netdev - Re: [PATCH] netfilter: xt_condition: add security capability support

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Date:	Wed, 25 Aug 2010 11:04:09 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	Luciano Coelho <luciano.coelho@...ia.com>
cc:	ext Changli Gao <xiaosuo@...il.com>,
	"kaber@...sh.net" <kaber@...sh.net>,
	"netfilter-devel@...r.kernel.org" <netfilter-devel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>
Subject: Re: [PATCH] netfilter: xt_condition: add security capability
 support


On Wednesday 2010-08-25 09:09, Luciano Coelho wrote:
>> 
>> Indeed so. But you did not invent any new interface. You are reusing
>> files, which can be protected by DAC modes, or LSMs doing
>> funky-stuff. xt_{condition,recent,..} already implement file modes,
>> but does it check for it? Well no, because fs/namei.c does it for
>> them. As for LSMs, well, I hope they do cater for testing for
>> capability bits.
>
>I dug deeper into the code and I can see that /sys/net has capability
>checks (implemented in netdev_store() in net-sysfs.c) and nobody without
>CAP_NET_ADMIN will be able to write to the files there.  But in procfs I
>couldn't see anything similar and anyone with file write permissions can
>modify the files in /proc/net/*.

I did not say there was. fs/ will handle the DAC part, and if you
wanted MAC/capability checking/other sparkles, an LSM sounds like
the right spot.
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