Support Apple Pay in cross-origin iframes with allow=payment attribute

• Component: WebCore Misc.
• Status: RESOLVED FIXED

[Brad]

Web pages that use a third party payment vendor for a checkout flow may integrate the vendor in a cross-origin iframe to prevent the vendor from accessing non-payment data on the top level/main origin. However, this integration does not allow using Apple Pay due to this error: https://github.com/WebKit/WebKit/blob/Safari-612.1.11/Source/WebCore/Modules/applepay/PaymentSession.cpp#L63

The Payment Request spec supports this use case by allowing the top level/main origin to delegate payments permission to an iframe using the allow attribute: https://www.w3.org/TR/payment-request/#using-with-cross-origin-iframes. This opt-in mechanism prevents abuse by untrusted iframes because the top origin determines which of its children it intends to provide payments.

Safari/WebKit should support this attribute/use case in the Payment Request and Apple Pay APIs.

[Devin Rousso]

*** This bug has been marked as a duplicate of bug 167417 ***

[Brad]

The duplicate ticket didn't end up addressing this issue: https://bugs.webkit.org/show_bug.cgi?id=229406#c15

Could we get input from someone on Apple Pay on resolving this?

[Radar WebKit Bug Importer]

<rdar://problem/88969594>

[Javier López Navarro]

I have created a Pull Request on the WebKit repository with the changes suggested by Brad solving this issue.
https://github.com/WebKit/WebKit/pull/11485

[EWS]

Committed 262616@main (fead01e13ad2): <https://commits.webkit.org/262616@main>

Reviewed commits have been landed. Closing PR #11485 and removing active labels.