--- Advisory RFP9907 ----------------------------- rfp.labs -----------
You, your servers, RDS, and thousands of script kiddies
..how to keep your website intact..
(Defending against RDS attacks)
------------------------------ rain forest puppy / rfpat_private ---
Table of contents:
- 1. Problem
- 2. Solutions
- 3. Situations
- 4. Detecting msadc.pl
- 5. Conclusion
- 6. Resources
-----------------------------------------------------------------------
Don't have time to read this? Then all you need to do is delete the
following file:
?:\Program Files\Common Files\System\Msadc\msadcs.dll
Quick and dirty RDS disablement. (If you need RDS, you better read on)
-----------------------------------------------------------------------
----[ 1. Problem
.gov, .mil, and even microsoft.com haven fallen lately to the
hands of website defacers. Turns out, it's all been because of RDS. Now,
sure, IIS 4.0 is pretty much exploitable right out of the box, but
Microsoft has released not one, not two, but *three* different patches,
plus re-released the same advisory numerous times. And it's still a
problem.
So we need education. There's a lot of speculation floating
around out there as to what and how you should fix yourself. Since I
wrote the exploit for RDS, and have researched it quite a bit, I'd like to
share my findings, in an effort to put this issue to rest.
The problem is basically Jet 3.5 allows calls to VBA's shell()
function, which lets you run shell commands (this was documented in
RFP9901: NT ODBC remote vulnerabilities, available at:
http://www.wiretrip.net/rfp/p/doc.asp?id=3&iface=2
). Now, IIS 4.0, by default, installs MDAC 1.5. This includes RDS, which
allows for remote access to ODBC components over the web, through one
particular .DLL located at /msadc/msadcs.dll (this is documented in
RFP9902: RDS/IIS vulnerability and exploit, available at:
http://www.wiretrip.net/rfp/p/doc.asp?id=1&iface=2
). So you see it's a two-part problem. There is also an additional third
element, where sample pages installed by various RDS SDK packages include
a sample component named VbBusObj, which allows you to bypass some of
Microsoft's recommended fixes (this is also documented in RFP9902).
We shall touch on all of these elements.
----[ 2. Solutions
The problem is that there's too many solutions, and there's many
different combinations of usages. I'll try to detail as many as possible.
Also, for simplicity I've mirrored all important binaries (i386 only) on
my website, just in case you can't get to www.microsoft.com, etc.
-Solution #1: move cmd.exe (ULG recommended fix)
http://www.aviary-mag.com/News/Powerful_Exploit/ULG_Fix/ulg_fix.html
I commend ULG for helping out, however this solution has a problem. True
that mdac.pl is hardcoded to use cmd.exe (or command.com for that matter).
However, I want it known that
CMD.EXE IS NOT REQUIRED FOR THE EXPLOIT TO WORK
I used it for shear compatibility. If you don't believe me, try it
yourself. Edit mdac.pl to not submit the 'cmd /c' string. You can still
supply any executable name (for example, 'rdisk'). Just remember, if you
don't use cmd.exe, then you can't use commands like 'copy', and features
such as file redirection ( ' > file.out'). These are only provided by
using cmd.exe.
Also note that moving cmd.exe/command.com is merely security through
obscurity. If the hacker finds where you put it, they can still use it.
And adjusting the permissions on it to disallow System access may break
applications. I would use this solution with extreme caution (considering
there are other patches, I would use those instead).
-Solution #2: upgrade from MDAC 1.5 to 2.0
MDAC 2.0 moves from Jet 3.5 to Jet 3.52. This is still vulnerable to the
VBA shell() attack (which is essential to the exploit), and does not
disable RDS by default. In fact, I believe it will reinstall RDS if you
removed it. Some notable things:
* default Jet engine becomes 3.52 (still vulnerable)
* allows custom handler support (to stop anonymous RDS usage)
* creates Microsoft.Jet.OLEDB.3.51* providers
Now, this solution, in it's default form, is not good. You minimally need
to enable the custom handler support. This is simply a registry key,
found at:
HKEY_LOCAL_MACHINE\Software\Microsoft\DataFactory\HandlerInfo\
Keyname: HandlerRequired
Value: DWORD:1 (safe) or 0 (unsafe)
It is recommended you change this to 1. This is also what is accomplished
by using the 'handsafe.exe/.reg' fix provided by Microsoft. You can get
this file from my website at:
http://www.wiretrip.net/rfp/bins/msadc/handsafe.exe
When ran, this file will produce another file named handsafe.rem. Rename
this to handsafe.reg, and then double-click to import it into the registry
(which will change the above mentioned key to a value of 1).
