Last year I wrote an SSO plugin (auto-login from smart card) for 1.12.6, based on the http pass-thru plugin. I'm trying to use my plugin with v1.15.8 and only the regular user login seems to work.  The admin login (scp) appears broken.  At this point I'm just trying to rule out possibilities.
Have their been any API changes between the versions? Here's the main part of the code that has the problem. I have verifid that it does get the user's email correctly and that the lookup function returns the user.
`
class HttpAuthentication extends StaffAuthenticationBackend{
var $config
function __construct($config){
	
	$this->config = $config;
}
function supportsInteractiveAuthentication(){
	return false;
}
function signOn(){
	// stuff for reading smart card, assigns value to $upn
	$email = AuthHelper::getEmail($upn, $this-config); // looks up user email in AD
	$user = StaffSession::lookup($email);
	if (($user = StaffSession::lookup($email)) && $user->getId()){
		return $user;
	}
}
}
`