Intent to Experiment: Anonymous iframes

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Arthur Sonzogni

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Jul 27, 2022, 9:34:56 AM7/27/22

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Summary

Anonymous iframes give developers a way to load documents in third party iframes using new and ephemeral contexts. Anonymous iframes are a generalization of COEP credentialless to support 3rd party iframes that may not deploy COEP. Like with COEP credentialless, we replace the opt-in of cross-origin subresources by avoiding to load non-public resources. This will remove the constraint that 3rd party iframes must support COEP in order to be embedded in a COEP page and will unblock developers looking to adopt cross-origin-isolation. This way, developers using COEP can now embed third party iframes that do not.

Blink component

Blink>SecurityFeature

Search tags

coep, cross-origin-embedder-policy, iframe, anonymous

TAG review

https://github.com/w3ctag/design-reviews/issues/639

TAG review status

Issues addressed

Risks

Interoperability and Compatibility

The main risk is that anonymous iframes fail to become an interoperable part of the web platform if other browsers do not implement the API.

Gecko: No signal (https://github.com/mozilla/standards-positions/issues/628)

WebKit: No signal (https://lists.webkit.org/pipermail/webkit-dev/2022-April/032205.html)

Web developers: Positive (https://github.com/WICG/proposals/issues/53) Zoom, Google Display Ads, StackBlitz are supportive. Several other developer also expressed their need to get anonymous iframe to embed 3rd party iframes inside crossOriginIsolated contexts.

Other signals:

Ergonomics

None.

Activation

We are going to publish a blog post: We don't expect developers having difficulties using is as-is. It only requires adding the "anonymous" attribute to <iframe>.

Security

See the threat model doc: https://wicg.github.io/anonymous-iframe/#security http://go/anonymous-iframe-threat-model

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?

No risks identified. This is platform independent. WebView is not an exception.

Goals for experimentation

- Double check the feature makes sense given large developers like Google Ads and Zoom. - Confirm this resolves the difficulties deploying COEP and understand any limitations. - Get feedback about the shape of the API. - Understand if developers need additional APIs to use it. For instance: https://github.com/w3ctag/design-reviews/issues/742 or others.

Reason this experiment is being extended

Ongoing technical constraints

None

Debuggability

Anonymous iframes were designed to avoid breaking iframes. They do not introduce new kinds of failures. In the devtool issue explaining an iframe was blocked by COEP, Anonymous iframes will be suggested as a potential solution. The JS API: `window.isAnonymouslyFramed` already reflects whether a document is embedded inside an anonymous iframe or not. This is not reflected in devtool yet, but it could be in the future, if we think this is worth it.

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?

Yes

This is a web platform feature. Consistent behavior among all the platforms is important.

Is this feature fully tested by web-platform-tests?

Yes

DevTrial instructions

https://anonymous-iframe.glitch.me

Flag name

--enable-blink-features=AnonymousIframe

Requires code in //chrome?

False

Tracking bug

https://bugs.chromium.org/p/chromium/issues/detail?id=1211800

Launch bug

https://bugs.chromium.org/p/chromium/issues/detail?id=1342928

Estimated milestones

OriginTrial desktop last	108
OriginTrial desktop first	106
DevTrial on desktop	105

OriginTrial Android last	108
OriginTrial Android first	106
DevTrial on Android	105

OriginTrial webView last	108
OriginTrial webView first	106

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5729461725036544

Links to previous Intent discussions

Intent to prototype: https://groups.google.com/a/chromium.org/g/blink-dev/c/CjrLTguZuO4

This intent message was generated by Chrome Platform Status.

Mike Taylor