fastify-jwt

fastify-jwt

JWT utils for Fastify, internally it uses fast-jwt.

NOTE: The plugin has been migrated from using jsonwebtoken to fast-jwt. Even though fast-jwt has 1:1 feature implementation with jsonwebtoken, some exotic implementations might break. In that case please open an issue with details of your implementation. See Upgrading notes for more details about what changes this migration introduced.

fastify-jwt supports Fastify@3. fastify-jwt v1.x supports both Fastify@2.

Install

npm i fastify-jwt --save

Usage

Register as a plugin. This will decorate your fastify instance with the following methods: decode, sign, and verify; refer to their documentation to find how to use the utilities. It will also register request.jwtVerify and reply.jwtSign. You must pass a secret when registering the plugin.

const fastify = require('fastify')()
fastify.register(require('fastify-jwt'), {
  secret: 'supersecret'
})

fastify.post('/signup', (req, reply) => {
  // some code
  const token = fastify.jwt.sign({ payload })
  reply.send({ token })
})

fastify.listen(3000, err => {
  if (err) throw err
})

For verifying & accessing the decoded token inside your services, you can use a global onRequest hook to define the verification process like so:

const fastify = require('fastify')()
fastify.register(require('fastify-jwt'), {
  secret: 'supersecret'
})

fastify.addHook("onRequest", async (request, reply) => {
  try {
    await request.jwtVerify()
  } catch (err) {
    reply.send(err)
  }
})

Afterwards, just use request.user in order to retrieve the user information:

module.exports = async function(fastify, opts) {
  fastify.get("/", async function(request, reply) {
    return request.user
  })
}

However, most of the time we want to protect only some of the routes in our application. To achieve this you can wrap your authentication logic into a plugin like

const fp = require("fastify-plugin")

module.exports = fp(async function(fastify, opts) {
  fastify.register(require("fastify-jwt"), {
    secret: "supersecret"
  })

  fastify.decorate("authenticate", async function(request, reply) {
    try {
      await request.jwtVerify()
    } catch (err) {
      reply.send(err)
    }
  })
})

Then use the preValidation of a route to protect it & access the user information inside:

module.exports = async function(fastify, opts) {
  fastify.get(
    "/",
    {
      preValidation: [fastify.authenticate]
    },
    async function(request, reply) {
      return request.user
    }
  )
}

Make sure that you also check fastify-auth plugin for composing more complex strategies.

Auth0 tokens verification

If you need to verify Auth0 issued HS256 or RS256 JWT tokens, you can use fastify-auth0-verify, which is based on top of this module.

Options

secret (required)

You must pass a secret to the options parameter. The secret can be a primitive type String, a function that returns a String or an object { private, public }.

In this object { private, public } the private key is a string, buffer or object containing either the secret for HMAC algorithms or the PEM encoded private key for RSA and ECDSA. In case of a private key with passphrase an object { private: { key, passphrase }, public } can be used (based on crypto documentation), in this case be sure you pass the algorithm inside the signing options prefixed by the sign key of the plugin registering options).

In this object { private, public } the public key is a string or buffer containing either the secret for HMAC algorithms, or the PEM encoded public key for RSA and ECDSA.

Function based secret is supported by the request.jwtVerify() and reply.jwtSign() methods and is called with request, token, and callback parameters.

Example

const { readFileSync } = require('fs')
const path = require('path')
const fastify = require('fastify')()
const jwt = require('fastify-jwt')
// secret as a string
fastify.register(jwt, { secret: 'supersecret' })
// secret as a function with callback
fastify.register(jwt, {
  secret: function (request, token, callback) {
    // do something
    callback(null, 'supersecret')
  }
})
// secret as a function returning a promise
fastify.register(jwt, {
  secret: function (request, token) {
    return Promise.resolve('supersecret')
  }
})
// secret as an async function
fastify.register(jwt, {
  secret: async function (request, token) {
    return 'supersecret'
  }
})
// secret as an object of RSA keys (without passphrase)
// the files are loaded as strings
fastify.register(jwt, {
  secret: {
    private: readFileSync(`${path.join(__dirname, 'certs')}/private.key`, 'utf8'),
    public: readFileSync(`${path.join(__dirname, 'certs')}/public.key`, 'utf8')
  },
  sign: { algorithm: 'RS256' }
})
// secret as an object of P-256 ECDSA keys (with a passphrase)
// the files are loaded as buffers
fastify.register(jwt, {
  secret: {
    private: {
      key: readFileSync(`${path.join(__dirname, 'certs')}/private.pem`),
      passphrase: 'super secret passphrase'
    },
    public: readFileSync(`${path.join(__dirname, 'certs')}/public.pem`)
  },
  sign: { algorithm: 'ES256' }
})

Optionally you can define global default options that will be used by fastify-jwt API if you do not override them.

