Subject: AW: Computing rspauth (Was Re: AW: [AAA-WG]: Re: Comments on draf t-ietf-aaa-diameter-sip-app-04(pre).txt)

From: "Beck01, Wolfgang" <[email-masked]>
Date: Tue, 31 Aug 2004 17:24:02 +0200

Miguel,

You wrote:
> I agree with your statement. The idea is not for the SIP server to store 
> the user's password or H(A1). These should be stored in the Diameter server.
> 
> So what we need is: some means to transport H(A1) from the Diameter 
> server to the SIP server. I think this is missing at the moment.
Yes.

> So I propose to create a new AVP (whose name might be HA1) in the 
> SIP-Authentication-Info. This will carry HA1 from the Diameter server to 
> the SIP server, if needed. HA1 should contain the MD5 or MD5-sesssion of 
> A1, as per RFC 2617.
Ok.

> On the other hand, you mentioned the problem of replay attacks. Well, I 
> believe the interface between the Diameter client and server should be 
> secure with IPsec or TLS, as per recommendations in RFC 3588, so this is 
> not a problem in Diameter. But I can add this point to the security 
> considerations section.
You are lucky that Diameter has such recommendations (IPSec/TLS). In RADIUS,
sending H(A1) might only be secure if the algorithm is MD5-sess. There
shouldn't be interopability issues here, if RADIUS has this restrictions.

Wolfgang