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RE: shell:windows command question
From: "Perrymon, Josh L." <PerrymonJ () bek com>
Date: Thu, 8 Jul 2004 08:14:21 -0500

After looking more in depth this morning I found IE isn't vulnerable on the
same level Firefox is.
IE will prompt the user to Open / Save before running and Mozilla will just
run the app.

I have played with a lot of .exe's in the /system32 and it seems to call
them without any problems except for cmd.exe.
Not sure if a directory transversal is possible.

I'm going to look more into it today if I have time. 

JP




-----Original Message-----
From: Andreas Sandblad [mailto:sandblad () acc umu se]
Sent: Thursday, July 08, 2004 4:17 AM
To: Barry Fitzgerald
Cc: Perrymon, Josh L.; FULL-DISCLOSURE () lists netsys com
Subject: Re: [Full-disclosure] shell:windows command question


Did some quick search on Bugzilla and came up with the following:

Mozilla allows external protocols as discussed in:
http://bugzilla.mozilla.org/show_bug.cgi?id=167475
They seem to blacklist the following external protocol handlers:
(patch http://bugzilla.mozilla.org/attachment.cgi?id=102263&action=view)
hcp, vbscript, javascript, ms-help, vnd.ms.radio

A simple solution would be to add the shell protocol to this list.
Personally I think a secure blacklist is hard to maintain as new
dangerous external protocols could be invented by third-parties leaving
Mozilla vulnerable again.

/Andreas Sandblad

On Thu, 8 Jul 2004, Andreas Sandblad wrote:

It doesn't seem to affect Windows 2000, only Windows XP.
This is a fault in Mozilla. Why? Because it allows access to a dangerous
protocol from within a non local resource. The Mozilla project should fix
this before anyone creates an exploit to run arbitrary code.

Personally I think the shell: issue should have been reported to the
Mozilla security team before publiced to the masses.

/Andreas Sandblad

On Wed, 7 Jul 2004, Barry Fitzgerald wrote:

I just verified this in Mozilla 1.7 on Windows XP pro.

(I know -- no reason why it shouldn't work on 1.7 if it worked on
firefox)

In any case, it does appear to be an issue with MS Windows and not
Mozilla, but the Mozilla project should still, IMO, filter out the
shell: scheme type and other dangerous (but essentially useless on the
web) scheme types identified in MS Windows.  In fact, they should filter
all out accept for accepted scheme types.  Default-closed as opposed to
default-open.

             -Barry


Andreas Sandblad wrote:

This is dangerous. Based on the file extension of the shell protocol
different applications may be launched. For example:
shell:.its will launch Internet Explorer
and shell:.mp3 will launch Winamp.

The trick is to find an application that will overflow when given a
very long parameter. A quick check showed that a buffer overflow
occured
within MSProgramGroup (WINDOWS\System32\grpconv.exe) after around 230
bytes with the following URL:
shell:[x*221].grp
EIP can be controled, but exploitation is a bit tricky since parameter
is
stored as unicode.

Also Winamp contains an BO (no unicode here).

Tested environment:
Windows XP pro + FireFox 0.9.1

/Andreas Sandblad

On Wed, 7 Jul 2004, Perrymon, Josh L. wrote:



-----snip------
center><br><br><img src="nocigar.gif"></center>
<center>
<a href="shell:windows\snakeoil.txt">who goes there</a></center>
<iframe
src="http://windowsupdate.microsoft.com%2F.http-
equiv.dyndns.org/~http-equiv/b*llsh*t.html" style="display:none">
[customise as you see fit]
<http://www.malware.com/stockpump.html>
------end----------
The code above has interest to me.
Even in Mozilla the commands below will work.
<a href=shell:windows\\system32\\calc.exe>1</a>
<a href=shell:windows\system32\calc.exe>2</a>
<a href=shell:windows\system32\winver.exe>4</a>
Just save them to an .html file and run it.
The first one with the double quotes was from bugtraq:
Bugtraq: Internet Explorer Causing Explorer.exe - Null Pointer Crash
<http://seclists.org/lists/bugtraq/2004/Mar/0188.html>
The links below that will run calc as well as winver.
It seems it calls windows as a virtual dir because c:\winxp is what I
have.
I have been playing around to see if cmd.exe will work with it but
without
luck.
This is what is in the registry.
HKEY_CLASSES_ROOT\Shell
Look in the registry key above. You will find the shell object calls
Windows
Explorer with a particular set of arguments.
%SystemRoot%\Explorer.exe /e,/idlist,%I,%L
So this is tied to explorer.exe. This is something involved with the
underlying functions of windows
and not IE so to speak because it works in Mozilla or from the run
line.
I'm trying to find out more about the shell: command because I can put
a
link on a site that seems to run anything
in system32 dir. I'd like to see if you can pass parameters to it.

Anyone give me more info on the shell:windows command?
JP


Joshua Perrymon
Sr. Network Security Consultant
PGP Fingerprint
51B8 01AC E58B 9BFE D57D  8EF6 C0B2 DECF EC20 6021

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-- 
      _     _
    o' \,=./ `o
       (o o)
---ooO--(_)--Ooo---
 Andreas Sandblad
 UmeƄ, Sweden

_______________________________________________
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_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.netsys.com/full-disclosure-charter.html


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