Security Headers Configuration
Implement HTTP security headers to defend against common browser-based attacks.
Essential Headers
| Header | Purpose | Value |
|---|---|---|
| HSTS | Force HTTPS | max-age=31536000; includeSubDomains |
| CSP | Restrict resources | default-src 'self' |
| X-Frame-Options | Prevent clickjacking | DENY |
| X-Content-Type-Options | Prevent MIME sniffing | nosniff |
Express Implementation
const helmet = require('helmet');
app.use(helmet());
// Custom CSP
app.use(helmet.contentSecurityPolicy({
directives: {
defaultSrc: ["'self'"],
scriptSrc: ["'self'", "'unsafe-inline'"],
styleSrc: ["'self'", "'unsafe-inline'"],
imgSrc: ["'self'", "data:", "https:"],
connectSrc: ["'self'", "https://api.example.com"],
fontSrc: ["'self'", "https://fonts.gstatic.com"],
frameAncestors: ["'none'"]
}
}));Nginx Configuration
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;
add_header Permissions-Policy "geolocation=(), microphone=(), camera=()" always;
add_header Content-Security-Policy "default-src 'self'; script-src 'self'" always;Verification Tools
Security Headers Checklist
- HSTS enabled with long max-age
- CSP configured and tested
- X-Frame-Options set to DENY
- X-Content-Type-Options set to nosniff
- Referrer-Policy configured
- Permissions-Policy disables unused features
Additional Implementations
See references/python-apache.md for:
- Python Flask security headers middleware
- Flask-Talisman library configuration
- Apache.htaccess configuration
- Header testing script
Common Mistakes
- Setting CSP to report-only permanently
- Using overly permissive policies
- Forgetting to test after changes
- Not including all subdomains in HSTS