H.235 Security Blues

Euchner Martin Martin.Euchner at ICN.SIEMENS.DE
Wed Jul 25 04:31:06 EDT 2001


Hi Manoj,

the GK determines whether to apply mutual authentication; i.e. authenticate and integrity protect the RAS messages towards the EP. This is a matter of security policy and therefore something, that is a local matter. For security reasons, I would recommend applying mutual authentication instead on just single sided authentication.

There is no need to negotiate this feature, as an endpoint can always recognize whether messages from the GK are secured or not. The EP does this by looking at the presence of the various OIDs in the security tokens. Missing OIDs = no security. Thus, this feature is always indicated in-band in each message.


Kind Regards,

Martin Euchner.
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 -----Original Message-----
From:   Paul, Manoj [mailto:mpaul at trillium.com]
Sent:   Tuesday, July 24, 2001 7:55 PM
To:     'Euchner Martin'; ITU-SG16 at mailbag.cps.INTEL.COM
Subject:        RE: H.235 Security Blues

Hi Martin,

 Thanks for your response. I have an additional question under section
D.6.3.1
of H.235V2. Second para of this section states that Gk decides whether to
apply Auth/Int in the reverse direction as well. I could not find any IE in
GRQ/GCF where GK could inform the endpoint if messages originating from GK
will also contain hash values and that EPs should also auth/int them. Does
GK
tell endpoints to apply Auth/Int in reverse direction also by out-of band
mechanisms (something during password subscription etc.)?

thanks
Manoj.

-----Original Message-----
From: Euchner Martin [mailto:Martin.Euchner at ICN.SIEMENS.DE]
Sent: Tuesday, July 24, 2001 9:39 AM
To: ITU-SG16 at mailbag.cps.INTEL.COM
Subject: Re: H.235 Security Blues


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.
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| 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/
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| __________________
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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/
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 -----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.

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