Role-based access control in Flask - Mini Project: Build & Apply

Role-based access control

📖 Scenario: You are building a simple web app where users have different roles like 'admin' and 'user'. You want to control which pages each role can see.

🎯 Goal: Create a Flask app that stores user roles, checks the role before showing a page, and only allows admins to see the admin page.

📋 What You'll Learn

Create a dictionary called users with usernames as keys and roles as values

Create a variable called current_user to simulate the logged-in user

Write a function check_access(role) that returns true if current_user has the given role

Use @app.route to create two pages: '/' for all users and '/admin' only for admins

💡 Why This Matters

🌍 Real World

Role-based access control is used in websites and apps to show or hide pages based on who is logged in, like admins managing content and users viewing it.

💼 Career

Understanding role-based access control is important for backend developers and web developers to secure parts of applications and manage user permissions.

1

Set up user roles dictionary

Create a dictionary called users with these exact entries: 'alice': 'admin', 'bob': 'user', 'carol': 'user'.

Flask

# Your code here

Hint

Think of users as a list of people with their roles.

2

Simulate logged-in user

Create a variable called current_user and set it to the string 'alice' to represent the logged-in user.

Flask

users = {'alice': 'admin', 'bob': 'user', 'carol': 'user'}
# Your code here

Hint

This variable tells the app who is currently using it.

3

Create access check function

Write a function called check_access(role) that returns True if the current_user has the given role, otherwise False. Use the users dictionary to find the role.

Flask

users = {'alice': 'admin', 'bob': 'user', 'carol': 'user'}
current_user = 'alice'
# Your code here

Hint

Use users.get(current_user) to get the role of the logged-in user.

4

Create Flask routes with role checks

Import Flask and abort from flask. Create a Flask app called app. Add two routes: @app.route('/') that returns 'Welcome, user!' for all users, and @app.route('/admin') that returns 'Welcome, admin!' only if check_access('admin') is true, otherwise abort with 403.

Flask

users = {'alice': 'admin', 'bob': 'user', 'carol': 'user'}
current_user = 'alice'

def check_access(role):
    return users.get(current_user) == role

# Your code here

Hint

Use abort(403) to block access if the user is not an admin.

Practice

1. What is the main purpose of role-based access control (RBAC) in a Flask application?

easy

A. To automatically generate user interfaces

B. To speed up the Flask server response time

C. To restrict user actions based on their assigned roles

D. To store user passwords securely

Solution

1. Step 1: Understand RBAC concept

   RBAC means users can only do things allowed by their roles, like admin or user.

2. Step 2: Identify RBAC purpose in Flask

   In Flask, RBAC limits access to routes or actions based on roles.

3. Final Answer:

   To restrict user actions based on their assigned roles -> Option C

4. Quick Check:

   RBAC = restrict actions by role [OK]

Hint: RBAC controls what users can do by their role [OK]

Common Mistakes:

• Confusing RBAC with performance optimization
• Thinking RBAC manages UI generation
• Mixing RBAC with password security

2. Which Flask decorator is commonly used to protect a route so only logged-in users with a specific role can access it?

easy

A. @csrf_protect

B. @login_required

C. @app.route

D. @role_required('admin')

Solution

1. Step 1: Identify decorators for access control

   @login_required ensures user is logged in but does not check role.

2. Step 2: Find decorator checking specific role

   @role_required('admin') restricts access to users with 'admin' role.

3. Final Answer:

   @role_required('admin') -> Option D

4. Quick Check:

   Role check decorator = @role_required [OK]

Hint: Use @role_required to check user roles on routes [OK]

Common Mistakes:

• Using @login_required alone for role checks
• Confusing @app.route with access control
• Mistaking @csrf_protect for role restriction

3. Given this Flask route code snippet:

@app.route('/dashboard')
@role_required('editor')
def dashboard():
    return 'Welcome Editor'

What happens if a logged-in user with role 'viewer' tries to access '/dashboard'?

medium

A. They get redirected or denied access

B. They can access but with limited features

C. They get a server error

D. They see 'Welcome Editor' message

Solution

1. Step 1: Understand role_required decorator effect

   @role_required('editor') allows only users with 'editor' role to access the route.

2. Step 2: Check user role 'viewer' against required 'editor'

   User role 'viewer' does not match 'editor', so access is denied or redirected.

3. Final Answer:

   They get redirected or denied access -> Option A

4. Quick Check:

   Role mismatch = access denied [OK]

Hint: Role mismatch blocks access, not error or partial view [OK]

Common Mistakes:

• Assuming wrong role still shows content
• Expecting server error on role mismatch
• Thinking partial access is automatic

4. Consider this Flask code snippet:

@app.route('/admin')
@role_required('admin')
def admin_panel():
    return 'Admin Panel'

Which of the following is a common mistake that would cause this role check to fail?

medium

A. Not importing the role_required decorator

B. Using @app.route after @role_required

C. Returning a string instead of JSON

D. Defining the function without parentheses

Solution

1. Step 1: Check decorator usage

   role_required must be imported to work; missing import causes failure.

2. Step 2: Verify other options

   @app.route order is flexible; returning string is valid; function definition syntax is correct.

3. Final Answer:

   Not importing the role_required decorator -> Option A

4. Quick Check:

   Missing import breaks decorator [OK]

Hint: Always import decorators before use [OK]

Common Mistakes:

• Assuming decorator order always matters
• Confusing return type with access control
• Syntax errors in function definition

5. You want to create a Flask route /settings that only users with roles 'admin' or 'manager' can access. Which code snippet correctly implements this role-based access control?

hard

A. @app.route('/settings')
@role_required('admin')
@role_required('manager')
def settings():
return 'Settings Page'

B. @app.route('/settings')
def settings():
if current_user.role in ['admin', 'manager']:
return 'Settings Page'
return 'Access Denied'

C. @app.route('/settings')
@role_required(['admin', 'manager'])
def settings():
return 'Settings Page'

D. @app.route('/settings')
@role_required('admin' or 'manager')
def settings():
return 'Settings Page'

Solution

1. Step 1: Analyze multiple role checks

   @app.route('/settings')
   @role_required('admin')
   @role_required('manager')
   def settings():
       return 'Settings Page'

   stacks decorators, which requires both roles simultaneously, not either/or.

2. Step 2: Check list role check in decorator

   @app.route('/settings')
   @role_required(['admin', 'manager'])
   def settings():
       return 'Settings Page'

   assumes role_required accepts list, which may not be supported by default.

3. Step 3: Evaluate logical or misuse

   @app.route('/settings')
   @role_required('admin' or 'manager')
   def settings():
       return 'Settings Page'

   uses 'admin' or 'manager' which evaluates to 'admin' always, incorrect.

4. Step 4: Confirm manual role check

   @app.route('/settings')
   def settings():
       if current_user.role in ['admin', 'manager']:
           return 'Settings Page'
       return 'Access Denied'

   manually checks if user role is in allowed list, correctly allowing either role.

5. Final Answer:

   Option B code with manual role check -> Option B

6. Quick Check:

   Manual role list check allows multiple roles [OK]

Hint: Use if-check for multiple roles if decorator lacks list support [OK]

Common Mistakes:

• Stacking decorators for multiple roles (AND instead of OR)
• Passing list directly to decorator without support
• Using 'or' inside decorator argument incorrectly