The Complete Guide to Securing Nginx Web Servers

Hey friend! Nginx has become one of the most widely used web servers on the Internet. In fact, it now runs over 30% of the world’s busiest websites!

However, with great power comes great responsibility. Securing Nginx properly is absolutely critical given how many high-profile sites rely on it.

In this comprehensive guide, I’ll walk you through all the key steps and best practices for hardening your Nginx servers against attack. I’ll share my insights as a technology expert on how to balance performance and security when making configuration decisions.

By the end, you’ll have a solid roadmap for implementing robust security across these critical areas:

• SSL/TLS encryption
• System hardening
• Application security
• Logging and monitoring

Let’s get started!

Why Securing Nginx Matters

Before we dig into the how, let me quickly explain why going through the effort of hardening Nginx is so important.

As a high-performance web server, Nginx has some key advantages that contribute to its widespread popularity:

• Speed – Nginx uses an asynchronous event-driven approach that provides much higher concurrency and throughput compared to traditional servers like Apache. It‘s incredibly fast at serving content.

• Efficiency – Nginx has a much smaller memory and CPU footprint compared to other web servers. This makes it ideal for high-traffic sites.

• Scalability – Nginx scales amazingly well, capable of handling many thousands of concurrent connections with minimal overhead.

• Flexibility – Nginx provides load balancing, media streaming, caching, and other features via its flexible module architecture.

However, these same strengths also make Nginx an attractive target for attackers:

• 30% market share – Given how widely used Nginx is, vulnerabilities can impact a huge number of high-traffic websites.

• Business-critical usage – Many organizations rely on Nginx to serve critical content, apps, and APIs to their business. Downtime is unacceptable.

• Valuable data – Nginx often fronts sensitive databases and storage systems containing valuable customer data.

Some real-world examples of Nginx security incidents include:

• The 2017 ransomware attack that hijacked 150,000 Nginx servers to mine cryptocurrency.

• The 2018 Git vulnerability that allowed remote code execution on Nginx servers.

• The 2020 misconfiguration exposing the Parler website and millions of private messages.

Based on Netcraft data, over 180 million websites run on Nginx. A vulnerability in a widely used version could impact tens of millions of sites simultaneously!

Clearly, hardening and securing your Nginx servers should be a top priority to avoid becoming a statistic. Now let‘s look at how to do that properly across several key areas.

Step 1 – SSL/TLS Encryption

The first step in securing connections to your Nginx server is implementing SSL/TLS encryption. This prevents sensitive information sent over HTTP from being exposed.

Obtain and Install a Valid SSL Certificate

All connections to your Nginx server should use HTTPS, which relies on an SSL certificate to encrypt traffic. When setting this up:

• Purchase certificate – Obtain a certificate from a trusted commercial CA like Let‘s Encrypt or DigiCert. Avoid self-signed certificates.

• 2048-bit key minimum – Use a 2048-bit private key at minimum when generating your CSR and certificate. 1024-bit keys are insecure.

• SHA-256 algorithm – Go with a SHA-256 signature hash or higher for optimal security when creating your private key and CSR.

• Configure Nginx – Install the certificate files and configure Nginx to use them:

server {

  listen 443 ssl;

  ssl_certificate /path/to/fullchain.pem;
  ssl_certificate_key /path/to/privkey.pem;

}

This will enable Nginx to handle encrypted HTTPS connections using your certificate.

Optimize TLS Settings

Simply enabling SSL is not enough – you also need to optimize TLS settings for best security:

• TLS 1.2 only – Disable old versions and exclusively allow more secure TLS 1.2:

ssl_protocols TLSv1.2; 

• Strong ciphers only – Only use strong ciphers offering Perfect Forward Secrecy. Drop insecure ciphers like DES, RC4, MD5:

ssl_ciphers HIGH:!aNULL:!MD5;

• Diffie-Hellman groups – Use unique DH groups per server for Perfect Forward Secrecy:

ssl_dhparam /path/to/dhparam.pem;

• OCSP stapling – Enable OCSP stapling for faster certificate revocation checking.

• Chain certificate – Add intermediate chain certs to avoid trust warnings.

