OAuth2 overview in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Flask-OAuthlib client.

Flask

from flask_oauthlib.client import [1]

Drag options to blanks, or click blank then click option'

AOAuth

BOAuth2

COAuthClient

DOAuthProvider

Attempts:

3 left

💡 Hint

Common Mistakes

Using OAuth2 instead of OAuth

Using OAuthClient which does not exist

The Flask-OAuthlib client is imported using OAuth.

2fill in blank

medium

Complete the code to create an OAuth object in a Flask app.

Flask

oauth = [1](app)

Drag options to blanks, or click blank then click option'

AOAuthProvider

BOAuth2

COAuth

DOAuthClient

Attempts:

3 left

💡 Hint

Common Mistakes

Using OAuth2 which is not the class name

Using OAuthProvider which is for servers

You create an OAuth object by calling OAuth(app) passing the Flask app.

3fill in blank

hard

Fix the error in the OAuth remote app registration code.

Flask

google = oauth.remote_app(
    'google',
    consumer_key='[1]',
    consumer_secret='YOUR_SECRET',
    request_token_params={'scope': 'email'},
    base_url='https://www.googleapis.com/oauth2/v1/',
    request_token_url=None,
    access_token_method='POST',
    access_token_url='https://accounts.google.com/o/oauth2/token',
    authorize_url='https://accounts.google.com/o/oauth2/auth'
)

Drag options to blanks, or click blank then click option'

AGOOGLE_CLIENT_ID

BGOOGLE_SECRET

CCLIENT_ID

DAPI_KEY

Attempts:

3 left

💡 Hint

Common Mistakes

Using the secret instead of the client ID

Using API_KEY which is unrelated

The consumer_key should be your Google client ID, often stored in a variable like GOOGLE_CLIENT_ID.

4fill in blank

hard

Fill both blanks to complete the OAuth token getter function.

Flask

@google.tokengetter
def get_google_oauth_token():
    return [1].get('access_token'), [2]

Drag options to blanks, or click blank then click option'

Asession

BNone

Crequest

Dcurrent_user

Attempts:

3 left

💡 Hint

Common Mistakes

Returning request instead of session

Returning current_user which is unrelated

The tokengetter returns the access token stored in the Flask session and None for the token secret.

5fill in blank

hard

Fill all three blanks to complete the OAuth login route using Flask.

Flask

@app.route('/login')
def login():
    return [1].authorize(callback=[2]('authorized', _external=True))

@app.route('/login/authorized')
def authorized():
    resp = [3].authorized_response()
    if resp is None or resp.get('access_token') is None:
        return 'Access denied.'
    session['access_token'] = resp['access_token']
    return 'You are logged in!'

Drag options to blanks, or click blank then click option'

Agoogle

Burl_for

Dredirect

Attempts:

3 left

💡 Hint

Common Mistakes

Using redirect instead of google.authorize

Not using url_for for callback URL

The login route calls google.authorize with a callback URL generated by url_for. The authorized route uses google.authorized_response() to get the token.

Practice

1. What is the main purpose of OAuth2 in a Flask application?

easy

A. Store user passwords securely in the Flask app database

B. Allow users to log in using external services without sharing passwords

C. Encrypt all data sent between client and server

D. Automatically create user accounts without permission

Solution

1. Step 1: Understand OAuth2 role

   OAuth2 lets apps use other services for login without handling user passwords directly.

2. Step 2: Identify correct purpose in Flask context

   Flask apps use OAuth2 to let users sign in via external providers safely.

3. Final Answer:

   Allow users to log in using external services without sharing passwords -> Option B

4. Quick Check:

   OAuth2 = external login without password sharing [OK]

Hint: OAuth2 means login without storing passwords [OK]

Common Mistakes:

• Thinking OAuth2 stores passwords
• Confusing OAuth2 with encryption
• Assuming OAuth2 creates accounts automatically

2. Which Flask extension is commonly used to simplify OAuth2 integration?

easy

A. Flask-WTF

B. Flask-SQLAlchemy

C. Authlib

D. Flask-Mail

Solution

1. Step 1: Recall Flask extensions for OAuth2

   Authlib is a popular Flask extension designed to handle OAuth2 easily.

