Microsoft uses fuzz testing internally and says it runs the largest fuzzing lab in the world. This can be used as an argument to z3 or other smt solvers. Fuzzing, a blackbox method that mutates seed input values, is generally incapable of generating diverse inputs that exercise all paths in the program. Current testing techniques used by developers of smt solvers do not satisfy the high demand for correct and robust solvers, as our testing experiments show. Vijay ganesh talk outline 2 topics covered in lecture on sat solvers motivation for sat smt solvers in software engineering. As with many other successful applications of smt solvers, there is a focus on reducing the number of queries that most be made and preprocessing the input to a solver. In computer science and mathematical logic, the satisfiability modulo theories smt problem is a decision problem for logical formulas with respect to combinations of background theories expressed in classical firstorder logic with equality. Whitebox fuzzing for security testing sage has had a remarkable impact at microsoft. Taking a leaf out of his book ive decided to accompany these with a video that demonstrates the tools described in operation and. Z3 is a satisfiability modulo theories smt solver that integrates several decision procedures.
The tool can handle various nonlinear real functions such as polynomials, trigonometric. Smt solvers for software security tales of automation usenix security workshop on offensive technologies woot12 august 7th 2012, bellevue, wa, usa julien vanegue microsoft security science sean heelan immunity inc. There are different ways that fuzzing tools generate inputs to pass to the target program. Optimizing symbolic execution for malware behavior. By design, such avoidance limits the extent to which the smt solver is able to apply the. Sometimes an alternative to proof assistants, satis. A concrete use case is fuzz testing a technique which continuously tests a program against generated inputs until it crashes. Automated prover smt solver the why platform cjava programs mllike programs jessie coq who pangolin why pangoline. Sage is a whitebox fuzzing tool for security testing. Georgy nosenko an introduction to the use smt solvers for software security. But on the other hand, it will often go deeper in the programs state space. Fuzzing requires test automation, that is, the ability to execute tests automatically. Program analysis and testing using satisfiability modulo.
To improve this situation, we propose to complement traditional testing techniques with grammarbased blackbox. Verification back ends such as smt solvers are typically highly complex pieces of software with performance, correctness and robustness as key requirements. Smt solvers and applications vijay ganesh university of waterloo winter 20 wednesday, 16 january. I will report on our experience running sage for over 500machine years in microsofts security testing labs. It is not a comprehensive survey, but a basic and rigorous introduction to some of the key ideas. They focus on testing controlflow reachability properties of programs. Mechanical proof assistants have always had support for inductive proofs. Smt solver as a small part of an larger set of algorithms.
Interesting starting points for gathering background differential testing for software william m. Therefore, robustness and correctness are essential criteria. Results of running 8 solvers on the example why3 programs with a timeout value of 10 seconds. Smt solver z3 26 to decide a vulnerable program from. An smt solver will then return a satisfying assignm ent, if one exists. Grammarbased blackbox input fuzzing proved to be effective to uncover bugs in smt solvers but is entirely inputbased and. It is used in various software verification and analysis applications. All satisfiable constraints are mapped to n new inputs, which are tested and ranked according to incremental instruction coverage. Typically, fuzzers are used to test programs that take structured inputs. Contents introduction overview smt solvers equality reasoning arithmetic combination of theories satis ability. Inspired by the utility of fuzzers, we introduce stringfuzz and. For the purpose of optimizing the smt solver, a benchmark of smt expressions extracted by intercepting the angrs call to the smt solver ref.
However, the technique could take significant amount of time and effort to complete during the test phase of the software development lifecycle. Smt tactics available in the theorem solver z3 have been analyzed and combined with the purpose of finding the sweetspot between accuracy and performance as detailed. In particular, stateoftheart testing techniques do not reliably detect when an smt solver is unsound. Predicting smt solver performance for software veri. The inner magic behind the z3 theorem prover microsoft. Program analysis and testing using satisfiability modulo theories yet another conference 1 october 2012, moscow. Stateofthe art smt solvers, however, usually provide a rich api, which often introduces additional. Georgy nosenko an introduction to the use smt solvers for. Evaluation and application of two fuzzing approaches for. You get a propositional model from the solver and then check if it satisfies your background theory.
