[tor-bugs] #10703 [TorBrowserButton]: Fallback charset enables fingerprinting of bundle localization

Thu Jan 23 07:08:32 UTC 2014

#10703: Fallback charset enables fingerprinting of bundle localization
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     Reporter:  dcf               |      Owner:  mikeperry
         Type:  defect            |     Status:  needs_review
     Priority:  normal            |  Milestone:
    Component:  TorBrowserButton  |    Version:
   Resolution:                    |   Keywords:  tbb-fingerprinting
Actual Points:                    |  Parent ID:
       Points:                    |
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Comment (by dcf):

 Replying to [ticket:10703 dcf]:
 > JavaScript in the HTML measures the size of the rendered characters.

 Actually it's even easier than measuring the size. You can look at the
 `innerHTML` and get a string with exactly the decoded characters in it.
 Here is what `encodeURIComponent(elem.innerHTML)` looks like for the
 example sequence "\xc3\a3":
  * utf-8: ã %C3%A3
  * iso-8859-1: Ã£ %C3%83%C2%A3
  * iso-8859-2: ĂŁ %C4%82%C5%81
  * windows-1251: ГЈ %D0%93%D0%88
  * euc-kr: 찾 %EC%B0%BE
  * gbk: 茫 %E8%8C%AB

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/10703#comment:4>
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