Security Hole in Unix / Linux Systems

[Robert A . Klahn]

Greetings:

One thing that I have noticed missing in the media reports about this 
exploit is the answer to the question "So, what should I do?"

For a Linux system, the answer is most likely "nothing". I dont know of 
any distribution that uses CDE, at least by default. Mostly, in the Linux 
world, we have "moved past" CDE with Gnome and KDE.

For other U*IXes, the answer is a little bit more complex. Solaris, AIX, 
and HP/UX all use CDE, and for all recent versions, by default.

So, what to do, for these other U*IXes? Consider if you need to run dtspcd 
at all. Its purpose is to permit the running of applications on your 
server, from a remote client. Useful, perhaps. Risky, clearly. How does 
one turn dtspcd off? Easy, comment out this (or a similar looking line) 
from /etc/inetd.conf:

dtspc stream tcp nowait root /usr/dt/bin/dtspcd /usr/dt/bin/dtspcd

Save the file, and restart the inetd process by sending it the SIGHUP 
signal. Do a "netstat" to verify that port 6112 is not open. The actual 
netstat syntax varies from U*IX to U*IX, so do a man if you are unsure.

If you really need to be running dtspcd, you should block port 6112 at 
your firewall, and if you really need to run dtspcd, you really should 
have a firewall. You should also really be running dtspcd under TCP 
Wrappers, or something similar, on top of blocking the port at your 
firewall. If anyone is in this situation, let me know, and I can go into 
more depth. But, as we are now at least two times removed from the topic 
of the list (we are now talking about non-Linux systems that knowingly 
want to run something so risky), I will not take up any more of your time 
on the topic.

Bob.

On 2002.01.16 09:43 John Mosier wrote:
> 
>> CERT: EXPLOIT CIRCULATING FOR CDE HOLE
>> Posted January 15, 2002 05:32 Pacific Time
>> HACKERS ARE ACTIVELY exploiting a known vulnerability in Sun 
>> Microsystems Inc.'s Solaris version of the Unix operating system, 
>> security experts said late Monday, urging administrators to check if 
>> their system is vulnerable.
> 
>> The U.S.-government funded Computer Emergency Response 
>> Team/Coordination Center (CERT/CC) at Carnegie Mellon University in 
>> Pittsburgh said in an advisory that it had received "credible reports" 
>> of an exploit for Solaris systems. An exploit is a software tool that 
>> can be used to break into computer systems and that is often used by 
>> hackers.
>> The exploit takes advantage of a buffer overflow vulnerability that was 
>> first discovered in March 1999. The flaw in a library function used by 
>> the CDE (Common Desktop Environment) could allow an attacker to take 
>> full control over the system, CERT/CC said. CDE is a graphical user 
>> interface that is typically installed by default on Unix systems.
>> CDE is "a fairly widespread product on Unix platforms" and is included 
>> in products from Sun Microsystems Inc., IBM Corp., Hewlett-Packard Co. 
>> and Compaq Computer Corp., according to Art Manion, an Internet 
>> security analyst with CERT/CC.
>> The CDE Subprocess Control Service (dtspcd) is a network daemon that 
>> accepts requests from remote clients to execute commands and launch 
>> programs remotely. The service does not perform adequate input 
>> validation, as a result of which a malicious client could manipulate 
>> data sent and cause a buffer overflow, according to CERT/CC.
> 
>> CERT/CC advises administrators to check if a system is configured to 
>> run dtspcd by looking for the entries "dtspc 6112/tcp" in 
>> "/etc/services" and "dtspc stream tcp nowait root /usr/dt/bin/dtspcd 
>> /usr/dt/bin/dtspcd" in "/etc/inetd.conf".
>> Many Unix and Linux flavors are vulnerable and many vendors have long 
>> issued patches to fix the problem. Any system that does not run dtspcd 
>> is not vulnerable to this problem.
>> For the full story: 
>> http://www.infoworld.com/articles/hn/xml/02/01/15/020115hncert.xml?0116weam
> 
> John Mosier, Excelco, Inc. NEW contact info: Free:  866 225-3605
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> 
-- 
Robert A. Klahn
rklahn@acm.org

"Hope has two beautiful daughters: Anger and Courage. Anger at the way
things are, and Courage to struggle to create things as they should be." -
St. Augustine