[tbb-bugs] #27290 [Applications/Tor Browser]: WebGL is broken in Tor Browser 8

Tor Bug Tracker & Wiki blackhole at torproject.org
Thu Aug 23 16:19:15 UTC 2018

#27290: WebGL is broken in Tor Browser 8
     Reporter:  gk                        |      Owner:  tbb-team
         Type:  defect                    |     Status:  new
     Priority:  High                      |  Milestone:
    Component:  Applications/Tor Browser  |    Version:
     Severity:  Normal                    |   Keywords:  ff60-esr
Actual Points:                            |  Parent ID:
       Points:                            |   Reviewer:
      Sponsor:                            |
 Going to a demo e.g. http://webglsamples.org/aquarium/aquarium.html shows
 that WebGL is broken in Tor Browser. The first error is:
 Error: WebGL warning: Unable to restrict WebGL limits to minimums.
 The respective script breaks in the last line of
  * Creates a webgl context.
  * @param {!Canvas} canvas The canvas tag to get context
  *     from. If one is not passed in one will be created.
  * @return {!WebGLRenderingContext} The created context.
 tdl.webgl.create3DContext = function(canvas, opt_attribs,
 opt_preferredContextType) {
   if (opt_attribs === undefined) {
     opt_attribs = {alpha:false};
     tdl.misc.applyUrlSettings(opt_attribs, 'webgl');
   var names = ["webgl", "experimental-webgl"];
   if (opt_preferredContextType) {
     names.splice(0, 0, opt_preferredContextType);
   var context = null;
   for (var ii = 0; ii < names.length; ++ii) {
     try {
       context = canvas.getContext(names[ii], opt_attribs);

 Now, this works in Tor Browser if one toggles
 `privacy.resistFingerprinting` to `false`. The interesting part, however,
 is that this works in vanilla Firefox 60.1.0esr with
 `privacy.resistFingerprinting` enabled out of the box.

 I wonder what else we do that is tied to that pref and breaks WebGL.

 This got first noticed on our blog

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27290>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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