Managing The Local Administrator Password - Part 2 - The Solution

Jiri Formacek, a Microsoft Services consultant (based on his LinkedIn profile), has published an excellent local admin password management solution. 

The solution uses Group Policy Client Side Extension (CSE) to set random and unique per computer local administrator password that is changed at a user controlled interval (30 days by default). The password is then stored in a confidential Active Directory (AD) attribute. Permission to retrieve the password is controlled using a security group.

The solution is described in the documentation so I won’t be repeating what’s there. I’ll go over the main points and some stuff that’s not covered in the official documentation.  I recommend reading the documentation.

The solution can be downloaded here:

http://code.msdn.microsoft.com/windowsdesktop/Solution-for-management-of-ae44e789

The documentation can be found here:

http://code.msdn.microsoft.com/windowsdesktop/Solution-for-management-of-ae44e789/file/96116/1/Documentation.zip

Implementation requires AD schema extension in order to create two new attributes and add them to the computer object class.  

The two attributes are:

• ms-MCS-AdmPwd – stores the password 
• ms-MCS-AdmPwdExpirationTime – stores the expiration time, password change can be forced by setting the value to “0”

The attributes are marked as confidential so the authenticated users group cannot read the values.

More on confidential attributes here:  http://support.microsoft.com/kb/922836

Access to the attributes is controlled, with a security group. I used two separate groups. One group with read access to the ms-MCS-AdmPwd attribute for retrieving the passwords and the second one with write permission to the ms-MCS-AdmPwdExpirationTime attribute allowing for forcing the reset. In most cases it would be the same group performing both, however I prefer to have an option of separating the tasks. Permission can be granted per OU so you can further subdivide the access. For example based on geographical location.

The passwords can be retrieved using “AD Users and Computers” and ADSIEDIT consoles. Also, the author provided a GUI tool that can be used to easily retrieve admin passwords. The tool is installed along with the management tools.

The Client Side Extension (CSE) is a DLL file that needs to be deployed to and registered on managed computers. A convenient MSI file is provided. It can be deployed using your standard package management tools such as SCCM, Altiris or Group Policy.

The management tools (Group Policy Template, PowerShell scripts, and the GUI tool) are installed using the same MSI. Only the CSE needs to be installed on the managed computers.

The CSE is configured using the provided GPO template. 

 The documentation states that the default password length is 15 characters, in fact it is 12. We definitely want to use at least 15 characters long password as this prevents Windows from storing passwords using insecure LM Hash. More on LanManager here: 

http://computer-forensics.sans.org/blog/2012/02/29/protecting-privileged-domain-accounts-lm-hashes-the-good-the-bad-and-the-ugly

There are two settings in the template:

The CSE has an event log provider that logs to the Application Log. This is detailed in the documentation. I found it useful to set the logging level to the highest during testing.

Summarizing, I find this solution to meet all requirements. I have tested it on a 2012 AD with Win 7 clients and 2012 member servers as well as 2008R2 AD with Win7 and XP clients. I think this is an excellent solution.

A potential concern one may have is that the passwords are stored in clear text in AD directory partition. However, an attacker would have to obtain a copy of the AD database and extract the passwords offline.