hsts

What is hsts?

The 'hsts' npm package is used to set the HTTP Strict Transport Security (HSTS) header in web applications. This header is used to enforce secure (HTTP over SSL/TLS) connections to the server.

What are hsts's main functionalities?

Basic HSTS Header Setup

This code sets up a basic Express server and uses the 'hsts' middleware to set the HSTS header with a max age of 1 year (31536000 seconds).

const hsts = require('hsts');
const express = require('express');
const app = express();

app.use(hsts({ maxAge: 31536000 })); // 1 year in seconds

app.get('/', (req, res) => {
  res.send('Hello, world!');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

HSTS with Subdomains

This code sets the HSTS header to include subdomains by setting the 'includeSubDomains' option to true.

const hsts = require('hsts');
const express = require('express');
const app = express();

app.use(hsts({ maxAge: 31536000, includeSubDomains: true }));

app.get('/', (req, res) => {
  res.send('Hello, world!');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

HSTS with Preload

This code sets the HSTS header with the 'preload' option, which allows the domain to be included in browsers' HSTS preload lists.

const hsts = require('hsts');
const express = require('express');
const app = express();

app.use(hsts({ maxAge: 31536000, preload: true }));

app.get('/', (req, res) => {
  res.send('Hello, world!');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Other packages similar to hsts

helmet

Helmet is a comprehensive security middleware for Express applications. It includes various security headers, including HSTS, making it a more feature-rich alternative to the 'hsts' package. Helmet can be used to set multiple security headers with a single middleware.

README

HTTP Strict Transport Security middleware

This middleware adds the Strict-Transport-Security header to the response. This tells browsers, "hey, only use HTTPS for the next period of time". (See the spec for more.) Note that the header won't tell users on HTTP to switch to HTTPS, it will just tell HTTPS users to stick around. You can enforce HTTPS with the express-enforces-ssl module.

This will set the Strict Transport Security header, telling browsers to visit by HTTPS for the next 180 days:

const hsts = require('hsts')

app.use(hsts({
  maxAge: 15552000  // 180 days in seconds
}))
// Strict-Transport-Security: max-age: 15552000; includeSubDomains

Note that the max age must be in seconds. This was different in previous versions of this module!

The includeSubDomains directive is present by default. If this header is set on example.com, supported browsers will also use HTTPS on my-subdomain.example.com. You can disable this:

app.use(hsts({
  maxAge: 15552000,
  includeSubDomains: false
}))

Some browsers let you submit your site's HSTS to be baked into the browser. You can add preload to the header with the following code. You can check your eligibility and submit your site at hstspreload.org.

app.use(hsts({
  maxAge: 31536000,        // Must be at least 1 year to be approved
  includeSubDomains: true, // Must be enabled to be approved
  preload: true
}))

This header will always be set because the header is ignored in insecure HTTP. You may wish to set it conditionally:

const hstsMiddleware = hsts({
  maxAge: 1234000
})

app.use((req, res, next) => {
  if (req.secure) {
    hstsMiddleware(req, res, next)
  } else {
    next()
  }
})

This header is somewhat well-supported by browsers.