Intent to Experiment: FedCM Button Mode API and Use Other Account API
Yi Gu
Contact emails
yi...@chromium.org, cbies...@chromium.org, tanza...@chromium.org
Explainer
https://github.com/fedidcg/FedCM/issues/442
Specification
https://fedidcg.github.io/FedCM
This will be added as an extension.
Summary
We plan to experiment with two new extensions for the Federated Credential Management (FedCM) API:
Button Mode API
The button mode lets websites trigger FedCM directly when a user clicks a button (like a "Sign-in with IdP" button). This means FedCM will always display a visible user interface for login, in contrast to the widget mode where no UI is shown if a user’s login status is logged out.
When the FedCM API is used in "button mode" and a user isn't logged in, they'll be taken to the IdP login screen (in a pop-up window). Since this happens in response to a clear user action, the UI might even be more prominent (e.g., centered and modal) compared to the more subtle UI of widget mode.
Use Other Account API
With this API, an Identity Provider can request the browser to show a button that allows users to choose other accounts.
Blink component
Search tags
TAG review
https://github.com/w3ctag/design-reviews/issues/935
TAG review status
Pending
Risks
Interoperability and Compatibility
These are extensions to the FedCM API. Apple and Mozilla have both expressed a positive opinion on the initial FedCM API [1]. They have not yet shipped but Mozilla is prototyping [2]. If a user agent chooses not to implement these extensions, the sign-in flow should not be affected in that user agent because developers can fallback to the existing federated sign-in mechanisms.
[1] https://groups.google.com/a/chromium.org/g/blink-dev/c/URpYPPH-YQ4/m/bzghj9N3AQAJ
[2] https://groups.google.com/a/mozilla.org/g/dev-platform/c/ncmUwK1uO98/m/COhPA4ZrAAAJ
Gecko: No signal
WebKit: No signal
Web developers: Positive (https://github.com/fedidcg/FedCM/issues/442) These features are being developed to address existing feedback for the FedCM API.
Other signals:
Activation
Similar to the FedCM API, we deliberately leave the bulk of the work to the IdP to ensure that minimal RP change is needed.
This feature, specifically, is one that can be currently controlled by IdP (via JS SDK for “button mode”, via server-side config for “use other account”), so we expect activation to have a similar profile as FedCM: immediately enabled to websites (without redeployment) by IdPs making use of it (by redeploying their JS SDKs).
Security
The button mode shares most of the security properties from the widget mode. e.g. honoring CSP, CORS, using security headers, not asking users to type in the browser UI etc.
It’s worth noting that the pop-up window has the same web platform properties as what one would get with window.open(url,””,”popup,noopener,noreferrer”) that loads the login_url. It is important to note that there's no communication allowed between the website and this pop-up (e.g. no postMessage, no window.opener). We have shipped LoginStatus API and Error API in FedCM that use this type of pop-up window.
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?
None
Goals for experimentation
Gather data on whether a browser mediated sign in flow on a critical user journey is well received by users and developers. We'd like to see how the proposed UI/API play out and iterate on them to ship the API in its best shape.
Ongoing technical constraints
None
Debuggability
Same as FedCM in general – console messages in devtools and general JS debugging
Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?
No
FedCM API is not available in WebView
Is this feature fully tested by web-platform-tests?
Not yet.
We will continue adding tests before the experiment starts.
Flag name on chrome://flags
FedCmButtonMode, FedCmUseOtherAccount
Finch feature name
kFedCmButtonMode
kFedCmUseOtherAccount
Non-finch justification
None
Requires code in //chrome?
True
Tracking bug
Launch bug
https://launch.corp.google.com/launch/4293366
Estimated milestones
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/4689551782313984
Links to previous Intent discussions
Intent to prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CACh2XCPzJ1beiSbsmQqvu9x24zmf6LkGuup%3DgPVyXEx%2Bux9%3Dyg%40mail.gmail.com
This intent message was generated by Chrome Platform Status.
Mike Taylor
LGTM to experiment from M124 to M127 inclusive.
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Mike Taylor
That said, please request approvals from the various review gates
in your chromestatus entry before experimenting.
Yoav Weiss (@Shopify)
That said, please request approvals from the various review gates in your chromestatus entry before experimenting.
On 2/26/24 7:41 PM, Mike Taylor wrote:
LGTM to experiment from M124 to M127 inclusive.
On 2/26/24 5:45 PM, Yi Gu wrote:
Contact emailsyi...@chromium.org, cbies...@chromium.org, tanza...@chromium.org
Explainer
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Yi Gu
Thanks for the suggestion! We have a flowchart in that thread to try to explain what a browser would do in case a user is not logged in to the IdP but maybe it's not very clear. The answer to your questions is yes. IdP controls which login page the new window would load (by reusing the required "login_url" field from LoginStatus API). However they cannot choose another way to handle user logged-out in the middle of a FedCM button flow. In addition, we provided this deck of mocks w.r.t. how Chrome plans to implement the Button flow. We may change some of the UI affordance during OT and will publish a blog post with instruction and proposed UX soon.