linux-kernel - Re: [PATCH 2/2] groups: Allow unprivileged processes to use setgroups to drop groups

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Date:	Mon, 17 Nov 2014 17:11:57 -0500
From:	"Eric W.Biederman" <ebiederm@...ssion.com>
To:	Andy Lutomirski <luto@...capital.net>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
CC:	linux-man <linux-man@...r.kernel.org>, Ted Ts'o <tytso@....edu>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>,
	Josh Triplett <josh@...htriplett.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux API <linux-api@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 2/2] groups: Allow unprivileged processes to use setgroups to drop groups



On November 17, 2014 1:07:30 PM EST, Andy Lutomirski <luto@...capital.net> wrote:
>On Nov 17, 2014 3:37 AM, "One Thousand Gnomes"
><gnomes@...rguk.ukuu.org.uk> wrote:
>>
>> > optional), I can do that too.  The security model of "having a
>group
>> > gives you less privilege than not having it" seems crazy, but
>> > nonetheless I can see a couple of easy ways that we can avoid
>breaking
>>
>> It's an old pattern of use that makes complete sense in a traditional
>> Unix permission world because it's the only way to do "exclude
>{list}"
>> nicely. Our default IMHO shouldn't break this.
>>
>> > that pattern, no_new_privs being one of them.  I'd like to make
>sure
>> > that nobody sees any other real-world corner case that unprivileged
>> > setgroups would break.
>>
>> Barring the usual risk of people doing improper error checking I
>don't
>> see one immediately.
>>
>> For containers I think it actually makes sense that the sysctl can be
>> applied per container anyway.
>
>We'll probably need per container sysctls some day.

We already have a mess of per network namespace sysctls,
as well as few for other namespaces.

We have the infrastructure it is just a matter of using it for whatever purpose we need.

Eric

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