Greasemonkey userscript that removes SSL from Cloudfront hosted assets in GitHub

github_cloudfront_disable_ssl.user.js

/*
# README

This userscript is a hack to replace HTTPS Cloudfront hosted assets on GitHub.

Cloudfront serves its files *only* through 128-bit RC4/MD5 encryption, which is
old and not appropriate for secure use in the modern day, and as such I have
that disabled in Firefox (about:config security.ssl3.rsa_rc4_128_md5).

Since there is currently no way to whitelist encryption schemes for specific
websites, this userscript is a workaround that converts the CSS, Javascript and
images links used on github to plain http connection for the Cloudfront assets
server.

*/

// ==UserScript==
// @name           Github Cloudfront Disable SSL
// @namespace      https://gist.github.com/lkraider
// @description    Removes SSL from Cloudfront hosted assets
// @version        1.0.0
// @author         lkraider
// @include        https://github.com/*
// @include        https://*.github.com/*
// ==/UserScript==

var head = document.getElementsByTagName('head')[0];
var link = head.getElementsByTagName('link');
var script = head.getElementsByTagName('script');

var body = document.getElementsByTagName('body')[0];
var img = body.getElementsByTagName('img');

var https_cloudfront = "https://d3nwyuy0nl342s.cloudfront.net";
var cloudfront = https_cloudfront.replace("https://", "http://");

// GitHub pages contain `assetHost` variable that already points to correct
// server which is useful in case the host changes so the script doesn't need
// to be updated manually. Gist pages don't seem to define this though.
if (unsafeWindow.GitHub.assetHost) {
    https_cloudfront = unsafeWindow.GitHub.assetHost;
    cloudfront = https_cloudfront.replace("https://", "http://");
    unsafeWindow.GitHub.assetHost = cloudfront;
}

for (var i in link) {
    link[i].href = link[i].href.replace(https_cloudfront, cloudfront);
}

var new_script = [];
for (var i in script) {
    var old_src = script[i].src;
    if (old_src) {
        var new_src = old_src.replace(https_cloudfront, cloudfront);
        script[i].src = new_src;
        if (old_src != new_src) {
            var el = document.createElement('script');
            el.type = 'text/javascript';
            el.src = new_src;
            new_script.push(el);
        }
    }
}
for (var i in new_script) {
    head.appendChild(new_script[i]);
}

for (var i in img) {
    img[i].src = img[i].src.replace(https_cloudfront, cloudfront);
}