Evilscaught/fastify-auth

Run multiple auth functions in Fastify

@fastify/auth

This module does not provide an authentication strategy, but it provides a very fast utility to handle authentication (and multiple strategies) in your routes, without adding overhead.
Check out a complete example here.

Install

npm i @fastify/auth

Usage

As said above, @fastify/auth does not provide an authentication strategy, so you must provide authentication strategies yourself, with a decorator or another plugin.

In the following example, you will find a very simple implementation that should help you understand how to use this module:

fastify
  .decorate('verifyJWTandLevel', function (request, reply, done) {
    // your validation logic
    done() // pass an error if the authentication fails
  })
  .decorate('verifyUserAndPassword', function (request, reply, done) {
    // your validation logic
    done() // pass an error if the authentication fails
  })
  .register(require('@fastify/auth'))
  .after(() => {
    fastify.route({
      method: 'POST',
      url: '/auth-multiple',
      preHandler: fastify.auth([
        fastify.verifyJWTandLevel,
        fastify.verifyUserAndPassword
      ]),
      handler: (req, reply) => {
        req.log.info('Auth route')
        reply.send({ hello: 'world' })
      }
    })
  })

The default relationship of these customized authentication strategies is or, while we could also use and:

fastify
  .decorate('verifyAdmin', function (request, reply, done) {
    // your validation logic
    done() // pass an error if the authentication fails
  })
  .decorate('verifyReputation', function (request, reply, done) {
    // your validation logic
    done() // pass an error if the authentication fails
  })
  .register(require('@fastify/auth'))
  .after(() => {
    fastify.route({
      method: 'POST',
      url: '/auth-multiple',
      preHandler: fastify.auth([
        fastify.verifyAdmin,
        fastify.verifyReputation
      ], {
        relation: 'and'
      }),
      handler: (req, reply) => {
        req.log.info('Auth route')
        reply.send({ hello: 'world' })
      }
    })
  })

For more examples, please check example-composited.js

This plugin support callback and Promise returned by the functions. Note that an async function does not have to call the done parameter, otherwise the route handler to which the auth methods are linked to might be called multiple times:

fastify
  .decorate('asyncVerifyJWTandLevel', async function (request, reply) {
    // your async validation logic
    await validation()
    // throws an error if the authentication fails
  })
  .decorate('asyncVerifyUserAndPassword', function (request, reply) {
    // return a promise that throws an error if the authentication fails
    return myPromiseValidation()
  })
  .register(require('@fastify/auth'))
  .after(() => {
    fastify.route({
      method: 'POST',
      url: '/auth-multiple',
      preHandler: fastify.auth([
        fastify.asyncVerifyJWTandLevel,
        fastify.asyncVerifyUserAndPassword
      ]),
      handler: (req, reply) => {
        req.log.info('Auth route')
        reply.send({ hello: 'world' })
      }
    })
  })

Keep in mind that route definition should either be done as a plugin or within an .after() callback. For a complete example implementation, see example.js.

@fastify/auth will run all your authentication methods and your request will continue if at least one succeeds, otherwise it will return an error to the client. Any successful authentication will automatically stop @fastify/auth from trying the rest, unless you provide the run: 'all' parameter:

fastify.route({
  method: 'GET',
  url: '/run-all',
  preHandler: fastify.auth([
    (request, reply, done) => { console.log('executed 1'); done() },
    (request, reply, done) => { console.log('executed 2'); done() },
    (request, reply, done) => { console.log('executed 3'); done(new Error('you are not authenticated')) },
    (request, reply, done) => { console.log('executed 4'); done() },
    (request, reply, done) => { console.log('executed 5'); done(new Error('you shall not pass')) }
  ], { run: 'all' }),
  handler: (req, reply) => { reply.send({ hello: 'world' }) }
})

This example will show all the console logs and will reply always with 401: you are not authenticated. The run parameter is useful if you are adding to the request business data read from auth-tokens.

You can use this plugin on route level as in the above example or on hook level by using the preHandler hook:

fastify.addHook('preHandler', fastify.auth([
  fastify.verifyJWTandLevel,
  fastify.verifyUserAndPassword
]))

fastify.route({
  method: 'POST',
  url: '/auth-multiple',
  handler: (req, reply) => {
    req.log.info('Auth route')
    reply.send({ hello: 'world' })
  }
})

The difference between the two approaches is that if you use the route level preHandler function the authentication will run just for the selected route. Whereas if you use the preHandler hook the authentication will run for all the routes declared inside the current plugin (and its descendants).

Acknowledgements

This project is kindly sponsored by:

• LetzDoIt

License

Licensed under MIT.