Sender: sun-managers-relay () ra mcs anl gov
Date: Thu, 30 Apr 1998 12:00:53 +0200
From: anders () hmi de (Thomas Anders)
Followup-to: anders () hmi de (Thomas Anders)
Reply-To: anders () hmi de
X-Disclaimer: I only speak 4 myself - if at all
X-Mailer: Z-Mail (4.0.1 13Jan97)
To: sun-managers () ra mcs anl gov (Sun-Managers List)
Subject: SUMMARY/WARNING: AnswerBook2 DoS bug
already in December 1997 I discovered a serious bug in the AnswerBook2
server dwhttpd/3.1a4 that ships with Solaris 2.6 (server edition). With
a simple socket connection to the AB2 port (default: 8888), *anyone* on
the network with access to that port (default: everybody, see below) can
bring the server to spin and deny further responses:
- --- snip ---
HTTP/1.0 500 Server Error
Server: dwhttpd/3.1a4 (Inso; sun5)
The server currently lacks the resources needed to handle your request.
Please try again later.
- --- snap ---
The affected dwhttpd process will eat one cpu, with possible impact on
other services. (MP machines will still have some cpus available.)
I reported this to Sun who filed a bug report
HTTP 1.0 HEAD request brings the dwhttpd to spin
and assigned priority "fix within 3 months". AB2 technology is a
third-party product, so Sun filed a bug with Inso who provides
dwhttpd as part of their DynaWeb toolkit. Five months later (!)
now they finally claim: it's fixed in dwhttpd/4.0 which will ship
with Solaris 2.7. Still no patch for the existing AB2 package!
What you can do:
Q: Do I run dwhttpd?
A: Check for packages SUNWab2r, SUNWab2s and SUNWab2u.
Check if dwhttpd is invoked at system startup (/etc/rc2.d/S96ab2mgr)
Check with "ps -ef | grep dwhttpd"
Q: Is my AB2 server really vulnerable?
A: If you don't believe it, check yourself - the source code for a
sample "AB2 DoS attack program" (that I gave Sun to reproduce the bug)
is included in the bug report (wow - Sun publishes exploit scripts!).
Q: I'm vulnerable - what can I do?
A: 1. The only real fix is "/etc/init.d/ab2mgr stop" (which is a DoS
2. Restrict the access to your AB2 server port to particular clients
(e.g. intranet only) by tcp-wrapper or firewall setup.
*** 3. Get nervous, call Sun, request a patch for this bug now. ***
I hope we can get Sun/Inso to produce a *patch* soon.
If there are any substantial news I will summarize again.
Thomas Anders <anders () hmi de>
Hahn-Meitner-Institut Berlin, Germany