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    dart symbolic execution

    REPORT N 8189 December 2012 Project-Team Dart A Generic Framework for Symbolic Execution Andrei Arusoaie, Dorel Lucanu, Vlad Rusu. Expose 120. Their work extended DART for data structures. symbolic execution such as DART verifier and KLEE verifier. DART [10] com- bines concrete and symbolic execution to collect the . DART: Directed Automated Random Testing Koushik Sen University of Illinois Urbana-Champaign Joint work with Patrice Godefroid and Nils Klarlund. Foundation: DART (Directed Automated Random Testing) 2. A Generic Approach to Symbolic Execution Andrei Arusoaie, Dorel Lucanu, Vlad Rusu To cite this version: . CUTE: A Concolic Unit Testing Engine for C - Sen et. 11 DART Approach main(){int t1 = randomInt(); int t2 = randomInt(); _ Strlen becomes a symbolic input that can represent any integer Prune redundant paths Large-Scale Application inPractice Mostly based on these papers: DART: directed automated random testing , Godefroid et al., PLDI'05 KLEE: Unassisted and Automatic Generation of High-Coverage Tests for Complex Systems Programs , Cadar et al., OSDI'08 al. Negate the last path condition not already negated in order to visit a new execution path. Static symbolic execution Simulate execution on program source code Computes strongest post-conditions from entry point Dynamic symbolic execution (DSE) Run / interpret the program with concrete state Symbolic state computed in parallel ("concolic") Solver generates new concrete state DSE-Flavors Challenges and Variations 8:01. Symbolic execution maintains a symbolic state , which maps variables to symbolic expressions, and a symbol- DART, Latest, CUTE, jCUTE, Jalangi. RESEARCH CENTRE LILLE - NORD EUROPE Parc scientique de la Haute-Borne 40 avenue Halley - Bt A . Let path = l 0!e 1 l 1!e 2 l 2:::!e n l n be the sequence of events executed under test input . The approach of \symbolic execution" was originally outlined byKing[19]andwasrecentlyappliedbytheEXE,DART,andCUTEprojects[8, 17,34] to nd bugs in C programs. Supports Yices and Boolector. This is done in both GodeFroid Dart [3] and Bitblaze. Concrete and symbolic execution Concrete execution Symbolic execution Original program interleaved with gathering of symbolic constraints Dynamic symbolic execution Pioneered by Godefroid et al: Dart [PLDI'05], Cadar et al [SPIN'05] Why it is great What kind of software engineering problems it may be useful for How it works Example problems and solutions (tools) Each tool implemented on top of a dynamic symbolic execution engine

    Three types of fuzzer based on how much knowledge of the program under test they exploit. Uses CVC4. Dart VM has two execution modes where we hide or mangle symbolic information associated with the program: Obfuscated AOT produces stack traces which look like normal Dart stack traces, but with original names replaced by meaningless combinations of letters. al. execute the program with symbolic valued inputs (goal: good path coverage) represents equivalence class of inputswith first order logic formulas (path constraints) one path constraint abstractly represent all inputs that induces the program execution to go down a specific path solve the path constraint to obtain one representative input that The dynamic symbolic execution engine is decomposed into three dierent components: a symbolic decision engine (DSE), a concolic executor (SPouT), and a SMT solver backend allow- ing meta-strategy solving of SMT problems (JConstraints). A path condition is a formula over symbolic expres- sions. pare DART with other related work in Section 5 and conclude with Section 6. Concolic execution can be distributed. The following illustration shows the flowchart of the while loop . 2. Summary of Symbolic Execution for Bug Finding Augment a program with appropriate assertions Symbolically execute a path Create formula representing path constraint and assertion failure Solve constraints with a solver A satisfying assignment, if found, is an input triggering a bug Cadar & K. Sen, Symbolic Execution for Software Testing: Three . DART Overview DART's integration of random testing and dynamic test generation using symbolic reasoning is best intuitively explained with an ex-ample. Following is the syntax for the while loop. Used in the DART verifier. Symbolic Execution of Alloy Models Junaid Haroon Siddiqui and Sarfraz Khurshid The University of Texas at Austin Abstract. Our basic symbolic execution system cannot track symbolic constraints across RPC between multiple processes, so we will focus on using symbolic execution on a non-privilege-separated Zoobar site. Basic Symbolic Execution 14:17. Preliminary experiments with CESE show that the combination achieves better coverage than both pure enumerative test generation and pure directed symbolic test generation, in orders of magnitude less time . Pre-/post- condition summaries Lazy Test Generation ^The technique first explores, using dynamic symbolic execution, an abstraction of the function under test by replacing each called function with an unconstrained input. SAGE extends systematic dynamic test generation (introduced in DART) to handle large applications and is optimized for long symbolic executions at the x86 binary level. 15}. 2. The program Supports multiple constraint solvers using JConstraints. Execution Symbolic Execution t1=36 t1=m concrete state symbolic state constraints. One very good way to do this is the record actual execution paths during program execution. The idea is to drive symbolic execution along recorded concrete execution paths and so avoid the call to the solver to know if a path is unreachable. Concolic execution Also called dynamic symbolic execution Instrument the program to do symbolic execution as the program runs I.e., shadow concrete program state with symbolic variables Explore one path at a time, start to nish Always have a concrete underlying value to rely on 29 greybox fuzzing. C.