Clarke carnegie mellon university, pittsburgh, pa 152 abstract. Dec 18, 2010 smt solvers are widely used as core engines in many applications. Such legal inputs might be human produced or automated, for example from a grammar or smt solver query. Several of our applications are in the context of the z3 smt solver available from microsoft research. Abstract we introduce stringfuzz, a software tool for automatically testing string smt solvers. This chapter covers some of these areas where smt solvers have been used. Since its inception in 2003, the initiative has pursued these aims by focusing on the following concrete goals. We restrict the classification to bugs that manifest themselves as an incorrect solver result. An introduction to smt solvers and their applications part 1 andrew reynolds university of iowa october, 2017. Pdf smt solvers for software security researchgate.
A curated list of fuzzing resources books, courses free and paid, videos, tools, tutorials and. While z3, which is a satisfiability modulo theories smt solver, was intentionally designed with a general interface that would allow easy incorporation into other types of software development and analysis tools, we couldnt possibly have dreamed up the kind of uses weve seen, from biological computation analysis to solving pebbling. String smt solvers are specialised software tools for solving the satisfiability modulo theories smt problem with string contraints, which is a type of constraint satisfaction problem applicable in industry. Nov 19, 20 georgy nosenko an introduction to the use smt solvers for software security 1. An introduction to smt solvers and their applications part 1. Mckeeman differential testing, a form of random testing, is a component of a mature testing technology for large software systems. Full verification of smt solvers, however, is difficult due to their complex nature and still an open question. The main idea of the original fuzzing approach is to test programs with random inputs. Fuzzing is the third main approach for hunting software security vulnerabilities. Each element of a column must be unique in that column. View on github this is a one day workshop on using smt solvers for reverse engineering i gave at the honeynet project annual workshop in 2016. At a high level, our technique systematically explores execution paths of a program under test as in whitebox fuzzing, a. Fuzzing is a powerful testing technique which is typically used in the domains of software security and quality.
In order to demonstrate the use of a symbolic emulator ill apply it to the problem of whitebox fuzzing i. Software testing, verification and reliability 14, 2 2004. Fuzzing smt solvers with reinforcement learning uwspace. It contains the full slides, as well as the tasks and solutions. Since we installed smt solvers plugin into the rodin platform, the smt tactic button is now accessible in the proof control bar. Due to the pathexplosion problem and dependence on smt solvers, symbolic execution may also not achieve high path coverage. Concise bug explanation using smt solver upenn curf. Such smt solvers are just a leg up on sat solvers by dressing things up in an easierto. Fuzzing and deltadebugging smt solvers software testing. Over the last few years having seen some of the presentations by pablo sole on deplib, blogposts by sean heelan, and having messed around a little bit with the reil in binnavi we were really curious to get a. Thus this will likely be hard for any smt solver, and demonstrates that software verification is a hard problem in general unless pnp, or at least integer factorization becomes easy. I would say a first prototype is much easier achieved using an outer loop around the solver. Reviewing software testing techniques for finding security vulnerabilities. Fuzzing for smt solvers kyle dewey, mehmet emre, ben hardekopf university of california, santa barbara.
Z3 is a new and efficient smt solver freely available from microsoft research. An smt solver for nonlinear theories over the reals. Smt lib is an international initiative aimed at facilitating research and development in satisfiability modulo theories smt. Translating to the smt expression format given that we are using an smt solver z3, it is often useful to retrieve the corresponding smt expression for a symbolic expression. Using metrics based on total analyses time and number of queries issued to the smt solver. Smt solvers for software security george nosenko, security researcher at digital security 2. Satsmt solvers and applications university of waterloo. Boolector is an smt solver for the theory of bitvectors and the extensional theory of arrays over bitvectors. We empirically show using nine large opensource programs that overall, munch achieves higher indepth function coverage than symbolic execution or fuzzing alone. Fuzzing repeatedly executes an application with all kinds of input variants with the goal of finding security bugs, like bufferoverflows or crashes. Fuzzing a sudoku puzzle is probably not the best idea, because it is a very special corner case to reach exactly that one puzzle probably there is only one solution that is the solved version of the input. You can use the jfssmt2cxx tool to convert smtlibv2 constraints into a program.
Encode a program path as a query to a satsmt solver. We provide relevant background on coverageguided fuzzing 2. Satisfiability modulo theories smt solvers are fundamen tal tools in the broad context of software engineering and security re search. These variables can be used to encode constraints placed on the variables in the program. It won first places in the prestigious bitvector and bitvector with arrays tracks in the smt competition. This is a one day workshop on using smt solvers for reverse engineering i gave at the honeynet project annual workshop in 2016. To improve this situation, we propose to complement traditional testing techniques with grammarbased blackbox fuzz testing, combined with deltadebugging.
