Intent to Ship: User-Agent Client Hints "ch-ua-high-entropy-values" permissions policy

[Mike Taylor]

Contact emails

mike...@chromium.org

Explainer

https://github.com/WICG/ua-client-hints/blob/main/README.md (probably more useful to look at the Summary & Motivation)

Specification

https://wicg.github.io/ua-client-hints/#ch-ua-high-entropy-values

Summary

Adds support for a 'ch-ua-high-entropy-values' permissions policy that enables a top-level site to restrict which documents are able to collect high-entropy client hints via the navigator.userAgentData.getHighEntropyValues() JS API. Restricting collection of high-entropy hints over HTTP is already possible via existing per-client-hint permissions policies.

Blink component

Blink > Network > ClientHints

Web Feature ID

ua-client-hints

Motivation

Currently it's only possible to restrict third-party collection of high-entropy User-Agent Client Hints when they're requested over HTTP (via the various permissions policies associated with each Client Hint, i.e., https://wicg.github.io/client-hints-infrastructure/#policy-controlled-features). The permissions policy introduced in this change allows a first-party site to have more control over which third-parties are allowed to request high-entropy client hints via the getHighEntropyValues JS API, which could be deployed alongside the other permissions policies.

Initial public proposal

https://github.com/WICG/ua-client-hints/issues/151#issuecomment-783668130

TAG review

N/A: UA-CH has already been reviewed by TAG, and this is a small, incremental addition to the API.

TAG review status

Not applicable

Risks

Interoperability and Compatibility

No information provided

Gecko: Neutral (https://mozilla.github.io/standards-positions/#ua-client-hints) I haven't requested a new position for this small addition, since they don't support any of it, but they are neutral on the API itself.

WebKit: No signal (https://github.com/WebKit/standards-positions/issues/70#issuecomment-3488097085) No official position, as it's blocked on a position on Client Hints in general. But I have left a comment with a pointer to this feature.

Web developers: No signals

Other signals:

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?

N/A

Debuggability

No information provided

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

No

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

Yes https://wpt.fyi/results/client-hints/permissions-policy?label=experimental&label=master&aligned 

Flag name on about://flags

No information provided

Finch feature name

ClientHintUAHighEntropyValuesPermissionPolicy

Rollout plan

Will ship enabled for all users

Requires code in //chrome?

False

Tracking bug

https://issues.chromium.org/issues/385161047

Launch bug

https://launch.corp.google.com/launch/4366844

Estimated milestones

Shipping on desktop	144
Shipping on Android	144
Shipping on WebView	144

Anticipated spec changes

Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way).

None

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/6176703867781120?gate=5312509740056576

Links to previous Intent discussions

Intent to Prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/d302cc34-870b-4978-a583-4918ee1631c0%40chromium.org