Oauth2 JWT Interview Questions and Answers | Grant types, Scope, Access Token, Claims | Code Decode

Summary

This video script offers an in-depth exploration of OAuth 2.0 and OpenID Connect (OIDC), focusing on their role in authorization and authentication within secure applications. It explains the distinction between authentication and authorization using a relatable security checkpoint analogy and illustrates OAuth 2.0's functionality with the example of signing into Twitter through Google. The script further clarifies that OAuth 2.0 is solely for authorization, not authentication, and delegates user authentication to services like Google. It also introduces Auth0 as a one-stop solution for authentication and authorization, simplifying the process for developers by providing access tokens and other necessary security measures. The explanation of JWT (JSON Web Tokens), their structure, and the importance of claims within them, rounds out the educational content, aiming to equip viewers with a comprehensive understanding of these critical security protocols.

Takeaways

• 🔐 OAuth 2.0 is an authorization framework, not an authentication protocol. It focuses on determining what resources a user can access, not verifying their identity.
• 👥 Authentication and authorization are two distinct concepts: Authentication verifies who a person is, while authorization determines what they can access.
• 📲 An example of OAuth 2.0 in action is signing into Twitter via Google or Apple, where the user's identity is already authenticated, and the application requests authorization to access specific user data.
• 📈 The script introduces 'Next Level', an app designed to showcase expertise and skills, providing professional ratings that can lead to better job opportunities.
• 🚫 OAuth 1.0 is deprecated and not backward compatible with OAuth 2.0, which is the widely used version for authorization purposes.
• 💼 Auth0 is presented as a one-stop solution for authentication and authorization, offering endpoints and logic to simplify security implementations for developers.
• 🔗 The script explains that Auth0 uses OAuth 2.0 internally for authorization and provides additional features like ID tokens as part of OpenID Connect.
• 📜 The importance of scopes in OAuth 2.0 is highlighted, defining what data or actions an application is authorized to access.
• 🔑 JWT (JSON Web Tokens) is the widely accepted format for access tokens, providing a secure way to transmit information between parties by using a signed cryptographic hash.
• 📝 Claims within JWT tokens are key-value pairs that carry metadata about the user, with types including reserved, public, and private claims.
• 🛡️ The backend API must validate JWT tokens to ensure they are from a legitimate user and have not been tampered with, checking the signature, token type, algorithm, and expiration time.

Q & A

What is OAuth and how does it relate to security?

OAuth is an open standard for authorization. It is not about authentication but rather about what resources a user is allowed to access within an application. It delegates the user authentication to a service that holds the user account and asks for permission to access certain data, known as a scope.

Can you explain the difference between authentication and authorization using an example?

Sure, if you go to a building and meet a security checkpoint, the watchman asks for your identity (authentication) and then asks where you want to go (authorization). Authentication confirms who you are, while authorization determines if you're allowed to access a specific resource.

How does OAuth 2.0 work with services like Google for authorization?

OAuth 2.0 works by allowing an application, like Twitter, to delegate its authentication responsibility to Google. When you sign in with Google, Twitter asks for authorization to access specific data like your name, email, and profile picture stored with Google. This process is called getting a scope.

What is the purpose of a scope in OAuth 2.0?

A scope in OAuth 2.0 defines what data or actions the application is requesting access to. It's like asking for specific permissions from the user to access certain pieces of information they have stored with another service.

What is Auth0 and how does it relate to OAuth 2.0?

Auth0 is an organization that provides a One-Stop solution for authentication and authorization. It internally uses OAuth 2.0 to manage access tokens and authentication for developers, making it easier to secure applications without having to implement these features from scratch.

Can you describe the role of an authorization server in OAuth 2.0?

An authorization server in OAuth 2.0 is responsible for issuing access tokens to the client after successfully authenticating the user and obtaining authorization from them. It's essentially the service that manages and grants permissions for accessing resources.

What is the difference between Auth0 and OAuth 2.0?

OAuth 2.0 is an authorization framework, while Auth0 is a service that implements OAuth 2.0 and provides additional features for authentication and authorization. Auth0 simplifies the process for developers by handling the complexities of OAuth 2.0.

What are the two basic endpoints that Auth0 provides for OAuth 2.0?

Auth0 provides two basic endpoints: '/authorize' which is used to obtain the authorization grant, and '/token' which is used to exchange the grant for an access token.

Why are access tokens used instead of sending information as plain JSON objects?

Access tokens are used for security purposes. They prevent malicious users from tampering with requests and accessing unauthorized data. Access tokens are verified by the client application to ensure they are legitimate.

What is JWT and why is it used for access tokens?

JWT stands for JSON Web Token. It is a format used for securely transmitting information between parties. It's used for access tokens because it is a signed cryptographic hash that ensures the content cannot be altered by malicious parties.

Can you explain the structure of a JWT token?

A JWT token consists of three parts separated by dots: header, payload, and signature. The header specifies the type of token and the signing algorithm. The payload contains claims or metadata about the user. The signature is created using the header, payload, and a secret key to ensure the token's integrity.

What are claims in a JWT token?

Claims in a JWT token are key-value pairs that provide information about the user. They can be of three types: reserved claims, which are predefined and recommended (like 'iss', 'exp', 'sub', 'aud'); public claims, which are defined in a public registry; and private claims, which are custom and specific to the application.

How does a backend API validate an access token?

A backend API validates an access token by decoding the header and payload, checking the token's type and algorithm, using the secret key to verify the signature, and ensuring the token has not expired. If all checks pass, the token is considered valid.