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RE: EAP applicability (Was: Re: IETF Last Call on Walled Garden Standard for the Internet)

2008-03-13 21:41:43
See inline....

-----Original Message-----
From: Jari Arkko [mailto:jari(_dot_)arkko(_at_)piuha(_dot_)net]
Sent: Thursday, March 13, 2008 11:50 PM
To: Avi Lior
Cc: Bernard Aboba; ietf(_at_)ietf(_dot_)org
Subject: EAP applicability (Was: Re: IETF Last Call on Walled
Garden Standard for the Internet)

Avi,

For what it is worth, this ex-EAP co-chair also thinks
that the use
of EAP keys for applications is a very bad idea.


Why?


For a number of reasons. Take this from someone who has
actually tried to do this in the distant past and has
realized that it was a bad idea.

But first let me clarify that I'm not criticizing HOKEY for
EAP keys in any way; HOKEY is a fine application for EAP
keys. The document that started this thread can be fixed by
better IANA and applicability sections. I've also changed the
subject to reflect the new topic.

Back to the reasons for why application keying based on EAP
is a bad idea. First, there is an applicability statement in
RFC 3748 which discourages the use of EAP for other
applications than network access.
We've generally treated this liberally and included things
like VPN access (IKEv2) and mobility services in this as well.

Okay.  So some applications are okay.  I agree we need to provide guidelines as 
to the shortcomings.  Let SDOs then decide what is and what is not appropriate 
for them to do.

The point is that the term 'applications' is rather broad.  There are many 
types of applications. I may agree that using EMSK to protect all applications 
may be a problem.  But in certain situations it could solve problems as well.

Use of EAP keys in other contexts than the network access
itself presents a number of problems. The primary problem is
that while EAP runs on many, many interfaces and products,
the number of networks where is still relatively small, or at
least its nowhere near ubiquitous. This presents a problem
for applications that require EAP-based keys. This hotel
network supports web logins, not EAP so does that mean I
would be unable to use the EAP-based applications? And from
the point of view of an application provider, why would I
want to exclude the 99.9% of current Internet users that are
not behind an EAP-based network interface?

The conclusion from this is that application keying should be
arranged independently of network access. Note that in some
cases you can use the same credentials to access a particular
application, even if you are not reusing keys from the
network access phase. For instance, IKEv2 and its EAP
capability has been used in some mobility designs. But this
is an independent run of EAP, nothing to do with the network
access EAP run (if there even was one).

Finally, many of the things that you want to do are
impossible if you tie your applications to network access
keys. For instance, if you are mobile you would ideally want
to move from one access network to another. What if one of
these access networks does not support EAP for network
access. E.g., Wimax -> 3G? What would this do to your ability
to use an application?

Jari


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