[tbb-bugs] #16672 [Tor Browser]: Text rendering allows fingerprinting

[Tor Bug Tracker & Wiki]

#16672: Text rendering allows fingerprinting
-------------------------+-------------------------------------------------
     Reporter:           |      Owner:  tbb-team
  arthuredelstein        |     Status:  needs_review
         Type:  defect   |  Milestone:
     Priority:  normal   |    Version:
    Component:  Tor      |   Keywords:  tbb-fingerprinting-fonts, tbb-5.0,
  Browser                |  TorBrowserTeam201508R
   Resolution:           |  Parent ID:
Actual Points:           |
       Points:           |
-------------------------+-------------------------------------------------

Comment (by dcf):

 Replying to [comment:16 dcf]:
 > However it doesn't change the checksum relative to comment:15. It is
 still 1-8854c333. And when I zoom in, I can still see subpixel
 antialising. This is surprising to me because I know that both system
 fonts.conf and subpixels were on my mind when I made the fonts.conf from
 #13313, and I'm pretty sure I tested them back then.

 I went back and tested the bundles from comment:1:ticket:13313
 (https://people.torproject.org/~dcf/pt-bundle/4.0-alpha-3-fonts-1/). They
 indeed turn off subpixel antialiasing and do not load the Fontconfig files
 under /etc. Here are a transcript and screenshot. You can zoom in and see
 that there is no colored fringe around the letters.
 {{{
 $ FC_DEBUG=1024 ./start-tor-browser
 Launching Tor Browser for Linux in /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser...

 (process:29279): GLib-CRITICAL **: g_slice_set_config: assertion
 'sys_page_size == 0' failed
 FC_DEBUG=1024
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/fonts.conf
         Scanning config dir /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/65-0-lohit-
 marathi.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/65-0-lohit-
 nepali.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/65-droid.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/65-lohit.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-
 assamese.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-
 bengali.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-
 devanagari.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-
 gujarati.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-
 kannada.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-
 oriya.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-
 punjabi.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-tamil-
 classical.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-
 tamil.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/66-lohit-
 telugu.conf
         Loading config file /home/david/4.0-alpha-3-fonts-1/tor-
 browser_en-US/Browser/TorBrowser/Data/fontconfig/conf.d/67-lohit-
 malayalam.conf
 }}}

 [[Image(4.0-alpha-3-fonts-1.png)]]

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16672#comment:17>
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