We have a current magento site. We have an outside site that we need to connect via SSO (we have the details for the connection, key, etc). You must integrate the SSO link so that when a button is clicked on a modal window is brought up, with the external site displayed. Ideally you will be able to override the CSS of the external site with our own CSS. Once the action is completed in the external site, there is a "finish" type button that when clicked closes the modal window and adds to the cart.