Authorization Contracts.

Software components have a wide variety of access control requirements. A one-size-fits-all access control framework will not meet the needs of all of these components. We propose an expressive framework for implementing access control monitors for components. The basis of the framework is a novel concept: the authority environment. An authority environment associates rights with an execution context. The building blocks of access control monitors in our framework are authorization contracts: software contracts that manage authority environments. We've used the framework to implement diverse access control mechanisms (including discretionary access control, stack inspection, history-based access control, and object capabilities), and to write custom access control monitors for three case studies.