Lots of people on this forum seem to misread this one.
If cardholder data is POSTed to your server, and then you send it on to a third party, then you're receiving and transmitting, and you've got to be in compliance.
Don't touch credit card numbers. Not even to hot-potato it. If it touches you, it leaves a stain, and removing it will cost you high tens of thousands of dollars.
It's sort of like speeding, but with bigger tickets. Most people do it, but it's risky.
Why isn't anyone offering a thin wrapper service that lets you host a payment form yourself (giving you complete control of the page), and then POST the result to the service which just forwards to one of the major processors?
You get full control of the form, and your server never transmits CC data, so it's out of scope for PCI compliance.
My thought process was that it would work like this:
Merchant - Hosts a a payment form, but it POSTs to the service's server basically <form method="post" action="https ://someservice.com">
Service - Receives the POST and forwards it on to Auth.NET, Paypal Pro, or whoever the Merchant is using to process transactions. The user is redirected back to merchantwebsite.com with appropriate response data.
Are you saying the merchant website would still need to be PCI compliant or just the Service's?
I definitely understand that the service would have to be PCI compliant. But it seems like it'd be a valuable service for a number of small e-commerce providers to essentially outsource online PCI compliance with minimal downside.
EDIT: While I haven't used them, my understanding is that Braintree offers pretty much exactly this service, except that they require that they provide your merchant account and act as your payment processor.
Having said that:
The technical risk of you hosting HTML that POST's via HTTPS somewhere else is that any input that influences any dynamic component of the page on which the form is hosted could alter the "action" attribute of the form to point somewhere else, without it even being detectable in the page source.
You can say that about any chain of pages, including in-app page flows all the way through Google SERPs, but it's a particularly severe risk on the actual page that asks for the credit card number, since there are no macro-level cues a user has as to whether the page is valid or not.
OWASP is making more noise about things like "insecure redirects" for, among other things, this exact scenario. Expect the "host the HTML FORM that asks for the credit card number and send it to the payment processor" technique to run afoul of PCI DSS any year now.