Use existing Login system for XenForo?


Well-known member
I would like to add a XenForo forum to an existing site which was built in CodeIgniter (one of the better PHP frameworks). We have nearly 10,000 registered useers, and their passwords are stored hashed and are thus not readable in plaintext.

My intention was to install XenForo, remove all reference to Registration, Username/Email/Password editing/changing, and disable Login/Logout, and link users back to our third-party app for those functions. I was then going to have our app "register" the user in XenForo, and then log them in and out automagically with no user intervention. I have looked at xenAPI, but from what I can see, it seems to be missing a way to just tell XenForo "This user should now be logged in". Instead, it has an "authenticate" function that require us to know the plaintext password of the user.

Am I totally overthinking this and there is some way to keep our third-party authentication and XenForo synced up? Has anyone else either found a solution for outside authentication, or modified xenAPI to directly handle login/logout of XenFoo?