Subject: RE: [mobile-ip] confusion about prefix sol/adv

From: "Hesham Soliman (ERA)" <[email-masked]>
Date: Thu, 20 Jun 2002 14:53:25 +0200

=> One attack mentioned by Jari in earlier discussions
was to deprecate a lifetime of a prefix, or swap lifetimes....etc
This is effectively a DoS attack. The difference I see between
this and other DoS attacks is that an attacker can deny any 
communication with any CN (by making the MN choose the 
wrong address) while not located on the path between
the CN and the MN. 

But I still think we're jumping too far. I doubt that
security will be an issue if we send these messages
_after_ the BU is sent to the HA...
It's pretty easy to secure the message after that.
I'll reply to TJ's email shortly. 

Hesham

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From: Jari Arkko <[email-masked]>
Date: Thu, 20 Jun 2002 21:10:45 +0300

> wrong address) while not located on the path between

Some further notes.

An attacker can't force the MN to go all the way in
picking a wrong address. The HA would refuse to accept
such an address. What they can do, however, is to reduce
the number of (valid) addresses on the prefix list, or
make the lifetimes smaller. By replacing a valid prefix
with an invalid one, you can get the MN give up a valid
address and try to get a a bad address accepted -- this will
lead to the MN having no valid home addresses to
communicate with.

However, as TJ pointed out the current spec requires IPsec
on all MPS messages, except the first one. On the first
one these attacks are still possible, but the attacker would
have to pick the right to for the attack, i.e. between the

MN coming up and successfully performing the MPA-MPS procedure.

Interestingly, section 11.3.4. requires the IPsec SA to
provide replay protection, which it generally speaking can't
do without automatic key management. (Assuming key management
exists, we could perhaps require all ICMPv6 traffic to be
secured. That would solve the problem even with the first
MPS & MPA. The question is, what is mandatory to implement?)

Jari

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From: Vijay Devarapalli <[email-masked]>
Date: Thu, 20 Jun 2002 11:19:50 -0700

Jari Arkko wrote:

> secured. 

I am not sure if we should do it this way. I agree with Raj.
lets go with your cookies approach. and when the MN gets an 
unsolicited MPA, instead of using the information, sends an
MPS.

Vijay

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From: Jari Arkko <[email-masked]>
Date: Thu, 20 Jun 2002 21:39:32 +0300

> unsolicited MPA, instead of using the information, sends an

How about the above + note in the spec that you MAY implement
automatic key management to secure the whole thing if you want
to?

Jari

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From: Vijay Devarapalli <[email-masked]>
Date: Thu, 20 Jun 2002 12:27:02 -0700

> automatic key management to secure the whole thing if you want

it is tough to do this. this also has a side-effect of having to 
secure all ICMPv6 traffic between the MN and the HA. on top of 
that you say 'MAY'. so, who is going to implement it?

but, go ahead if you feel it is necessary.

Vijay