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From: blymn@baea.com.au (Brett Lymn)
Message-Id: <200003142339.KAA06053@mallee.awadi>
Subject: Re: Kernel modification that verifies execs against a md5
To: fair@clock.org (Erik Fair)
Date: Wed, 15 Mar 2000 10:09:05 +1030 (CST)
Cc: thorpej@zembu.com, blymn@baea.com.au (Brett Lymn),
        tech-security@netbsd.org
In-Reply-To: <v04220802b4f42cd5b404@[10.66.51.205]> from "Erik Fair" at Mar 14, 2000 09:57:16 AM
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According to Erik Fair:
>
>What about netbooted systems (e.g. DEC Shark)? There was a paper 
>given not too many years ago about modifying binaries as they fly by 
>on the wire.

Yes, NFS was not a FS that I thought would be valuable for this
scheme there are too many sneaky things you can do.

> I suppose once we have NFS working by default on top of 
>IPsec, this will be less of a concern...
>

As long as you can trust the file server.

>It is also possible to modify binaries directly, through the disk 
>device. Granted, your program to do so must now understand various FS 
>formats, but since we're all open source here, this shouldn't be too 
>difficult for an attacker, even if it makes his tools fat.
>

At the higher securelevels you are not allowed to open the raw device
so spelunking the FS directly is not an option.

>I don't want this md5 facility on by default, but it wouldn't 
>necessarily be a bad thing to have as an option for the truly 
>paranoid.

It is optional.

> (of course, you're not paranoid if they're really out to 
>get you...).
>

Oh they are, they are ;-)

-- 
===============================================================================
Brett Lymn, Computer Systems Administrator, BAE SYSTEMS
===============================================================================