JSON Web Signature (JWS) Token via Asymmetric RSA Key Pair (RSASSA-PKCS1-v1_5) Using Node.js Crypto Module

jws-rs256.mjs

import { Buffer } from 'node:buffer';
import fs from "node:fs";
import url from 'node:url';
import path from "node:path";
const {createSign, createVerify, generateKeyPairSync} = await import('node:crypto');
var claims = {name:"Joe",roles:["member","admin"]};
var { privateKey, publicKey } = generateKeyPairSync("rsa", {
  modulusLength: 2048,
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem'
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem',
  }
});

(async function () {
  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: 'RS256',
    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 sign = createSign('SHA256');
  sign.write(encodedHeader + '.' + encodedPayload);
  sign.end();
  let signature = sign.sign(privateKey, '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];
    let valid = false;
    let header = JSON.parse(Buffer.from(jwtHeader, 'base64url').toString('utf-8'));
    let alg = header.alg;
    if(alg === "RS256"){ // MUST verify alg is not set to none
      let verify = createVerify('SHA256');
      verify.write(jwtHeader + '.' + jwtPayload);
      verify.end();
      valid = verify.verify(publicKey, jwtSignature, 'base64url');
      if(valid){
        return JSON.parse(Buffer.from(jwtPayload, 'base64url').toString('utf-8'));
      } else {
        throw (error)
      }
    } else {
      throw (error)     
    }
  } catch (e) {
    //console.log (e);
    return "\x1b[31mInvalid Token!\x1b[37m";
  }
}

function generatePrivateKey (str) {
  return new Promise(function(resolve, reject) {
    try {
      let key = createPrivateKey({
          key: str,
          format: 'pem',
          encoding: 'utf-8'
      })
      resolve (key);
    } catch (e) {
      reject (e);
    }
  });
}

function generatePublicKey (str) {
  return new Promise(function(resolve, reject) {
    try {
      let key = createPublicKey({
          key: str,
          format: 'pem',
          encoding: 'utf-8'
      })
      resolve (key);
    } catch (e) {
      reject (e);
    }
  });
}

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;
}