Now, while protected via remote RDS attack, you're still vulnerable to all
other forms of ODBC attack, which include trojan Excel, Word, and Access
files, other rogue applications, etc. This should be considered
insufficient.
Creation of the Microsoft.Jet.OLEDB.3.51* providers is important, and
I'll get back to this.
-Solution #3: upgrade from MDAC 1.5 to 2.1 (any level)
MDAC 2.1 moves from Jet 3.5 to Jet 4.0 engine, which is not exploitable.
However, there are compatibility issues, due to the differences between
3.5 and 4.0. Many people have avoided upgrading because of these
incompatibilites. Not to mention some stability issues with the earlier
2.1 line as well. Some notables:
* default Jet engine becomes 4.0 (not vulnerable)
* allows custom handler support (to stop anonymous RDS usage)
However, custom handlers are not turned on by default. You need to set
the above mentioned registry key (HandlerRequired) to a value of 1, either
by using regedit or the handsafe.exe/.reg fix.
-Solution #4: upgrade from MDAC 1.5 to 2.0 to 2.1
Now, if you were a good little admin, you should have kept up to date on
your installs, upgrading as you went along. If you did, you will have
succumbed to the full upgrade route. The same problems exist as do
upgrading straight to 2.1 (as mentioned above)--you still need to enable
the 'HandlerRequired' registry key. Also remember that 2.1 used Jet 4.0
(not vulnerable) as the default engine. However, since you breezed
through the 2.0 install, you have the Microsoft.Jet.OLEDB.3.51 providers.
This means applications (including RDS) have a hook to call the old
(exploitable) Jet 3.51 engine!
You should remove these old hooks/providers. One method is to remove the
following registry entries:
HKEY_CLASSES_ROOT\Microsoft.Jet.OLEDB.3.51
HKEY_CLASSES_ROOT\Microsoft.Jet.OLEDB.3.51Errors
However, you're still faced with compatibility issues of using the 4.0
engine. So this isn't the greatest solution.
-Solution #5: install JetCopkg.exe (MS99-030)
JetCopkg.exe is a modified Jet 3.5 engine that has safety features enabled
in it to prevent exploitation, referred to as 'sandbox' mode. This safety
feature is controlled by the following registry key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Jet\3.5\engines\SandboxMode
With the following values:
0 disabled
1 enable for Access, disable for everything else
2 disable for Access, enable for everything else (default)
3 enable for everything
(Note 1: 'xxx for Access' means for use with Microsoft Access program)
(Note 2: this is all explained in:
http://support.microsoft.com/support/kb/articles/q239/1/04.asp)
(Note 3: the default permissions on this key are insecure! You should
change 'Authenticated Users' to 'Read Only' for this key. For many
examples how the weakness of this key can cause problems, see a great
email by Eric Shultze, posted on my website at:
http://www.wiretrip.net/rfp/p/doc.asp?id=11&iface=2
)
A value of 2 or 3 will keep the exploits out. So, IMHO
THIS IS THE PROPER, RECOMMENDED SOLUTION
Since it's still the same Jet 3.5 engine, you should have no compatibility
problems. However, this does not close RDS. While you won't be
exploited, it means an attacker can still have remote anonymous access to
your datasources. Which means he can mess with your data, which still
isn't good. So you need to do something about RDS. I suggest either
disabling RDS (see below), or upgrading to MDAC 2.0 (however, upgrade to
MDAC 2.0 first, then JetCopkg). By upgrading to MDAC 2.0, you'll gain
handler control, where you can deny anonymous access.
-Solution #6: remove/disable RDS support
This is your best bet, when used in combination with JetCopkg (mentioned
above). If you can't install system-modifying packages (due to Y2K
lockdown, etc), you can at least cut off remote exploitation potential by
disabling RDS. You can do this the very crude and dirty way by deleting:
?:\Program Files\Common Files\System\Msadc\msadcs.dll
This is the .DLL that provides the RDS interface. However, it is much
more recommended that you take a few extra moments and clear it up right.
This includes:
* Remove the /msadc virtual directory mapping from IIS. To do this, open
up the Microsoft Management Console/Internet Service Manager.
