Logging on through Terminal Services on a Windows Server 2003 Domain Controller

I work extensively with multi-domain forests, usually in a configuration with an empty root domain and several child domains that host users and computers etc. The other day I was trying to log on to a newly added Domain Controller in a child domain. I was going to prepare the domain for Exchange so I was trying to log on with an account that was a member of the Enterprise Admins group in the root domain. This usually works very well, because this group is always a member of the local Administrators group in any child domain. This time however I could not log on and got this error message:
To log on to this remote computer, you must be granted the Allow log on through Terminal Services right. By default, members of the Remote Desktop Users group have this right. If you are not a member of the Remote Desktop Users group or another group that has this right, or if the Remote Desktop Users group does not have this right, you must be granted the right manually.

This, of course, led me to investigate. The first thing I discovered was that this Domain Controller had also been made a Terminal Server. I won’t go into how bad an idea that is here, suffice to say that I do not recommend it. From this fact it followed that someone also probably had changed the default settings of the Allow log on through Terminal Services right in some policy, and that was probably the reason I could not log on. Sure enough. The Default Domain Policy had been changed (again, not a good idea), granting the Allow log on through Terminal Services right to a global group in the domain only. Let’s call that group TSUsers. I also discovered that the same someone had also added the TSUsers group to the Remote Desktop Users group. Normally that should have been enough to allow log on through Terminal Services. Obviously it wasn’t. So I had two problems. First, why could I not log on as a member of the Administrators group when the Default Domain Policy had been changed, and second; why was it not enough to add the TSUsers group to the Remote Desktop Users group to allow them to log on through Terminal Service?
By default, the Allow log on through Terminal Services right is controlled through the Local Computer Policy, the one you can edit with gpedit.msc. The default setting for Windows Server 2003 is to grant this right to the Administrators and Remote Desktop Users local groups. If the server is promoted to a Domain Controller, the Remote Desktop Users group is removed from the Local Computer Policy, leaving only the Administrators group.  So on a Domain Controller it is not enough to be a member of the Remote Desktop Users group to log on through Terminal Services. You must be a member of the Administrators group in the domain. That is probably what confused the person who had set up the server. He had added his domain group (TSUsers) to the Remote Desktop Users group and been unable to log on, since the server was a DC. That answered my second question. To solve this problem he edited the Default Domain Policy and gave the right to his domain group. But in doing so he overrode the Local Computer Policy, which gives members of the Administrators group access. This was what made me unable to log on to the server, and the answer to my first question. Easy!
Interestingly enough the text in the Remote tab on a Domain Controller does not change, even if Remote Desktop Users no longer can log on through Terminal Services. It still says that members of the group has access.
To solve my immediate problem I added the Enterprise Admins group to the Default Domain Policy in the child domain and was able to log on and do my Exchange preparation. This setup is obviously not recommended. A DC should never be a Terminal Server and domain based policies should not be changed in such a way as to lock out administrators.
In researching this post I also found out another interesting thing about Terminal Services in Windows Server 2003. You no longer have to give a user or group both the Log on locally and Allow log on through Terminal Services rights to be able to log on via Terminal Services. This was needed in Windows 2000. In Windows Server 2003 it is handled this way:
  • Log on locally controls logon via the console (not RDP console, but keyboard attached to the server)
  • Allow log on through Terminal Services controls logons via Terminal Services.
You can read more about that in this KB article:
Difference in the user right “Deny log on locally” between Windows 2000 and Windows 2003
http://support.microsoft.com/kb/837954/en-us

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