Custom permissions in Django - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a custom permission in Django REST Framework?

A custom permission is a way to define your own rules to control who can access or modify API views beyond the built-in permissions.

beginner

Which method must be implemented when creating a custom permission class in Django REST Framework?

You must implement the has_permission(self, request, view) method to check if the request should be allowed.

beginner

How do you apply a custom permission to a Django REST Framework view?

You add the custom permission class to the view's <code>permission_classes</code> list, for example: <code>permission_classes = [MyCustomPermission]</code>.

intermediate

What is the difference between has_permission and has_object_permission in custom permissions?

has_permission checks general access before the view runs, while has_object_permission checks access for a specific object instance.

intermediate

Why use custom permissions instead of just checking user roles inside views?

Custom permissions keep access logic separate and reusable, making code cleaner and easier to maintain.

Which base class should you extend to create a custom permission in Django REST Framework?

A rest_framework.views.APIView

B django.views.View

C rest_framework.permissions.BasePermission

D django.contrib.auth.models.Permission

Custom permissions extend BasePermission to define access rules.

What does the has_permission method receive as arguments?

A request and object

B request and view

C view and object

D request only

has_permission(self, request, view) receives the request and the view being accessed.

If you want to check permissions on a specific object, which method should you override?

A has_object_permission

B has_permission

C check_permission

D get_permission

has_object_permission is used to check permissions for individual objects.

How do you apply multiple permissions to a view?

A List all permission classes in <code>permission_classes</code> list

B Use only the first permission class

C Add permissions in the URL config

D Set permissions in the model

You list all permission classes in the permission_classes attribute of the view.

What happens if a custom permission's has_permission returns False?

A The request proceeds normally

B An error is raised

C The user is redirected to login

D Access is denied and a 403 Forbidden response is returned

Returning False denies access with a 403 Forbidden response.

Explain how to create and use a custom permission in Django REST Framework.

Think about the class you extend and the methods you override.

Why is it beneficial to separate permission logic into custom permission classes instead of checking permissions inside views?

Consider how separation of concerns helps in programming.

Practice

1. What is the main purpose of creating a custom permission in Django?

easy

A. To control user access based on specific rules you define

B. To change the database schema automatically

C. To speed up the Django server response time

D. To create new database tables for users

Solution

1. Step 1: Understand what permissions do in Django

   Permissions control what users can or cannot do in the app.

2. Step 2: Identify the role of custom permissions

   Custom permissions let you define your own rules for user access beyond default ones.

3. Final Answer:

   To control user access based on specific rules you define -> Option A

4. Quick Check:

   Custom permissions = control user access [OK]

Hint: Custom permissions control access rules you create [OK]

Common Mistakes:

• Thinking permissions change database structure
• Confusing permissions with performance settings
• Believing permissions create new tables

2. Which method must you override when creating a custom permission class in Django REST Framework?

easy

A. save

B. get_queryset

C. has_permission

D. dispatch

Solution

1. Step 1: Recall the BasePermission class methods

   The main method to check access is has_permission.

2. Step 2: Confirm which method controls permission checks

   has_permission returns True or False to allow or deny access.

3. Final Answer:

   has_permission -> Option C

4. Quick Check:

   Permission check method = has_permission [OK]

Hint: Override has_permission to define access rules [OK]

Common Mistakes:

• Using get_queryset which filters data, not permissions
• Confusing save method with permission checks
• Using dispatch which is for request handling

3. Given this custom permission class, what will be the result if a user is not authenticated?

from rest_framework.permissions import BasePermission

class IsAuthenticatedCustom(BasePermission):
    def has_permission(self, request, view):
        return request.user and request.user.is_authenticated

medium

A. Code raises an error due to missing return

B. Access is denied because user is not authenticated

C. Access is granted regardless of authentication

D. Access is granted only if user is staff

Solution

1. Step 1: Analyze the has_permission method logic

   It returns True only if request.user exists and is authenticated.

2. Step 2: Consider the case when user is not authenticated

   Then request.user.is_authenticated is False, so method returns False denying access.

3. Final Answer:

   Access is denied because user is not authenticated -> Option B

4. Quick Check:

   Unauthenticated user = access denied [OK]

Hint: Check if user.is_authenticated is True to allow access [OK]

Common Mistakes:

• Assuming access is granted without authentication
• Thinking code raises error due to return statement
• Confusing staff status with authentication

4. Identify the error in this custom permission class:

from rest_framework.permissions import BasePermission

class IsOwnerPermission(BasePermission):
    def has_permission(self, request, view):
        return request.user == view.get_object().owner

medium

A. Missing import for request module

B. No return statement in has_permission

C. Incorrect comparison operator used

D. Using has_permission instead of has_object_permission for object check

Solution

1. Step 1: Understand permission methods roles

   has_permission checks general access; has_object_permission checks per object.

2. Step 2: Identify misuse of has_permission for object ownership

   Comparing user to object owner requires has_object_permission, not has_permission.

3. Final Answer:

   Using has_permission instead of has_object_permission for object check -> Option D

4. Quick Check:

   Object checks need has_object_permission [OK]

Hint: Use has_object_permission for per-object access checks [OK]

Common Mistakes:

• Confusing has_permission with has_object_permission
• Assuming import errors cause this issue
• Thinking comparison operator is wrong

5. You want to create a custom permission that allows access only if the user is authenticated and the HTTP method is safe (GET, HEAD, OPTIONS). Which is the correct implementation?

hard

A. class SafeAndAuthenticated(BasePermission):
def has_permission(self, request, view):
return request.user.is_authenticated and request.method in ['GET', 'HEAD', 'OPTIONS']

B. class SafeAndAuthenticated(BasePermission):
def has_permission(self, request, view):
return request.user.is_authenticated or request.method in ['GET', 'HEAD', 'OPTIONS']

C. class SafeAndAuthenticated(BasePermission):
def has_permission(self, request, view):
return not request.user.is_authenticated and request.method in ['GET', 'HEAD', 'OPTIONS']

D. class SafeAndAuthenticated(BasePermission):
def has_permission(self, request, view):
return request.user.is_authenticated and request.method not in ['GET', 'HEAD', 'OPTIONS']

Solution

1. Step 1: Understand the requirement

   User must be authenticated AND method must be safe (GET, HEAD, OPTIONS).

2. Step 2: Analyze each option's logic

   class SafeAndAuthenticated(BasePermission): def has_permission(self, request, view): return request.user.is_authenticated and request.method in ['GET', 'HEAD', 'OPTIONS'] uses AND with correct method list; others use OR, NOT, or wrong method checks.

3. Final Answer:

   class SafeAndAuthenticated(BasePermission): def has_permission(self, request, view): return request.user.is_authenticated and request.method in ['GET', 'HEAD', 'OPTIONS'] -> Option A

4. Quick Check:

   Use AND for combined conditions [OK]

Hint: Use AND to combine authentication and method checks [OK]

Common Mistakes:

• Using OR instead of AND allowing wrong access
• Checking for methods incorrectly with NOT
• Allowing unauthenticated users by mistake