RE: iSCSI-12-95

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

How about the following text:

       If CHAP is used with a 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
       connec-tion. Moreover, in this case IKE authentication with group
       pre-shared keys MUST NOT be used unless it is not essential to
       protect group members against off-line dictionary attacks of other
       members. When CHAP is used with secret shorter than 96 bits, a
       compliant implemen-tation MUST NOT continue with the login unless it
       can verify that IPsec encryption is being used to protect the
       connection.

 Julo
----- Forwarded by Julian Satran/Haifa/IBM on 06/01/2002 06:41 PM -----
                                                                                                                                      
                      Julian Satran                                                                                                   
                                               To:      "THALER,PAT (A-Roseville,ex1)" <pat_thaler@agilent.com>                       
                      05/31/2002 07:18         cc:      ips@ece.cmu.edu                                                               
                      AM                       From:    Julian Satran/Haifa/IBM@IBMIL                                                 
                                               Subject: RE: iSCSI-12-95(Document link: Julian Satran - Mail)                          
                                                                                                                                      
                                                                                                                                      
                                                                                                                                      
                                                                                                                                      
                                                                                                                                      
                                                                                                                                      



Pat,

Comments in text.

Julo


                                                                                                                                      
                      "THALER,PAT                                                                                                     
                      (A-Roseville,ex1)        To:       Julian Satran/Haifa/IBM@IBMIL, ips@ece.cmu.edu                               
                      "                        cc:                                                                                    
                      <pat_thaler@agile        Subject:  RE: iSCSI-12-95                                                              
                      nt.com>                                                                                                         
                                                                                                                                      
                      05/31/2002 12:52                                                                                                
                      AM                                                                                                              
                      Please respond to                                                                                               
                      "THALER,PAT                                                                                                     
                      (A-Roseville,ex1)                                                                                               
                      "                                                                                                               
                                                                                                                                      
                                                                                                                                      



Julian,

I am having two problems with the second MUST in the following paragraph
from iSCSI-12-95 7.2.1:
If CHAP is used with a 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 authentication with group pre-shared
keys MUST NOT be used. 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.

Who or what does the requirement apply to? Is the iSCSI implementation
expected to check whether IKE is using pre-shared keys or is this a
requirement on the person setting up the security? It isn't clear to
me that an iSCSI implementation has access to that information.

+++ the requirement about checking length is an implementation requirement
(if you can't check that you have IPsec then you must fail login). The
requirement about IKE is for the administrator/manager at least.+++

Secondly, it isn't clear to me why it is required. I'm assuming the
concern is that a member of a group with preshared keys could use
an off-line dictionary attack to crack the CHAP secret of another
member of the group but it seems to me that there are situations
where this is not a threat. For instance, one could have a group that
was a host and multiple equally secure disk arrays. If one isn't
concerned about one of the arrays trying to impersonate another there
isn't a danger in allowing them to authenticate with CHAP protected
by IPsec enryption with a group pre-shared key.

Could the MUST be made a SHOULD with a statement that ignoring the
SHOULD means that one member of the group could crack the CHAP
secret of another member?

+++ this is a fair assessment of the situation and I think that your
suggestion makes sense +++

Regards,
Pat

-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Wednesday, May 29, 2002 3:02 PM
To: ips@ece.cmu.edu
Subject: iSCSI-12-95


12-95 is out.
It has the latest wording on security and text negotiation (including the
spanning).

Still to go - text fixes in chapter 11.

Julo