Racets: Faceted Execution in Racket

Abstract

Faceted Execution is a linguistic paradigm for dynamic information-ow control. Under faceted execution, secure program data is represented by faceted values: decision trees that encode how the data should appear to its owner (represented by a label) versus everyone else. When labels are allowed to be rst-class (i.e., predicates that decide at runtime which data to reveal), faceted execution enables policy-agnostic programming: a programming style that allows privacy policies for data to be enforced independently of code that computes on that data.To date, implementations of faceted execution are relatively heavyweight: requiring either changing the language runtime or the application code (e.g., by using monads). Following Racket's languages-as-libraries approach, we present Racets: an implementation of faceted execution as a library of macros. Given Racket's highly-expressive macro system, our implementation follows relatively directly from the semantics of faceted execution. To demonstrate how R can be used for policy-agnostic programming, we use it to build a web-based game of Ba leship. Our implementation sheds light on several interesting issues in interacting with code wri en without faceted execution. Our R implementation is open source, under development, and available online.