Subject: [Sip] Reviewers for the sec-agree draft

From: Gonzalo Camarillo <[email-masked]>
Date: Tue, 21 May 2002 13:02:06 +0300

Hello folks,

we need SIP people willing to have a look at the new version (01) of the
sec-agree draft (released one week and a half ago).

http://standards.ericsson.net/gonzalo/papers/draft-ietf-sip-sec-agree-01.txt

As you proabbly know, the previous version (00) had some problems that
were discovered during the iterim meeting in Vegas. The discovery of
problems (such as a broken SIP syntax) at that point of time (after the
WGLC had finished) indicates that nobody in the SIP WG bothered to read
the document.

I am not saying that this draft is so interesting that everyone will
enjoy reading it, but we would need at least a couple of reviewers that
are familiar with SIP and have the energy to review the document. We
cannot let the SIP WG send documents to the IESG that have major flaws!

Here you have a brief summary of the changes we introduced to the new
version of the draft (01):

The syntax has been fixed. Now it is allowed to have different security
mechanisms listed (separated by commas or in different lines). The
previous draft used commas to separate security mechanism tokens. That
made the header field non-SIP compliant.

The scope has been narrowed down. Before, the draft tried to solve every
security negotiation problem that could be found in a SIP network. Now
the draft only tries to resolve the security negotiation between a host
and its next SIP hop (e.g., UA and the outbound proxy).

The negotiation works as follows. The UA sends a SIP message (typically
OPTIONS) to its outbound proxy listing its security capabilities (e.g.,
TLS and IPSec). The outbound proxy sends a response with its own
capabilities (it is important that the list in the server is static).
With this information, client and server initiate the security mechanims
(e.g., initiate a TLS conection).

When the client sends another SIP message to the outbound proxy, this
time using the TLS connection, it includes a header field that contains
the list obtained previously from the server. This way, the server can
check whether a MitM changes the list in order to perform a bid-down
attack.

Of course, this security negotiation mechanism requires that all the
security mechanisms advertised provide integrity protection, at least.

Thank you,

Gonzalo
-- 
Gonzalo Camarillo         Phone :  +358  9 299 33 71
Oy L M Ericsson Ab        Mobile:  +358 40 702 35 35
Telecom R&D               Fax   :  +358  9 299 30 52
FIN-02420 Jorvas          Email :  [email-masked]
Finland                   http://www.hut.fi/~gonzalo

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: "James Undery" <[email-masked]>
Date: Tue, 21 May 2002 15:01:11 +0100

Hi,

I'll have to admit myself of being guilty of not reading drafts
recently. But I'd note digest-integrity needs to be dropped as it
protects the body of messages only. If it can't be dropped a lpidf like
extension would be required 
(http://www.jdrosen.net/papers/draft-rosenberg-impp-lpidf-00.txt) to
place your headers in the body.

James

> -----Original Message-----
> From: Gonzalo Camarillo [mailto:[email-masked]]
> Sent: 21 May 2002 11:02
> To: sip
> Cc: Allison Mankin; Jari Arkko (LMF); Vesa Torvinen (LMF)
> Subject: [Sip] Reviewers for the sec-agree draft
> 
> 
> Hello folks,
>

---

From: "Sanjoy Sen"<[email-masked]>
Date: Tue, 21 May 2002 09:21:26 -0500

James,

The use of 'sipfrag' (draft-sparks-sip-mimetypes-03 or whatever is the
latest version) is assumed. But, I agree that it should be explicitly stated
for clarity.

Sanjoy

> From: James Undery [mailto:[email-masked]]
> Sent: Tuesday, May 21, 2002 9:01 AM
> To: Gonzalo Camarillo; sip
> Cc: Jari Arkko (LMF); Vesa Torvinen (LMF)
> Subject: RE: [Sip] Reviewers for the sec-agree draft
> 
> 
> Hi,
>

---

From: "Vesa Torvinen (LMF)" <[email-masked]>
Date: Tue, 21 May 2002 16:25:57 +0200

Text in section 3.5 is supposed to address this issue: 

"If digest-integrity is chosen, the 494 (Security Agreement Required)
response will contain an HTTP authentication challenge. The client
MUST use the qos parameter possibly together with some variant of
MIME tunneling so that the Security-Verify header field in the
request is integrity protected in the MIME body. Note that digest
alone would not fulfill the minimum security requirements of this
specification."

We didn't want to specify how to use 'digest-integrity' exactly 
because this draft is related to negotiation - not individual 
mechanisms. Neither did we want to drop the mechanism from the 
list because someone can implement it using existing standards 
(e.g. MIME, B2BUA, etc). 

Vesa 

-----Original Message-----
From: James Undery [mailto:[email-masked]]
Sent: 21. toukokuuta 2002 17:01
To: Gonzalo Camarillo; sip
Cc: Jari Arkko (LMF); Vesa Torvinen (LMF)
Subject: RE: [Sip] Reviewers for the sec-agree draft

Hi,

James

---

From: "James Undery" <[email-masked]>
Date: Tue, 21 May 2002 15:41:22 +0100

> From: Vesa Torvinen (LMF) [mailto:[email-masked]]
> Sent: 21 May 2002 15:26
> To: James Undery
> Cc: Jari Arkko (LMF); Gonzalo Camarillo Gonzalez (LMF); sip

The word possibly above worries me, it'd also be nice to make the
mechanism explicit e.g. 'sipfrags' as Sanjoy suggested.

> list because someone can implement it using existing standards 

I think a small amount of usage is required e.g. S/MIME protection MUST
include any Security-* headers present. (This is mainly implicit at the
moment.)

James