Subject: RE: [Sip] Last Call: DHCPv6 Options for SIP Servers to Proposed Standard

From: "Christian Huitema" <[email-masked]>
Date: Tue, 28 May 2002 13:41:18 -0700

> Christian wrote:
> > I have a major issue with this spec, namely that the security
> > problems are not addressed. The security section correctly
> > lists one of the main security threats, the spoofing of a DHCP
server:
> 
> Yes, this is a real issue.
> 
> But isn't this sort of a general DHCP problem rather than one specific
> to the usage of SIP?
> 
> Do we need to bascially stop using DHCP while working on it, and if so
> is this (SIP working group) the right forum to try and tackle that?

Well, there is a middle ground, which is to only use DHCP when the
risk/benefit ratio is right. My contention is that, in the case of SIP,
the risk/benefit ratio is weighted a lot towards risk, and that in
general there are other solutions. For example, we know that the UA must
have some explicit configuration -- reference URL, security credentials,
etc. In these cases, using DHCP for SIP is not needed.

-- Christian Huitema

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---

From: Henning Schulzrinne <[email-masked]>
Date: Tue, 28 May 2002 17:17:44 -0400

> etc. In these cases, using DHCP for SIP is not needed.

I don't think that is true. In a visited network, the outbound proxy may 
be needed to communicate, as I mentioned in my previous email.

Plus, I don't see that the SIP case is so special. If I spoof a DHCP 
server (absent of a shared secret), I can hand out bogus IP addresses 
that conveniently end up sending all packets to the default router for 
that address (another compromised server). Why bother with just received 
S/MIME encrypted SIP requests if I can get the whole hog?

I don't know which of the DHCP IPv4 options will find its way into v6, 
but the POP server option, the NNTP server option and NIS+ options seem 
to be at least as juicy a target.

I'm all for a stronger applicability statement, but this would seem to 
apply to DHCPv6 in general. Basically, it would have to say "DHCPv6 is 
not currently suited for roaming users that don't have a pre-established 
secret with the visited domain".

Henning