[tbb-bugs] #31978 [Applications/Tor Browser]: Support use of policies.json

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#31978: Support use of policies.json
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 Reporter:  segfault                  |          Owner:  tbb-team
     Type:  defect                    |         Status:  needs_information
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:                            |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by segfault):

 > Wouldn't that mean you need to back out the patch for #30575, too?

 Yes, indeed.

 > I would not be very happy to do that and would object doing that for all
 platforms.

 I understand.

 > If we don't find a better solution we could think about supporting
 policies.json for Linux only. I wonder, though, whether one could fix your
 original problems without hacking around them with policies.json.
 >
 > So, what are your issues? Do you know what is causing them?

 We were able to find workarounds for most of the issues now. Two issues
 which we couldn't solve yet are:

 * "Tor Browser 9 sometimes won't load new URLs" [1].
 * "JavaScript sometimes blocked on Tor Browser first start" [2].

 To be honest, I'm not sure how policies.json would help us with those. The
 customizations which policies.json would make simpler for us are:

 * Enable a custom theme for our Unsafe Browser (which is also a customized
 Tor Browser) [3]. The current workaround requires us to ship a
 `addonStartup.json.lz4` file, which Firefox/Tor Browser usually generated
 when it's started.
 * Disabling the update check [4].

 We're worried that our workarounds to keep the customizations working are
 using methods that are unsupported by Mozilla (for example patching and
 repacking `tor-browser/browser/omni.ja`, and shipping
 `addonStartup.json.lz4`), require more and more hacks, and may be the root
 cause for more and more weird behavior ([1] and [2] for example). Using
 policies.json would allow us to drop some of these hacks, especially the
 `addonStartup.json.lz4` file and some preferences we set in `omni.ja`.

 [1] https://redmine.tails.boum.org/code/issues/17121
 [2] https://redmine.tails.boum.org/code/issues/17007
 [3] https://redmine.tails.boum.org/code/issues/17055
 [4] https://redmine.tails.boum.org/code/issues/17114

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31978#comment:2>
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