Django Security

# Django Security Best Practices

Comprehensive security guidelines for Django applications to protect against common vulnerabilities.

## When to Activate

- Setting up Django authentication and authorization
- Implementing user permissions and roles
- Configuring production security settings
- Reviewing Django application for security issues
- Deploying Django applications to production

## Core Security Settings

### Production Settings Configuration

```python
# settings/production.py
import os

DEBUG = False  # CRITICAL: Never use True in production

ALLOWED_HOSTS = os.environ.get('ALLOWED_HOSTS', '').split(',')

# Security headers
SECURE_SSL_REDIRECT = True
SESSION_COOKIE_SECURE = True
CSRF_COOKIE_SECURE = True
SECURE_HSTS_SECONDS = 31536000  # 1 year
SECURE_HSTS_INCLUDE_SUBDOMAINS = True
SECURE_HSTS_PRELOAD = True
SECURE_CONTENT_TYPE_NOSNIFF = True
SECURE_BROWSER_XSS_FILTER = True
X_FRAME_OPTIONS = 'DENY'

# HTTPS and Cookies
SESSION_COOKIE_HTTPONLY = True
CSRF_COOKIE_HTTPONLY = True
SESSION_COOKIE_SAMESITE = 'Lax'
CSRF_COOKIE_SAMESITE = 'Lax'

# Secret key (must be set via environment variable)
SECRET_KEY = os.environ.get('DJANGO_SECRET_KEY')
if not SECRET_KEY:
    raise ImproperlyConfigured('DJANGO_SECRET_KEY environment variable is required')

# Password validation
AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
        'OPTIONS': {
            'min_length': 12,
        }
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]
```

## Authentication

### Custom User Model

```python
# apps/users/models.py
from django.contrib.auth.models import AbstractUser
from django.db import models

class User(AbstractUser):
    """Custom user model for better security."""

    email = models.EmailField(unique=True)
    phone = models.CharField(max_length=20, blank=True)

    USERNAME_FIELD = 'email'  # Use email as username
    REQUIRED_FIELDS = ['username']

    class Meta:
        db_table = 'users'
        verbose_name = 'User'
        verbose_name_plural = 'Users'

    def __str__(self):
        return self.email

# settings/base.py
AUTH_USER_MODEL = 'users.User'
```

### Password Hashing

```python
# Django uses PBKDF2 by default. For stronger security:
PASSWORD_HASHERS = [
    'django.contrib.auth.hashers.Argon2PasswordHasher',
    'django.contrib.auth.hashers.PBKDF2PasswordHasher',
    'django.contrib.auth.hashers.PBKDF2SHA1PasswordHasher',
    'django.contrib.auth.hashers.BCryptSHA256PasswordHasher',
]
```

### Session Management

```python
# Session configuration
SESSION_ENGINE = 'django.contrib.sessions.backends.cache'  # Or 'db'
SESSION_CACHE_ALIAS = 'default'
SESSION_COOKIE_AGE = 3600 * 24 * 7  # 1 week
SESSION_SAVE_EVERY_REQUEST = False
SESSION_EXPIRE_AT_BROWSER_CLOSE = False  # Better UX, but less secure
```

## Authorization

### Permissions

```python
# models.py
from django.db import models
from django.contrib.auth.models import Permission

class Post(models.Model):
    title = models.CharField(max_length=200)
    content = models.TextField()
    author = models.ForeignKey(User, on_delete=models.CASCADE)

    class Meta:
        permissions = [
            ('can_publish', 'Can publish posts'),
            ('can_edit_others', 'Can edit posts of others'),
        ]

    def user_can_edit(self, user):
        """Check if user can edit this post."""
        return self.author == user or user.has_perm('app.can_edit_others')

# views.py
from django.contrib.auth.mixins import LoginRequiredMixin