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Date:      Wed, 29 Feb 2012 08:00:21 -0700
From:      Ian Lepore <freebsd@damnhippie.dyndns.org>
To:        jb <jb.1234abcd@gmail.com>
Cc:        freebsd-current@freebsd.org
Subject:   Re: negative group permissions?
Message-ID:  <1330527621.1023.27.camel@revolution.hippie.lan>
In-Reply-To: <loom.20120229T141955-30@post.gmane.org>
References:  <20120228092244.GB48977@mech-cluster241.men.bris.ac.uk> <loom.20120228T155607-690@post.gmane.org> <20120228162447.GB58311@mech-cluster241.men.bris.ac.uk> <20120229072458.GA95427@DataIX.net> <20120229085716.GA66484@mech-cluster241.men.bris.ac.uk> <loom.20120229T111136-48@post.gmane.org> <loom.20120229T141955-30@post.gmane.org>

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On Wed, 2012-02-29 at 13:21 +0000, jb wrote:
> jb <jb.1234abcd <at> gmail.com> writes:
> 
> > ... 
> > I would suggest (if you can) that you change the .seq permissions to 0664 and
> > watch what happens to it - the purpose is to narrow down who/what changed its
> > mode.
> > Some history. logs. and some ad hoc "watch script" would do it.
> 
> Take a look at "notify" feature (file, dir, event).
> http://www.freebsd.org/cgi/ports.cgi?query=notify&stype=all
> jb

I don't understand why everyone is focused on the 641 mode the file ends
up with.  The code creates the file using 0661, and under a umask of 022
you end up with a file with 0641 permissions.  How the write bit
disppeared from the group permissions doesn't seem to be germane to the
real question of why the code specifies world-exec access.  

I don't think it's a legitimate attempt to leverage the negative
permissions quirk, because it doesn't effectively do so.  It's not a
directory or executable file in the first place, so making it executable
for everyone except the owner and group is not some sort of subtle
security trick, it's just meaningless.  I think the code is long overdue
for a fix to 0660 permissions when creating the file.

-- Ian





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