@fastify/helmet

Important security headers for Fastify, using helmet.

Install

npm i @fastify/helmet

Compatibility

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 to set basic security headers.

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 wrapper around helmet that adds an 'onRequest' hook and a reply.helmet decorator.

It accepts the same options as helmet. See helmet documentation.

Apply Helmet to all routes

Pass { global: true } to register Helmet for all routes. For granular control, pass { global: false } to disable it at a global scope. Default is 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 enabling, disabling, and customizing helmet for each route using the helmet shorthand option when registering routes.

To disable helmet for a specific endpoint, pass { helmet: false } to the route options.

To enable or customize helmet for a specific endpoint, pass a configuration object to 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 also allows CSP nonce generation, which can be enabled by passing { enableCSPNonces: true } into the options. Retrieve the nonces through reply.cspNonce.

ℹ️ Note: This feature is implemented by this module and is not supported by helmet. For using helmet only for csp nonces, see example.

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) {
  // access the generated nonce by "reply.raw"
  reply.raw.scriptNonce
  reply.raw.styleNonce
})

Disable Default helmet Directives

By default, helmet adds a default set of CSP directives to the response. Disable this by setting useDefaults: false in the contentSecurityPolicy configuration.

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

License

Licensed under MIT.