Bugtraq: Re: Unprivilegued settings for FreeBSD kernel variables

["Eygene A. Ryabinkin" <rea () rea mbslab kiae ru>]

On Tue, Jun 15, 2004 at 09:01:13PM +0200, Dag-Erling Sm?rgrav wrote:
> I've already told you that there is no such threat, since the attack
> you describe can only be initiated by someone who already has
> unrestricted access.  Please stop wasting everybody's time.
 You are wrong. Unrestricted access means _really unrestricted_ and
kernel securelevel restricts access to certain places even to root.
IMHO, it's dagerous bug, because some administrators can think "...hmm,
I've enabled the hardest securelevel and even if a hacker would break
into my host with r00t privileges he will be restricted in certain ways.
The only thing he can do is to change /etc/rc.conf (for example) and
_reboot_ my host. But I will notice the reboot." So, for certain
people the following formulae may hold:
         Hardest securelevel + no reboots = good security.
 
 But this bug changes things. One can lower securelevel, do some nasty things
and raise it again _without reboots_. So, as I've already noted, you are wrong.
The bug _gives_ you almost unrestricted access.
        rea