Sunday, 1 May 2011

Metasploit Meterpreter Registry OpenKey and VNC PW Module

As you probably already know I've been doing some work with Metasploit post modules. This recent work has focused heavily on Registry functions. While doing this work I noticed a disturbing behavior. When Meterpreter checks to see if a key exists it was calling RegCreateKey instead of RegOpenKey.  RegCreateKey will attempt to create any and all keys in the supplied path that do not already exist. RegOpenKey, however, will not create the key if it doesn't already exist.

In Metasploit the registry.rb 'client-side' function is set up as a wrapper to the create_key function. Similarly the registry.c code for Meterpreter itself is set up this way. Calls to the OpenKey function were just passed on to the create_key function. I have now submitted a patch to correct this behaviour. The registry.rb function now sends a call via the meterpreter stdapi to the request_registry_open_key function. The request_registry_open_key function will appropriately call RegOpenKey instead. If/when this patch is accepted by the Metasploit team, it will make the Registry functions of Meterpreter much less invasive/noisy.

I have also gone ahead and submitted a patch for the enum_vnc_pw Post Module. The module as it currently stands will check the HKEY_Current_User keys for user-mode vnc passwords. However, this will only work if meterpreter is running udner the permissions of the user who is running the vnc server. I have added behaviour that will try to enumerate all userswith SIDs in HKEY_Users and then check each one that it can access, to see if it has stored VNC passwords. The get_reg function also had to be re-written to deal with possibile permissions issues if meterpreter does not have rights to access each users' registry. The best way to run this module will, of course be under SYSTEM priveleges as it will have access to every user. This will hopefully make the enum_vnc_pw module more effective at gathering it's data.


  1. Where did you submit the update to? I can't find it on Redmine, but I have been known to be blind.

  2. Mubix: I assume you mean for the VNC PW module it is at
    The Meterpreter Registry changes are submitted at:
    but I'm guessing Jcran will have to have a field day with that one before it would get fully approved.