Re: [Cfrg] How to circumvent the obstacles for PAKE integration into TLS // slides.

Björn, 

Its worth reading https://datatracker.ietf.org/doc/draft-sullivan-tls-opaque  which Nick presented at 104: https://datatracker.ietf.org/meeting/104/materials/slides-104-tls-slides-ietf104-tls-opaque-00. It covers both OPAQUE in the TLS handshake, and OPAQUE via Exported Authenticators https://datatracker.ietf.org/doc/draft-ietf-tls-exported-authenticator/ at some point after TLS handshake has taken place. Its currently OPAQUE specific, but the EA model could probably be applied to other PAKEs. And finally, https://datatracker.ietf.org/doc/draft-ietf-httpbis-http2-secondary-certs/ covers how to use EA with HTTP2.

Owen

-----Original Message-----
From: Cfrg <cfrg-bounces@irtf.org> On Behalf Of Björn Haase
Sent: 23 July 2019 08:43
To: Benjamin Kaduk <kaduk@mit.edu>; Watson Ladd <watsonbladd@gmail.com>
Cc: CFRG <cfrg@irtf.org>; hugokraw@gmail.com
Subject: Re: [Cfrg] How to circumvent the obstacles for PAKE integration into TLS // slides.

Dear Ben,

>To build on that, a big motivation for wanting auth at the HTTP layer 
>is that most generic web servers aren't going to know *at TLS handshake 
>time* whether a given client is going to need to authenticate for the 
>HTTP requests that will subsequently be conveyed over that connection.

I fully agree. When saying this, I think that we might better be careful not to mix-up two aspects:

1) The human at the client side mostly wants to be sure that the server side contents are authentic, from the very beginning.
2) The server side requires authentication often only when operations with privileges are requested.

What we have here is something similar to what I'd be calling "re-authentication use-case" for password checks in a connection that is already established.

Moreover I see differences regarding the use-cases A  "End-customer-managed web servers (IoT)" and  B "Conventional Web-Shop use-cases (Web-PKI)". The main additional benefit of PAKE for use-case A is that the server-authentication (1.) above) is provided also without the need of Web-PKI integration of the server.

I think that one might best try to realize the maximum possible re-use for authentication mechanisms in both use-cases A/B. Again this might be a reason for "outsourcing" all of the user-handling related stuff outside of the main TLS body. Also for use case "B" it might be worth to consider pulling out the password handling out from the main html application. Maybe one could use the same mechanisms of a "user authentication" module that we would be using for PAKE? For doing so again some kind of channel-linked tunnel mechanism through TLS might be helpful/necessary.

Yours,

Björn.

P.S.: I have moved this discussion back to the main list. Sorry for starting this discussion with the "not yet publication-ready" slides.

Mit freundlichen Grüßen I Best Regards 

Dr. Björn Haase 

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