Secure Nginx with Let’s Encrypt SSL on CentOS 7

By using Let’s Encrypt you can get a free valid SSL certificate. Let’s Encrypt is the Certificate Authority (CA) which provides free SSL certificate. To get SSL certificate Certbot client is used which fetches and deploys SSL certificate on your server. In this tutorial, you are going to learn how to secure Nginx with Let’s Encrypt SSL on CentOS.

Before we begin

Let’s Encrypt certificate can only be requested from the server the domain is pointing to. Let’s Encrypt checks if the domain is pointed to the current server and if successful, it issues the certificate.

Prerequisites

1. Before you start to secure Nginx with Let’s Encrypt SSL on CentOS 7 using the Certbot client. You must have the non-root user account on your server with sudo privileges.
2. Make it sure your domain is pointing to the current server.

1. Install Certbot Client

To install Certbot client you need to add EPEL reposiory, to do so type:

sudo yum install epel-release

Now install Certbot client by executing following command

sudo yum install httpd mod_ssl python-certbot-nginx

Confirm the installation by typing

certbot --version

2. Setup Firewall

If you are not running the firewall skip this step.

You need to make it sure port 80 and 443 are open in your firewall. To open ports inside firewalld using following commands.

sudo firewall-cmd --add-service=http
sudo firewall-cmd --add-service=https
sudo firewall-cmd --runtime-to-permanent

If your system is running iptables then you can run following basic commands to enable traffic on port 80 and port 443.

sudo iptables -I INPUT -p tcp -m tcp --dport 80 -j ACCEPT
sudo iptables -I INPUT -p tcp -m tcp --dport 443 -j ACCEPT

3. Setting up Let’s Encrypt SSL on Nginx

Let’s Encrypt do a strong domain validation for ownership of the domain. After successful verification, it issues the certificate. In below command replace example with your domain name

sudo certbot --nginx -d example.com -d www.example.com

If you are the first time to install certificate then Certbot will ask you to enter Email ID and agree to terms and conditions.

After the above step, Certbot will ask you to configure HTTPS settings.

Output
Output
Please choose whether HTTPS access is required or optional.
-------------------------------------------------------------------------------
1: Easy - Allow both HTTP and HTTPS access to these sites
2: Secure - Make all requests redirect to secure HTTPS access
-------------------------------------------------------------------------------
Select the appropriate number [1-2] then [enter](press 'c' to cancel):

Select your choice and continue to next step. We recommend you to choose Secure option if you don’t want to change the configuration file manually.

NOTE: All generated files stored inside /etc/letsencrypt/live directory.

Generate Strong Diffie-Hellman Parameters

For securely exchanging cryptographic keys over an unsecured communication channel Diffie–Hellman key exchange (DH) method is used. Generate strong D-H parameters by using the following command. It will generate dhparam.pem file.

sudo openssl dhparam -out /etc/ssl/certs/dhparam.pem 2048

Now you need to edit Nginx configuration file

sudo nano /etc/nginx/nginx.conf

You should paste the following code inside the server block.

/etc/nginx/nginx.conf
ssl_dhparam /etc/ssl/certs/dhparam.pem;

Now check if the syntax is ok, to do so type:

sudo nginx -t

If there is no problem in syntax reload Nginx configuration file

sudo systemctl reload nginx

4. Autorenewal For SSL Certificates

All of these Let’s Encrypt certificates are short-lived and expires after 90 days. So you will have to update these certificates before they expire by running the following command.

sudo certbot renew

You can automate this process by adding a cronjob. Enter the following command to open crontab

sudo crontab -e

Add following lines to end of the file. It will run the command twice a day and renews if the certificate is about to expire.

0 */12 * * * /usr/bin/certbot renew >> /var/log/le-renew.log

Conclusion

You have learned how to secure Nginx with Let’s Encrypt SSL on CentOS 7 by using Certbot. If you have any queries regarding this please don’t forget to comment below.