Subject: [Emu] EAP-TLS EMSK exposure

From: "Nakhjiri Madjid-VXT746" <[email-masked]>
Date: Mon, 3 Aug 2009 18:50:00 -0400

Hi, 
 
I would appreciate if you could forward this question to the list.
 
I have a question regarding EAP-TLS. I am trying to understand if it is
possible for an attacker to extract the EMSK from EAP peer memory (if
not protected) and plant it inside another EAP peer and establish new
child keys for the new peer.
I guess sessionID is a measure against this, but I did not see anything
in RFC 5216 that says the EAP server checks for uniqueness of sessionIDs
across clients. It only says, if it finds the sessionID, it resumes the
session and if it does not it tries to start a new session, so I guess
if the attacker extracted both EMSK and sessionID, the attack would be
possible, no?
 
The other related question is what needs to happen before session
resumption? Is there a state between initially authenticated active
session and the resumed one? Does the EAP session go dormant? The reason
I ask, is whether the server keeps track of active sessionIDs or dormant
sessionIDs?
Can two peers use the same sessionID at the same time?
 
thanks,
Madjid