solidity-security-best-practices

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Solidity Security Best Practices

Solidity智能合约安全最佳实践

When to Apply

适用场景

Reviewing smart contract code for common vulnerabilities.
Implementing critical patterns like Checks-Effects-Interactions.
Auditing access control and upgradeability logic.
Preparing for a security audit or bug bounty.
Debugging unexpected behavior in external contract interactions.

检查智能合约代码中的常见漏洞。
实现Checks-Effects-Interactions（CEI）等关键模式。
审计访问控制与可升级性逻辑。
为安全审计或漏洞赏金活动做准备。
调试外部合约交互中的异常行为。

Critical Security Patterns

核心安全模式

Checks-Effects-Interactions (CEI)

Checks-Effects-Interactions（CEI）模式

Always update state variables before making external calls to prevent reentrancy.

solidity

// BAD
function withdraw(uint amount) public {
    require(balances[msg.sender] >= amount);
    (bool s, ) = msg.sender.call{value: amount}("");
    balances[msg.sender] -= amount;
}

solidity

// GOOD
function withdraw(uint amount) public {
    require(balances[msg.sender] >= amount);
    balances[msg.sender] -= amount;
    (bool s, ) = msg.sender.call{value: amount}("");
    require(s);
}

在进行外部调用前务必先更新状态变量，以防止重入攻击。

solidity

// BAD
function withdraw(uint amount) public {
    require(balances[msg.sender] >= amount);
    (bool s, ) = msg.sender.call{value: amount}("");
    balances[msg.sender] -= amount;
}

solidity

// GOOD
function withdraw(uint amount) public {
    require(balances[msg.sender] >= amount);
    balances[msg.sender] -= amount;
    (bool s, ) = msg.sender.call{value: amount}("");
    require(s);
}

Access Control

访问控制

Restrict sensitive functions to authorized addresses using standard patterns.

solidity

// BAD
function setOwner(address _new) public {
    owner = _new;
}

solidity

// GOOD
function setOwner(address _new) public onlyOwner {
    owner = _new;
}

使用标准模式将敏感函数限制为仅授权地址可调用。

solidity

// BAD
function setOwner(address _new) public {
    owner = _new;
}

solidity

// GOOD
function setOwner(address _new) public onlyOwner {
    owner = _new;
}

Reentrancy Protection

重入防护

Use mutexes to prevent recursive calls into the same function or contract.

solidity

// BAD
function claim() public {
    require(!claimed[msg.sender]);
    msg.sender.call{value: 1 ether}("");
    claimed[msg.sender] = true;
}

solidity

// GOOD
function claim() public nonReentrant {
    require(!claimed[msg.sender]);
    claimed[msg.sender] = true;
    payable(msg.sender).transfer(1 ether);
}

使用互斥锁防止对同一函数或合约的递归调用。

solidity

// BAD
function claim() public {
    require(!claimed[msg.sender]);
    msg.sender.call{value: 1 ether}("");
    claimed[msg.sender] = true;
}

solidity

// GOOD
function claim() public nonReentrant {
    require(!claimed[msg.sender]);
    claimed[msg.sender] = true;
    payable(msg.sender).transfer(1 ether);
}

Safe External Calls

安全外部调用

Handle token transfer failures and validate external contract interactions.

solidity

// BAD
function pay(IERC20 token, uint amount) public {
    token.transfer(msg.sender, amount);
}

solidity

// GOOD
using SafeERC20 for IERC20;
function pay(IERC20 token, uint amount) public {
    token.safeTransfer(msg.sender, amount);
}

处理代币转账失败情况并验证外部合约交互。

solidity

// BAD
function pay(IERC20 token, uint amount) public {
    token.transfer(msg.sender, amount);
}

solidity

// GOOD
using SafeERC20 for IERC20;
function pay(IERC20 token, uint amount) public {
    token.safeTransfer(msg.sender, amount);
}

High Priority Patterns

高优先级模式

Input Validation

输入验证

Sanitize all user-provided data to prevent unexpected state changes.

