Requires reading first Advanced Pipeline and the Authentication Feature.

Authentication feature creates an AuthenticationPipeline which is executed right after the Features phase in the call pipeline. All authentication protocols such as basic, digest, oauth are implemented as interceptors on AuthenticationPipeline.

Phases:

AuthenticationPipeline has two phases:

• CheckAuthentication – phase for checking if a user is already authenticated before all authentication mechanisms kick in.
• RequestAuthentication – phase for authentication mechanisms to plug into.

The subject of the pipeline is an AuthenticationContext instance.

Protocol:

• Auth provider interceptor tries to find a Principal in the context of the current call.
• If the principal is found, it is returned, and the pipeline is finished.
• If the principal is not found, the provider will add a challenge to AuthenticationContext.
• At the end of the pipeline, if there is no principal, we start calling challenges in order.
• Whichever challenge succeeds first wins.

Example Flow:

• Basic auth examines the Authorization header.
• If it’s missing or invalid, or the user is not recognized, a 401 Unauthorized is sent back to the client, and the current call ends.
• The browser displays a login dialog, and after credentials are provided, it makes a new HTTP request with a proper Authorization header.
• Basic auth provider examines the new header, extracts credentials, and verifies them.
• If the credentials are valid, the principal is attached to the call. If not, a 401 is returned to the client again.