Opened 5 months ago

Last modified 5 months ago

#30531 new defect

WebGL antialiasing support enabled iff. OpenGL is supported

Reported by: intrigeri Owned by: tbb-team
Priority: Medium Milestone:
Component: Applications/Tor Browser Version:
Severity: Normal Keywords: AffectsTails, tbb-fingerprinting
Cc: Actual Points:
Parent ID: Points:
Reviewer: Sponsor:

Description

With Tor Browser 8.5-build2, we see 2 different WebGL fingerprints on panopticlick: 2ef68bcd75e09a41aea04bae556f3ecc on bare metal and in VMs that support OpenGL acceleration, f9a0f737691a9b57f5294121fc58a2df in VMs that don't support OpenGL acceleration.

Quoting segfault (from https://redmine.tails.boum.org/code/issues/16337#note-61) who investigated this further:

"I looked at the JS code used by panopticlick to calculate this hash, and printed the values which go into the hash. The only difference I could find is that antialiasing is enabled iff OpenGL is enabled. (That's exposed via the antialias bool of gl.getContextAttributes(), see https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/getContextAttributes)."

Impact: 1 bit of fingerprinting; risk: nowadays I would assume the huge majority of bare metal systems that can run TB have OpenGL, but most VMs haven't (unless geeky configuration is done, which is a minority). So it's roughly equivalent to splitting the anonymity set between VMs and bare metal, I'd say.

GeKo says:

i guess we could think about making the antialiasing info uniform
like, just saying "no"

Child Tickets

Change History (3)

comment:1 Changed 5 months ago by gk

Keywords: tbb-fingerprinting added

Or maybe we should give true back. However, I wonder whether any of that would help anyway as a website could probably test whether anti-aliasing is available by rendering some content.

Last edited 5 months ago by gk (previous) (diff)

comment:2 in reply to:  description ; Changed 5 months ago by cypherpunks

6992168724b997c74fc89f1e4a9301ce on Microsoft Basic Render Driver Direct3D11 vs_5_0 ps_5_0 :(

comment:3 in reply to:  2 Changed 5 months ago by gk

Replying to cypherpunks:

6992168724b997c74fc89f1e4a9301ce on Microsoft Basic Render Driver Direct3D11 vs_5_0 ps_5_0 :(

That's likely a different issue. I've opened #30537 for it (I assume this fingerprint stems from a Windows 10 system, right?).

Note: See TracTickets for help on using tickets.