[tor-bugs] #29745 [Applications/Tor Browser]: Exposed chrome:// resources allow browser version and OS detection [Bug 1534581]

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#29745: Exposed chrome:// resources allow browser version and OS detection [Bug
1534581]
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 Reporter:  flngerprlnt               |          Owner:  tbb-team
     Type:  defect                    |         Status:  new
 Priority:  High                      |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:  tbb-fingerprinting        |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by Thorin):

 From upstream, that this can also leak the app language: see [1]. Leaking
 browser version is not an issue, all TB users should be on the same ESR
 cycle - and you can't defeat feature detection anyway. Detecting OS is
 trivial as well (for now)

 Suggest changing the title, and keyword => `tbb-fingerprinting-locale` .
 As it happens, I checked the contents of `chrome://global/locale/intl.css`
 in all 30 language packs, and I've lost my notes on them: about 6 or 7
 have extra css rules which could be used: namely that French one, LTR
 languages, and from memory, a couple of non-Latin languages such as
 Japanese. Of course, there may be other `chrome://` files that leak more
 entropy.

 [1] https://bugzilla.mozilla.org/show_bug.cgi?id=1534581#c21

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29745#comment:2>
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