1520596 - AutoplayPolicy incorrectly thinks we have 'autoplay-media' permission when we're sharing screen

Status: NEW

(Core :: Audio/Video: Playback, enhancement, P5)

Description

[Alastor Wu [:alwu]]

While I was testing my patches from bug1520088, I found that nsContentUtils::IsExactSitePermAllow would return incorrect result even if the principle doesn't have that permission type.

For example, calling nsContentUtils::IsExactSitePermAllow(aPricinple, "wtf") would return true. That function returned true from [1].

My usage scenario is in AutoplayPolicy, I would use top level document's principle to check whether sites have autoplay-media permission or not. I don't want it return true when site doesn't have that permission.

[1] https://searchfox.org/mozilla-central/rev/c21d6620d384dfb13ede6054015da05a6353b899/extensions/cookie/nsPermissionManager.cpp#2310-2313

[2] https://searchfox.org/mozilla-central/rev/bee8cf15c901b9f4b0c074c9977da4bbebc506e3/dom/media/AutoplayPolicy.cpp#94-99

Comment 1

[Alastor Wu [:alwu]]

Hi, Smaug,
Could you help me take a look for this bug? or help me direct this NI to person who can help.
Thank you!

Comment 2

[Alastor Wu [:alwu]]

FYI, I was testing this site [1], and then I found IsExactSitePermAllow(aPricinple, "autoplay-media") would return true after I got the screen permission.

[1] https://www.webrtc-experiment.com/screen-sharing/#21212466423507326

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Are you passing wrong principal?
https://searchfox.org/mozilla-central/rev/c21d6620d384dfb13ede6054015da05a6353b899/extensions/cookie/nsPermissionManager.cpp#2310-2313 makes very much sense, since it is dealing system principal.

Comment 4

[Alastor Wu [:alwu]]

After some investigation, the autoplay checking for playing screen sharing happened on the chrome process, so we actually passed the system pricinple to the permission manager, which means nsContentUtils::IsExactSitePermAllow() is good without problem.

So now I will investigate why this happen on the chrome process, instead of child process, because it seems to me that the sharing content is the part of child process.

Comment 5

[Alastor Wu [:alwu]]

This is a low priority bug, won't cause any bug, I just curious about some unexpected behaviors.