Bearer token authentication in Rest API - Mini Project: Build & Apply

Bearer Token Authentication

📖 Scenario: You are building a simple REST API that requires users to authenticate using a bearer token. This is a common way to secure APIs by sending a secret token with each request.

🎯 Goal: Create a REST API endpoint that checks for a bearer token in the request headers and returns a success message if the token is valid, or an error message if it is missing or invalid.

📋 What You'll Learn

Create a variable called VALID_TOKEN with the exact value 'abc123token'.

Create a function called check_token that takes a headers dictionary as input.

In check_token, check if the Authorization header exists and starts with 'Bearer '.

Extract the token from the Authorization header and compare it to VALID_TOKEN.

Return True if the token matches, otherwise False.

Create a function called api_endpoint that takes a headers dictionary as input.

Use check_token inside api_endpoint to verify the token.

Return the string 'Access granted' if the token is valid, or 'Access denied' if not.

Print the result of calling api_endpoint with the headers {'Authorization': 'Bearer abc123token'}.

💡 Why This Matters

🌍 Real World

Bearer token authentication is widely used to secure APIs in web and mobile apps. It helps ensure that only authorized users can access protected resources.

💼 Career

Understanding bearer token authentication is essential for backend developers, API developers, and anyone working with secure web services.

1

Create the valid token variable

Create a variable called VALID_TOKEN and set it to the string 'abc123token'.

Rest API

# Create the valid token variable
# Your code here

Hint

Think of VALID_TOKEN as the secret key that the API will accept.

2

Create the token check function

Create a function called check_token that takes a parameter headers. Inside the function, check if the Authorization header exists in headers and starts with 'Bearer '. Return True if the token after 'Bearer ' matches VALID_TOKEN, otherwise return False.

Rest API

VALID_TOKEN = 'abc123token'

def check_token(headers):
    # Your code here

Hint

Use headers.get('Authorization', '') to safely get the header. Then check if it starts with 'Bearer '. Extract the token by slicing the string after 'Bearer '.

3

Create the API endpoint function

Create a function called api_endpoint that takes a parameter headers. Inside the function, use check_token(headers) to verify the token. Return the string 'Access granted' if the token is valid, otherwise return 'Access denied'.

Rest API

VALID_TOKEN = 'abc123token'

def check_token(headers):
    auth = headers.get('Authorization', '')
    if auth.startswith('Bearer '):
        token = auth[len('Bearer '):]
        return token == VALID_TOKEN
    return False

def api_endpoint(headers):
    # Your code here

Hint

Use an if statement to check the result of check_token(headers). Return the correct string based on the result.

4

Print the API endpoint result

Print the result of calling api_endpoint with the headers dictionary {'Authorization': 'Bearer abc123token'}.

Rest API

VALID_TOKEN = 'abc123token'

def check_token(headers):
    auth = headers.get('Authorization', '')
    if auth.startswith('Bearer '):
        token = auth[len('Bearer '):]
        return token == VALID_TOKEN
    return False

def api_endpoint(headers):
    if check_token(headers):
        return 'Access granted'
    else:
        return 'Access denied'

print(api_endpoint({'Authorization': 'Bearer abc123token'}))  # Your code here

Hint

Use print() to show the result of api_endpoint called with the correct headers.

Practice

1. What is the main purpose of a Bearer token in REST API authentication?

easy

A. To prove the identity of the client making the request

B. To encrypt the data sent between client and server

C. To specify the format of the response data

D. To define the API endpoint URL

Solution

1. Step 1: Understand Bearer token role

   A Bearer token is a secret key sent with requests to prove who the client is.

2. Step 2: Identify main purpose

   It helps the server know the client's identity and permissions.

