What exactly does Let's Encrypt certbot's `enhance` command?

Question

Let's Encrypt certbot have subcommand enhance that has a description "Add security enhancements to your existing configuration".

The only additional information that I can find in certbot's CLI help file is:

enhance: Helps to harden the TLS configuration by adding security enhancements to already existing configuration.

And still it is not clear what enchantments are added to existing configuration. Which files are modified, etc... I am particularly interested in configuration with Ubuntu + Apache HTTP Server (using --apache option).

Without having read exactly what `certbot enhance` does, I would guess what it refers to is TLS configuration similar to what eg https://wiki.mozilla.org/Security/Server_Side_TLS suggests . Maybe run it in some environment and see what it does? — Håkan Lindqvist, Jul 17 '18 at 11:54

Lenniey · Accepted Answer · 2018-07-17T12:14:03.637

I couldn't find it either, so I looked at the source (and another doc) which states:

security:
  Security parameters & server settings

  --rsa-key-size N      Size of the RSA key. (default: 2048)
  --must-staple         Adds the OCSP Must Staple extension to the
                        certificate. Autoconfigures OCSP Stapling for
                        supported setups (Apache version >= 2.3.3 ). (default:
                        False)
  --redirect            Automatically redirect all HTTP traffic to HTTPS for
                        the newly authenticated vhost. (default: Ask)
  --no-redirect         Do not automatically redirect all HTTP traffic to
                        HTTPS for the newly authenticated vhost. (default:
                        Ask)
  --hsts                Add the Strict-Transport-Security header to every HTTP
                        response. Forcing browser to always use SSL for the
                        domain. Defends against SSL Stripping. (default: None)
  --uir                 Add the "Content-Security-Policy: upgrade-insecure-
                        requests" header to every HTTP response. Forcing the
                        browser to use https:// for every http:// resource.
                        (default: None)
  --staple-ocsp         Enables OCSP Stapling. A valid OCSP response is
                        stapled to the certificate that the server offers
                        during TLS. (default: None)
  --strict-permissions  Require that all configuration files are owned by the
                        current user; only needed if your config is somewhere
                        unsafe like /tmp/ (default: False)

and tried it in my testing environment:

certbot --authenticator webroot --installer apache

[...]
Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access.
-------------------------------------------------------------------------------
1: No redirect - Make no further changes to the webserver configuration.
2: Redirect - Make all requests redirect to secure HTTPS access. Choose this for
new sites, or if you're confident your site works on HTTPS. You can undo this
change by editing your web server's configuration.
-------------------------------------------------------------------------------
Select the appropriate number [1-2] then [enter] (press 'c' to cancel):2

Enabled Apache rewrite module
Redirecting vhost in /etc/apache2/sites-enabled/example.conf to ssl vhost in /etc/apache2/sites-enabled/example.ssl.conf

-------------------------------------------------------------------------------
Congratulations! You have successfully enabled https://example.com and https://www.example.com

You should test your configuration at:
https://www.ssllabs.com/ssltest/analyze.html?d=example.com



certbot enhance --hsts

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator None, Installer apache

Which certificate would you like to use to enhance your configuration?
-------------------------------------------------------------------------------
1: example.com
-------------------------------------------------------------------------------
Press 1 [enter] to confirm the selection (press 'c' to cancel):

Which domain names would you like to enable the selected enhancements for?
-------------------------------------------------------------------------------
1: example.com
2: www.example.com
-------------------------------------------------------------------------------
Select the appropriate numbers separated by commas and/or spaces, or leave input
blank to select all options shown (Enter 'c' to cancel):

Adding Strict-Transport-Security header to ssl vhost in /etc/apache2/sites-enabled/example.ssl.conf



certbot enhance --uir

Plugins selected: Authenticator None, Installer apache

Which certificate would you like to use to enhance your configuration?
-------------------------------------------------------------------------------
1: example.com
-------------------------------------------------------------------------------
Press 1 [enter] to confirm the selection (press 'c' to cancel):

Which domain names would you like to enable the selected enhancements for?
-------------------------------------------------------------------------------
1: example.com
2: www.example.com
-------------------------------------------------------------------------------
Select the appropriate numbers separated by commas and/or spaces, or leave input
blank to select all options shown (Enter 'c' to cancel):

Adding Upgrade-Insecure-Requests header to ssl vhost in /etc/apache2/sites-enabled/example.ssl.conf

You can guess the rest of the options (didn't try them all).

It added the following lines to my sites-enabled ssl.conf:

Include /etc/letsencrypt/options-ssl-apache.conf
SSLCertificateFile /etc/letsencrypt/live/example.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/example.com/privkey.pem
Header always set Strict-Transport-Security "max-age=31536000"
Header always set Content-Security-Policy upgrade-insecure-requests

and these in my sites-enabled non-ssl.conf:

RewriteEngine on
RewriteCond %{SERVER_NAME} =www.example.com [OR]
RewriteCond %{SERVER_NAME} =example.com
RewriteRule ^ https://%{SERVER_NAME}%{REQUEST_URI} [END,NE,R=permanent]

What exactly does Let's Encrypt certbot's `enhance` command?

1 Answers1