Additionally, it is also possible to reject tokens selectively (i.e. blacklisting) by providing the option trusted with the following signature: (request, decodedToken) => boolean|Promise<boolean>|SignPayloadType|Promise<SignPayloadType> where request is a FastifyRequest and decodedToken is the parsed (and verified) token information. Its result should be false or Promise<false> if the token should be rejected or, otherwise, be true or Promise<true> if the token should be accepted and, considering that request.user will be used after that, the return should be decodedToken itself.

Example

const { readFileSync } = require('fs')
const path = require('path')
const fastify = require('fastify')()
const jwt = require('fastify-jwt')
fastify.register(jwt, {
  secret: {
    private: readFileSync(`${path.join(__dirname, 'certs')}/private.pem`, 'utf8')
    public: readFileSync(`${path.join(__dirname, 'certs')}/public.pem`, 'utf8')
  },
  // Global default decoding method options
  decode: { complete: true },
  // Global default signing method options
  sign: {
    algorithm: 'ES256',
    iss: 'api.example.tld'
  },
  // Global default verifying method options
  verify: { allowedIss: 'api.example.tld' }
})

fastify.get('/decode', async (request, reply) => {
  // We clone the global signing options before modifying them
  let altSignOptions = Object.assign({}, fastify.jwt.options.sign)
  altSignOptions.iss = 'another.example.tld'

  // We generate a token using the default sign options
  const token = await reply.jwtSign({ foo: 'bar' })
  // We generate a token using overrided options
  const tokenAlt = await reply.jwtSign({ foo: 'bar' }, altSignOptions)

  // We decode the token using the default options
  const decodedToken = fastify.jwt.decode(token)

  // We decode the token using completely overided the default options
  const decodedTokenAlt = fastify.jwt.decode(tokenAlt, { complete: false })

  return { decodedToken, decodedTokenAlt }
  /**
   * Will return:
   *
   * {
   *   "decodedToken": {
   *     "header": {
   *       "alg": "ES256",
   *       "typ": "JWT"
   *     },
   *     "payload": {
   *       "foo": "bar",
   *       "iat": 1540305336
   *       "iss": "api.example.tld"
   *     },
   *     "signature": "gVf5bzROYB4nPgQC0nbJTWCiJ3Ya51cyuP-N50cidYo"
   *   },
   *   decodedTokenAlt: {
   *     "foo": "bar",
   *     "iat": 1540305337
   *     "iss": "another.example.tld"
   *   },
   * }
   */
})

fastify.listen(3000, err => {
  if (err) throw err
})

cookie

Example using cookie

In some situations you may want to store a token in a cookie. This allows you to drastically reduce the attack surface of XSS on your web app with the httpOnly and secure flags. Cookies can be susceptible to CSRF. You can mitigate this by either setting the sameSite flag to strict, or by using a CSRF library such as fastify-csrf.

Note: This plugin will look for a decorated request with the cookies property. fastify-cookie supports this feature, and therefore you should use it when using the cookie feature. The plugin will fallback to looking for the token in the authorization header if either of the following happens (even if the cookie option is enabled):

• The request has both the authorization and cookie header
• Cookie is empty, authorization header is present

If you are signing your cookie, you can set the signed boolean to true which will make sure the JWT is verified using the unsigned value.

const fastify = require('fastify')()
const jwt = require('fastify-jwt')

fastify.register(jwt, {
  secret: 'foobar'
  cookie: {
    cookieName: 'token',
    signed: false
  }
})

fastify
  .register(require('fastify-cookie'))

fastify.get('/cookies', async (request, reply) => {
  const token = await reply.jwtSign({
    name: 'foo',
    role: ['admin', 'spy']
  })

  reply
    .setCookie('token', token, {
      domain: 'your.domain',
      path: '/',
      secure: true, // send cookie over HTTPS only
      httpOnly: true,
      sameSite: true // alternative CSRF protection
    })
    .code(200)
    .send('Cookie sent')
})

fastify.addHook('onRequest', (request) => request.jwtVerify())

fastify.get('/verifycookie', (request, reply) => {
  reply.send({ code: 'OK', message: 'it works!' })
})

fastify.listen(3000, err => {
  if (err) throw err
})

trusted

Example trusted tokens

const fastify = require('fastify')()

fastify.register(require('fastify-jwt'), {
  secret: 'foobar',
  trusted: validateToken
})

fastify.addHook('onRequest', (request) => request.jwtVerify())

fastify.get('/', (request, reply) => {
  reply.send({ code: 'OK', message: 'it works!' })
})

fastify.listen(3000, (err) => {
  if (err) {
    throw err
  }
})

