Token-based authentication in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to generate a secure token for user authentication.

Ruby on Rails

token = SecureRandom.[1](24)

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

Ahex

Bbase64

Cuuid

Drandom

Attempts:

3 left

💡 Hint

Common Mistakes

Using SecureRandom.random which does not exist.

Using SecureRandom.uuid which returns a UUID, not a hex string.

The SecureRandom.hex(24) method generates a random hexadecimal string of length 48 characters, suitable for tokens.

2fill in blank

medium

Complete the code to add secure password authentication to the User model.

Ruby on Rails

has_secure_[1]

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

Asession

Bpassword

Ctoken

Dauthentication

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use has_secure_token which is a different method.

Using has_secure_authentication which does not exist.

The has_secure_password method adds password hashing and authentication features to the User model.

3fill in blank

hard

Fix the error in the controller method that finds a user by token.

Ruby on Rails

user = User.find_by([1]: params[:token])

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

Aauth_token

Btoken

Cauthentication_token

Daccess_token

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'token' which may not be the attribute name.

Using 'access_token' which is not standard in this context.

The User model typically stores the token in the auth_token attribute, so the query should use that key.

4fill in blank

hard

Fill both blanks to generate and save a new token for the user.

Ruby on Rails

user.[1] = SecureRandom.[2](20)
user.save!

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

Aauth_token

Bhex

Crandom

Dtoken

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'token' instead of 'auth_token' as attribute.

Using SecureRandom.random which does not exist.

The auth_token attribute stores the token, and SecureRandom.hex(20) generates a secure hex string token.

5fill in blank

hard

Fill all three blanks to create a before_action that authenticates user by token.

Ruby on Rails

before_action :[1], only: [:show, :update]

def [2]
  @user = User.find_by([3]: request.headers['Authorization'])
  head :unauthorized unless @user
end

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

Aauthenticate_user

Bauth_token

Ctoken

Dauthorize_user

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for before_action and method.

Using 'token' instead of 'auth_token' as attribute.

The method authenticate_user is used as a before_action. It finds the user by auth_token from the Authorization header and denies access if not found.

Practice

1. What is the main purpose of token-based authentication in Rails?

easy

A. To identify users securely without requiring passwords every time

B. To store user passwords in plain text

C. To create server sessions for each user

D. To encrypt database records automatically

Solution

1. Step 1: Understand token-based authentication

   Token-based authentication uses a secret token to identify users securely without needing passwords repeatedly.

2. Step 2: Compare options

   Only To identify users securely without requiring passwords every time correctly describes this purpose; others describe unrelated or incorrect behaviors.

3. Final Answer:

   To identify users securely without requiring passwords every time -> Option A

4. Quick Check:

   Token-based authentication = Identify users securely without passwords [OK]

Hint: Tokens replace passwords for repeated user identification [OK]

Common Mistakes:

• Confusing tokens with password storage
• Thinking tokens create server sessions
• Assuming tokens encrypt data automatically

2. Which Rails method adds a secure token to a model for token-based authentication?

easy

A. has_secure_password

B. validates_token

C. has_secure_token

D. generate_token

Solution

1. Step 1: Recall Rails token helper methods

   Rails provides has_secure_token to add a secure token to models easily.

2. Step 2: Eliminate incorrect options

   has_secure_password is for passwords, not tokens; others are not valid Rails methods.

3. Final Answer:

   has_secure_token -> Option C

4. Quick Check:

   Token method in Rails = has_secure_token [OK]

Hint: Remember: token method is 'has_secure_token' not 'password' [OK]

Common Mistakes:

• Confusing has_secure_token with has_secure_password
• Using non-existent methods like generate_token
• Assuming validates_token is built-in

3. Given the model code:

class User < ApplicationRecord
  has_secure_token :auth_token
end

user = User.new
user.save
puts user.auth_token.nil?

What will be the output?

medium

A. false

B. Error: undefined method

C. nil

D. true

Solution

1. Step 1: Understand has_secure_token behavior

   When a new User is saved, Rails automatically generates a unique token for auth_token, so it won't be nil.

2. Step 2: Evaluate the output of puts user.auth_token.nil?

   Since auth_token is set, nil? returns false, so output is false.

3. Final Answer:

   false -> Option A

4. Quick Check:

   Token generated on save = false for nil? [OK]

Hint: Tokens auto-generate on save, so nil? returns false [OK]

Common Mistakes:

• Assuming token is nil before save
• Expecting nil output instead of false
• Confusing method names causing errors

4. Identify the error in this token authentication setup:

class ApiUser < ApplicationRecord
  has_secure_token :auth_token
end

user = ApiUser.new
user.auth_token = nil
user.save
puts user.auth_token.nil?

medium

A. user.save will raise an exception due to nil token

B. has_secure_token requires a token column named 'token', not 'auth_token'

C. Token is not generated because auth_token was manually set to nil before save

D. No error; output will be false

Solution

1. Step 1: Recall has_secure_token generation condition

   has_secure_token :auth_token generates a token if auth_token.blank? before save (nil.blank? returns true).

2. Step 2: Trace code execution

   Setting user.auth_token = nil keeps it blank, so save generates the token. user.auth_token.nil? returns false. No error.

3. Final Answer:

   No error; output will be false -> Option D

4. Quick Check:

   nil.blank? = true -> generates token [OK]

Hint: Setting to nil does NOT prevent generation; nil.blank? = true [OK]

Common Mistakes:

• Thinking setting to nil prevents token generation
• Expecting save to raise error on nil token
• Thinking output is true because manually set to nil

5. You want to secure an API in Rails using token-based authentication. Which approach correctly checks the token sent in request headers against the stored user token?

hard

A. Store tokens in cookies and check them with session[:token]

B. Use before_action to find user by auth_token from request.headers['Authorization'] and reject if not found

C. Use has_secure_password to verify token in params

D. Generate a new token on every request and compare with stored token

Solution

1. Step 1: Understand token authentication in APIs

   APIs commonly send tokens in headers; Rails can check request.headers['Authorization'] to find the user.

2. Step 2: Evaluate options for correctness

   Use before_action to find user by auth_token from request.headers['Authorization'] and reject if not found correctly uses before_action to authenticate by token. Options B and C misuse cookies and password helpers. Generate a new token on every request and compare with stored token is insecure and impractical.

3. Final Answer:

   Use before_action to find user by auth_token from request.headers['Authorization'] and reject if not found -> Option B

4. Quick Check:

   API token check = before_action with header token [OK]

Hint: Check token in headers with before_action for API security [OK]

Common Mistakes:

• Using cookies or sessions for API token storage
• Confusing password helpers with token verification
• Generating new token each request causing mismatch