Introduction
Let’s Encrypt is a Certificate Authority (CA) that provides an easy way to obtain and install free TLS/SSL certificates, thereby enabling encrypted HTTPS on web servers. It simplifies the process by providing a software client, Certbot, that attempts to automate most (if not all) of the required steps. Currently, the entire process of obtaining and installing a certificate is fully automated on both Apache and Nginx.
In this tutorial, you will use Certbot to obtain a free SSL certificate for Apache on Debian 9 and set up your certificate to renew automatically.
This tutorial will use a separate Apache virtual host file instead of the default configuration file. We recommend creating new Apache virtual host files for each domain because it helps to avoid common mistakes and maintains the default files as a fallback configuration.
Prerequisites
To follow this tutorial, you will need:
-
One Debian 9 server set up by following this initial server setup for Debian 9 tutorial, including a non-root user with
sudo
privileges and a firewall. -
A fully registered domain name. This tutorial will use example.com throughout. You can purchase a domain name on Namecheap, get one for free on Freenom, or use the domain registrar of your choice.
-
Both of the following DNS records set up for your server. You can follow this introduction to DigitalOcean DNS for details on how to add them.
- An A record with
example.com
pointing to your server’s public IP address. - An A record with
www.example.com
pointing to your server’s public IP address.
- An A record with
-
Apache installed by following How To Install Apache on Debian 9. Be sure that you have a virtual host file for your domain. This tutorial will use
/etc/apache2/sites-available/example.com.conf
as an example.
Step 1 ā Installing Certbot
The first step to using Let’s Encrypt to obtain an SSL certificate is to install the Certbot software on your server.
As of this writing, Certbot is not available from the Debian software repositories by default. In order to download the software using apt
, you will need to add the backports repository to your sources.list
file where apt
looks for package sources. Backports are packages from Debianās testing and unstable distributions that are recompiled so they will run without new libraries on stable Debian distributions.
To add the backports repository, open (or create) the sources.list
file in your /etc/apt/
directory:
$ sudo nano /etc/apt/sources.list
At the bottom of the file, add the following line:
. . .
deb http://ftp.debian.org/debian stretch-backports main
This includes the main
packages, which are Debian Free Software Guidelines (DFSG)-compliant, as well as the non-free
and contrib
components, which are either not DFSG-compliant themselves or include dependencies in this category.
Save and close the file by pressing CTRL+X
, Y
, then ENTER
, then update your package lists:
$ sudo apt update
Then install Certbot with the following command. Note that the -t
option tells apt
to search for the package by looking in the backports repository you just added:
$ sudo apt install python-certbot-apache -t stretch-backports
Certbot is now ready to use, but in order for it to configure SSL for Apache, we need to verify that Apache has been configured correctly.
Step 2 ā Setting Up the SSL Certificate
Certbot needs to be able to find the correct virtual host in your Apache configuration for it to automatically configure SSL. Specifically, it does this by looking for a ServerName
directive that matches the domain you request a certificate for.
If you followed the virtual host set up step in the Apache installation tutorial, you should have a VirtualHost
block for your domain at /etc/apache2/sites-available/example.com.conf
with the ServerName
directive already set appropriately.
To check, open the virtual host file for your domain using nano
or your favorite text editor:
$ sudo nano /etc/apache2/sites-available/example.com.conf
Find the existing ServerName
line. It should look like this, with your own domain name instead of example.com
:
...
ServerName example.com;
...
If it doesnāt already, update the ServerName
directive to point to your domain name. Then save the file, quit your editor, and verify the syntax of your configuration edits:
$ sudo apache2ctl configtest
If there aren’t any syntax errors, you will see this output:
Syntax OK
If you get an error, reopen the virtual host file and check for any typos or missing characters. Once your configuration file’s syntax is correct, reload Apache to load the new configuration:
$ sudo systemctl reload apache2
Certbot can now find the correct VirtualHost block and update it.
Next, let’s update the firewall to allow HTTPS traffic.
