Helmet

Helmet can help protect your app from some well-known web vulnerabilities by setting HTTP headers appropriately. Generally, Helmet is just a collection of 14 smaller middleware functions that set security-related HTTP headers (read more).

Hint Note that applying helmet as global or registering it must come before other calls to app.use() or setup functions that may call app.use(). This is due to the way the underlying platform (i.e., Express or Fastify) works, where the order that middleware/routes are defined matters. If you use middleware like helmet or cors after you define a route, then that middleware will not apply to that route, it will only apply to middleware defined after the route.

Use with Express (default)#

Start by installing the required package.

$ npm i --save helmet

Once the installation is complete, apply it as a global middleware.

import * as helmet from 'helmet';
// somewhere in your initialization file
app.use(helmet());

Hint If you are getting the This expression is not callable error while trying to import Helmet, you very likely have the allowSyntheticDefaultImports and esModuleInterop options set to true in your project's tsconfig.json file. If that's the case, change the import statement to: import helmet from 'helmet' instead.

Use with Fastify#

If you are using the FastifyAdapter, install the fastify-helmet package:

$ npm i --save fastify-helmet

fastify-helmet should not be used as a middleware, but as a Fastify plugin, i.e., by using app.register():

import { fastifyHelmet } from 'fastify-helmet';
// somewhere in your initialization file
await app.register(fastifyHelmet);

Warning When using apollo-server-fastify and fastify-helmet, there may be a problem with CSP on the GraphQL playground, to solve this collision, configure the CSP as shown below:

await app.register(fastifyHelmet, {
  contentSecurityPolicy: {
    directives: {
      defaultSrc: [`'self'`],
      styleSrc: [`'self'`, `'unsafe-inline'`, 'cdn.jsdelivr.net', 'fonts.googleapis.com'],
      fontSrc: [`'self'`, 'fonts.gstatic.com'],
      imgSrc: [`'self'`, 'data:', 'cdn.jsdelivr.net'],
      scriptSrc: [`'self'`, `https: 'unsafe-inline'`, `cdn.jsdelivr.net`],
    },
  },
});

// If you are not going to use CSP at all, you can use this:
await app.register(fastifyHelmet, {
  contentSecurityPolicy: false,
});