[tor-bugs] #23104 [Applications/Tor Browser]: CSS line-height reveals the platform Tor Browser is running on

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#23104: CSS line-height reveals the platform Tor Browser is running on
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 Reporter:  gk                                   |          Owner:  igt0
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tbb-fingerprinting-os,               |  Actual Points:
  TorBrowserTeam201709R                          |
Parent ID:                                       |         Points:
 Reviewer:  gk                                   |        Sponsor:
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Comment (by igt0):

 Great question, the css2 specification[1] says that the line height factor
 should be between 1.0 and 1.2. Mozilla uses 1.2 for some time[2] and only
 if the ascending and descending values are 0. Chrome has its own thing[3].

 That said, for the short and medium term, I think the current test makes
 sense because if the line factor changes, the test will break. I tried to
 think about a ref test instead of JS test. However the 1.2 value would be
 hardcoded on it anyway.

 [1] https://www.w3.org/TR/CSS2/visudet.html
 [2] https://developer.mozilla.org/en-US/docs/Web/CSS/line-height
 [3] https://bugs.chromium.org/p/chromium/issues/detail?id=455754

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23104#comment:12>
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