[rsbac] Fwd: [OT] rsync 2.5.6 security advisory
Amon Ott
ao at rsbac.org
Thu Dec 4 10:29:22 CET 2003
Hi!
Another example. The attacked rsync server was probably the exploited gentoo
rsync server.
Amon.
---------- Forwarded Message ----------
Subject: [OT] rsync 2.5.6 security advisory
Date: Donnerstag, 4. Dezember 2003 10:02
From: Fabian Uebersax <fabian.uebersax at tiscali.ch>
To: linux-kernel at vger.kernel.org
From http://rsync.samba.org/ :
December 4th 2003
Background
The rsync team has received evidence that a vulnerability in rsync was
recently used in combination with a Linux kernel vulnerability to compromise
the security of a public rsync server. While the forensic evidence we have is
incomplete, we have pieced together the most likely way that this attack was
conducted and we are releasing this advisory as a result of our
investigations to date.
Our conclusions are that:
* rsync version 2.5.6 contains a heap overflow vulnerability that can be
used to remotely run arbitrary code.
* While this heap overflow vulnerability could not be used by itself to
obtain root access on a rsync server, it could be used in combination with
the recently announced brk vulnerability in the Linux kernel to produce a
full remote compromise.
* The server that was compromised was using a non-default rsyncd.conf
option "use chroot = no". The use of this option made the attack on the
compromised server considerably easier. A successful attack is almost
certainly still possible without this option, but it would be much more
difficult.
Please note that this vulnerability only affects the use of rsync as a "rsync
server". To see if you are running a rsync server you should use the netstat
command to see if you are listening on TCP port 873. If you are not listening
on TCP port 873 then you are not running a rsync server.
New rsync release
In response we have released a new version of rsync, version 2.5.7. This is
based on the current stable 2.5.6 release with only the changes necessary to
prevent this heap overflow vulnerability. There are no new features in this
release.
We recommend that anyone running a rsync server take the following steps:
1. Update to rsync version 2.5.7 immediately.
2. If you are running a Linux kernel prior to version 2.4.23 then you
should upgrade your kernel immediately. Note that some distribution vendors
may have patched versions of the 2.4.x series kernel that fix the brk
vulnerability in versions before 2.4.23. Check with your vendor security site
to ensure that you are not vulnerable to the brk problem.
3. Review your /etc/rsyncd.conf configuration file. If you are using the
option "use chroot = no" then remove that line or change it to "use chroot =
yes". If you find that you need that option for your rsync service then you
should disable your rsync service until you have discussed a workaround with
the rsync maintainers on the rsync mailing list. The disabling of the chroot
option should not be needed for any normal rsync server.
The patches and full source for rsync version 2.5.7 are available from http://
rsync.samba.org/ and mirror sites. We expect that vendors will produce
updated packages for their distributions shortly.
Credits
The rsync team would like to thank the following individuals for their
assistance in investigating this vulnerability and producing this response:
* Timo Sirainen <tss.iki.fi>
* Mike Warfield <mhw.wittsend.com>
* Paul Russell <rusty.samba.org>
* Andrea Barisani <lcars.gentoo.org>
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-------------------------------------------------------
Amon.
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