Microsoft Site Server Commerce Edition Lets Remote Users With Valid NT Accounts Upload and Then Execute ASP Scripts on the Server or Consume Disk Space on the Server
SecurityTracker Alert ID: 1003419|
SecurityTracker URL: http://securitytracker.com/id/1003419
(Links to External Site)
Date: Feb 1 2002
Denial of service via network, Execution of arbitrary code via network|
Exploit Included: Yes |
Version(s): 3.0 SP4 Commerce Edition|
rfp.labs reported a vulnerability in Microsoft Site Server's content publishing feature. A remote user with a valid NT account can upload and then execute arbitrary ASP code on the server or can consume disk space on the server to create a denial of service condition on the server.|
It is reported that a remote user with a valid NT account can use the forms provided at /SiteServer/Publishing/ to upload a file via the 'cphost.dll' module.
A remote user can supply a TargetURL with a filename prepended with the '../' string and a TargetURL of '/Sites/Publishing/Users/' to upload an executable script file to the /Sites/Publishing directory, which apparently has scripting permissions. Then, the remote user can have the server execute the uploaded script.
A demonstration exploit script is provided in the Source Message.
A remote user can also upload a large file with a TargetURL that is more than 250 characters to cause the upload operation to abort in mid-process. This will leave a temporary file written to a random directory in the c:\temp directory. If this operation is repeated, disk space can be consumed to create a denial of service condition.
A remote user with a valid NT account can consume disk space on the server and possibly create a denial of service condition. A remote user with a valid NT account can upload and execute arbitrary ASP scripts on the server.|
No solution was available at the time of this entry.|
The author of the report recommends disabling access to cphost.dll or removing the entire publishing system as a solution.
The author of the report also recommends that users install Site Server SP4 (if not already installed). The install order for SS 3.0 SP4 is reportedly *before* NT SP6a, so be sure to reapply SP6a afterwards.
Vendor URL: www.microsoft.com/siteserver/ (Links to External Site)
Access control error, Exception handling error, Input validation error|
|Underlying OS: Windows (NT), Windows (2000)|
|Underlying OS Comments: Tested on Windows NT4 SP5; Windows 2000 may or may not be affected|
Source Message Contents
Subject: [VulnWatch] RFP2201: MS Site Server Evilness|
-----/ RFP2201 /-------------------------------/ rfp.labs / wiretrip /----
MS Site Server Evilness
Security considerations to keep in mind when using Site Server 3.0
-----------------------------------------/ shimmer / email@example.com
------------------------------------/ rain forest puppy / firstname.lastname@example.org
Table of contents:
-/ 1 / Standard advisory information
-/ 2 / What this is all about
-/ 3 / Site Server 3.0
-/ 4 / Site Server 3.0, Commerce Edition
-/ 5 / Site Server 3.0, Commerce Edition + updates
-/ 6 / Conclusion
Disclaimer: no one is forcing you to read this; stop if you don't want to.
-/ 1 / Standard advisory information /------------------------------------
Software package: MS Site Server (regular + Commerce Edition)
Vendor homepage: www.microsoft.com/siteserver/
Version tested: 3.0
Platforms: Windows NT
Vulnerability type: Various (info exposure to file uploading)
Prior problems: See text
Current version: 3.0 SP4
NOTE: The vendor was not given this advisory prior to release due to the
fact that the solutions are based on known, published administrative best
practices and year-old patches. The recommended best practices herein
are generally covered in the MS IIS lockdown guide (I would supply the URL
but I have found the Microsoft Security site too difficult to navigate as
of late, and was unable to find the new resting place of this document).
-/ 2 / What this is all about /-------------------------------------------
First off, it's been a little over a year since my last official advisory.
I figured it's definately past time to release some new documents. So...
here it is.
I've always meant to take a peek into Site Server, to see if anything evil
was inside. Unfortunately, my MSDN subscription only included Site Server
3.0, Commerce Edition. To install that, you need to first install the
regular Site Server 3.0, which is not included with MSDN (that I saw). So
I never was able to get my hands on a copy of the regular 3.0 version to
take a peek at. That was around a year ago, maybe more.
