Typed static analysis for concurrent, policy-based, resource access control

We present a type and effect system for statically determining whether concurrent programs in a simple functional language adhere to a strict access control policy. Policy states are represented by automata states and are tracked, statically, by the type and effect system. We ensure that, per thread, all function calls are, independently, in accordance with policy with respect to the current state. To verify that several concurrent threads jointly satisfy a policy we are required to explore the state space of an interleaving of the several threads’ effects. However, we observe that by furnishing our language with monitor synchronisation primitives we can reduce our state space search by abstracting away behaviours inside atomic sections. The type and effect system is proved to satisfy Subject Reduction and a Safety theorem which guarantees that well-typed programs never violate policy.