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Full Description
Abu?erover?owoccurswheninputiswrittenintoamemorybu?erthatisnot large enough to hold the input. Bu?er over?ows may allow a malicious person to gain control over a computer system in that a crafted input can trick the defectiveprogramintoexecutingcodethatisencodedintheinputitself.They are recognised as one of the most widespread forms of security vulnerability, and many workarounds, including new processor features, have been proposed to contain the threat. This book describes a static analysis that aims to prove the absence of bu?er over?ows in C programs. The analysis is conservative in the sense that it locates every possible over?ow. Furthermore, it is fully automatic in that it requires no user annotations in the input program. Thekeyideaoftheanalysisistoinferasymbolicstateforeachp- gram point that describes the possible variable valuations that can arise at that point. The program is correct if the inferred values for array indices and pointer o?sets lie within the bounds of the accessed bu?er. The symbolic state consists of a ?nite set of linear inequalities whose feasible points induce a convex polyhedron that represents an approximation to possible variable valuations. The book formally describes how program operations are mapped to operations on polyhedra and details how to limit the analysis to those p- tionsofstructuresandarraysthatarerelevantforveri?cation.Withrespectto operations on string bu?ers, we demonstrate how to analyse C strings whose length is determined by anul character within the string.
Contents
From the Contents: Preface.- Introduction.-Value Range Analysis.- Analysing C.- A Semantics for C.- Core C.- Related Work.- Part 1 Abstracting Soundly.- Abstract State Space.- Points-To Analysis.- Numeric Domains.- Taming Casting and Wrapping.- A Language Featuring Finite Integer Arithmetic.- Implicit Wrapping of Polyhedral Variables.- Explicit Wrapping of Polyhedral Variables.- An Abstract Semantics for SubC.- Discussion.- Overlapping Memory Accesses and Pointers.- Memory as a Set of Fields.- Mixing Values and Pointers.- Abstraction Relation.- Abstract Semantics.- Part II Ensuring Efficiency.- Planar Polyhedra.- Operations on Inequalities.- Operations on Sets of Inequalities.- The TVPI Abstract Domain.- The Integral TVPI Domain.- Interfacing Analysis and Numeric Domain.- Inferring Relevant Fields and Addresses.- Applying Widening in Fixpoint Calculations.- Part III Improving Precision.- Tracking String Lengths.- Widening with Landmarks .- Combining Points-To and Numeric Analysis.- Conclusion and Outlook
