4 ms·

Docker "isolation" is not as strong as most hipsters think. :-)

• wastedhours 12y ago
  Interesting, any links which expand on the issues?
  • stevekemp 12y ago
    This is the first that comes to mind: http://blog.bofh.it/debian/id_413 http://blog.bofh.it/debian/id_413
    • kalmi10 12y ago
      That's an article from 2011. This evasion does not work today.
      • stevekemp 12y ago
        That example is old, but yes it does work, and will continue to work until docker uses user namespaces. That said the example is not a good one because of the changes applied these days, e.g. the use of the UID on the host-side.
        • kalmi10 12y ago
          I actually tried it on Docker 1.2.0 with the ubuntu:14.04 image. /sys is already mounted and it is read-only, and it cannot be mounted manually: root@07ba8c752195:/# mkdir sys2 root@07ba8c752195:/# mount -t sysfs sysfs /sys2 mount: block device sysfs is write-protected, mounting read-only mount: cannot mount block device sysfs read-only
          • Lai0chee 12y ago
            BTW: Just one example of a typical Linux namespace vulnerability: http://git.kernel.org/cgit/linux/kernel/git/ebiederm/user-namespace.git/commit/?h=for-next&id=a6138db815df5ee542d848318e5dae681590fccd http://git.kernel.org/cgit/linux/kernel/git/ebiederm/user-na...
          • stevekemp 12y ago
            I tested this with the busybox image, and received a warning that /sys was already mounted, but the attack then proceded to work as expected.
            • kalmi10 12y ago
              kalmi@sylph ~> docker run -t -i busybox:latest / # mount -t sysfs sysfs /sys mount: permission denied (are you root?) / # mkdir sys2 / # mount -t sysfs sysfs /sys2 mount: mounting sysfs on /sys2 failed: Permission denied kalmi@sylph ~> docker --version Docker version 1.2.0, build fa7b24f kalmi@sylph ~> uname -r Linux sylph 3.13.0-35-generic #62-Ubuntu SMP Fri Aug 15 01:58:42 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
              • stevekemp 12y ago
                We don't need to argue about this, but I see the same permission-denied issue as you, but that doesn't matter. The /sys is mounted already and reading/writing to it succeeds: / # mount -t sysfs sysfs /sys mount: permission denied (are you root?) / # echo /var/lib/docker/aufs/mnt/638ae26bb710384a8ebade3a66049277affea8b0f3e96003d351f167a9706aef/tmp/evil-helper > /sys/kernel/uevent_helper / # cat /sys/kernel/uevent_helper /var/lib/docker/aufs/mnt/638ae26bb710384a8ebade3a66049277affea8b0f3e96003d351f167a906aef/tmp/evil-helper From there the attack works. Obviously the change here is that I need to know the full UID, which is a cheat, but ..
  • Lai0chee 12y ago
    Docker is based on Linux namespaces. The first thing which comes to mind is that Docker does not use user namespaces. Hence, the root within Docker is the same root as on the host side. Of course Docker papers over the issue by using apparmor and other tricks but this does not cure the issue itself. Linux containers (LXC, libvirt-lxc, Docker) are shared kernel visualization. Every single kernel vulnerability will hit you hard. In contrast to LXC and libvirt-lxc Docker lets you configure a lot of insane setups which are not secure. (But easy to setup) Also keep in mind resource issues. If you setup your container in a wrong way it my eat all your available file descriptors, all memory, etc... (Because it is shared kernel) Let's face it, the whole technology was not designed for sandboxing, more for easy deployment of applications. That said, I really love container and use them a lot in production with libvirt-lxc. But I don't use them for sandboxing.
• nickstinemates 12y ago
  A lot developing in this space. Will have more to talk about soon :)