I have recently created a module that allows my users to sign in to our CAS SSO website and authenticate to the DNN portal. If a user account does not exist for them, one is created and their profile and user account attributes are gathered from our local LDAP server.

However, I had to modify the admin\Security\logoff.aspx page in order to redirect to our SSO logout page. This breaks the core because if a new version of DNN is installed it will overwrite this page. Is there another way to hook into the logout functionality? Maybe through the authentication provider?

I've already added my 2 lines of code to logout of our SSO to the logout.ascx. But when DNN gets upgraded again it might overwrite those changes. A new membership provider does not meet the SSO requirement (we've tried, believe me), so the only way that I could do the custom login was to write a module for that. That is fine because DNN allows you to specify your login page and I just put the custom login module on a hidden page and I was done. However, the same is not true for the logout page. Regardless of where the loginTabId is pointed to, you cannot change the LogoutTabId (for lack of a better term). I hope this gets fixed in future version.