine and i can't switch to Fiddler. 

Syed