proxypac

Proxy Auto Configuration Dynamic Generator Service

Background

Usually, Browsers let you set a proxy with the possibility to exclude destination hosts by a list or pattern. Sometimes this is not enough and you actually want the opposite: Only use proxy for specific destination hosts.

For this purpose, browsers provide a way to set a Automatic proxy configuration URL

Then you might want to provide a way to let users set the proxy to use themselves. For example, in my case, developers have their own servers with a squid installed. That way, development domains can all resolve to 127.0.0.1 and be the same for everybody.

You may also want to serve different destination domains for different groups of people

Features

This http-service is a dynamic generator of such proxy-auto-configuration featuring:

• set proxy (ip) via HTTP GET arg ?ip= -> (default proxy)
• set proxy (port) via HTTP GET arg ?port= -> (default 3128)
• set domain config via HTTP GET arg ?conf= (txt-file in config/)

How it works

The response generated by this service looks like this

function FindProxyForURL( url, host ) 
{

    var proxyserver = "${IP}:${PORT}";

    var proxylist = new Array(
        'example.org',
        'example.net',
    );

    for (var i = 0; i < proxylist.length; i++)
    {
        var value = proxylist[i];
        
        if (shExpMatch(host, value))
        {
            return "PROXY "+proxyserver;
        }
    }

    return "DIRECT";
}

The webserver used in front of this service is https://github.com/msoap/shell2http
it calls the script pac.sh that generates this response, while injecting the variables and the domain list (var proxylist) in a loop.

Environment variables

These variables can either be changed by building your own image or at container-start:

• CONFDIR (default = /config)
• PORT (for the webserver) (default = 8080)
• DEFAULTCONFIG (default = default -> ${CONFDIR}/default.txt)
• ROUTE (default /)

Quick Start

docker run --pull=always --name proxypac --rm -p 8080:8080 ghcr.io/sgohl/proxypac:main

or compose.yml

version: '3.7'
services:
  proxypac:
    image: ghcr.io/sgohl/proxypac:main
    environment:
      PORT: "8080"              ## optional/default
      ROUTE: "/"                ## optional/default
      DEFAULTCONFIG: "default"  ## optional/default
      CONFDIR: "/config"        ## if changed, you must mount your own host config folder or build your own image

test: http://localhost:8080/?ip=192.168.123.456

Fallback proxy via /etc/hosts

In case the user does not set the HTTP GET arg ?ip= the service responds per default with proxy

That way - if you prefer - you can set the IP of the proxy via /etc/hosts (or c:\windows\system32\drivers\etc\hosts)

192.168.123.456 proxy