Abstract: A method, apparatus, and computer instructions for authorizing a user to access resources on a data processing system. A request to access resources on the data processing system is received. This request includes a certificate for use in authenticating the user making the request. An authentication process is performed using the certificate. If the user is authenticated, a determination is made as to whether an authorizing agent is specified in the certificate. A mapping for the user is requested from the authorizing agent, if the authorizing agent is specified in the certificate. The user is mapped to a local user on the data processing system using the mapping, in response to receiving the mapping for the user, wherein the user accesses resources on the data processing system as the local user. If an authorizing agent is not specified, the user is denied access to the resources.