How to enable HSTS for Apache

HSTS or HTTP Strict Transport Security provides an extra layer of security for HTTPS (SSL / TLS) traffic by preventing the connection to be downgraded to HTTP, which is not encrypted.

HSTS can be enabled in Apache by enabling the headers module with some specific configurations.

1. Launch terminal application.
2. Enable headers module for Apache.

   $ sudo a2enmod headers # Ubuntu, Debian and SUSE variants
   Enabling module headers.
   To activate the new configuration, you need to run:
     systemctl restart apache2

   • Distribution with a2enmod support can simply run the command above without having to manually enable the required modules.
   • CentOS and Red Hat enables the module by default so requires no manual action to enable the modules.

   Related: How to enable or disable Apache modules

   Options	Debian, Ubuntu	openSUSE and SLES	Fedora Core, CentOS, RHEL	macOS	homebrew	xampp
   a2enmod support	yes	yes	no	no	no	no
   Modules to install	none
   Module name	n/a			headers
   Loadmodule directive	n/a			LoadModule headers_module <module_locations>/mod_headers.so

3. Add relevant Header directive in virtual server configuration.

   <VirtualHost *:443>
           # .....
           # ....
           Header always set Strict-Transport-Security "max-age=15552000; includeSubDomains"
   </VirtualHost>

   Related: Location for Apache VirtualHost configuration

   Related: Options for configuring HTTP headers in Apache

4. Restart Apache service for the changes to take effect.

   $ sudo systemctl restart apache2 # Ubuntu and Debian
   $ sudo systemctl restart httpd # CentOS and Red Hat

   Related: How to start, restart and stop Apache service

5. Test by accessing the service using curl.

   $ curl --head https://www.facebook.com
   HTTP/2 200
   set-cookie: fr=1kSvv492E5q1inyhV..BeSNo2.VF.AAA.0.0.BeSNo2.AWXv6Ptp; expires=Sat, 16-May-2020 05:59:17 GMT; Max-Age=7775999; path=/; domain=.facebook.com; secure; httponly
   set-cookie: sb=NtpIXuU2eriH34nD6VfGz_em; expires=Tue, 15-Feb-2022 05:59:18 GMT; Max-Age=63072000; path=/; domain=.facebook.com; secure; httponly
   cache-control: private, no-cache, no-store, must-revalidate
   pragma: no-cache
   strict-transport-security: max-age=15552000; preload
   vary: Accept-Encoding
   x-content-type-options: nosniff
   x-frame-options: DENY
   x-xss-protection: 0
   expires: Sat, 01 Jan 2000 00:00:00 GMT
   content-type: text/html; charset="utf-8"
   x-fb-debug: vMujBKiilKcPMV/+nHPJ1hc1edb5y08fSxdhwLel5lsiXHrqfWR9JNW1FX9y7lFivSJF+rhA6HOM77cSFuODaw==
   date: Sun, 16 Feb 2020 05:59:18 GMT
   alt-svc: h3-24=":443"; ma=3600
   date: Sun, 16 Feb 2020 05:59:18 GMT