Denial of service when using Active Directory for KDC ?

[Tim Alsop]

Javier,
 
Thankyou. I have a related question for your :
 
In order to use a user account which is then used to run ktpass against I need to first create the user account (e.g. service.account at domain.com). When I use ktpass I specify the name of this account using the -mapuser parameter. 
 
With the above in consideration, surely it is possible to use kinit, or windows logon, or some other authentication method to logon as service.account at domain.com and cause this account to get locked when password attempt is wrong > x times ?
 
If I understand it correctly the principal name given when ktpass is run is used as an alias, but the account in AD can still be accessed using the firstname.lastname at domain format ?
 
I look forward to your feedback.
 
Regards, Tim

________________________________

From: jpbermejo [mailto:jpbermejo at prisacom.com]
Sent: Fri 06/05/2005 09:34
To: Markus Moeller; Tim Alsop
Cc: kerberos at mit.edu
Subject: Re: Denial of service when using Active Directory for KDC ?



On Thu, 2005-05-05 at 21:52 +0100, Markus Moeller wrote:
> Tim,
> in our setup we use computer accounts instead of user accounts, and don't
> have experienced this issue. I think the latest ktpass can do this with
> mapuser having a $ at the end.

I don't know about computer accounts, but this DoS is not possible if
you are using service principals. Active Directory doesn't allow login
for service principals, and keytab are only useful to decrypt tickets.
Making an ldap query to AD, you can get things like

dNSHostName: sist03lnx.domain.com
userPrincipalName: HOST/sist03lnx at DOMAIN.COM
servicePrincipalName: HTTP/sist03lnx.domain.com
servicePrincipalName: HTTP/sist03lnx

In this case, only HOST/sist03lnx keytab works with `kinit -k`. If you
attempt to get a TGT with the other principals, you get nothing.

Javier Palacios

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