    The while loop executes the instructions each time the condition specified evaluates to true. DART: Directed Automated Random Testing - Godefroid et. symbolic testing (symbolic execution) [PLDI'05, FSE'05, FASE'06, CAV'06,ISSTA'07, ICSE'07] "Nightly/daily building and smoke testing" have become widespread since they often reveal bugs early in the software development process . - Symbolic execution - Collect constraints on inputs - Negate those, solve with constraint solver, generate new inputs - do "systematic dynamic test generation" (=DART) Whitebox Fuzzing = "DART meets Fuzz" Two Parts: 1. Dart Programming - while Loop. Symbolic execution [57] is a program analysis technique that executes a pro-gram on symbolic, instead of concrete, input values and computes the e ects .

    Abstract JDart performs dynamic symbolic execution of Java programs: it executes programs with concrete inputs while recording symbolic constraints on executed program paths. Since 2008, SAGE has found many new expensive security bugs in many Windows applications.

    Summary of Symbolic Execution for Bug Finding Augment a program with appropriate assertions Symbolically execute a path Create formula representing path constraint and assertion failure Solve constraints with a solver A satisfying assignment, if found, is an input triggering a bug A reliable tool has to correctly implement both execution types. Two main sources of bottlenecks for dynamic symbolic execution are path ex- '05] 25 . When we apply dynamic symbolic execution to repOk, we obtain a complete symbolic representation . Symbolic execution has seen signicant interest in the last few years, across a large number of computer science areas, such as software engineering, systems and security, among many others. Use a constraint solverto nd solutions. Give a list of constraintsthat any acceptable solution must satisfy. DART: directed automated random testing. Introducing Symbolic Execution 10:52. Find centralized, trusted content and collaborate around the technologies you use most. Start off the execution with a random input . 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 state maps variables to symbolic values. '06]vs. DART [Godefroidet al. Their approach, called concolic testing, analyzes a program by choosing an initial set of concrete input values V to a given program. Symbolic Execution: A Little History 3:05. Dynamic Symbolic Execution (DSE) for automated test generation consists of instrumenting and running a program while collecting path constraint on inputs from predicates encountered in branch instructions, and of deriving new inputs from the previous path constraint by an SMT (Satisfiability Modulo Theories) solver in order to steer next executions toward new . First, certain queries to the SMT solver can be slow to practi- Program is simultaneously executed with concrete and symbolic inputs . Learn more Following is the syntax for the while loop. They both use a emulated environment for non-symbolic execution (to track actual execution paths) which . Concretization of symbolic variables is an important aspect of modern symbolic executors for the . . blackbox fuzzing. A sufx of is a subsequence i = l i! e . For supporting big real-world programs, more aggressive pruning of execution paths must be done. 1 1 Modern Symbolic Execution: DART, EGT, CUTE, jCUTE, EXE, KLEE, CREST, CATG Koushik Sen EECS Department University of California, Berkeley CristianCadar Department of Computing Imperial College London 2 Today, QA is mostly testing "50% of my company employees are testers, and the rest spends 50% of their time testing!" Bill Gates 1995 3 DART maintains a symbolic memory Sthat maps memory ad- dresses to expressions. In a case where this isn't good enough and the constraint solver isn't enough, DART falls back to concrete execution (the dynamic analysis piece) to determine actual . Symbolic execution has two main limitations.

    mentations of symbolic execution: DART [16], CUTE [35] USENIX Association 29th USENIX Security Symposium 181. and EXE [6] instrument the program under test at the level of C source code. Initially, Sis a mapping that maps each 1W edo this to simplify the xposition; left-hand sides could be made symbolic as well. [13] in their work on CUTE, a concolic unit test engine for C language. . Foundation: DART (Directed Automated Random Testing) 2. In practice, DART typically achieves much better coverage than pure random testing (see [GKS05]).

