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Date:      Wed, 2 Oct 1996 10:41:41 -0400
From:      Garrett Wollman <wollman@lcs.mit.edu>
To:        Michael Hancock <michaelh@cet.co.jp>
Cc:        current@freebsd.org
Subject:   Immutable flags (was: Re: WARNING: botched ld.so commit! :-()
Message-ID:  <9610021441.AA28734@halloran-eldar.lcs.mit.edu>
In-Reply-To: <Pine.SV4.3.93.961002102251.1788A-100000@parkplace.cet.co.jp>
References:  <199610011435.AAA32208@godzilla.zeta.org.au> <Pine.SV4.3.93.961002102251.1788A-100000@parkplace.cet.co.jp>

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<<On Wed, 2 Oct 1996 10:25:43 +0900 (JST), Michael Hancock <michaelh@cet.co.jp> said:

> On Wed, 2 Oct 1996, Bruce Evans wrote:
>> This shows that the chflags on ld.so is mainly to [prevent] shoot[ing]
>> yourself in the foot.  It doesn't improve security.

> I was thinking of asking why we're evening using it when
> INITIAL_IMMUTABLE_LEVEL is not configurable without hardcoding the source.

Ummm, INITIAL_IMMUTABLE_LEVEL?  This doesn't mean anything to me.

In any case, the immutable bits are set for two reasons:

1) They were set on the code we got from Berkeley.
2) We wanted to make it easier for people to secure their systems by
pre-configuring those files.

There are a number of files which are necessary for system recovery
which probably should be set immutable but aren't; these include
/bin/sh, /bin/test, /sbin/fsck, and a number of others.  In addition,
administrators will have to remember for themselves to set their
configuration files immutable and their important system directories
append-only, which can only be done after a machine is set up to the
administrator's satisfaction.

-GAWollman

--
Garrett A. Wollman   | O Siem / We are all family / O Siem / We're all the same
wollman@lcs.mit.edu  | O Siem / The fires of freedom 
Opinions not those of| Dance in the burning flame
MIT, LCS, ANA, or NSA|                     - Susan Aglukark and Chad Irschick



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