Secure Headers Middleware

Secure Headers Middleware simplifies the setup of security headers. Inspired in part by the capabilities of Helmet, it allows you to control the activation and deactivation of specific security headers.

Import

import { Hono } from 'hono'
import { secureHeaders } from 'hono/secure-headers'

Usage

You can use the optimal settings by default.

const app = new Hono()
app.use(secureHeaders())

You can suppress unnecessary headers by setting them to false.

const app = new Hono()
app.use(
  '*',
  secureHeaders({
    xFrameOptions: false,
    xXssProtection: false,
  })
)

You can override default header values using a string.

const app = new Hono()
app.use(
  '*',
  secureHeaders({
    strictTransportSecurity: 'max-age=63072000; includeSubDomains; preload',
    xFrameOptions: 'DENY',
    xXssProtection: '1',
  })
)

Supported Options

Each option corresponds to the following Header Key-Value pairs.

Option	Header	Value	Default
-	X-Powered-By	(Delete Header)	True
contentSecurityPolicy	Content-Security-Policy	Usage: Setting Content-Security-Policy	No Setting
crossOriginEmbedderPolicy	Cross-Origin-Embedder-Policy	require-corp	False
crossOriginResourcePolicy	Cross-Origin-Resource-Policy	same-origin	True
crossOriginOpenerPolicy	Cross-Origin-Opener-Policy	same-origin	True
originAgentCluster	Origin-Agent-Cluster	?1	True
referrerPolicy	Referrer-Policy	no-referrer	True
reportingEndpoints	Reporting-Endpoints	Usage: Setting Content-Security-Policy	No Setting
reportTo	Report-To	Usage: Setting Content-Security-Policy	No Setting
strictTransportSecurity	Strict-Transport-Security	max-age=15552000; includeSubDomains	True
xContentTypeOptions	X-Content-Type-Options	nosniff	True
xDnsPrefetchControl	X-DNS-Prefetch-Control	off	True
xDownloadOptions	X-Download-Options	noopen	True
xFrameOptions	X-Frame-Options	SAMEORIGIN	True
xPermittedCrossDomainPolicies	X-Permitted-Cross-Domain-Policies	none	True
xXssProtection	X-XSS-Protection	0	True

Middleware Conflict

Please be cautious about the order of specification when dealing with middleware that manipulates the same header.

In this case, Secure-headers operates and the x-powered-by is removed:

const app = new Hono()
app.use(secureHeaders())
app.use(poweredBy())

In this case, Powered-By operates and the x-powered-by is added:

const app = new Hono()
app.use(poweredBy())
app.use(secureHeaders())

Setting Content-Security-Policy

const app = new Hono()
app.use(
  '/test',
  secureHeaders({
    reportingEndpoints: [
      {
        name: 'endpoint-1',
        url: 'https://example.com/reports',
      },
    ],
    // -- or alternatively
    // reportTo: [
    //   {
    //     group: 'endpoint-1',
    //     max_age: 10886400,
    //     endpoints: [{ url: 'https://example.com/reports' }],
    //   },
    // ],
    contentSecurityPolicy: {
      defaultSrc: ["'self'"],
      baseUri: ["'self'"],
      childSrc: ["'self'"],
      connectSrc: ["'self'"],
      fontSrc: ["'self'", 'https:', 'data:'],
      formAction: ["'self'"],
      frameAncestors: ["'self'"],
      frameSrc: ["'self'"],
      imgSrc: ["'self'", 'data:'],
      manifestSrc: ["'self'"],
      mediaSrc: ["'self'"],
      objectSrc: ["'none'"],
      reportTo: 'endpoint-1',
      sandbox: ['allow-same-origin', 'allow-scripts'],
      scriptSrc: ["'self'"],
      scriptSrcAttr: ["'none'"],
      scriptSrcElem: ["'self'"],
      styleSrc: ["'self'", 'https:', "'unsafe-inline'"],
      styleSrcAttr: ['none'],
      styleSrcElem: ["'self'", 'https:', "'unsafe-inline'"],
      upgradeInsecureRequests: [],
      workerSrc: ["'self'"],
    },
  })
)

nonce attribute

You can add a nonce attribute to a script or style element by adding the NONCE imported from hono/secure-headers to a scriptSrc or styleSrc:

import { secureHeaders, NONCE } from 'hono/secure-headers'
import type { SecureHeadersVariables } from 'hono/secure-headers'

// Specify the variable types to infer the `c.get('secureHeadersNonce')`:
type Variables = SecureHeadersVariables

const app = new Hono<{ Variables: Variables }>()

// Set the pre-defined nonce value to `scriptSrc`:
app.get(
  '*',
  secureHeaders({
    contentSecurityPolicy: {
      scriptSrc: [NONCE, 'https://allowed1.example.com'],
    },
  })
)

// Get the value from `c.get('secureHeadersNonce')`:
app.get('/', (c) => {
  return c.html(
    <html>
      <body>
        {/** contents */}
        <script src='/js/client.js' nonce={c.get('secureHeadersNonce')} />
      </body>
    </html>
  )
})

If you want to generate the nonce value yourself, you can also specify a function as the following:

const app = new Hono<{
  Variables: { myNonce: string }
}>()

const myNonceGenerator: ContentSecurityPolicyOptionHandler = (c) => {
  // This function is called on every request.
  const nonce = Math.random().toString(36).slice(2)
  c.set('myNonce', nonce)
  return `'nonce-${nonce}'`
}

app.get(
  '*',
  secureHeaders({
    contentSecurityPolicy: {
      scriptSrc: [myNonceGenerator, 'https://allowed1.example.com'],
    },
  })
)

app.get('/', (c) => {
  return c.html(
    <html>
      <body>
        {/** contents */}
        <script src='/js/client.js' nonce={c.get('myNonce')} />
      </body>
    </html>
  )
})