Step 3 ā Allowing HTTPS Through the Firewall
If you have the ufw
firewall enabled, as recommended by the prerequisite guides, you’ll need to adjust the settings to allow for HTTPS traffic. Luckily, when installed on Debian, ufw
comes packaged with a few profiles that help to simplify the process of changing firewall rules for HTTP and HTTPS traffic.
You can see the current setting by typing:
$ sudo ufw status
If you followed the Step 2 of our guide on How to Install Apache on Debian 9, the output of this command will look like this, showing that only HTTP traffic is allowed to the web server:
Status: active
To Action From
-- ------ ----
OpenSSH ALLOW Anywhere
WWW ALLOW Anywhere
OpenSSH (v6) ALLOW Anywhere (v6)
WWW (v6) ALLOW Anywhere (v6)
To additionally let in HTTPS traffic, allow the āWWW Fullā profile and delete the redundant āWWWā profile allowance:
$ sudo ufw allow 'WWW Full'
$ sudo ufw delete allow 'WWW'
Your status should now look like this:
$ sudo ufw status
Status: active
To Action From
-- ------ ----
OpenSSH ALLOW Anywhere
WWW Full ALLOW Anywhere
OpenSSH (v6) ALLOW Anywhere (v6)
WWW Full (v6) ALLOW Anywhere (v6)
Next, let’s run Certbot and fetch our certificates.
Step 4 ā Obtaining an SSL Certificate
Certbot provides a variety of ways to obtain SSL certificates through plugins. The Apache plugin will take care of reconfiguring Apache and reloading the config whenever necessary. To use this plugin, type the following:
$ sudo certbot --apache -d example.com -d www.example.com
This runs certbot
with the --apache
plugin, using -d
to specify the names you’d like the certificate to be valid for.
If this is your first time running certbot
, you will be prompted to enter an email address and agree to the terms of service. After doing so, certbot
will communicate with the Let’s Encrypt server, then run a challenge to verify that you control the domain you’re requesting a certificate for.
If that’s successful, certbot
will ask how you’d like to configure your HTTPS settings:
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):
Select your choice then hit ENTER
. The configuration will be updated, and Apache will reload to pick up the new settings. certbot
will wrap up with a message telling you the process was successful and where your certificates are stored:
IMPORTANT NOTES:
- Congratulations! Your certificate and chain have been saved at:
/etc/letsencrypt/live/example.com/fullchain.pem
Your key file has been saved at:
/etc/letsencrypt/live/example.com/privkey.pem
Your cert will expire on 2018-12-04. To obtain a new or tweaked
version of this certificate in the future, simply run certbot again
with the "certonly" option. To non-interactively renew *all* of
your certificates, run "certbot renew"
- Your account credentials have been saved in your Certbot
configuration directory at /etc/letsencrypt. You should make a
secure backup of this folder now. This configuration directory will
also contain certificates and private keys obtained by Certbot so
making regular backups of this folder is ideal.
- If you like Certbot, please consider supporting our work by:
Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate
Donating to EFF: https://eff.org/donate-le
Your certificates are downloaded, installed, and loaded. Try reloading your website using https://
and notice your browser’s security indicator. It should indicate that the site is properly secured, usually with a green lock icon. If you test your server using the SSL Labs Server Test, it will get an A grade.
Let’s finish by testing the renewal process.
Step 5 ā Verifying Certbot Auto-Renewal
Let’s Encrypt’s certificates are only valid for ninety days. This is to encourage users to automate their certificate renewal process. The certbot
package we installed takes care of this for us by adding a renew script to /etc/cron.d
. This script runs twice a day and will automatically renew any certificate that’s within thirty days of expiration.
To test the renewal process, you can do a dry run with certbot
:
$ sudo certbot renew --dry-run
If you see no errors, you’re all set. When necessary, Certbot will renew your certificates and reload Apache to pick up the changes. If the automated renewal process ever fails, Letās Encrypt will send a message to the email you specified, warning you when your certificate is about to expire.
Conclusion
In this tutorial, you installed the Let’s Encrypt client certbot
, downloaded SSL certificates for your domain, configured Apache to use these certificates, and set up automatic certificate renewal. If you have further questions about using Certbot, their documentation is a good place to start.
edit: I did NOT write this guide\tutorial. I saved it on my site for own purpose.