I believe that the document will have implications for the RADIUS
protocol. For example, during the RADEXT WG meeting at IETF 67, we
discussed the need for crypto-agility in RADIUS, and the current lack of
ability to negotiate cryptographic algorithms. This is why Crypto-agility
was added as a RADEXT WG work item.
Since Diameter already supports cryptographic algorithm negotiation, I do
not believe that crypto-agility is an issue there.
My reading of the document is that it does not impose any security
requirements on EAP methods beyond those described in RFC 4017 and RFC
3748. At least that is what is being assumed in the EAP Key Management
Framework document, which cites RFC 4017 and RFC 3748 as meeting the
requirements.
I think that the term 'AAA key management' applies to situations which
involve use of AAA for derivation or transport of keying material. In the
case of EAP, that would include EAP methods, AAA protocols as well as the
SAP.
1. I do think that SAP designers are an audience, particularly since that
work often occurs outside of IETF.
2. The AAA protocol does play a role in freshness, because it can support
replay protection, preventing the same key transport message from being
replayed, thereby introducing stale keys.
3. I think that "authentication of all parties" is distinct from context
binding, although it is certainly a pre-requisite for it. Without
defining the parties to the key management exchange and authenticating
them, it is not possible to protect against key usage outside of the
authorized scope.
4. Agree that integrity should also be called out.
5. There are vulnerabilities associated with the 802.11i key naming
scheme. For example, I believe that PSK cracking tools have been built
that perform offline dictionary attacks on the 802.11i key names.
EAP methods satisfying RFC 4017 criteria are not vulnerable, but I do
think it illustrates the potential dangers. The problem is fixed in
802.11r.
6. I believe this section applies to binding within all phases, including
AAA, EAP and SAP. Generally AAA integrity protection mechanisms should
satisfy the binding requirements (or at least that is what is assumed in
the EAP Key Management Framework document). For EAP, the requirements are
met by RFC 4017 requirements (including Channel Binding support). So in
practice the issue has mostly arisen within SAP designs, some of which
have not properly handled key scoping and binding. For example, within
IEEE 802.11i, the authenticator is not identified, only the port/BSSID so
that the peer cannot properly determine the authenticator key scope. This
is also fixed in 802.11r.
7. I think some clarification may be needed here. As stated in the EAP
Key Management Framework document, the authenticator and AAA client are
always co-located (though these entities may both be distributed as in
some CAPWAP architectures).
-----------------------------------------------------------------
Hi Russ and Bernard,
I'm not really clear on the purpose of the document. What does it apply
to? Does it require changes to existing AAA protocols? Does it add new
requirements to EAP methods that are not in RFC3748? It would probably
be good to reference 3748 when it applies to a requirement in this
document (such as replay protection, strong fresh session keys, etc.).
What does AAA key management protocol refer to? Is it the combination
of EAP, AAA and Security Association Protocol?
A few comments on this document
1. Section 3 states "This section provides guidance to AAA protocol
designers and EAP method designers."
This should include designers of "security association protocols" as
well since many of the requirements apply to them.
2. Strong fresh session keys
In this section it is not clear what the subject session keys are. It
is not clear to me what role the AAA protocol plays in "ensure that the
keying material supplied as an input to session key derivation is fresh"
Also wouldn't key caching be relevant on the EAP server rather than the
"AAA server"?
3. Authenticate all parties
What is the AAA key management protocol? It seems that some of this
section is about validating keys are used within they correct context
and not necessarily authentication. Maybe part of this section should
belong with the context binding section.
4. Keying material confidentiality
It seems that a system should also preserve key material integrity
(perhaps this is assumed in confidentiality).
5. Unique Key Names
This section states "the key name MUST NOT be based on the keying
material itself." 802.11i uses this technique; are there vulnerabilities
associated with this?
6. Bind key to its context
In this section it is not clear what the "protocol" is or how the
binding would occur. What is meant by "The manner in which the keying
material is expected to be used."
7. Security considerations
The first paragraph is difficult to understand. It seems to be stating
that the authenticator can be separated from a AAA client as long as the
context of the request is communicated correctly between parties. Is
this it?
Joe
_______________________________________________
Ietf mailing list
Ietf(_at_)ietf(_dot_)org
https://www1.ietf.org/mailman/listinfo/ietf