Time-Staging Enhancement of Hybrid System Falsification

Optimization-based falsification employs stochastic optimization algorithms to search for error input of hybrid systems. In this paper we introduce a simple idea to enhance falsification, namely time staging, that allows the time-causal structure of time-dependent signals to be exploited by the optimizers. Time staging consists of running a falsification solver multiple times, from one interval to another, incrementally constructing an input signal candidate. Our experiments show that time staging can dramatically increase performance in some realistic examples. We also present theoretical results that suggest the kinds of models and specifications for which time staging is likely to be effective

Compositional Vulnerability Detection with Insecurity Separation Logic

Memory-safety issues and information leakage are known to be depressingly common. We consider the compositional static detection of these kinds of vulnerabilities in first-order C-like programs. Existing methods often treat one type of vulnerability (e.g. memory-safety) but not the other (e.g. information leakage). Indeed the latter are hyper-safety violations, making them more challenging to detect than the former. Existing leakage detection methods like Relational Symbolic Execution treat only non-interactive programs, avoiding the challenges raised by nondeterminism for reasoning about information leakage. Their implementations also do not treat non-trivial leakage policies like value-dependent classification, which are becoming increasingly common. Finally, being whole-program analyses they cannot be applied compositionally -- to deduce the presence of vulnerabilities in a program by analysing each of its parts -- thereby ruling out the possibility of incremental analysis. In this paper we remedy these shortcomings by presenting Insecurity Separation Logic (InsecSL), an under-approximate relational program logic for soundly detecting information leakage and memory-safety issues in interactive programs. We show how InsecSL can be soundly automated by bi-abduction based symbolic execution. Based on this, we design and implement a top-down, contextual, compositional, inter-procedural analysis for vulnerability detection. We implement our approach in a proof-of-concept tool, Underflow, for analysing C programs, which we demonstrate by applying it to various case studies

A Hoare Logic with Regular Behavioral Specifications

We present a Hoare logic that extends program specifications with regular expressions that capture behaviors in terms of sequences of events that arise during the execution. The idea is similar to session types or process-like behavioral contracts, two currently popular research directions. The approach presented here strikes a particular balance between expressiveness and proof automation, notably, it can capture interesting sequential behavior across multiple iterations of loops. The approach is modular and integrates well with autoactive deductive verification tools. We describe and demonstrate our prototype implementation in SecC using two case studies: A matcher for E-Mail addresses and a specification of the game steps in the VerifyThis Casino challenge

Compositional Verification of a Lock-Free Stack with RGITL

This paper describes a compositional verification approach for concurrentalgorithms based on the logic Rely-Guarantee Interval Temporal Logic (RGITL),which is implemented in the interactive theorem prover KIV. The logic makes itpossible to mechanically derive and apply decomposition theorems for safety andliveness properties. Decomposition theorems for rely-guarantee reasoning, linearizability and lock-freedom are described and applied on a non-trivial running example,a lock-free data stack implementation that uses an explicit allocator stack for memory reuse. To deal with the heap, a lightweight approach that combines ownershipannotations and separation logic is taken

IC0701 verification competition 2011

Abstract. This paper reports on the experiences with the program verification competition held during the FoVeOOS conference in October 2011. There were 6 teams participating in this competition. We discuss the three different challenges that were posed and the solutions developed by the teams. We conclude with a discussion about the value of such competitions and lessons that can be learned from them.