Fast forward to last week, Shimmer, a fellow security buff, passed along
a copy of Site Server 3.0 and mentioned that I should look at it. Happy
to finally get a chance, I threw it on my poor overly-abused NT4 install
(which exists to test NT/IIS exploits mostly), and went to town. It
didn't take long to start coming across 'uncool' stuff.
Basically what I did was install the regular Site Server 3.0 and look
for bugs. I then upgraded to Commerce edition and looked for additional
bugs. Then I updated to the latest NT & site Server service packs, and
checked to see if they were still present. So 3 installations, each
having it's own section.
Just to state up front, we have no idea if these bugs exist on the Win2K
platform, or in Site Server 2000. Perhaps a subject for a later date.
And yes, Site Server 3.0 prior to Site Server SP4 (not to be confused with
NT SP4) is known to have security bugs--so if you haven't upgraded to SP4
yet, this article will give you several reasons to do so.
-/ 3 / Site Server 3.0 /--------------------------------------------------
Tested platform was Site Server 3.0 installed on NT4 SP5 machine.
In the example URLs, 'solce.rfp.labs' is the vulnerable server.
Some vulnerabilities are already known for this version of Site
Server. In particular, MS KB 1231656 details 6 separate viewcode.asp
pages included in the samples directory. This is documented as
There are other bugs, but they apply to Site Server 3.0, Commerce
Edition (see section 4, below).
Onto the bugs....
--/ a / LDAP_Anonymous account w/ default password
The installation of Site Server 3.0 includes the creation of a
LDAP_Anonymous user account, which is used by the included LDAP service.
Unfortunately the password for this account is set to 'LdapPassword_1'.
This password is also hardcoded into two system DLLs as well:
The account is added to the 'Guests' group, and is given the 'Log on
locally' privilege. Shimmer actually ran across this during his own
hack-fest. He also noted that the system appears to meticuously clean
up after this particular user account...as in, erase left over profile
files and such--basically, the system removes all traces that this user
account was used to log in.
The risks at this point are moderate: someone can use this account to
log into the machine and otherwise access system resources (but with
few actual privileges). However we will build upon this.
I would like to note that this is actually a known bug to Microsoft,
and is discussed in MSKBQ248840. It just hasn't surfaced in the
Systems that have (or had in the past) Site Server 3.0 installed, without
having been upgraded to Site Server SP4, will have this vulnerability.
Solution: upgrade to Site Server SP4.
--/ b / Information leakage and more via administrative pages
There are a host of administrative pages in the /SiteServer/Admin/
virtual directory. Normally they require a valid user login to
access; fortunately, we just so happen to know that the LDAP_Anonymous
account is available (and it works). So onto the info leaks...
This page gives a list of installed Site Server components. Fortunately
the LDAP_Anonymous account doesn't have privileges to enumerate the IIS
components as well. View the source...the info is stashed in META tags.
Displays known domains of which that server is involved. You'll need
IE to run the ActiveX, or view the data passed as parameters in the HTML
Displays a list of installed ODBC drivers, which then leads to:
Displays all DSNs configured for selected ODBC driver (from driver.asp)
Create, modify, and potentially delete LDAP users and groups. Can add
arbitrary users, and put them in arbitrary groups (including Admin
Group). Note: this is separate from Windows NT user/groups, and is
limited to within the LDAP realm, and thus the online web apps.
>From here, LDAP_Anonymous can view current search catalog configs. Not
much value in that tho.
These all expose various LDAP service and backend configuration
The impact varies according to what information is leaked, but none of it
would likely lead to a system compromise directly.
Solution: deny access to the /SiteServer/Admin/ directory by auauthorized
sources and users.
--/ c / Information leakage via _mem_bin pages
The Site Server installation places a few ASPs and DLLs in the _mem_bin
directory in the \wwwroot\. Two of the three DLLs require privileges not
granted by LDAP_Anonymous. The only ASP pages of interest:
Displays the default AUO (LDAP) schema, including host and port. If you
changed the port of the LDAP service, this would expose the new port.
Will give the password reminder for any user requested (but username must
be known). The password reminders are stored in the LDAP database, and
only for LDAP users (this is unrelated to NT user accounts).
