@connectedcars/jwtutils

node-jwtutils

Zero dependency JWT encoding and decoding for Node.

Features:

• Encode and decode any JWT tokens
• Supported asymmetric algorithmes (RS256, RS384, RS512, ES256, ES384 and ES512)
• Supported symmetric algorithmes (HS256, HS384 and HS512)
• Support for multiple issuers and keys per issuer.
• Import keys from JWK endpoints
• Easy service authentication for Google and Github
• Express middleware to validate JWT's

Background

Most other JWT implementations tend be complex and have a large array of dependencies because they implement the seldom used JOSE standard. This often makes the whole JWT encoding/decoding complicated and hard to understand, something it really should not be.

So the focus of this module has been to make a simple, secure, fast and flexible set of utility methods to work with JWT's. The code itself is also easy to understand and less than 200 lines of code, making it much easier to security audit the code.

Also note doing your own crypto is a bad idea so this module only deals with the encoding/decoding of the JWT, the underlaying crypto operations are done by Node's build-in crypto api that uses openssl.

While symmetric algorithms are supported for legacy integrations, they are not advisable for production use.

Samples

• Integrate with Google Identity Platform

Basic usage

const { JwtUtils, JwtVerifyError } = require('@connectedcars/jwtutils')

const unixNow = Math.floor(Date.now() / 1000)

let jwtHeader = {
  typ: 'JWT',
  alg: 'RS256',
  kid: '1'
}

let jwtBody = {
  aud: 'https://api.domain.tld',
  iss: 'https://jwt.io/',
  sub: '[e-mail]',
  iat: unixNow,
  exp: unixNow + 600,
  scope: ['http://stuff', 'http://stuff2']
}

// Don't use this key for anything but testing as this is the key from jwt.io
const pemEncodedPrivateKey =
  '-----BEGIN RSA PRIVATE KEY-----\n' +
  'MIICWwIBAAKBgQDdlatRjRjogo3WojgGHFHYLugdUWAY9iR3fy4arWNA1KoS8kVw\n' +
  '33cJibXr8bvwUAUparCwlvdbH6dvEOfou0/gCFQsHUfQrSDv+MuSUMAe8jzKE4qW\n' +
  '+jK+xQU9a03GUnKHkkle+Q0pX/g6jXZ7r1/xAK5Do2kQ+X5xK9cipRgEKwIDAQAB\n' +
  'AoGAD+onAtVye4ic7VR7V50DF9bOnwRwNXrARcDhq9LWNRrRGElESYYTQ6EbatXS\n' +
  '3MCyjjX2eMhu/aF5YhXBwkppwxg+EOmXeh+MzL7Zh284OuPbkglAaGhV9bb6/5Cp\n' +
  'uGb1esyPbYW+Ty2PC0GSZfIXkXs76jXAu9TOBvD0ybc2YlkCQQDywg2R/7t3Q2OE\n' +
  '2+yo382CLJdrlSLVROWKwb4tb2PjhY4XAwV8d1vy0RenxTB+K5Mu57uVSTHtrMK0\n' +
  'GAtFr833AkEA6avx20OHo61Yela/4k5kQDtjEf1N0LfI+BcWZtxsS3jDM3i1Hp0K\n' +
  'Su5rsCPb8acJo5RO26gGVrfAsDcIXKC+bQJAZZ2XIpsitLyPpuiMOvBbzPavd4gY\n' +
  '6Z8KWrfYzJoI/Q9FuBo6rKwl4BFoToD7WIUS+hpkagwWiz+6zLoX1dbOZwJACmH5\n' +
  'fSSjAkLRi54PKJ8TFUeOP15h9sQzydI8zJU+upvDEKZsZc/UhT/SySDOxQ4G/523\n' +
  'Y0sz/OZtSWcol/UMgQJALesy++GdvoIDLfJX5GBQpuFgFenRiRDabxrE9MNUZ2aP\n' +
  'FaFp+DyAe+b4nDwuJaW2LURbr8AEZga7oQj0uYxcYw==\n' +
  '-----END RSA PRIVATE KEY-----'

// let jwt = JwtUtils.encode(pemEncodedPrivateKey, jwtHeader, jwtBody, privateKeyPassword)
let jwt = JwtUtils.encode(pemEncodedPrivateKey, jwtHeader, jwtBody)

// Don't use this key for anything but testing as this is the key from jwt.io
const publicKey =
  '-----BEGIN PUBLIC KEY-----\n' +
  'MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDdlatRjRjogo3WojgGHFHYLugd\n' +
  'UWAY9iR3fy4arWNA1KoS8kVw33cJibXr8bvwUAUparCwlvdbH6dvEOfou0/gCFQs\n' +
  'HUfQrSDv+MuSUMAe8jzKE4qW+jK+xQU9a03GUnKHkkle+Q0pX/g6jXZ7r1/xAK5D\n' +
  'o2kQ+X5xK9cipRgEKwIDAQAB\n' +
  '-----END PUBLIC KEY-----'

const allowedAudinces = ['https://api.domain.tld']

const pubKeys = {
  'https://jwt.io/': {
    '1@RS256': publicKey,
    'default@RS256': publicKey // Will default to this key if the header does not have a kid
  }
}

try {
  let decodedJwtBody = JwtUtils.decode(jwt, pubKeys, allowedAudinces)
} catch (e) {
  if (e instanceof JwtVerifyError) {
    // Can be returned to user
  } else {
    // Should not be returned to user
    console.error(e)
  }
}

