Production: Hardening OpenKAT

Hardening is making your environment secure. The default installation of OpenKAT is suitable for local use. If you are installing the software in a production environment, make sure you are running a secure configuration. The following modifications are a first step:


Django uses the DJANGO_ALLOWED_HOSTS setting to determine which host/domain names it can serve. This is a security measure to prevent HTTP Host header attacks, which are possible even under many seemingly-safe web server configurations.

The default value for this setting is *, which allows all hosts. You should always set this to the domain and subdomain names that your application uses. For example, if your application is available at and, you should set DJANGO_ALLOWED_HOSTS to, (comma separated).

See the Django ALLOWED_HOSTS documentation for more information. Note that the KAT setting (environment variable) is named DJANGO_ALLOWED_HOSTS and its values are separated by commas.


Django uses the DJANGO_CSRF_TRUSTED_ORIGINS setting to determine which hosts are trusted origins for unsafe requests (e.g. POST). For requests that include the Origin header, Django’s CSRF protection requires that the origin host be in this list.

The default value for this setting is empty. You should always set this to your own host names, prefixed with https:// (or http:// for insecure requests). For example, if your application is available at and, you should set DJANGO_CSRF_TRUSTED_ORIGINS to, (comma separated).

See the Django CSRF_TRUSTED_ORIGINS documentation for more information. Note that the KAT setting (environment variable) is named DJANGO_CSRF_TRUSTED_ORIGINS and its values are separated by commas.

Security headers

Rocky expects a reverse proxy that can handle TLS. This is a good place to set the security headers:








default-src ‘self’; object-src ‘none’; child-src ‘self’; frame-ancestors ‘none’; upgrade-insecure-requests; block-all-mixed-content






“cache”,”cookies”,”storage” (Opt. bij reverse NGINX proxies, “cookies” weglaten

Cross-Origin-Embedder-Policy (COEP)


Cross-Origin-Opener-Policy (COOP)


Cross-Origin-Resource-Policy (CORP)



accelerometer=(),autoplay=(),camera=(), display-capture=(),document-domain=(), encrypted-media=(),fullscreen=(), geolocation=(), gyroscope=(), magnetometer=(), microphone=(), midi=(), payment=(), picture-in-picture=(), publickey-credentials-get=(), screen-wake-lock=(),sync-xhr=(self), usb=(),web-share=(), xr-spatial-tracking=()


no-store, max-age=0


max-age=86400, enforce

SSL/TLS on nginx

Use the following versions and settings for SSL/TLS on nginx:

  • ssl_protocols TLSv1.2 TLSv1.3; # Dropping SSLv3, ref: POODLE


  • ssl_ecdh_curve secp384r1; # Requires nginx >= 1.1.0

  • ssl_session_tickets off; # Requires nginx >= 1.5.9

  • ssl_stapling on; # Requires nginx >= 1.3.7

  • ssl_stapling_verify on; # Requires nginx => 1.3.7

  • ssl_prefer_server_ciphers on;

  • ssl_session_timeout 10m;

  • ssl_session_cache shared:SSL:10m;

Optional use of HSTS, including for subdomains.

add_header Strict-Transport-Security "max-age=31104000;" always;

Obscuring errors to the clients

By default, errors in OpenKAT are visible to the user. The reverse proxy can restrict this and return a generic error message.

proxy_intercept_errors on; error_page 500 502 503 504 /error.html;

In addition, it makes sense to prevent the proxy itself from sending its version along with each response:

server_tokens off;

Web Application Firewall

Installing KAT (rocky) behind a WAF provides an additional layer of security. Modsecurity, which is part of the reverse proxy, can be used for this purpose. More information can be found on the project’s Github page:

Continue reading

Much more information is available on this topic. When applying OpenKAT in a production environment, the following links offer a first step: