Bank login dialog in an iframe when you shop online, how does it work?

I was shopping online and at the time of payment, a login dialog from my bank appears in an iframe, I filled my details and the the online shop page let me go on with the purchase.

How does it work? I guess:

1. The online shop shows you the page with an iframe pointing to your bank login widget.
2. You fill the login details and the bank authenticate you.

Now, how the bank now pass information to the online shop site to tell them you can go on?

Because the login is in an iframe, and as far as I know what happen in the ifr开发者_C百科ame cannot affect the container page. So once you are authenticated in your bank, how the bank tell the online shop page "it's good, go on" ?

Cheers.

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In a typical checkout situation there is as you can imagine a lot that goes on behind the scenes. But typically in this scenario, one would include with the request to the payment provider (i.e. PayPal, SagePay (formerly Protx), DataCash) a return success URL and return error URL. Typically a handler of some description on the ecommerce site would receive a callback from the payment provider (i.e not the iframe) once you have successfully completed authentication with your bank.

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The website could have some webservices or other services running in the background handling the bank response and setting some sort of cookie or session for the site and loading another page.