mark :: blog
We always have a moose theme for Christmas. Tracy bought some small cute wood
moose decorations from John Lewis online this year for the tree. The John Lewis
Glasgow store had a bit of a moose theme too, with Christmas displays made up of
much larger wood versions of the decorative moose. The floor manager said they'd usually get
thrown away or sold to staff at the end of the event.
A moose is for life, not just for Christmas. Tracy managed to arrange to buy some
from the store to save them being thrown away. So we are now the proud owners of 6
large and 6 medium sized wooden moose.
Perhaps we can find some way to integrate
them into the decorations for our wedding next year.
Secunia collect some very interesting information about the patch
state of Windows systems. Their results from 20,000 machines published
yesterday were that over 98% of PCs were
insecure, having at least one out-of-date application installed.
Actually this isn't surprising and is exactly what I'd expect;
it's all down to third party applications.
Let's say you're browsing the web. It's more than likely that at
some point you'll want to view some PDF files, watch some Flash
content, or play a Java game. Those tasks are all dealt with by third
party applications, although to the end user it's all part of the
browser experience. Since your system is only as secure as its
weakest link, you need to manage security updates for those third
party applications just as carefully as you manage security updates
for the rest of your system. That's why Adobe Reader, Java, Flash,
and all the myriad of other applications you've installed in order to
make your system useful have their own update mechanisms. Some
applications on Windows will 'phone home' when they are run and check
to see if they need to be updated, others deploy services that sit in
the background looking for updates from time to time, others even
check every time your system starts. Many don't get automated updates
How do you deal with all that risk? I believe it's possible by
providing an OS distribution which includes all the bits you'll
likely need to make a useful computing environment, thereby taking
away that update uncertainty. Red Hat ship several PDF viewers in our
distributions for example, but we also ship (in an Extras channel)
Adobe Reader. Our Security Response Team are monitoring for security
issues in everything we ship, all the third party applications,
and providing a single point of contact, a single
notification system, and a single way to get the updates.
If Microsoft knew that say 25% of all their users installed
Firefox, wouldn't they be better bundling it and providing their
centralised automated updates for it, to reduce their customers
overall risk? They do already bundle some third party applications, although it's
been with mixed success as we found 3 years ago when they
provide security fixes for bundled Flash (ZDNet
This is, in part, why you've not seen me respond recently to the
Vista security reports which compare vulnerability counts. In these
reports they use a cut-down minimal Red Hat Enterprise Linux
installation in order to make it look more like Windows for the
comparisons. But this is completely backwards -- the fact that we're
including and fixing the flaws using a common process in so much
third party software is actually helping reduce the risk and protect
real customers. For example we could easily cut our vulnerability
count by shipping only one PDF viewer instead of four. But if we know
that these other viewers are going to get installed by the customer
anyway all we've done is to hide the vulnerability count elsewhere,
and you've made the customers overall risk increase.
So it may seem counter-intuitive but we should ship as much third
party applications (that we know people use) as we can, because a
single managed security update and notification process will decrease
a users overall risk. The fewer third party applications that users
have to get from elsewhere and install and manage for themselves the better
in my opinion.
Red Hat Enterprise Linux 5.2 was released last week, around 6 months since the
release of 5.1 in November 2007. So let's use this opportunity to take a quick
look back over the vulnerabilities and security updates we've made in that time,
specifically for Red Hat Enterprise Linux 5 Server.
The graph below shows the total number of security updates issued for Red Hat
Enterprise Linux 5 Server starting at 5.1 up to and including the 5.2 release,
broken down by severity. I've split it into two columns, one for the packages
you'd get if you did a default install, and the other if you installed every
single package (which is unlikely as it would involve a bit of manual effort
to select every one). So, for a given installation, the number
of packages and vulnerabilities will probably be somewhere between the two.
So for a default install, from release of 5.1 up to and including 5.2, we shipped 46
updates to address 119 vulnerabilities. 8 advisories were rated critical, 24
were important, and the remaining 14 were moderate and low.
For all packages, from release of 5.1 to and including 5.2, we shipped 62 updates
to address 179 vulnerabilities. 9 advisories were rated critical, 29 were
important, and the remaining 24 were moderate and low.
