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

ByAkensai

Learning how to secure Nginx with Let’s Encrypt SSL/TLS and harden your HTTPS configuration on Ubuntu is one of the most important steps you can take as a server administrator. Without SSL/TLS, all data between your server and visitors travels in plain text. That means passwords, form data, and sensitive information are exposed. Let’s Encrypt gives you free, trusted SSL certificates. Combined with a hardened HTTPS configuration, your server becomes significantly more resistant to attacks. In this tutorial, you’ll install Certbot, obtain a certificate, configure Nginx to use it, and then tighten your SSL settings to get an A+ rating on SSL Labs. By the end, your site will be encrypted, fast, and properly secured.

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

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

– A server running Ubuntu 20.04 or 22.04
– Nginx installed and running
– A registered domain name pointed to your server’s IP address
– Root or sudo access to the server
– Basic comfort with the Linux command line

Your domain’s DNS A record must be resolving to your server before Let’s Encrypt can issue a certificate. You can verify this with dig yourdomain.com or a free DNS lookup tool.

Estimated time to complete: 20–30 minutes

Make sure Nginx is active before proceeding:

sudo systemctl status nginx

If it’s not running, start it with sudo systemctl start nginx.

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

Related article: How to Configure Redis Object Caching for Wordpress Performance Optimization

Follow these steps carefully. Each one builds on the last.

Step 1: Update your system packages

Always start with a fresh package index. This prevents version conflicts.

sudo apt update && sudo apt upgrade -y

Step 2: Install Certbot and the Nginx plugin

Certbot automates certificate issuance and renewal. The Nginx plugin handles configuration changes automatically.

sudo apt install certbot python3-certbot-nginx -y

Step 3: Allow HTTPS traffic through the firewall

If you’re using UFW, open ports 80 and 443:

sudo ufw allow 'Nginx Full'
sudo ufw reload

Port 80 is needed for the Let’s Encrypt HTTP challenge. Port 443 serves your HTTPS traffic.

Step 4: Obtain your SSL certificate

Run Certbot with the Nginx plugin. Replace yourdomain.com with your actual domain:

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

Certbot will ask for your email address and prompt you to agree to the terms. It then contacts Let’s Encrypt, verifies domain ownership, and installs the certificate. When asked about redirecting HTTP to HTTPS, choose option 2 to redirect all traffic automatically.

Step 5: Verify the certificate was installed

Check that Certbot modified your Nginx config correctly:

sudo nginx -t

You should see syntax is ok and test is successful. Reload Nginx to apply changes:

sudo systemctl reload nginx

Step 6: Harden your SSL/TLS configuration

The default Certbot settings are good but not optimal. Open your Nginx server block file. It’s usually located at /etc/nginx/sites-available/yourdomain.com. Find the SSL section and update it with stronger settings:

ssl_protocols TLSv1.2 TLSv1.3;
ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256;
ssl_prefer_server_ciphers off;
ssl_session_timeout 1d;
ssl_session_cache shared:MozSSL:10m;
ssl_session_tickets off;
ssl_stapling on;
ssl_stapling_verify on;
resolver 8.8.8.8 8.8.4.4 valid=300s;
resolver_timeout 5s;

These settings disable outdated TLS 1.0 and 1.1. They also enable OCSP stapling, which speeds up the SSL handshake for visitors. You can learn more about recommended cipher suites at the Mozilla SSL Configuration Generator.

Step 7: Add HTTP security headers

Inside your server block, add these headers to protect against common web attacks:

add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;
add_header X-Frame-Options DENY;
add_header X-Content-Type-Options nosniff;
add_header Referrer-Policy "no-referrer-when-downgrade";
add_header X-XSS-Protection "1; mode=block";

The Strict-Transport-Security header tells browsers to always use HTTPS for your domain. The max-age value is set to two years. This is the recommended value for HSTS preloading.

Step 8: Test and reload Nginx

Always test your configuration before reloading:

sudo nginx -t && sudo systemctl reload nginx

Step 9: Verify automatic renewal

Let’s Encrypt certificates expire after 90 days. Certbot installs a systemd timer to renew them automatically. Check it with:

sudo systemctl status certbot.timer

You can also do a dry run to confirm renewal works:

sudo certbot renew --dry-run

If the dry run completes without errors, automatic renewal is working correctly. For more details on certificate management, visit the official Certbot documentation.

Troubleshooting Common Issues When You Secure Nginx with Let’s Encrypt SSL/TLS on Ubuntu

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

This usually means port 80 is blocked. Check your firewall rules and confirm your DNS is pointing to the right server IP.

Error: “nginx: [emerg] unknown directive”

You likely have a typo in your config file. Run sudo nginx -t to see the exact line causing the problem.

Certificate not renewing automatically

Check if the Certbot timer is active: sudo systemctl list-timers | grep certbot. If it’s missing, re-enable it with sudo systemctl enable certbot.timer.

SSL Labs score lower than expected

Run your domain through SSL Labs Server Test to see exactly what’s holding your score back. Common issues include weak cipher suites or missing HSTS headers.

Mixed content warnings in browser

This happens when your page loads HTTP resources alongside HTTPS. Update all internal links, images, and scripts to use HTTPS URLs.

Conclusion

You’ve now completed the full process of how to secure Nginx with Let’s Encrypt SSL/TLS and harden your HTTPS configuration on Ubuntu. Your server now has a valid, trusted certificate. It also uses modern TLS protocols and strong security headers. Certbot will handle renewals automatically, so you don’t need to worry about expired certificates.

From here, you might want to explore setting up a Web Application Firewall, configuring Nginx rate limiting, or optimizing your server for WordPress performance. Each of these steps builds on the secure foundation you’ve just created. A properly secured server protects your users and builds trust in your site.

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