How to lock Firefox's proxy settings for proxy filters

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fishin4guitars
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Joined: Tue Feb 15, 2011 7:56 pm

How to lock Firefox's proxy settings for proxy filters

Post by fishin4guitars »

Maybe I'm the only one who doesn't know this, but here goes...

If you use a proxy filter (such as DansGuardian), and have users with a slightly above average technical ability, they can easily get around said filter by using Firefox's proxy settings. This fix remedies this hole.

1) In $HOME/.mozilla/firefox/(random characters).default/, create a file user.js
For example, in my case it's ~/.mozilla/firefox/3ga6boxk.default/
2) In ./user.js, place the text

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lockPref("network.proxy.http", "127.0.0.1");
lockPref("network.proxy.http_port", 8080);
lockPref("network.proxy.type", 1);
lockPref("network.proxy.share_proxy_settings", true);
Of course, you would replace 127.0.0.1 with your proxy's ip address, and 8080 with the port your filter uses.

3) run

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sudo chmod 644 ./user.js
sudo chown root ./user.js
sudo chgrp root ./user.js
This changes the permissions to -rw-r--r--, and the owner and owning group to root so that, in case of an even more technical user, they can't edit the file.
You could also put a universal user.js file in a convenient location not in the users home directory, and place a link called user.js in its place in the (random characters).default directory.

I use this on Firefox 4, but it should work with earlier versions as well.
32 bit Linux Mint 10 Gnome

Favorite Distro? Arch Linux

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