The nine critical updates were in five different packages:
- Four updates to Firefox (November, February, March, April)
where a malicious web site could potentially run arbitrary code as the
user running Firefox. Given the nature of the flaws, ExecShield
protections in RHEL5 should make exploiting these memory flaws
- An update to the GnuTLS library (May), where
a remote attacker who can connect to a server making use of GnuTLS could
cause a buffer overflow. In Red Hat Enterprise Linux 5, the CUPS print
server uses GnuTLS.
- An update to MIT Kerberos (March),
where a remote attacker who can conect to the krb5kdc or kadmind
services could cause a buffer overflow.
- An update to OpenPegasus
a remote attacker who can connect to OpenPegasus could cause a buffer overflow.
The Red Hat Security Response Team believes that it would be hard to remotely
exploit this issue to execute arbitrary code, due to the default SELinux
targeted policy, and the default SELinux memory protection tests.
- Two updates to Samba (November, December) where
a remote attacker who can connect to the Samba port could cause buffer
overflows. In addition to
ExecShield making this harder to exploit, the impact of any sucessful
exploit would be reduced as Samba is constrained by an SELinux targeted
policy (enabled by default).
Updates to correct all of these critical issues were available via Red Hat
Network either the same day, or one calendar day after the issues were public.
To get a better idea of risk we need to look not only at the vulnerabilities but
also the exploits written for those vulnerabilities.
A proof of concept exploit exists publicly for one of the
but we are not aware of public exploits for any other of those critical
vulnerabilities. Also of high risk was an important "zero-day" exploit affecting the Linux
kernel where a local unprivileged user could gain root privileges.
Red Hat Enterprise Linux 5.1 was affected and
a fix was
available two calendar days after public disclosure.
Red Hat Enterprise Linux 5 shipped with a number of security technologies
designed to make it harder to exploit vulnerabilities and in some cases block
exploits for certain flaw types completely. For the period of this study there
were two flaws blocked that would otherwise have required updates:
- A double-free flaw in CUPS. The glibc pointer checking limited the
exploitability of this issue to just a crash of CUPS and not the ability to
execute arbitrary code. code execution. We
still issued an
update, as a remote attacker could trigger this flaw and cause CUPS to
- An uninitialized pointer free flaw in unzip, caught by the glibc pointer
checking. As exploitation of this flaw results in just
a crash of a
user application, no updates were needed.
This data is interesting to get a feel for the risk of running Enterprise Linux
5 Server, but isn't really useful for comparisons with other versions or
distributions -- for example, a default install of Red Hat Enterprise 4AS did
not include Firefox. You can get the results I presented above for yourself by
using our public
security measurement data and tools, and run your own custom metrics for any
given Red Hat product, package set, timescales, and severities.
See also 5.0 to 5.1 risk report
ZoneMinder is an amazing Linux video camera
security and surveillance application I use as part of my home automation
system. ZoneMinder prior to version 1.23.3 contains unescaped
PHP exec() calls which can allow an authorised remote user the ability to run
arbitrary code as the Apache httpd user (CVE-2008-1381)
v2 Base Score 6.5
This is really a moderate severity flaw because you need a remote attacker who
has the ability to start/stop/control ZoneMinder, and you really should protect
your ZoneMinder installation so you don't allow arbitrary people to control your
security system. (Although I think at least one distributor package of
ZoneMinder doesn't protect it by default, and you can find a few unprotected
ZoneMinder consoles using a web search).
I discovered this because when we went on holiday early in April I forgot to
turn down the heating in the house. Our heating system is controlled by
computer and you can change the settings locally by talking to a Jabber heating
bot (Figure 1). But remotely over the internet it's pretty locked down and the only thing
we can access is the installation of ZoneMinder. So without remote shell access,
and with an hour to spare at Heathrow waiting for the connecting flight to
Phoenix, I figured the easiest way to correct the temperature was to find a
security flaw in ZoneMinder and exploit it. The fallback plan was to explain to
our house-minder how to change it locally, but that didn't seem as much fun.
