LGTM2
On 12/12/22 11:03 PM, Yoav Weiss wrote:
LGTM1
On Mon, Dec 12, 2022 at 8:14 PM Nicolás Peña <[email protected]> wrote:
I was not aware that Permissions-Policy enables having support for
just JS or just HTTP header support, but in our case we want to
ship both, which is the default. I have added a couple of examples
at the bottom of that explainer.
Thanks for adding those examples! :)
On Monday, December 12, 2022 at 4:41:49 AM UTC-5 Yoav Weiss wrote:
On Thu, Dec 8, 2022 at 4:38 PM Nicolás Peña <[email protected]>
wrote:
Contact emails
[email protected]
Explainer
https://github.com/fedidcg/FedCM/blob/main/explorations/iframe_support.md
<https://github.com/fedidcg/FedCM/blob/main/explorations/iframe_support.md>
Would be great to have some more explicit examples in the
explainer. For example, it's not immediately obvious to me if
this would support both HTTP header based delegation as well
as the "allow" attribute on the iframe itself. Would it? Such
support can have implications on the ergonomics story here.
Specification
https://fedidcg.github.io/FedCM/#permissions-policy-integration
Summary
Adds support for calling the FedCM API inside cross-origin
iframes via a permissions policy which sites are opted out
of by default. It enables websites to sandbox the scripts
from identity providers which trigger the FedCM API in an
iframe. We also considered whether this feature could
support "authenticated embeds" use cases where the iframe
itself needs a sign-in from the user. While the UI
currently does not support this scenario, we invite
requirements and feedback from interested parties. In both
cases, the parent frame must provide the cross-origin
iframe with the permissions policy
'identity-credentials-get'. This also allows top-level
contexts to opt out of using FedCM through the Permissions
Policy header.
Blink component
Blink>Identity>FedCM
<https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EIdentity%3EFedCM>
TAG review
This is a small addition to FedCM API that uses an
existing mechanism to give cross-origin iframe control
(permissions policy), so we do not consider this change to
be substantive enough to warrant a separate review.
Previous reviews:
https://github.com/w3ctag/design-reviews/issues/622
<https://github.com/w3ctag/design-reviews/issues/622>
https://github.com/w3ctag/design-reviews/issues/718
<https://github.com/w3ctag/design-reviews/issues/718>
TAG review status
Not applicable
Risks
*
*Interoperability and Compatibility
This is a small addition to the FedCM API, and as such
mostly inherits the interop and compatibility risks from
that API.
Seehttps://groups.google.com/a/chromium.org/g/blink-dev/c/URpYPPH-YQ4/m/E9pgS7GEBAAJ
for the discussion.
Gecko: Positive for the API in general
(https://github.com/mozilla/standards-positions/issues/618),
positive for cross-origin iframe support specifically
(https://github.com/mozilla/standards-positions/issues/701
<https://github.com/mozilla/standards-positions/issues/701>)
WebKit: Positive for the API in general
(https://lists.webkit.org/pipermail/webkit-dev/2022-March/032162.html),
requested signal on cross-origin iframe support
specifically
(https://github.com/WebKit/standards-positions/issues/83
<https://github.com/WebKit/standards-positions/issues/83>)
Web developers: Positive (we know several sites that use
cross-origin iframes for authentication of users via
federation)
Other signals: -
Ergonomics
The main ergonomics risk is that the website must
explicitly add the permissions policy for the iframe where
the identity provider invokes FedCM, which breaks the
FedCM benefit of deploying with no RP change.
Another issue is having a page where both the main frame
and some iframes decide to invoke the FedCM API. Because
we produce a very user visible dialog, we've decided that
multiple calls within the same page are not allowed,
i.e.https://bugs.chromium.org/p/chromium/issues/detail?id=1374422.
In practice, this means that if there were multiple frames
interested in using FedCM within the same page, then the
RP needs to ensure that those frames collaborate so that
they do not try to invoke themselves at the same time, as
otherwise only one of them will be successful in showing
the FedCM dialog.
Activation
Similar to the baseline FedCM API that this I2S is
extending from, the bulk of the work is on the identity
provider to ensure that they call the FedCM API
appropriately. The added work for the RP in the iframe
case is the requirement of a permissions policy, but this
is needed because the FedCM API is very powerful and it's
not reasonable to automatically grant arbitrary
cross-origin iframes with the power to invoke it.
Security
User annoyance from the dialog is dealt with by the
requirement of permissions policy. The top-level frame
needs to explicitly allow any cross-origin iframe to
invoke the FedCM API. The other security consideration
here is the accountability for the dialog: what domain do
we show as the requestor for the FedCM dialog: the
top-level or the cross-origin iframe? The current status
is that we always show the top-level domain. We considered
showing the cross-origin iframe domain in addition to the
top-level, but we are not currently planning to ship it
due to lack of concrete demand for it. Note that this is
consistent with other powerful APIs such as camera and GPS
access.
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 as this feature is not available on WebView.
Debuggability
Besides regular FedCM support, we show a clear error
message stating when the API has failed due to missing
permissions policy.
Will this feature be supported on all six Blink platforms
(Windows, Mac, Linux, Chrome OS, Android, and Android
WebView)?
No
The current implementation is available on all platforms
(Windows, Mac, Linux, ChromeOS and Android) except WebView.
Is this feature fully tested by web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?
Yes
https://wpt.fyi/results/credential-management/fedcm-iframe.https.html?label=master&label=experimental&aligned
<https://wpt.fyi/results/credential-management/fedcm-iframe.https.html?label=master&label=experimental&aligned>
(we’re still working on making tests behave as intended on
WPT.fyi)
Flag name
This can be enabled by going to chrome://flags, and
setting the FedCM feature to “FedCM (Enabled - with iframe
support)”
Requires code in //chrome?
True
Tracking bug
https://bugs.chromium.org/p/chromium/issues/detail?id=1322320
Launch bug
https://launch.corp.google.com/launch/4209514
Sample links
https://fedcm-main-frame.glitch.me
Estimated milestones
Ship 110
Anticipated spec changes
The main spec change
<https://github.com/fedidcg/FedCM/issues/320> that we
anticipated on the initial FedCM I2S has a good path
towards being resolved.
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5162418615877632
This intent message was generated by Chrome Platform
Status <https://chromestatus.com/>.
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