linux-kernel - Re: group ownership of tun devices -- nonfunctional?

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Message-ID: <Pine.LNX.4.58.0708201324570.2672@be1.lrz>
Date:	Mon, 20 Aug 2007 13:45:44 +0200 (CEST)
From:	Bodo Eggert <7eggert@....de>
To:	Rene Herman <rene.herman@...e.nl>
cc:	Bodo Eggert <7eggert@....de>, Mike Mohr <akihana@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: group ownership of tun devices -- nonfunctional?

On Mon, 20 Aug 2007, Rene Herman wrote:
> On 08/19/2007 11:42 PM, Bodo Eggert wrote:

> > The intended [my me] semantics is If the user is not
> >  * the allowed user
> > or
> >  * member of the allowed group
> > or
> >  * cabable of CAP_NET_ADMIN
> > then error out. I'm asuming
> 
> There is a short description of the desired semantics in the link that was 
> posted:
> 
> http://lkml.org/lkml/2007/6/18/228
> 
> ===
> The user now is allowed to send packages if either his euid or his egid
> matches the one specified via tunctl (via -u or -g respecitvely). If both
> gid and uid are set via tunctl, both have to match.
> ===
> 
> Paraphrasing the original code above, it's saying:
> 
> if ((owner_is_set && does_not_match) || (group_is_set && does_not_match))
> 	bugger_off_unless(CAP_NET_ADMIN);
> 
> or reverting the logic:
> 
> if ((owner_is_unset || does_match) && (group_is_unset || does_match))
> 	good_to_go();
> 
> which probably matches the intention -- we're good to go only if the 
> credentials that are set also match.

Maybe there are valid reasons to do it this way, but I think having it the 
way I described would be less confusing.

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