CosmFuzz

A developer-friendly fuzzing tool for CosmWasm smart contracts that wraps Ziggy and provides automatic harness generation with multi-contract support.

Features

• Multi-contract fuzzing: Fuzz multiple interacting CosmWasm contracts simultaneously
• Harness generation: Discovers invariants and generates fuzzing harness template
• Invariant-driven: Define invariants directly in your contract code using #[cfg(cosmfuzz)] modules

Installation

cargo install --path cosmfuzz

Quick Start

# 1. Initialize in your target
cd my-cosmwasm-contract
cosmfuzz init

# 2. Add invariants and setup function to your contract
# See docs/writing-invariants.md
# See docs/setup-functions.md

# 3. Start fuzzing
cosmfuzz fuzz

# 4. Debug a crash
cosmfuzz run /tmp/cosmfuzz/my-project/output/cosmfuzz/crashes/.../id:000000...

Notes:

• cosmfuzz init runs cargo afl system-config.
• cosmfuzz fuzz patches cosmwasm-std's MockApi::addr_validate to return Ok(Addr::unchecked(input)) for fuzzing.

Documentation

• Writing Invariants - How to define invariants in your contracts
• Configuration - Configuring cosmfuzz-config.toml
• Commands - Complete command reference
• Example Walkthrough - Complete CW20 fuzzing tutorial
• Advanced Usage - Custom harnesses and testing frameworks

Example

See examples/ for a minimal working example.