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[tor-bugs] #6253 [Firefox Patch Issues]: Prompt before allowing HTML5 Canvas image extraction
#6253: Prompt before allowing HTML5 Canvas image extraction
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Reporter: mikeperry | Owner: mikeperry
Type: defect | Status: new
Priority: major | Milestone:
Component: Firefox Patch Issues | Version:
Keywords: tbb-fingerprinting | Parent:
Points: | Actualpoints:
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The HTML5 canvas can be used for fingerprinting WebGL and font rendering
as described in http://www.w2spconf.com/2012/papers/w2sp12-final4.pdf. The
fingerprint technique hinges on the ability for JS to extract image/data
urls from the canvas object and hash them and/or compute differences.
There's some demonstration code that works for a specific (but currently
unknown) ruby version here: https://github.com/kmowery/canvas-
fingerprinting.
I think the least-effort defense for now is to simply prompt before image
extraction, and to allow extraction permissions to be set on a url-bar
domain basis if the user has opted to store browser state to disk.
Later, we can think about virtualizing this surface during extraction, but
I don't think we'll need to do that unless every site in the world decides
to make a lolcat captioning HTML5 widget.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/6253>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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