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.

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 at all.

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 didn't provide security fixes for bundled Flash (ZDNet coverage).

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.

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:

1. 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 harder.
2. 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.

3. An update to MIT Kerberos (March), where a remote attacker who can conect to the krb5kdc or kadmind services could cause a buffer overflow.

4. An update to OpenPegasus (January), where 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.

5. 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 Samba flaws, CVE-2007-6015, 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:

1. 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 crash.
2. 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.

CVSS v2 Base Score 6.5 (AV:N/AC:L/Au:S/C:P/I:P/A:P)

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 available)

Figure 1: Local heating control

On the PocketPC:

• 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 GPS automatically"
• 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 running.
• 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:

output from exiftool: GPS Position : 55 deg 46' 58.21" N, 4 deg 0' 5.50" W City : Motherwell Province-State : Scotland Country-Primary Location Name : United Kingdom

My full 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."

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 too.

So happy with a false alarm we cancelled our Critical Action Plan and I went off and had a nice weekend practicing taking panoramas without a tripod ready for an upcoming holiday. My first attempt came out better than I expected:

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 Red Hat).

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.

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.

	Fedora Core						Fedora		Red Hat Enterprise Linux
	1	2	3	4	5	6	7	8	3	4	5
	2003Nov	2004May	2004Nov	2005Jun	2006Mar	2006Oct	2007May	2007Nov	2003Oct	2005Feb	2007Mar
Firewall by default	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
Signed updates required by default	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
NX emulation using segment limits by default	Y	Y	Y	Y	Y	Y	Y	Y	Y2	Y	Y
Support for Position Independent Executables (PIE)	Y	Y	Y	Y	Y	Y	Y	Y	Y2	Y	Y
Address Randomization (ASLR) for Stack/mmap by default3	Y	Y	Y	Y	Y	Y	Y	Y	Y2	Y	Y
ASLR for vDSO (if vDSO enabled)3	no vDSO	Y	Y	Y	Y	Y	Y	Y	no vDSO	Y	Y
Restricted access to kernel memory by default		Y	Y	Y	Y	Y	Y	Y		Y	Y
NX for supported processors/kernels by default		Y1	Y	Y	Y	Y	Y	Y	Y2	Y	Y
Support for SELinux		Y	Y	Y	Y	Y	Y	Y		Y	Y
SELinux enabled with targeted policy by default			Y	Y	Y	Y	Y	Y		Y	Y
glibc heap/memory checks by default			Y	Y	Y	Y	Y	Y		Y	Y
Support for FORTIFY_SOURCE, used on selected packages			Y	Y	Y	Y	Y	Y		Y	Y
All packages compiled using FORTIFY_SOURCE				Y	Y	Y	Y	Y			Y
Support for ELF Data Hardening				Y	Y	Y	Y	Y		Y	Y
All packages compiled with stack smashing protection					Y	Y	Y	Y			Y
SELinux Executable Memory Protection						Y	Y	Y			Y
glibc pointer encryption by default						Y	Y	Y			Y
FORTIFY_SOURCE extensions including C++ coverage								Y

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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