Preinstalled Extension in FF 68.1.0esr doesn't work

Question

I am preparing a firefox enterprise installation on windows server with a special configuration and a preinstalled extension. This is a single installation that will be used by all users accessing the server.

Here are the steps I followed:

1. I installed firefox: Firefox_setup_68.1.0-esr.msi
2. I transferred our policies.json file to C:\Program Files\Mozilla Firefox\distribution
3. I transferred our autoconfig.js file to C:\Program Files\Mozilla Firefox\browser\defaults\preferences
4. I transferred our extName@ourdomain.local.xpifile to C:\Program Files\Mozilla Firefox\browser\extensions.

By running FireFox, I can see that both the policies and the configurations have been correctly considered, while the extension does not work.

After doing various tests I can say that:

• the extension is correctly loaded and enabled, in autoconfig.json there are these directive:

  pref("extensions.autoDisableScopes", 0);
  pref("extensions.enabledScopes", 15);
  

• the extension is not signed, but in the autoconfig.json file there is the directive:

  pref ("xpinstall.signatures.required", false);
  

• trying to install the extension from the Add-ons Manager using the item: Install Add-on from file ... It works correctly. Unfortunately I can't use this option, because Extension is installed only for current user.

So, given that the extension works, what's wrong with the preparation procedure, is the directory wrong or some configuration are missing?

Do preinstalled extensions need additional files or a different layout?

I also tried without our policies.json file and leaving only the directive that allows xpi file without signature in the autoconfig.json file.

Any help will be greatly appreciated, thanks

Answer 1

Finally I found a syntax error in policies.json file and a missing section.

Following policies page it was not very clear to me what was //path/to/xpi. This is the examples:

"Extensions": {
     "Install": ["https://addons.mozilla.org/firefox/downloads/somefile.xpi", "//path/to/xpi"],
     "Uninstall": ["bad_addon_id@mozilla.org"],
     "Locked":  ["addon_id@mozilla.org"]
   }

Finally I found that using a file url works.

Rereading the indicated page, I also noticed that the ExtensionSettings section was missing, fixing the path and adding this section now the extension is correctly installed and works!

Here is an examples of policies.json fixed:

{
  "policies": { 
    "Extensions": {
      "Install": ["file:///C:/Program Files/Mozilla Firefox/browser/extensions/extName@ourdomain.local.xpi"],
      "Uninstall": [],
      "Locked":  []
    },
    "ExtensionSettings": {
      "*": {
        "blocked_install_message": "Custom error message.",
        "install_sources": ["https://addons.mozilla.org/"],
        "installation_mode": "blocked"
      },
      "extName@ourdomain.local": {
        "installation_mode": "force_installed",
        "install_url": "file:///C:/Program Files/Mozilla Firefox/browser/extensions/extName@ourdomain.local.xpi"
      }
    }
  }
}