linux-kernel - Re: [AppArmor 01/41] Pass struct vfsmount to the inode

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Message-Id: <B4A3C582-68F9-4077-B058-03B79A5577EB@mac.com>
Date:	Sat, 26 May 2007 01:20:50 -0400
From:	Kyle Moffett <mrmacman_g4@....com>
To:	casey@...aufler-ca.com
Cc:	Andreas Gruenbacher <agruen@...e.de>,
	James Morris <jmorris@...ei.org>, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [AppArmor 01/41] Pass struct vfsmount to the inode_create LSM hook

On May 24, 2007, at 14:58:41, Casey Schaufler wrote:
> On Fedora zcat, gzip and gunzip are all links to the same file.  I  
> can imagine (although it is a bit of a stretch) allowing a set of  
> users access to gunzip but not gzip (or the other way around).

That is a COMPLETE straw-man argument.  I can override your "check"  
with this absolutely trivial perl code:

exec { "/usr/bin/gunzip" } "gzip", "-9", "some/file/to.gz";

Pathname-based checks are pretty fundamentally insecure.  If you want  
to protect a "name", then you should tag the "name" with security  
attributes (IE: AppArmor).  On the other hand, if you actually want  
to protect the _data_, then tagging the _name_ is flawed; tag the  
*DATA* instead.

Cheers,
Kyle Moffett

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