实战例子：Solidity代码小失误导致池子里60万U被盗空

实战例子：Solidity代码小失误导致池子里60万USDT被盗空
被盗原因：利用token的漏洞

查看合约地址
一、先看这笔交易：黑客用0.04个eth换了112个USDT
再用112个USDT换了101个TCR
关键这步：101个TCR换了63.9万USDT(价值400万RMB)，如下图

第1步，点击这里
第2步,点address

第3步，点contract，就可以看合约源码了

/***Submitted for verification at Etherscan.io on 2021-04-13
*/// SPDX-License-Identifier: Unlicense
pragma solidity 0.8.2;// interface need to claim rouge tokens from contract and handle upgraded functions
abstract contract IERC20 {function balanceOf(address owner) public view virtual returns (uint256);function transfer(address to, uint256 amount) public virtual;function allowance(address owner, address spender)publicviewvirtualreturns (uint256);function totalSupply() public view virtual returns (uint256);
}// interface to potential future upgraded contract,
// only essential write functions that need check that this contract is caller
abstract contract IUpgradedToken {function transferByLegacy(address sender,address to,uint256 amount) public virtual returns (bool);function transferFromByLegacy(address sender,address from,address to,uint256 amount) public virtual returns (bool);function approveByLegacy(address sender,address spender,uint256 amount) public virtual;
}//
// The ultimate ERC20 token contract for TecraCoin project
//
contract TcrToken {//// ERC20 basic information//uint8 public constant decimals = 8;string public constant name = "TecraCoin";string public constant symbol = "TCR";uint256 private _totalSupply;uint256 public constant maxSupply = 21000000000000000;string public constant version = "1";uint256 public immutable getChainId;//// other flags, data and constants//address public owner;address public newOwner;bool public paused;bool public deprecated;address public upgradedAddress;bytes32 public immutable DOMAIN_SEPARATOR;// keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");bytes32 public constant PERMIT_TYPEHASH =0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;string private constant ERROR_DAS = "Different array sizes";string private constant ERROR_BTL = "Balance too low";string private constant ERROR_ATL = "Allowance too low";string private constant ERROR_OO = "Only Owner";//// events//event Transfer(address indexed from, address indexed to, uint256 value);event Paused();event Unpaused();event Approval(address indexed owner,address indexed spender,uint256 value);event AddedToBlacklist(address indexed account);event RemovedFromBlacklist(address indexed account);//// data stores//mapping(address => mapping(address => uint256)) private _allowances;mapping(address => uint256) private _balances;mapping(address => bool) public isBlacklisted;mapping(address => bool) public isBlacklistAdmin;mapping(address => bool) public isMinter;mapping(address => bool) public isPauser;mapping(address => uint256) public nonces;//// contract constructor//constructor() {owner = msg.sender;getChainId = block.chainid;// EIP712 DomainDOMAIN_SEPARATOR = keccak256(abi.encode(keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),keccak256(bytes(name)),keccak256(bytes(version)),block.chainid,address(this)));}//// "approve"//function approve(address spender, uint256 amount) external {if (deprecated) {returnIUpgradedToken(upgradedAddress).approveByLegacy(msg.sender,spender,amount);}_approve(msg.sender, spender, amount);}//// "burnable"//function burn(uint256 amount) external {require(_balances[msg.sender] >= amount, ERROR_BTL);_burn(msg.sender, amount);}function burnFrom(address from, uint256 amount) external {require(_allowances[msg.sender][from] >= amount, ERROR_ATL);require(_balances[from] >= amount, ERROR_BTL);_approve(msg.sender, from, _allowances[msg.sender][from] - amount);_burn(from, amount);}//// "transfer"//function transfer(address to, uint256 amount) external returns (bool) {if (deprecated) {returnIUpgradedToken(upgradedAddress).transferByLegacy(msg.sender,to,amount);}require(_balances[msg.sender] >= amount, ERROR_BTL);_transfer(msg.sender, to, amount);return true;}function transferFrom(address from,address to,uint256 amount) external returns (bool) {if (deprecated) {returnIUpgradedToken(upgradedAddress).transferFromByLegacy(msg.sender,from,to,amount);}_allowanceTransfer(msg.sender, from, to, amount);return true;}//// non-ERC20 functionality//// Rouge tokens and ETH withdrawalfunction acquire(address token) external onlyOwner {if (token == address(0)) {payable(owner).transfer(address(this).balance);} else {uint256 amount = IERC20(token).balanceOf(address(this));require(amount > 0, ERROR_BTL);IERC20(token).transfer(owner, amount);}}//// "blacklist"//function addBlacklister(address user) external onlyOwner {isBlacklistAdmin[user] = true;}function removeBlacklister(address user) external onlyOwner {isBlacklistAdmin[user] = false;}modifier onlyBlacklister {require(isBlacklistAdmin[msg.sender], "Not a Blacklister");_;}modifier notOnBlacklist(address user) {require(!isBlacklisted[user], "Address on blacklist");_;}function addBlacklist(address user) external onlyBlacklister {isBlacklisted[user] = true;emit AddedToBlacklist(user);}function removeBlacklist(address user) external onlyBlacklister {isBlacklisted[user] = false;emit RemovedFromBlacklist(user);}function burnBlackFunds(address user) external onlyOwner {require(isBlacklisted[user], "Address