How to Secure Nginx with Let’s Encrypt SSL/TLS and Harden Your Configuration for an A+ Rating

ByAkensai

Learning how to secure Nginx with Let’s Encrypt SSL/TLS and harden your configuration for an A+ rating is one of the most valuable skills a server administrator can have. An unsecured web server exposes your users to data interception, man-in-the-middle attacks, and browser warnings that destroy trust instantly. Let’s Encrypt provides free, automated SSL certificates trusted by all major browsers. Combined with a hardened Nginx configuration, you can achieve a perfect A+ score on SSL Labs’ Server Test. This tutorial walks you through every step , from installing Certbot to tuning your TLS settings, enabling HSTS, and disabling weak ciphers. By the end, your server will be encrypted, hardened, and ready for production traffic.

Prerequisites to Secure Nginx with Let’s Encrypt SSL/TLS for an A+ Rating

Before you begin, make sure you have the following in place.

Required access and software:
– A server running Ubuntu 20.04 or 22.04 (this guide uses Ubuntu)
– Nginx installed and running
– A registered domain name pointing to your server’s IP address
– Root or sudo access to the server
– Port 80 and 443 open in your firewall

Assumed knowledge level:
You should be comfortable using the Linux command line. You don’t need to be an expert, but you should know how to SSH into a server and edit files with a text editor like nano.

Estimated time to complete: 20–30 minutes

If Nginx isn’t installed yet, run:

sudo apt update
sudo apt install nginx -y
sudo systemctl enable nginx
sudo systemctl start nginx

Confirm your domain resolves correctly before continuing. Certbot will fail if DNS isn’t pointing to your server.

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

For more strange history, see: How to Set Up and Configure Pfsense Firewall From Scratch

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

Step 1: Install Certbot and the Nginx Plugin

Certbot automates the certificate issuance and renewal process. Install it using Snap for the latest version:

sudo apt install snapd -y
sudo snap install --classic certbot
sudo ln -s /snap/bin/certbot /usr/bin/certbot

Step 2: 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 verify domain ownership, issue the certificate, and automatically update your Nginx config. Follow the on-screen prompts and choose to redirect HTTP to HTTPS when asked.

Step 3: Verify Auto-Renewal

Let’s Encrypt certificates expire every 90 days. Certbot sets up a renewal timer automatically. Test it with:

sudo certbot renew --dry-run

If you see “Congratulations, all simulated renewals succeeded,” you’re good to go.

Step 4: Generate a Strong Diffie-Hellman Group

A custom DH group prevents certain cryptographic attacks. This command takes a few minutes:

sudo openssl dhparam -out /etc/nginx/dhparam.pem 4096

Step 5: Harden Your Nginx SSL Configuration

This is the most important step for achieving an A+ rating. Open your site’s Nginx config:

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

Update the server block for port 443 with the following settings:

server {
    listen 443 ssl http2;
    server_name yourdomain.com www.yourdomain.com;

    ssl_certificate /etc/letsencrypt/live/yourdomain.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/yourdomain.com/privkey.pem;
    ssl_trusted_certificate /etc/letsencrypt/live/yourdomain.com/chain.pem;

    ssl_dhparam /etc/nginx/dhparam.pem;

    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_prefer_server_ciphers on;
    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_session_cache shared:SSL:10m;
    ssl_session_timeout 1d;
    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;

    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 X-XSS-Protection "1; mode=block";

    root /var/www/yourdomain.com/html;
    index index.html index.php;
}

Save and close the file.

Step 6: Test and Reload Nginx

Always test your config before reloading. A syntax error can take your site offline:

sudo nginx -t
sudo systemctl reload nginx

You should see syntax is ok and test is successful.

Step 7: Run the SSL Labs Test

Visit the SSL Labs Server Test and enter your domain. With this configuration, you should receive an A+ rating. The test checks your cipher strength, protocol support, HSTS headers, and OCSP stapling.

Troubleshooting Common Issues When Hardening Nginx SSL/TLS

Even with careful steps, things can go wrong. Here are the most common problems and how to fix them.

Certbot fails with “Could not bind to IPv4 or IPv6”

This means port 80 is already in use. Stop the process using it:

sudo systemctl stop nginx
sudo certbot certonly --standalone -d yourdomain.com
sudo systemctl start nginx

Nginx fails the config test after editing

Check your syntax carefully. Missing semicolons and mismatched brackets are common culprits. Run sudo nginx -t and read the error line number.

HSTS causes browser errors after reverting to HTTP

HSTS tells browsers to always use HTTPS. If you remove SSL later, users will see errors for up to two years. Don’t add the preload directive unless you’re fully committed to HTTPS.

OCSP stapling shows “ssl_stapling” ignored

This happens when the trusted certificate chain is missing. Make sure your ssl_trusted_certificate directive points to the chain.pem file, not fullchain.pem.

SSL Labs scores you below A+

Check the “Protocol Details” section in the SSL Labs report. Common causes include:
– TLS 1.0 or 1.1 still enabled , remove them from ssl_protocols
– Session tickets enabled , make sure ssl_session_tickets off; is present
– Missing HSTS header , double-check your add_header directive

You can also reference the official Nginx SSL module documentation for detailed parameter explanations.

Conclusion

You now know how to secure Nginx with Let’s Encrypt SSL/TLS and harden your configuration for an A+ rating. You’ve installed a free, trusted certificate, disabled weak protocols and ciphers, enabled OCSP stapling, added HSTS headers, and verified everything with SSL Labs. This setup protects your users and builds trust with search engines and browsers alike. Keep your certificates renewing automatically and revisit your cipher list every six to twelve months as cryptographic best practices evolve. From here, you might want to explore setting up a Web Application Firewall, configuring rate limiting in Nginx, or locking down your WordPress installation further. A secure server is never a one-time task , it’s an ongoing practice.

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