[tor-commits] [tor-browser-spec/master] Describe font limiting.

mikeperry at torproject.org mikeperry at torproject.org
Mon Apr 28 15:18:48 UTC 2014

commit be2c61fff30c20801707a1fd8597e89de18b043f
Author: Mike Perry <mikeperry-git at fscked.org>
Date:   Wed Dec 28 22:21:20 2011 -0600

    Describe font limiting.
 docs/design/design.xml |   21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/docs/design/design.xml b/docs/design/design.xml
index 0a5df12..df15dbe 100644
--- a/docs/design/design.xml
+++ b/docs/design/design.xml
@@ -1233,18 +1233,17 @@ number of bits available to the adversary while avoiding the rendering and
 language issues of supporting a global font set.
-     <para><command>Design Goal:</command>
-We intend to <ulink
-url="https://trac.torproject.org/projects/tor/ticket/2872">limit the number of
-fonts</ulink> a url bar origin can load, gracefully degrading to built-in
-and/or remote fonts once the limit is reached.
-     </para>
      <para><command>Implementation Status:</command>
-Aside from disabling plugins to prevent enumeration, we have not yet
-implemented any defense against CSS or Javascript fonts.
+We disable plugins, which prevents font enumeration. Additionally, we limit
+both the number of font queries from CSS, as well as the total number of 
+fonts that can be used in a document by patching Firefox. We create two prefs,
+<command>browser.display.max_font_attempts</command> and
+<command>browser.display.max_font_count</command> for this purpose. Once these
+limits are reached, the browser behaves as if
+<command>browser.display.use_document_fonts</command> was reached. We are
+still working to determine optimal values for these prefs. <!-- XXX: Link
+patch and document pref values. -->
@@ -1298,7 +1297,7 @@ hooks</ulink> as well as a window observer to <ulink
 new windows based on desktop resolution</ulink>. Additionally, we patch
 Firefox to cause CSS Media Queries to use the client content window size
-for all desktop size related media queries. <!-- FIXME: link patch --> 
+for all desktop size related media queries. <!-- XXX: link patch --> 

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