Automated Whitebox Fuzz Testing
description
Transcript of Automated Whitebox Fuzz Testing
Automated Whitebox Fuzz Testing
Patrice Godefroid (Microsoft Research)Michael Y. Levin (Microsoft Center for
Software Excellence)David Molnar (UC-Berkeley, visiting MSR)
Fuzz Testing
• An effective technique for finding security vulnerabilities in software• Apply invalid, unexpected, or random data to the inputs of a program.• If the program fails(crashing, access violation
exception), the defects can be noted.
Vulnerability Finding Today
• One Security bug can bring $500-$100,000 on the open market
• Good bug finders make $180-$250/hr consulting• Few companies can find good people, many don’t even
realize this is possible.• Still largely a black art
Whitebox Fuzzing• This paper present an alternative whitebox fuzz testing approach
inspired by recent advances in symbolic execution and dynamic test generation– Run the code with some initial well-formed input
– Collect constraints on input with symbolic execution
– Generate new constraints (by negating constraints one by one)
– Solve constraints with constraint solver
– Synthesize new inputs
Dynamic Test Generationvoid top(char input[4]) { int cnt = 0; if (input[0] == ‘b’) cnt++; if (input[1] == ‘a’) cnt++; if (input[2] == ‘d’) cnt++; if (input[3] == ‘!’) cnt++; if (cnt >= 3) crash();}
input = “good”
• Running the program with random values for the 4 input bytes is unlikely to discovery the error: a probability of about
• Traditional fuzz testing is difficult to generate input values that will drive program through all its possible execution paths.
301/ 2
Depth-First Search
void top(char input[4]) { int cnt = 0; if (input[0] == ‘b’) cnt++; if (input[1] == ‘a’) cnt++; if (input[2] == ‘d’) cnt++; if (input[3] == ‘!’) cnt++; if (cnt >= 3) crash();}
I0 != ‘b’I1 != ‘a’I2 != ‘d’I3 != ‘!’good
I0 != ‘b’
I1 != ‘a’
I2 != ‘d’
I3 != ‘!’
Depth-First Search
goo!good
void top(char input[4]) { int cnt = 0; if (input[0] == ‘b’) cnt++; if (input[1] == ‘a’) cnt++; if (input[2] == ‘d’) cnt++; if (input[3] == ‘!’) cnt++; if (cnt >= 3) crash();}
I0 != ‘b’I1 != ‘a’I2 != ‘d’I3 == ‘!’
Practical limitation
godd
void top(char input[4]) { int cnt = 0; if (input[0] == ‘b’) cnt++; if (input[1] == ‘a’) cnt++; if (input[2] == ‘d’) cnt++; if (input[3] == ‘!’) cnt++; if (cnt >= 3) crash();}
I0 != ‘b’I1 != ‘a’I2 == ‘d’I3 != ‘!’good
Every time only one constraint is expanded, low efficiency!
Generational SearchKey Idea: One Trace, Many Tests
goo!
godd
gaod
bood
“Generation 1” test cases
good
void top(char input[4]) { int cnt = 0; if (input[0] == ‘b’) cnt++; if (input[1] == ‘a’) cnt++; if (input[2] == ‘d’) cnt++; if (input[3] == ‘!’) cnt++; if (cnt >= 3) crash();}
I0 == ‘b’I1 == ‘a’I2 == ‘d’I3 == ‘!’
void top(char input[4]) { int cnt = 0; if (input[0] == ‘b’) cnt++; if (input[1] == ‘a’) cnt++; if (input[2] == ‘d’) cnt++; if (input[3] == ‘!’) cnt++; if (cnt >= 3) crash();}
0good
1goo!
1godd
2god!
1gaod
2gao!
2gadd
gad!
1bood
2boo!
2bodd
2baod
bod! bad!
badd baod
The Generational Search Space
SAGE Architecture(Scalable Automated Guided Execution)
Check forCrashes
(AppVerifier)
Trace Program(Nirvana)
Gather Constraints(Truscan)
SolveConstraints(Disolver)
Input0 Trace File Constraints
Input1Input2
…
InputN
• Since 1st MS internal release in April’07: dozens of new security bugs found (most missed by blackbox fuzzers, static analysis)
• Apps: image processors, media players, file decoders,…
• Many bugs found rated as “security critical, severity 1, priority 1”
• Now used by several teams regularly as part of QA process
Initial Experiences with SAGE
ExperimentsANI Parsing - MS07-017
RIFF...ACONLISTB...INFOINAM....3D Blue Alternate v1.1..IART....................1996..anih$...$...................................rate....................seq ....................LIST....framicon......... ..
RIFF...ACONBB...INFOINAM....3D Blue Alternate v1.1..IART....................1996..anih$...$...................................rate....................seq ....................anih....framicon......... ..
