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ruzzy

Fuzz pure Ruby code and Ruby C extensions with coverage-guided libFuzzer instrumentation.

Updated Mar 22, 2026
Search Tags:#security testing#ruby#fuzzing#coverage-guided#addresssanitizer#libfuzzer#c extensions
One-click install
npx skills add https://github.com/TECH-HY/SKILLS --skill ruzzy-tech-hy
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: ruzzy
Source: https://github.com/TECH-HY/SKILLS/tree/main/skills/ruzzy
Command: npx skills add https://github.com/TECH-HY/SKILLS --skill ruzzy-tech-hy

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve? Ruby lacks production-ready coverage-guided fuzzing tools, making it hard to detect memory corruption, undefined behavior, and crashes in Ruby applications and native C extensions before they reach production. ## Core Features & Use Cases - Pure Ruby Fuzzing: Uses a tracer-and-harness script pattern to apply coverage-guided fuzzing to pure Ruby code. - C Extension Fuzzing: Fuzzes Ruby gems with native extensions compiled with AddressSanitizer and UndefinedBehaviorSanitizer flags to detect heap overflows, use-after-free, and undefined behavior. - libFuzzer Integration: Passes all standard libFuzzer options (corpus directories, max_len, timeout) and supports crash reproduction from saved artifacts. - Use Case: Fuzz the msgpack gem by compiling it with sanitizer flags, writing a harness that calls MessagePack.unpack on fuzzer input, and running it under LD_PRELOAD with ASan to surface memory corruption bugs. ## Quick Start Install the ruzzy gem with clang, set the ASAN_OPTIONS environment variable, and run a fuzzing harness with LD_PRELOAD pointing to Ruzzy's ASan library.

Frequently Asked Questions about ruzzy

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I fuzz Ruby code with Ruzzy?▼

Fuzzing pure Ruby code requires two scripts: a tracer script that calls Ruzzy.trace with your harness path, and a harness script defining a test_one_input lambda passed to Ruzzy.fuzz. Run the tracer with LD_PRELOAD set to Ruzzy's ASan library path.

How do I fuzz Ruby C extensions for memory corruption?▼

Compile the gem with clang using -fsanitize=address,fuzzer-no-link flags, then write a single harness that calls the extension's API inside a lambda and rescues Ruby exceptions. Run it with LD_PRELOAD pointing to Ruzzy::ASAN_PATH to detect heap overflows and use-after-free.

Does Ruzzy work on macOS or Windows?▼

Ruzzy supports only Linux x86-64 and AArch64/ARM64 natively. For macOS or Windows, use the official Dockerfile or development environment provided in the Ruzzy GitHub repository.

Why does Ruzzy show memory leak warnings from the Ruby interpreter?▼

The Ruby interpreter itself leaks memory, which AddressSanitizer reports as noise. Set ASAN_OPTIONS with detect_leaks=0, along with allocator_may_return_null=1 and use_sigaltstack=0, before running any fuzzing campaign.

How do I reproduce a crash found by Ruzzy?▼

Pass the saved crash artifact file as an argument to your harness command, for example ruby harness.rb ./crash-<hash>, with the same LD_PRELOAD and ASAN_OPTIONS settings. The fuzzer re-runs that single input to reproduce the crash.

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