H.235 Security Blues

Euchner Martin Martin.Euchner at ICN.SIEMENS.DE
Tue Jul 24 12:38:37 EDT 2001


Manoj and experts,

thanks for pointing out several points in H.235v2 that do deserve clarification.
My answers are included below in the original text.

I've also attached draft text for the H.323 Implementors Guide, that proposes clarifications and corrections. If you agree, I would send the text "officially" to our H.323 IG editor.



With kind regards

Martin Euchner.
-----------------------------------------------------------------------
| Dipl.-Inf.                     Phone: +49 89 722 55790
| Martin Euchner                 Fax  : +49 89 722 46841
| Siemens AG
| ICN M SR 3                     mailto:Martin.Euchner at icn.siemens.de
|                                mailto:martin.euchner at ties.itu.int
| Hofmannstr. 51                 Intranet: http://intranet.icn.siemens.de/marketing/cs27/
| D-81359 Muenchen               Internet: http://www.siemens.de
| __________________
| Germany
-----------------------------------------------------------------------

Kind Regards

Martin Euchner.
-----------------------------------------------------------------------
| Dipl.-Inf.                     Phone: +49 89 722 55790
| Martin Euchner                 Fax  : +49 89 722 46841
| Siemens AG
| ICN M SR 3                     mailto:Martin.Euchner at icn.siemens.de
|                                mailto:martin.euchner at ties.itu.int
| Hofmannstr. 51                 Intranet: http://intranet.icn.siemens.de/marketing/cs27/
| D-81359 Muenchen               Internet: http://www.siemens.de
| __________________
| Germany
-----------------------------------------------------------------------



 -----Original Message-----
From:   Paul, Manoj [mailto:mpaul at TRILLIUM.COM]
Sent:   Thursday, July 19, 2001 9:15 PM
To:     ITU-SG16 at mailbag.cps.INTEL.COM
Subject:        H.235 Security Blues

Experts,

  Could someone clarify following aspects of H.235 V2 Annex D (Baseline Security Profile).
1) Section D.2, last but second paragraph (This profile defines to....). According
to this paragraph, the generalId field shall be set to the "called endpoint ID" for
H225 signalling messages. Since the calls must be GK routed, shouldn't the generalId
refer to the gkId for 225 messages sent by endpoints?

Yes, correct. The GeneralID should always be the destination ID. Please see, the section in the Implementors Guide which corrects this.

Even if it is the called epId,
how the peer endpoint can ever know the called epId, since it does not appear ARQ/ACF
messages?

I'm not really sure whether I got your question here. When the EP does not have an identifier yet, as might occur in early RAS messages, then D.10 say to fill-in NULL instead.

Section D.10 throws some insight into the usage of senderId and generalId, but
it does it so only for RAS messages.

Do you think it is necessary to make sendersID and generalID explicit in the table in D.9.2? There shouldn't be any exceptions such as in the case of RAS where

2) Section D.9.1 of H.235 V2 states the 225 UUIEs which shall contain cryptoTokens
field. H.323 V4 has added new UUIEs (Status, Status Enquiry,...).

Ooops, this actually has been an oversight and not any intentional. Of course, the additional H.323 V4 signaling messages such as Status, Status inquiry, Setup-ack and notify-UUIEs etc shall be covered and secured as well. And similar correction is also necessary for Annex E. The IG provides the necessary corrections.

Does that mean
that H.323 V4 can not possibly use H.235 V2?

Absolutely not. H.323 v4 and H.225.0 V4 were designed in such a way that H.235v2 deployment is possible.


best regards
Manoj Paul.


-----Original Message-----
From: ssilvy at hss.hns.com [mailto:ssilvy at hss.hns.com]
Sent: Thursday, May 31, 2001 9:26 PM
To: mpaul at TRILLIUM.COM; ITU-SG16 at mailbag.cps.INTEL.COM
Subject: Re:





Hi,

In case of initial RRQ when EPID is not available the table D.10 in H235v2
says that sendersID would be NULL.
So the hash would be calculated with sendersID as NULL when the
identification information i.e EPID is not available as in initial RRQ.

Silvy.




Nagesh Kumar B V
06/01/2001 10:40 AM

To:   Silvy Samuel/HSSBLR at HSSBLR, Ivan T Varghis/HSSBLR at HSSBLR
cc:

Subject:


---------------------- Forwarded by Nagesh Kumar B V/HSSBLR on 06/01/2001
09:46 AM ---------------------------


"Paul, Manoj" <mpaul at TRILLIUM.COM> on 05/31/2001 06:35:31 PM

Please respond to "Paul, Manoj" <mpaul at TRILLIUM.COM>

To:   ITU-SG16 at mailbag.cps.INTEL.COM
cc:    (bcc: Nagesh Kumar B V/HSSBLR)

Subject:




 Hi All,

   I have a question on the use of H.235 Annex D (Baseline Security
Profile). According
to this profile, except for GRQ/GCF messages, all other RAS messages shall
contain a hash
value computed using HMAC-SHA1-96 algorightm on the entire RAS message.
Consider an
endpoint sending RRQ to the Gk. In the clearToken field of RRQ message, the
endpoint shall
fill generalId as gkId (which it got in GCF) and senderId as it's own epId.
EpId is
generally returned to the endpoint by the gatekeeper in RCF. That means
that
an endpoint
may not have an epId while sending RRQ to Gk. In such a case, how it is
supposed to
fill the senderId and compute the hash value on complete RRQ message?
Any pointers are appreciated.




thanks
Manoj Paul.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For help on this mail list, send "HELP ITU-SG16" in a message to
listserv at mailbag.intel.com

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For help on this mail list, send "HELP ITU-SG16" in a message to
listserv at mailbag.intel.com

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For help on this mail list, send "HELP ITU-SG16" in a message to
listserv at mailbag.intel.com



More information about the sg16-avd mailing list