Enforcing the confidentiality and integrity of information is critical in distributed applications. Production systems typically use some form of authorization mechanism to protect information, but these mechanisms do not typically provide end-to-end information security guarantees. Information flow control mechanisms provide end-to-end security, but their guarantees break down when trust relationships may change dynamically, a common scenario in production environments. This dissertation presents flow-limited authorization, a new foundation for enforcing information security. Flow-limited authorization is an approach to authorization in that it can be used to reason about whether a principal is permitted to perform an action. It is an approach to information flow control in that it can be used to reason about whether a flow of information is secure.

This dissertation presents the theoretical foundation of this approach, the Flow-Limited Authorization Model (FLAM). FLAM uses a novel principal algebra that unifies authority and information flow policies and a logic for making secure authorization and information flow decisions. This logic ensures that such decisions cannot be influenced by attackers or leak confidential information.

We embed the FLAM logic in a core programming model, the Flow-Limited Authorization Calculus (FLAC). FLAC programs selectively enable flows of information; the type system ensures that attackers cannot create unauthorized flows. A well-typed FLAC not only ensures proper authorization, but also secure information flow.

The FLAC approach to secure programming is instantiated in \textsc{Flame}, a library and compiler plugin for enforcing flow-limited authorization in Haskell programs. Flame uses type-level constraints and monadic effects to statically enforce flow-limited authorization for Haskell programs in a modular way.