调用 borrow() 借款时,使用的是未从预言机获取新的值,而是过时 exchangeRate 值, 而调用 liquidate() 清算时会从预言机获取新的 exchangeRate 值, 计算产生巨大的价格差异,从中获利.
forge test --contracts "./src/KashiPairMediumRiskV1-exp.sol" -vvv
相关链接:
https://twitter.com/BlockSecTeam/status/1603633067876155393
anyswap 已更名为 Multichain
anyswapRouterV4::anySwapOutUnderlyingWithPermit()
首先对传入的 Token 地址没有校验, 攻击者恶意部署的返回受影响的 Token 核心利用点是 token 不存在 permit() 函数而被调用, 但是存在 fallback , 交给 fallback 处理, 随意传入的 v r s 无从校验,交易不会失败, 而受影响的是前端默认 approve 最大可用数量代币给合约,而不是按需授权数量的授权的用户.
function anySwapOutUnderlyingWithPermit(
address from,
address token,
address to,
uint amount,
uint deadline,
uint8 v,
bytes32 r,
bytes32 s,
uint toChainID
) external {
address _underlying = AnyswapV1ERC20(token).underlying();
IERC20(_underlying).permit(from, address(this), amount, deadline, v, r, s);
TransferHelper.safeTransferFrom(_underlying, from, token, amount);
AnyswapV1ERC20(token).depositVault(amount, from);
_anySwapOut(from, token, to, amount, toChainID);
}因为授权过多代币数量给 anyswapRouterV4 而受影响的代币, 包括最近被利用的 NUM,以及 WETH, WBNB 等, 不存在 permit() 函数但是存在 fallback的代币.
以 WETH 为例子:
forge test --contracts "./src/anyswapRouterV4-exp.sol" -vvv
相关链接:
https://medium.com/zengo/without-permit-multichains-exploit-explained-8417e8c1639b
https://blog.neptunemutual.com/taking-a-closer-look-at-the-numbers-protocol-hack/
ULME Token::buyMiner() public 函数, 可恶意用授权 USDT 的地址, 去兑换 ULME 代币.
攻击步骤:
(1)闪电贷借入 USDT
(2) USDT 兑换成 ULME
(3) 调用 ULME Token contract::buyMiner(), 传入事先收集的授权 USDT 给 ULME Token 合约的地址列表,去购买 ULME 代币,拉高币价
(4) 出售 ULME 获利
function buyMiner(address user,uint256 usdt)public returns (bool){
address[]memory token=new address[](2);
token[0]=_usdt_token;
token[1]=address(this);
usdt=usdt.add(usdt.div(10));
require(IERC20(_usdt_token).transferFrom(user,address(this),usdt), "buyUlm: transferFrom to ulm error");
uint256 time=sale_date;
sale_date=0;
address k=0x25812c28CBC971F7079879a62AaCBC93936784A2;
IUniswapV2Router01(_roter).swapExactTokensForTokens(usdt,1000000,token,k,block.timestamp+60);
IUniswapV2Router01(k).transfer(address(this),address(this),IERC20(address(this)).balanceOf(k));
sale_date=time;
return true;
}
}forge test --contracts "./src/ULME-exp.sol" -vvv
攻击获利: ~ 50,646 BUSD
attack_tx: https://etherscan.io/tx/0xdb9a13bc970b97824e082782e838bdff0b76b30d268f1d66aac507f1d43ff4ed
相关链接:
https://twitter.com/blocksecteam/status/1584839309781135361
https://twitter.com/BeosinAlert/status/1584888021299916801
BondFixedExpiryTeller::redeem() 函数对传入的 token_ 没有校验, 传入攻击者自己部署的地址, 函数内的 expiry()/burn() 函数都走攻击者恶意构造的逻辑保证正常执行，而 underlying() 返回 OHM 地址进行 transfer().
function redeem(ERC20BondToken token_, uint256 amount_) external override nonReentrant {
if (uint48(block.timestamp) < token_.expiry())
revert Teller_TokenNotMatured(token_.expiry());
token_.burn(msg.sender, amount_);
token_.underlying().transfer(msg.sender, amount_);
}forge test --contracts "./src/OlympusDAO-exp.sol" -vvv
攻击获利: ~ 30,437 OHM
attack_tx: https://etherscan.io/tx/0x3ed75df83d907412af874b7998d911fdf990704da87c2b1a8cf95ca5d21504cf
相关链接:
https://twitter.com/Supremacy_CA/status/158342502609464115
https://twitter.com/peckshield/status/1583416829237526528
每次 transfer() 转账都会燃烧池子里 0.1% 的 HEALTH Token,多次调用 transfer() 消耗池子里的 HEALTH Token,最后再交换消耗前闪电贷借入WBNB 换的 HEALTH Token,售出为 WBNB 获利.
function _transfer(address from, address to, uint256 value) private {
//..
uint256 burnValue = _balances[uniswapV2Pair].mul(burnFee).div(1000);
_balances[uniswapV2Pair] = _balances[uniswapV2Pair].sub(burnValue);
_balances[_burnAddress] = _balances[_burnAddress].add(burnValue);
//..
