Creating a Hashed Password for VNC

For an automated installation project at work I needed to set the password to an UltraVNC server running on Windows.  VNC is a remote desktop protocol and very handy.  For good reason the server's password is not stored in the clear, but rather a (now weakly) encrypted version.

Unfortunately, while the admin GUI of the program will gladly create the result for you and save it to the ultravnc.ini file or registry, what if you need to do it without human intervention?  Even trained chimps are expensive these days and tend to throw crap around when bored.  No one will be around to bring up the window and type it in by hand.

It's a shame to waste time on such a thing because the program really should support it at the command line.  After a few hours of googling, combing forums and source code for answers, I gave up and hacked together something myself.   Instead I used Python to create the "cypher text", which can then be saved to the .ini file or to the Windows registry in whatever manner is easiest.  Since you can choose where to put it, supporting other VNC products is possible too.

I'll squeeze the good parts in here.

Steps:

1. Install a modern Python 2.x if you don't have it.
2. Download this module that handles the nuts and bolts of the encryption algorithm: d3des.py
3. Copy the code below to a file named something like "vnc_enc.py" and save to the same folder:
   

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   import d3des as d # for brevity - narrow column def get_vnc_enc(password): passpadd = (password + '\x00'*8)[:8] strkey = ''.join([ chr(x) for x in d.vnckey ]) ekey = d.deskey(strkey, False) ctext = d.desfunc(passpadd, ekey) return ctext.encode('hex') if __name__ == '__main__': import sys if len(sys.argv) > 1: print get_vnc_enc(sys.argv[1]) else: print 'usage: %s <password>' % sys.argv[0]

4. To print the result to the console:
   

   C:\> vnc_enc.py foo  
   2a4180b2e31f5790
   

5. Here's a batch file to take a password and write it to the UltraVNC registry area.  This is what I needed for work.  It could be saved to the registry directly with Python, but I've opted to keep these parts of the program separate.  Name it pass2reg.cmd or similar:

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   @echo off setlocal if "%1" == "" ( echo usage: %0 ^<password^>     exit /b ) set regkey=HKLM\SOFTWARE\ORL\WinVNC3\Default set valname=Password rem clumsy cmd way to set value to env var for /f "delims=" %%H in ('vnc_enc.py %1') do set ctxt=%%H echo VNC Text is: %ctxt% echo Writing to: %regkey%\%valname% reg add %regkey% /v %valname% /t reg_binary /f /d %ctxt% echo Writing to: %regkey%\%valname%2 reg add %regkey% /v %valname%2 /t reg_binary /f /d %ctxt%

6. If you need to write the result to an ini file instead, try Python's ConfigParser module.  It is easy to use.

That's it.  Python saves the day again.  I'm sure a few minutes from now I'll find someone already solved it.  Happy weekend!