In an external system, a request handler may receive, at the external system, a logon ticket from a proprietary software system, the logon ticket associated with a request from a user of the proprietary system for access to the external system. A ticket handler may provide the logon ticket to an authentication service which is configured to perform a validation of the logon ticket at the proprietary system. A session manager may receive, from the authentication service and based on the validation, a user session and access rights related to the requested access. An access control manager may provide the requested access to the user via the proprietary system, according to the access rights and within the user session.