Re: [patch 1/2] [RFC] Simple tamper-proof device filesystem.

["Serge E. Hallyn" <serue@us.ibm.com>]

Quoting Tetsuo Handa (penguin-kernel@i-love.sakura.ne.jp):
> Hello.
> 
> Serge E. Hallyn wrote:
> > CAP_MKNOD will be removed from its capability
> I think it is not enough because the root can rename/unlink device files
> (mv /dev/sda1 /dev/tmp; mv /dev/sda2 /dev/sda1; mv /dev/tmp /dev/sda2).

Sure but that doesn't bother us :)

The admin in the container has his own /dev directory and can do what he
likes with the devices he's allowed to have.  He just shouldn't have
access to others.  If he wants to rename /dev/sda1 to /dev/sda5 that's
his choice.

> > To use your approach, i guess we would have to use selinux (or tomoyo)
> > to enforce that devices may only be created under /dev?
> Everyone can use this filesystem alone.

Sure but it is worthless alone.

No?

What will keep the container admin from doing 'mknod /root/hda1 b 3 1'?

> But use with MAC (or whatever access control mechanisms that prevent
> attackers from unmounting/overlaying this filesystem) is recomennded.

-serge