Initial input Crashing test case
ANI Parsing - MS07-017
RIFF...ACONLISTB...INFOINAM....3D Blue Alternate v1.1..IART....................1996..anih$...$...................................rate....................seq ....................LIST....framicon......... ..
RIFF...ACONBB...INFOINAM....3D Blue Alternate v1.1..IART....................1996..anih$...$...................................rate....................seq ....................anih....framicon......... ..
Only 1 in 232 chance at random!
Initial input Crashing test case
Initial input : 341 branch constraints, 1,279,939 total instructions. Crash test cases: 7706 test cases, 7hrs 36 mins
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000040h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 0 – initial input – 100 bytes of “00”
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 00 00 00 00 00 00 00 00 00 00 00 00 ; RIFF............00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000040h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 1
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 00 00 00 00 ** ** ** 20 00 00 00 00 ; RIFF....*** ....00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000040h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 2
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 3D 00 00 00 ** ** ** 20 00 00 00 00 ; RIFF=...*** ....00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000040h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 3
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 3D 00 00 00 ** ** ** 20 00 00 00 00 ; RIFF=...*** ....00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 73 74 72 68 00 00 00 00 00 00 00 00 ; ....strh........00000040h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 4
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 3D 00 00 00 ** ** ** 20 00 00 00 00 ; RIFF=...*** ....00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 73 74 72 68 00 00 00 00 76 69 64 73 ; ....strh....vids00000040h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 5
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 3D 00 00 00 ** ** ** 20 00 00 00 00 ; RIFF=...*** ....00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 73 74 72 68 00 00 00 00 76 69 64 73 ; ....strh....vids00000040h: 00 00 00 00 73 74 72 66 00 00 00 00 00 00 00 00 ; ....strf........00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 6
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 3D 00 00 00 ** ** ** 20 00 00 00 00 ; RIFF=...*** ....00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 73 74 72 68 00 00 00 00 76 69 64 73 ; ....strh....vids00000040h: 00 00 00 00 73 74 72 66 00 00 00 00 28 00 00 00 ; ....strf....(...00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 7
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 3D 00 00 00 ** ** ** 20 00 00 00 00 ; RIFF=...*** ....00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 73 74 72 68 00 00 00 00 76 69 64 73 ; ....strh....vids00000040h: 00 00 00 00 73 74 72 66 00 00 00 00 28 00 00 00 ; ....strf....(...00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 C9 9D E4 4E ; ............ÉäN00000060h: 00 00 00 00 ; ....
Generation 8
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 3D 00 00 00 ** ** ** 20 00 00 00 00 ; RIFF=...*** ....00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 73 74 72 68 00 00 00 00 76 69 64 73 ; ....strh....vids00000040h: 00 00 00 00 73 74 72 66 00 00 00 00 28 00 00 00 ; ....strf....(...00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 9
Zero to Crash in 10 Generations
• Starting with 100 zero bytes …
• SAGE generates a crashing test:
00000000h: 52 49 46 46 3D 00 00 00 ** ** ** 20 00 00 00 00 ; RIFF=...*** ....00000010h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................00000030h: 00 00 00 00 73 74 72 68 00 00 00 00 76 69 64 73 ; ....strh....vids00000040h: 00 00 00 00 73 74 72 66 B2 75 76 3A 28 00 00 00 ; ....strf²uv:(...00000050h: 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 ; ................00000060h: 00 00 00 00 ; ....
Generation 10 – bug ID 1212954973!
Found after only 3 generations starting from “well-formed” seed file
Different Crashes From Different Initial Input Files 100
zerobytes
1867196225 X X X X X2031962117 X X X X X612334691 X X1061959981 X X1212954973 X X1011628381 X X X842674295 X1246509355 X X X1527393075 X1277839407 X1951025690 X
Media 1: 60 machine-hours, 44,598 total tests, 357 crashes, 12 bugs
Bug ID seed1 seed2 seed3 seed4 seed5 seed6 seed7
Most Bugs Found are “Shallow”
1 2 3 4 5 6 70
0.5
1
1.5
2
2.5
3
3.5
# Unique First-Found Bugs
Generation
Conclusion Blackbox vs. Whitebox Fuzzing
• Cost/precision tradeoffs
– Blackbox is lightweight, easy and fast, but poor coverage
– Whitebox is smarter, but complex and slower
– Recent “semi-whitebox” approaches• Less smart but more lightweight: Flayer (taint-flow analysis, may
generate false alarms), Bunny-the-fuzzer (taint-flow, source-based, heuristics to fuzz based on input usage), autodafe, etc.
• Which is more effective at finding bugs? It depends…
– Many apps are so buggy, any form of fuzzing finds bugs!
– Once low-hanging bugs are gone, fuzzing must become smarter: use whitebox and/or user-provided guidance (grammars, etc.)
• Bottom-line: in practice, use both!
Thank you!Questions?