Launch secure LXC containers on Fedora 20 using SELinux and sVirt

selinux-penguin-new_mediumGetting started with LXC is a bit awkward and I’ve assembled this guide for anyone who wants to begin experimenting with LXC containers in Fedora 20. As an added benefit, you can follow almost every step shown here when creating LXC containers on Red Hat Enterprise Linux 7 Beta (which is based on Fedora 19).

You’ll need a physical machine or a VM running Fedora 20 to get started. (You could put a container in a container, but things get a little dicey with that setup. Let’s just avoid talking about nested containers for now. No, really, I shouldn’t have even brought it up. Sorry about that.)

Prep Work

Start by updating all packages to the latest versions available:

yum -y upgrade

Verify that SELinux is in enforcing mode by running getenforce. If you see Disabled or Permissive, get SELinux into enforcing mode with a quick configuration change:

sed -i 's/^SELINUX=.*/SELINUX=enforcing/' /etc/selinux/config

I recommend installing setroubleshoot-server to make it easier to find the root cause of AVC denials:

yum -y install setroubleshoot-server

Reboot now. This will ensure that SELinux comes up in enforcing mode (verify that with getenforce after reboot) and it ensures that auditd starts up sedispatch (for setroubleshoot).

Install management libraries and utilities

Let’s grab libvirt along with LXC support and a basic NAT networking configuration.

yum -y install libvirt-daemon-lxc libvirt-daemon-config-network

Launch libvirtd via systemd and ensure that it always comes up on boot. This step will also adjust firewalld for your containers and ensure that dnsmasq is serving up IP addresses via DHCP on your default NAT network.

systemctl start libvirtd.service
systemctl enable libvirtd.service

Bootstrap our container

Installing packages into the container’s filesystem will take some time.

yum -y --installroot=/var/lib/libvirt/filesystems/fedora20 --releasever=20 --nogpg install systemd passwd yum fedora-release vim-minimal openssh-server procps-ng

This step fills in the filesystem with the necessary packages to run a Fedora 20 container. We now need to tell libvirt about the container we’ve just created.

virt-install --connect lxc:// --name fedora20 --ram 512 --filesystem /var/lib/libvirt/filesystems/fedora20/,/

At this point, libvirt will know enough about the container to start it and you’ll be connected to the console of the container! We need to adjust some configuration files within the container to use it properly. Detach from the console with CTRL-].

Let’s stop the container so we can make some adjustments.

virsh -c lxc:// shutdown fedora20

Get the container ready for production

Hop into your container and set a root password.

chroot /var/lib/libvirt/filesystems/fedora20 /bin/passwd root

We will be logging in as root via the console occasionally and we need to allow that access.

echo "pts/0" >> /var/lib/libvirt/filesystems/fedora20/etc/securetty

Since we will be using our NAT network with our auto-configured dnsmasq server (thanks to libvirt), we can configure a simple DHCP setup for eth0:

cat < < EOF > /var/lib/libvirt/filesystems/fedora20/etc/sysconfig/network
cat < < EOF > /var/lib/libvirt/filesystems/fedora20/etc/sysconfig/network-scripts/ifcfg-eth0

Using ssh makes the container a lot easier to manage, so let’s ensure that it starts when the container boots. (You could do this via systemctl after logging in at the console, but I’m lazy.)

chroot /var/lib/libvirt/filesystems/fedora20/
ln -s /usr/lib/systemd/system/sshd.service /etc/systemd/system/


Cross your fingers and launch the container.

virsh -c lxc:// start --console fedora20

You’ll be attached to the console during boot but don’t worry, hold down CTRL-] to get back to your host prompt. Check the dnsmasq leases to find your container’s IP address and you can login as root over ssh.

cat /var/lib/libvirt/dnsmasq/default.leases


After logging into your container via ssh, check the process labels within the container:

