1. A method of employing single sign-on in shared services environments, the method comprising: by a broker server system comprising computer hardware, performing pass-through authentication, the performing comprising: receiving credentials from a client system, the credentials corresponding to a user of the client system; attempting to authenticate, using the credentials, an identity of the user by communicating the credentials to an authentication server; receiving, from the authentication server, an indication that the credentials are expired; passing the expired credentials to a target resource to which the client system has requested access so as to cause the target resource to initiate a process for changing the expired credentials; generating, after the credentials have been changed, a ticket comprising a reference to the credentials; and providing the ticket to the client system, wherein the client system is enabled to provide the ticket to the target resource to obtain access to the target resource.