Re: [Full-disclosure] Flaw in Microsoft Domain Account-CachingAllows- Local Workstation Admins to Temporarily-EscalatePrivileges and Login as Cached- Domain Admin Accounts-(2010-M$-002)

From: Marsh Ray <marsh@extendedsubset.com>
To: Michael Bauer <ravenmsb@gmail.com>
Cc: Stefan Kanthak <stefan.kanthak@nexgo.de>,<full-disclosure@lists.grok.org.uk> <full-disclosure@lists.grok.org.uk>,<bugtraq@securityfocus.com> <bugtraq@securityfocus.com>,George Carlson <gcarlson@vccs.edu>
Subject: Re: [Full-disclosure] Flaw in Microsoft Domain Account-CachingAllows- Local Workstation Admins to Temporarily-EscalatePrivileges and Login as Cached- Domain Admin Accounts-(2010-M$-002)
Date:


On 12/13/2010 11:19 AM, Michael Bauer wrote:
> An administrator is very different there are many levels of
> administrative control in windows to say an admin is an admin is
> absurd.

I disagree. There's only one level of pwned.

> There is a big difference between a local admin and a domain
> admin.

Yes, local vs. network is sometimes a useful distinction.

But joining a machine to the domain gives it a bit more power to attack 
other stuff on the domain. And how many domain-joined systems do not 
also include Domain Admins as Local Admins?

> There are many types of admin in windows and all of them have
> different levels of permission.

I disagree.

> I would be very scared to have anyone
> taking care of any of my systems windows or NIX who thought an admin
> was an admin and root is root.

You ought to be scared anyway.
There's a new local exploit here every few days or weeks.

> Here is a reference showing the
> different SIDs for some common windows accounts.
> Http://support.microsoft.com/kb/24333
>
> If you take time to read it you will see there are numerous types of
> windows administrator all with different permissions.

I know MS set out to define all these different capabilities and so on. 
My impression is that much of that was suggested by Orange Book. But 
they supposedly obtained this Orange Book certification yet still 
installed notepad.exe as world-writable by default.

In practice, those distinctions rarely hold up under scrutiny. Remember 
"Guest User" vs "User" vs "Power User"? MS has greatly de-emphasized the 
utility of boundaries between privileges them in the OS over time, 
preferring instead to invent new ones that were more relevant to the 
times. Witnesseth the recent discussions about the elevation token and 
IE protected mode.

The best you can hope for is to maintain an effective boundary between 
normal users and root/admin. But usually as soon as you install a few 
off-the-shelf Windows or shareware apps, it's gone. Try this: install 
your favorite "productivity" app in a non-default directory, e.g. C:\, 
then look at the filesystem permissions on its executable folder (and 
everywhere it might load DLLs from). Then note that (just a wild guess) 
it probably runs some dll-preloader and system tray icon processes for 
everyone who logs in - even Admins.

Even on a pristine OS install, the next local escalation bug is just a 
matter of time, and that's just the published ones. The bad guys likely 
have plenty already.

If you're lucky, you might be able to maintain an effective security 
boundary between a local computer and the network. Don't waste your time 
trying to protect machines from users who have unsupervised physical 
access anyway.

- Marsh





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