# ps aufxZ
LABEL                           USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 1 0.0  1.3 47444 3444 ?      Ss   03:18   0:00 /sbin/init
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 18 0.0  2.0 43016 5368 ?     Ss   03:18   0:00 /usr/lib/systemd/systemd-journald
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 38 0.4  7.8 223456 20680 ?   Ssl  03:18   0:00 /usr/bin/python -Es /usr/sbin/firewalld -
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 40 0.0  0.7 26504 2084 ?     Ss   03:18   0:00 /usr/sbin/smartd -n -q never
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 41 0.0  0.4 19268 1252 ?     Ss   03:18   0:00 /usr/sbin/irqbalance --foreground
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 44 0.0  0.6 34696 1636 ?     Ss   03:18   0:00 /usr/lib/systemd/systemd-logind
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 46 0.0  1.8 267500 4832 ?    Ssl  03:18   0:00 /sbin/rsyslogd -n
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 dbus 47 0.0  0.6 26708 1680 ?     Ss   03:18   0:00 /bin/dbus-daemon --system --address=syste
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 rpc 54 0.0  0.5 41992 1344 ?      Ss   03:18   0:00 /sbin/rpcbind -w
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 55 0.0  0.3 25936 924 ?      Ss   03:18   0:00 /usr/sbin/atd -f
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 56 0.0  0.5 22728 1488 ?     Ss   03:18   0:00 /usr/sbin/crond -n
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 60 0.0  0.2 6412 784 pts/0   Ss+  03:18   0:00 /sbin/agetty --noclear -s console 115200 
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 74 0.0  3.2 339808 8456 ?    Ssl  03:18   0:00 /usr/sbin/NetworkManager --no-daemon
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 394 0.0  5.9 102356 15708 ?  S    03:18   0:00  \_ /sbin/dhclient -d -sf /usr/libexec/nm
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 polkitd 83 0.0  4.4 514792 11548 ? Ssl 03:18   0:00 /usr/lib/polkit-1/polkitd --no-debug
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 rpcuser 110 0.0  0.6 46564 1824 ? Ss   03:18   0:00 /sbin/rpc.statd
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 111 0.0  1.3 82980 3620 ?    Ss   03:18   0:00 /usr/sbin/sshd -D
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 409 0.0  1.9 131576 5084 ?   Ss   03:18   0:00  \_ sshd: root@pts/1
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 413 0.0  0.9 115872 2592 pts/1 Ss 03:18   0:00      \_ -bash
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 438 0.0  0.5 123352 1344 pts/1 R+ 03:19   0:00          \_ ps aufxZ
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 411 0.0  0.8 44376 2252 ?    Ss   03:18   0:00 /usr/lib/systemd/systemd --user
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 412 0.0  0.5 66828 1328 ?    S    03:18   0:00  \_ (sd-pam)
system_u:system_r:virtd_lxc_t:s0-s0:c0.c1023 root 436 0.0  0.4 21980 1144 ?    Ss   03:19   0:00 /usr/lib/systemd/systemd-hostnamed

You’ll notice something interesting if you run getenforce now within the container — SELinux is disabled. Actually, it’s not really disabled. The processing of SELinux policy is done on the host. The container isn’t able to see what’s going on outside of its own files and processes. The libvirt documentation for LXC hints at the importance of this isolation:

A suitably configured UID/GID mapping is a pre-requisite to making containers secure, in the absence of sVirt confinement.

In the absence of the “user” namespace being used, containers cannot be considered secure against exploits of the host OS. The sVirt SELinux driver provides a way to secure containers even when the “user” namespace is not used. The cost is that writing a policy to allow execution of arbitrary OS is not practical. The SELinux sVirt policy is typically tailored to work with an simpler application confinement use case, as provided by the “libvirt-sandbox” project.

This leads to something really critical to understand:

Containers don’t contain

Dan Walsh has a great post that goes into the need for sVirt and the protections it can provide when you need to be insulated from potentially dangerous virtual machines or containers. If a user is root inside a container, they’re root on the host as well. (There’s an exception: UID namespaces. But let’s not talk about that now. Oh great, first it was nested containers and now I brought up UID namespaces. Sorry again.)

Dan’s talk about securing containers hasn’t popped up on the Red Hat Summit presentations page quite yet but here are some notes that I took and then highlighted:

  • Containers don’t contain. The kernel doesn’t know about containers. Containers simply use kernel subsystems to carve up namespaces for applications.
  • Containers on Linux aren’t complete. Don’t compare directly to Solaris zones yet.
  • Running containers without Mandatory Access Control (MAC) systems like SELinux or AppArmor opens the door for full system compromise via untrusted applications and users within containers.

Using MAC gives you one extra barrier to keep a malicious container from getting higher levels of access to the underlying host. There’s always a chance that a kernel exploit could bypass MAC but it certainly raises the level of difficulty for an attacker and allows server operators extra time to react to alerts.

DevOps and enterprise inertia

As I wait in the airport to fly back home from this year’s Red Hat Summit, I’m thinking back over the many conversations I had over breakfast, over lunch, and during the events. One common theme that kept cropping up was around bringing DevOps to the enterprise. I stumbled upon Mathias Meyer’s post, The Developer is Dead, Long Live the Developer, and I was inspired to write my own.

Before I go any further, here’s my definition of DevOps: it’s a mindset shift where everyone is responsible for the success of the customer experience. The success (and failure) of the project rests on everyone involved. If it goes well, everyone celebrates and looks for ways to highlight what worked well. If it fails, everyone gets involved to bring it back on track. Doing this correctly means that your usage of “us” and “them” should decrease sharply.