Then:
* Go to 'Internet Information Server'
* Select the proper system
* Select 'Default Web Site'
* Select 'msadc'
* Either hit the 'Del' key, or click the delete icon
* Are you sure? Yes.
* Remove the following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\W3SVC
\Parameters\ADCLaunch
(Note: line is wrapped for clarity)
* Delete all files and subdirectories in:
?:\Program Files\Common Files\System\Msadc
----[ 3. Situations
-Situation #1: I need RDS support!
Ugh, sorry to hear that. But ok, this is doable. You need to at least
upgrade to MDAC 2.0. If you have backwards-compatibility issues, then
MDAC 2.0 with JetCopkg should do the job, otherwise shoot for MDAC 2.1.
Make sure you enable the 'HandlerRequired' registry key (explained
above). Also make sure you remove the RDS samples, if available (see
below). Microsoft also recommends disabling Anonymous Access for the
/msadc directory for the default web site under the MMC. Lastly, you need
to implement a custom handler. Information on doing such is available at:
http://www.microsoft.com/Data/ado/rds/custhand.htm
-Situation #2: I'm all locked down, except for those sample scripts...
VERY IMPORTANT
Using custom handlers is the only way to stop anonymous access to RDS
without disabling RDS entirely. However, if the RDS samples are installed
(found at:
?:\Program Files\Common Files\System\Msadc\Samples
) then an object included with the sample files (VbBusObj) can be used to
bypass the custom handlers! In fact, there is no reason at all this
should be on a production server, and should be removed. It's a two-step
process:
* Delete the following subdirectory (EVERYTHING in it):
?:\Progam Files\Comman Files\System\Msadc\Samples
* Remove the following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\W3SVC
\Parameters\ADCLaunch\VbBusObj.VbBusObjCls
That will remove the VbBusObj object, and prevent people from bypassing
your custom handlers.
----[ 4. Detecting msadc.pl
Detecting activity by msadc.pl version 1 and 2 isn't all that
hard. However, I'm assuming the exploit as it exists now--there are
modifications possible that will make detection harder. I'm only going to
focus on the exploit as I wrote it.
First off, the script will do a GET request to /msadc/msadcs.dll
on the target webserver. If it exists, it will proceed; otherwise, it
spits out an error message and exits. This initial GET request should be
logged in your webserver access logs, per the usual. Note that 'skilled
users' may change this to a HEAD or POST request, and may use some
obfuscation techniques on the URL (like hex-encoding). But it will still
be logged. The key is noticing msadcs.dll with no paramters (explained in
a second)...this means someone is looking, but not using (yet). As far as
RDS is concerned, no one should ever be just 'looking'. Valid users will
use it straight out. So calling msadcs.dll with no parameters should be
flagged as suspicious.
If msadcs.dll exists (determined by returning a particular
response), then it asks the user what command to run. By default,
msadc.pl will prepend 'cmd /c' or 'command /c', for compatibility. This
means it is dependant on cmd.exe or command.com. However, again, 'skilled
users' can modify the script to not require either.
Next the script actually starts making RDS queries. It does so
using POST requests to one of the following URLs:
Normal query:
/msadc/msadcs.dll/ActiveDataFactory.Query
VbBusObj to bypass custom handlers:
/msadc/msadcs.dll/VbBusObj.VbBusObjCls.GetRecordset
Query VbBusObj for NetBIOS name:
/msadc/msadcs.dll/VbBusObj.VbBusObjCls.GetMachineName
Now, if you are using RDS for legitimate purposes, then the
ActiveDataFactory.Query URL is normal. However, no one should be using
VbBusObj, so the other two URLs should be instantly flagged as an attack.
Remember that grep'ing your logs for 'VbBusObj' isn't going to do
it--'skilled users' can hex-encode the URL to read something like:
/%6Dsadc/%6Dsadcs.dll/V%62BusO%62j.V%62BusO%62jCls.GetRecordset
(this is just one example)
Notice how the string is now broken up. Therefore purely relying on a
'grep' to find problems may not be enough.
At this point, I want to also point out two other tidbits:
* the default msadc.pl script uses 'ACTIVEDATA' as the User-Agent. This
can serve as a flag--however, the normal RDS control also uses this tag as
the User-Agent, therefore it may not be possible to distinguish from
normal traffic.