2. Step 2: Eliminate unrelated extensions

   Flask-SQLAlchemy manages databases, Flask-WTF handles forms, Flask-Mail sends emails, so they don't handle OAuth2.

3. Final Answer:

   Authlib -> Option C

4. Quick Check:

   OAuth2 in Flask = Authlib [OK]

Hint: Authlib is for OAuth2 in Flask [OK]

Common Mistakes:

• Choosing Flask-SQLAlchemy for OAuth2
• Confusing form or mail extensions with OAuth2
• Not knowing Authlib's purpose

3. Given this Flask OAuth2 code snippet, what will print(user_info) output after successful login?

from authlib.integrations.flask_client import OAuth
app = Flask(__name__)
oauth = OAuth(app)
google = oauth.register('google', client_id='id', client_secret='secret', access_token_url='https://accounts.google.com/o/oauth2/token', authorize_url='https://accounts.google.com/o/oauth2/auth', api_base_url='https://www.googleapis.com/oauth2/v1/', client_kwargs={'scope': 'openid email profile'})

@app.route('/login')
def login():
    redirect_uri = url_for('authorize', _external=True)
    return google.authorize_redirect(redirect_uri)

@app.route('/authorize')
def authorize():
    token = google.authorize_access_token()
    user_info = google.get('userinfo').json()
    print(user_info)
    return 'Logged in'

medium

A. Empty dictionary because token is invalid

B. An error because 'userinfo' endpoint is missing

C. A string 'Logged in' printed to console

D. A dictionary with user's email, name, and profile info

Solution

1. Step 1: Understand OAuth2 flow in code

   After login, the app gets an access token and calls 'userinfo' endpoint to get user data as JSON.

2. Step 2: Analyze user_info content

   The google.get('userinfo').json() returns a dictionary with user details like email and name.

3. Final Answer:

   A dictionary with user's email, name, and profile info -> Option D

4. Quick Check:

   OAuth2 userinfo call = user data dict [OK]

Hint: OAuth2 userinfo returns user data dictionary [OK]

Common Mistakes:

• Expecting a string instead of dictionary
• Assuming endpoint is missing
• Thinking token is invalid without error

4. What is wrong with this Flask OAuth2 snippet?

@app.route('/authorize')
def authorize():
    token = google.authorize_access_token
    user_info = google.get('userinfo').json()
    return user_info

medium

A. Missing parentheses when calling authorize_access_token

B. Using 'userinfo' instead of 'user_info' endpoint

C. Returning JSON directly causes syntax error

D. No redirect URI specified in authorize route

Solution

1. Step 1: Check method call syntax

   The code uses google.authorize_access_token without parentheses, so it references the method, not calls it.

2. Step 2: Understand effect of missing parentheses

   Without calling the method, token is a function object, causing errors later.

3. Final Answer:

   Missing parentheses when calling authorize_access_token -> Option A

4. Quick Check:

   Method call needs () [OK]

Hint: Always add () to call methods [OK]

Common Mistakes:

• Forgetting parentheses on method calls
• Confusing endpoint names
• Assuming JSON return causes error

5. You want your Flask app to request only the user's email and profile during OAuth2 login with Google. Which scope value should you use when registering the OAuth client?

hard

A. 'openid email profile'

B. 'read write'

C. 'user:email user:profile'

D. 'email profile openid offline_access'

Solution

1. Step 1: Identify correct OAuth2 scopes for Google

   Google uses 'openid email profile' scopes to request user's email and profile info.

2. Step 2: Eliminate incorrect scopes

   'read write' is generic, 'user:email user:profile' is GitHub style, 'offline_access' requests refresh tokens, not needed here.

3. Final Answer:

   'openid email profile' -> Option A

4. Quick Check:

   Google OAuth2 scopes for email/profile = 'openid email profile' [OK]

Hint: Use 'openid email profile' for Google OAuth2 scopes [OK]

Common Mistakes:

• Using GitHub or generic scopes
• Adding unnecessary offline_access scope
• Confusing scope syntax