RE: securety related question...

> On Sat, 5 Oct 2002, Bob Kimmel wrote:
>
> > I asked a question on one of the LFS groups a while back, and someone
> > told me about the --bind option of mount, which causes the same files
> > to appear in more than one place in the directory structure.  It seems
> > to me this feature could be used to create virtual chroot jails - even
> > if the files needed by a particular app/daemon are dispersed, shared
> > with other daemons, etc., one could create a jail directory, and then
> > mount --bind the needed directories within the jail.
> >
> > Is this analysis correct?  Are there performance issues with this
> > approach?  Has anyone done this, thought about doing it, tried it
> > and found it doesn't work, etc.?  I'd be interested in hearing
> > opinions...
>
> The point of chrooting something is to _deny utterly_ any chance it has of
> accessing other parts of the filesystem.  If you mount other parts of the
> filesystem that are in use elsewhere, you _defeat the purpose_ of
> chrooting.
>

The problem is that the alternative is sometimes not to chroot at all.
For example, I am currently running qmail.  I would like to chroot, but
I can't (at least, if there is a way to do it, I don't know what it is).
My idea was, using the mount --bind option might allow one to use chroot
when one couldn't otherwise.  So, my question is, does doing this defeat
the purpose of chroot as badly as not using chroot does :-)  If I can
chroot a daemon without mounting other parts of the filesystem within
the chroot jail, I'll do that.  But if I can't, is a virtual chroot
better than no chroot at all?

BK

Bob Kimmel

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