RE: iSCSI: 7.2.1 CHAP Considerations (12-98)

["Julian Satran" <Julian_Satran@il.ibm.com>]

The text I would suggest in 7.2.1 is:

If an initiator or target generates or verifies a CHAP secret that has less than 96 random bits then IPsec encryption (according to the implementation requirements in Section 7.3.2 Confidentiality) MUST be used to protect the connection. Moreover, in this case IKE authenti-cation with group pre-shared keys SHOULD NOT be used unless it is not essential to protect group members against off-line dictionary attacks by other members. When CHAP is used with secret shorter than 96 bits, a compliant implementation MUST NOT continue with the login unless it can verify that IPsec encryption is being used to protect the connection.

Julo

Ofer Biran/Haifa/IBM@IBMIL Sent by: owner-ips@ece.cmu.edu 06/13/2002 11:53 AM Please respond to Ofer Biran

To:        Black_David@emc.com         cc:        ssenum@cisco.com, ips@ece.cmu.edu         Subject:        RE: iSCSI: 7.2.1 CHAP Considerations (12-98)

How about:

  When CHAP is used with secret shorter than 96 bits,
  a compliant implementation MUST NOT continue with
  the login step in which it should send a CHAP response
  (CHAP_R - see 10.5) unless it can verify that IPsec
  encryption is being used to protect the connection.

On initiator-only authentication this puts the responsibility
only on the initiator implementation who surely knows the
secret and its length.


  Regards,
     Ofer


Ofer Biran
Storage and Systems Technology
IBM Research Lab in Haifa
biran@il.ibm.com  972-4-8296253


Black_David@emc.com@ece.cmu.edu on 13/06/2002 02:26:07

Please respond to Black_David@emc.com

Sent by:    owner-ips@ece.cmu.edu


To:    ssenum@cisco.com
cc:    ips@ece.cmu.edu
Subject:    RE: iSCSI: 7.2.1 CHAP Considerations (12-98)



Yes, my intent was to modify the draft text to include the
"essential condition" described below.  --David

> -----Original Message-----
> From: Steve Senum [mailto:ssenum@cisco.com]
> Sent: Wednesday, June 12, 2002 6:14 PM
> To: Black_David@emc.com
> Cc: ips@ece.cmu.edu
> Subject: Re: iSCSI: 7.2.1 CHAP Considerations (12-98)
>
>
> David,
>
> What you state would be better, but that is
> not what the current text (as of 12-98) says.
>
> Steve Senum
>
> Black_David@emc.com wrote:
> >
> > I think the essential condition here is that the
> > "do not continue if secret is shorter than 96 bits"
> > criteria should apply only to implementations that
> > know and use the secret (i.e., generators of CHAP
> > responses, and recipients of those responses that
> > do their own verification as opposed to outsourcing
> > that verification to something like a RADIUS server).
> >
> > Thanks,
> > --David
> > ---------------------------------------------------
> > David L. Black, Senior Technologist
> > EMC Corporation, 42 South St., Hopkinton, MA  01748
> > +1 (508) 249-6449 *NEW*      FAX: +1 (508) 497-8500
> > black_david@emc.com         Cell: +1 (978) 394-7754
> > ---------------------------------------------------
> >
> > > -----Original Message-----
> > > From: Steve Senum [mailto:ssenum@cisco.com]
> > > Sent: Wednesday, June 12, 2002 3:58 PM
> > > To: Julian Satran
> > > Cc: ietf-ips
> > > Subject: Re: iSCSI: 7.2.1 CHAP Considerations (12-98)
> > >
> > >
> > > Julian,
> > >
> > > In the case where an iSCSI Target is authenticating
> > > an iSCSI Initiator, the Target sends a CHAP
> > > challenge and identifier, and the Initiator sends
> > > back a CHAP response and username.
> > >
> > > In the case were the Target is using the RADIUS
> > > protocol, these four pieces of information are
> > > sent by the Target to a RADIUS server, which
> > > simply gives an accept or reject reply.  The target
> > > never has access to the CHAP secret (which is good),
> > > hence no check can be made on its length.
> > >
> > > Regards,
> > > Steve Senum
> > >
> > > Julian Satran wrote:
> > > >
> > > > can you elaborate? Julo
> > > >
> > > >   Steve Senum <ssenum@cisco.com>
> > > >   Sent by: owner-ips@ece.cmu.edu         To:        ietf-ips
> > > >                                  <ips@ece.cmu.edu>
> > > >   06/12/2002 09:32 PM                    cc:
> > > >   Please respond to Steve Senum          Subject:
> > > iSCSI: 7.2.1 CHAP
> > > >                                  Considerations (12-98)
> > > >
> > > >
> > > >
> > > > I have a concern over the wording of the
> > > > following text from section 7.2.1 (12-98 version):
> > > >
> > > >    When CHAP is used with secret shorter than 96 bits,
> > > >    a compliant implementation MUST NOT continue with
> > > >    the login unless it can verify that IPsec encryption
> > > >    is being used to protect the connection.
> > > >
> > > > I know the above is attempt to "put some teeth" into
> > > > the requirements to make the use of CHAP secure,
> > > > but I believe there are common cases where the
> > > > length of the CHAP secret cannot be verified, such
> > > > as when a RADIUS server is being used.
> > > >
> > > > Regards,
> > > > Steve Senum
> > >
>