// ideally this function would do a query against some sort of storage to determine its outcome
async function validateToken(request, decodedToken) {
  const denylist = ['token1', 'token2']

  return !denylist.includes(decodedToken.jti)
}

formatUser

Example with formatted user

You may customize the request.user object setting a custom sync function as parameter:

const fastify = require('fastify')();
fastify.register(require('fastify-jwt'), {
  formatUser: function (user) {
    return {
      departmentName: user.department_name,
      name: user.name
    }
  },
  secret: 'supersecret'
});

fastify.addHook('onRequest', (request, reply) =>  request.jwtVerify());

fastify.get("/", async (request, reply) => {
  return `Hello, ${request.user.name} from ${request.user.departmentName}.`;
});

namespace

To define multiple JWT validators on the same routes, you may use the namespace option. You can combine this with custom names for jwtVerify and jwtSign.

When you omit the jwtVerify and jwtSign options, the default function name will be <namespace>JwtVerify and <namespace>JwtSign.

Example with namespace

const fastify = require('fastify')

fastify.register(jwt, {
  secret: 'test',
  namespace: 'security',
  jwtVerify: 'securityVerify',
  jwtSign: 'securitySign'
})

fastify.register(jwt, {
  secret: 'fastify',
  namespace: 'airDrop'
})

// use them like this:
fastify.post('/sign/:namespace', async function (request, reply) {
  switch (request.params.namespace) {
    case 'security':
      return reply.securitySign(request.body)
    default:
      return reply.airDropJwtSign(request.body)
  }
})

messages

For your convenience, you can override the default HTTP response messages sent when an unauthorized or bad request error occurs. You can choose the specific messages to override and the rest will fallback to the default messages. The object must be in the format specified in the example below.

Example

const fastify = require('fastify')

const myCustomMessages = {
  badRequestErrorMessage: 'Format is Authorization: Bearer [token]',
  noAuthorizationInHeaderMessage: 'Autorization header is missing!',
  authorizationTokenExpiredMessage: 'Authorization token expired',
  // for the below message you can pass a sync function that must return a string as shown or a string
  authorizationTokenInvalid: (err) => {
    return `Authorization token is invalid: ${err.message}`
  }
}

fastify.register(require('fastify-jwt'), {
  secret: 'supersecret',
  messages: myCustomMessages
})

decode

• complete: Return an object with the decoded header, payload, signature and input (the token part before the signature), instead of just the content of the payload. Default is false.
• checkTyp: When validating the decoded header, setting this option forces the check of the typ property against this value. Example: checkTyp: 'JWT'. Default is undefined.

sign

• key: A string or a buffer containing the secret for HS* algorithms or the PEM encoded public key for RS*, PS*, ES* and EdDSA algorithms. The key can also be a function accepting a Node style callback or a function returning a promise. If provided, it will override the value of secret provided in the options.

• algorithm: The algorithm to use to sign the token. The default is autodetected from the key, using RS256 for RSA private keys, HS256 for plain secrets and the correspondent ES or EdDSA algorithms for EC or Ed* private keys.

• mutatePayload: If set to true, the original payload will be modified in place (via Object.assign) by the signing function. This is useful if you need a raw reference to the payload after claims have been applied to it but before it has been encoded into a token.

• expiresIn: Time span after which the token expires, added as the exp claim in the payload. It is expressed in seconds or a string describing a time span (E.g.: 60, "2 days", "10h", "7d"). A numeric value is interpreted as a seconds count. If you use a string be sure you provide the time units (days, hours, etc.), otherwise milliseconds unit is used by default ("120" is equal to "120ms"). This will override any existing value in the claim.

• notBefore: Time span before the token is active, added as the nbf claim in the payload. It is expressed in seconds or a string describing a time span (E.g.: 60, "2 days", "10h", "7d"). A numeric value is interpreted as a seconds count. If you use a string be sure you provide the time units (days, hours, etc.), otherwise milliseconds unit is used by default ("120" is equal to "120ms"). This will override any existing value in the claim.

