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Re: Screensharing: Bootstrapping Collaboration between Capturer and Capturee

From: Youenn Fablet <youenn@apple.com>
Date: Mon, 14 Jun 2021 17:16:22 +0200
Message-id: <27865B0F-9F76-4DD5-87F7-F4D9BD8B7A33@apple.com>
Cc: Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com>, Elad Alon <eladalon@google.com>, WebRTC WG <public-webrtc@w3.org>
To: Jan-Ivar Bruaroey <jib@mozilla.com>
>> I really like apis when they allow untrusted parties to collaborate securely allowing more freedom to the end user and I think it is a goal  it is worth pursuing. 
> Communication channels between two untrusted parties is always something to look closely at, from a security and privacy standpoint.
> A safe model is to have the UA in the middle: the UA triggers these actions on behalf of the user, not on behalf of the capturer.
> For instance, by presenting UA UI in the capturer page to control capturee through actions, similar to picture-in-picture for VC.
> For instance if capturee page is playing a video, it might be convenient from capturer page to pause the capturee video using the play/pause actions.
> A further step would be to allow capturer page to blend well with this UA UI.
> So I hear 3 directions for presentation control actions:
> A: UA triggers these standard actions on behalf of the capturer.
> B: UA triggers these standard actions on behalf of the user, not on behalf of the capturer.
> C: Out of band between mutually participating properties only, based on id.
> I think both A and B sound promising. Youenn, it seems to me A might have slightly better ergonomics, so I'm curious about what risks B might mitigate.

A and B are not exclusive, B could be implemented and deployed faster than A.
I believe B is the current MediaSession approach and has the same security context.

A is an extension to this approach and needs additional scrutiny since now capturer, which is not as trusted as UA, is the one deciding to trigger these actions.
For instance, capturer might iterate through all slides while not displaying the captured live stream to the user.
Or multiple capturers can interact with the same capturee.
This is not to say it is impossible but it probably requires more work.
Received on Monday, 14 June 2021 15:17:04 UTC

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