[tbb-bugs] #13874 [Tor Browser]: Investigate possible DPI spoofing bypass

[Tor Bug Tracker & Wiki]

#13874: Investigate possible DPI spoofing bypass
--------------------------------+--------------------------
 Reporter:  gk                  |          Owner:  tbb-team
     Type:  task                |         Status:  new
 Priority:  normal              |      Milestone:
Component:  Tor Browser         |        Version:
 Keywords:  tbb-fingerprinting  |  Actual Points:
Parent ID:                      |         Points:
--------------------------------+--------------------------
 OxPoly on twitter claims being able to get the actual DPI of a device
 while the user is running Tor Browser. The PoC is:
 {{{
 var devicePixelRatio = window.devicePixelRatio || 1;
 dpi_x = document.getElementById('testdiv').offsetWidth * devicePixelRatio;
 dpi_y = document.getElementById('testdiv').offsetHeight *
 devicePixelRatio;

 alert(dpi_x);
 }}}
 We should verify and if it is indeed an issue fix that.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13874>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online