Bearer token authentication in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Bearer token in authentication?

A Bearer token is a secret string that a client sends to a server to prove its identity. It works like a digital key that grants access to protected resources.

beginner

How is a Bearer token typically sent in an HTTP request?

It is sent in the HTTP header named Authorization with the word Bearer followed by the token, like this:
Authorization: Bearer <token>.

beginner

Why should Bearer tokens be kept secret?

Because anyone who has the Bearer token can access the protected resources as if they were the authorized user. It is like having a key to someone's house.

intermediate

What happens if a Bearer token is expired or invalid?

The server will reject the request, usually responding with a 401 Unauthorized status, meaning the client must get a new token or re-authenticate.

intermediate

Can Bearer tokens be used over HTTP instead of HTTPS? Why or why not?

Bearer tokens should only be used over HTTPS because HTTP is not secure. If sent over HTTP, the token can be intercepted by attackers and misused.

Where is the Bearer token placed in an HTTP request?

A In the request body

B In the URL query parameters

C In a cookie

D In the Authorization header

Bearer tokens are sent in the Authorization header as 'Bearer <token>'.

What does the server respond with if the Bearer token is missing or invalid?

A 401 Unauthorized

B 200 OK

C 404 Not Found

D 500 Internal Server Error

The server responds with 401 Unauthorized to indicate authentication failure.

Why must Bearer tokens be kept secret?

A Because they contain the user's password

B Because they expire quickly

C Because they allow access to protected resources

D Because they are stored in cookies

Bearer tokens grant access to resources, so if leaked, anyone can use them.

Which protocol should be used to securely send Bearer tokens?

A HTTPS

B FTP

C HTTP

D SMTP

HTTPS encrypts the data, protecting Bearer tokens from interception.

What keyword precedes the token in the Authorization header?

A Token

B Bearer

C Basic

D Digest

The keyword 'Bearer' is used before the token in the Authorization header.

Explain how Bearer token authentication works in a REST API.

Think about the token as a key sent with each request.

Describe why it is important to use HTTPS when using Bearer tokens.

Consider what happens if data is sent over an insecure connection.

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