The security of our software is critical for consumer confidence, the protection of privacy and valuable intellectual property, and of course national security. Because of our society's increased reliance on software, security breaches can lead to serious personal or corporate losses, and endanger the privacy, liberties, and even the lives of individuals. As threats to software security have become more sophisticated, so too have the techniques and analyses developed to improve it. Symbolic execution has emerged as a fundamental tool for security applications. Its main idea is to run a program using symbolic instead of concrete values: a set of symbols are assigned to the program inputs, and the outputs are expressed as a set of "verification conditions", logical formulas over the input symbols. A number of successful security analyses use symbolic execution and similar methods to recast security questions about programs as constraint satisfaction problems in some formal logic. Automatic reasoners for that logic can then be used to solve those problems. In the last few years, solvers based on Satisfiability Modulo Theories (SMT) techniques have become a natural choice in such approaches to security because of their superior performance and automation compared to more traditional theorem provers and their greater generality with respect to ad-hoc tools or propositional satisfiability solvers.
This collaborative project brings together experts in security and in SMT to pursue two complementary research goals: (i) harness the full power of SMT solvers to improve current security tools based on symbolic analysis; and (ii) design and develop new techniques to address the needs of anticipated future security applications. Specific activities addressing these goals include: collecting challenge benchmark problems from existing security analyses and developing targeted SMT optimizations for these benchmarks; developing appropriate security abstractions in the SMT language used to express security verification conditions; developing logical theories and algorithms for reasoning about character strings in such verification conditions; exposing a general framework for extending the verification condition language; and developing techniques for computing symbolic solution sets for SMT constraints. These activities are expected to (i) significantly increase the flexibility, performance, and reasoning capabilities of SMT solvers in support of security applications; (ii) improve the performance and scalability of current security analyses by leveraging the reasoning power of SMT solvers; and (iii) provide a foundation for new, more powerful, and more expressive security analyses. Overall, this project will help create more scalable and expressive security applications which could have a considerable impact on society as they enable the production of software much more resistant to security attacks.
