linux-kernel - Re: [patch 1/2] [RFC] Simple tamper-proof device filesystem.

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Message-ID: <54137.81.207.0.53.1197891890.squirrel@secure.samage.net>
Date:	Mon, 17 Dec 2007 12:44:50 +0100 (CET)
From:	"Indan Zupancic" <indan@....nu>
To:	"Tetsuo Handa" <penguin-kernel@...ove.sakura.ne.jp>
Cc:	david@...idnewall.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 1/2] [RFC] Simple tamper-proof device filesystem.

Hi,

On Mon, December 17, 2007 01:40, Tetsuo Handa wrote:
> Hello.
>
> Indan Zupancic wrote:
>> What prevents them from mounting tmpfs on top of /dev, bypassing your fs?
> Mandatory access control (MAC) prevents them from mounting tmpfs on top of
> /dev .
> MAC mediates namespace manipulation requests such as mount()/umount().
>
>> Also, if they have root there are plenty of ways to prevent an administrator
>> from logging in, e.g. using iptables or changing the password.
> MAC mediates execution of /sbin/iptables or /usr/bin/passwd .
>
> So, use of this filesystem alone is meaningless because
> attackers with root privileges can do what you are saying.
> But use of this filesystem with MAC is still valid because
> MAC can prevent attackers with root privileges from doing what you are saying.

If MAC can avoid all that, then why can't it also avoid tampering with /dev?
What security does your filesystem add at all, if it's useless without a MAC
doing
all the hard work?

I think you can better spend your time on read-only bind mounts.

Greetings,

Indan


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