From: Roy Stapleton (roy@stapleton.biz)
Date: Thu Jan 20 2005 - 19:46:54 EST
I have tried the sethc.exe one, the 'at' command scheduler technique and
the 'c:\program' technique.
The OS I used was windows XP pro sp2. I logged in as a domain user with
no added rights, i.e. only local user access to the machine.
There is no write access in the c:\ or c:\windows\system32 folder, so
the sethc.exe technique fell at this hurdle, default rights on these
folders are users: read & execute and list (this folder, subfolders and
files), create folders (this folder and subfolders), create files
(subfolders only).
For the same reasons, the c:\program exploit failed as well.
The domain user does not have the privilege to create schedules with the
at command, so this failed as well.
The problem seen below does exist on XP. It may be (pardon the
fuzziness here) to do with caching load images of executable files and
prefetch stores. If you look in the C:\WINDOWS\Prefetch directory you
will see all the recently loaded executable files stored in a prefetch
format.
This may be why the original loaded when BSK tried the sethc.exe
technique in BSK's email.
For the below, I checked these on a machine I had local admin access on.
XP also watches files in the system32 directory. If you browse there
and rename the sethc.exe to something else and then refresh the screen,
you will see XP restore the sethc.exe file after a few seconds.
If you open a dos prompt and (make a backup of the sethc.exe file
warning here) copy cmd.exe to sethc.exe, answering that yes, you do want
to overwrite the original, you will see the new sethc.exe in an explorer
window with a cmd.exe icon. Now, if you delete that, windows will
restore sethc.exe but with a cmd.exe icon (note the file sizes). When
done this way, pressing shift 5 times will indeed open a cmd prompt.
This subject does interest me greatly, if you know of any techniques
that will escalate privileges on an XP machine I would like to know
them.
Thanks
Roy
-----Original Message-----
From: BSK [mailto:bishan4u@yahoo.co.uk]
Sent: 20 January 2005 11:13
To: miguel.dilaj@pharma.novartis.com; pen-test@securityfocus.com
Subject: Re: priviledge escalation techniques
> That's really strange. It works in WinXP.
> Perhaps there was a change in functionality (for
> bad!) from Win2K to XP?
> The only possibility I can imagine is either:
> a) something blocks launching interactive programs
> before logon in 2K, but
> not in XP
> b) 2K is checking that sethc.exe is valid before
> launching it, and XP is
> not doing that check (I don't really think that this
> is the case, but...)
>
> Do you have any XP box to test?? I'll try to get
> hold of a 2K as well.
I couldn't try on a XP box, but tried on a windows
2000 server. It behaves very differently here, after
the replacement of sethc.exe with cmd.exe:
1. before logging in, pressing 'shift' 5 times,
invokes sethc.exe but the original one, which in fact
doesn't exist in system32 directory, atleast with same
name. I think windows regenerated that file but with
some other name.
2. if I press 'shift' 5 times after logging in,
nothing appears, neither original sethc.exe nor the
replaced sethc.exe
Any clues?
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