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End-to-End Verification of Information-Flow Security for C and Assembly Programs

Last modified: Sun Jun 26 02:09:36 2016 GMT.

PLDI Artifact Evaluation

Authors

David Costanzo
Zhong Shao
Ronghui Gu

Abstract

Protecting the confidentiality of information manipulated by a computing system is one of the most important challenges facing today's cybersecurity community. A promising step toward conquering this challenge is to formally verify that the end-to-end behavior of the computing system really satisfies various information-flow policies. Unfortunately, because today's system software still consists of both C and assembly programs, the end-to-end verification necessarily requires that we not only prove the security properties of individual components, but also carefully preserve these properties through compilation and cross-language linking.

In this paper, we present a novel methodology for formally verifying end-to-end security of a software system that consists of both C and assembly programs. We introduce a general definition of observation function that unifies the concepts of policy specification, state indistinguishability, and whole-execution behaviors. We show how to use different observation functions for different levels of abstraction, and how to link different security proofs across abstraction levels using a special kind of simulation that is guaranteed to preserve state indistinguishability. To demonstrate the effectiveness of our new methodology, we have successfully constructed an end-to-end security proof, fully formalized in the Coq proof assistant, of a nontrivial operating system kernel (running on an extended CompCert x86 assembly machine model). Some parts of the kernel are written in C and some are written in assembly; we verify all of the code, regardless of language.

Published

In Proc. 2016 ACM SIGPLAN Conference on Programming Language Design and Implementation (PLDI'16), Santa Barbara, CA, pages 648-664, June 2016.
  • Conference Paper [PDF]
  • Slides for the PLDI'16 Talk [PDF] and [PPTX w. full animation]
  • Extended Technical Report [PDF]

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