GPP Password Retrieval with PowerShell
Archived: 2026-04-05 17:39:46 UTC
Last week, I read a great post entitled "Exploiting Windows 2008 Group Policy Preferences" that I wish I saw
sooner.  The article included a nice Python script to accomplish the task of decrypting passwords that were set
using the GPP feature in Windows 2008 domains.  However, it looked like something that would be handy to have
in a PowerShell script.  Before I continue, I would like to point out the updated disclaimer, it certainly applies to
this post.
You should read the original article, but the quick summary is that its possible for any authenticated user (this
includes machine accounts) on the domain to decrypt passwords that are enforced with Windows 2008 Group
Policy Preferences.  From my experience, this practice is common for larger domains which need to set different
local administrator ("500" account) passwords for different OUs.
Python is an excellent scripting language, but PowerShell has two notable advantages in this specific use-case. 
First, PowerShell does not require any additional libraries since it has access to the entire .NET framework. 
Second, PowerShell is installed by default on all modern Windows systems to include Windows Server 2008 so it
can be used right from the machine you are on.
The following Get-GPPPassword PowerShell script can be used by penetration testers to elevate to local
administrator privileges (on your way to Domain Admin) by downloading the "groups.xml" file from the domain
controller and passing it to the script.  The files are typically found in:
\\domain\SYSVOL\domain\Policies\{*}\Machine\Preferences\Groups\Groups.xml
Get-GPPPassword (Use Updated Version)
To run the function, just copy and paste the text into powershell and type 'Get-GPPPassword'. This will in effect
bypass the ExecutionPolicy.
Writing this script ended up not being as easy as I originally thought mostly due to never dealing with .NET and
crypto before.  I would like to thank Matt Graeber for solving the null IV issue, Mike Santiago for general code
improvements and of course Emilien Giraul (and the Sogeti ESEC Pentest team for their detailed writeup).
Try it out and let me know what you think.
***Update 26 May 2012***
You can also download the maintained version of the script from the PowerSploit repository on GitHub.  It already
has some great scripts for Windows post-exploitation on it!
https://obscuresecurity.blogspot.co.uk/2012/05/gpp-password-retrieval-with-powershell.html
Page 1 of 2

***Update 16 June 2012***
Updated the script block with the improvements from Matt Graeber.  Matt wrapped it into a function and
apparently saved a puppy by creating a new object (avoiding the use of write-host).
***Update 3 July 2013***
I have reorganized and rewritten the script. You can find the updated version and read about it here.
-Chris
Source: https://obscuresecurity.blogspot.co.uk/2012/05/gpp-password-retrieval-with-powershell.html
https://obscuresecurity.blogspot.co.uk/2012/05/gpp-password-retrieval-with-powershell.html
Page 2 of 2