Subject: [Sip] Issue #232: TLS v. IPSec

From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 6 Dec 2001 16:41:45 -0500

Issue:

Bis-05 currently specifies TLS as the preferred transport layer security
solution for SIP. THis has raised concerns. Mostly, these concerns are
around the fact that TLS implies TCP, and user to proxy transport security
with TCP is going to be problematic.

Discussion points:

I think its sensible to separate the transport security into user to proxy
and proxy to proxy security. For proxy to proxy, TLS appears much better.
The setup overheads are not an issue, it has congestion control, and it
provides authentication identification information to the proxy for policy
decisions. It also has a workable keying solution, whereas IPSec does not at
this time. 

Not that IPSec is never a good thing; for securing the connections between
boxes in the network of a single provider, IPSec is very reasonable. TLS
could also be used there, of course.

Proposal:

TLS MUST be supported on all proxies for proxy-proxy security
IPSec MAY be supported
User to proxy security is a separate issue

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
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[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
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---

From: Michael Thomas <[email-masked]>
Date: Thu, 6 Dec 2001 14:18:03 -0800 (PST)

> and proxy to proxy security. For proxy to proxy, TLS appears much better.

   Better in what way? Also: I don't find your
   spilt sensible at all. It leaves the most
   vulnerable and problematic pieces without
   a defined solution (UA's). 

 > The setup overheads are not an issue, it has congestion control, 

   You can run TCP/SCTP over IPsec too.

 > and it
 > decisions. 

   This is an API issue, not a protocol issue.

 > It also has a workable keying solution, whereas IPSec does not at
 > this time. 

   _What_??? What is IKE? What is KINK? What is XAUTH
   for AAA hackery? Also: anybody who believes that
   TLS inherits a workable PKI is la-la land. The web
   does not use PKI for security purposes even
   though there's a lot of hype and useless CPU cycles.

 > could also be used there, of course.

   All of the cross realm issues present in IPsec
   are present for TLS. This shouldn't be any deep
   surprise: one is a L3.5 wedge, the other is a
   L4.5 wedge, and they both rely on the same auth
   techologies.

		Mike

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From: "Jari Arkko" <[email-masked]>
Date: Fri, 7 Dec 2001 00:20:39 +0200

> and proxy to proxy security. 

We are very much in agreement here.

> and proxy to proxy security. For proxy to proxy, TLS appears much better.

But here I disagree. There's a few problems in TLS as well. The main
one from my point of view relates to very large networks (guess which
ones?) where scalability proxy-to-proxy might be an issue.Here, IPsec
tunnel mode and separate gateways could help a lot -- if you have an SA
pair between all operators that is much better than an SA pair between
each box of each operator (e.g. 1000 operators => 1M SAs; 50 proxy
farm on each operator site => 2.5 G SAs). There are also other issues,
such as the fact that an IPsec tunnel could also be used simultaneously
for lots of other signaling protection needs while the TLS is only useful
for one thing. SCTP. The ability to use just IPsec (no key management
at all, very simple). Etc.

Question: does TLS support preshared symmetric keys (which IPsec does,
easing deployment as you don't need to deploy certs and possibly PKIs)?

Also, I believe Mike Thomas posted some long list of pros and cons
for the TLS-IPsec in SIP a while back. Perhaps we could get back to
that list?

In conclusion, I would propose MUST use IPsec for proxy-to-proxy, but
allow for separate gateways as well as transport mode in the box. MAY
use TLS.

> It also has a workable keying solution, whereas IPSec does not at

I think this is an overly broad claim. They are working on an a new IKE
version, but that doesn't mean the old one is broken. The old version
is also widely deployed and products are easily available.

I wouldn't use this as an argument in the TLS-IKE discussion.

> User to proxy security is a separate issue

We are again in agreement. Btw, please take a look at the draft-garcia and the
section on access domain security... basically people feel that neither TLS
nor IPSec/IKE are a solution in the wireless case. Could be LANs and WLANs,
though.

Jari