* the default msadc.pl script uses '!ADM!ROX!YOUR!WORLD!' as the MIME
separator string. While this isn't logged anywhere, some IDSes
(like Dragon; www.securitywizards.com) use this to detect attacks on the
wire.
By default, the script tries to use local .MDB files found on the
server. If one is found, it will create a table named 'AZZ' within the
.MDB. It does not delete the table afterward, so you can check all .MDB
files for tables named 'AZZ'. However, version 2 of msadc.pl allows for a
different query type that may not create the 'AZZ' table, and may not even
use local .MDBs (UNC support).
----[ 5. Conclusion
Ok, yet another night where I go without sleep to type up an
advisory. I really need to stop this. The things I do for you people. ;)
The best indication that you've been attacked by RDS is that your website
reads something along the lines seen on my homepage, at:
http://www.wiretrip.net/rfp/
It's not that hard. Minimally, delete a file, and you're pretty safe.
Then you can rest assured you won't be the next defaced website on
Attrition.
Go forth and patch,
.rain.forest.puppy.
ps. as much as I try, I'm only human. This document may contain errors.
It's late, I'm tired, I want to expedite this, and a lot of it is from
memory. I apologize up front for any errors I may make.
----[ 6. Resources
- Office 97/Jet 3.5 update binary (i386)
http://www.wiretrip.net/rfp/bins/msadc/jetcopkg.exe
http://officeupdate.microsoft.com/isapi/gooffupd.asp
?TARGET=/downloaditems/JetCopkg.exe
- Microsoft Universal Data Access homepage
http://www.microsoft.com/data/
- MDAC 2.1.2.4202.3 (GA) (aka MDAC 2.1 sp2) update (i386)
http://www.wiretrip.net/rfp/bins/msadc/mdac_typ.exe
http://www.microsoft.com/data/download_21242023.htm
- MDAC 2.1.1.3711.11 (GA) (aka MDAC 2.1 sp1) hotfix
http://www.microsoft.com/data/download/jetODBC.exe
- MDAC 2.1 release manifest
http://www.microsoft.com/data/MDAC21info/MDAC21sp2manifest.htm
- MDAC 2.1 installation FAQ
http://www.microsoft.com/data/MDAC21info/MDACinstQ.htm
- Security Implications of RDS 1.5, IIS 3.0 or 4.0, and ODBC
http://support.microsoft.com/support/kb/articles/q184/3/75.asp
- Unauthorized ODBC Data Access with IIS and RDS (MS99-004)
http://www.microsoft.com/security/bulletins/ms98-004.asp
- Re-release of MS99-004 (MS99-025)
http://www.microsoft.com/security/bulletins/ms99-025.asp
- MS99-025 FAQ (best explanation of problem by Microsoft)
http://www.microsoft.com/security/bulletins/MS99-025faq.asp
- MS99-30: Patch available for Office ODBC Vulnerabilities
http://www.microsoft.com/security/bulletins/ms99-030.asp
- Jet Expression Can Execute Unsafe VBA Functions
http://support.microsoft.com/support/kb/articles/q239/1/04.asp
- Implementing Custom Handlers in RDS 2.0
http://www.microsoft.com/Data/ado/rds/custhand.htm
- Handsafe registry patch (enables handlers)
http://www.wiretrip.net/rfp/bins/msadc/handsafe.exe
http://www.microsoft.com/security/bulletins/handsafe.exe
- RFP9901: NT ODBC remote compromise
http://www.wiretrip.net/rfp/p/doc.asp?id=3&iface=2
- RFP9902: RDS/IIS 4.0 vulnerability and exploit
http://www.wiretrip.net/rfp/p/doc.asp?id=1&iface=2
- RDS exploit (msadc.pl v1 and v2)
http://www.wiretrip.net/rfp/p/doc.asp?id=16&iface=2
- ULG recommended fix on OSALL
http://www.aviary-mag.com/News/Powerful_Exploit/ULG_Fix/ulg_fix.html
- CERT blurb
http://www.cert.org/current/current_activity.html#0
- Attrition mirror of defaced websites (patch or you'll be on it!)
http://www.attrition.org/mirror/attrition/
--- rain forest puppy / rfpat_private ----------- ADM / wiretrip ---
Patch your system before flipper and fuqnut get to you...
--- Advisory RFP9907 ----------------------------- rfp.labs -----------
This archive was generated by hypermail 2b30 : Fri Apr 13 2001 - 15:09:33 PDT