Security Headers Configuration Skill

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

Agent Skills: Security Headers Configuration

Install this agent skill to your local

Skill Files