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Date:      Sun, 20 Jun 1999 22:58:44 -0600
From:      Warner Losh <imp@harmony.village.org>
To:        Eivind Eklund <eivind@FreeBSD.ORG>
Cc:        "Brian W. Buchanan" <brian@CSUA.Berkeley.EDU>, FreeBSD-security Mailing List <freebsd-security@FreeBSD.ORG>
Subject:   Re: proposed secure-level 4 patch 
Message-ID:  <199906210458.WAA95598@harmony.village.org>
In-Reply-To: Your message of "Sun, 20 Jun 1999 22:37:57 %2B0200." <19990620223757.K63035@bitbox.follo.net> 
References:  <19990620223757.K63035@bitbox.follo.net>  <19990620180356.J63035@bitbox.follo.net> <Pine.BSF.4.05.9906201312120.70357-100000@smarter.than.nu> 

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In message <19990620223757.K63035@bitbox.follo.net> Eivind Eklund writes:
: I won't go so far as to say that the introduction of securelevel 4 is
: a regression (it is nice functionality when you want to truly secure a
: box), but it would be much better if it came after having made
: "securelevel" a set of orthogonal switches.

I would go that far, or at least say that it isn't a desirable
progression.  A more general, and useful, feature would be to have
some sysctls that become readonly at secure level 2 or greater.  I
could also be talked into making this a separate sysctl which once set
cannot be unset.

This would allow me to turn off binding of ports, turning on secure
ports, turning other features on/off with a finer toothed comb.  I do
not think that the proposed secure level 4 would materially improve
security and strikes me as a kludge.  I do agree that there needs to
be a secure way to keep it off once off, but secure level 4 isn't it.

Speaking on the implementation issues, it would be sufficient to add a
bit in the type field for the SYSCTL_PROC function.  This bit would be
checked before allowing the sysctl to be written.  That stikes me as a
much more useful way to do this.

This issue was beaten to death in the NetBSD lists recently.  I
believe it was der Mouse that proposed this in (I think)
netbsd-security.

After secure level 2 the desired security features becomes more
orthogonal. 

Warner
FreeBSD security officer.

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