How to block access to https URLs by regex on OS X?

Question

Is there any way in which I can, on OS X, effectively block against access (by browsers or potentially any process) to secure URLs by regex?

E.g. deny access to: https://example.com/foo/bar/.*

but at the same time allow access to all other non-matching URLs under https://example.com/

I'm not looking for a solution which involves browser extensions, but that would work automatically for any browser and any fresh (extensionless) browser profile.

Thanks.

Answer 1

You can use a proxy auto-config (PAC) file to do this if all your applications honor system proxy settings. It is a JavaScript file declaring a single function FindProxyForURL(), which provides the web browser the proxy setting for a URL. You just need to return a non-working proxy setting to prevent a connection from happening.

var normal = "DIRECT", blackhole = "PROXY 127.0.0.1:3421";

function FindProxyForURL(url, host) {
    if(/^https:\/\/example.com\/foo\/bar\//i.test(url)) {
        return blackhole;
    }
    return normal;
}

You need to use a file URL to load the PAC file from the local hard drive. Enter this URL as the system proxy setting in the Network System Preferences panel.

This approach has been used before – see no-ads for an example of such a script that blocks many URLs.