US Patent 6192476: Controlling access to a resource

A method and system are provided for determining whether a principal (e.g. a thread) may access a particular resource. According to one aspect of the invention, the access authorization determination takes into account the sources of the code on the call stack of the principal at the time the access is desired. Because the source of the code on the call stack will vary over time, so will the access rights of the principal. Thus, when a request for an action is made by a thread, a determination is made of whether the action is authorized based on permissions associated with routines in a calling hierarchy associated with the thread. The determination of whether a request is authorized is based on a determination of whether at least one permission associated with each routine encompasses the permission required to perform the requested action. Support for “privileged” routines is also provided. When a routine in the calling hierarchy is privileged, the determination of whether an action is authorized is made by determining whether at least one permission associated with each routine between and including the privileged routine and a second routine in the calling hierarchy encompasses the permission required to perform the requested action.