Subject: Re: [eap] DISCUSS: draft-ietf-eap-netsel-problem

From: "Bernard Aboba" <[email-masked]>
Date: Fri, 02 Nov 2007 06:03:50 -0800

Thanks.

One question is the security of the EAP method.  If the RFC 4017 mandatory 
criteria are met, then even if there is not a pre-configured profile, an 
attacker with a rogue authenticator should not be able to obtain long-term 
credentials.

Another question is how the peer verifies that the EAP server is authorized 
to serve the selected realm.  For example, if the identity 
"[email-masked]" is chosen, should the peer require that the Server-Id 
match "example.com" in some way?  Does this imply that the layer 2 
advertisement mechanism should provide the realm?

In WiFi this has arisen in the context of Emergency Services where it may be 
desirable to verify that a given network is "legitimate" in some sense 
before placing an Emergency Services call with it.  Unfortunately, the SSID 
is not globally unique so that without a pre-configured profile, it is not 
possible to determine whether a given Server-Id is authorized to serve a 
particular SSID.  However, one may be able to match the Server-Id against 
the realm advertised as described in RFC 4284.

In WiMAX this issue has issue has arisen because IEEE 802.16e only 
identified layer 2 networks by their NSP ID, not their realm.  If the peer 
does not have a pre-configured profile (as they won't if they have just 
purchased a device at retail, but not signed up for a provider yet), then 
this creates a few problems:

a. The NSP ID is a number that is meaningless to an ordinary user.
b. NSP IDs are allocated by the IEEE 802 RAC, which only cares about 
ensuring against duplication, *not* about determining whether the numbers 
are being requested to legitimate spectrum owners.
c.  As a result, there is no existing process to verify legitimate ownership 
of an NSP ID or correspondence between an NSP ID and a Server-Id.

One potential solution has been to advertise a realm instead (a la RFC 
4284).  This enables the advertised realm to be matched against the 
Server-Id.

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