Solverbased debuggers solverbased type systems solverbased concurrency bug. Detecting critical bugs in smt solversusing blackbox mutational. Z3 is a new and efficient smt solver freely available from microsoft research. It is used in several program analysis, verification, and test case generation projects at microsoft and was awarded the 2015 acm sigplan programming languages software award, which is given for software systems that have had a lasting influence. Detecting critical bugs in smt solvers using blackbox mutational fuzzing. Current testing techniques used by developers of smt solvers do not satisfy the high demand for correct and robust. Examples of theories typically used in computer science are the theory of real numbers, the theory of integers, and the theories of various data. Stateoftheart testing techniques for smt solvers do not reliably detect such errors. Since 2008, sage has been running in production for over 1,000 machineyears, automatically fuzzing hundreds of applications. This chapter covers some of these areas where smt solvers have been used. Casp and smt formalisms, which is the main theoretical contribution of the thesis. Nov 19, 20 smt solvers for software security array operations in smt lib 2.
Satisfiability modulo theories smt solvers are fundamental tools in the broad context of software engineering and security research. The tool can handle various nonlinear real functions such as polynomials, trigonometric. Microsoft launches cloud fuzzing service i programmer. To this end, we present a reinforcement learning driven fuzzing system banditfuzz that zeroes in on the grammatical constructs of wellformed solver inputs that are the root cause of performance or correctness issues in solversundertest.
In the process, sage found many new security vulnerabilities missed by blackbox fuzzing and static program analysis and. Boolector is an smt solver for the theory of bitvectors and the extensional theory of arrays over bitvectors. A familiarity with the basic idea of smt solvers would be useful. Fuzzing and deltadebugging smt solvers proceedings of the. In this case, the fuzzer takes a legal input provided by the operator and mutates it, using that as an input instead. Fuzzing 16 generates formulas that may crash the solvers or reveal performance issues, but do not reliably detect soundness problems. We describe the opensource tool dreal, an smt solver for nonlinear formulas over the reals. Full verification of smt solvers, however, is difficult due to their complex nature and still an open question. A fuzzer for string smt solvers uwspace university. Fuzzing has been used to test all kinds of software including sat solvers 10. Z3 is a satisfiability modulo theories smt solver that integrates several decision procedures.
Im looking at doing some verification work where ive got regular tree grammars as an underlying theory. And store a i v returns a new array identical to a, but on position i it contains the value v. Results of running 8 solvers on the example why3 programs with a timeout value of 10 seconds. In proceedings of the 27th acm joint european software engineer. The advantage of smt is that many things that are obvious in smt can take a long time for an equivalent sat solver to rediscover. Satisfiability modulo theories smt problem is a decision problem for logical first order formulas with respect to combinations of background theories such as. Successful commercial computer systems contain tens of millions of lines of handwritten software, all of which is subject to change as competitive pressures motivate the addition of new features in each release. Smt solvers are useful both for verification, proving the correctness of programs, software testing based on symbolic execution, and for synthesis, generating program fragments by searching over the space of possible programs. Pdf smt solvers for software security researchgate.
Detecting critical bugs in smt solvers using blackbox mutational. So lets use a smt solver z3 for example to express a solved sudoku puzzle and to solve it actually. Satisfiability modulo theories smt solvers have made tremendous progress over the last decade 25 and now underpin many im portant software engineering. Typically, fuzzers are used to test programs that take structured inputs. It is not directed at experts but at potential users and developers of. Solving fp constraints using coverageguided fuzzing esecfse 19, august 26s30, 2019, tallinn, estonia listing 1. Again, i would say that for a first version you should get pretty far with an external integration where you let the smt solver deal with propositional sat and uninterpreted functions and arithmetic if you need this. 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.
Clarke carnegie mellon university, pittsburgh, pa 152 abstract. It is not directed at experts but at potential users and developers of smt solvers. The software running on your pc has been affected by sage. Smt solvers perform great once the problem domain has been defined. Btor format 8, the smtlib format 26 distinguishes b etw een type b o ole an and bitve ctor of bitwidth one. Computeraided verification of computer programs often uses smt solvers. Our sat solver precosat won three medals in the sat competition 2009.
This is the largest computational usage ever for any smt solver, with over 4 billion constraints processed to date. To the best of our knowledge, banditfuzz is the first machinelearning based fuzzer for smt solvers. Floatingpoint arithmetic is an essential ingredient of embedded systems, such as in the avionics and automotive industries. 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. As with many other successful applications of smt solvers, there is a focus on reducing the number of queries that most be made. Fuzzing or fuzz testing is an automated software testing technique that involves providing invalid, unexpected, or random data as inputs to a computer program. Vulnerability checking exploit generation copy protection analysis overall workflow.
