Security Headers

Essential Security Headers

# /etc/nginx/snippets/security-headers.conf

# Prevent clickjacking
add_header X-Frame-Options "SAMEORIGIN" always;

# Prevent MIME type sniffing
add_header X-Content-Type-Options "nosniff" always;

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

# Referrer policy
add_header Referrer-Policy "strict-origin-when-cross-origin" always;

# HSTS (HTTPS only - be careful with this)
add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;

# Permissions policy (formerly Feature-Policy)
add_header Permissions-Policy "geolocation=(), microphone=(), camera=()" always;

Content Security Policy

# Basic CSP
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self';" always;

# CSP with external resources
add_header Content-Security-Policy "default-src 'self'; script-src 'self' https://cdn.example.com; style-src 'self' https://fonts.googleapis.com; img-src 'self' https: data:; font-src 'self' https://fonts.gstatic.com;" always;

# Report-only mode (for testing)
add_header Content-Security-Policy-Report-Only "default-src 'self'; report-uri /csp-report" always;

Complete Security Configuration

server {
    listen 443 ssl http2;
    server_name example.com;

    # SSL configuration
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

    # Security headers
    include snippets/security-headers.conf;

    # Hide nginx version
    server_tokens off;

    # Limit request body size
    client_max_body_size 10M;

    # Prevent access to hidden files
    location ~ /\. {
        deny all;
    }

    # Prevent access to sensitive files
    location ~* \.(env|log|htaccess|htpasswd|ini|conf)$ {
        deny all;
    }

    root /var/www/example.com;
    index index.html;

    location / {
        try_files $uri $uri/ =404;
    }
}

Testing Security Headers

# Check headers
curl -I https://example.com

# Online tools:
# - https://securityheaders.com
# - https://observatory.mozilla.org

Header Notes