Clamp CSS media query for color and disable system colors

We should reduce the resolution on the CSS media query for color or spoof it entirely.

I could see the clamp approach mapping existing possibilities to only two or three: greyscale, 8bit, and/or 24bit.

I could also see just lying and always saying 24bit.

added actualpoints::7 component::firefox patch issues interview owner::mikeperry priority::high resolution::fixed status::closed tbb-fingerprinting type::defect labels

Always saying 24bit sounds good to me.

Trac:
Cc: N/A to g.koppen@jondos.de

It's also now apparently possible to query system colors directly through the HTML5 canvas: http://eb0b428b.byethost7.com/screen.html

#6253 (closed) might be one way to block that, but there may be other vectors (like trial and error through direct DOMNode comparison).

Apparently, there are several prefs that already exist around Native/System color lookup. The main one seems to be ui.use_native_colors, but it is cached by the style system at startup (so you need a restart to test its effects, which is painful). I'm not sure exactly what effect it has yet.

Trac:
Priority: normal to major
Summary: Clamp CSS media query for color to Clamp CSS media query for color and disable system colors
Cc: g.koppen@jondos.de to g.koppen@jondos.de, shondoit

Trac:
screen.html

Copy of system color test script

Trac:
Keywords: N/A deleted, interview added

https://gitweb.torproject.org/torbrowser.git/blob/maint-2.2:/src/current-patches/firefox/0024-Do-not-expose-system-colors-to-CSS-or-canvas.patch

Creating and testing the artificial system color map was the bulk of the work here.

Trac:
Status: new to closed
Resolution: N/A to fixed
Actualpoints: N/A to 7

closed

added 56h of time spent

mentioned in issue #7006 (closed)

mentioned in issue #7920 (closed)

mentioned in issue #13818 (moved)

mentioned in issue #15197 (moved)

mentioned in issue #18777 (moved)

mentioned in issue tpo/applications/tor-browser#15197 (closed)