arXiv subjects

Sébastien Bardin

Publications and source records attributed to Sébastien Bardin.

26 records · Page 2Linked to original sources

arXiv2018

Model Generation for Quantified Formulas: A Taint-Based Approach

We focus in this paper on generating models of quantified first-order formulas over built-in theories, which is paramount in software verification and bug finding. While standard methods are either geared toward proving the absence of solution or targeted to specific theories, we propose a generic approach based on a reduction to the quantifier-free case. Our technique allows thus to reuse all the efficient machinery developed for that context. Experiments show a substantial improvement over state-of-the-art methods.

cs.LO↗

arXiv2017

Abstract Interpretation using a Language of Symbolic Approximation

The traditional abstract domain framework for imperative programs suffers from several shortcomings; in particular it does not allow precise symbolic abstractions. To solve these problems, we propose a new abstract interpretation framework, based on symbolic expressions used both as an abstraction of the program, and as the input analyzed by abstract domains. We demonstrate new applications of the frame- work: an abstract domain that efficiently propagates constraints across the whole program; a new formalization of functor domains as approximate translation, which allows the production of approximate programs, on which we can perform classical symbolic techniques. We used these to build a complete analyzer for embedded C programs, that demonstrates the practical applicability of the framework.

cs.SE↗

arXiv2017

Freeing Testers from Polluting Test Objectives

Testing is the primary approach for detecting software defects. A major challenge faced by testers lies in crafting efficient test suites, able to detect a maximum number of bugs with manageable effort. To do so, they rely on coverage criteria, which define some precise test objectives to be covered. However, many common criteria specify a significant number of objectives that occur to be infeasible or redundant in practice, like covering dead code or semantically equal mutants. Such objectives are well-known to be harmful to the design of test suites, impacting both the efficiency and precision of testers' effort. This work introduces a sound and scalable formal technique able to prune out a significant part of the infeasible and redundant objectives produced by a large panel of white-box criteria. In a nutshell, we reduce this challenging problem to proving the validity of logical assertions in the code under test. This technique is implemented in a tool that relies on weakest-precondition calculus and SMT solving for proving the assertions. The tool is built on top of the Frama-C verification platform, which we carefully tune for our specific scalability needs. The experiments reveal that the tool can prune out up to 27% of test objectives in a program and scale to applications of 200K lines of code.

cs.SE↗

arXiv2017

CDCL-inspired Word-level Learning for Bit-vector Constraint Solving

The theory of quantifier-free bit-vectors (QF_BV) is of paramount importance in software verification. The standard approach for satisfiability checking reduces the bit-vector problem to a Boolean problem, leveraging the powerful SAT solving techniques and their conflict-driven clause learning (CDCL) mechanisms. Yet, this bit-level approach loses the structure of the initial bit-vector problem. We propose a conflict-driven, word-level, combinable constraints learning for the theory of quantifier-free bit-vectors. This work paves the way to truly word-level decision procedures for bit-vectors, taking full advantage of word-level propagations recently designed in CP and SMT communities.

cs.LO↗

arXiv2017

Generic and Effective Specification of Structural Test Objectives

While a wide range of different, sometimes heterogeneous test coverage criteria have been proposed, there exists no generic formalism to describe them, and available test automation tools usually support only a small subset of them. We introduce a unified specification language, called HTOL, providing a powerful generic mechanism to define test objectives, which permits encoding numerous existing criteria and supporting them in a unified way. HTOL comes with a formal semantics and can express complex requirements over several executions (using a novel notion of hyperlabels), as well as alternative requirements or requirements over a whole program execution. A novel classification of a large class of existing criteria is proposed. Finally, a coverage measurement tool for HTOL objectives has been implemented. Initial experiments suggest that the proposed approach is both efficient and practical.

cs.SE↗

arXiv2016

Targeting Infeasibility Questions on Obfuscated Codes

Software deobfuscation is a crucial activity in security analysis and especially, in malware analysis. While standard static and dynamic approaches suffer from well-known shortcomings, Dynamic Symbolic Execution (DSE) has recently been proposed has an interesting alternative, more robust than static analysis and more complete than dynamic analysis. Yet, DSE addresses certain kinds of questions encountered by a reverser namely feasibility questions. Many issues arising during reverse, e.g. detecting protection schemes such as opaque predicates fall into the category of infeasibility questions. In this article, we present the Backward-Bounded DSE, a generic, precise, efficient and robust method for solving infeasibility questions. We demonstrate the benefit of the method for opaque predicates and call stack tampering, and give some insight for its usage for some other protection schemes. Especially, the technique has successfully been used on state-of-the-art packers as well as on the government-grade X-Tunnel malware -- allowing its entire deobfuscation. Backward-Bounded DSE does not supersede existing DSE approaches, but rather complements them by addressing infeasibility questions in a scalable and precise manner. Following this line, we propose sparse disassembly, a combination of Backward-Bounded DSE and static disassembly able to enlarge dynamic disassembly in a guaranteed way, hence getting the best of dynamic and static disassembly. This work paves the way for robust, efficient and precise disassembly tools for heavily-obfuscated binaries.

cs.CR↗

arXiv2013

A Combined Approach for Constraints over Finite Domains and Arrays

Arrays are ubiquitous in the context of software verification. However, effective reasoning over arrays is still rare in CP, as local reasoning is dramatically ill-conditioned for constraints over arrays. In this paper, we propose an approach combining both global symbolic reasoning and local consistency filtering in order to solve constraint systems involving arrays (with accesses, updates and size constraints) and finite-domain constraints over their elements and indexes. Our approach, named FDCC, is based on a combination of a congruence closure algorithm for the standard theory of arrays and a CP solver over finite domains. The tricky part of the work lies in the bi-directional communication mechanism between both solvers. We identify the significant information to share, and design ways to master the communication overhead. Experiments on random instances show that FDCC solves more formulas than any portfolio combination of the two solvers taken in isolation, while overhead is kept reasonable.

cs.LO↗

arXiv2013

Efficient Leverage of Symbolic ATG Tools to Advanced Coverage Criteria

Automatic test data generation (ATG) is a major topic in software engineering. In this paper, we seek to bridge the gap between the coverage criteria supported by symbolic ATG tools and the most advanced coverage criteria found in the literature. We define a new testing criterion, label coverage, and prove it to be both expressive and amenable to efficient automation. We propose several innovative techniques resulting in an effective black-box support for label coverage, while a direct approach induces an exponential blow-up of the search space. Initial experiments show that ATG for label coverage can be achieved at a reasonable cost and that our optimisations yield very significant savings.

cs.SE↗