During symbolic execution, program state consists of symbolic values for some memory locations. Generalized symbolic execution for model checking and testing sarfraz khurshid1, corina s. As a result, the output values computed by a program are expressed as a function of the input symbolic values. From afar, fuzzing is a dumb, bruteforce method that works surprisingly well, and symbolic execution is. Concrete execution refers to the representation and execution of concrete or real values against a program, where as symbolic execution refers to the representation and execution. For more information on my research, take a look at my publications. Pdf symbolic execution and recent applications to worst. Test inputs are chosen based on whether they can trigger new branching behaviors of the program. Schwartz carnegie mellon university 5000 forbes ave.
Symbolic execution is a software testing technique that is useful to aid the generation of test data and in proving the program quality. By the end of this lab, you will have a symbolic execution system that can take the zoobar web. Mergepoint introduces veritesting, a new technique that employs static symbolic execution to amplify the effect of dynamic symbolic execution. Directly applying an offtheshelf symbolic execution engine on ssltls libraries is, however, not practical due to the problem. Symbolic execution symbolic execution refers to execution of program with symbols as argument. Triton dynamic binary analysis platform that includes a dynamic symbolic execution tool. Enhancing symbolic execution with veritesting proceedings. Symbolic execution and program testing virginia tech.
Basic symbolic execution program analysis coursera. Generalized symbolic execution for model checking and testing. Symbolic execution verification condition generation fsoft ivancic et al. A survey of symbolic execution techniques season lab. Software security introducing symbolic execution youtube. Symbolic execution the symbolic execution of a program is described in this section in an ideal sense, and then, in section 6, a particular practical system which has been built an ap proximation to the ideal is discussed. Klee is a symbolic virtual machine built on top of the llvm compiler infrastructure, and available under the uiuc open source license. All you ever wanted to know about dynamic taint analysis. Bap binary analysis platform provides a framework for writing program analysis tools. Im interested in almost all aspects of computer security, but these days i usually work on static and dynamic binary program analysis, vulnerability discovery e. Symbolic execution can be used for finding bugs in software, where it checks for runtime errors or.
It symbolically represents all inputs for executing the path. Symbolic execution is a popular technique for software. A fundamental problem that arises frequently in quantitative program analysis e. Some insights about symbolic execution i execute programs with symbols. With symbolic execution, the program is executed in an abstracted manner. Selective symbolic execution vitaly chipounov, vlad georgescu, cristian zam. Dawn song path predicates a path predicate encodes the constraints that must be satisfied for a program path to be executed. Symbolic execution and recent applications to worstcase execution, load testing and security analysis chapter pdf available in advances in computers january 2018 with 483 reads. Klee llvm execution engine klee is a symbolic virtual machine built on top of the llvm compiler infrastructure, and available under the uiuc open source license. Symbolic execution is an important software testing approach. Lets describe this process, with the following code fragment. Various means, such as symbolic execution, concolic execution, taint analysis, can be used in binary analysis to help collect control flow information, execution path information, etc. Symbolic execution as empirical studies tool web application security checker enhancement to abstractionbased static analysis program synthesis tool all of these take advantage of sym exec strengths, and try to avoid drawbacks 7. This can be a good way to audit your application for security vulnerabilities so that you can then fix them.
In computer science, symbolic execution also symbolic evaluation or symbex is a means of analyzing a program to determine what inputs cause each part of a program to execute. This is possible because when a symbolic variable, or variables, appear in a conditional scarred expression, there could exist some solutions that would make the guard true, and some solutions that. And expressions involving comparisons, like disequality. Expressions involving arithmetic operators like addition. Many security and software testing applications require checking whether. Bap is a publicly available infrastructure for performing program veri. For example, the core code of our symbolic executor for assembly is only 250 lines long due to the. Systematic comparison of symbolic execution systems acm digital.
An instruction trace is collected using the tracecap plugin in decaf, and then the symbolic execution in bap is used to compute path constraints and generate new inputs for fuzzing. In contrast, few attempts to apply symbolic execution in the context of ivls have been reported 46, 52. Deconstructing dynamic symbolic execution microsoft research. To sum up, our main contributions are listed as follows. The goal of this survey is to provide an overview of the main ideas, challenges, and solutions developed in the area, distilling them for a broad. Accelerating array constraints in symbolic execution. I think symbolic execution can be used in many other interesting ways next. Pasareanu is an associate research professor with cylab at carnegie mellon university, working at the silicon valley campus with nasa ames research center.
This whitebox fuzzing tool based on decaf and bap 1. For more information on what klee is and what it can do, see the osdi 2008 paper. Summary of symbolic execution for bug finding augment a program with appropriate assertions symbolically execute a path create formula representing. Each execution state, labeled with an upper case letter, shows the statement to be executed, the symbolic store. The role of art is not to reproduce visible objects, but to make invisibles visible. Cool fact about bap, theres a really weird but very cool embedded lisp that. An interpreter follows the program, assuming symbolic values for inputs rather than obtaining actual inputs as normal execution of the program would. Selecta formal system for testing and debugging programs by symbolic execution.
