Ringzer0CTF – Cryptography – I lost MY password Can you find it?

Ringzer0CTF – Cryptography – I lost MY password Can you find it?

Objective:

Get the flag…… I don’t know what else to put here

Solution:

So this level give you a tar file

I downloaded the tar and unzipped it

There is a policies folder with the following folders inside

02/06/2014  09:20 AM    <DIR>          .
02/06/2014  09:20 AM    <DIR>          ..
02/05/2014  03:59 PM    <DIR>          {31B2F340-016D-11D2-945F-00C04FB984F9}
02/05/2014  03:59 PM    <DIR>          {6AC1786C-016F-11D2-945F-00C04fB984F9}
02/06/2014  09:22 AM    <DIR>          {75DE8F0A-DEC0-441F-AE29-90DFAFCF632B}
02/06/2014  08:20 AM    <DIR>          {874C2133-64E1-4F2C-8BD8-71D9BD59643D}
02/06/2014  08:29 AM    <DIR>          {C7BD6C6D-A1C8-4C23-815E-3D8D4187640F}
               0 File(s)              0 bytes
               7 Dir(s)  326,238,683,136 bytes free

I poked through the directory and found an interesting file in one

In this directory d22fdb09ef96576dfc49076a9322a555\Policies\{75DE8F0A-DEC0-441F-AE29-90DFAFCF632B}\User\Preferences\Groups>

It is a groups.xml file

Which contains

<?xml version="1.0" encoding="UTF-8"?>
 -<Groups clsid="{3125E937-EB16-4b4c-9934-544FC6D24D26}">
  -<User clsid="{DF5F1855-51E5-4d24-8B1A-D9BDE98BA1D1}" removePolicy="0" userContext="0" uid="{C73C0939-38FB-4287-AC48-478F614F5EF7}" changed="2014-02-06 19:33:28" image="1" name="Administrator (built-in)">
 <Properties userName="Administrator (built-in)" subAuthority="" acctDisabled="0" neverExpires="1" noChange="0" changeLogon="0" cpassword="PCXrmCkYWyRRx3bf+zqEydW9/trbFToMDx6fAvmeCDw" description="Administrator" fullName="Administrator" action="R"/>
 </User>
 </Groups>

Ooooohhh there is something called cpassword there, lets google that

https://adsecurity.org/?p=2288

This site says that this is and AES-256 encrypted password for the Administrator account. 

However Microsoft actually published their AES key online at some point in time making it pretty trivial to crack

Rapid7 has a pretty good write up about it https://blog.rapid7.com/2016/07/27/pentesting-in-the-real-world-group-policy-pwnage/

So If Rapid7 has pretty good write up about it…. Guess what that means?

Someone has already created a decryption tool for it and its preloaded in Kali

 gpp-decrypt
➜  ~ gpp-decrypt
Usage: gpp-decrypt: encrypted_data

So syntax is the application followed by the encrypted data. let’s put in the hash and see what happens

➜  ~ gpp-decrypt PCXrmCkYWyRRx3bf+zqEydW9/trbFToMDx6fAvmeCDw
/usr/bin/gpp-decrypt:21: warning: constant OpenSSL::Cipher::Cipher is deprecated
LocalRoot!

We get an error about a Cipher being deprecated but after that we get the decrypted password

LocalRoot!