Re: Read only devices (Re: BoS: amodload.tar.gz - ...)

[mdz () netrail net (Matt Zimmerman)]

On Fri, 21 Jun 1996, Sean Vickery wrote:

> On 20 June 1996, Patrick Ferguson wrote:
> > Instead of the hassle of dealing with that, properly configure your
> > filesystems.  Since you can mount a filesystem at any point in the tree,
> > why not just spend some extra time and diagram out which directories will
> > be write accessed the least and mount them read-only.  Even superuser privs
> > can't violate ro mounting.
> > [...]
> Mounting filesystems containing system binaries read-only does not
> sound as safe as turning on the hardware write-protect on the disks
> containing those filesystems.
>
> Why? If an attacker can alter your system binaries, s/he must have root
> privileges.  Which means s/he can also unmount the filesystems and
> remount them read-write.  But to change the disk back to read-write
> cannot be done over the network.  It requires physical access to the
> disk(s).

Right...which makes a good case for using NFS instead, and exporting the
filesystems read-only from a server which is hopefully less accessible to
the general public and/or intruders (offering a very limited set of
network services, etc.).  Of course, then you have to deal with the usual
NFS security issues (most of which can be avoided within reasonable limits
by well-configured firewalls and TCP wrappers).

// Matt Zimmerman       Chief of System Management           NetRail, Inc.
// mdz () netrail net                                       sales () netrail net
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