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

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Date:	Tue, 29 May 2007 16:25:54 -0700 (PDT)
From:	david@...g.hm
To:	Pavel Machek <pavel@....cz>
cc:	Crispin Cowan <crispin@...ell.com>, Cliffe <cliffe@...et.net.au>,
	casey@...aufler-ca.com, Kyle Moffett <mrmacman_g4@....com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [AppArmor 01/41] Pass struct vfsmount to the inode_create LSM
 hook

On Tue, 29 May 2007, Pavel Machek wrote:

> Hi!
>
>>> If we want "/etc/shadow" to be the only way to access the shadow file
>>> we could label the data with "/etc/shadow". Any attempts to access
>>> this data using a renamed file or link would be denied (attempts to
>>> link or rename could also be denied).
>> Eloquently put.
>>
>> AppArmor actually does something similar to this, by mediating all of
>> the ways that you can make an alias to a file. These are:
> ...
>>     * Hard links: AppArmor explicitly mediates permission to make a hard
>
> Unfortunately, aparmor is by design limited to subset of distro
> (network daemons). Unfortunately, some other programs (passwd, vi)
> routinely make hardlinks. So AA mediating hardlink is not enough, as
> vi will happily hardlink /etc/shadow into /etc/.vi-shadow-1234.

but with the AA design of default deny this isn't a big problem unless you 
specificly allow some network daemon to access /etc/.vi-shadow-1234

in this context passwd and vi are considered trusted processes, they are 
used _after_ you authenticate onto the box.

no, this won't help you much against local users, but there are a _lot_ of 
boxes out there with few, if any, local users who don't also have the root 
password. AA helps the admin be safer when configuring netwrok daemons.

David Lang
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