Subject: [eap] Proposed Resolution of Issue 320: Use of term Lower Layer

From: "Bernard Aboba" <[email-masked]>
Date: Sun, 22 Jan 2006 21:40:46 -0800

The text of Issue 320 is enclosed below.  The proposed resolution is to 
accept the changes, with modifications to one of the suggestions as follows:

Change

"The exception to the "no sharing" rule is the AAA layer.  On EAP
server, keying material requested by and passed down to the AAA layer
may be replicated to the AAA layer on the authenticator.   On the
authenticator, the AAA layer may provide the replicated keying
material to the lower layer over which the EAP authentication
conversation took place.  This enables "mode independence" to be
maintained. "

To

"On the EAP server, keying material requested by and passed down to the AAA 
layer
may be replicated to the AAA layer on the authenticator.   On the
authenticator, the AAA layer may provide the replicated keying
material to the lower layer over which the EAP authentication
conversation took place.  This enables "mode independence" to be maintained.
However, the EMSK MUST NOT be transported by the AAA layer."

---------------------------------------------------------------------------------------------------------------------
Issue 320: Use of term lower layer
Submitter name: Joe Salowey
Submitter email address: [email-masked]
Date Submitted: December 1, 2005
Reference:
Document: Keying-08
Comment type: E
Priority: 1
Section: 2
Rationale/Explanation of issue:
The term lower layer is used inconsistently in the document.

Lower layer should refer to the protocol between the EAP Peer and the
EAP Authenticator.  It is between these entities that the security
association protocol is typically run.  The MSK is transported to the
lower layer.

AAA is not an EAP lower layer except in the special case where the AAA
client and server are acting as the EAP Peer and EAP Authenticator for
some reason (an example of this could was in EUSM).  Entities other than
the lower layer may obtain keys derived from the EMSK.

Requested change:

Section 2.1
-----------
change

"Of these phases, Phase 0, 1b and Phase 2 are handled by a lower layer."

To

"Of these phases, Phase 0, 1b and Phase 2 are handled external to EAP.
Phases 0 and 2 are handled by the lower layer protocol and phase 1b is
typically handled by a AAA protocol."

Section 2.2
------------
(remove references to IV)
---
Change

"The EMSK MUST NOT be provided to the lower layer, nor is it permitted
to pass any quantity to the lower layer from which the EMSK could be
computed without breaking some cryptographic assumption, such as
inverting a one-way function."

To

"The EMSK MUST NOT be provided to an entity outside the EAP server or
peer,  nor is it permitted to pass any quantity to an entity outside the EAP
server or peer from which the EMSK could be computed without breaking some 
cryptographic assumption, such as
inverting a one-way function."
---
Change

"In order to preserve the security of keys derived within EAP methods,
lower layers other than AAA MUST NOT export keys passed down by EAP
methods. "

To

"In order to preserve the security of keys derived within EAP methods,
 lower layers MUST NOT export keys passed down by EAP
 methods."
---
Change

"EAP keying material and parameters provided to a lower layer other
than AAA MUST NOT be transported to another entity."

To

"EAP keying material and parameters provided to a lower layer MUST NOT
be transported to another entity."
---
Change

"The exception to the "no sharing" rule is the AAA layer.  On EAP
server, keying material requested by and passed down to the AAA layer
may be replicated to the AAA layer on the authenticator.   On the
authenticator, the AAA layer may provide the replicated keying
material to the lower layer over which the EAP authentication
conversation took place.  This enables "mode independence" to be
maintained. "

To

"The AAA layer may transport keys that are exported from the EAP server.
On the EAP server, keying material requested by and passed down to the AAA 
layer
may be replicated to the AAA layer on the authenticator.   On the
authenticator, the AAA layer may provide the replicated keying
material to the lower layer over which the EAP authentication
conversation took place.  This enables "mode independence" to be 
maintained."

-----------
Section 2.3
-----------

Change
"The caching behavior of existing EAP lower layers is as follows:"

To

"The caching behavior of existing EAP lower layers and AAA layers is as
follows:"

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---

From: "Bernard Aboba" <[email-masked]>
Date: Mon, 23 Jan 2006 07:20:48 -0800

Additional changes required to resolve this issue:

Change:

"Existing EAP lower layers handle the caching of EAP keying
material and the generation of transient session keys in
different ways:"

To:

"Existing EAP lower layers and AAA layers handle the caching of EAP keying
material and the generation of transient session keys in
different ways:"

Change "Lower Layer" to "Lower Layer or AAA" in Figure 3.

>maintained.

---

From: "Bernard Aboba" <[email-masked]>
Date: Mon, 23 Jan 2006 07:31:44 -0800

One more:

Change the first two paragraphs of Section 2.2 to:

"As illustrated in Figure 3, on completion of EAP authentication, EAP 
methods
export the Master Session Key (MSK), Extended
Master Session Key (EMSK), Peer-ID,
Server-ID, Session-ID and Key-Lifetime to the EAP peer or authenticator 
layers.  The
Initialization Vector (IV) is
deprecated.

The EAP peer and authenticator layers MUST NOT modify or cache
keying material or parameters (including Channel Bindings)
passing in either direction between
the EAP method layer and the EAP layer.
The EAP layer also MUST NOT cache keying material or parameters
(including Channel Bindings) passed to it, whether by the EAP 
peer/authenticator
layer, the lower layer or the AAA layer."

>>"On the EAP server, keying material requested by and passed down to the 
>>AAA layer