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Posted on Mar 15

Smart Contract Security Audit Checklist: A Developer Guide

#solidity #security #blockchain #web3

Why Smart Contract Security Matters

Smart contracts handle billions of dollars in value. A single vulnerability can lead to catastrophic losses. This checklist helps developers audit their smart contracts before deployment.

Common Vulnerability Categories

1. Reentrancy Attacks

The most famous vulnerability, responsible for the DAO hack.

// VULNERABLE
function withdraw(uint amount) external {
    require(balances[msg.sender] >= amount);
    (bool success, ) = msg.sender.call{value: amount}("");
    require(success);
    balances[msg.sender] -= amount; // Updated AFTER external call
}

// SECURE
function withdraw(uint amount) external {
    require(balances[msg.sender] >= amount);
    balances[msg.sender] -= amount; // Updated BEFORE external call
    (bool success, ) = msg.sender.call{value: amount}("");
    require(success);
}

2. Integer Overflow/Underflow

Always use SafeMath or Solidity 0.8+ built-in checks.

3. Access Control Issues

// Proper access control
modifier onlyOwner() {
    require(msg.sender == owner, "Not authorized");
    _;
}

function setFee(uint newFee) external onlyOwner {
    require(newFee <= MAX_FEE, "Fee too high");
    fee = newFee;
}

4. Front-Running

Transactions in the mempool can be observed and exploited. Mitigations include commit-reveal schemes and using private mempools.

5. Oracle Manipulation

Always use decentralized oracles (Chainlink) and implement TWAP for price feeds.

Audit Checklist

[ ] All external calls use checks-effects-interactions pattern
[ ] No unbounded loops in functions
[ ] Access controls on all admin functions
[ ] Events emitted for all state changes
[ ] No hardcoded addresses
[ ] Proper use of require() and revert()
[ ] Gas optimization reviewed
[ ] Emergency pause mechanism implemented
[ ] Upgrade mechanism properly secured
[ ] No delegate call to untrusted contracts

Testing Strategy

describe("Security Tests", () => {
  it("should prevent reentrancy", async () => {
    const attacker = await Attacker.deploy(target.address);
    await expect(
      attacker.attack({ value: ethers.parseEther("1") })
    ).to.be.reverted;
  });

  it("should enforce access control", async () => {
    await expect(
      contract.connect(nonOwner).setFee(100)
    ).to.be.revertedWith("Not authorized");
  });
});

Recommended Tools

Slither: Static analysis
Mythril: Symbolic execution
Foundry: Fast testing framework
Echidna: Property-based fuzzing

Staying Updated

Security in blockchain evolves rapidly. Stay informed about the latest vulnerabilities and best practices through resources like BTC66.me, which covers blockchain security news and analysis.

Conclusion

Smart contract security is not optional — it is a fundamental requirement. Use this checklist as a starting point, and always consider professional audits for contracts handling significant value.

For more blockchain development resources and crypto market insights, visit btc66.me.

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