Trace Properties from Separation Logic Specifications

We propose a formal approach for relating abstract separation logic library specifications with the trace properties they enforce on interactions between a client and a library. Separation logic with abstract predicates enforces a resource discipline that constrains when and how calls may be made between a client and a library. Intuitively, this can enforce a protocol on the interaction trace. This intuition is broadly used in the separation logic community but has not previously been formalised. We provide just such a formalisation. Our approach is based on using wrappers which instrument library code to induce execution traces for the properties under examination. By considering a separation logic extended with trace resources, we prove that when a library satisfies its separation logic specification then its wrapped version satisfies the same specification and, moreover, maintains the trace properties as an invariant. Consequently, any client and library implementation that are correct with respect to the separation logic specification will satisfy the trace properties

Enforcing Programming Guidelines with Region Types and Effects

We present in this paper a new type and effect system for Java which can be used to ensure adherence to guidelines for secure web programming. The system is based on the region and effect system by Beringer, Grabowski, and Hofmann. It improves upon it by being parametrized over an arbitrary guideline supplied in the form of a finite monoid or automaton and a type annotation or mockup code for external methods. Furthermore, we add a powerful type inference based on precise interprocedural analysis and provide an implementation in the Soot framework which has been tested on a number of benchmarks including large parts of the Stanford SecuriBench.Comment: long version of APLAS'17 pape

A Generic Approach to Flow-Sensitive Polymorphic Effects

Effect systems are lightweight extensions to type systems that can verify a wide range of important properties with modest developer burden. But our general understanding of effect systems is limited primarily to systems where the order of effects is irrelevant. Understanding such systems in terms of a lattice of effects grounds understanding of the essential issues, and provides guidance when designing new effect systems. By contrast, sequential effect systems --- where the order of effects is important --- lack a clear algebraic characterization. We derive an algebraic characterization from the shape of prior concrete sequential effect systems. We present an abstract polymorphic effect system with singleton effects parameterized by an effect quantale --- an algebraic structure with well-defined properties that can model a range of existing order-sensitive effect systems. We define effect quantales, derive useful properties, and show how they cleanly model a variety of known sequential effect systems. We show that effect quantales provide a free, general notion of iterating a sequential effect, and that for systems we consider the derived iteration agrees with the manually designed iteration operators in prior work. Identifying and applying the right algebraic structure led us to subtle insights into the design of order-sensitive effect systems, which provides guidance on non-obvious points of designing order-sensitive effect systems. Effect quantales have clear relationships to the recent category theoretic work on order-sensitive effect systems, but are explained without recourse to category theory. In addition, our derived iteration construct should generalize to these semantic structures, addressing limitations of that work