django-security-advanced

# Django Security — Advanced

This skill extends `django-security` with file uploads, API security, headers, and deployment. Load `django-security` first.

## When to Activate

- Validating file uploads (size, extension, storage path)
- Configuring DRF rate limiting or JWT authentication
- Setting Content Security Policy headers
- Configuring secrets with django-environ
- Reviewing security logging setup before production deployment

---

## File Upload Security

### File Validation

```python
import os
from django.core.exceptions import ValidationError

def validate_file_extension(value):
    """Validate file extension."""
    ext = os.path.splitext(value.name)[1]
    valid_extensions = ['.jpg', '.jpeg', '.png', '.gif', '.pdf']
    if not ext.lower() in valid_extensions:
        raise ValidationError('Unsupported file extension.')

def validate_file_size(value):
    """Validate file size (max 5MB)."""
    filesize = value.size
    if filesize > 5 * 1024 * 1024:
        raise ValidationError('File too large. Max size is 5MB.')

# models.py
class Document(models.Model):
    file = models.FileField(
        upload_to='documents/',
        validators=[validate_file_extension, validate_file_size]
    )
```

### Secure File Storage

```python
# settings.py
MEDIA_ROOT = '/var/www/media/'
MEDIA_URL = '/media/'

# Use a separate domain for media in production
MEDIA_DOMAIN = 'https://media.example.com'

# Don't serve user uploads directly
# Use whitenoise or a CDN for static files
# Use a separate server or S3 for media files
```

---

## API Security

### Rate Limiting

```python
# settings.py
REST_FRAMEWORK = {
    'DEFAULT_THROTTLE_CLASSES': [
        'rest_framework.throttling.AnonRateThrottle',
        'rest_framework.throttling.UserRateThrottle'
    ],
    'DEFAULT_THROTTLE_RATES': {
        'anon': '100/day',
        'user': '1000/day',
        'upload': '10/hour',
    }
}

# Custom throttle
from rest_framework.throttling import UserRateThrottle

class BurstRateThrottle(UserRateThrottle):
    scope = 'burst'
    rate = '60/min'

class SustainedRateThrottle(UserRateThrottle):
    scope = 'sustained'
    rate = '1000/day'
```

### Authentication for APIs

```python
# settings.py
REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': [
        'rest_framework.authentication.TokenAuthentication',
        'rest_framework.authentication.SessionAuthentication',
        'rest_framework_simplejwt.authentication.JWTAuthentication',
    ],
    'DEFAULT_PERMISSION_CLASSES': [
        'rest_framework.permissions.IsAuthenticated',
    ],
}

# views.py
from rest_framework.decorators import api_view, permission_classes
from rest_framework.permissions import IsAuthenticated

@api_view(['GET', 'POST'])
@permission_classes([IsAuthenticated])
def protected_view(request):
    return Response({'message': 'You are authenticated'})
```

---

## Security Headers

### Content Security Policy

```python
# settings.py
CSP_DEFAULT_SRC = "'self'"
CSP_SCRIPT_SRC = "'self' https://cdn.example.com"
CSP_STYLE_SRC = "'self' 'unsafe-inline'"
CSP_IMG_SRC = "'self' data: https:"
CSP_CONNECT_SRC = "'self' https://api.example.com"

# Middleware
class CSPMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        response = self.get_response(request)
        response['Content-Security-Policy'] = (
            f"default-src {CSP_DEFAULT_SRC}; "
            f"script-src {CSP_SCRIPT_SRC}; "
            f"style-src {CSP_STYLE_SRC}; "
            f"img-src {CSP_IMG_SRC}; "
            f"connect-src {CSP_CONNECT_SRC}"
        )
        return response
```

---

## Environment Variables

### Managing Secrets

```python
# Use python-decouple or django-environ
import environ

env = environ.Env(
    # set casting, default value
    DEBUG=(bool, False)
)

# reading .env file
environ.Env.read_env()

SECRET_KEY = env('DJANGO_SECRET_KEY')
DATABASE_URL = env('DATABASE_URL')
ALLOWED_HOSTS = env.list('ALLOWED_HOSTS')

# .env file (never commit this)
# DEBUG=False
# SECRET_KEY=your-secret-key-here
# DATABASE_URL=postgresql://user:password@localhost:5432/dbname
# ALLOWED_HOSTS=example.com,www.example.com
```

---

## Logging Security Events

```python
# settings.py
LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'file': {
            'level': 'WARNING',
            'class': 'logging.FileHandler',
            'filename': '/var/log/django/security.log',
        },
        'console': {
            'level': 'INFO',
            'class': 'logging.StreamHandler',
        },
    },
    'loggers': {
        'django.security': {
            'handlers': ['file', 'console'],
            'level': 'WARNING',
            'propagate': True,
        },
        'django.request': {
            'handlers': ['file'],
            'level': 'ERROR',
            'propagate': False,
        },
    },
}
```

---

## Quick Security Checklist

| Check | Description |
|-------|-------------|
| `DEBUG = False` | Never run with DEBUG in production |
| HTTPS only | Force SSL, secure cookies |
| Strong secrets | Use environment variables for SECRET_KEY |
| Password validation | Enable all password validators |
| CSRF protection | Enabled by default, don't disable |
| XSS prevention | Django auto-escapes, don't use `\|safe` with user input |
| SQL injection | Use ORM, never concatenate strings in queries |
| File uploads | Validate file type and size |
| Rate limiting | Throttle API endpoints |
| Security headers | CSP, X-Frame-Options, HSTS |
| Logging | Log security events |
| Updates | Keep Django and dependencies updated |

Security is a process, not a product. Regularly review and update your security practices.

## Reference

- `django-security` — core settings, authentication, authorization, SQL injection, XSS, CSRF
- `security-review` — general security review checklist (OWASP Top 10)