3. Final Answer:

   To prove the identity of the client making the request -> Option A

4. Quick Check:

   Bearer token = client identity proof [OK]

Hint: Bearer tokens prove who you are, not encrypt data [OK]

Common Mistakes:

• Thinking Bearer tokens encrypt data
• Confusing token with API endpoint
• Assuming token defines response format

2. Which of the following is the correct way to include a Bearer token in an HTTP request header?

easy

A. Token: Bearer your_token_here

B. Authorization: Bearer your_token_here

C. Authorization: Token your_token_here

D. Bearer: Authorization your_token_here

Solution

1. Step 1: Recall Bearer token header format

   The standard way is to use the 'Authorization' header with the word 'Bearer' followed by the token.

2. Step 2: Match correct syntax

   Authorization: Bearer your_token_here matches the correct syntax: 'Authorization: Bearer your_token_here'.

3. Final Answer:

   Authorization: Bearer your_token_here -> Option B

4. Quick Check:

   Authorization header + Bearer keyword = correct format [OK]

Hint: Use 'Authorization: Bearer <token>' exactly [OK]

Common Mistakes:

• Using 'Token' instead of 'Bearer'
• Swapping header name and value order
• Omitting 'Bearer' keyword

3. Given this Python code snippet using the requests library, what will be the output if the token is invalid?

import requests
headers = {"Authorization": "Bearer invalid_token"}
response = requests.get("https://api.example.com/data", headers=headers)
print(response.status_code)

medium

A. 200

B. 404

C. 401

D. 500

Solution

1. Step 1: Understand HTTP status codes for authentication

   401 means Unauthorized, which is returned when authentication fails due to invalid token.

2. Step 2: Analyze the code behavior with invalid token

   The server will reject the request and respond with 401 Unauthorized status code.

3. Final Answer:

   401 -> Option C

4. Quick Check:

   Invalid token = 401 Unauthorized [OK]

Hint: Invalid token usually returns 401 status code [OK]

Common Mistakes:

• Assuming 200 means success with invalid token
• Confusing 404 Not Found with authentication error
• Thinking server error 500 occurs for invalid token

4. You wrote this code to send a Bearer token but the server always responds with 401 Unauthorized. What is the likely error?

headers = {"Authorization": "bearer mytoken123"}
response = requests.get(url, headers=headers)

medium

A. The URL is incorrect

B. The token string is missing

C. The header name should be 'Token' instead of 'Authorization'

D. The word 'bearer' should be capitalized as 'Bearer'

Solution

1. Step 1: Check Bearer token header case sensitivity

   The 'Bearer' keyword in the Authorization header is case sensitive and must be capitalized.

2. Step 2: Identify the error in the code

   The code uses 'bearer' in lowercase, causing the server to reject the token and respond 401.

3. Final Answer:

   The word 'bearer' should be capitalized as 'Bearer' -> Option D

4. Quick Check:

   Bearer keyword is case sensitive [OK]

Hint: Capitalize 'Bearer' exactly in Authorization header [OK]

Common Mistakes:

• Using lowercase 'bearer' keyword
• Changing header name from 'Authorization'
• Ignoring token format errors

5. You want to secure an API endpoint so only requests with a valid Bearer token can access it. Which of these is the best approach to implement this in your REST API server?

hard

A. Check the 'Authorization' header for a Bearer token, validate it, and reject requests without valid tokens

B. Allow all requests but log the Bearer token if present

C. Require the token as a URL query parameter instead of header

D. Ignore tokens and rely on IP address filtering

Solution

1. Step 1: Understand secure API access with Bearer tokens

   Secure APIs check the Authorization header for a valid Bearer token to authenticate requests.

2. Step 2: Identify best practice for token validation

   Rejecting requests without valid tokens ensures only authorized clients access the endpoint.

3. Final Answer:

   Check the 'Authorization' header for a Bearer token, validate it, and reject requests without valid tokens -> Option A

4. Quick Check:

   Validate token in Authorization header to secure API [OK]

Hint: Validate Bearer token in Authorization header to secure API [OK]

Common Mistakes:

• Using query parameters for tokens (less secure)
• Allowing requests without token validation
• Relying on IP filtering alone