Correct Audit Logging: Theory and Practice

Abstract

Retrospective security has become increasingly important to the theory and practice of cyber security, with auditing a crucial component of it. However, in systems where auditing is used, programs are typically instrumented to generate audit logs using manual, ad-hoc strategies. This is a potential source of error even if log analysis techniques are formal, since the relation of the log itself to program execution is unclear. This paper focuses on provably correct program rewriting algorithms for instrumenting formal logging specifications. Correctness guarantees that the execution of an instrumented program produces sound and complete audit logs, properties defined by an information containment relation between logs and the program's logging semantics. We also propose a program rewriting approach to instrumentation for audit log generation, in a manner that guarantees correct log generation even for untrusted programs. As a case study, we develop such a tool for OpenMRS, a popular medical records management system, and consider instrumentation of break the glass policies.