• ... the rest of the sign options can be found here.

verify

• key: A string or a buffer containing the secret for HS* algorithms or the PEM encoded public key for RS*, PS*, ES* and EdDSA algorithms. The key can also be a function accepting a Node style callback or a function returning a promise. If provided, it will override the value of secret provided in the options.
• algorithms: List of strings with the names of the allowed algorithms. By default, all algorithms are accepted.
• complete: Return an object with the decoded header, payload, signature and input (the token part before the signature), instead of just the content of the payload. Default is false.
• cache: A positive number specifying the size of the verified tokens cache (using LRU strategy). Setting this to true is equivalent to provide the size 1000. When enabled the performance is dramatically improved. By default the cache is disabled.
• cacheTTL: The maximum time to live of a cache entry (in milliseconds). If the token has a earlier expiration or the verifier has a shorter maxAge, the earlier takes precedence. The default is 600000, which is 10 minutes.
• maxAge: The maximum allowed age for tokens to still be valid. It is expressed in seconds or a string describing a time span (E.g.: 60, "2 days", "10h", "7d"). A numeric value is interpreted as a seconds count. If you use a string be sure you provide the time units (days, hours, etc.), otherwise milliseconds unit is used by default ("120" is equal to "120ms"). By default this is not checked.
• ... the rest of the verify options can be found here.

API Spec

fastify.jwt.sign(payload [,options] [,callback])

This method is used to sign the provided payload. It returns the token. The payload must be an Object. Can be used asynchronously by passing a callback function; synchronously without a callback. options must be an Object and can contain sign options.

fastify.jwt.verify(token, [,options] [,callback])

This method is used to verify provided token. It accepts a token (as Buffer or a string) and returns the payload or the sections of the token. Can be used asynchronously by passing a callback function; synchronously without a callback. options must be an Object and can contain verify options.

Example

const token = fastify.jwt.sign({ foo: 'bar' })
// synchronously
const decoded = fastify.jwt.verify(token)
// asycnhronously
fastify.jwt.verify(token, (err, decoded) => {
  if (err) fastify.log.error(err)
  fastify.log.info(`Token verified. Foo is ${decoded.foo}`)
})

fastify.jwt.decode(token [,options])

This method is used to decode the provided token. It accepts a token (as a Buffer or a string) and returns the payload or the sections of the token. options must be an Object and can contain decode options. Can only be used synchronously.

Example

const token = fastify.jwt.sign({ foo: 'bar' })
const decoded = fastify.jwt.decode(token)
fastify.log.info(`Decoded JWT: ${decoded}`)

fastify.jwt.options

For your convenience, the decode, sign, verify and messages options you specify during .register are made available via fastify.jwt.options that will return an object { decode, sign, verify, messages } containing your options.

Example

const { readFileSync } = require('fs')
const path = require('path')
const fastify = require('fastify')()
const jwt = require('fastify-jwt')
fastify.register(jwt, {
  secret: {
    private: readFileSync(`${path.join(__dirname, 'certs')}/private.key`),
    public: readFileSync(`${path.join(__dirname, 'certs')}/public.key`)
  },
  sign: {
    algorithm: 'RS256',
    aud: 'foo',
    iss: 'example.tld'
  },
  verify: {
    allowedAud: 'foo',
    allowedIss: 'example.tld',
  }
})

fastify.get('/', (request, reply) => {
  const globalOptions = fastify.jwt.options

  // We recommend that you clone the options like this when you need to mutate them
  // modifiedVerifyOptions = { audience: 'foo', issuer: 'example.tld' }
  let modifiedVerifyOptions = Object.assign({}, fastify.jwt.options.verify)
  modifiedVerifyOptions.allowedAud = 'bar'
  modifiedVerifyOptions.allowedSub = 'test'

  return { globalOptions, modifiedVerifyOptions }
  /**
   * Will return :
   * {
   *   globalOptions: {
   *     decode: {},
   *     sign: {
   *       algorithm: 'RS256',
   *       aud: 'foo',
   *       iss: 'example.tld'
   *     },
   *     verify: {
   *       allowedAud: 'foo',
   *       allowedIss: 'example.tld'
   *     }
   *   },
   *   modifiedVerifyOptions: {
   *     allowedAud: 'bar',
   *     allowedIss: 'example.tld',
   *     allowedSub: 'test'
   *   }
   * }
   */
})

fastify.listen(3000, err => {
  if (err) throw err
})

fastify.jwt.cookie

For your convenience, request.jwtVerify() will look for the token in the cookies property of the decorated request. You must specify cookieName. Refer to the cookie example to see sample usage and important caveats.

reply.jwtSign(payload, [options,] callback)

options must be an Object and can contain sign options.

request.jwtVerify([options,] callback)

options must be an Object and can contain verify and decode options.

request.jwtDecode([options,] callback)

Decode a JWT without verifying

As of 3.2.0, decorated when options.jwtDecode is truthy. Will become non-conditionally decorated in 4.0.0. This avoid breaking change that would effect fastify-auth0-verify.

options must be an Object and can contain verify and decode options.