solidity

// BAD
function setRate(uint _rate) public {
    rate = _rate;
}

solidity

// GOOD
function setRate(uint _rate) public {
    if (_rate == 0) revert InvalidRate();
    rate = _rate;
}

对所有用户提供的数据进行清理，以防止意外的状态变更。

solidity

// BAD
function setRate(uint _rate) public {
    rate = _rate;
}

solidity

// GOOD
function setRate(uint _rate) public {
    if (_rate == 0) revert InvalidRate();
    rate = _rate;
}

Upgrade Safety

升级安全性

Protect implementation contracts and ensure storage compatibility.

solidity

// BAD
contract MyProxy is Initializable {
    uint public x;
    function init(uint _x) public { x = _x; }
}

solidity

// GOOD
contract MyProxy is Initializable {
    uint public x;
    function init(uint _x) public initializer { x = _x; }
}

保护实现合约并确保存储兼容性。

solidity

// BAD
contract MyProxy is Initializable {
    uint public x;
    function init(uint _x) public { x = _x; }
}

solidity

// GOOD
contract MyProxy is Initializable {
    uint public x;
    function init(uint _x) public initializer { x = _x; }
}

Circuit Breakers

断路器机制

Implement emergency stop mechanisms to pause functionality during attacks.

solidity

// BAD
function trade() public {
    _performTrade();
}

solidity

// GOOD
function trade() public whenNotPaused {
    _performTrade();
}

实现紧急停止机制，以便在攻击期间暂停功能。

solidity

// BAD
function trade() public {
    _performTrade();
}

solidity

// GOOD
function trade() public whenNotPaused {
    _performTrade();
}

Medium Priority Patterns

中优先级模式

Signature Security

签名安全

Prevent replay attacks by including nonces and domain separators.

solidity

// BAD
function exec(bytes memory sig) public {
    address signer = recover(sig);
    _doWork(signer);
}

solidity

// GOOD
function exec(bytes memory sig, uint nonce) public {
    require(!used[nonce]);
    used[nonce] = true;
    address signer = recover(sig, nonce);
}

通过包含随机数（nonce）和域分隔符防止重放攻击。

solidity

// BAD
function exec(bytes memory sig) public {
    address signer = recover(sig);
    _doWork(signer);
}

solidity

// GOOD
function exec(bytes memory sig, uint nonce) public {
    require(!used[nonce]);
    used[nonce] = true;
    address signer = recover(sig, nonce);
}

Randomness

随机性实现

Avoid using on-chain data for randomness; use verifiable random functions.

solidity

// BAD
uint rand = uint(keccak256(abi.encodePacked(block.timestamp)));

solidity

// GOOD
// Use Chainlink VRF
uint rand = IVRF(vrf).requestRandomWords();

避免使用链上数据生成随机性；使用可验证随机函数。

solidity

// BAD
uint rand = uint(keccak256(abi.encodePacked(block.timestamp)));

solidity

// GOOD
// Use Chainlink VRF
uint rand = IVRF(vrf).requestRandomWords();

Event Emission

事件触发

Emit events for all significant state changes to facilitate off-chain tracking.

