Configuring Firefox proxy settings via GPO

Step 1 - Making a GPO to install Firefox

1. Download a Firefox MSI package from http://www.frontmotion.com/news/firefox/releases/

2. Place the MSI in a shared folder on the domain controller or some other location available to all target computers. e.g C:\shared.

3. Rename the MSI so that the filename has only one period character. E.g firefox47.msi

The GPO deployment will fail with a 1612 error in the event log if the target computers do not have at least read permissions for this folder.

The GPO deployment will fail with a 1274 error in the event log if the filename has more than one period character.

4. Create the GPO in the OU that you want to deploy this GPO to. It is recommended to create an OU just for Firefox computers. The below example shows this GPO named as “FFMSI”.



5. Edit the GPO as shown below

The filepath to the MSI package cannot be a literal path. It must be an FQDN path.

The deployment type should be “assigned”.

6. The GPO will now be applied to the computers within it’s scope. This happens at Windows startup and it can also be done on demand by typing “gpupdate /force” from a command line on the target computer. The command “gpresult /R” can be used to show which Group Policy settings were applied . 

7. If the end-user already has Firefox installed under C:\Program Files\ they should not see any effect from the GPO which installs the Firefox MSI. If the end-user does not already have Firefox installed, the GPO will install it from the MSI to C:\Program Files\

Step 2- Making a text file which Firefox will read it’s proxy configuration from.

1. Create a text file in the same shared folder where the Firefox MSI is located.

2. Edit the file to contain text similar to this :

//

lockPref("browser.startup.homepage", "http://www.yahoo.com");

lockPref("network.proxy.http", "10.1.2.78");

lockPref("network.proxy.http_port",8881);

lockPref("network.proxy.type", 1);

lockPref("network.proxy.no_proxies_on", "localhost, 127.0.0.1");

lockPref("network.proxy.share_proxy_settings", true);



The first line of the file must read //

The configuration must begin on the second line of the file.

The file must be saved as mozilla.cfg

Step 3- Making a GPO to push the mozilla.cfg file to the Firefox installation folder.

1. Create the GPO in the OU that you want to deploy this GPO to. It is recommended to create an OU just for Firefox computers. The below example shows this GPO named as “FFsettings”.

2. Edit the GPO as shown below

The filepath to the mozilla.cfg file cannot be a literal path. It must be an FQDN path.

The target/destination for the mozilla.cfg file is the literal Firefox installation path.

The action type should be “Replace”.

3. The GPO will now be applied to the computers within it’s scope. This happens at Windows startup and it can also be done on demand by typing “gpupdate /force” from a command line on the target computer. The command “gpresult /R” can be used to show which Group Policy settings were applied . 

4. When the end-user restarts their computer, their Firefox proxy settings should be configured with the details in the mozilla.cfg file, and those settings should be unavailable from the UI (grayed out). It may take more than one restart, or a manual gpupdate /force. It depends on the complexity of the Windows domain setup, e.g if there are multiple Domain Controllers.