[Ekaterina Kulikova]

ZkSynk Building a custom paymaster Smart Contract | Деплой смарт контракта ЗкСинк*

Требования к серверу:

• 2/4/50 - минимальные

Также нам понадобится:
- кошелек метамаск с ETH Goerli
- Тестовая сеть zksynk era testnet (можно подключить тут)
- Тестовые токенамы ETH в сети zksynk (кран тут)
- Приватный ключ от метамаска (не используйте кошельки с ральными деньгами!)
- RPC ETH1 goerli (можно взять на инфуре)

Подготавливаем сервер:

sudo apt-get update -y && sudo apt upgrade -y && sudo apt-get install make build-essential unzip lz4 gcc git jq chrony -y

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.1/install.sh | bash

source ~/.bashrc

nvm -v

nvm install v16.16.0

node -v
#вывод - v16.16.0

corepack enable 

corepack prepare [email protected] --activate

mkdir custom-paymaster-tutorial && cd custom-paymaster-tutorial

yarn init -y

yarn add -D typescript ts-node ethers@^5.7.2 zksync-web3 @ethersproject/web @ethersproject/hash hardhat @matterlabs/hardhat-zksync-solc @matterlabs/hardhat-zksync-deploy @matterlabs/zksync-contracts @openzeppelin/contracts

mkdir contracts deploy

nano hardhat.config.ts
#вставляем:

import { HardhatUserConfig } from "hardhat/config";

import "@matterlabs/hardhat-zksync-deploy";
import "@matterlabs/hardhat-zksync-solc";

const config: HardhatUserConfig = {
  zksolc: {
    version: "1.3.10", // Use latest available in https://github.com/matter-labs/zksolc-bin/
    compilerSource: "binary",
    settings: {},
  },
  defaultNetwork: "zkSyncTestnet",
  networks: {
    hardhat: {
      zksync: true,
    },
    zkSyncTestnet: {
      url: "https://testnet.era.zksync.dev",
      ethNetwork: "goerli", // Can also be the RPC URL of the network (e.g. `https://goerli.infura.io/v3/<API_KEY>`)
      zksync: true,
    },
  },
  solidity: {
    version: "0.8.17",
  },
};

export default config;

сохраняем и выходим из нано

Paymaster contract

nano contracts/MyPaymaster.sol
#вставляем:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

import {IPaymaster, ExecutionResult, PAYMASTER_VALIDATION_SUCCESS_MAGIC} from "@matterlabs/zksync-contracts/l2/system-contracts/interfaces/IPaymaster.sol";
import {IPaymasterFlow} from "@matterlabs/zksync-contracts/l2/system-contracts/interfaces/IPaymasterFlow.sol";
import {TransactionHelper, Transaction} from "@matterlabs/zksync-contracts/l2/system-contracts/libraries/TransactionHelper.sol";

import "@matterlabs/zksync-contracts/l2/system-contracts/Constants.sol";

contract MyPaymaster is IPaymaster {
    uint256 constant PRICE_FOR_PAYING_FEES = 1;

    address public allowedToken;

    modifier onlyBootloader() {
        require(
            msg.sender == BOOTLOADER_FORMAL_ADDRESS,
            "Only bootloader can call this method"
        );
        // Continue execution if called from the bootloader.
        _;
    }

    constructor(address _erc20) {
        allowedToken = _erc20;
    }

    function validateAndPayForPaymasterTransaction(
        bytes32,
        bytes32,
        Transaction calldata _transaction
    )
        external
        payable
        onlyBootloader
        returns (bytes4 magic, bytes memory context)
    {
        // By default we consider the transaction as accepted.
        magic = PAYMASTER_VALIDATION_SUCCESS_MAGIC;
        require(
            _transaction.paymasterInput.length >= 4,
            "The standard paymaster input must be at least 4 bytes long"
        );

        bytes4 paymasterInputSelector = bytes4(
            _transaction.paymasterInput[0:4]
        );
        if (paymasterInputSelector == IPaymasterFlow.approvalBased.selector) {
            // While the transaction data consists of address, uint256 and bytes data,
            // the data is not needed for this paymaster
            (address token, uint256 amount, bytes memory data) = abi.decode(
                _transaction.paymasterInput[4:],
                (address, uint256, bytes)
            );

            // Verify if token is the correct one
            require(token == allowedToken, "Invalid token");