    In practice, DART typically achieves much better coverage than pure random testing (see [GKS05]). However, the scalability of symbolic execution is often limited by path explosion, i.e., the number of symbolic states representing the paths under exploration quickly explodes as execution goes on. Additionally, when a conditional . al. a key goal of symbolic execution in the context of soft- ware testing is to explore as many different program paths as possible in a given amount of time, and for each path to (1) generate a set of concrete input values exercising that path, and (2) check for the presence of various kinds of errors including assertion violations, uncaught - Dynamic symbolic execution - Collect constraints on inputs - Negate those, solve with constraint solver, generate new inputs - do "systematic dynamic test generation" (=DART) Whitebox Fuzzing = "DART meets Fuzz" Two Parts: 1. In other words, the loop evaluates the condition before the block of code is executed. ACM 1976] Analysis of programs with unspecied inputs -Execute a program on symbolic inputs Symbolic states represent sets of concrete states For each path, build a path condition -Condition on inputs - for the execution to follow that path JDart performs dynamic symbolic execution of Java pro- grams: it executes programs with concrete inputs while recording sym- bolicconstraintsonexecutedprogrampaths.Aconstraintsolveristhen usedforgeneratingnewconcretevaluesfromrecordedconstraintsthat drive execution along previously unexplored paths. JDart - Dynamic symbolic execution tool built on Java PathFinder. Introduction1.1. EXE 27 Symbolic program state . This paper presents the basics of the symbolic execution approach and studies the common tools which utilize symbolic execution in them. functions) Goals I Detect errors I Check corner cases I Provide high code coverage (e.g.path coverage)

    Dynamic Symbolic Execution (DSE) for automated test generation consists of instrumenting and running a program while collecting path constraint on inputs from predicates encountered in branch instructions, and of deriving new inputs from the previous path constraint by an SMT (Satisfiability Modulo Theories) solver in order to steer next executions toward new . Used in the KLEE verifier. . EXE 26 . 1.

    Symbolic Execution for Software Testing: Three Decades Later - Cadar and Sen A Few Billion Lines of Code Later Using Static Analysis to Find Bugs in the Real World - Engler et. Classic symbolic execution 5 Execute the program on symbolic values. Path condition is a quantier-free formula over Concolic. Directed Search: Summary Dynamic test generation to direct executions along alternative program paths collect symbolic constraints at branch points (whenever possible) negate one constraint at a branch point to take other branch (say b) call constraint solver with new path constraint to generate new test inputs next execution driven by these new test inputs to take alternative concrete and symbolic execution was coined by Sen et al. The goal is to eventually cause every if-statement to be executed both ways. Coveraged measured internally ("internal coverage") The first option is to simply rely on the coverage reported by KLEE. '05] Many successful tools EXE = KLEE (Imperial), SPF (NASA), Cloud9, S2E (EPFL) Interview with Andy Chou 32:31. original dynamic symbolic execution papers on DART [1], CUTE [3], or KLEE [6]. '06] vs. DART [Godefroid et al. EXE 28 Symbolic program state Concrete state . 1. The intention is to visit deep into the program execution tree .

