RE: IMMUTABLE and APPEND-ONLY rationales

From: Derek Martin (derek@cerberus.ne.mediaone.net)
Date: Sun Jun 25 2000 - 12:24:10 EST


Today, Linda Walsh gleaned this insight:

>
> > -----Original Message-----
> > From: owner-linux-kernel@vger.rutgers.edu
> > [mailto:owner-linux-kernel@vger.rutgers.edu]On Behalf Of Alexander Viro
> >
> > Erm... Folks, let me fill in a detail that seems to be missing here. Dunno
> > about BSDI, but 4.4BSD as it had been released (and {Free,Net,Open}BSD)
> > have more elaborate scheme - they have immutable and user-immutable.
> > Rules looks so: immutable is subject to securelevel limitations,
> > user-immutable is a normal attribute (can be set/reset the same way it is
> > for any other permission bit). Either of them prevents modification/unlinking/
> > renaming/creating a link to. That way one can have the security-enforcing
> > behaviour (normal immutable) _and_ normal users can use it as protection
> > on their files. Root can override the user-immutable (as every other
> > permission bit).
> ---
> This makes alot of sense.
>
> I would guess (?) that an accidental 'rm -fr' by root wouldn't remove
> normal 'immutable' files -- but that they would still be required to
> remove the immutable bit first? If not, root couldn't use user-level
> immutable w/o being afraid that they or a root level program wouldn't
> accidently remove the file same as today...

FWIW, I agree with this wholeheartedly.

-- 
PGP/GPG Public key at http://cerberus.ne.mediaone.net/~derek/pubkey.txt
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Derek D. Martin      |  Unix/Linux Geek
derekm@mediaone.net  |  derek@cerberus.ne.mediaone.net
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