DeFi Saver 用户 31 万 DAI 是如何被盗的？慢雾技术拆解攻击细节

function swapTokenToToken(address_src, address_dest, uint_amount, uint_minPrice, uint_exchangeType, address_exchangeAddress, bytes memory_callData, uint_0xPrice) public payable { // use this to avoid stack too deep error address[3] memory orderAddresses = [_exchangeAddress,_src,_dest]; if (orderAddresses[1] == KYBER_ETH_ADDRESS) { require(msg.value >=_amount, "msg.value smaller than amount"); } else { require(ERC20(orderAddresses[1]).transferFrom(msg.sender, address(this),_amount), "Not able to withdraw wanted amount"); } uint fee = takeFee(_amount, orderAddresses[1]); _amount = sub(_amount, fee); // [tokensReturned, tokensLeft] uint[2] memory tokens; address wrapper; uint price; bool success; // at the beggining tokensLeft equals_amount tokens[1] =_amount; if (_exchangeType == 4) { if (orderAddresses[1] != KYBER_ETH_ADDRESS) { ERC20(orderAddresses[1]).approve(address(ERC20_PROXY_0X),_amount); } (success, tokens[0], ) = takeOrder(orderAddresses,_callData, address(this).balance,_amount); // either it reverts or order doesn't exist anymore, we reverts as it was explicitely asked for this exchange require(success && tokens[0] > 0, "0x transaction failed"); wrapper = address(_exchangeAddress); } if (tokens[0] == 0) { (wrapper, price) = getBestPrice(_amount, orderAddresses[1], orderAddresses[2],_exchangeType); require(price >_minPrice ||_0xPrice >_minPrice, "Slippage hit"); // handle 0x exchange, if equal price, try 0x to use less gas if (_0xPrice >= price) { if (orderAddresses[1] != KYBER_ETH_ADDRESS) { ERC20(orderAddresses[1]).approve(address(ERC20_PROXY_0X),_amount); } (success, tokens[0], tokens[1]) = takeOrder(orderAddresses,_callData, address(this).balance,_amount); // either it reverts or order doesn't exist anymore if (success && tokens[0] > 0) { wrapper = address(_exchangeAddress); emit Swap(orderAddresses[1], orderAddresses[2],_amount, tokens[0], wrapper); } } if (tokens[1] > 0) { // in case 0x swapped just some amount of tokens and returned everything else if (tokens[1] !=_amount) { (wrapper, price) = getBestPrice(tokens[1], orderAddresses[1], orderAddresses[2],_exchangeType); } // in case 0x failed, price on other exchanges still needs to be higher than minPrice require(price >_minPrice, "Slippage hit onchain price"); if (orderAddresses[1] == KYBER_ETH_ADDRESS) { (tokens[0],) = ExchangeInterface(wrapper).swapEtherToToken.value(tokens[1])(tokens[1], orderAddresses[2], uint(-1)); } else { ERC20(orderAddresses[1]).transfer(wrapper, tokens[1]); if (orderAddresses[2] == KYBER_ETH_ADDRESS) { tokens[0] = ExchangeInterface(wrapper).swapTokenToEther(orderAddresses[1], tokens[1], uint(-1)); } else { tokens[0] = ExchangeInterface(wrapper).swapTokenToToken(orderAddresses[1], orderAddresses[2], tokens[1]); } } emit Swap(orderAddresses[1], orderAddresses[2],_amount, tokens[0], wrapper); } } // return whatever is left in contract if (address(this).balance > 0) { msg.sender.transfer(address(this).balance); } // return if there is any tokens left if (orderAddresses[2] != KYBER_ETH_ADDRESS) { if (ERC20(orderAddresses[2]).balanceOf(address(this)) > 0) { ERC20(orderAddresses[2]).transfer(msg.sender, ERC20(orderAddresses[2]).balanceOf(address(this))); } } if (orderAddresses[1] != KYBER_ETH_ADDRESS) { if (ERC20(orderAddresses[1]).balanceOf(address(this)) > 0) { ERC20(orderAddresses[1]).transfer(msg.sender, ERC20(orderAddresses[1]).balanceOf(address(this))); } } } 

function takeOrder(address[3] memory_addresses, bytes memory_data, uint_value, uint_amount) private returns(bool, uint, uint) { bool success; (success, ) =_addresses[0].call.value(_value)(_data); uint tokensLeft =_amount; uint tokensReturned = 0; if (success){ // check how many tokens left from_src if (_addresses[1] == KYBER_ETH_ADDRESS) { tokensLeft = address(this).balance; } else { tokensLeft = ERC20(_addresses[1]).balanceOf(address(this)); } // check how many tokens are returned if (_addresses[2] == KYBER_ETH_ADDRESS) { TokenInterface(WETH_ADDRESS).withdraw(TokenInterface(WETH_ADDRESS).balanceOf(address(this))); tokensReturned = address(this).balance; } else { tokensReturned = ERC20(_addresses[2]).balanceOf(address(this)); } } return (success, tokensReturned, tokensLeft); } 

23b872dd //SlowMist// transferFrom 函数签名 000000000000000000000000c001cd7a 370524209626e28eca6abe6cfc09b0e5 0000000000000000000000005bb456cd 09d85156e182d2c7797eb49a43840187 00000000000000000000000000000000 00000000000041a522386d9b95c00000 //SlowMist// 310000e18