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From: "Hr.Ladavac" <lada@ws2301.gud.siemens.co.at>
Message-Id: <199611280955.AA040424941@ws2301.gud.siemens.co.at>
Subject: Re: looking for an idea
To: julian@whistle.com (Julian Elischer)
Date: Thu, 28 Nov 1996 10:55:41 +0100 (MEZ)
Cc: lada@ws2301.gud.siemens.co.at, wpaul@skynet.ctr.columbia.edu,
        terry@lambert.org, sprice@hiwaay.net, hackers@freebsd.org
In-Reply-To: <329CBC11.59E2B600@whistle.com> from "Julian Elischer" at Nov 27, 96 02:09:21 pm
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E-mail message from Julian Elischer contained:
> Hr.Ladavac wrote:
> > 
> > E-mail message from Julian Elischer contained:
> > > Bill Paul wrote:
> > > >
> > > >
> > > If YOU ( the server) are root....
> > >
> > > make a file owned by them mode 400
> > > require them to open it and send you the file descriptor via AF_UNIX
> > >
> > > check it matches..
> > > if it does, then
> > > 1/ the are themselves
> > > or
> > > 2/ they are root (game over)
> > 
> > Or
> >         3) they made a hard link, opened that, and sent you the
> >            file descriptor.
> 
> hard links have the same ownership as the original!

You're right--silly me :(
> and only the owner can make one anyhow, so

Not on HP-UX; anyone with the write access to any directory on the same
filesystem can do it but it doesn't help them: they still have to be
either root or the owner in order to open it or chmod it.

So, yes, your solution is okay for the server-is-root case.  Anyone sees
some real problems with that?

/Marino
> they have to be the correct user to do this....
> 
> > 
> >            The only protection agains that is a partition writable only
> >            by root where these files are to live--almost as bad as
> >            procfs.
> > 
> > /Marino
>