Occurs when dynamic transaction fees or gas fees increase unexpectedly, eating into the user's transaction value and causing unintended slippage.
Game
During the transaction, the user expects a predictable gas cost. Would you say he can calm down and go eat a sandwich?
// SPDX-License-Identifier: MIT// Open me in VSCode and really think before opening the hints!// Add @audit tags wherever suspicious// Go to the solidity docs to complete missing knowledge of what's happening here// Solve by drafting a fix!pragmasolidity ^0.8.0;interface IDEX {functionswap(address tokenIn,address tokenOut,uint256 amountIn) externalreturns (uint256);}contract GasIncreaseGame { IDEX public dex;addresspublic tokenOut;constructor(address_dex,address_tokenOut) { dex =IDEX(_dex); tokenOut = _tokenOut; }functionexecuteSwap(address tokenIn,uint256 amountIn) public { dex.swap(tokenIn, tokenOut, amountIn); }}
Consider how you might limit the transaction’s gas cost or mitigate the impact of gas-heavy external calls.
Timeouts or gas limit checks might help you detect and prevent excessive gas consumption during the transaction.
functionexecuteSwap(address tokenIn,uint256 amountIn) public {uint256 gasLimit = gasleft() /2; // Fix: Use only a portion of the remaining gas for the external call (bool success,bytesmemory returnData) =address(dex).call{gas: gasLimit}( abi.encodeWithSelector(dex.swap.selector, tokenIn, tokenOut, amountIn) );require(success,"Swap failed or exceeded gas limit");// Decode and validate the resultuint256 amountOut = abi.decode(returnData, (uint256));require(amountOut >0,"Invalid swap output");}