[webkit-dev] Requesting a position on Document Policy

Ian Clelland iclelland at chromium.org
Tue Sep 22 12:28:42 PDT 2020

Pinging this thread again, since the TAG has asked about multi-vendor
interest  <https://github.com/w3ctag/design-reviews/issues/408>as well

Since I sent the original email, there has also been some discussion within
the WebAppSec W3C working group about using Document Policy to deprecate
security-negative features on the web platform; +John Wilander
<wilander at apple.com> who may have additional thoughts on the utility of
this API from that angle.

On Tue, Jul 28, 2020 at 10:02 AM Ian Clelland <iclelland at chromium.org>

> Hi WebKit!
> I'm building out the infrastructure in Blink for Document Policy, and
> would like to ship at least part of it in Chrome for developers to take
> advantage of. I'd like to get an official position from WebKit leads on
> this. I'm also interested in getting thoughts from other WebKit folks about
> the design or implementation.
> Some details:
> Document Policy explainer:
> https://github.com/w3c/webappsec-permissions-policy/blob/master/document-policy-explainer.md
> Document Policy spec:
> https://w3c.github.io/webappsec-permissions-policy/document-policy.html
> GitHub Repository (shared with Permissions Policy (previously Feature
> Policy)): https://github.com/w3c/webappsec-permissions-policy
> Blink intent-to-ship discussion:
> https://groups.google.com/a/chromium.org/g/blink-dev/c/Za159T1QOek/m/lewQUFlBCQAJ
> Also previously discussed at the TAG:
> https://github.com/w3ctag/design-reviews/issues/408
> I think that the last time I brought this to WebKit engineers would have
> been at TPAC last year, where it was discussed in the WebAppSec meetings as
> a way to provide a general configuration mechanism for documents, splitting
> off of ideas that had been floating around at the time for Feature Policy.
> While Document Policy itself doesn't prescribe any actual features, it
> could eventually be used to configure the behaviour of different
> web-platform features, such as:
> - Restricting the use of poorly-performing images
> - Disabling slow synchronous JS APIs
> - Configuring frame, image, or script loading styles
> - Restricting overall document sizes or network usage
> - Restricting patterns which cause page re-layout
> The initial intent, though, is to ship part of this in Chrome to support
> an opt-out for the Scroll-to-text-fragment feature.
> Document Policy has two different mechanisms which can work in conjunction
> with each other: The first is the Document-Policy (and
> Document-Policy-Report-Only) HTTP header, which just sets the policy on the
> document it ships with. The other is a negotiation mechanism between an
> embedder and its embedded content, which uses an Iframe attribute and an
> additional request header.
> I'm currently interested in shipping just the first of these mechanisms in
> Chrome. The second may warrant more discussion and review, and isn't needed
> for the Scroll-to-text-fragment opt-out. The details are in the Chrome
> Platform Status entry:
> https://www.chromestatus.com/feature/5756689661820928
> Feel free to ask any questions; I'm happy to discuss this in whatever
> forum works best for folks,
> Thanks!
> Ian
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