So I downloaded ZoneMinder and took a look at the source. ZoneMinder is a
mixture of C and PHP, and a few years ago I found a buffer overflow in one of
the C CGI scripts, but as I use Red Hat Enterprise Linux exploiting any new
buffer overflow with my ZoneMinder compiled as PIE definately wouldn't be
feasible with just an hours work. My PHP and Apache were up to date too. So I
focussed on the PHP scripts.
A quick grep of the PHP scripts packaged with ZoneMinder found a few cases where
the arguments passed to PHP exec() were not escaped. One of them was really
straightforward to exploit, and with a carefully crafted URL (and if you have
authorization to a ZoneMinder installation) you can run arbitrary shell code as
the Apache httpd user. So with the help of an inserted semicolon and one reverse shell
I had the ability to remotely turn down the heating, and was happy.
I notified the ZoneMinder author and the various vendors shortly after and
updates were released today (a patch is also
Figure 1: Local heating control
So if you're wondering why I've not bloged in a while it's because
we're just back from holiday, the first in a few years. It was pretty
eventful; I got engaged
to Tracy at Shoshone Point at the Grand Canyon, we saw Spamalot
in Vegas, and went to see Rocco Deluca
play live in LA (Tracy even managed to get a photo with
her favourite actor Kiefer Sutherland who turned up to watch).
I'm out on holiday soon to Arizona, so we've been looking for ways to geocode
the photos we'll be taking and get a record of our route. I use a Mio A701
phone which has built-in GPS, and this time we'll be using Tom Tom in the USA
rather than Mapopolis. The problem with Tom Tom Navigator is that it doesn't
keep a track log, and there doesn't seem to be any plugins to allow it to do so.
So here is the solution I've been experimenting with over the weekend.
- Make sure the GPS Intermediate Driver is enabled, on the MIO there
is a built-in "GPS Settings" utility where I have it set to COM4 and "Manage
- Use the GPS2Blue
utility. Make sure it's set to GPS on COM4, 4800 baud, with logging
only of GGA/GLL/RMC/VTG NMEA, and select 'Log processed raw data...'. You don't
need to enable the "2blue" bit, we're just using it to write the tracklog.
- Make sure your camera has a date and time that is close to the one being shown
by GPS2Blue from the satellites
- Start TomTom. Make sure it's also set to COM4, 4800 baud. This
will work because the GPS Intermediate Driver is opened by GPS2Blue. You
can't start TomTom first, but you can exit GPS2Blue and leave TomTom
- After finishing you end up with a NMEA track log with an hour of logging
taking up about 1.6Mb. Transfer it to your Fedora machine.
On my Fedora machine:
- Use gpsbabel to convert the NMEA
track log and clean it up a bit. I used:
gpsbabel -i nmea -f GPS_2008-03-03_122630.log -x discard,hdop=10,sat=5 -o gpx -F out.gpx
- Use gps2photo.pl to
add the geocoding to your images. This script looks at the time and date the
photo was taken and tries to match it up to an entry in the tracklog, so you
may need to play with the timeoffset to
deal with timezone differences. Although we have snow, being in the UK in the Winter has
it's advantages as we're UTC+0, so I just used:
gpsPhoto.pl --geoinfo=osm --dir ./ --gpsfile out.gpx --timeoffset 0 \
--city=auto --sublocation=auto --state auto --country auto --kml out.kml
The exif metadata inside each jpeg now contains the approximate co-ordinates
of where you were when you took the photo along with a guess of the location
(city, country, etc). You can load out.kml into GoogleEarth to see the
tracklog and photos on a map. If you've allowed Flickr to read the location data
from exif then uploading a geotagged photo will automatically place it on a
map. (Make sure you consider the consequences before enabling that option or
you may end up unintentionally leaking information like the location of your
friends houses or parties you've been to). Here's a quick pic taken in the snow today to test it out:
It sometimes seems like the Security Response Team at Red Hat are
pushing security updates every day, but actually a default
installation of Enterprise Linux 4 AS was vulnerable to only 7
critical security issues in the first three years since release. But to
get a picture of the risk you need to do more than count
risk report was published yesterday in Red Hat Magazine and
reveals the state of security since the release of Red Hat Enterprise
Linux 4 including metrics, key vulnerabilities, and the most common
ways users were affected by security issues.
