W3C home > Mailing lists > Public > public-webappsec@w3.org > January 2017

Presentation API in non secure contexts

From: Francois Daoust <fd@w3.org>
Date: Mon, 23 Jan 2017 18:00:44 +0100
To: <public-webappsec@w3.org>, <public-web-security@w3.org>
Cc: "'Kostiainen, Anssi'" <anssi.kostiainen@intel.com>, "mark a. foltz" <mfoltz@google.com>
Message-ID: <008801d2759a$3cf0e7c0$b6d2b740$@w3.org>
Dear Web App Security WG,
[and Hello Web Security IG]

The Presentation API allows an application to request display of web content onto a second screen. While the Presentation API forbids mixed content, it does not require a secure context. We discussed this point with some of you back at TPAC 2015 in Sapporo, and raised it in our request for review shortly afterwards:
https://lists.w3.org/Archives/Public/public-webappsec/2015Nov/0064.html

The feeling was that the overall risk is relatively low: there is permission involved and the API can do little harm to users.

The Second Screen WG would like to confirm with you that this approach is still acceptable. The group received feedback that the spec should require secure contexts, especially because it prompts the user for permission. See discussion starting at:
https://github.com/w3c/presentation-api/issues/362#issuecomment-262102686

The security guidelines in the Presentation API were updated to highlight the need to warn users about origins that are potentially non trustworthy:
https://w3c.github.io/presentation-api/#user-interface-guidelines
... and in particular:
[[ Showing the origin that will be presented will help the user know if that content is from an potentially trustworthy origin (e.g., https:), and corresponds to a known or expected site. The user agent should specifically indicate when the origin requesting presentation is not potentially trustworthy. ]]

As a side note, the Second Screen WG will soon re-publish another Candidate Recommendation of the Presentation API. On the security front, the only changes were to move the mixed content and sandboxing checks to the `PresentationRequest` constructor instead of to individual methods of the `PresentationRequest` object, to "fail early". We do not believe that this should trigger another security review, but feedback is of course always welcome!

Thanks,
Francois,
Staff Contact, Second Screen WG.
Received on Monday, 23 January 2017 17:01:01 UTC

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