[257] in netbsd-help mailing list archive
Re: Security issues
daemon@ATHENA.MIT.EDU (John Hawkinson)
Sat Jul 8 01:35:58 1995
Date: Sat, 8 Jul 1995 01:35:47 -0400
To: Edwin Foo <efoo@MIT.EDU>
Cc: netbsd-help@MIT.EDU
In-Reply-To: "[256] in netbsd-help mailing list archive"
From: John Hawkinson <jhawk@MIT.EDU>
> Hello. I was trying to get X to run on my computer yesterday and
> after quite a few hours of head scratching with the help of ghudson
> I found that there might be a bug in the NetBSD Aperture driver,
[...]
> > 1. Disable the kernel security feature by initializing the
> > ``securelevel'' variable to -1 in /sys/kern/kern_sysctl.c, line
> > 205 and building a new kernel. For more informations, see the
> > comments in /usr/include/sys/systm.h.
> > 2. Install the aperture driver. ....
>
> Seeing as how (2) is not a good option until the driver gets fixed, I would
> like to try (1).
note to everybody else: Actually, we did this by recompiling init,
since that was faster and easier...
> However, I'm curious as to just how much or how little security I
> lose by enabling access to /dev/mem in multiuser mode; mainly, does
> this make my computer easy to break into?
Not really, no. It essentially means that once someone is root, they
can do things that they've always been able to do under traditional
operating systems. This basically consists of:
Writing to /dev/mem (arbitrary memory)
Writing to raw disk devices (outside the filesystem)
But if they're root, they've essentially already cracked your system.
It's probably not worth worrying about securelevel.
Securelevel is in general most useful along with the ``immutable
files'' option, which prevents people from modifying files in
securelevel>0, and this is hand-in-hand with the prevention of writes
to raw devices (which would bypass this protection). If you don't use
this (you dno't), it probably doesn't matter.
--jhawk
