Reviewer: Valery Smyslov Review result: Has Issues I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. The document introduces an extension to the OAuth protocol that allows resource servers to signal to a client that the authentication event associated with the access token of the current request does not meet its authentication requirements and specify how to meet them. The document is well written and easy to understand. The Security Considerations section looks comprehensive. However, I think that one potential issue is not discussed - the possibility of DoS attacks. The protocol allows the resource server to send the client back to the authorization server for a "better" authentication token. In my opinion it opens a possibility for rogue resource servers to mount a DoS attack by constantly requesting a "better" token. In my understanding a client should respect these replies and each time should ask the authorization server for a "better" (e.g. fresher) token. Depending on the authentication mechanism involved this may be annoying for the user and put an additional load on both the client and the authorization server. -- last-call mailing list last-call@xxxxxxxx https://www.ietf.org/mailman/listinfo/last-call