Usage of express middleware

const express = require('express')
const { JwtAuthMiddleware, JwtVerifyError } = require('@connectedcars/jwtutils')

// Configuration
const audiences = ['https://api.domain.tld']
const pubKeys = {
  'https://jwt.io/': {
    '1@RS256': publicKey // Fx. use key from before
  },
  'https://jwt.io/custom': { // Overwrite default validation for this issuer
    '1@RS256': { // Same options can also be used directly with decode
      publicKey: publicKey,
      expiresMax: 3600, // Don't allow token that has a lifetime over 1 hour
      expiresSkew: 600, // Allow tokens that expired up to 10 minutes ago
      nbfIatSkew: 300, // Allow tokens that has nbf or iat in the future by up to 5 minutes
    }
  }
}

const app = express()

// Register the middleware
app.use(JwtAuthMiddleware(pubKeys, audiences, user => { // Also supports Promises and async
  if (user.issuer === 'https://jwt.io/') {
    if (!user.subject.match(/^[^@]+@domain\.tld$/)) {
      throw new JwtVerifyError('Issuer https://jwt.io/ only allowed to have subject ending in @domain.tld')
    }
  }
}))

// Register an error handler to return 401 errors
app.use((err, req, res, next) => {
  if (err instanceof JwtVerifyError) {
    if (err.innerError) {
      console.error(`Failed with: ${err.innerError.message}`)
    }
    res.status(401).send(err.message)
  } else {
    res.status(500).send('Unknown error')
  }
})

app.get('/', (req, res) => {
  res.send(`Hello ${req.user.subject}`)
})
app.listen(3000, () => {
  console.log('Example app listening on port 3000!')
})

Integration with 3rd parties

Google Identity platform:

const { PubkeysHelper } = require('@connectedcars/jwtutils')

// Fetch with Google's public keys every hour
const applyGoogleKeys = (pubKeys) => {
  PubkeysHelper.fetchJwkKeys('https://www.googleapis.com/oauth2/v3/certs')
    .then(keys => {
      pubKeys['https://accounts.google.com'] = keys
    })
    .catch(e => {
      // Do some error handling
      console.log(e)
    })
}

applyGoogleKeys(pubKeys)
setInterval(() => {
  applyGoogleKeys(pubKeys)
}, 60 * 60 * 1000)

Usage of service authentication (Google and Github)

const { JwtServiceAuth } = require('./index')
const fs = require('fs')
const r2 = require('r2')

// Wrap your favorite http library
let httpRequestHandler = async (method, url, headers, body) => { // Fx. POST, http://domain.tld, {}, "..."
  // Do http request
  let httpRespone = await r2[method.toLowerCase()](url, { headers, body }).response
  let data = await httpResponse.arrayBuffer()
  return {
    statusCode: httpResponse.status,
    data: data,
    headers: httpResponse.headers
  }
})

let jwtServiceAuth = new JwtServiceAuth(httpRequestHandler) // Or use the built-in default

let gitHubAppPrivateKey = fs.readFileSync("user-appname.2017-01-01.private-key.pem", 'utf8')
let googleServiceAccountKeyfile = fs.readFileSync("user-serviceaccount-12345678.json", 'utf8')

async function getAccessTokens() {
  let githubAppToken = await = jwtServiceAuth.getGithubAccessToken(gitHubAppPrivateKey, 1, 1)
  let googleToken = await jwtServiceAuth.getGoogleAccessToken(googleServiceAccountKeyfile)
}

Documentation

• Github App: https://developer.github.com/apps/building-github-apps/authentication-options-for-github-apps/
• Google Service Account: https://developers.google.com/identity/protocols/OAuth2ServiceAccount

Generate own keypair

Generate private RSA key:

# Here the key is encrypted with aes256
openssl genrsa -aes256 -out private.pem 2048

Generate public key from private key:

openssl rsa -in private.pem -outform PEM -pubout -out public.pem

Command line helper utils

NOTE: Does not support nested JSON

Load private key:

jwtencode private.pem

Copy/paste to stdin (Ctrl-D to end), the password line is only needed if the private key is encrypted:

password password-for-private-key
{
  "alg": "RS256",
  "typ": "JWT",
  "kid": "1"
}
{
  "iss": "jwt.io",
  "aud": "https://api.domain.tld",
  "sub": "[e-mail]",
  "iat": 1504292127,
  "nbf": 1504292127,
  "exp": 1598986470
}

jwtdecode public.pem 1 RS256 https://jwt.io localhost

Copy/paste to stdin (Ctrl-D to end):

eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCIsImtpZCI6IjEifQ.eyJpc3MiOiJodHRwczovL2p3dC5pbyIsImF1ZCI6ImxvY2FsaG9zdCIsInN1YiI6InN1YmplY3RAZG9tYWluLnRsZCIsImlhdCI6MTUwNDI5MjEyNywibmJmIjoxNTA0MjkyMTI3LCJleHAiOjE1OTg5ODY0NzB9.0L5AWwUF3EleBqnQ6V0Lqa36jCccP4A7cAFHHIY1b-oE7pxCoFr8gnAOrlc16N0WUPI6O17JT79kQIPR-LjFm-BgBycBw4eEFYb8z7iXA-zqgQz4ajZXlIljJtJUBbTupbnzEiBKjEFnTxYqb-vUm-TDwTMPaYzBxqqfOrrvKlw