Symbolic Verification of Cache Side-Channel Freedom

Abstract

Cache timing attacks allow third-party observers to retrieve sensitive information from program executions. But, is it possible to automatically check the vulnerability of a program against cache timing attacks and then, automatically shield program executions against these attacks? For a given program, a cache configuration and an attack model, our CacheFix framework either verifies the cache side-channel freedom of the program or synthesizes a series of patches to ensure cache side-channel freedom during program execution. At the core of our framework is a novel symbolic verification technique based on automated abstraction refinement of cache semantics. The power of such a framework allows symbolic reasoning over counterexample traces and combines it with runtime monitoring for eliminating cache side channels during program execution. Our evaluation with routines from OpenSSL , libfixedtimefixedpoint , GDK , and FourQlib libraries reveals that our CacheFix approach (dis)proves cache side-channel freedom within an average of 75 s. In nearly all test cases, CacheFix synthesizes all patches within 20 min to ensure cache side-channel freedom of the respective routines during execution.