The Intelligent Fuzzing in TTCN-3

1. The Intelligent Fuzzing in TTCN-3 Xu Luo, Wu Ji, Liu Chao Software Engineering Institute Beihang University http://www.sei.buaa.edu.cn

2. Outline • Background • Fuzzing in TTCN-3 • Summary

3. Outline • Background • Definition of Fuzzing • Fuzzer Types • Fuzzing in TTCN-3 • Summary

4. Definition • Fuzzing — • A highly automated testing technique that covers numerous boundary cases using invalid data (from files, network protocols, API calls, and other targets) as application input to better ensure the absence of exploitable vulnerabilities. • From modem applications’ tendency to fail due to random input caused by line noise on “fuzzy” telephone lines.

5. Simple Fuzz Example • SUT: Fake Clear Text Protocol [Client] -> "user jared\r\n" "user OK. Provide pass.\r\n" <- [Server] [Client] -> "pass mylamepasswd\r\n" "Login successful. Proceed.\r\n" <-[Server] [Client] -> "list file 1\r\n" ...

6. Simple Fuzz Example (cont.) • Test case 1 [Client] -> "us<50000 \xff's>er jared\r\n" • Test case 2 [Client] -> "user ja<12 %n's>red\r\n" • Test case 3 [Client] -> "user jared\r\n" "user OK. Provide pass.\r\n" <- [Server] [Client] -> "\x04\x98\xbb\x...\r\n"

7. Fuzzer Classification • Generation Method • Generation • Mutation • Knowledge of Inputs • Random • Intelligent • Scope of SUT • Specialized Fuzzer • Generic Fuzzer

8. Intelligent vs. Generic • The contradiction between … • Intelligent Needs the knowledge of SUT • Generic Independent of a specific SUT • How to resolve the contradiction TTCN-3

9. Outline • Background • Fuzzing in TTCN-3 • Our Purpose • Architecture • Details • Summary

10. Our Purpose • Develop a Generic Fuzzer • Based on TTCN-3 • Using the Knowledge of the Input Format —Intelligent • Applying Data Mutation Approach —Mutation

12. Capture Valid Input • Input: • TTCN-3 ATS • Output: • TTCN-3 Value • With its syntax • Purpose: • Instance of Valid Input As seed to generate Invalid Inputs • Syntax Information Needed by the Intelligent mutation

13. Capture Valid Input (cont.) • How to capture Insert the capture code btw. TE & CD Valid Input CD Req CD Prv TE Capture CD: encode

14. Intelligent Mutation • Input: • TTCN-3 value With its syntax • Mutation Strategy • Output: • <Field, Mutation Operator>s • Purpose: • Generate Mutation Operators One mutation operator → One field

15. Intelligent Mutation (cont.) • How to mutate (intelligently) • Type-Sensitive Mutation • Choose mutation operators according to the type of the data being mutated • Attack Heuristics • Design mutation operators according to the stored invalid inputs that have previously been known to expose software vulnerabilities

16. Attack Heuristics • Buffer Overflow [Client] -> "us<50000 \xff's>er jared\r\n" • Format String Attack [Client] -> "user ja<12 %n's>red\r\n" • Inserting Special Characters [Client] -> "user ja<1342 \x00's>red\r\n" • Integer Overflow 0x00, 0x0000, 0x00000000 0xFF, 0xFFFF, 0xFFFFFFFF • ……

17. Type-Sensitive Mutation • Supported TTCN-3 Types • Basic Types • BOOLEAN • Reverse • INTEGER • Boundary, Integer Overflow, ++, -- • CHARSTRING，OCTETSTRING • Null, Buffer Overflow, Format String Attack • ……

18. Type-Sensitive Mutation (cont.) • Supported TTCN-3 Types • Structured Types • RECORD，SET • Remove optional fields • RECORD_OF，SET_OF • Remove elements, • Duplicate elements, • Change the order of elements • ENUMERATED • Choose other value • ……

19. Inject Invalid Inputs • Input: • Test cases • Valid Inputs • Output: • Invalid Inputs • Procedure: • Applying mutation operator to generate invalid input from the instance of the valid input • The invalid input will be sent to SUT

20. Inject Invalid Inputs (cont.) • How to inject Insert the injection code btw. TE & CD Mutation Operator CD Req CD Prv TE Inject CD: encode

21. Test Verdict • The problem • The response of SUT can’t be predicted when an invalid input is injected • The solution • Each time an invalid input is injected, followed with a positive test case that is defined in conformance or functional test suite

22. Test Verdict (cont.) • Each test case includes 3 parts: • Inject an invalid input • Cancel current transaction (if needed) Don’t care the response of SUT • Execute a positive test case Determine if a failure has occurred

23. Evaluation • SUT • Implementations of SIP • Three popular softphones: • Linphone 1.7.1 with libosip2 2.2.2 • SJphone For windows XPsp2, 1.65.377a • X-Lite 2.0, Win32-1103m-14262

24. The Number of Test Cases • How many TCs have been generated • Focusing on INVITE • Based on the ETSI standardized SIP conformance test suite • 429 test cases has been generated

25. Results • Linphone • 3 test cases caused crashes • …via.viaBody.0.viaParams.0.paramValue • …fromField…userOrTelephoneSubscriber • …fromField…hostPort.host • SJphone • 1 test case caused crash • …contentLength.len • X-Lite • No crash • One line has not been released

26. Outline • Background • Fuzzing in TTCN-3 • Summary

27. Summary • How TTCN-3 resolves the contradiction between Intelligent & Generic • TTCN-3 conformance or functional test suite specifies the syntax structure of the valid inputs, which can be used by our fuzzer —Intelligent • The syntax structure definitions are independent of the message encoding rules, the mutation operators could work on the syntax level instead of bit level —Generic

28. Thanks!