RE: Denial of service when using Active Directory for KDC ?
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. [email]service.account@domain.com[/email]). 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 [email]service.account@domain.com[/email] 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@domain format ?
I look forward to your feedback.
Regards, Tim
________________________________
From: jpbermejo [mailto:jpbermejo@prisacom.com]
Sent: Fri 06/05/2005 09:34
To: Markus Moeller; Tim Alsop
Cc: [email]kerberos@mit.edu[/email]
Subject: Re: Denial of service when using Active Directory for KDC ?
On Thu, 2005-05-05 at 21:52 +0100, Markus Moeller wrote:[color=blue]
> 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.[/color]
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@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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RE: Denial of service when using Active Directory for KDC ?
On Fri, 2005-05-06 at 11:28 +0200, Tim Alsop wrote:[color=blue]
> 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.[/color]
I did use that method many months ago, with a 2000 domain. Now, with a
2003 domain I've actually never tried ktpass seriously, and I use either
samba or css_adkadmin. The first one forces node.domain.com into node$
as principal name, where the second allows HOST/node.domain.com. Both
are standar computer accounts as any other windows machine.
You can get a TGT (or any other tickets) for these principals using the
proper keytab.
[color=blue]
> 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@domain format ?[/color]
As I don't use ktpass anymore, no alias or mapping to user accounts is
performed. With both samba and adkadmin you can create service
principals, and those are again pure windows service principals (as, for
example LDAP/your.domain.controller). Those principals, at least on the
unix side, are not allowed to acquire tickets (neither tgt nor service
ones), so they cannot be 'denialed' anyway as the keytab is only used to
decrypt tickets from other requesting principals.
Javier Palacios
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