s

Dr Sharar Ahmadi


Research Fellow

Academic and research departments

Computer Science Research Centre.

Publications

Sharar Ahmadi, Brijesh Dongol, Matt Griffin (2022)Proving Memory Access Violations in Isabelle/HOL, In: Proceedings of the 8th ACM SIGPLAN International Workshop on Formal Techniques for Safety-Critical Systems (FTSCS 2022)pp. 45-55 Association for Computing Machinery (ACM)

Security-critical applications often rely on memory isolation mechanisms to ensure integrity of critical data (e.g., keys) and program instructions (e.g., implementing an attestation protocol). These include software-based security microvisor (SµV) or hardware-based (e.g., TrustLite or SMART). Here, we must guarantee that none of the assembly-level instructions corresponding to a program violate the imposed memory access restrictions. We demonstrate our approach on two architectures (SµV and TrustLite) on which remote at-testation protocols are implemented. We extend an approach based on the Binary Analysis Platform (BAP) to generate compiled assembly for a given C program, which is translated to an assembly intermediate language (BIL) and ultimately to Isabelle/HOL theories. In our extension, we develop an adversary model and define conformance predicates imposed by an architecture. We generate a set of programs covering all possible cases in which an assembly-level instruction attempts to violate at least one of the conformance predicates. This shows that the memory access restriction of both SµV and TrustLite are dynamically maintained. Moreover, we introduce conformance predicates for assembly-level instructions that can change the control flow, which improve TrustLite's memory protection unit.