Posts Tagged ‘impacket’

So after my last article, in which I describe an alternative way to execute code on a remote machine if you have the local administrator’s password, I kept wondering what else could be done with the remote registry? The first thing I immediately thought of was dumping the windows hashes. The reason I thought of this was because it would have several advantages:

  • You would not need to bypass anti virus
  • You would not need to worry about uploading executable files
  • You would not need to worry about spawning new processes on the remote machine
  • You would only need one open port

Since I dislike reinventing the wheel (unless it’s for educational purposes) I started to first search around and see what current methods are available. As far as I can tell they all boil down to the following:

  • Use psexec to dump hashes by
    • Spawning a new process and running reg.exe
    • Uploading your own executable and running it
  • Use WMI to spawn a new process and run reg.exe
  • Use Windows tools
    • regedit.exe / reg.exe
    • Third party (WinScanX)

If you are not interested in my first failed attempt, the learned things you can skip directly to the script on GitHub as usual. Keep reading if you want to know the details. In case you are wondering: Yes I used impacket, it rocks.

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For me the fun in hacking still remains in finding new ways to achieve the same goal. On one of those days with splendid sun and people having their beer, I thought it would be a good idea to start researching how to get a remote Windows shell without using any of the more  well known methods and preferably from a Linux host. To set the proper context I’m talking about the situation where you have gathered local administrative credentials and want to start gathering shells all over the network. I started to research the current methods and see how they worked the way they did. Then I did a lot of searching around and also some basic process monitoring stuff. This eventually gave me what I wanted a new?? way to start remote processes without using any of the known methods BUT unfortunately it has one possible drawback: it is not instant like the other well known methods.  Depending on your goal and time this can be as much a drawback as it can be an advantage. The actual method IS NOT really new it’s just used in a remote way. Let’s do a quick recap of the ‘well known’ methods I’m referring to, to make sure we are on the same level:

psexec
This is probably the most well known one and implemented in a dozen ways. The basics revolve around uploading an executable and creating a service that starts the executable. It’s efficient, reliable and thoroughly tested. It works from Windows and Linux hosts.

Windows Management Instrumentation (WMI)
This one is often used from visual basic script files or powershell scripts to exeute processes remotely. As far as I can tell it uses some undocumented dcerpc functions. It works very nice from Windows host, but I haven’t seen a Linux implementation yet. There is a libwmi library but I think it only does WMI queries, please correct me if I’m wrong.

Windows Remote Management / Shell (WinRM / WinRS)
This one is pretty neat since it uses the mechanisms provided by Windows to give you a direct shell without uploading anything or making use of temporary files. There is a nice write up about it on the rapid7 website.

Managed Object Format (MOF)
This one seems to have come into existing with Stuxnet and is pretty sexy. All you have to do is drop a correctly prepared file and Windows will execute it.

Looking at all these methods there are a two things that caught my attention:

  • DCE/RPC is pretty powerful
  • Eventually you want to upload your own executable (ex: meterpreter)

If you are impatient you can skip to the source of the POC on github, if you want to know more keep reading.

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