SSPSecurity::passive_login
Attempt to passively authenticate the user with the identity provider, then SilverStripe.
If the user is not authenticated in SilverStripe but is on the identity provider, this will passively authenticate them in SilverStripe and redirect them to the current page. If the user is already authenticated in SilverStripe this function returns nothing. Passive authentication is not enabled by default and an explicit call to 'SSPSecurity::passive_login()' needs to be added to your 'Page_Controller->init()' function. Please note that passive login only works with the default SSPAuthenticator. Currently it is not possible to specify a custom SSPAuthenticator on demand.
Signature
public function passive_login()