How To Secure Nginx with Let's Encrypt on Debian 10
Let’s Encrypt is a Certificate Authority (CA) that provides a straightforward way to obtain and install free TLS/SSL certificates, 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 Nginx on Debian 10 and set up your certificate to renew automatically.
This tutorial will use a separate Nginx server block file instead of the default file. We recommend creating new Nginx server block files for each domain because it helps to avoid common mistakes and maintains the default files as a fallback configuration.
To follow this tutorial, you will need:
- One Debian 10 server, set up by following this initial server setup for Debian 10 tutorial, along with a
sudonon-root user and a firewall.
- A fully registered domain name. 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
your_domainpointing to your server’s public IP address.
- An A record with
www.your_domainpointing to your server’s public IP address.
- An A record with
Step 1 — Installing Certbot
The first step to using Let’s Encrypt to obtain an SSL certificate is to install the Certbot software on your server.
python3-certbot-nginx package from the Debian repositories will allow us to install and use Cerbot’s nginx plugin. Working with Python 3 and the
python3-certbot-nginx package increases the longevity of our setup: Python 2 will be deprecated by January 2020, so our setup ensures compatibility with Python 3. Debian 10 currently supports both Python 2 and Python 3.
Before installing the
python3-certbot-nginx package, update your package list:
- sudo apt update
Next, install the dependencies for the
python3-certbot-nginx package, which include the
- sudo apt install python3-acme python3-certbot python3-mock python3-openssl python3-pkg-resources python3-pyparsing python3-zope.interface
Finally, install the
- sudo apt install python3-certbot-nginx
Certbot is now ready to use, but in order for it to configure SSL for Nginx, we need to verify some of Nginx’s configuration.
Step 2 — Confirming Nginx’s Configuration
Certbot needs to be able to find the correct
server block in your Nginx configuration for it to be able to automatically configure SSL. Specifically, it does this by looking for a
server_name directive that matches your requested domain.
If you followed the server block setup step in the Nginx installation tutorial, you should have a server block for your domain at
/etc/nginx/sites-available/your_domain with the
server_name directive already set appropriately.
To check, open the server block file for your domain using
nano or your favorite text editor:
- sudo nano /etc/nginx/sites-available/your_domain
Find the existing
server_name line. It should look like this:
... server_name your_domain www.your_domain; ...
If it does, exit your editor and move on to the next step.
If it doesn’t, update it to match. Then save the file, quit your editor, and verify the syntax of your configuration edits:
- sudo nginx -t
If you get an error, reopen the server block file and check for any typos or missing characters. Once your configuration file syntax is correct, reload Nginx to load the new configuration:
- sudo systemctl reload nginx
Certbot can now find the correct
server block and update it.
Next, let’s update the firewall to allow HTTPS traffic.
Step 3 — Allowing HTTPS Through the Firewall
If you have the
ufw firewall enabled, as recommended in the prerequisite guides, you’ll need to adjust the settings to allow for HTTPS traffic.
You can see the current setting by typing:
- sudo ufw status
It will probably look like this, meaning that only HTTP traffic is allowed to the web server:
OutputStatus: active To Action From -- ------ ---- OpenSSH ALLOW Anywhere Nginx HTTP ALLOW Anywhere OpenSSH (v6) ALLOW Anywhere (v6) Nginx HTTP (v6) ALLOW Anywhere (v6)
To let in HTTPS traffic, allow the
Nginx Full profile and delete the redundant
Nginx HTTP profile allowance:
- sudo ufw allow 'Nginx Full'
- sudo ufw delete allow 'Nginx HTTP'
Your status should now look like this:
- sudo ufw status
OutputStatus: active To Action From -- ------ ---- OpenSSH ALLOW Anywhere Nginx Full ALLOW Anywhere OpenSSH (v6) ALLOW Anywhere (v6) Nginx Full (v6) ALLOW Anywhere (v6)
Next, let’s run Certbot and fetch our certificates.
Step 4 — Obtaining an SSL Certificate
Certbot provides a variety of ways to obtain SSL certificates through plugins. The Nginx plugin will take care of reconfiguring Nginx and reloading the config whenever necessary. To use this plugin, type the following:
- sudo certbot --nginx -d your_domain -d www.your_domain
certbot with the
--nginx plugin, using
-d to specify the names we’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.
OutputPlease 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 Nginx 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:
OutputIMPORTANT NOTES: - Congratulations! Your certificate and chain have been saved at: /etc/letsencrypt/live/your_domain/fullchain.pem Your key file has been saved at: /etc/letsencrypt/live/your_domain/privkey.pem Your cert will expire on 2019-10-08. 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 — 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
- sudo certbot renew --dry-run
If you see no errors, you’re all set. When necessary, Certbot will renew your certificates and reload Nginx to pick up the changes. If the automated renewal process ever fails, Let’s Encrypt will send a message to the email you specified, warning you when your certificate is about to expire.
In this tutorial, you installed the Let’s Encrypt client
certbot, downloaded SSL certificates for your domain, configured Nginx 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.