From owner-freebsd-chat Fri Oct 17 21:32:36 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id VAA26730 for chat-outgoing; Fri, 17 Oct 1997 21:32:36 -0700 (PDT) (envelope-from owner-freebsd-chat) Received: from obie.softweyr.ml.org ([199.104.124.49]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id VAA26724 for ; Fri, 17 Oct 1997 21:32:25 -0700 (PDT) (envelope-from wes@xmission.com) Received: (from wes@localhost) by obie.softweyr.ml.org (8.7.5/8.6.12) id WAA14607; Fri, 17 Oct 1997 22:39:16 -0600 (MDT) Date: Fri, 17 Oct 1997 22:39:16 -0600 (MDT) Message-Id: <199710180439.WAA14607@obie.softweyr.ml.org> From: Wes Peters To: Terry Lambert CC: chat@freebsd.org Subject: Re: C2 Trusted FreeBSD? In-Reply-To: <199710171817.LAA16458@usr06.primenet.com> References: <199710171817.LAA16458@usr06.primenet.com> Sender: owner-freebsd-chat@freebsd.org X-Loop: FreeBSD.org Precedence: bulk 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