            // We verify that the user has provided enough allowance
            address userAddress = address(uint160(_transaction.from));

            address thisAddress = address(this);

            uint256 providedAllowance = IERC20(token).allowance(
                userAddress,
                thisAddress
            );
            require(
                providedAllowance >= PRICE_FOR_PAYING_FEES,
                "Min allowance too low"
            );

            // Note, that while the minimal amount of ETH needed is tx.gasPrice * tx.gasLimit,
            // neither paymaster nor account are allowed to access this context variable.
            uint256 requiredETH = _transaction.gasLimit *
                _transaction.maxFeePerGas;

            try
                IERC20(token).transferFrom(userAddress, thisAddress, amount)
            {} catch (bytes memory revertReason) {
                // If the revert reason is empty or represented by just a function selector,
                // we replace the error with a more user-friendly message
                if (revertReason.length <= 4) {
                    revert("Failed to transferFrom from users' account");
                } else {
                    assembly {
                        revert(add(0x20, revertReason), mload(revertReason))
                    }
                }
            }

            // The bootloader never returns any data, so it can safely be ignored here.
            (bool success, ) = payable(BOOTLOADER_FORMAL_ADDRESS).call{
                value: requiredETH
            }("");
            require(
                success,
                "Failed to transfer tx fee to the bootloader. Paymaster balance might not be enough."
            );
        } else {
            revert("Unsupported paymaster flow");
        }
    }

    function postTransaction(
        bytes calldata _context,
        Transaction calldata _transaction,
        bytes32,
        bytes32,
        ExecutionResult _txResult,
        uint256 _maxRefundedGas
    ) external payable override onlyBootloader {
        // Refunds are not supported yet.
    }

    receive() external payable {}
}

сохраняем и выходим из нано

nano contracts/MyERC20.sol
#вставляем:

// SPDX-License-Identifier: UNLICENSED

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract MyERC20 is ERC20 {
    uint8 private _decimals;

    constructor(
        string memory name_,
        string memory symbol_,
        uint8 decimals_
    ) ERC20(name_, symbol_) {
        _decimals = decimals_;
    }

    function mint(address _to, uint256 _amount) public returns (bool) {
        _mint(_to, _amount);
        return true;
    }

    function decimals() public view override returns (uint8) {
        return _decimals;
    }
}

сохраняем и выходим из нано

Компилируем и деплоим контракты:

cd deploy

nano deploy-paymaster.ts
#вставляем:

import { utils, Provider, Wallet } from "zksync-web3";
import * as ethers from "ethers";
import { HardhatRuntimeEnvironment } from "hardhat/types";
import { Deployer } from "@matterlabs/hardhat-zksync-deploy";

export default async function (hre: HardhatRuntimeEnvironment) {
  const provider = new Provider("https://testnet.era.zksync.dev");

  // The wallet that will deploy the token and the paymaster
  // It is assumed that this wallet already has sufficient funds on zkSync
  const wallet = new Wallet("<PRIVATE-KEY>");

  // The wallet that will receive ERC20 tokens
  const emptyWallet = Wallet.createRandom();
  console.log(`Empty wallet's address: ${emptyWallet.address}`);
  console.log(`Empty wallet's private key: ${emptyWallet.privateKey}`);

  const deployer = new Deployer(hre, wallet);

  // Deploying the ERC20 token
  const erc20Artifact = await deployer.loadArtifact("MyERC20");
  const erc20 = await deployer.deploy(erc20Artifact, [
    "MyToken",
    "MyToken",
    18,
  ]);
  console.log(`ERC20 address: ${erc20.address}`);

  // Deploying the paymaster
  const paymasterArtifact = await deployer.loadArtifact("MyPaymaster");
  const paymaster = await deployer.deploy(paymasterArtifact, [erc20.address]);
  console.log(`Paymaster address: ${paymaster.address}`);

  console.log("Funding paymaster with ETH");
  // Supplying paymaster with ETH
  await (
    await deployer.zkWallet.sendTransaction({
      to: paymaster.address,
      value: ethers.utils.parseEther("0.06"),
    })
  ).wait();

  let paymasterBalance = await provider.getBalance(paymaster.address);

  console.log(`Paymaster ETH balance is now ${paymasterBalance.toString()}`);

  // Supplying the ERC20 tokens to the empty wallet:
  await // We will give the empty wallet 3 units of the token:
  (await erc20.mint(emptyWallet.address, 3)).wait();

  console.log("Minted 3 tokens for the empty wallet");

  console.log(`Done!`);
}

Заменить <PRIVATE-KEY> на приватный ключ от вашего метамаска

сохраняем и выходим из нано

yarn hardhat compile

yarn hardhat deploy-zksync --script deploy-paymaster.ts
#вывод должен быть такой:

