Senior LevelWeb Security & Cyber Defense
How does Coverage-Guided Fuzzing (AFL++, libFuzzer) discover memory corruption bugs in native code?
❓ Interview Prompt: Explain Coverage-Guided Fuzzing, AFL++, libFuzzer, compile-time code coverage instrumentation, input mutation engines, and crash triaging.
Coverage-Guided Fuzzing (AFL++, libFuzzer) is an automated testing technique that feeds millions of mutated inputs into compiled native programs (C/C++, Rust, Go) to uncover hidden memory bugs:
Fuzzing Mechanics:
1
Compile-Time Instrumentation: Instruments binary code to measure branch coverage.
2
Evolutionary Mutation: Fuzzer mutates input bytes (bit flips, integer overflows). If a mutation hits new code branches, it is added to the corpus.
3
Crash Detection: Automatically saves input payloads that trigger AddressSanitizer (ASan) crashes or segmentation faults!
Code Implementation Example
c
// Target function instrumented for libFuzzer
int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
// Pass mutated input bytes into target parser function
parse_custom_image_header(Data, Size);
return 0;
}💡Writing a libFuzzer fuzz target function in C.
🎯 Interview Key Takeaway
Use coverage-guided fuzzers (AFL++, libFuzzer) in CI/CD to uncover memory corruption bugs in native code components.
#Fuzzing#AFL++#libFuzzer#Senior
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