Understanding OAuth 2.0: Who Hands the Access Token to Your Web Browser?

Dive into the intricacies of the OAuth 2.0 authorization code flow and learn how access tokens are managed. This guide will clarify how your web browser interacts with access tokens. --- This video is based on the question https://stackoverflow.com/q/70335208/ asked by the user 'Kid_Learning_C' ( https://stackoverflow.com/u/3703783/ ) and on the answer https://stackoverflow.com/a/70349680/ provided by the user 'Michal Trojanowski' ( https://stackoverflow.com/u/1712294/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: OAuth 2.0: In the authorization code flow, who eventually hands the access token to my web browser? Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Understanding OAuth 2.0: Who Hands the Access Token to Your Web Browser? In the world of web applications, securing user information while providing seamless access is a priority. This is where OAuth 2.0 comes into play, particularly its authorization code flow. But have you ever wondered who exactly hands the access token to your web browser during this process? Let’s break this down step-by-step. What is OAuth 2.0? OAuth 2.0 is a framework that allows third-party applications to obtain limited access to a user's data without exposing the user's credentials. It does this through various grant types, which are methods for obtaining an access token. The authorization code flow is one such method, primarily used by web applications. The Authorization Code Flow Explained Step 1: Authorization Request The user initiates a request to access a resource protected by the authorization server. The user is redirected to the authorization server where they authenticate. After authentication, the authorization server redirects back to the application with an authorization code. Step 2: Token Exchange The web browser receives the authorization code and sends it to the application's backend. The backend application then sends a request to the authorization server's /oauth/token endpoint to exchange the authorization code for an access token. Step 3: Establishing User Session Once the application receives the access token from the authorization server, it can establish a user session in the web browser. This is crucial because it differentiates one user from another and maintains their respective sessions within the application. Does the Browser Get the Access Token? Here’s the pivotal clarification: the browser does not need the access token itself. This is fundamentally different from the implicit flow, where the token is sent directly to the browser to be used for subsequent requests. In this code flow, the processes are handled on the server side, isolating access tokens from the browser's direct handling. Why Doesn't the Browser Use the Access Token? Browsers Can't Handle Tokens: Web browsers, by design, don’t understand or manage access tokens the same way they handle cookies or other session identifiers. Session Management: Instead of relying on the token for interaction, the application uses sessions to keep track of user authentication and authorization. The Role of Session Management When your application receives the access token, it should ideally create a session for the logged-in user within the browser context. This means every time that user interacts with the application, the necessary authorizations are managed through that session rather than requiring the actual token to accompany each request. Key Points to Remember: The application handles access tokens securely and uses them to authenticate API calls. If the primary goal is to authenticate users simply, traditional session management may suffice instead of fully implementing OAuth. Conclusion Understanding the behavior of OAuth 2.0 in conjunction with how user sessions are managed allows developers and users alike to grasp fundamental security practices in web applications. In conclusion, while the application manages the access token, it is critical to have effective session management in place to ensure users can interact with the application without exposing sensitive tokens directly in their browsers. This enhances both security and user experience. By demystifying the access token's journey through the authorization code flow, you can better secure your application's interactions with users, all