Message-ID: <434429F2.7030400@perkel.com>
Date: Wed, 05 Oct 2005 12:30:58 -0700
From: Marc Perkel <marc@perkel.com>
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To: Nix <nix@esperi.org.uk>
CC: Lennart Sorensen <lsorense@csclub.uwaterloo.ca>, 7eggert@gmx.de,
       Luke Kenneth Casson Leighton <lkcl@lkcl.net>,
       linux-kernel@vger.kernel.org
Subject: Re: what's next for the linux kernel?
References: <4TiWy-4HQ-3@gated-at.bofh.it> <4U0XH-3Gp-39@gated-at.bofh.it>	<E1EMutG-0001Hd-7U@be1.lrz> <87k6gsjalu.fsf@amaterasu.srvr.nix>	<4343E611.1000901@perkel.com>	<20051005144441.GC8011@csclub.uwaterloo.ca>	<4343E7AC.6000607@perkel.com>	<20051005145606.GA7949@csclub.uwaterloo.ca>	<4343EC6A.70603@perkel.com> <874q7vhj0c.fsf@amaterasu.srvr.nix>
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Nix wrote:

>On Wed, 05 Oct 2005, Marc Perkel yowled:
>  
>
>>Agian - thinking outside the box.
>>    
>>
>
>I hate that phrase. There is no `box'.
>
>  
>
That's what it looks like when you are inside it.

>>If the permissions were don'e right in your own directories your
>>inherited rights would give your permissions automatically to your
>>home directory and all directories uner it. Netware has a concept
>>called an inherited rights mask - something Linux lacks. Windows also
>>has rights like this and Samba emulates it. So unless root put files
>>in your directory and specifically denied you rights to them, you
>>would have full rights to your own directory.
>>    
>>
>
>So, um, what happens to these permissions when you copy a file and put
>it somewhere else? Do the inherited rights go with it or not? In Unix
>it's pretty intuitive. In this system there seem to be two right
>answers, both of which seem... risky from a security perspective.
>  
>
You inherit the rights of the new directory.

Also - under Netware not all permissions are stored with the file. The 
rights are calculated from the file heirachy so you don't store a lot of 
data with each file unless the file has permissions set that is 
different than that of the directory it's in. So moving a file to 
someone's home directory doesn't require any permissions to be set to 
give the user rights to the file.

>  
>
>>However - if you were browsing the /etc directory and there were files
>>there that you had no read or write access to - then you wouldn't even
>>be able to list them.
>>    
>>
>
>/tmp is the problem here, and shows the futility and pointlessness of
>this feature. If you have an unlistable file in /tmp, *its name is still
>determinable*, because other users cannot create files with that
>name. The concept adds *nothing* over some combination of dirs with the
>execute bit cleared for some set of users and subdirectories which
>cannot be read by some set of users. There's no need for this profoundly
>non-Unixlike permission at all. (As usual, ACLs make managing this on
>a fine-grained scale rather easier.)
>
>  
>
It doesn't really make sense to use the /tmp directory the way Unix uses 
it. Why would you want just anyone to even know the names of the 
temporary files you are using. Users should have their own temp 
directory or create their own directory within /tmp

But - to address your question - if there were an invisible (to you) 
file in a directory that you had create rights to then you would get a 
file creation error.

>>                      If you went to the home directory and lets say
>>everyone had 700 permissions on all the directories withing home, you
>>would only see your own directory. You wouldn't even be able to know
>>what other directories existed there.
>>    
>>
>
>This is what per-process filesystems are for.
>
>  
>
>>If you want to start thinking about DOING IT RIGHT you need to think
>>beyond the Unix model and start looking at Netware. Maybe in 5 years
>>Linux will evolve to where Netware was in 1990.
>>    
>>
>
>I think Plan 9 is a better goal than Netware. At least it was designed
>by people aiming for a better Unix rather than people trying to build a
>better DOS, and so is more likely to have a compatible philosophy.
>
>  
>
I'm not familiar with Plan 9.

>>Unix permissions totally suck but it's old baggage that you're stuck
>>with somewhat. Are you going to be stuck forever and is Linux ever
>>going to grow up and move on to better things? Linux is crippled when
>>it comes to permissions.
>>    
>>
>
>Well, you can't change it drastically without violating POSIX. There's
>no damned way Linux is going to do *that*.
>
>  
>
>>                         The Windows people are laughing at you and
>>you don't even get it why they are laughing.
>>    
>>
>
>You *do* realise just how incapable the Windows permission-management
>GUI is, don't you? Any OS where the command-line tools hide half
>the permissions model and the GUI hides a slightly different half,
>and where looking at a set of permissions and hitting cancel can
>*change* those permissions drastically, is not sane.
>  
>
That's why I'm pushing netware as a model rather than windows. But 
Windows file permissions are superior to Linux.

>(Disclaimer: the last time I bothered to verify the latter behaviour
>was in NT4. Maybe they've partially fixed it.)
>
>  
>

One place where Windows wins over Linux is in the "easy to use" 
category. Something the Linux world should look ast.

I am a Linux supporter and love it. I'm saying this to help make it better.

-- 
Marc Perkel - marc@perkel.com

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    My Blog: http://marc.perkel.com

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