not on blacklist");_burn(user, _balances[user]);}//// "bulk transfer"//// transfer to list of address-amountfunction bulkTransfer(address[] calldata to, uint256[] calldata amount)externalreturns (bool){require(to.length == amount.length, ERROR_DAS);for (uint256 i = 0; i < to.length; i++) {require(_balances[msg.sender] >= amount[i], ERROR_BTL);_transfer(msg.sender, to[i], amount[i]);}return true;}// transferFrom to list of address-amountfunction bulkTransferFrom(address from,address[] calldata to,uint256[] calldata amount) external returns (bool) {require(to.length == amount.length, ERROR_DAS);for (uint256 i = 0; i < to.length; i++) {_allowanceTransfer(msg.sender, from, to[i], amount[i]);}return true;}// send same amount to multiple addressesfunction bulkTransfer(address[] calldata to, uint256 amount)externalreturns (bool){require(_balances[msg.sender] >= amount * to.length, ERROR_BTL);for (uint256 i = 0; i < to.length; i++) {_transfer(msg.sender, to[i], amount);}return true;}// send same amount to multiple addresses by allowancefunction bulkTransferFrom(address from,address[] calldata to,uint256 amount) external returns (bool) {require(_balances[from] >= amount * to.length, ERROR_BTL);for (uint256 i = 0; i < to.length; i++) {_allowanceTransfer(msg.sender, from, to[i], amount);}return true;}//// "mint"//modifier onlyMinter {require(isMinter[msg.sender], "Not a Minter");_;}function addMinter(address user) external onlyOwner {isMinter[user] = true;}function removeMinter(address user) external onlyOwner {isMinter[user] = false;}function mint(address to, uint256 amount) external onlyMinter {_balances[to] += amount;_totalSupply += amount;require(_totalSupply < maxSupply, "You can not mine that much");emit Transfer(address(0), to, amount);}//// "ownable"//modifier onlyOwner {require(msg.sender == owner, ERROR_OO);_;}function giveOwnership(address _newOwner) external onlyOwner {newOwner = _newOwner;}function acceptOwnership() external {require(msg.sender == newOwner, ERROR_OO);newOwner = address(0);owner = msg.sender;}//// "pausable"//function addPauser(address user) external onlyOwner {isPauser[user] = true;}function removePauser(address user) external onlyOwner {isPauser[user] = false;}modifier onlyPauser {require(isPauser[msg.sender], "Not a Pauser");_;}modifier notPaused {require(!paused, "Contract is paused");_;}function pause() external onlyPauser notPaused {paused = true;emit Paused();}function unpause() external onlyPauser {require(paused, "Contract not paused");paused = false;emit Unpaused();}//// "permit"// Uniswap integration EIP-2612//function permit(address user,address spender,uint256 value,uint256 deadline,uint8 v,bytes32 r,bytes32 s) external {require(deadline >= block.timestamp, "permit: EXPIRED");bytes32 digest =keccak256(abi.encodePacked("",DOMAIN_SEPARATOR,keccak256(abi.encode(PERMIT_TYPEHASH,user,spender,value,nonces[user]++,deadline))));address recoveredAddress = ecrecover(digest, v, r, s);require(recoveredAddress != address(0) && recoveredAddress == user,"permit: INVALID_SIGNATURE");_approve(user, spender, value);}//// upgrade contract//function upgrade(address token) external onlyOwner {deprecated = true;upgradedAddress = token;}//// ERC20 view functions//function balanceOf(address account) external view returns (uint256) {if (deprecated) {return IERC20(upgradedAddress).balanceOf(account);}return _balances[account];}function allowance(address account, address spender)externalviewreturns (uint256){if (deprecated) {return IERC20(upgradedAddress).allowance(account, spender);}return _allowances[account][spender];}function totalSupply() external view returns (uint256) {if (deprecated) {return IERC20(upgradedAddress).totalSupply();}return _totalSupply;}//// internal functions//function _approve(address account,address spender,uint256 amount) private notOnBlacklist(account) notOnBlacklist(spender) notPaused {_allowances[account][spender] = amount;emit Approval(account, spender, amount);}function _allowanceTransfer(address spender,address from,address to,uint256 amount) private {require(_allowances[from][spender] >= amount, ERROR_ATL);require(_balances[from] >= amount, ERROR_BTL);// exception for Uniswap "approve forever"if (_allowances[from][spender] != type(uint256).max) {_approve(from, spender, _allowances[from][spender] - amount);}_transfer(from, to, amount);}function _burn(address from, uint256 amount) private notPaused {_balances[from] -= amount;_totalSupply -= amount;emit Transfer(from, address(0), amount);}function _transfer(address from,address to,uint256 amount) private notOnBlacklist(from) notOnBlacklist(to) notPaused {require(to != address(0), "Use burn instead");require(from != address(0), "What a Terrible Failure");_balances[from] -= amount;_balances[to] += amount;emit Transfer(from, to, amount);}
}// rav3n_pl was here

部署一个合约，然后在合约里面进行很多交易，然后把USDT转走了

第4步，查看合约创建时间

合约创建300多天了，
但是黑客是Feb-04-2022 10:54:37 AM交易的，说明上线很久，才发行漏洞。

而且合约没有经过安全校验。

二、分析合约代码
在tenderly.co上分析合约操作步骤

让池子里的TCR币突然就燃烧掉很多，池子里的TCR变少了，价格自然变高。所以101个TCR换了
63.9万个USDT
错误代码：
require(_allowances[msg.sender][from] >= amount, ERROR_ATL);
应该是：require(_allowances[from] [msg.sender]>= amount, ERROR_ATL);
写反了，导致任何人都可以燃烧任何人的token

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