Opened 2 months ago

Closed 2 months ago

#31954 closed task (fixed)

Make sure -webkit-device-pixel-ratio is no fingerprinting risk

Reported by: gk Owned by: tbb-team
Priority: Medium Milestone:
Component: Applications/Tor Browser Version:
Severity: Normal Keywords: tbb-fingerprinting-resolution, ff68-esr, TorBrowserTeam201910
Cc: Actual Points: 0.1
Parent ID: Points: 0.25
Reviewer: Sponsor:

Description

In Firefox 63 finally support landed for webkit prefixed device-pixel-ratio media queries (https://bugzilla.mozilla.org/show_bug.cgi?id=1444139). We should make sure this does not undermine our fingerprinting resistance.

Child Tickets

Change History (1)

comment:1 Changed 2 months ago by gk

Actual Points: 0.1
Keywords: tbb-fingerprinting-resolution added; tbb-fingerprinting removed
Resolution: fixed
Status: newclosed

The Mozilla ticket actually flips just a pref. The implementation work got done back in https://bugzilla.mozilla.org/show_bug.cgi?id=1176968. One can see from the test at https://hg.mozilla.org/mozilla-central/rev/48f644f1c41e that the webkit version is essentially an alias for the moz version (as the implementation notes in the Browser compatibility table for Firefox say). GetScreenPixelsPerCSSPixel() calls GetDevicePixelRatio() and that in turn GetDevicePixelRatioOuter() which is taking care of our fingerprinting concerns (https://searchfox.org/mozilla-esr68/source/dom/base/nsGlobalWindowOuter.cpp#3685). So, we are good here.

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