[HOKEY] FW: [eap] Re-review of draft-ietf-hokey-erx-13.txt
"Glen Zorn" <gzorn@arubanetworks.com> Wed, 12 March 2008 20:32 UTC
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Thread-Topic: [eap] Re-review of draft-ietf-hokey-erx-13.txt
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From: Glen Zorn <gzorn@arubanetworks.com>
To: hokey@ietf.org
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Subject: [HOKEY] FW: [eap] Re-review of draft-ietf-hokey-erx-13.txt
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Bernard_Aboba@hotmail.com <mailto:Bernard_Aboba@hotmail.com> scribbled on Wednesday, March 12, 2008 10:47 AM: > Re-Review of draft-ietf-hokey-erx-13.txt > > I went through the draft again. Note that these comments only > reflect my own review; the author still needs to follow up > with other reviewers. > > Here are some overall comments: > > 1. I think you need to deal with the potential fraud issues > in the document. This would involve describing the > precautions that a AAA server should take in authorizing > domains to receive DSRKs, and validating subsequent accounting > records. > > 2. I think you need to specify the applicability of this > specification. I'm still somewhat uncertain about whether we're > talking about intra-media, inter-media, inter-domain (with some > meaning of > domain), etc. Please clear this up. > > Some details: > > Note that this may introduce some delay in starting EAP. In some > lower layers, the delay can be minimized or even avoided by the peer > initiating EAP by sending messages such as EAPoL-Start in the IEEE > 802.1X specification [10]. > > [BA] Since ERX is not compatible with IEEE 802.1X (whose state > machine doesn't support peer-initiated messages) I don't see > how this is possible. It might be better to omit the reference. > > When the EAP-Request/Identity times out, the authenticator > MUST NOT close connection if an ERP exchange is in progress or has > already succeeded in establishing a reauthentication MSK. > > [BA] What does "close connection" mean? Is the document > making normative statements about link layers specified > outside the IETF? > > The authenticator uses the realm in the keyName-NAI [4] > field to send > the message to the appropriate ER server. > > [BA] Do you really mean that the authenticator is using the > realm to determine the IP address of the ER server? Or is the > keyname-NAI field just copied into the User-Name attribute so > that routing happens normally? > > The local ER server SHALL request > the home AAA server for the DSRK by sending the domain name in the > AAA message that carries the EAP-Initiate/Reauth bootstrap message. > The local ER server MUST be in the path from the peer to the home ER > server. If it is not, it cannot request the DSRK. > > [BA] Since the local ER server does not determine whether it > is on the path how is "path pinning" to be achieved? How does > the AAA server know whether an ER server is on the path or not? > What does it do if it is not on the path? In other words, > what does the MUST imply? > > Also, how is the mapping from domain name to IP address to be > achieved? Is this via an A/AAAA RR? A SRV RR lookup? > > Section 4.3 > > In case of ERP with the > home ER server, the peer uses the realm from its original NAI; in > case of a local ER server, the peer uses the domain name received at > the lower layer or through a ERP bootstrapping exchange. > > [BA] Which "original NAI" are we talking about? The NAI used > in the EAP-Response/Identity in the original EAP conversation? > The NAI in the Peer-Id? The NAI in the ERX conversation? > > Section 5.1 > > o In addition, the rMSK is sent along with the EAP-Finish/Re-auth > message, in a AAA attribute [12]. > > [BA] Transport of the MSK is already specified in existing AAA > documents, such as RFC 4072 (Diameter EAP). Why is reference > 12 being given here rather than those existing documents? > This document does not update those specifications. > > Section 8 > > Authenticate all parties > > The EAP Re-auth protocol provides mutual authentication of the > peer and the server. Both parties need to possess the keying > material that resulted from a previous EAP exchange > in order to > successfully derive the required keys. Also, both the EAP re- > authentication Response and the EAP re-authentication > Information messages are integrity protected so that the peer > and the server can verify each other. When the ERP > exchange is > executed with a local ER server, the peer and the local server > mutually authenticate each other via that exchange in the same > manner. The peer and the authenticator authenticate > each other > in the secure association protocol executed by the lower layer > just as in the case of a regular EAP exchange. > > [BA] I think you mean "ERX" not "EAP re-authentication" or ERP, right? > One thing that is left out here is authentication between the > ERX local server and the ERX home server. This exists if they > are one hop apart, but otherwise not. So I think there is an > assumption that the ERX server is only willing to provide keys > to domains that it is explicitly authorized to deal with. > > It is RECOMMENDED that the AAA protocol be protected using > IPsec or TLS so that the keys are protected in transit. Note > however that keys may be exposed to AAA proxies along the way > and compromise of any of those proxies may result in > compromise of keys being transported through them. > > [BA] I think you just want to say "It is RECOMMENDED that the > AAA protocol protect the keys in transit. This can be > accomplished via transmission layer security (IPsec or TLS), > or via an application-layer mechanism." > > Confidentiality of identity > > Deployments where privacy is a concern may find the use of > rIKname-NAI to route ERP messages serves their privacy > requirements. Note that it is plausible to associate multiple > runs of ERP messages since the rIKname is not changed as part > of the ERP protocol. There was no consensus for that > requirement at the time of development of this specification. > If the rIKname is not used and the Peer-ID is used > instead, the > ERP exchange will reveal the Peer-ID over the wire. > > [BA] The rest of the spec does not talk about use of the > Peer-Id. Since not all EAP method deriving keys have a > Peer-Id, do you really want this mentioned here? > > To prevent such DoS attacks, an ERP failure should not result in > deletion of any authorization state established by a full EAP > exchange. > > [BA] Is this purely up to this specification to determine? > Typically the lower layer defines the authorization state and > how it is installed/removed. > This may not necessarily involve EAP (e.g. 802.11 4-way handshake).
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