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Start for freeUnderstanding Modern Authentication for Web Applications
Modern authentication mechanisms have become a cornerstone for securing web applications. With the evolution of web technologies, the traditional ways of authenticating users have shifted towards more secure and user-friendly methods. Stuart Kwan, a Program Manager on the Azure Active Directory team, provides a detailed overview of how modern authentication works, focusing on web applications.
The Role of Identity Providers
At the heart of modern authentication lies the concept of an identity provider, a crucial component that acts as an intermediary between the user and the web application. When a user, referred to as Alice in our example, attempts to access a web application, her initial unauthenticated state is recognized by the application. To authenticate Alice, the application relies on a trust relationship with an identity provider.
Initiating the Authentication Process
To sign Alice in, the website redirects her browser to the identity provider. This redirection is an essential step where the browser serves as an agent, carrying an authentication request to the identity provider. The parameters contained in the URL's query string, following the question mark, are the actual parameters of the sign-in request.
User Authentication at the Identity Provider
Alice may authenticate herself using various methods such as entering a username and password, presenting a smart card, or using an authenticator app. Once the identity provider verifies Alice's credentials, it issues a token, which is sent back to the website through an HTTP POST, with the token embedded in the body.
Authentication Protocol Binding
This process involves specific bindings - methods of how authentication requests and responses are tied to the communication protocol. A common approach is the use of redirect binding for sending the request and post binding for returning the token.
Validating the Token
Upon receiving the token, the website validates its signature using the identity provider’s public sign-in key, which is available through a documented endpoint. Once validated, Alice is considered authenticated, and her identity is confirmed through the claims within the token.
Maintaining Authentication State
To recognize Alice in subsequent requests, the website places a signed HTTP cookie in her browser. This cookie, a form of security token itself, ensures that Alice's browser communicates her authenticated state in every interaction with the website.
The Security Protocols
The industry utilizes various protocols like SAML, OpenID Connect, and WS Federation to implement this authentication flow. While they all serve the same fundamental purpose, they differ in encoding methods and token types. Notably, OpenID Connect employs JSON for both tokens and protocol descriptions, differing from the XML used in SAML and WS Federation.
Conclusion
Modern authentication for web applications introduces a sophisticated mechanism to secure user interactions. By leveraging identity providers, redirect and post bindings, and secure tokens, web applications can offer a seamless yet secure user experience. Understanding these processes and protocols is essential for developers and IT professionals aiming to enhance web application security in the evolving digital landscape.
For a deeper dive into modern authentication mechanisms, watch the full video here.
