No More Prying Eyes
Encoding scripts to prevent unauthorized access.
- By Chris Brooke
I like scripts to be as informative as possible, with vast amounts of
data, status of operations and the like echoed back to me as the script
runs. That’s one reason I use the CScript.exe engine rather than the WScript.exe
engine to execute my scripts (WScript echoes everything in a MessageBox
and requires users to click OK after every echo—it gets tedious after
awhile). But there’s at least one operation where I don’t want anything
echoed back to me: passwords. Whenever a password is entered to log onto
Windows or access protected content on Web sites (or anything else), that
password is obscured. Of course it is! We don’t want any prying eyes seeing
what we’re typing in to gain access to protected systems. Why is it then—considering
how powerful and potentially devastating they can be—we don’t secure our
scripts with passwords? Answer: In certain cases, we should.
As demonstrated last month, some administrative tasks simply can’t be
performed remotely using WMI. There are times when you must actually walk
over to the user’s machine and execute the script locally. Indeed, this
might happen quite regularly. In these cases, there are two choices:
- Copy the script over every time you need it and delete it afterward
(or bring it with you on a floppy disk).
- Secure the script by encoding it and requiring a password before
If you choose the former, more power to you. If circumstances require
choosing the latter (i.e., perhaps you’re not the only admin running the
scripts, and the other admins don’t have access to your “diskette locker”),
then I can help. To be reminded how to encode scripts to prevent unauthorized
access (as best as possible with scripting), refer to my March through
May columns. For enabling password prompts in scripts that don’t echo
typed characters back to the screen, read on.
Windows has a special object created for just this purpose: ScriptPW.Password.
It has only one method—GetPassword, which collects input from the user,
allowing that value to be assigned to a variable.
Dim objScriptPW '... and
Dim strPassword, strValidPWord
WScript.Echo "Enter password to run script:"
If strPassword <>
strValidPWord Then WScript.Quit
'... rest of script
Note: The ScriptPW object comes with Windows XP and Windows
Server 2003. However, because it’s a standard DLL, it should work fine
in Windows 2000 and even Win9x. Simply copy the file “scriptpw.dll” from
an XP or Windows 2003 machine to the desired target machine. Then register
'C:\Windows\System32> regsvr32 scriptpw.dll'"
The above script demonstrates a very straightforward use for the Password
object: Obscure something that’s being typed in and compare it to something
else. Once validated, script execution continues. However, there are many
other uses for this object.
In the October column, WMI was used to connect remotely using different
user credentials. I said, “...hard wiring an admin account and password
into a script is generally a very bad idea.” Well, the Password object
can be used to avoid hard wiring this information into your scripts. In
this case, the script wouldn’t need to be encoded to be secure and effective,
because the entering and comparing of passwords occurs at runtime. Once
the script terminates, all password information is destroyed. A user could
look at your source code all day and not be able to figure out your password.
Here’s a code snippet to illustrate this point:
Set objWMI=objLocator.ConnectServer _
("remotecomputer", "root\cimv2", strUser, strPWord)
It can also be used to obscure any information you don’t want others
to see while working on their systems. Quick story: Where I previously
worked, we had a user we called “Nosy Nellie.” She was the squeaky wheel
that always got the grease from management. Whenever she had any system
trouble (which was quite often), she would sit there and pretend not to
watch as we fixed her system. Sometimes this repair involved accessing
password-protected resources. She would then go directly to management
and demand access to that resource “... or I simply can’t get my work
done!” Next thing, we’d get a memo to give her access to this or that
database, resource and so on. With this new authority, she would proceed
to really screw things up. It got to the point where we’d pretend to be
stumped anytime our repair to her system involved accessing a resource
that she didn’t need to know about. We’d then return to her desk while
she was at lunch and finish fixing her system.
The point is, there are all sorts of reasons to obscure data input. Using
the Password object makes performing this task from within a script a
breeze. As with most things, there are a couple of caveats. First, the
Password object can only be used with CScript.exe. You’ll get an error
if you try to run your script using WScript.exe. Second, the Password
object doesn’t echo back “placeholder” characters like asterisks. Rather,
it simply doesn’t echo anything, so type carefully.
Critical Update: There’s a new version of the Windows Script Host available.
Actually, it’s not a new version but a new build revision. Still, as it’s
important to stay current, I’ve included a link to download the current
version. First, here’s how you determine what version you’re running:
WScript.Echo "Version: " &
WScript.Echo "Build: " &
The version should be (better be) 5.6. Chances are that your current
build version is 6626 (unless you’re already running Server 2003, which
has build 8515). Build 8515 (the latest build for all platforms-XP/Win2K/NT/98)
can be downloaded at http://msdn.microsoft.com/scripting.
Chris Brooke, MCSE, is a contributing editor for Redmond magazine and director of enterprise technology for ComponentSource. He specializes in development, integration services and network/Internet administration. Send questions or your favorite scripts to [email protected].