Understanding OAuth and JWT in Azure Entra ID: Differences and Use Case Scenarios

Azure Entra ID, formerly known as Azure Active Directory (Azure AD), leverages various protocols and technologies to ensure secure and efficient identity management and access control. Among these technologies are OAuth and JWT (JSON Web Token), which play crucial roles in authentication and authorization processes. This article explores the concepts of OAuth and JWT, their differences, and their use case scenarios within Azure Entra ID.

OAuth: Open Authorization

Overview

OAuth (Open Authorization) is an open standard protocol that enables secure, token-based authorization for web, mobile, and desktop applications. It allows third-party applications to obtain limited access to user resources without exposing user credentials.

Key Components

• Resource Owner: The user who owns the resource.
• Client: The application requesting access to the user’s resource.
• Resource Server: The server hosting the resource (e.g., an API).
• Authorization Server: The server that authenticates the user and issues access tokens.

OAuth Flow

1. Authorization Request: The client requests authorization from the user to access their resource.
2. Authorization Grant: The user grants authorization, typically by logging in and consenting.
3. Access Token Request: The client requests an access token from the authorization server using the authorization grant.
4. Access Token Response: The authorization server issues an access token.
5. Resource Access: The client uses the access token to access the resource server.

Use Case Scenarios

• Single Sign-On (SSO): Allow users to sign in to multiple applications with a single set of credentials.
• API Access: Enable third-party applications to access APIs on behalf of the user without sharing their credentials.
• Delegated Access: Allow applications to perform actions on behalf of the user, such as posting to social media or accessing files.

JSON Web Token (JWT)

Overview

JWT is a compact, URL-safe means of representing claims to be transferred between two parties. It is commonly used in authentication and authorization contexts, particularly within OAuth flows.

JWT Structure

• Header: Contains metadata about the token, including the type of token (JWT) and the signing algorithm.
• Payload: Contains claims, which are statements about an entity (usually the user) and additional data.
• Signature: Ensures the token’s integrity and authenticity. It is created by signing the header and payload with a secret key or private key.

Example JWT

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

Use Case Scenarios

• Stateless Authentication: Use JWTs for stateless authentication in web applications, allowing for scalable and efficient session management.
• API Authorization: Securely pass information between the client and server, such as user roles and permissions, without requiring server-side session storage.
• Mobile Applications: Implement secure token-based authentication in mobile apps, reducing the need for constant server communication.

Differences Between OAuth and JWT

Purpose

• OAuth: Primarily a framework for authorization, enabling third-party applications to obtain limited access to user resources without exposing credentials.
• JWT: A token format used for securely transmitting information between parties, often used within OAuth to represent access tokens and ID tokens.

Components

• OAuth: Involves multiple components (resource owner, client, resource server, authorization server) and a multi-step flow for obtaining and using access tokens.
• JWT: A self-contained token with a simple structure (header, payload, signature) that can be used within OAuth or independently.

Usage

• OAuth: Used for obtaining access tokens, managing authorization flows, and enabling third-party application access to resources.
• JWT: Used for transmitting claims, representing access tokens, and providing stateless authentication.

Security

• OAuth: Focuses on secure delegation of access, often incorporating JWT for token representation.
• JWT: Provides security through its signed tokens, ensuring the integrity and authenticity of the transmitted information.

Use Case Scenarios in Azure Entra ID

OAuth Use Cases

1. Delegated Access for APIs: Azure Entra ID uses OAuth to allow applications to access Microsoft Graph API on behalf of a user. For example, a third-party CRM application can access a user’s calendar data with their consent.
2. Single Sign-On (SSO): Organizations can implement SSO across multiple applications using OAuth, allowing users to sign in once and gain access to all integrated applications seamlessly.

JWT Use Cases

1. Access Tokens in OAuth: Azure Entra ID issues JWTs as access tokens in OAuth flows. These tokens contain claims about the user and the permissions granted, which the client application uses to access resources.
2. ID Tokens for Authentication: In OpenID Connect (an identity layer on top of OAuth 2.0), Azure Entra ID issues JWTs as ID tokens, containing user identity information that applications can use for authentication.
3. API Security: Azure Entra ID uses JWTs to secure API endpoints. When a client makes a request to an API, it includes the JWT in the authorization header, allowing the API to verify the token and grant access based on the claims.

Conclusion

OAuth and JWT are integral to Azure Entra ID’s identity and access management capabilities. OAuth provides a robust framework for secure authorization and delegated access, while JWT offers a compact and secure way to transmit claims. Understanding their differences and appropriate use cases allows organizations to implement secure and efficient authentication and authorization mechanisms across their applications and services. Whether enabling SSO, securing APIs, or managing access tokens, Azure Entra ID’s support for OAuth and JWT ensures a comprehensive approach to identity management.