eap Mailing List: Re: Issue: Use of term lower layer

[Julien Bournelle (julien.bournelle]

Hi all,

On Thu, Dec 01, 2005 at 03:05:49PM -0800, Salowey, Joe wrote:
> Submitter name: Joe Salowey
> Submitter email address: jsalowey [at] cisco.com
> Date first submitted: 12/1/2005
> Reference: 
> Document: Keying Framework
> Comment type: E
> Priority: '1' Should fix 
> 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. 

 just a question: what do we mean here by the security association
 protocol ? the protocol used to secure the access (e.g. IKE or 4
 way-handshake) or the EAP lower-layer ?
 
 I ask the question because in PANA, we have this distinction. From the
 AAA-Key, we derived the PANA_MAC_Key which is used to protect further
 PANA signaling between the EAP client (PaC) and the EAP Authenticator
 (PAA). We also derive a key from the AAA-Key which can be used as an
 IKE psk between the EAP peer (PaC) and the Enforcement Point located in
 the AR (cf. draft-ietf-pana-ipsec-xx.txt).

 Julien

> 
> 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 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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-- 
julien.bournelle at int-evry.fr