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167 lines
5.0 KiB
Markdown
167 lines
5.0 KiB
Markdown
---
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name: defi-amm-security
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description: Solidity AMM 合约、流动性池和交换流程的安全检查清单。涵盖重入、CEI 排序、捐赠或通胀攻击、预言机操纵、滑点、管理员控制和整数数学。
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origin: ECC direct-port adaptation
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version: "1.0.0"
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---
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# DeFi AMM 安全
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Solidity AMM 合约、LP 金库和交换函数的关键漏洞模式及强化实现。
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## 适用场景
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* 编写或审计 Solidity AMM 或流动性池合约
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* 实现持有代币余额的交换、存款、提款、铸造或销毁流程
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* 审查任何在份额或储备金计算中使用 `token.balanceOf(address(this))` 的合约
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* 向 DeFi 协议添加费用设置器、暂停器、预言机更新或其他管理功能
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## 工作原理
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将其作为检查清单加模式库使用。对照以下类别审查每个用户入口点，并优先使用强化示例而非自行编写的变体。
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## 执行安全
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本技能中的 shell 命令是本地审计示例。仅在受信任的代码检出或一次性沙箱中运行，不要将不受信任的合约名称、路径、RPC URL、私钥或用户提供的标志拼接到 shell 命令中。在安装工具或运行可能消耗大量本地或付费资源的长时间模糊测试/静态分析任务前，请先询问。
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切勿在命令示例、日志或报告中包含机密信息、私钥、助记词、API 令牌或主网签名凭证。
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## 示例
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### 重入攻击：强制遵循 CEI 顺序
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存在漏洞：
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```solidity
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function withdraw(uint256 amount) external {
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require(balances[msg.sender] >= amount);
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token.transfer(msg.sender, amount);
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balances[msg.sender] -= amount;
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}
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```
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安全：
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```solidity
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import {ReentrancyGuard} from "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
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import {SafeERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
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using SafeERC20 for IERC20;
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function withdraw(uint256 amount) external nonReentrant {
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require(balances[msg.sender] >= amount, "Insufficient");
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balances[msg.sender] -= amount;
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token.safeTransfer(msg.sender, amount);
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}
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```
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当存在经过验证的库时，不要自行编写防护措施。
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### 捐赠或通胀攻击
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直接使用 `token.balanceOf(address(this))` 进行份额计算，会让攻击者通过向合约发送代币（绕过预期路径）来操纵分母。
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```solidity
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// Vulnerable
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function deposit(uint256 assets) external returns (uint256 shares) {
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shares = (assets * totalShares) / token.balanceOf(address(this));
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}
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```
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```solidity
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// Safe
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uint256 private _totalAssets;
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function deposit(uint256 assets) external nonReentrant returns (uint256 shares) {
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uint256 balBefore = token.balanceOf(address(this));
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token.safeTransferFrom(msg.sender, address(this), assets);
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uint256 received = token.balanceOf(address(this)) - balBefore;
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shares = totalShares == 0 ? received : (received * totalShares) / _totalAssets;
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_totalAssets += received;
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totalShares += shares;
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}
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```
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跟踪内部会计并衡量实际收到的代币。
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### 预言机操纵
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现货价格可通过闪电贷操纵。优先使用 TWAP。
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```solidity
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uint32[] memory secondsAgos = new uint32[](2);
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secondsAgos[0] = 1800;
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secondsAgos[1] = 0;
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(int56[] memory tickCumulatives,) = IUniswapV3Pool(pool).observe(secondsAgos);
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int24 twapTick = int24(
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(tickCumulatives[1] - tickCumulatives[0]) / int56(uint56(30 minutes))
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);
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uint160 sqrtPriceX96 = TickMath.getSqrtRatioAtTick(twapTick);
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```
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### 滑点保护
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每个交换路径都需要调用者提供的滑点和截止时间。
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```solidity
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function swap(
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uint256 amountIn,
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uint256 amountOutMin,
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uint256 deadline
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) external returns (uint256 amountOut) {
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require(block.timestamp <= deadline, "Expired");
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amountOut = _calculateOut(amountIn);
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require(amountOut >= amountOutMin, "Slippage exceeded");
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_executeSwap(amountIn, amountOut);
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}
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```
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### 安全的储备金计算
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```solidity
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import {FullMath} from "@uniswap/v3-core/contracts/libraries/FullMath.sol";
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uint256 result = FullMath.mulDiv(a, b, c);
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```
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对于大型储备金计算，当存在溢出风险时，避免使用简单的 `a * b / c`。
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### 管理控制
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```solidity
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import {Ownable2Step} from "@openzeppelin/contracts/access/Ownable2Step.sol";
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contract MyAMM is Ownable2Step {
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function setFee(uint256 fee) external onlyOwner { ... }
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function pause() external onlyOwner { ... }
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}
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```
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所有权转移应优先使用显式接受，并对每个特权路径设置门控。
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## 安全检查清单
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* 暴露于重入攻击的入口点使用 `nonReentrant`
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* 遵循 CEI 顺序
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* 份额计算不依赖原始的 `balanceOf(address(this))`
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* ERC-20 转账使用 `SafeERC20`
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* 存款衡量实际收到的代币
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* 预言机读取使用 TWAP 或其他抗操纵源
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* 交换需要 `amountOutMin` 和 `deadline`
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* 对溢出敏感的储备金计算使用安全原语，如 `mulDiv`
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* 管理函数受访问控制
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* 存在紧急暂停功能并经过测试
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* 在生产前运行静态分析和模糊测试
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## 审计工具
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```bash
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pip install slither-analyzer
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slither . --exclude-dependencies
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echidna-test . --contract YourAMM --config echidna.yaml
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forge test --fuzz-runs 10000
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```
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