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Date:      Wed, 28 Feb 1996 18:35:36 +1030 (CST)
From:      Michael Smith <msmith@atrad.adelaide.edu.au>
To:        nlawson@kdat.csc.calpoly.edu (Nathan Lawson)
Cc:        newton@communica.com.au, security@freebsd.org
Subject:   Re: Suspicious symlinks in /tmp
Message-ID:  <199602280805.SAA16934@genesis.atrad.adelaide.edu.au>
In-Reply-To: <199602272055.MAA15968@kdat.calpoly.edu> from "Nathan Lawson" at Feb 27, 96 12:55:45 pm

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Nathan Lawson stands accused of saying:
> > 
> > So:  Not only does it not matter who owns the symlink, it also doesn't
> > matter how it is chmod'ed.  You can set its permissions to rwxrwxrwx 
> > without making a spot of difference to the accessibility of the file
> > it's pointing at.
> 
> Yes, but let's say Joe User tries out the ln -s command.  Now he can't delete
> his symlink.  This behavior is broken.  A user should not be able to create
> any type of file, whether a symlink or just a normal file, that is owned
> by another user.

How's that supposed to work?  To create it, he has to have write permissions
in the destination directory; the same are required to delete it.

> Like I said before, how about a justification as to the usefullness of this
> behavior?  I've already provided one annoying result of it.

You haven't.  The alternative behaviour would allow a user to create a symlink
to a protected file, change the permissions on the link, and thus
access the file.  Lose lose lose.

Think of symlinks as a redirection, not a second instance of the file 
(contrast hard links).

> Nate Lawson 

-- 
]] Mike Smith, Software Engineer        msmith@atrad.adelaide.edu.au    [[
]] Genesis Software                     genesis@atrad.adelaide.edu.au   [[
]] High-speed data acquisition and      (GSM mobile) 0411-222-496       [[
]] realtime instrument control          (ph/fax)  +61-8-267-3039        [[
]] Collector of old Unix hardware.      "Where are your PEZ?" The Tick  [[



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