[tor-bugs] #16267 [Tor Browser]: NoCaptcha Recaptcha is not working because of canvas fingerprint blocking
Tor Bug Tracker & Wiki
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Tue Jun 9 19:35:08 UTC 2015
#16267: NoCaptcha Recaptcha is not working because of canvas fingerprint blocking
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Reporter: szgal | Owner: tbb-team
Type: defect | Status: new
Priority: normal | Milestone:
Component: Tor Browser | Version:
Resolution: | Keywords: tbb-usability-website
Actual Points: | Parent ID:
Points: |
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Comment (by cypherpunks):
>it draws images to a canvas and then uses toDataUrl()
A, yeh, really.
I thinked a bit and now I know how to fix canvas fingerprinting for
toDataUrl.
1 toDataUrl must return not data: URI, but a blob: URI. It won't break
sites which use this URI to show the image to the user, but it will
disallow to derive pixel data from it.
2 It must be only allowed to be used as an URI for image: in CSS, as src
for IMG, etc. Using it in XHR or anything other than image must be
disallowed.
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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16267#comment:5>
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