Attempting to get the public key

getPubKey.js

const ethers = require("ethers")

const pk =
 "0x0471c746523d16e93d4738f882d9b0beebf66c68caa0f895db15686b57b878cfc7b3e09813ba94f1bbfaa91a06566d3d18bbf69d10bcc947325bbcd6fea97ed692"
const ad = "0xcD3edF915387E2555A829567cE0dBbC919834B82"

getPubKey = async () => {
 const infuraProvider = new ethers.providers.JsonRpcProvider(
  "https://ropsten.infura.io/v3/<projectID>"
 )
 const tx = await infuraProvider.getTransaction(
  "0x07035a057bdddc9c0e1c07c32b341f6082f9d6be2dc39452753587c2e69fbf96"
 )
 const expandedSig = {
  r: tx.r,
  s: tx.s,
  v: tx.v
 }
 const signature = ethers.utils.joinSignature(expandedSig)
 const txData = {
  gasPrice: tx.gasPrice,
  gasLimit: tx.gasLimit,
  value: tx.value,
  nonce: tx.nonce,
  data: tx.data,
  chainId: tx.chainId,
  to: tx.to
 }
 const rsTx = await ethers.utils.resolveProperties(txData)
 const raw = ethers.utils.serializeTransaction(rsTx) // returns RLP encoded tx
 const msgHash = ethers.utils.keccak256(raw) // as specified by ECDSA
 const msgBytes = ethers.utils.arrayify(msgHash) // create binary hash
 const recoveredPubKey = ethers.utils.recoverPublicKey(msgBytes, signature)
 const recoveredAddress = ethers.utils.recoverAddress(msgBytes, signature)
 console.log(recoveredAddress)
 console.log(recoveredPubKey)
 console.log("Correct public key:", recoveredPubKey === pk)
 console.log("Correct address:", recoveredAddress === ad)
}

getPubKey()

Thanks very much for the useful code - thanks for sharing!
Just to note, there is no tx.chainId or tx.data, and also ethers excepts on gasPrice and value unless converted to BigNumber.

Pull the chainId from the provider, and use tx.input for data.

txData object should be:

const txData = {
        nonce: tx.nonce,
        gasPrice: ethers.BigNumber.from(tx.gasPrice),
        gasLimit: tx.gas,
        to: tx.to,
        value: ethers.BigNumber.from(tx.value),
        data: tx.input,
        chainId: chainId // passed in - pull from network object, etc.
    }

Great piece, however today it lacks support for EIP-1559 transactions. I amended the code a bit to account for that (replace const txData = .... with this block):

...
    let txData;
    switch (tx.type) {
        case 0:
            txData = {
                gasPrice: tx.gasPrice,
                gasLimit: tx.gasLimit,
                value: tx.value,
                nonce: tx.nonce,
                data: tx.data,
                chainId: tx.chainId,
                to: tx.to
            };
            break;
        case 2:
            txData = {
                gasLimit: tx.gasLimit,
                value: tx.value,
                nonce: tx.nonce,
                data: tx.data,
                chainId: tx.chainId,
                to: tx.to,
                type: 2,
                maxFeePerGas: tx.maxFeePerGas,
                maxPriorityFeePerGas: tx.maxPriorityFeePerGas
            }
            break;
        default:
            throw "Unsupported tx type";
    }
...

Thanks @pokrovskyy! This was on my todo list for a while now 👍

Great piece, however today it lacks support for EIP-1559 transactions. I amended the code a bit to account for that (replace const txData = .... with this block):

...
    let txData;
    switch (tx.type) {
        case 0:
            txData = {
                gasPrice: tx.gasPrice,
                gasLimit: tx.gasLimit,
                value: tx.value,
                nonce: tx.nonce,
                data: tx.data,
                chainId: tx.chainId,
                to: tx.to
            };
            break;
        case 2:
            txData = {
                gasLimit: tx.gasLimit,
                value: tx.value,
                nonce: tx.nonce,
                data: tx.data,
                chainId: tx.chainId,
                to: tx.to,
                type: 2,
                maxFeePerGas: tx.maxFeePerGas,
                maxPriorityFeePerGas: tx.maxPriorityFeePerGas
            }
            break;
        default:
            throw "Unsupported tx type";
    }
...

nice job👍🏻 @pokrovskyy @chrsengel