Vulnerability lies in the attacker deriving an obvious password from
password reminder clues (or, maybe users are silly enough to put their
password as their password reminder). But considering that the
LDAP_Anonymous user can add/modify/view user data (via the
UserManager.asp script, above), this is not really anything special.
The overall impact of both of these are minimal.
Solution: you can probably live without both pages, so perhaps removing
them would suffice.
--/ d / Cross-site scripting in various files
Many of the ASP pages appear vulnerable to CSS, but here are two specific
ones (URLS are wrapped):
They do require a valid login, so this greatly minimizes exploitability.
--/ e / Anonymous LDAP access
Site Server installs an LDAP service used to house user data for the
local web site subscription database. The LDAP service runs on port
1002. Basically, by firing up an LDAP client/browser (I used Softerra's
LDAP Browser 2.1), it's possible to log in anonymously (essentially
what the LDAP_Anonymous account is meant for!)
While this is read-only access, the concern is that by browsing
ou=Members (probably of the default o=Microsoft), all of the indicated
members (cn=xxx) have a plain-text 'userPassword' attribute. Thus, an
anonymous LDAP browser can access the password of every user in the LDAP
Solution: do not allow access to port 1002 by anyone other than the
web server(s). Firewall is good, yah?
--/ f / User publishing of files
Back in mid-1999 Mnemonix posted an advisory that showed how Site Server
2.0 was vulnerable to people uploading files to the /user/ virtual
directory--which was given write access by default. The problem was
that an anonymous user could use a PUT request to upload a malicious
ASP file, and then have it ran by requesting it normally. More info
under BID 1811.
Well, in 3.0 things were improved. The Virtual directory was moved
to /Sites/Publishing/Users/. A valid NT user account is required to
upload (more on this in a bit). While the .../Users/ directory and
everything below is given write permissions, it is not given any type
of file browsing or script permissions--so even if an attacker did
upload a malicious ASP page, it would not be ran (in fact, it would
come back with a 403/Forbidden error page).
So at this point anyone with a valid user account can upload non-
executable content. Enter the LDAP_Anonymous account once again.
Using this account, it's possible to upload large files in an effort
to consume disk space, leading to a potential DoS. The virtual
directory is mapped to the Site Server install directory, which defaults
to C:\Microsoft Site Server\Sites\ ... so it's possible that the attack
could fill the system drive.
Solution: remove write access from specified directories.
--/ g / Content publishing (cphost.dll) issues
Besides using a PUT command to upload a file, a remote user can use the
forms provided at /SiteServer/Publishing/ to upload a file via a HTTP
POST to /scripts/cphost.dll, which was added on installation (there are
other versions of cphost.dll as well; this one is coded to specifically
jive with Site Server's way of doing things).
The intended functionality of cphost.dll doesn't provide anything beyond
what was described in section [f] (above). It allows a user (with valid
NT account credentials...a la LDAP_Anonymous) to upload files to the
/Sites/Publishing/Users/... directory. The content deployment page also
makes reference to uploading a file to a 'Content Deployment project
directory', as well as uploading a server side component to be
installed. We did not really dig into these avenues, but we assume them
to be as equally (or more so) vulnerable as the one we are describing.
The upload form takes two parameters: the my_file parameter which
contains the file to be uploaded, and the TargetURL parameter which
specifies the final location of the uploaded file(s). The TargetURL
must be in an IIS-configured writable directory (which is separate from
the NTFS write ACLs on the filesystem). Basically, this means that
cphost.dll will not place files in anything but /Sites/Publishing/Users/
It does allow the user to make subdirectories, and the typical place to
put user 'LDAP_Anonymous' files is
/Sites/Publishing/Users/Solce/ldap_anonymous/ (keep in mind that Solce
is the name of the server). While this is the default location for user
LDAP_Anonymous's files, they can techincally be put anywhere under
/Sites/Publishing/Users/. Directory browsing is not enabled, so you
can't view files that are already uploaded (or a gain a list of
So anyways, all of this has a point. There are two bugs in cphost.dll.