Algorithms supported

The following algorithms are currently supported by fast-jwt that is internally used by fastify-jwt.

Name	Description
none	Empty algorithm - The token signature section will be empty
HS256	HMAC using SHA-256 hash algorithm
HS384	HMAC using SHA-384 hash algorithm
HS512	HMAC using SHA-512 hash algorithm
ES256	ECDSA using P-256 curve and SHA-256 hash algorithm
ES384	ECDSA using P-384 curve and SHA-384 hash algorithm
ES512	ECDSA using P-521 curve and SHA-512 hash algorithm
RS256	RSASSA-PKCS1-v1_5 using SHA-256 hash algorithm
RS384	RSASSA-PKCS1-v1_5 using SHA-384 hash algorithm
RS512	RSASSA-PKCS1-v1_5 using SHA-512 hash algorithm
PS256	RSASSA-PSS using SHA-256 hash algorithm
PS384	RSASSA-PSS using SHA-384 hash algorithm
PS512	RSASSA-PSS using SHA-512 hash algorithm
EdDSA	EdDSA tokens using Ed25519 or Ed448 keys, only supported on Node.js 12+

You can find the list here.

Examples

Certificates Generation

Here some example on how to generate certificates and use them, with or without passphrase.

Signing and verifying (jwtSign, jwtVerify)

const fastify = require('fastify')()
const jwt = require('fastify-jwt')
const request = require('request')

fastify.register(jwt, {
  secret: function (request, reply, callback) {
    // do something
    callback(null, 'supersecret')
  }
})

fastify.post('/sign', function (request, reply) {
  reply.jwtSign(request.body.payload, function (err, token) {
    return reply.send(err || { 'token': token })
  })
})

fastify.get('/verify', function (request, reply) {
  request.jwtVerify(function (err, decoded) {
    return reply.send(err || decoded)
  })
})

fastify.listen(3000, function (err) {
  if (err) fastify.log.error(err)
  fastify.log.info(`Server live on port: ${fastify.server.address().port}`)

  // sign payload and get JWT
  request({
    method: 'POST',
    headers: {
      'Content-Type': 'application/json'
    },
    body: {
      payload: {
        foo: 'bar'
      }
    },
    uri: `http://localhost:${fastify.server.address().port}/sign`,
    json: true
  }, function (err, response, body) {
    if (err) fastify.log.error(err)
    fastify.log.info(`JWT token is ${body.token}`)

    // verify JWT
    request({
      method: 'GET',
      headers: {
        'Content-Type': 'application/json',
        authorization: 'Bearer ' + body.token
      },
      uri: 'http://localhost:' + fastify.server.address().port + '/verify',
      json: true
    }, function (err, response, body) {
      if (err) fastify.log.error(err)
      fastify.log.info(`JWT verified. Foo is ${body.foo}`)
    })
  })
})

Verifying with JWKS

The following example integrates the get-jwks package to fetch a JWKS and verify a JWT against a valid public JWK.

Example

const Fastify = require('fastify')
const fjwt = require('fastify-jwt')
const buildGetJwks = require('get-jwks')

const fastify = Fastify()
const getJwks = buildGetJwks()

fastify.register(fjwt, {
  decode: { complete: true },
  secret: (request, token) => {
    const { header: { kid, alg }, payload: { iss } } = token
    return getJwks.getPublicKey({ kid, domain: iss, alg })
  }
})

fastify.addHook('onRequest', async (request, reply) => {
  try {
    await request.jwtVerify()
  } catch (err) {
    reply.send(err)
  }
})

fastify.listen(3000)

TypeScript

This plugin has two available exports, the default plugin function fastifyJwt and the plugin options object FastifyJWTOptions.

Import them like so:

import fastifyJwt, { FastifyJWTOptions } from 'fastify-jwt'

Define custom Payload Type

typescript declaration merging

// fastify-jwt.d.ts
import "fastify-jwt"

declare module "fastify-jwt" {
  interface FastifyJWT {
    payload: { name: string }
  }
}

// index.ts
fastify.get('/', async (request, replay) => {
  request.user.name // string

  const token = await replay.jwtSign({
    name: 123
    // ^ Type 'number' is not assignable to type 'string'.
  });
})

Acknowledgements

This project is kindly sponsored by:

• LetzDoIt

License

Licensed under MIT.