Fuzzing is a powerful testing technique which is typically used in the domains of software security and quality. To improve this situation, we propose to complement traditional testing techniques with grammarbased blackbox fuzz testing, combined with deltadebugging. Contribute to ppmxsudoku solver development by creating an account on github. Smt solvers are widely used as core engines in many applications. Theories smt problem with string contraints, which is a type of constraint. G and try to derive a contradiction i assume the inequality a 0 i register thelemma. Earlier this summer beans attended the weeklong smt solver summer school held at mit campus in boston, mass. The casp solver ezsmt, the main software product of this work, is inspired by earlier solvers of this kind including systems clingcon gebser et al. There are different ways that fuzzing tools generate inputs to pass to the target program. Fuzzing and deltadebugging smt solvers institute for formal. T ry to pip e cat devurandom to an arbitrary smt solver. Btor format 8, the smt lib format 26 distinguishes b etw een type b o ole an and bitve ctor of bitwidth one.
Smtracker is a matlabbased graphical user interface gui for automatically quantifying, visualising and managing smt data via five interactive panels, allowing the user to interactively explore tracking data from several conditions, movies and cells on a trackby track basis. Such legal inputs might be human produced or automated, for example from a grammar or smt solver query. However, systems are usually designed and modeled at a higher level than the boolean level and the translation to boolean logic can be expensive. It won first places in the prestigious bitvector and bitvector with arrays tracks in the smt competition. To improve this situation, we propose to complement traditional testing techniques with grammarbased blackbox. For example, if an smt solver concludes unsat although the input. Detecting critical bugs in smt solversusing blackbox. A brief introduction to fuzzing and why its an important. Fuzzing for smt solvers kyle dewey, mehmet emre, ben hardekopf.
Tools and algorithms for the construction and analysis of systems 4963 budapest, april 2008, 337340. This can be used as an argument to z3 or other smt solvers. Smt solver as a small part of an larger set of algorithms. The concolic execution technique for python programs used in this chapter was pioneered by. Verification back ends such as smt solvers are typically highly complex pieces of software with performance, correctness and robustness as key requirements. Predicting smt solver performance for software veri.
A crashing smt solver may lead to a crash of the application, or even worse, an incorrect solver may lead to wrong results. 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. They focus on testing controlflow reachability properties of programs. Therefore, robustness and correctness are essential criteria. An example conjunction of loatingpoint constraints in the smtlibv2.
Fuzzing and deltadebugging smt solvers software testing. The program is then monitored for exceptions such as crashes, failing builtin code assertions, or potential memory leaks. It is not a comprehensive survey, but a basic and rigorous introduction to some of the key ideas. By design, such avoidance limits the extent to which the smt solver is able to apply the. An smt solver for nonlinear theories over the reals. Solving floatingpoint constraints using coverageguided fuzzing. Several of our applications are in the context of the z3 smt solver available from microsoft research. Many applications use satis ability modulo theories smt solvers as core decision engines. Hack, art, and science, which presents an overview of the main automated testing techniques in use today for finding security vulnerabilities in software fuzzing means automatic test generation and execution with the goal of finding security. Grammarbased blackbox input fuzzing proved to be effective to uncover bugs in smt solvers but is entirely inputbased and. Inspired by the utility of fuzzers, we introduce stringfuzz and. Dec 18, 2010 smt solvers are widely used as core engines in many applications. For example, smt solvers are used to generate test cases, to nd bugs 5,11,12,30,31, and to verify systems 2,6,19,20,21,23.
Care must be taken to avoid socalled matching loops, which may prevent termination of the solver. Satsmt solvers and applications university of waterloo. Whitebox fuzzing for security testing sage has had a remarkable impact at microsoft. Effectively, the sum tota l of knowledge possessed by. Diffusion parameters and motion behaviour is analysed by several methods. Fuzzing and deltadebugging smt solvers robert brummayer and armin biere institute for formal models and veri. Expression select a i returns the value stored at position i of the array a. All satisfiable constraints are mapped to n new inputs, which are tested and ranked according to incremental instruction coverage. An smt solver will then return a satisfying assignm ent, if one exists, such as b 0 in this case. Smt solvers for software security array operations in smtlib 2. By nature, many of these applications are safetycritical, requiring rigorous mathematical methods such as model checking to verify the adherence to safety standards.
Jan 11, 2012 blackbox fuzzing is a simple yet effective technique for finding security vulnerabilities in software. Z3 lets you define your own stuff with uninterpreted functions, but that doesnt tend to work well any time your decision procedures are recursive. Georgy nosenko an introduction to the use smt solvers for. Fuzzing and deltadebugging smt solvers proceedings of. Introduction fuzzing and symbolic execution often do not achieve high coverage, not only at the source code, binary, or any intermediate code levels but also at the component level. It is used in various software verification and analysis applications. String smt solvers are specialised software tools for solving the satisfiability modulo. Georgy nosenko an introduction to the use smt solvers. Satisfiability modulo theories smt solvers that support quantifier instantiations via matching triggers can be programmed to give practical support for userdefined theories. Theories solvers for software security, in particular for. At microsoft, fuzzing is mandatory for every untrusted interface of every product, as prescribed in the security development lifecycle, 7 which documents recommendations on how to develop. Grammarbased blackbox fuzzing test smt solver with randomsmt formulas for speci. In this paper, the source language used is dafny 19, the ivl is boogie 2 20, and the smt solver is z3 9, but the tactic described is applicable to other program veri.
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