}forge test --contracts "./src/HEALTH-exp.sol" -vvv
攻击获利: ~ 16 WBNB
attack_tx: https://bscscan.com/tx/0xae8ca9dc8258ae32899fe641985739c3fa53ab1f603973ac74b424e165c66ccf
相关链接:
https://twitter.com/BlockSecTeam/status/1583073442433495040
StaxLPStaking 合约 migrateStake() 函数 (1)没有访问控制,任意 EOA 账户或合约可以随意调用,(2) 函数 oldStaking 可以任意传参,传入自己恶意部署的合约地址,凭空获得 LP Token.
function migrateStake(address oldStaking, uint256 amount) external {
StaxLPStaking(oldStaking).migrateWithdraw(msg.sender, amount);
_applyStake(msg.sender, amount);
}forge test --contracts "./src/templedao-exp.sol -vvv
攻击获利: ~ 2 M USDC
attack_tx: https://etherscan.io/tx/0x8c3f442fc6d640a6ff3ea0b12be64f1d4609ea94edd2966f42c01cd9bdcf04b5
Remove liquidity and sale_tx: https://etherscan.io/tx/0x4b119a4f4ba1ad483e9851973719f310527b43f3fcc827b6d52db9f4c1ddb6a2
套利合约闪电贷回调函数 pancakeCall 没有限制仅 Pair 合约可调用.
forge test --contracts "./src/arbitrage_contract-exp.sol" -vvv
攻击获利: ~ 25912 USDT / ~ 327 WBNB / ~ 5160 BUSD / ~ 0.014 BTCB / ~ 0.097 ETH
attack_tx: https://bscscan.com/tx/0xd48758ef48d113b78a09f7b8c7cd663ad79e9965852e872fdfc92234c3e598d2
burn() 函数允许任何人调用燃烧任意地址的代币,导致 LP Pair 合约 $SDT代币被恶意消耗完,用小部分 $SDT 代币就可以掏空池子里的 WBNB.
function burn(address account, uint256 _amount) public {
_transferFrom(account, DEAD, _amount);
emit burnTokens(account, _amount);
}forge test --contracts "./src/shadowfi.sol" -vvv
攻击获利: ~ 1078 WBNB
attack_tx:https://bscscan.com/tx/0xe30dc75253eecec3377e03c532aa41bae1c26909bc8618f21fb83d4330a01018
糟糕的随机源取自链上, 遇到不想要的结果让交易回滚
function publicMint() public payable {
uint256 supply = totalSupply();
require(!pauseMint, "Pause mint");
require(msg.value >= price, "Ether sent is not correct");
require(supply + 1 <= maxTotal, "Exceeds maximum supply");
_safeMint(msg.sender, 1);
bool randLucky = _getRandom();
uint256 tokenId = _totalMinted();
emit NEWLucky(tokenId, randLucky);
tokenId_luckys[tokenId] = lucky;
if(tokenId_luckys[tokenId] == true){
require(payable(msg.sender).send((price * 190) / 100));
require(payable(withdrawAddress).send((price * 10) / 100));}
}
function _getRandom() private returns(bool) {
uint256 random = uint256(keccak256(abi.encodePacked(block.difficulty, block.timestamp)));
uint256 rand = random%2;
if(rand == 0){return lucky = false;}
else {return lucky = true;}
}forge test --contracts "./src/luckytiger-exp.sol.sol" -vvv
攻击获利: 忽略不计
attack_tx: https://etherscan.io/tx/0x804ff3801542bff435a5d733f4d8a93a535d73d0de0f843fd979756a7eab26af
Solidity 0.8 版本以下没有溢出检测，从 QIXI -BNB LP 池子闪电贷借空池子里 BNB,QIXI Token 存在溢出, _Transfer 没有对转账的发送钱包余额检查,任意调用转账时在 _basicTransfer 里下溢获得大量 QIXI Token,闪电贷回调里转 QIXI Token 到 LP 池子,满足 K 值检查,不用偿还 BNB.
function _basicTransfer(address sender, address recipient, uint256 value) internal returns (bool) {
balanceOf[sender] -= value;
balanceOf[recipient] += value;
emit Transfer(sender, recipient, value);
return true;
}forge test --contracts "./src/QIXI-exp.sol" -vvv
攻击获利: ~ 6 WBNB
attack_tx: https://bscscan.com/tx/0x16be4fe1c8fcab578fcb999cbc40885ba0d4ba9f3782a67bd215fb56dc579062