Kerberos Implementation in a distributed Windows environment

[Tim Alsop]

Sanford,

You might be able to turn off replay detection. However, if you are able to turn it off it would be less secure.

Tim. 

-----Original Message-----
From: sanford.sham at accenture.com [mailto:sanford.sham at accenture.com] 
Sent: 10 October 2003 21:12
To: Tim Alsop
Cc: kerberos at mit.edu
Subject: RE: Kerberos Implementation in a distributed Windows environment


That's correct, and is one of the propsed solution. However, that would make the system not very scalable, and also makes it harder to maintain. I was just wondering whether what people thinks about this...is there anthoer way?

Thanks

Regards
Sanford
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Sanford Sham
Accenture
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email: sanford.sham at accenture.com



                                                                                                                                        
              Tim Alsop                                                                                                                 
              <Tim.Alsop at CyberSafe.Ltd.         To:      Sanford Sham/Internal/Accenture at Accenture, kerberos at mit.edu                    
              UK>                               cc:                                                                                     
                                                Subject: RE: Kerberos Implementation in a distributed Windows environment               
              10/10/2003 03:55 PM                                                                                                       
                                                                                                                                        
                                                                                                                                        



Sanford,


Is it possible for you to use a unique Kerberos principal for each service on the EAI boxes ? This would avoid replay attack detection issues.


Thanks, Tim.


-----Original Message-----
From: sanford.sham at accenture.com [mailto:sanford.sham at accenture.com]
Sent: 08 October 2003 00:52
To: kerberos at mit.edu
Subject: Re: Kerberos Implementation in a distributed Windows environment


Hi


I'm just writing to ask a question, currently related to my project.


We are trying to implement Kerberos security in our distributed Windows environment. We have, more than one, dedicated Windows 2k boxes (let's called them EAI boxes) that are used to communicate with WebSphere servers, using Kerberos tickets etc.


We have more than one EAI boxes that's online at any given time. All the NT services are hosted under the same Windows domain account. Bascially, it's as if the same domain account is used to host multiple services, on multiple machines.


The problem comes when simultaneous transactions are conducted. Let's say all EAI boxes fires a transactions to the same Websphere services at the same time. Since it's hosted by the same domain account, the user that is seen on the kerberos ticket is the same. Also, since it is fired at the same time, the timestamp is the same (or very close). Therefore, after receiving the first transactions, Websphere rejects all subsequent transactions on the basis of duplicate Kerberos tickets being sent (or replay).


Microsoft says that there is nothing they can do to fix this. They argue that the standard specifies that only [Client Id, Timestamp] is used in the authenticator, and they would not modify this to make the authenticator more unique.


Can you provide a view on this? Thanks very much for you help.


Regards
Sanford





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