1466438 - Service Workers and uBlock/uMatrix shows the offline page

Status: NEW

(Core :: DOM: Service Workers, defect, P3)

Description

[Karl Dubost💡 :karlcow]

Maybe this has already been mentioned before. 

Steps to reproduce:
1. Install uBlock and uMatrix on Firefox
2. Makes the default option to block everything even first party (CSS, JS, etc.)
3. Allows adactio.com in uBlock and uMatrix (see screenshot)
4. Go to https://adactio.com/links/13955

Expected:
Receive the normal page

Actual:
Receive the offline page saying I'm not connected.

This is an example with adactio.com, but this is happening with all sites with a ServiceWorker. Other examples include 

* Smashing Magazine
  https://www.smashingmagazine.com/
  Where I get a Corrupted Content Error instead.

* Larlet.fr
  https://larlet.fr/david/stream/2018/05/16/
  Where I get an offline page similar to adactio.


The trick is that a simple reload (without changing anything else) actually loads the page on all these sites.

Comment 1

[Karl Dubost💡 :karlcow]

Attachment: service-worker-blocker.jpg

Comment 2

[Ben Kelly [:bkelly, not reviewing]]

> Expected:
> Receive the normal page

While this seems reasonable, I don't know that its actually defined anywhere.  It would be great to actually have a defined model of how web extensions are supposed to work with service worker interception.

Also, I expect this behavior is probably different in non-e10s mode.  When we enable parent-side interception for service workers our behavior will probably switch to what we do in non-e10s mode.  In these configurations its possible the web extensions will block the request before it even gets to the service worker.

Also, this might be related to bug 1437626.  Our content script classification script has the concept of "top window" which doesn't apply for service workers.  This might be confusing the web extensions API.