Building Secure Contracts

What Is This?

Overview

Trail of Bits' Building Secure Contracts is a comprehensive security toolkit designed to help developers identify, analyze, and remediate vulnerabilities in smart contracts across multiple blockchain platforms. The toolkit bundles together static analysis tools, fuzzing frameworks, and formal verification utilities into a unified workflow that integrates directly into development pipelines. It provides structured guidance alongside automated tooling to enforce security best practices from the earliest stages of contract development.

The toolkit centers on several well-known open-source tools maintained by Trail of Bits, including Slither for static analysis, Echidna for property-based fuzzing, and Medusa for coverage-guided fuzzing. These tools work together to surface issues that manual code review often misses, such as reentrancy vulnerabilities, integer overflows, access control flaws, and unsafe delegatecall patterns. The framework supports Ethereum, Binance Smart Chain, Avalanche, Polygon, Optimism, and Arbitrum, making it relevant across the most widely deployed smart contract ecosystems.

Beyond automated scanning, the toolkit includes a curated set of security properties, testing templates, and educational resources that guide developers through writing verifiable security invariants. This combination of tooling and structured learning makes it suitable for both security auditors conducting formal reviews and developers building contracts from scratch.

Who Should Use This

• Smart contract developers building DeFi protocols, NFT platforms, or DAO governance systems who want to catch vulnerabilities before deployment
• Security auditors and penetration testers who need systematic tooling to supplement manual code review during client engagements
• Blockchain protocol teams integrating continuous security testing into their CI/CD pipelines
• Solidity and Vyper developers transitioning from traditional software development who need structured guidance on blockchain-specific attack surfaces
• DevSecOps engineers responsible for establishing security gates in Web3 development workflows
• Researchers and academics studying smart contract vulnerability classes across multiple EVM-compatible chains

Why Use It?

Problems It Solves

• Manual code review alone cannot reliably detect all vulnerability patterns in complex contract interactions, especially across inheritance hierarchies and external call chains
• Developers lack consistent tooling to write and enforce security invariants that hold across all possible execution paths
• Security testing is often deferred to late-stage audits, making remediation expensive and time-consuming
• Cross-chain deployments introduce chain-specific risks that generic tools do not account for
• Teams struggle to maintain security posture as contracts evolve and new features are added over time

Core Highlights

• Static analysis via Slither detects over 90 vulnerability detectors covering common and advanced Solidity patterns
• Echidna enables property-based fuzzing to test that user-defined invariants hold under adversarial input conditions
• Medusa provides coverage-guided fuzzing with improved corpus management for deeper code path exploration
• Supports six EVM-compatible blockchains with chain-specific configuration options
• Includes pre-built security property templates for common contract patterns such as ERC20, ERC721, and access control
• Integrates with Hardhat, Foundry, and Truffle development environments
• Provides structured educational content alongside tooling to build developer security knowledge

How to Use It?

Basic Usage

Install Slither using pip and run a basic analysis against a Solidity project:

pip install slither-analyzer
slither . --solc-remaps @openzeppelin=node_modules/@openzeppelin

To run Echidna against a contract with a defined invariant:

echidna-test contracts/Token.sol --contract TokenTest --config echidna.yaml

A simple Echidna property in Solidity looks like this:

function echidna_balance_invariant() public view returns (bool) {
    return totalSupply() >= balanceOf(address(this));
}

Specific Scenarios

Scenario 1: Pre-deployment audit preparation. Run Slither with the --print human-summary flag to generate a structured report before submitting a contract for external audit. This surfaces low-hanging issues and reduces audit scope.

Scenario 2: Continuous integration security gate. Add Slither to a GitHub Actions workflow to block pull requests that introduce new high-severity findings, enforcing security standards across the development team.

Real-World Examples

A DeFi lending protocol team used Echidna to define invariants around collateral ratios, discovering an edge case where a flash loan interaction could temporarily violate solvency constraints before the fix was deployed to mainnet.

A security auditor used Slither's inheritance graph printer to map complex proxy upgrade patterns in a governance contract, identifying an uninitialized storage slot that could be exploited post-upgrade.

Important Notes

Requirements

• Python 3.8 or higher is required for Slither installation
• Echidna and Medusa require a compatible Solidity compiler version matching the target contracts
• Node.js and a supported package manager are needed when integrating with Hardhat or Truffle projects