Subject: [Ieprep] Security Requirements for SIPPING SEC-11 to SEC-14

From: "King, Kimberly S." <[email-masked]>
Date: Tue, 15 Oct 2002 08:17:11 -0400

"SEC-11: Anonymity: For the reasons noted earlier, users have to
             authenticate themselves towards the network carrying the
             request. The authentication may be based on capabilities
             and noms, not necessarily their civil name. Clearly, they
             may remain anonymous towards the request destination, using the
network-asserted identity and general privacy mechanisms"

Does this type of anonymity require an explicit relationship on the part of
the IP/SIP network and the user?

Do all users require anonymity?  

Suppose we are in the SIP to CSN topology, I assume the request destination
is the SIP gateway (i.e., the destination is seen from the perspective of
the SIP network).  Does this requirement "may remain anonymous towards the
request destination" preclude the gateways ability to authenticate the user?

       " SEC-12: Denial-of-service: ETS systems are likely to be subject
             to deliberate denial-of-service attacks during certain
             types of emergencies. DOS attacks may be launched on the
             network itself as well as its authentication and
             authorization mechanism."

As stated, it appears the requirement is that DOS attacks may be launched.
Since I really doubt that is the desired requirement, what is it that you
are requesting?

        "SEC-13: Minimize resource use by unauthorized users: Systems
             should minimize the amount of state, computation and
             network resources that an unauthorized user can command."

I hate to broach the subject, but this sounds like a policy statement.

        "SEC-14: Avoid amplification: The system must not amplify attacks
             by causing the transmission of more than one packet to a
             network address whose reachability has not been verified."

Is this standard procedure?  If so, why have the requirement?  If not, it
seems like it would delay call setup and require changes for default
behavior (since by SEC-4, ETS users may use phones that are not their own).

Also, do you mean "one packet" or one SIP message?
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From: Ian Brown <[email-masked]>
Date: Tue, 15 Oct 2002 13:32:25 +0100

> Do all users require anonymity?

No.

> request destination" preclude the gateways ability to

No -- remember that we (and the gateway in this scenario) are interested in
the authorisation of a user to make an ETS call, not necessarily in
authenticating their *identity*.

> I hate to broach the subject, but this sounds like a policy statement.

I think it's also an important technical requirement that reduces the impact
of DoS attacks.

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From: Henning Schulzrinne <[email-masked]>
Date: Tue, 15 Oct 2002 11:49:56 -0400

> Also, do you mean "one packet" or one SIP message?

Roughly the same thing, unless you have (UDP) fragmentation. I added 'or 
SIP request'.