A Framework for the Modular Specification and Orchestration of Authorization Policies

Many frameworks for defining authorization policies fail to make a clear distinction between policy and state. We believe this distinction to be a fundamental requirement for the construction of scalable, distributed authorization services. In this paper, we introduce a formal framework for the definition of authorization policies, which we use to construct the policy authoring language APOL. This framework makes the required distinction between policy and state, and APOL permits the specification of complex policy orchestration patterns even in the presence of policy gaps and conflicts. A novel aspect of the language is the use of a switch operator for policy orchestration, which can encode the commonly used ruleand policy-combining algorithms of existing authorization languages. We define denotational and operational semantics for APOL and then extend our framework with statically typed methods for policy orchestration, develop tools for policy analysis, and show how that analysis can improve the precision of static typing rules.