@fastify/helmet

Important security headers for Fastify. It is a tiny wrapper around helmet.

Install

npm i @fastify/helmet

Compatibility

Plugin version	Fastify version
^12.x	^5.x
^9.x	^4.x
^7.x	^3.x
^1.x	^2.x
^1.x	^1.x

Please note that if a Fastify version is out of support, then so are the corresponding versions of this plugin in the table above. See Fastify's LTS policy for more details.

Usage

Simply require this plugin, and the basic security headers will be set.

const fastify = require('fastify')()
const helmet = require('@fastify/helmet')

fastify.register(
  helmet,
  // Example disables the `contentSecurityPolicy` middleware but keeps the rest.
  { contentSecurityPolicy: false }
)

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

How it works

@fastify/helmet is a tiny wrapper around helmet that adds an 'onRequest' hook and a reply.helmet decorator.

It accepts the same options as helmet, and you can see more in the helmet documentation.

Apply Helmet to all your application routes

By passing { global: true } into the options, @fastify/helmet allows you to register Helmet for all your application routes by default. If you want a more granular control on how to apply Helmet to your application you can choose to disable it on a global scope by passing { global: false } to the options. By default, this option is set to true.

Example - enable @fastify/helmet globally

fastify.register(helmet)
// or
fastify.register(helmet, { global: true })

Example - disable @fastify/helmet globally

// register the package with the `{ global: false }` option
fastify.register(helmet, { global: false })

fastify.get('/route-with-disabled-helmet', async (request, reply) => {
  return { message: 'helmet is not enabled here' }
})

fastify.get('/route-with-enabled-helmet', {
  // We enable and configure helmet for this route only
  helmet: {
    dnsPrefetchControl: {
      allow: true
    },
    frameguard: {
      action: 'foo'
    },
    referrerPolicy: false
  }
}, async (request, reply) => {
  return { message: 'helmet is enabled here' }
})

// helmet is disabled on this route but we have access to `reply.helmet` decorator
// that allows us to apply helmet conditionally
fastify.get('/here-we-use-helmet-reply-decorator', async (request, reply) => {
  if (condition) {
    // we apply the default options
    await reply.helmet()
  } else {
    // we apply customized options
    await reply.helmet({ frameguard: false })
  }

  return {
    message: 'we use the helmet reply decorator to conditionally apply helmet middlewares'
  }
})

helmet route option

@fastify/helmet allows you to enable, disable, and customize helmet for each one of your application hooks by using the helmet shorthand route option when you register your application routes.

If you want to disable helmet for a specific endpoint you must pass { helmet: false } to your route options.

If you want to enable or customize helmet for a specific endpoint you must pass a helmet configuration object to your route options. E.g.: { helmet: { frameguard: false } }.

Example - @fastify/helmet configuration using the helmet shorthand route option

// register the package with the `{ global: true }` option
fastify.register(helmet, { global: true })

fastify.get('/route-with-disabled-helmet', { helmet: false }, async (request, reply) => {
  return { message: 'helmet is not enabled here' }
})

fastify.get('/route-with-enabled-helmet', async (request, reply) => {
  return { message: 'helmet is enabled by default here' }
})

fastify.get('/route-with-custom-helmet-configuration', {
  // We change the helmet configuration for this route only
  helmet: {
    enableCSPNonces: true,
    contentSecurityPolicy: {
      directives: {
        'directive-1': ['foo', 'bar']
      },
      reportOnly: true
    },
    dnsPrefetchControl: {
      allow: true
    },
    frameguard: {
      action: 'foo'
    },
    hsts: {
      maxAge: 1,
      includeSubDomains: true,
      preload: true
    },
    permittedCrossDomainPolicies: {
      permittedPolicies: 'foo'
    },
    referrerPolicy: false
  }
}, async (request, reply) => {
  return { message: 'helmet is enabled with a custom configuration on this route' }
})

Content-Security-Policy Nonce

@fastify/helmet provide a simple way for csp nonces generation. You can enable this behavior by passing { enableCSPNonces: true } into the options. Then, you can retrieve the nonces through reply.cspNonce.

Note: This feature is implemented inside this module. It is not a valid option or supported by helmet. If you need to use helmet feature only for csp nonce you can follow the example here.

Example - Generate by options

fastify.register(
  helmet,
  // enable csp nonces generation with default content-security-policy option
  { enableCSPNonces: true }
)

fastify.register(
  helmet,
  // customize content security policy with nonce generation
  {
    enableCSPNonces: true,
    contentSecurityPolicy: {
      directives: {
        ...
      }
    }
  }
)

fastify.get('/', function(request, reply) {
  // retrieve script nonce
  reply.cspNonce.script
  // retrieve style nonce
  reply.cspNonce.style
})

Example - Generate by helmet

fastify.register(
  helmet,
  {
    contentSecurityPolicy: {
      directives: {
        defaultSrc: ["'self'"],
        scriptSrc: [
          function (req, res) {
            // "res" here is actually "reply.raw" in fastify
            res.scriptNonce = crypto.randomBytes(16).toString('hex')
            // make sure to return nonce-... directive to helmet, so it can be sent in the headers
            return `'nonce-${res.scriptNonce}'`
          }
        ],
        styleSrc: [
          function (req, res) {
            // "res" here is actually "reply.raw" in fastify
            res.styleNonce = crypto.randomBytes(16).toString('hex')
            // make sure to return nonce-... directive to helmet, so it can be sent in the headers
            return `'nonce-${res.styleNonce}'`
          }
        ]
      }
    }
  }
)

fastify.get('/', function(request, reply) {
  // you can access the generated nonce by "reply.raw"
  reply.raw.scriptNonce
  reply.raw.styleNonce
})

Disable Default helmet Directives

By default, helmet will add a default set of CSP directives to the response. This behavior can be disabled by setting useDefaults: false in the contentSecurityPolicy configuration.

fastify.register(
  helmet,
  {
    contentSecurityPolicy: {
      useDefaults: false,
      directives: {
        'default-src': ["'self'"]
      }
    }
  }
)

License

Licensed under MIT.