VST-Flow: Fine-grained low-level reasoning about real-world C code

TL;DR

This paper extends the Verified Software Toolchain (VST) with support for information-flow security proofs, introducing new Hoare rules and implementation strategies in Coq for secure reasoning about C code.

Contribution

It presents a novel approach to integrate information flow security into VST, including new Hoare rules and a framework for automated proofs in Coq.

Findings

Defined information flow security in continuation-passing style

Proposed Hoare rules with security assertions

Outlined implementation in Coq and adaptation of VST-Floyd

Abstract

We show how support for information-flow security proofs could be added on top of the Verified Software Toolchain (VST). We discuss several attempts to define information flow security in a VST-compatible way, and present a statement of information flow security in "continuation-passing" style. Moreover, we present Hoare rules augmented with information flow control assertions, and sketch how these rules could be proven sound with respect to the definition given before. We also discuss how this can be implemented in the Coq proof assistant, and how VST's proof automation framework (VST-Floyd) can be adapted to support convenient information flow security proofs.