solidity

// BAD
function update(uint _v) public {
    val = _v;
}

solidity

// GOOD
function update(uint _v) public {
    val = _v;
    emit Updated(_v);
}

对所有重要的状态变更触发事件，以便于链下追踪。

solidity

// BAD
function update(uint _v) public {
    val = _v;
}

solidity

// GOOD
function update(uint _v) public {
    val = _v;
    emit Updated(_v);
}

Common Vulnerability Checklist

常见漏洞检查表

Vulnerability Name	SCWE ID	Quick Fix
tx.origin Authentication	SCWE-018	Use msg.sender instead
Unprotected SELFDESTRUCT	SCWE-038	Add access control to selfdestruct
Reentrancy - External Call Before State Update	SCWE-046	Use CEI pattern or ReentrancyGuard
Unchecked External Call Return Value	SCWE-109	Use require() or SafeERC20
Delegatecall Injection	SCWE-132	Validate target address for delegatecall
Integer Overflow/Underflow	SCWE-106	Use Solidity 0.8+ or SafeMath
Default Function Visibility	SCWE-128	Explicitly define visibility
Unencrypted On-Chain Private Data	SCWE-136	Encrypt data or store off-chain
Weak Randomness	SCWE-015	Use Chainlink VRF or commit-reveal
Unprotected Ether Withdrawal	SCWE-029	Add access control to withdrawal
Uninitialized Storage Pointer	SCWE-043	Initialize all storage pointers
Signature Replay Attack	SCWE-020	Use nonces and EIP-712
Hash Collision with abi.encodePacked	SCWE-025	Use abi.encode for dynamic types
DoS with Block Gas Limit	SCWE-031	Avoid loops over unbounded arrays
Floating Pragma	SCWE-058	Lock pragma to a specific version
Front-Running	SCWE-063	Use commit-reveal or slippage protection
Unprotected Initializer	SCWE-053	Use 'initializer' modifier
Incorrect Access Control	SCWE-048	Use OpenZeppelin AccessControl/Ownable
DoS with Unexpected Revert	SCWE-030	Use pull-over-push for payments
Assert Violation	SCWE-067	Use require() for input validation
Lack of Reentrancy Guard	SCWE-077	Add nonReentrant modifier
Forced Ether via Self-Destruct	SCWE-079	Don't rely on address(this).balance
Hardcoded Gas Amount	SCWE-100	Avoid .transfer(), use .call()

漏洞名称	SCWE ID	快速修复方案
tx.origin身份验证	SCWE-018	使用msg.sender替代
未受保护的SELFDESTRUCT	SCWE-038	为selfdestruct添加访问控制
重入攻击 - 外部调用先于状态更新	SCWE-046	使用CEI模式或ReentrancyGuard
未检查外部调用返回值	SCWE-109	使用require()或SafeERC20
Delegatecall注入	SCWE-132	验证delegatecall的目标地址
整数溢出/下溢	SCWE-106	使用Solidity 0.8+版本或SafeMath
默认函数可见性	SCWE-128	显式定义函数可见性
链上未加密私有数据	SCWE-136	加密数据或存储在链下
弱随机性	SCWE-015	使用Chainlink VRF或提交-揭示方案
未受保护的以太币提取	SCWE-029	为提取功能添加访问控制
未初始化的存储指针	SCWE-043	初始化所有存储指针
签名重放攻击	SCWE-020	使用nonce和EIP-712
abi.encodePacked哈希碰撞	SCWE-025	对动态类型使用abi.encode
区块Gas限制导致的DoS	SCWE-031	避免遍历无界数组
浮动版本声明	SCWE-058	将pragma锁定到特定版本
抢先交易（Front-Running）	SCWE-063	使用提交-揭示方案或滑点保护
未受保护的初始化函数	SCWE-053	使用'initializer'修饰符
错误的访问控制	SCWE-048	使用OpenZeppelin AccessControl/Ownable
异常回滚导致的DoS	SCWE-030	采用拉取式而非推送式支付
Assert断言违规	SCWE-067	使用require()进行输入验证
缺少重入防护	SCWE-077	添加nonReentrant修饰符
自毁强制转入以太币	SCWE-079	不要依赖address(this).balance
硬编码Gas值	SCWE-100	避免使用.transfer()，改用.call()

Enhanced with MCP

结合MCP增强功能

If you have the

solidity-agent-toolkit

MCP server configured, these tools provide automated security analysis:

```
run_slither
```
for static analysis
```
match_vulnerability_patterns
```
for heuristic detection
```
check_vulnerability
```
for SCWE pattern matching
```
search_vulnerabilities
```
for OWASP knowledge base lookup

如果你配置了

solidity-agent-toolkit

MCP服务器，这些工具可提供自动化安全分析：

```
run_slither
```
：静态分析
```
match_vulnerability_patterns
```
：启发式检测
```
check_vulnerability
```
：SCWE模式匹配
```
search_vulnerabilities
```
：OWASP知识库查询

References

参考资料

OWASP Smart Contract Top 10 (2026)

OWASP智能合约Top 10（2026版）