Smt solvers are extensively used in formal methods, most notably in software verification e. Grammar based fuzzing works by having the tool generate input informed by. Tools and algorithms for the construction and analysis of systems 4963 budapest, april 2008, 337340. It is not directed at experts but at potential users and developers of smt solvers. Care must be taken to avoid socalled matching loops, which may prevent termination of the solver. Most acm queue readers might think of program verification research as mostly theoretical with little impact on the world at large. Satsmt solvers and applications vijay ganesh university of waterloo winter 20 wednesday, 9 january. Such smt solvers are just a leg up on sat solvers by dressing things up in an easiertowrite and easiertoreasonwith language. It performs symbolic execution dynamically at the binary x86 level, generates constraints on program inputs, and solves those constraints with an smt solver in order to. Detecting critical bugs in smt solversusing blackbox.
Our sat solver precosat won three medals in the sat competition 2009. Our idea is to transform an smt formula into a program whose input. Fuzzing or fuzz testing is an automated software testing technique that involves providing invalid, unexpected, or random data as inputs to a computer program. Smt solvers for software security openwall community wiki. Satisfiability modulo theories smt problem is a decision problem for logical first order formulas with respect to combinations of background theories such as. Grammarbased blackbox input fuzzing proved to be e. A familiarity with the basic idea of smt solvers would be useful. The main idea of the original fuzzing approach is to test programs with random inputs in order to detect security bugs, e. Effectively, the sum tota l of knowledge possessed by. It teaches the basics of how program behavior is encoded in smt formulas more precisely, quantifier free theory of bitvectors no theory of arrays separation logic content in a one day. In this paper, we present an automatic approach for generating test cases that reveal soundness errors in the implementations of.
Code issues 1 pull requests 0 actions projects 0 security insights. Smt solvers for software security george nosenko, security researcher at digital security. The program is then monitored for exceptions such as crashes, failing builtin code assertions, or potential memory leaks. The project aims at helping programmers reason about software bugs in large scale projects, which can be extremely hard to debug due to their high complexity. Now this is more work to use, because the operator needs to define the grammar. Citeseerx a fuzzing and deltadebugging smt solvers. Randomly fuzz modify a wellformed input grammarbased fuzzing. The first one, all enabled smt, will call successively every enabled smt solver configurations. More specifically, they synthesize valid branch reachability properties using concrete. Earlier this summer beans attended the weeklong smt solver summer school held at mit campus in boston, mass. Whitebox fuzzing smt solvers for software security usenix woot12. An smt solver will then return a satisfying assignm ent, if one exists, such as b 0 in this case.
On this page you find a partial list of software provided by fmv. In this case, the fuzzer takes a legal input provided by the operator and mutates it, using that as an input instead. Fuzzing is a powerful testing technique which is typically used in the domains of software security and quality assurance 28,29. This summer, i worked with professor mayur naik on concise bug explanation using smt solver. Fuzzing and deltadebugging smt solvers proceedings of the. Fuzzing is an automated technique widely used to provide software quality assurance during testing to find flaws and bugs by providing random or invalid inputs to a computer software. A solved sudoku puzzle can be expressed mathematically, very close to the three rules of sudoku. Due to the pathexplosion prob lem and dependence on smt solvers, symbolic execution may also not. Smt solvers are widely used as core engines in many applications. We describe the opensource tool dreal, an smt solver for nonlinear formulas over the reals. Clicking on this button will show the list of all available smt solver configurations.
Fuzzing has been used to test all kinds of software including sat solvers 10. While writing this series of posts rolf rolles posted a great videoblog entry on the topic of input crafting using an smt solver. Satisfiability modulo theories smt solvers that support quantifier instantiations via matching triggers can be programmed to give practical support for userdefined theories. Georgy nosenko an introduction to the use smt solvers. Fuzz testing techniques were already applied by software engineers around. Fuzzing and deltadebugging smt solvers proceedings of. Constraint solver based on coverageguided fuzzing mcimperialjfs. Fuzzing and deltadebugging smt solvers institute for formal.
The software running on your pc has been affected by sage. An introduction to smt solvers johannes kanig inria, lri, proval team 2 juin 2010 adacore. Fuzzing and deltadebugging smt solvers robert brummayer and armin biere institute for formal models and veri cation johannes kepler university linz, austria abstract. Each element of a subgrid must be unique in that subgrid.