# Security Hardening Summary

## Critical Vulnerabilities Fixed

### 1. ✅ Container Security
**Issue**: Container running as root user
**Fix**: 
- Created non-root user `appuser` in Dockerfile
- Container now runs with limited privileges
- Added `no-new-privileges:true` security option

### 2. ✅ Host Header Injection
**Issue**: Unvalidated `request.host` usage
**Fix**:
- Added whitelist of allowed hosts
- Implemented `@validate_host` decorator
- All routes now validate Host header before processing

### 3. ✅ Input Sanitization
**Issue**: Unvalidated domain input in templates
**Fix**:
- Added `sanitize_domain()` function with regex validation
- Domain length and format validation
- Prevents injection attacks via domain parameter

### 4. ✅ Network Security
**Issue**: Binding to all interfaces (0.0.0.0)
**Fix**:
- Application now binds to localhost only (127.0.0.1:8080)
- External access through Traefik reverse proxy only
- Updated all Traefik labels to use port 8080

### 5. ✅ Security Headers
**Issue**: Missing security headers
**Fix**:
- Added comprehensive security headers middleware
- X-Content-Type-Options: nosniff
- X-Frame-Options: DENY
- X-XSS-Protection: 1; mode=block
- Content-Security-Policy
- Referrer-Policy

### 6. ✅ Rate Limiting
**Issue**: No rate limiting or request validation
**Fix**:
- Implemented rate limiting per IP address
- Different limits for different endpoints:
  - Main page: 50 requests/hour
  - Health check: 10 requests/minute
  - Config endpoints: 20 requests/hour
- Request size validation (512B-2KB depending on endpoint)

### 7. ✅ Container Hardening
**Issue**: Overprivileged container
**Fix**:
- Read-only filesystem with tmpfs for /tmp
- Resource limits (256MB RAM, 0.5 CPU)
- Security options preventing privilege escalation

## Security Features Added

### Input Validation
- Host header validation against whitelist
- Domain sanitization with regex patterns
- Request size limits per endpoint
- Content-Type validation

### Rate Limiting
- Per-IP rate limiting with sliding window
- Configurable limits per endpoint type
- Automatic cleanup of old request records

### Network Security
- Localhost-only binding
- Reverse proxy required for external access
- Updated health checks for new port

### Container Security
- Non-root user execution
- Read-only filesystem
- Resource constraints
- No new privileges policy

## Deployment Notes

1. **Rebuild the Docker image** after these changes
2. **Update docker-compose.yml** with the new configuration
3. **Test all endpoints** to ensure functionality
4. **Monitor logs** for any security-related errors
5. **Consider adding Redis** for production rate limiting

## Monitoring Recommendations

- Monitor for 403 (Forbidden host) responses
- Watch for 429 (Rate limit exceeded) responses
- Log any invalid domain attempts
- Monitor resource usage within limits

## Additional Security Considerations

For production deployment, consider:
- Using Redis for distributed rate limiting
- Implementing proper logging and monitoring
- Adding WAF (Web Application Firewall) rules
- Regular security audits and dependency updates
- Implementing request signing for sensitive endpoints