What security considerations should I keep in mind when developing smart contracts for Sei EVM? – Sei

While Sei's EVM implementation is compatible with Ethereum, there are Sei-specific security considerations alongside standard EVM security practices you should follow. This guide covers both to help you build secure dApps on Sei.

Sei-Specific Security Considerations

Parallel Execution Awareness

Sei's parallel transaction processing can introduce potential edge cases:

Transaction Ordering: Don't assume transactions will be executed in a specific order, as parallel execution may reorder them within the same block.
Block Information: Be cautious with block-level information like block.timestamp and block.number in critical logic, as transactions executing in parallel access the same values.
Flash Loan Protection: Design your contracts to be resistant to flash loan attacks, which could exploit parallel execution to manipulate markets.

Precompile Security

When using Sei's precompiled contracts:

Input Validation: Always validate inputs before passing them to precompiles.
Address Association: For precompiles requiring address association, verify association status before critical operations.
Permission Control: Implement proper access controls around precompile calls, especially those handling assets or performing sensitive operations.

Cross-Environment Considerations

With Sei's dual native/EVM environment:

Bridge Safety: When using the native-to-EVM bridge, implement additional verification for high-value transfers.
Address Format Validation: Verify address formats when accepting native Sei addresses as inputs to avoid misdirected funds.

General EVM Security Best Practices

Access Control

// ❌ Insecure: No access control
function withdrawFunds() external {
    payable(msg.sender).transfer(address(this).balance);
}

// ✅ Secure: Proper access control
address public owner;

constructor() {
    owner = msg.sender;
}

modifier onlyOwner() {
    require(msg.sender == owner, "Not owner");
    _;
}

function withdrawFunds() external onlyOwner {
    payable(owner).transfer(address(this).balance);
}

Role-Based Access: Consider implementing role-based access using libraries like OpenZeppelin's AccessControl.
Multi-Signature: For high-value contracts, implement multi-signature requirements for critical operations.
Time Locks: Add time delays for sensitive operations, allowing monitoring and intervention if necessary.

Reentrancy Protection

// ❌ Vulnerable to reentrancy
function withdraw(uint amount) external {
    require(balances[msg.sender] >= amount, "Insufficient balance");
    (bool success, ) = msg.sender.call{value: amount}("");
    require(success, "Transfer failed");
    balances[msg.sender] -= amount; // State change after external call
}

// ✅ Protected against reentrancy
bool private locked;

modifier nonReentrant() {
    require(!locked, "Reentrant call");
    locked = true;
    _;
    locked = false;
}

function withdraw(uint amount) external nonReentrant {
    require(balances[msg.sender] >= amount, "Insufficient balance");
    balances[msg.sender] -= amount; // State change before external call
    (bool success, ) = msg.sender.call{value: amount}("");
    require(success, "Transfer failed");
}

Check-Effects-Interactions Pattern: Always apply state changes before making external calls.
Reentrancy Guards: Use nonReentrant modifiers from trusted libraries like OpenZeppelin.

Integer Overflow/Underflow

// ❌ Vulnerable to overflow/underflow (pre-Solidity 0.8.x)
function transfer(address to, uint256 amount) external {
    require(balances[msg.sender] >= amount, "Insufficient balance");
    balances[msg.sender] -= amount;
    balances[to] += amount; // Could overflow
}

// ✅ Safe with Solidity 0.8.x built-in checks
// Or use SafeMath for earlier versions

Use Recent Solidity Version: Solidity 0.8.x includes built-in overflow/underflow checks.
SafeMath: For older Solidity versions, use SafeMath library.
Unchecked Operations: Only use unchecked blocks when you've verified overflow is impossible.

External Calls

// ❌ Unsafe external call
function unsafeCall(address target, bytes memory data) external {
    (bool success, ) = target.call(data);
    // Missing success check
}

// ✅ Safe external call
function safeCall(address target, bytes memory data) external {
    (bool success, bytes memory returnData) = target.call(data);
    require(success, "External call failed");
    // Additionally validate returnData if needed
}

Always Check Return Values: Verify the success of external calls.
Avoid Assuming Call Success: Implement proper error handling for failed calls.
Validate External Contract Addresses: Verify addresses before making calls.

Front-Running Protection

Commit-Reveal Schemes: For operations sensitive to transaction ordering.
Minimum/Maximum Acceptable Values: Include parameters to specify acceptable slippage.
Timeouts: Implement expiration timestamps for pending operations.

Gas Considerations

Avoid Unbounded Operations: Functions shouldn't depend on unbounded data structures.
Gas Limits: Be aware of block gas limits when designing operations that might process large datasets.

Testing & Verification

Comprehensive Testing

Unit Tests: Test individual components with libraries like Hardhat's testing framework.
Integration Tests: Test contract interactions to ensure they work together properly.
Fuzz Testing: Use tools like Echidna to find edge cases through randomized inputs.

Security Audits

Internal Reviews: Have team members review each other's code.
External Audits: Consider professional audits for high-value contracts.
Bug Bounties: Implement bug bounty programs to incentivize security findings.

Deployment Practices

Upgradeability Considerations

// Example using OpenZeppelin's upgradeable contracts
contract MyUpgradeableContract is Initializable, UUPSUpgradeable {
    function initialize() public initializer {
        // Initialization code instead of constructor
    }

    function _authorizeUpgrade(address) internal override onlyOwner {}
}

Transparent vs UUPS: Choose an upgradeability pattern appropriate for your needs.
Initialization: Ensure proper initialization of upgradeable contracts.
Storage Layout: Be cautious with storage layout changes in upgrades.

Emergency Preparedness

Circuit Breakers: Implement pause functionality for critical operations.
Recovery Mechanisms: Plan for potential security incidents.
Key Management: Use proper key management practices for admin/owner accounts.

Sei Testnet Usage

Test Thoroughly on Testnet: Always test on Sei testnet before mainnet deployment.
Simulate Mainnet Conditions: Test with realistic conditions similar to expected mainnet usage.
Verify Precompile Behavior: Ensure precompiles behave as expected in your specific use case.

Common Vulnerabilities Checklist

[ ] Reentrancy vulnerabilities
[ ] Access control issues
[ ] Integer overflows/underflows (pre-Solidity 0.8.x)
[ ] Unchecked external calls
[ ] Front-running vulnerabilities
[ ] Logic errors in business rules
[ ] Dependency vulnerabilities
[ ] Gas-related issues
[ ] Oracle manipulation vulnerabilities
[ ] Flash loan attack vectors