[tor-bugs] #32418 [Applications/Tor Browser]: Torbrowser tells on every start, that it can't update although it is newest

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#32418: Torbrowser tells on every start, that it can't update although it is newest
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 Reporter:  Yeti                      |          Owner:  tbb-team
     Type:  defect                    |         Status:  needs_information
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:  tbb-update                |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by mcs):

 Kathy and I did some investigation and learned that (on Windows only)
 Mozilla tries to fix file system permissions whenever it detects that it
 cannot write to the update info directory or to the directory that
 contains the application. Unfortunately, there are quite a few places
 where this kind of fix up is attempted (if you are curious, look for calls
 to `fixUpdateDirectoryPermissions()` within
 `toolkit/mozapps/update/UpdateService.jsm` and trace the call chains).

 If the permission fix up fails, a "manual update required" prompt is shown
 (which is what the reporter of this bug is seeing).

 The entire update service relies upon being able to write to the update
 info directory, so it will be difficult to support a "read only" update
 info directory. In other words, Firefox's updater was not designed with
 this scenario in mind.

 A better approach, assuming we think it is a good idea to support it,
 would be to disable the update checks. Unfortunately, the only way to
 disable update check in recent versions of Firefox is via the enterprise
 policies mechanism, and that mechanism is disabled in Tor Browser (see
 #30575).

 Tor Browser team: Do we want to provide a way to disable the update check,
 e.g., by re-implementing support for the old `app.update.enabled` pref? We
 would need to ensure that that pref is checked very early; for example,
 the UpdateService JS constructor calls a getter that causes the file
 system permission fix to be attempted on Windows, which would trigger the
 "manual update required" prompt. Mozilla removed the capability for users
 to disable the update check because they do not want users to run outdated
 browsers.

 An alternative would be to disable the code that tries to fix file system
 permissions on Windows, but we would then need to verify that doing so
 does not lead to another code path that causes the browser to display an
 update error prompt.

 Another alternative would be to decide that installing in a read-only area
 of the file system and updating the browser manually is not something we
 can support.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32418#comment:4>
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