Simple Nodejs approach to work with JWT's using JOSE and public/private keys generated with OpenSSL

app.js

const jose = require('jose');
const fs = require('fs');
const path = require("path");

// project
// ├── src
// │   └── app.js
// ├── package.json
// └── privatekey.pub
// └── publickey.cer

const privateKey = jose.JWK.asKey(fs.readFileSync(path.resolve(__dirname, '../privatekey.pem')));
const publicKey = jose.JWK.asKey(fs.readFileSync(path.resolve(__dirname, '../publickey.cer')));

// Sign
let jwt = jose.JWT.sign(
  { 'urn:example:claim': 'foo' },
  privateKey,
  {
    algorithm: 'RS512',
    expiresIn: '1 min',
    header: {
      typ: 'JWT'
    },
    audience: 'urn:example:client_id',
    issuer: 'https://op.example.com'
  }
);

try {
  // Verify JWT and also verify payload content
  let payload = jose.JWT.verify(
    jwt,
    publicKey,
    {
      issuer: 'https://op.example.com',
      audience: 'urn:example:client_id'
    }
    );
    console.log(payload);
} catch (err) {
  console.log(err);
  if (err instanceof jose.errors.JOSEError && err.code === 'ERR_JWT_EXPIRED') {
    console.log('Expired token');
  }
  else if (err instanceof jose.errors.JOSEError && err.code === 'ERR_JWT_MALFORMED') {
    console.log('Invalid token');
  }
  else if (err instanceof jose.errors.JOSEError && err.code === 'ERR_JWT_CLAIM_INVALID') {
    console.log('Claim invalid');
  }
  else {
    console.log('Unexpected error');
  }
};

instructions.md

First you need to generate a pair of keys. Generate the private as follows:

openssl genrsa -out privatekey.pem 4096

Then generate the public one using the private generated previously:

openssl req -new -x509 -key privatekey.pem -out publickey.cer

Then proceed to install node dependencies, execute the following in project root directory:

npm install

Finally run:

npm start

package.json

{
  "name": "use-of-jose",
  "version": "1.0.0",
  "description": "Use of JOSE library and private/public keys",
  "main": "src/app.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start" "node src/app"
  },
  "author": "Ricardo de la Cruz <the_phantom_racer@hotmail.com>",
  "license": "ISC",
  "dependencies": {
    "jose": "^1.27.0"
  }
}

Keys must be created first to avoid errors in app execution.