Date: Fri, 17 Oct 1997 22:39:16 -0600 (MDT) From: Wes Peters <softweyr@xmission.com> To: Terry Lambert <tlambert@primenet.com> Cc: chat@freebsd.org Subject: Re: C2 Trusted FreeBSD? Message-ID: <199710180439.WAA14607@obie.softweyr.ml.org> In-Reply-To: <199710171817.LAA16458@usr06.primenet.com> References: <XFMail.971015212530.cdillon@tri-lakes.net> <199710171817.LAA16458@usr06.primenet.com>
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Terry Lambert writes:
> > >Or in other words - C2 or not, we are going to need a modified ffs that
> > >properly overwrites the freed (via unlink, truncate or other means)
> > >storage on disk anyways?
> >
> > Not my area of expertise exactly, but from what I gather, yes. This would
> > eat tremendous amounts of precious I/O, unless I suppose it was done at
> > idle times, but that might defeat the purpose of it.
>
> This should be done on a block by block basis, and could be done
> in a stacking layer on top of a variable granularity block store.
Yes, and there are some strategies that could be adopted to minimize the
impact of this. Disk blocks are not immediately freed, but rather
returned to a queue of blocks to be overwritten; once overwritten they
are marked as freed. The overwrites could be interleaved with normal
disk I/O head stepping algorithms, and/or performed during idle I/O
times unless needed in the free store.
It would be advantageous to allow multiple overwrite strategies as well,
specifying no overwrite for low-security situations like my workstation
at home, behind an infrequently connected firewall; single overwrite for
situations where you're not completely paranoid about your user base,
and multiple-overwrite with varying patterns for FreeBSD systems
installed in ballistic missile submarines. ;^)
--
"Where am I, and what am I doing in this handbasket?"
Wes Peters Softweyr LLC
http://www.xmission.com/~softweyr softweyr@xmission.com
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