Burp PAC Server

This Burp Extension generates a dynamic Proxy Auto-Configuration (PAC) script that will route traffic to your Burp proxy only if it matches the scope defined in your Burp target, e.g.:

function FindProxyForURL(url, host) {
	var proxy = 'PROXY localhost:8080; DIRECT';
    var simple_scope = [];
    var advanced_scope = [
        {"enabled":true,"host":"example.com","protocol":"any"},
        {"enabled":true,"host":"twitter.com","protocol":"any"}
    ];

    // since browsers do no longer allow PAC script to
    // inspect the path and query strings of HTTPS URLs,
    // this script does all its routing based on hostname alone
	for (s in simple_scope)
        // for simple scope, which works with prefixes
        // we need to strip of anything following the third /
        // and compare to the hostname
        if(simple_scope[s].startsWith('https:')) {
            if (simple_scope[s].length > 0 && url.indexOf(simple_scope[s].substring(0, simple_scope[s].indexOf('/', 8))) == 0)
			    return proxy;
        } else {
            // if http we can compare full urls still:
            if (simple_scope[s].length > 0 && url.indexOf(simple_scope[s]) == 0)
			    return proxy;
        }
		
	for (s in advanced_scope)
		if (advanced_scope[s].enabled && new RegExp(t[s].host).test(host))
			return proxy;
	return 'DIRECT';
}

To use the Burp PAC Server extension:

1. Download the JAR from releases in this repository;
2. In Burp Extender, browse to your downloaded file and add the JAR;
3. When the extension is loaded and enabled, the PAC server will spin up immediately, and the dynamic script is available on http://localhost:37314/proxy.pac
4. You can now configure your favorite browser plugin to point to this script, e.g.:
   • FoxyProxy:
     1. Go to FoxyProxy options;
     2. Add a new proxy;
     3. Select "Automatic proxy configuration URL";
     4. Enter the URL http://localhost:37314/proxy.pac
     5. Click View or Test to test the configuration
   • SwitchyOmega
     1. Go to SwitchyOmega options;
     2. Create a new profile;
     3. Select PAC profile
     4. Enter the URL http://localhost:37314/proxy.pac
     5. Note that in SwitchyOmega, you will need to manually refresh the PAC script every time you make changes to your scope in Burp.