    execution implementations: SAGE (Microsoft), CREST 2. In other words, the loop evaluates the condition before the block of code is executed. Implement the core concolic execution logic in concolic_test() in symex/fuzzy.py to get concolic execution working. a symbolic execution, the program memory and output values are represented by symbolic expressions over the symbolic input values. 1. DART: Directed Automated Random Testing Patrice Godefroid, Nils Klarlund, Koushik Sen Presented by: Geri Grolinger Instructor: Professor Azadeh Farzan. Due to several practical applications, improving the per-formance of symbolic execution can have a big impact. 2 Symbolic Execution Semantics A symbolic state (or symbolic environment) q is a map from program variables to symbolic expressions. 2To simplify thepresentation, we assume that M~0is same for all executions of P. Symbolic Execution King [Comm. While it was rather impractical . The execution of the instrumented version behaves just like the original, ex-cept that it also creates a symbolic representation of the program execution state. ClassicalSymbolic Execution 2.Challengesof Symbolic Execution 3.ConcolicTesting 4. It primarily uses symbolic execution (a form of static analysis) to investigate the function, which means that no concrete values are present except for literals in the code. Symbolic Execution Systems 8:26. Symbolically re-execute the program on the trace, generating a set of symbolic constraints (including path conditions). most recent commit 6 months ago. If there is no such path condition, the algorithm terminates. Instead of describing the steps required to reach a solution, describe the solution. Akey observation from [GKS05]is thatimprecisioninsymbolic execution can be alleviated using concrete values and randomiza-tion: whenever symbolic execution does not know how to generate a constraint for a program statement depending on some inputs, Cadar et al, Symbolic Execution for Software Testing in Practice -a Preliminary Assessment _, ICSE 2011. The approach was pioneered by EGT [6] and DART [22]. 2.1 An Introduction to DART Consider the function h in the le below: int f(int x) {return 2 * x;} int h(int x . A Dynamic Symbolic Execution (DSE) engine for JavaScript. ing DART [26], KLEE [10], and SAGE [27]. coverage guided such as EFS, Randoop, AFL, VUzzer. A constraint solver is. Symbolic execution 4 1976: A system to generate test data and symbolically . Flow Analysis: Scaling it up to a Complete Language and Problem Set 11:40. dynamic symbolic execution . DART [13], dynamic symbolic execution can try to explore all the paths within a program to provide a degree of completeness to the analysis. & Symbolic Execution E.g., SAGE, Pex, CUTE, DART. A key observation from [GKS05] is that imprecision in symbolic execution can be alleviated using concrete values and randomiza-tion: whenever symbolic execution does not know how to generate a constraint for a program statement depending on some . whitebox fuzzing. In this case, coverage is measured at the level at which the symbolic execution tool operates in KLEE's case, in terms of LLVM .

    One of the key ingredients of modern symbolic execution techniques is mixed concrete-symbolic execution [5], [18]. Background. Symbolic Execution as Search, and the Rise of Solvers 12:45. A concrete execution of a deterministic sequential program is fully determined by the test input. taint analysis that determines dependencies of branches on particular parts of input. Dynamic symbolic execution (DSE) Run / interpret the program with concrete state Symbolic state computed in parallel ("concolic") Solver generates new concrete state DSE-Flavors EXE-style [Cadaret al. Introduction1.1. The goal of symbolic execution is to generate such a set of inputs so that all the feasible execution paths (or as many as possible in a given time bud-get) can be explored exactly once by running the program on those inputs. In symbolic execution, inputs to a program are treated as symbolic values. Symbolic Execution 3 Concolic Testing DART 4 Summary Marco Probst Concolic Testing 5 / 22. GDart is an ensemble of tools allowing dynamic symbolic execution of JVM programs. Directed Search: Summary Dynamic test generation to direct executions along alternative program paths collect symbolic constraints at branch points (whenever possible) negate one constraint at a branch point to take other branch (say b) call constraint solver with new path constraint to generate new test inputs next execution driven by these new test inputs to take alternative Symbolic execution is a powerful technique that can generate tests steering program execution into desired paths. DART: Directed Automated . We present a new tool, named DART, for automatically testing software that combines three main techniques: (1) automated extraction of the interface of a program with its external environment using static source-code parsing; (2) automatic generation of a test driver for this interface that performs random testing to simulate the most general . A game-changing technique to address this problem is Dynamic Symbolic Execution (DSE), the combination of symbolic and concrete execution, introduced by [DART]. CATG - Concolic execution tool that uses ASM for instrumentation. Symbolic execution is a formal method where the program or design under test is solved with the help of a Satisability Modulo Theory (SMT) solver, in terms of its . Outline Motivation Symbolic Execution Techniques EGT Concolic Testing Challenges Path Explosion EXE-style [Cadar et al. Symbolic execution engines DART [25] and CUTE [43] represent some of the earliest modern attempts to mix concrete and symbolic execution [12]. In comparison with our approach . DART and CUTE: Concolic Testing Koushik Sen University of California, Berkeley Joint work with Gul Agha, Patrice Godefroid, Nils Klarlund, Rupak Majumdar, Darko Marinov . . Symbolic execution - Wikipedia; King, James C. "Symbolic execution and program testing." 1976 (pdf) DART: Directed Automated Random Testing; CUTE: A Concolic Unit Testing Engine for C; Jeff Foster, "Symbolic Execution," 2011 (pdf) -

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