How to Secure Nginx with Let’s Encrypt SSL/TLS and Harden Your Configuration on Ubuntu 24.04

ByAkensai

Learning how to secure Nginx with Let’s Encrypt SSL/TLS and harden your configuration on Ubuntu 24.04 is one of the most important steps you can take for any production server. Without HTTPS, your visitors’ data travels in plain text. Search engines also penalize unencrypted sites. This tutorial walks you through installing Certbot, obtaining a free SSL certificate, and applying security hardening settings that protect your server from common attacks. By the end, your Nginx server will serve content over HTTPS with modern TLS settings, strong cipher suites, and important security headers in place. Whether you’re running a WordPress site, a web application, or a simple landing page, these steps apply to any Nginx setup on Ubuntu 24.04.

Prerequisites to How to Secure Nginx with Let’s Encrypt SSL/TLS and Harden Your Configuration on Ubuntu 24.04

Before you start, make sure you have the following in place:

– Ubuntu 24.04 server with a non-root sudo user
– Nginx already installed and running
– A registered domain name pointed to your server’s public IP address via DNS A record
– Root or sudo access to the server
– Basic familiarity with the Linux command line

Your domain’s DNS must fully propagate before Let’s Encrypt can verify ownership. Use a tool like DNS Checker to confirm your A record is live. Estimated time to complete this tutorial is 20–30 minutes. You don’t need prior SSL experience. Every command is explained clearly.

How to Secure Nginx with Let’s Encrypt SSL/TLS and Harden Your Configuration on Ubuntu 24.04: Step-by-Step

Related article: How to Create and Register Custom Post Types in WordPress with the Register_post_type() Function

Step 1: Update Your System

Always start with a fresh package index. This ensures you install the latest versions of all tools.

sudo apt update && sudo apt upgrade -y

Step 2: Install Certbot and the Nginx Plugin

Certbot is the official Let’s Encrypt client. The Nginx plugin handles certificate installation and server block updates automatically.

sudo apt install certbot python3-certbot-nginx -y

Step 3: Obtain Your SSL Certificate

Replace yourdomain.com with your actual domain. Certbot will verify domain ownership and fetch the certificate.

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

Follow the prompts. Enter your email address when asked. Agree to the terms of service. Certbot will automatically update your Nginx config to redirect HTTP to HTTPS.

Step 4: Verify Automatic Certificate Renewal

Let’s Encrypt certificates expire every 90 days. Certbot installs a systemd timer that renews them automatically. Test it with a dry run.

sudo certbot renew --dry-run

You should see a success message. If you don’t, check your firewall rules and DNS settings.

Step 5: Create a Strong Diffie-Hellman Parameter File

This file strengthens the key exchange process during TLS handshakes. It takes a few minutes to generate.

sudo openssl dhparam -out /etc/nginx/dhparam.pem 2048

Step 6: Harden Your Nginx SSL Configuration

Open your domain’s Nginx server block. It’s usually located at /etc/nginx/sites-available/yourdomain.com.

sudo nano /etc/nginx/sites-available/yourdomain.com

Inside the server block that listens on port 443, add or update these SSL settings:

ssl_protocols TLSv1.2 TLSv1.3;
ssl_prefer_server_ciphers on;
ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305';
ssl_dhparam /etc/nginx/dhparam.pem;
ssl_session_cache shared:SSL:10m;
ssl_session_timeout 1d;
ssl_session_tickets off;

These settings disable outdated TLS 1.0 and 1.1. They enforce strong cipher suites only.

Step 7: Add HTTP Security Headers

Security headers protect against clickjacking, XSS attacks, and content sniffing. Add these lines inside the same server block.

add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
add_header X-Frame-Options DENY always;
add_header X-Content-Type-Options nosniff always;
add_header X-XSS-Protection "1; mode=block" always;
add_header Referrer-Policy "strict-origin-when-cross-origin" always;

The Strict-Transport-Security header tells browsers to always use HTTPS. It’s one of the most important headers you can set.

Step 8: Test and Reload Nginx

Always test your configuration before reloading. A syntax error will take down your site.

sudo nginx -t

If the output says syntax is ok and test is successful, reload Nginx.

sudo systemctl reload nginx

Step 9: Verify Your SSL Rating

Visit SSL Labs Server Test and enter your domain. A properly hardened server should score an A or A+. Review any warnings and fix them as needed.

Troubleshooting Common Issues When Securing Nginx with SSL/TLS on Ubuntu 24.04

Error: “Failed to connect to host for DVSNI challenge”

This means Let’s Encrypt can’t reach your server on port 80. Check your firewall with sudo ufw status. Make sure port 80 is open.

sudo ufw allow 80
sudo ufw allow 443

Error: “nginx: configuration file test failed”

You have a syntax error in your config. Run sudo nginx -t to see the exact line. Common mistakes include missing semicolons or mismatched braces.

Certificate Not Renewing Automatically

Check the Certbot timer status:

sudo systemctl status certbot.timer

If it’s inactive, enable it:

sudo systemctl enable certbot.timer
sudo systemctl start certbot.timer

Mixed Content Warnings in Browser

Your site loads over HTTPS but some resources still use HTTP. Update all internal links and asset URLs to use HTTPS. If you’re running WordPress, the Really Simple SSL plugin can fix this automatically.

SSL Labs Score Lower Than Expected

If you score a B, you may still have TLS 1.0 or 1.1 enabled. Double-check your ssl_protocols line. Make sure it only includes TLSv1.2 TLSv1.3.

Conclusion

You’ve now completed the process to secure Nginx with Let’s Encrypt SSL/TLS and harden your configuration on Ubuntu 24.04. Your server encrypts traffic with modern TLS protocols, uses strong cipher suites, and sends important security headers with every response. These changes protect your visitors and improve your site’s trustworthiness. Certbot handles certificate renewals automatically, so you don’t have to worry about expiration. From here, you can explore additional hardening steps like setting up a Web Application Firewall, configuring rate limiting in Nginx, or enabling OCSP stapling for faster TLS handshakes. Keeping your server configuration up to date is an ongoing process. Revisit your SSL Labs score periodically to catch any new vulnerabilities.

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