Subject: PANA security requirements

From: George Tsirtsis <[email-masked]>
Date: Thu, 28 Feb 2002 19:38:21 -0500

All,

I have been trying to understand the security requirements for PANA and have
been talking to a couple of security people in my company. Here is where I
am at the moment.

The requirements draft says that we should be able to guard against "blind
masquerading" attacks and the protection should be similar to that of TCP
SYN attacks.
From the draft:
"  PANA MUST be robust against a class of DoS attacks such as blind
masquerade     
   attacks through IP spoofing that swamp the PAA in 
   spending much resources and prevent legitimate clients' attempts of 
   network access. The required robustness is no worse than that for 
   TCP SYN attack. "

I fail to understand what the requirement is. One can not really prevent TCP
SYN attacks...unless it runs over a secure channel e.g.: you only accept
IPSECed packets. This is not acceptable in PANA i.e.: we can not assume a
secured channel because PANA's purpose is to authenticate a user and
potentially generate session keys.

Furthermore, employing a cookie (as has been suggested) to protect against
DoS attacks may be a false promise. The process of generating and agreeing
cookies may themselves provide opportunity for DoS attacks. i.e.: an
attacker can send a large number of cookie establishment requests. So, a
cookie only makes sense if the process that you try to protect is
*significantly* more computational and expensive! This is why ISAKMP is
using cookies as far as I can tell.

I do not understand why PANA needs anything similar. In particular, if EAP
is used, as a number of proposals suggest, I think cookies at the PANA layer
are useless. This is because the need for a cookie is dictated by the
complexity of the EAP method that it is chosen, as I indicate above. If the
chosen method needs cookies or any other protection, then the method itself
is likely to employ them. e.g.: if you run TLS over EAP over PANA, what
would you need to protect at PANA layer on top of what TLS is designed to
protect?

Please let me know if I am totally off the mark here...I am still working on
this but I thought to let you know of my current thoughts in case I have
misunderstood something.

Regards
George