First, if you give cphost.dll a TargetURL that's over around 250
characters, it will abort mid-operation. Specifically, cphost.dll
temporarily writes files (as they are being uploaded) to a random
directory in C:\temp--this location is hardcoded into the DLL. Normally,
once the files are uploaded (and thus written out), cphost.dll will then
move them to the final resting place specified by TargetURL. However,
if the TargetURL is large enough, the move operation will fail, leaving
the files forever in C:\temp taking up space. So yes, another space-
hogging denial of service attack...this time it is hardcoded to the C:\
But DoS attacks are lame (hear me kids? LAME!) Fortunately I did
mention one more bug in cphost.dll, and this one is more fun (or scary,
pending your point of view).
Like any good researcher, I played with using '..' types of tricks in
the TargetURL, including using Unicode and other fun stuff in order
to see if I could get cphost.dll to put files lower than the .../Users/
directory (/Sites/Publishing/ has script execute permissions, unlike
/Sites/Publishing/Users/*). However no tricks yeild anything usable
with TargetURL. So I took the road-less-travelled...
It turns out that modifying the filename disposition parameter of the
multipart POST request is just enough to put an uploaded file one
directory higher. So by specifying a filename of '../test.asp', and a
TargetURL of '/Sites/Publishing/Users/' (which is writable and thus
valid to cphost.dll), the end result is the uploaded test.asp being
placed at /Sites/Publishing/test.asp, WHICH HAS SCRIPTING PERMISSIONS.
To exploit this you will need the capability of doing NTLM
authentication and providing an arbitrary multipart POST data body
(both of which are featured in upcoming libwhisker versions ;)
An example content body (with the obvious content boundary):
Content-Disposition: form-data; name="my_file"; filename="../test.asp"
Does it work?
<% Response.Write("Yes!") %>
Content-Disposition: form-data; name="TargetURL"
This resulted in the indicated file contents being saved to the URL
mentioned above, which then, when requested, would print "Yes!",
indicating it was parsed through the ASP parser. This allows arbitrary
ASP execution, which can then further be used to compromise the system,
read databases, etc.
Solution: at this point in time, disable access to cphost.dll, and
probably remove the entire publishing system in general.
-/ 4 / Site Server 3.0, Commerce Edition /--------------------------------
After I was all done poking at the regular Site Server 3.0, I decided to
install Site Server 3.0, Commerce Edition (which requires Site Server 3.0
to already be installed). Basically I wanted to see if any new bugs
where added, and if any of the above bugs were magically fixed.
Site Server 3.0 Commerce does have a history of two bugs:
- BID 994: code wizards generate code that does not validate user data
- BID 256: /AdSamples/config/site.csc contains SQL user/pass info
Well, in general Commerce edition does add a few new extra server-side
components to use in scripts...nothing really public facing. The 'Ad'
component is the biggest one to mention, installing both the /AdSamples/
and /AdManager/ directory. Access to /AdManger/ requires proper NT
account authentication, and LDAP_Anonymous does *not* work.
--/ a / Probable SQL tampering in sample sites
I reviewed the sample sites found in /clocktower/, /vc30/, /mspress30/,
and /market/. My general theory is that these were generated by the
code wizards metioned in BID 994, as none of them validate user parameters
before sticking them into SQL queries. Since Site Server required MS
SQL for a backend (and MS SQL allows the piggy-backing of SQL queries and
other SQL injection tricks), it seems possible that someone could use the
samples to play around in the DB--but they will be limited to whatever
sample user context and database that was specified during installation
(which could be the master DB under 'sa' privs, or a special garbage DB
with a user account created just for it). My odds are with the fact that
the sample DSN created during install will have more permissions than
should be warranted to a sample application.
Solution: yank all the sample sites, and remove the sample DSN(s) created.
You don't need sample apps on production servers. Everyone should know
that by now.
--/ b / Changes in prior bugs
The only change after installing Commerce addition was that the following
page (which displayed installed ODBC drivers) didn't function anymore:
That might be a glitch in my server config, but oh well. Everything else
was confirmed to still be present.