Тут у нас создался новый кошелек, на который было сминчено 3 токена, запоминаем:
2я строка - <EMPTY_WALLET_PRIVATE_KEY>
3я строка - <TOKEN_ADDRESS>
4я строка - <PAYMASTER_ADDRESS>

nano use-paymaster.ts
#вставляем:

import { Provider, utils, Wallet } from "zksync-web3";
import * as ethers from "ethers";
import { HardhatRuntimeEnvironment } from "hardhat/types";

// Put the address of the deployed paymaster here
const PAYMASTER_ADDRESS = "<PAYMASTER_ADDRESS>";

// Put the address of the ERC20 token here:
const TOKEN_ADDRESS = "<TOKEN_ADDRESS>";

// Wallet private key
const EMPTY_WALLET_PRIVATE_KEY = "<EMPTY_WALLET_PRIVATE_KEY>";

function getToken(hre: HardhatRuntimeEnvironment, wallet: Wallet) {
  const artifact = hre.artifacts.readArtifactSync("MyERC20");
  return new ethers.Contract(TOKEN_ADDRESS, artifact.abi, wallet);
}

export default async function (hre: HardhatRuntimeEnvironment) {
  const provider = new Provider("https://testnet.era.zksync.dev");
  const emptyWallet = new Wallet(EMPTY_WALLET_PRIVATE_KEY, provider);

  // const paymasterWallet = new Wallet(PAYMASTER_ADDRESS, provider);
  // Obviously this step is not required, but it is here purely to demonstrate that indeed the wallet has no ether.
  const ethBalance = await emptyWallet.getBalance();
  if (!ethBalance.eq(0)) {
    throw new Error("The wallet is not empty!");
  }

  console.log(
    `ERC20 token balance of the empty wallet before mint: ${await emptyWallet.getBalance(
      TOKEN_ADDRESS
    )}`
  );

  let paymasterBalance = await provider.getBalance(PAYMASTER_ADDRESS);
  console.log(`Paymaster ETH balance is ${paymasterBalance.toString()}`);

  const erc20 = getToken(hre, emptyWallet);

  const gasPrice = await provider.getGasPrice();

  // Encoding the "ApprovalBased" paymaster flow's input
  const paymasterParams = utils.getPaymasterParams(PAYMASTER_ADDRESS, {
    type: "ApprovalBased",
    token: TOKEN_ADDRESS,
    // set minimalAllowance as we defined in the paymaster contract
    minimalAllowance: ethers.BigNumber.from(1),
    // empty bytes as testnet paymaster does not use innerInput
    innerInput: new Uint8Array(),
  });

  // Estimate gas fee for mint transaction
  const gasLimit = await erc20.estimateGas.mint(emptyWallet.address, 5, {
    customData: {
      gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
      paymasterParams: paymasterParams,
    },
  });

  const fee = gasPrice.mul(gasLimit.toString());
  console.log("Transaction fee estimation is :>> ", fee.toString());

  console.log(`Minting 5 tokens for empty wallet via paymaster...`);
  await (
    await erc20.mint(emptyWallet.address, 5, {
      // paymaster info
      customData: {
        paymasterParams: paymasterParams,
        gasPerPubdata: utils.DEFAULT_GAS_PER_PUBDATA_LIMIT,
      },
    })
  ).wait();

  console.log(
    `Paymaster ERC20 token balance is now ${await erc20.balanceOf(
      PAYMASTER_ADDRESS
    )}`
  );

  paymasterBalance = await provider.getBalance(PAYMASTER_ADDRESS);
  console.log(`Paymaster ETH balance is now ${paymasterBalance.toString()}`);

  console.log(
    `ERC20 token balance of the empty wallet after mint: ${await emptyWallet.getBalance(
      TOKEN_ADDRESS
    )}`
  );
}

Заменить <EMPTY_WALLET_PRIVATE_KEY>, <TOKEN_ADDRESS> и <PAYMASTER_ADDRESS> на свои значения

Сохраняем и выходим из нано

yarn hardhat deploy-zksync --script use-paymaster.ts
#вывод, как на скрине ниже

Напоминаю, что это пятый контракт из серии, не забывайте выполнить первые и подписывайтесь!