Subject: RE: [dhcwg] [DHCPv6] Delayed Authentication Protocol v.s. ReconfigureKey Authentication Protocol

From: "Bernie Volz \(volz\)" <[email-masked]>
Date: Sun, 15 Oct 2006 11:06:37 -0400

Hideshi:

A malicious client might well find it far easier to simply respond to
the DHCPv6 Solicit messages from the client. In either case, it does
require the malicious client to be on-line for these earlier
transactions. So, while not full proof, it does mean that an attacker
that only briefly connects to a network can only do limited harm (since
only those clients that initiated transactions during that time are
attackable). And, given that IPv6 addresses are not likely to be as
critical a response as IPv4 ones, lifetimes (lease times) could be
significantly longer.

But, there are networks where unicast packets are *NOT* commonly seen by
all on the LAN. For example, switches don't send traffic that isn't
needed to be sent out a particular port. In those environments, the
client can't just connect anywhere -- it needs to be on the same port
which may be far more difficult and also limits the potential attacks.

The Reconfigure Key Authentication Protocol isn't foolproof and can't be
assumed to be complete secure, but it also doesn't require distributing
key information to clients and servers beforehand.

So, don't view it as a completely secure protocol; just as making the
job of attacking clients much more difficult (at least through DHCPv6
reconfigure messages).

Also, this might have bearing on
draft-ietf-dhc-dhcpv6-reconfigure-rebind-00.txt and the issue about to
whom the client responds when receiving a Reconfigure (though likely if
the malicious client is going to this trouble, it could easily
masquerade as the server although it wouldn't be guaranteed whether it
or the real server's response would be accepted by the client -- in that
case, it might take multiple reconfigures).

The point of this protocol was to make it much harder for a client to do
this -- not impossible. And, I agree that if you want more robust
security, you must use the Delayed Authentication Protocol.

- Bernie

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]] 
Sent: Friday, October 13, 2006 6:55 AM
To: [email-masked]
Subject: [dhcwg] [DHCPv6] Delayed Authentication Protocol v.s.
ReconfigureKey Authentication Protocol

Hi all,

Before, I asked some questions regarding Reconfigure Key Authentication
Protocol in RFC3315.
And I got the knowledge that Reconfigure Key Authenctication Protocol
cannot provide protection 
for malicious Reconfigure message.
#Please refer attached e-mail.

But, RFC3315 says,
----------------
21.5. Reconfigure Key Authentication Protocol

   The Reconfigure key authentication protocol provides protection
   against misconfiguration of a client caused by a Reconfigure message
   sent by a malicious DHCP server. 
(snip)
----------------
I think that this description is incorrect.
We realize that this protocol cannot provide protection for malicious
DHCPv6 Server.
And I also think that we should not encourage to use this Protocol as
Authentication Method,
because of the weakness.
It is better to use Delayed Authentication Protocol as Authentication
Method rather than 
Reconfigure Key Authenctication Protocol.

Are there any benefit that can be gained from Reconfigure Key
Authentication Protocol?

What do you think?

Thank you for your help every time.
Best regards,
*************************************
Hideshi Enokihara
IPv6 Business
Network & Software Development Dept.
Yokogawa Electric Corporation

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