JSON Web Signature (JWS) Token via HMAC using SHA-256 w Node.js Crypto Module

jws-hs256.mjs

import { Buffer } from 'node:buffer';
import fs from "node:fs";
import url from 'node:url';
import path from "node:path";
const {createHmac, generateKey} = await import('node:crypto');
var claims = {name:"Joe",roles:["member","admin"]};
var secretKey;

(async function () {
  secretKey = await generateSecretKey();
  let jws = await returnJWS(claims);
  console.log("\x1b[37mYour JWS token is: " + consoleString(jws));
  console.log("Paste JSON Web Token In Terminal Then Press Enter.")
})();

function returnJWS(claims){
  let headerObject = {
    alg: 'HS256',
    typ: 'JWT',
    kid: 'public'
  };
  let headerString = JSON.stringify(headerObject);
  let encodedHeader = Buffer.from(headerString).toString('base64url');
  let payloadString = JSON.stringify(claims);
  let encodedPayload = Buffer.from(payloadString).toString('base64url');
  const hmac = createHmac('sha256', secretKey);
  hmac.update(encodedHeader + '.' + encodedPayload);
  let signature = hmac.digest('base64url');

  let jsonWebToken = encodedHeader + '.' + encodedPayload + '.' + signature;
  return jsonWebToken;
}

function validateJWS(jwt){
  try {
    let jwtParts = jwt.split('.');
    let jwtHeader = jwtParts[0];
    let jwtPayload = jwtParts[1];
    let jwtSignature = jwtParts[2].trim();
    let signature;
    let header = JSON.parse(Buffer.from(jwtHeader, 'base64url').toString('utf-8'));
    let alg = header.alg;
    if(alg === "HS256"){
      const hmac = createHmac('sha256', secretKey);
      hmac.update(jwtHeader + '.' + jwtPayload);
      signature = hmac.digest('base64url').trim();
      console.log(signature)
      console.log(jwtSignature)
      if(signature == jwtSignature) {
        return Buffer.from(jwtPayload, 'base64url').toString('utf-8')
      } else {
        return "\x1b[31mInvalid Token!\x1b[37m";
      }
    } else {
      throw (error)     
    }
  } catch (e) {
    console.log (e);
    return "\x1b[31mInvalid Token!\x1b[37m";
  }
}

function generateSecretKey () {
  return new Promise(function(resolve, reject) {
    generateKey('aes', { length: 256 }, (err, key) => {
      if (err) {
        reject (err);
      }
      resolve (key)
    });
  });
}

export default {returnJWS, validateJWS};

process.stdin.setEncoding('utf8');
process.stdin.on('readable', async () => {
  let chunk;
  while ((chunk = process.stdin.read()) !== null) {
    console.log(await validateJWS(chunk));
  }
});

function consoleString(token){
  let tokenParts = token.split(/(\.)/);
  let colors = ["32m","31m","33m","34m","36m"];
  let color = "\x1b[X";
  let str = ""
  tokenParts.forEach(function(part,index){
    if(part != "."){
      str += color.replace("X",colors.shift())
    }
    str += part;
    str += "\x1b[37m"
  })
  return str;
}