The issue at hand

One of the conference attendees told me that he and his technical colleagues are curious about trying DevOps but their organization isn’t set up in a way to make it work. On top of that, very few members of the teams knew about the concept of continuous delivery and only one or two people knew about tools that are commonly used to practice it.

I dug deeper and discovered that they have outages just like any other company and they treat outages as an operations problem primarily.  Operations teams don’t get much sleep and they get frustrated with poorly written code that is difficult to deploy, upgrade, and maintain.  Feedback loops with the development teams are relatively non-existent since the development teams report into a different portion of the business.  His manager knows that something needs to change but his manager wasn’t sure how to change it.

His company certainly isn’t unique.  My advice for him was to start a three step process:

Step 1: Start a conversation around responsibility.

Leaders need to understand that the customer experience is key and that experience depends on much more than just uptime. This applies to products and systems that support internal users within your company and those that support your external customers.

Imagine if you called for pizza delivery and received a pizza without any cheese. You drive back to the pizza place to show the manager the partial pizza you received. The manager turns to the employees and they point to the person assigned to putting toppings on the pizza. They might say: “It’s his fault, I did my part and put it in the oven.” The delivery driver might say: “Hey, I did what I was supposed to and I delivered the pizza. It’s not my fault.”

All this time, you, the customer, are stuck holding a half made pizza. Your experience is awful.

Looking back, the person who put the pizza in the oven should have asked why it was only partially made. The delivery driver should have asked about it when it was going into the box. Most important of all, the manager should have turned to the employees and put the responsibility on all of them to make it right.

Step 2: Foster collaboration via cross-training.

Once responsibility is shared, everyone within the group needs some knowledge of what other members of the group do. This is most obvious with developers and operations teams. Operations teams need to understand what the applications do and where their weak points are. Developers need to understand resource constraints and how to deploy their software. They don’t need to become experts but they need to know enough overlapping knowledge to build a strong, healthy feedback loop.

This cross-training must include product managers, project managers, and leaders. Feedback loops between these groups will only be successful if they can speak some of the language of the other groups.

Step 3: Don’t force tooling.

Use the tools that make the most sense to the groups that need to use them. Just because a particular software tool helps another company collaborate or deploy software more reliably doesn’t mean it will have a positive impact on your company.

Watch out for the “sunk cost” fallacy as well. Neal Ford talked about this during a talk at the Red Hat Summit and how it can really stunt the growth of a high performing team.


The big takeaway from this post is that making the mindset shift is the first and most critical step if you want to use the DevOps model in a large organization. The first results you’ll see will be in morale and camaraderie. That builds momentum faster than anything else and will carry teams into the idea of shared responsibility and ownership.

openssl heartbleed updates for Fedora 19 and 20

heartbleedThe openssl heartbleed bug has made the rounds today and there are two new testing builds or openssl out for Fedora 19 and 20:

Both builds are making their way over into the updates-testing stable repository thanks to some quick testing and karma from the Fedora community.

If the stable updates haven’t made it into your favorite mirror yet, you can live on the edge and grab the koji builds:

For Fedora 19 x86_64:

yum -y install koji
koji download-build --arch=x86_64 openssl-1.0.1e-37.fc19.1
yum localinstall openssl-1.0.1e-37.fc19.1.x86_64.rpm

For Fedora 20 x86_64:

yum -y install koji
koji download-build --arch=x86_64 openssl-1.0.1e-37.fc20.1
yum localinstall openssl-1.0.1e-37.fc20.1.x86_64.rpm

Be sure to replace x86_64 with i686 for 32-bit systems or armv7hl for ARM systems (Fedora 20 only). If your system has openssl-libs or other package installed, be sure to install those with yum as well.

Kudos to Dennis Gilmore for the hard work and to the Fedora community for the quick tests.

Detect proxies with icanhazproxy

You can already detect proxy servers using by accessing the service on port 80, 81, and 443. If you compare your results and you see different IP addresses, there’s most likely a proxy in the way.

To make things easier, I’ve launched It’s available on ports 80, 81 and 443 as well. If you choose to access it on port 443, you’ll get a certificate for that you’ll need to ignore.

You’ll get one of two possible responses:

200/OK with JSON output: When a proxy is detected, you’ll receive a 200 response and any proxy-related headers will be returned in JSON format. Here’s a sample:

$ curl
{"via": "1.1 0A065C93"}

You may receive multiple headers via JSON, so please be prepared for that.

204/NO CONTENT and empty response: No common proxy headers were detected. Here’s an example:

$ curl -si | head -n1

If you get this response but you know there’s a proxy in the way, let me know. I may need to look for extra headers or other items in the request.

Go try it out and send me your feedback!