Calculate ProxyAddress from a Given CREATE2 call - Example using GnosisSafe

script.js

// This script assume using the GnosisSafe & GnosisSafeProxyFactory from here
// https://github.com/gnosis/safe-contracts/blob/v1.2.0/contracts/proxies/GnosisSafeProxyFactory.sol
// safe -> https://github.com/gnosis/safe-contracts/blob/v1.2.0/contracts/GnosisSafe.sol

import { ethers } from 'ethers';
import Web3 from 'web3';
import * as ethUtil from 'ethereumjs-util';
import abi from 'ethereumjs-abi';

const rpcUrl = ''; // Fill your RPC URI
const web3 = web3 = new Web3(new Web3.providers.HttpProvider(rpcUrl));

const safeProxyFactoryAddress = '0x76E2cFc1F5Fa8F6a5b3fC4c8F4788F0116861F9B';
const safeMasterCopyAddress = '0x6851d6fdfafd08c0295c392436245e5bc78b0185';

// contract for deploying new safes
const safeProxyFactory = new web3.eth.Contract(
  safeProxyFactoryAbi,
  safeProxyFactoryAddress,
);
const safe = new web3.eth.Contract(
  safeMasterCopyAbi,
  safeMasterCopyAddress,
);

const saltNonce = (new Date().getTime() / 1000).toFixed();
const setupData = safe.methods
    .setup(
    [delegateAddress, minionAddress], // owners
    threshold, // signing threshol d
    Address0, // to - Contract address for optional delegate call.
    "0x", // data - Data payload for optional delegate call.
    Address0, // fallbackHandler
    Address0, // paymentToken
    0, // payment
    Address0, // paymentReceiver
    )
    .encodeABI();

const proxyCreationCode = await safeProxyFactory.methods
    .proxyCreationCode()
    .call();

// Alternative 1: Using ethereumjs-abi library
// ========================================================

// Check GnosisSafeProxyFactory.deployProxyWithNonce method
const encodedNonce = abi
  .rawEncode(['uint256'], [saltNonce])
  .toString('hex');
const salt = ethUtil.keccak256(
  `0x${ethUtil.keccak256(setupData).toString('hex') + encodedNonce}`,
);

const constructorData = abi
  .rawEncode(['address'], [safeMasterCopyAddress])
  .toString('hex');
const initCode = proxyCreationCode + constructorData;

const contractAddress = `0x${ethUtil
  .generateAddress2(
    safeProxyFactory.options.address,
    salt,
    initCode,
  )
  .toString('hex')}`;

console.log('Predicted safe address using ethereumjs-util', contractAddress);

// Alternative 2: Using ethers library
// ========================================================

const salt2 = ethers.utils.solidityKeccak256(
  ['bytes32', 'uint256'],
  [ethers.utils.solidityKeccak256(['bytes'], [setupData]), saltNonce],
);

// does not work with web3.eth.abi.encodeParameters as it packed encode with additional data like length ?
const initCode2 = ethers.utils.solidityPack(
  ['bytes', 'uint256'],
  [proxyCreationCode, safeMasterCopyAddress],
);

const contractAddress2 = ethers.utils.getCreate2Address(
    safeProxyFactory.options.address,
    salt2,
    ethers.utils.keccak256(initCode2),
  );

console.log('Predicted safe address using ethers', contractAddress2);