Re: [Ace] Comment about error responses in draft-ietf-ace-oauth-authz-21

[Ludwig Seitz <[e-mail]>]

On 18/02/2019 15:59, Sebastian Echeverria wrote:
> Hello,
> 
> I have a short comment about error responses from an RS in 
> draft-ietf-ace-oauth-authz-21. More specifically, my question is about 
> section 5.8.2. In the second paragraph, it states “The response code 
> MUST be 4.01 (Unauthorized) in case the client has not performed the 
> proof-of-possession, or if RS has no valid access token for the client.” 
> I am assuming this means that if the client is trying to access a 
> resource and sending a pop key id that is not known by the RS, either 
> because the RS has never seen it or because it is associated to a token 
> that has already been removed from the RS, then this is how the RS 
> should reply.
> 
> If this is the case, I am a bit confused on how to implement this when 
> using the DTLS profile. When using this profile, a client will first try 
> to establish a DTLS session with the RS when accessing a resource. Once 
> the session is established, it will actually try to access the resource 
> over that DTLS connection. The pop key id to be used is sent when 
> establishing the DTLS connection in the DTLS handshake messages, but if 
> the RS does not have a key+token associated to that id for whatever 
> reason, then it will cancel the DTLS handshake. If the DTLS handshake is 
> never completed, then the RS can’t really send a reply at all, much less 
> a 4.01 reply.
> 
> Thanks,
> 
> Sebastian Echeverria
> 

Sebastian is right. I will change the text in the framework to allow for 
cases where no answer at all can be provided. The intent was that these 
error messages should only be sent when the access token is POSTed to 
the authz-info endpoint.

/Ludwig


-- 
Ludwig Seitz, PhD
Security Lab, RISE
Phone [phone]