RE: Group membership / Kerberos tickets

From: Zack Schiel (ZSchiel_at_blueandco.com)
Date: 04/28/05

  • Next message: Marc Fossi: "SecurityFocus Microsoft Newsletter #238" 
    Date: Thu, 28 Apr 2005 15:23:05 -0500
To: <focus-ms@securityfocus.com>

    We have an OU structure similar to this as well, however in this particular case we're talking about SUS server GPOs, which ideally should be set according to a machine's *current* location rather than its 'usual' place of residence.  The issue we're addressing is that of mobile users being in the 'wrong' office when large updates are approved; the way around this is to determine the local SUS server by site. 

    -Z-

    ________________________________________
    From: mcurole@shawinc.com [mailto:mcurole@shawinc.com]
    Sent: Thursday, April 28, 2005 2:59 PM
    To: focus-ms@securityfocus.com
    Cc: Zack Schiel
    Subject: RE: Group membership / Kerberos tickets

    What is your OU structure like? We have on OU for servers e.g. ou=server,dc=company,dc=com and an OU for our PC e.g. ou=workstations,dc=company,dc=com. Then you just link your GPO to the workstations ou.

    Mark

    "Laura A. Robinson" <larobins@bellatlantic.net> wrote on 04/28/2005 01:19:40 PM:

    > 1. Yes, you are on the right track; this is [cringe- I hate this phrase]
    > expected behavior.
    > 2. Have you tried using Kerbtray or another utility to purge the servers'
    > tickets?
    > 3. If you don't purge the tickets and get new ones, then you're stuck with
    > either waiting for about a week if you have the default Kerberos settings in
    > your domain, or you have to reboot the servers.
    > 4. This is the nature of Kerberos; it's not instantaneous in terms of
    > deny/grant/group population changes.
    >
    > Laura
    >
    > > -----Original Message-----
    > > From: Zack Schiel [mailto:ZSchiel@blueandco.com]
    > > Sent: Thursday, April 28, 2005 10:52 AM
    > > To: focus-ms@securityfocus.com
    > > Subject: Group membership / Kerberos tickets
    > >
    > > I'm hoping that someone here can confirm this for me and
    > > possibly give a deeper explanation for the behavior that we're seeing.
    > >
    > > Essentially, we are in the process of creating a series of
    > > site GPOs; the default Authenticated Users permission
    > > remains, and we've also denied Read and Apply Group Policy to
    > > a new group containing certain computers, mainly servers. 
    > > The problem that we're running into is that these servers
    > > don't appear in RSoP reports as members of the new security
    > > group (even though they have been for nearly 24 hours now),
    > > and thus they are receiving and applying these GPOs.  When
    > > the machines are rebooted, they correctly add the group to
    > > their list of security groups to which they belong, and the
    > > GPOs are denied. 
    > >
    > > The obvious solution is to reboot the servers before linking
    > > the GPO.  We would of course prefer to avoid rebooting dozens
    > > of servers, however. 
    > >
    > > I believe the reason this happens is that a machine receives
    > > its TGT at startup, and the TGT contains SIDs for groups to
    > > which the machine belongs.  This TGT is then simply renewed
    > > every X number of hours for several days, and thus the list
    > > of SIDs isn't updated until the ticket is actually reissued
    > > at restart.  Am I on the right track here?  Is there a
    > > relatively easy way to force a machine to reissue its TGT
    > > without rebooting or causing other issues? 
    > >
    > > Aside from our current predicament, this seems to be a bit of
    > > a security hole-machines can actively receive GPOs to which
    > > they have been denied access, long after they are denied that
    > > access. 
    > >
    > > Thanks,
    > >
    > > -Zack-
    > >
    > > ______________________
    > > Zack Schiel
    > > Network Support
    > > Blue & Co., LLC
    > >
    > >
    > >
    > > --------------------------------------------------------------
    > > -------------
    > > --------------------------------------------------------------
    > > -------------
    > >
    >
    >
    > ---------------------------------------------------------------------------
    > ---------------------------------------------------------------------------
    >
    >
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