"Red Hat knew about 49% of the security
vulnerabilities that we fixed in advance of them being publicly
disclosed. For those issues, the average notice was 21 calendar days,
although the median was much lower, with half the private issues
having advance notice of 8 days or less."
Last Friday, just as I was finishing work for the day, an email
appeared in my mailbox from the UK CPNI announcing a public remote
code execution flaw in Apache on HP-UX. As Chair of the Apache
Software Foundation Security Team I knew there were no outstanding remote code
execution flaws in Apache HTTP server (in fact we've not had a remote
code execution flaw for many years) so I was expecting to invoke the
Red Hat Critical Action Plan which would have meant a rather long
weekend for me, my team, and various development and quality engineering staff.
First thing to do was to find the original source of the advisory,
as co-ordination centres and research firms are known to often play the
Telephone game, with advisory texts mangled beyond recognition. Following
the links led to the actual
advisory on the HP site. This describes the vulnerability as follows:
But then they give the CVE name for the flaw, CVE-2007-6388,
which is a known public flaw fixed last month in various
Apache versions from the ASF and in updates from various vendors
that ship Apache (including Red Hat).
This flaw is a cross-site scripting flaw in the mod_status module.
Note that the server-status page is not enabled by default and it is
best practice to not make this publicly available.
I wrote mod_status over 12 years ago and so I know that this flaw is exactly
how the ASF describes it; it definitely can't let a remote attacker execute
arbitrary code on your Apache HTTP server, under any circumstances.
I fired off a quick email to a couple of contacts in the HP security
team and they confirmed that the flaw they fixed is just the cross-site
scripting flaw, not a remote code flaw. The CVSS ratings they give in
their advisory are consistent with it being a cross-site scripting flaw
So happy with a false alarm we cancelled our Critical Action Plan and
I went off and had a nice weekend
taking panoramas without a tripod ready for an upcoming holiday. My first
attempt came out better than I expected:
Secunia released a security summary report for 2007 and surprisingly
gave a count for Red Hat for the year at over 600 vulnerabilities. I
had no idea how they got to this number, it certainly doesn't match
our own publicly available metrics at
Using our public tool, for every Red Hat product and service, for 2007
we issued 306 advisories to fix 404 vulnerabilities. Of those 404
vulnerabilities 41 were critical (on the scale used by Microsoft and
Most people are not going to be using every Red Hat product, so taking
just Enterprise Linux product you find 348 vulnerabilities, of which 27
were critical. A given user is going to only be vulnerable to the issues that affect
the products and packages they have installed. Using the scripts on
our pages you can figure it out for your own circumstances. But as an
example, the default installation of Red Hat Enterprise Linux 4 AS had
172 vulnerabilities of which 4 were critical.
The Secunia report does actually make it clear you can't use their
vulnerability count as a method of comparing platforms, in part due to the
differences in methodology of the vendors, but I'm sure this won't stop
some press from jumping to conclusions if they don't read the actual report.
I've asked Secunia how they got to their number of vulnerabilities, but in the
meantime, a raw count of vulnerabilities is only a small part of the
overall risk exposure in using a product. I've got some more reports that go
into this in more detail for two years of Enterprise Linux 4 and Enterprise Linux
5.0 to 5.1.
Update: Coverage of this: ZDNet
Update: Secunia told me that they treat each advisory separately; so for example
yesterday we issued updates for some moderate severity issues in
the Apache Web server, but we did separate advisories for each affected
product: Red Hat Enterprise Linux 2.1, 3, 4, 5, Red Hat Application Stack v1, v2.
So in this case the same Apache vulnerability would be counted 6 times.
A year ago I published a table of
Security Features in
Red Hat Enterprise Linux and Fedora Core. Since then we've released
two more Fedora versions, and a Red Hat Enterprise Linux, so it's time to
update the table.
Between releases there are lots of changes made to improve security and I've not
listed everything; just a high-level overview of the things I think are most
interesting that help mitigate security risk. We could go into much more
detail, breaking out the number of daemons covered by the SELinux default
policy, the number of binaries compiled PIE, and so on.
1 Since June 2004, 2 Since September 2004, 3 Selected Architectures
Hi! I'm Mark Cox. This blog gives my
thoughts and opinions on my security
work, open source, fedora, home automation,
and other topics.
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