Re: user flags in public temp space (was Re: chflags() [heads up])

From: Doug Harple (dharpleat_private)
Date: Mon Aug 09 1999 - 12:17:49 PDT

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    On Sat, 7 Aug 1999, Darren Reed wrote:
    
    > In some mail from Tim Fletcher, sie said:
    > >
    > > > I think I defeated myself in trying to explain the implementation I was
    > > > trying to describe.  For each user, when they login, a virtual /tmp is
    > > > created and that is shared between all sessions that user has.  This is
    > > > setup at login time and is carried forth to all children, root or not,
    > > > and cannot be reset (somewhat akin to chroot) unless devious methods are
    > > > employed (i.e. write to /dev/mem).
    > > >
    > > > So if I have 10 logins to host foo, each login sees the same /tmp, even
    > > > the root shells I generate via su/sudo in half.  If I login as root, I
    > > > don't have the same /tmp (I get a different one).  cron/at jobs would
    > > > be no different.  So the `real' /tmp could even be 755 root.wheel.
    > >
    > > Although it does rather cripple /tmp in another way: That of sharing
    > > information between users. If I tell another user that the file s/he wants
    > > is in /tmp (as my /home/tim dir is 711 with most files 600) I don't have
    > > to mess with file perms and s/he doesn't have to get the exact right name
    > > to read the file.
    >
    > Why do they need to access your home dir ?  You're making assumptions
    > which you probably shouldn't...
    >
    
    I think perhaps you misread what he was saying.  He's not saying that he
    wants another user to have access to his /home dir.  He is, however,
    saying that a common /tmp makes it possible for him to share files with
    another user without compromising his own security.  If /tmp was assigned
    on a per-user basis, he would be unable to use the /tmp directory in that
    fashion.
    
    ---
    Doug Harple / Community Connect
    dharpleat_private
    



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