Archive for category News

SpamAssassin 2010 bug

Posted by on Saturday, 2 January, 2010

From : https://secure.grepular.com/blog/index.php/2010/01/01/spamassassin-2010-bug/

I use SpamAssassin to filter the spam out of my incoming email. Last night I noticed that a legitimate email had a particularly high spam score. On further investigation I found that a rule named FH_DATE_PAST_20XX was triggering:

* 3.2 FH_DATE_PAST_20XX The date is grossly in the future

I checked the Date header of the email and it looked totally fine to me. It had just changed from the year 2009 to the year 2010. Could that be a coincidence? A quick look in /usr/share/spamassassin/72_active.cf turned up the rule:

header FH_DATE_PAST_20XX Date =~ /20[1-9][0-9]/ [if-unset: 2006]

Oops. That regex matches on any year between 2010 and 2099. I googled for the rule and came across this:

http://wiki.apache.org/spamassassin/Rules/FH_DATE_PAST_20XX

In the comments it mentioned the problem which I found: “Note: the current rule in 3.2 will start matching legitimate dates from 2010-01-01. See issue #5852.” Looking at issue 5852, the problem was first identified on 2008-Nov-05 and was “fixed” in CVS on 2009-Jun-30. I’m using the standard stable Debian package which doesn’t contain this fix yet so I had to stick the following in my local.cf file to apply a score of 0 to it:

score FH_DATE_PAST_20XX 0.0

I think a lot of systems will be experiencing false positives on their ham because of this at the moment. It is a particularly high scoring rule considering that the default threshold is 5.0.

As I understand it, rules aren’t distributed with SpamAssassin as of the next version (3.3) so hopefully problems like this wont happen in future. The “fix” which was supplied for this problem five months ago was to update the regex so it matches 2020-2099 instead.

You can read the thread I started about this issue on the SpamAssassin users list here. It’s the one started at “Fri, 01 Jan 2010 00:57:37 GMT” with the subject line “FH_DATE_PAST_20XX”


Chedder Bay Kernel Exploit

Posted by on Saturday, 18 July, 2009

Found at : http://www.jethrocarr.com/index.php?cms=blog:20090718

A new 0-day attack on the Linux kernel has just been released by Brad Spengler called the “Chedder Bay Exploit” which exploits a flaw in the Linux 2.6.30+ kernel.

This exploit is interesting, in that the code doesn’t look particularly broken, but when compiled the compiler optimisations causes the compiled code to have a security hole.

For more technical details on this exploit and further news, check the LWN.net article or use the CVE reference CVE-2009-1897.

From my quick review of the exploit, it appears the attack uses Pulseaudio to bypass Selinux security if it is enabled and then performs an attack against the /dev/net/tun device, allowing a standard user to gain root access.

Not having pulseaudio or the tun kernel module loaded should prevent this exploit from working, although I have not yet had sufficient time to test this since I received the alert announcement around 3am NZ time.

The exploit affects the 2.6.30+ kernel releases and also some of the test kernel 2.6.18 kernel releases by Redhat.

However, all production kernel releases for RHEL/CentOS do not appear to be vulnerable since the change that introduced the security exploit had not been backported yet.

In my tests on CentOS 5.3 with kernel 2.6.18-128.1.16.el5xen on i386/xen, I was unable to trigger the exploit.


Debian GNU/Linux 5.0 Update (RC2)

Posted by on Sunday, 28 June, 2009

——————————————-

The Debian Project                                 http://www.debian.org/
Debian GNU/Linux 5.0 updated                             press@debian.org
June 27th, 2009                  http://www.debian.org/News/2009/20090627
————————————————————————-

Debian GNU/Linux 5.0 updated

The Debian project is pleased to announce the second update of its stable
distribution Debian GNU/Linux 5.0 (codename “lenny”).  This update mainly
adds corrections for security problems to the stable release, along with
a few adjustment to serious problems.

Please note that this update does not constitute a new version of Debian
GNU/Linux 5.0 but only updates some of the packages included.  There is
no need to throw away 5.0 CDs or DVDs but only to update via an up-to-
date Debian mirror after an installation, to cause any out of date
packages to be updated.

Those who frequently install updates from security.debian.org won’t have
to update many packages and most updates from security.debian.org are
included in this update.

New CD and DVD images containing updated packages and the regular
installation media accompanied with the package archive respectively will
be available soon at the regular locations.

Upgrading to this revision online is usually done by pointing the
aptitude (or apt) package tool (see the sources.list(5) manual page) to
one of Debian’s many FTP or HTTP mirrors.  A comprehensive list of
mirrors is available at:

<http://www.debian.org/distrib/ftplist>