1575033 - Disallow calling navigator.requestMediaKeySystemAccess() from cross-origin iframes

Status: NEW

(Core :: Audio/Video, enhancement, P3)

Description

[(no longer active)]

Allowing access to EME from third-party contexts allows the extraction of the supported media key systems, which can be a fingerprinting vector. Chrome disallows this access by default, we should probably do the same.

See this spec issue: https://github.com/w3c/encrypted-media/issues/364.

Comment 1

[Bryce Seager van Dyk [:bryce] (he/him) - Not reading bugmail]

:Ehsan, do you know if we have any prior art around feature policy? This file on the spec github makes it look like it's a Chromium specific thing, and I'm wondering if we have anything already in central that we could reference here.

Comment 2

[(no longer active)]

Yes, see bug 1572461 about our latest position on feature policy and what we are planning to implement. Specifically I don't think we want to implement the FP specific parts of that issue. (I've CCed Anne here so that he can correct me if my understanding is wrong!)

Comment 3

[Nils Ohlmeier [:drno]]

As feature policy is not available yet I think we have a dependency here.

Comment 4

[Anne (:annevk)]

Note that enough of Feature Permissions Policy has shipped at this point for EME to make use of it.