[tor-bugs] #13875 [Tor Browser]: Tor Browser DPI spoofing is broken (was: Tor Browser DPI spoofing is broken if the user changes zoom level)

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#13875: Tor Browser DPI spoofing is broken
-------------------------+-------------------------------------------------
     Reporter:  isis     |      Owner:  tbb-team
         Type:  defect   |     Status:  reopened
     Priority:  major    |  Milestone:
    Component:  Tor      |    Version:
  Browser                |   Keywords:  tbb-fingerprinting, tbb-testcase,
   Resolution:           |  tbb-firefox-patch
Actual Points:           |  Parent ID:
       Points:           |
-------------------------+-------------------------------------------------
Changes (by gk):

 * keywords:  tbb-fingerprinting => tbb-fingerprinting, tbb-testcase, tbb-
     firefox-patch
 * priority:  normal => major


Comment:

 Replying to [comment:8 mikeperry]:
 > Reopened this to dup the other way, ie: calling #8076 the dup (or simply
 closed, as this ticket contains the results of investigation).

 Well, the investigation is not over, there is still the CSS case and the
 things we wanted to study (large amount of variability) which is why I
 duped it the way I did. That said I don't feel so strongly that I'd start
 duping this over again but I think we should make sure that a fix we
 provide for this particular PoC catches all the other DPI-spoofing-is-
 broken-scenarios, too.

 Some relevant resources from #8076:

 https://developer.mozilla.org/en-US/docs/CSS/resolution
 https://bugzilla.mozilla.org/show_bug.cgi?id=564815 (the devicePixelRatio
 bug)

 Oh, and while I am at it: the issue is visible with a default Tor Browser
 without messing with the zoom at all (which is why I changed the summary
 and raised the priority).

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13875#comment:9>
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