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Last Call Review of draft-ietf-oauth-step-up-authn-challenge-12

Request Review of draft-ietf-oauth-step-up-authn-challenge
Requested revision No specific revision (document currently at 17)
Type Last Call Review
Team Security Area Directorate (secdir)
Deadline 2023-03-03
Requested 2023-02-17
Authors Vittorio Bertocci , Brian Campbell
I-D last updated 2023-03-01
Completed reviews Secdir Last Call review of -12 by Valery Smyslov (diff)
Artart Last Call review of -12 by Robert Sparks (diff)
Genart Last Call review of -11 by Christer Holmberg (diff)
Artart Telechat review of -13 by Robert Sparks (diff)
Httpdir Telechat review of -13 by Mark Nottingham (diff)
Assignment Reviewer Valery Smyslov
State Completed
Request Last Call review on draft-ietf-oauth-step-up-authn-challenge by Security Area Directorate Assigned
Posted at
Reviewed revision 12 (document currently at 17)
Result Has issues
Completed 2023-03-01
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.