SKILL.md
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
# settings/production.py
import osDEBUG = 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
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
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
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
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, PermissionRequiredMixin
from django.views.generic import UpdateView
class PostUpdateView(LoginRequiredMixin, PermissionRequiredMixin, UpdateView):
model = Post
permission_required = 'app.can_edit_others'
raise_exception = True # Return 403 instead of redirect
def get_queryset(self):
"""Only allow users to edit their own posts."""
return Post.objects.filter(author=self.request.user)
### Custom Permissions
permissions.py
from rest_framework import permissions
class IsOwnerOrReadOnly(permissions.BasePermission):
"""Allow only owners to edit objects."""
def has_object_permission(self, request, view, obj):
# Read permissions allowed for any request
if request.method in permissions.SAFE_METHODS:
return True
# Write permissions only for owner
return obj.author == request.user
class IsAdminOrReadOnly(permissions.BasePermission):
"""Allow admins to do anything, others read-only."""
def has_permission(self, request, view):
if request.method in permissions.SAFE_METHODS:
return True
return request.user and request.user.is_staff
class IsVerifiedUser(permissions.BasePermission):
"""Allow only verified users."""
def has_permission(self, request, view):
return request.user and request.user.is_authenticated and request.user.is_verified
### Role-Based Access Control (RBAC)
models.py
from django.contrib.auth.models import AbstractUser, Group
class User(AbstractUser):
ROLE_CHOICES = [
('admin', 'Administrator'),
('moderator', 'Moderator'),
('user', 'Regular User'),
]
role = models.CharField(max_length=20, choices=ROLE_CHOICES, default='user')
def is_admin(self):
return self.role == 'admin' or self.is_superuser
def is_moderator(self):
return self.role in ['admin', 'moderator']
Mixins
class AdminRequiredMixin:
"""Mixin to require admin role."""
def dispatch(self, request, args, *kwargs):
if not request.user.is_authenticated or not request.user.is_admin():
from django.core.exceptions import PermissionDenied
raise PermissionDenied
return super().dispatch(request, args, *kwargs)
## SQL Injection Prevention
### Django ORM Protection
GOOD: Django ORM automatically escapes parameters
def get_user(username):
return User.objects.get(username=username) # Safe
GOOD: Using parameters with raw()
def search_users(query):
return User.objects.raw('SELECT * FROM users WHERE username = %s', [query])
BAD: Never directly interpolate user input
def get_user_bad(username):
return User.objects.raw(f'SELECT * FROM users WHERE username = {username}') # VULNERABLE!
GOOD: Using filter with proper escaping
def get_users_by_email(email):
return User.objects.filter(email__iexact=email) # Safe
GOOD: Using Q objects for complex queries
from django.db.models import Q
def search_users_complex(query):
return User.objects.filter(
Q(username__icontains=query) |
Q(email__icontains=query)
) # Safe
### Extra Security with raw()
If you must use raw SQL, always use parameters
User.objects.raw(
'SELECT * FROM users WHERE email = %s AND status = %s',
[user_input_email, status]
)
## XSS Prevention
### Template Escaping
{# Django auto-escapes variables by default - SAFE #}
{{ user_input }} {# Escaped HTML #}
{# Explicitly mark safe only for trusted content #}
{{ trusted_html|safe }} {# Not escaped #}
{# Use template filters for safe HTML #}
{{ user_input|escape }} {# Same as default #}
{{ user_input|striptags }} {# Remove all HTML tags #}
{# JavaScript escaping #}
<script>
var username = {{ username|escapejs }};
</script>
### Safe String Handling
from django.utils.safestring import mark_safe
from django.utils.html import escape
BAD: Never mark user input as safe without escaping
def render_bad(user_input):
return mark_safe(user_input) # VULNERABLE!
GOOD: Escape first, then mark safe
def render_good(user_input):
return mark_safe(escape(user_input))
GOOD: Use format_html for HTML with variables
from django.utils.html import format_html
def greet_user(username):
return format_html('<span class="user">{}</span>', escape(username))
### HTTP Headers
settings.py
SECURE_CONTENT_TYPE_NOSNIFF = True # Prevent MIME sniffing
SECURE_BROWSER_XSS_FILTER = True # Enable XSS filter
X_FRAME_OPTIONS = 'DENY' # Prevent clickjacking
Custom middleware
from django.conf import settings
class SecurityHeaderMiddleware:
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
response = self.get_response(request)
response['X-Content-Type-Options'] = 'nosniff'
response['X-Frame-Options'] = 'DENY'
response['X-XSS-Protection'] = '1; mode=block'
response['Content-Security-Policy'] = "default-src 'self'"
return response
## CSRF Protection
### Default CSRF Protection
settings.py - CSRF is enabled by default
CSRF_COOKIE_SECURE = True # Only send over HTTPS
CSRF_COOKIE_HTTPONLY = True # Prevent JavaScript access
CSRF_COOKIE_SAMESITE = 'Lax' # Prevent CSRF in some cases
CSRF_TRUSTED_ORIGINS = ['https://example.com'] # Trusted domains
Template usage
<form method="post">
{% csrf_token %}
{{ form.as_p }}
<button type="submit">Submit</button>
</form>
AJAX requests
function getCookie(name) {
let cookieValue = null;
if (document.cookie && document.cookie !== '') {
const cookies = document.cookie.split(';');
for (let i = 0; i < cookies.length; i++) {
const cookie = cookies[i].trim();
if (cookie.substring(0, name.length + 1) === (name + '=')) {
cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
break;
}
}
}
return cookieValue;
}
fetch('/api/endpoint/', {
method: 'POST',
headers: {
'X-CSRFToken': getCookie('csrftoken'),
'Content-Type': 'application/json',
},
body: JSON.stringify(data)
});
### Exempting Views (Use Carefully)
from django.views.decorators.csrf import csrf_exempt
@csrf_exempt # Only use when absolutely necessary!
def webhook_view(request):
# Webhook from external service
pass
## File Upload Security
### File Validation
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
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
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
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
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
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
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,
},
},
}