From: Joerg Sonnenberger <[EMAIL PROTECTED]>
To: freebsd-hackers@freebsd.org
Subject: Re: Configuration differences for jails
Date: Thu, 21 Apr 2005 13:43:59 +0200

On Thu, Apr 21, 2005 at 07:39:08AM -0400, c0ldbyte wrote:
> Now if that last question is correct and thats the proccess you are
using
> to create a jail then depending on the situation wouldnt that inturn
> defeat some of the main purposes of the jail, like the following. If
you
> mounted your "/bin" on "/mnt/jail/bin" then if a person that was
looking
> to break in and effect the system that is currently locked in the
"jail"
> all he would have to do is just write something to the "jail/bin" which
is
> actualy your root "/bin" and then the next time a binary is used from
your
> root directories it could still infect the rest of the system
ultimately
> defeating the purpose of what you just set up. To my understanding and
use
> a jail is somewhat totaly independent of the OS that it resides in and
> wont be if you are using nullfs to mount root binary directories on it.

ro mount as written by grant parent protects against this.

I am not very familar with mount_nullfs, but i think it is _one_ copy with _multiple_ references(FIXME).So if we modify something in one jail, the same effect will
also impose on other jails,even the real machine. Due to this problem,
readonly mounts may be a good choice.
BUT if we do some things related to the /etc files, such as passwd, ro mounts can not deal with this situation because different jails need different passwd files for
private users.
So I think this can only be done by making a copy of relevant files but not ro
mounts.
Any idea?


regards
Jas

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