I am attempting to set up Authorize.net's CIM payment method to work within Magento Community Edition, version 1.7.0.1. Since it is handled quite differently than the DPM and AIM methods, I have built it into the existing Onepage Checkout using an iFrame. I then pass it all the needed information, it works perfectly and Authorize.net completes the transaction and returns to the site.
Here is where the issue lies. I am not sure how to complete the order, and pass the confirmation to the database. What page would I send Authorize.net to for the return? I tried using /checkout/onepage/savePayment but it results in the following error:
"{"error":"The requested Payment Method is not available.","message":"Invalid data."}"
Does anyone know how I might accomplish this?