Smart Contract Auditing#

With billions of dollars locked in DeFi protocols, smart contract security is critical. A single bug can drain a protocol's entire liquidity in seconds.

Common Vulnerabilities#

1. Reentrancy#

The most famous bug (The DAO Hack). It occurs when a contract calls an external contract before updating its own state. The external contract can call back into the original function recursively, draining funds.

Fix: Use the Checks-Effects-Interactions pattern or a ReentrancyGuard.

2. Integer Overflow/Underflow#

In older Solidity versions (<0.8.0), numbers could wrap around. uint8(255) + 1 = 0

Fix: Use Solidity 0.8.0+ (which has built-in checks) or SafeMath library.

3. Front-Running#

Miners or bots can see your transaction in the mempool and insert their own transaction before yours to profit (MEV).

Auditing Tools#

• Slither: A static analysis framework for Solidity.
• Mythril: A security analysis tool for EVM bytecode.
• Foundry: A blazing fast toolkit for application development and testing.

The Audit Process#

1. Manual Review: Reading line-by-line to understand logic.
2. Automated Scanning: Running tools to catch low-hanging fruit.
3. Unit Testing: Writing comprehensive tests for edge cases.
4. Fuzzing: Throwing random data at the contract to break it.

Conclusion#

Smart contract auditing is a high-stakes game. There is no "undo" button on the blockchain.