-/ 5 / Site Server 3.0, Commerce Edition + updates /----------------------
So now the fun part. I took the vulnerable server and installed SP6,
the IIS security rollup, and Site Server SP4. Many of these bugs may have
been (silently) fixed, so I figured I'd update and see what's still
vulnerable, and what's still exploitable.
--/ a / Bye-bye to old bugs
The password on the LDAP_Anonymous account was changed. This greatly
affects the overall exploitability of the other bugs, since a valid NT
account is required to access almost all of the web scripts. According
to MSKBQ248840, the LDAP_Anonymous password is a new random string
generated every time the LDAP service starts up. Looking at the code in
\winnt\system32\inetsrv\dscomobj.dll this is true, but it's done in
an odd manner. Basically a 10 character password is generated using
the SSLGenerateRandomBits() function in schannel.dll, or using rand()
(seeded with time()) if schannel.dll is not available. The 10 character
password is composed of 64 possible characters (A-Z, a-z, 0-9, _, %,
and hex 0x16). If the "HKLM\SYSTEM\CurrentControlSet\Services\LDAPSVC
\Parameters\PasswordPolicy" registry key is defined, then more password
mangling takes place; otherwise, the string 'Ab&1' is prepended to the
10 random characters, making a final 14 character string.
But now the weird part: instead of updating/replacing the old password
with the new password, the service instead deletes the LDAP_Anonymous
account, and recreates it with the new password. When deleting the
the account, the service does not remove the old account SID from the list
of users allowed in the "Log on locally" privilege; after a few system
reboots and service restarts, you'll have a long list of "Account Removed"
entries. Also since the SID of the account keeps changing, it's hard
to maintain any local filesystem ACLs to limit local access by the
LDAP_Anonymous account...not to mention if you audit user and group
management functions, you'll be swamped with entries detailing the
deletion and addition process (over 6 entries ever time the service
Of course, all of that is basically an inconvenience. However, there is
something interesting to note: using a null session netbios query, it's
possible to get the 'password last changed' value of the LDAP_Anonymous
account. Now, systems that lack schannel.dll (do any really exist?) fall
back to a rand() using srand(time()). This means that on systems without
schannel.dll, a null netbios session will indicate the approximate time
the password was created, which could then be brute-forced with feasible
effort by seeding the random function with times just prior to the
indicated password creation time, and trying the resulting password.
This vulnerability is very limited tho, since it requires access to port
139 and the absence of schannel.dll. But it's interesting none-the-less.
--/ b / Bugs that didn't leave
The LDAP service still allows anonymous browsing.
All of the administrative info-leaking URLs, _mem_bin scripts, and CSS
pages still work when used with a valid NT account (we don't have the
password for the LDAP_Anonymous account anymore, but normal domain
accounts will still expose the information).
The cphost.dll upload script still allows a valid NT user to upload
files, and still is vulnerable to the evil multipart request that puts
ASP pages into /Sites/Publishing.
--/ c / Hello to new bugs
Well, the new server had Site Server SP4, then NT Server SP6a, followed
by the IIS security rollup installed (in that order). According to
history, the viewcode.asp bug should have been fixed. However, I
am still able to view the source of arbitrary ASP pages (URL wrapped):
Looking at the source for viewcode.asp (via viewcode.asp ;) it appears
that it's possible to view the source of any page *except* pages in
a directory named /secure/. The script is also limited to files contained
in IIS virtual directories...it doesn't appear that '..' tricks will work.
But source code disclosure is still not cool....
-/ 6 / Conclusion /------------------------------------------------------
So there you have it--nothing earth-shattering, but enough bad stuff that
Site Server admins should be made aware of. If you haven't installed
Site Server SP4 yet, you really need to. The install order for SS3.0 SP4
places it *before* NT SP6(a), so make sure to reapply SP6a afterwards
(and then the IIS security rollup!).
It only takes one known NT account login to exploit these bugs over port
80, so this is still a problem in internal/intranet settings. The known
password on the LDAP_Anonymous account just made it easy for a random
attacker who didn't have prior knowledge of a NT user account to still
exploit the problems.
-/ acks /----------------------------------------------------------------
Special thanks to shimmer for working with me on this
-----/ RFP2201 /-----------/ rfp.labs / wiretrip / email@example.com /----
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