Check your SSL Labs rating and remediate any issues to get an A+ on all criteria.

Step 2 – Operating System Hardening

Besides just encrypting connections, you also need to harden the underlying operating system and close vulnerabilities.

Keep Nginx Updated

It‘s vital to keep your Nginx version updated and apply security patches:

• Review changelogs on each release for security and bug fix details.

• Follow recommended procedures for upgrading major versions like 1.14 to 1.16.

• Use a repository like Nginx Repo for RHEL/CentOS to more easily keep Nginx updated.

Neglecting updates is dangerous – for example, the 2017 ransomware attack exploited a 4-year-old Nginx vulnerability that had been patched!

Operating System Hardening

Harden the OS platform running Nginx by following security best practices:

• Disable unused services – Disable any unnecessary services to reduce your attack surface.

• Firewall rules – Restrict network access to only allow required ports like 80, 443, and block everything else.

• User access controls – Remove shell access for the nginx user and limit permissions using SELinux or AppArmor.

• Filesystem permissions – Tightly restrict filesystem permissions for Nginx folders like /etc/nginx.

• Patch regularly – Keep the OS and other software updated constantly to latest versions.

Remove Version Leakage

Disable any Nginx modules that reveal sensitive version info:

server_tokens off;

Hackers can exploit known vulnerabilities in specific versions. Don‘t give them intel!

Step 3 – Application Security Best Practices

Along with system hardening, Nginx configuration also needs proper application security:

Disable Unneeded HTTP Methods

Disallow unused HTTP methods like TRACE and TRACK which could potentially be abused:

if ($request_method !~* ^(GET|HEAD|POST)$ ){
  return 403;
} 

Prevent Clickjacking Attacks

Clickjacking tricks users into clicking hidden elements. Set the X-Frame-Options header to prevent other sites framing your content:

add_header X-Frame-Options "SAMEORIGIN";

Mitigate Cross-Site Scripting (XSS)

Enable Nginx‘s built-in X-XSS-Protection header to help mitigate XSS attacks:

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

This will block pages if a cross-site script is detected.

Implement a Web Application Firewall

For deep application security against OWASP Top 10 threats, deploy a WAF like ModSecurity along with the OWASP Core Rule Set.

Limit Direct File Access

Block users from directly accessing potentially sensitive application code:

location ~ \.php$ {
  deny all;
}

Users should only access rendered content through Nginx.

Step 4 – Logging and Monitoring

Logging and monitoring are crucial to detecting and responding quickly to attacks.

Extensive HTTP Logging

Capture detailed HTTP access logs including:

• URLS accessed
• HTTP methods
• Status codes
• User agents
• Timestamps
• IP addresses

log_format main 
  ‘$remote_addr - $remote_user [$time_local] "$request" ‘
  ‘$status $body_bytes_sent "$http_referer" ‘
  ‘"$http_user_agent" "$http_x_forwarded_for"‘;

access_log /var/log/nginx/access.log main;

Detailed logging provides vital forensic evidence if your site is compromised.

Implement Intrusion Detection

Analyze Nginx logs to detect attack patterns and compromised resources using tools like ossec and elastiflow.

Monitor Key Metrics

Actively monitor performance metrics like HTTP error rates, traffic spikes, and response times for anomalies indicating attacks.

Review Config Changes

Use version control for Nginx configs and review all changes to identify suspicious or unauthorized modifications.

Conclusion

That wraps up this comprehensive guide on hardening Nginx for security!

Here are some key takeaways:

• Implement SSL using strong certificates and optimized TLS settings.
• Harden the operating system and keep Nginx updated with the latest security patches.
• Disable unused functionality and deploy application security measures like a WAF.
• Extensively log traffic and actively monitor for attacks.

No single technique can make your Nginx servers 100% secure. However, following these industry best practices will significantly improve your security posture against the myriad of threats on the Internet.

With hackers constantly evolving their tactics, properly securing your servers is a constant process that requires diligence. But I hope these tips provide a solid roadmap as you lock down your Nginx environments.

Now go forth and deploy robust security so you can keep serving your sites at Nginx‘s blazing fast speed!