She is an acm distinguished scientist, known for her influential research on software model checking, symbolic execution and assumeguarantee compositional verification, using abstraction and learningbased methods. Intuitive understanding of symbolic execution i execute programs with symbols. This paper presents the basics of the symbolic execution approach and studies the common tools which utilize symbolic execution in them. Veritesting allows mergepoint to find twice as many bugs, explore orders of magnitude more paths, and achieve higher code coverage than previous dynamic symbolic execution systems. Unlike concrete execution, where the taken path is determined by the input, in symbolic execution the program can take any feasible path. This lab will introduce you to a powerful technique for finding bugs in software. I concrete execution versus symbolic execution i symbolic execution tree i applications of symbolic execution.
Symbooglix symbolic execution tool for boogie programs. Symbolic execution is an approach at the core of many modern techniques to software testing, automatic program repair, and re verse engineering 6, 10, 20, 22, 25, 27. All you ever wanted to know about dynamic taint analysis and. Symbolic variables represent inputs to the program. A platform for invivo multipath analysis of software systems, chipounov, kuznetsov, candea, asplos 2011. Symbolic execution has been incubated in dozens of tools developed over the past four decades, leading to major practical breakthroughs in a number of prominent software reliability applications. Symbolic execution has become a popular technique for software. Symbolic execution is a program analysis technique introduced in the 70s that has received renewed interest in recent years, due to algorithmic advances and increased availability of computational power and constraint solving technology. Symbolic execution tree of function foobar given in figure 1. Postconditioned symbolic execution qiuping yi12, zijiang yang3, shengjian guo4, chao wang4, jian liu1, chen zhao1 1 national engineering research center for fundamental software, institute of software, beijing, china 2 graduate university, chinese academy of sciences, beijing, china 3 department of computer science, western michigan university, kalamazoo, michigan, usa. A survey of symbolic execution techniques 2018 hacker news.
Say we want to insure that func always returns a valid nonnull pointer. On benchmarking the capability of symbolic execution tools. Symbolic execution and recent applications to worstcase. A system to generate test data and symbolically execute programs, l. Symbolic execution is a popular program analysis technique introduced in the mid 70s to test. Intellitest generates inputs for parameterized unit tests by analyzing the branch conditions in the program. Aug 30, 2016 importantly, we take a build security in mentality, considering techniques at each phase of the development cycle that can be used to strengthen the security of software systems. A curated list of awesome symbolic execution resources including essential research papers, lectures, videos, and tools. We know that symbolic execution for program analysis tends to have trouble. Symbolic execution lecture part of software security course on coursera. A binaryanalysis platform david brumley, ivan jager, thanassis avgerinos, and edward j. Symbolic execution as empirical studies tool web application security checker enhancement to abstractionbased static analysis program synthesis tool all of these take advantage of. Dynamic symbolic execution dse is a wellknown technique for automatically generating tests to achieve higher levels of coverage in a program. While the key idea behind sym bolic execution was introduced more than three decades ago 5, 12, 22, 25, it has only recently been made practi cal, as a result of signi.
Execution symbolic execution hybrid fuzzing figure 1. Dynamic taint analysis and forward symbolic execution but might have been afraid to ask edward j. Software security basic symbolic execution youtube. This paper proposes usage of binary analysis platform bap for symbolic execution and z3 smt solver as smt solving software. Parallel symbolic execution for automated realworld software testing stefan bucur vlad ureche cristian zam. We tackled the harder problem and produced two productionquality bugfinding systems. A binary analysis platform cmu ece carnegie mellon. It provides internal components like a dynamic symbolic execution dse engine, a taint engine, ast representations of the x86 and the x8664 instructions set semantics, smt simplification passes, an smt solver interface and, the last but not least, python bindings. Parallel symbolic execution for automated realworld software testing. The first step in symbolic execution is to generate a control flow graph or cfg. In this article, we survey the main aspects of symbolic execution and discuss the most. Symbolic execution georgia institute of technology. History of symbolic execution as well as satsmt solving, fuzzing, and taint data tracking enzetsymbolic execution. Parallel symbolic execution for automated realworld.
A fuzzer and a symbolic executor walk into a cloud trail. The problem is theoretically as well as practically challenging because. Guodong li, indradeep ghosh software systems innovation group fujitsu laboratories of america. Bound analysis using backward symbolic execution microsoft. Symbolic execution for software testing in practice. Symbolic execution has become an effective program testing technique, providing a way to automatically generate inputs that trigger software errors ranging from lowlevel program crashes to higher. To support symbolic execution, expressions also include symbolic variables. A survey of symbolic execution techniques acm computing. Dynamic symbolic execution visual studio microsoft docs. We propose a new postconditioned symbolic execution method for identifying and eliminating common path suf. License join the chat at binaryanalysisplatformbap docs build status. It provides internal components like a dynamic symbolic execution dse engine, a taint engine, ast representations of the x86 and the x8664 instructions set semantics, smt simplification passes, an. Bap plugins may then be written to use the bil representation of the software. In proceedings of the 23rd international conference on computer aided verification, pages 463469.
Importantly, we take a build security in mentality, considering techniques at each phase of the development cycle that can be used to strengthen the security of software systems. Expressions consist of things like integers n, variables x. The execution requires a selection of paths that are exercised by a set of data values. Whereas a normal execution must take either the true or false branch of a conditional, a symbolic execution could actually take both branches. We observe that symbolic execution, a technique proven to be effective in. Automatic unit test generation and execution for javascript program through symbolic execution hideo tanida, tadahiro uehara software engineering laboratory fujitsu laboratories ltd. If a symbolic execution tool can find test cases to trigger logic bombs, it indicates that the tool can. A survey of symbolic execution techniques acm computing surveys.
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