linux-kernel - Re: chroot(2) and bind mounts as non-root

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Date:	Tue, 20 Dec 2011 16:23:30 -0500
From:	Colin Walters <walters@...bum.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	LKML <linux-kernel@...r.kernel.org>, alan@...rguk.ukuu.org.uk,
	morgan@...nel.org, luto@....edu, kzak@...hat.com,
	Steve Grubb <sgrubb@...hat.com>
Subject: Re: chroot(2) and bind mounts as non-root

On Sun, 2011-12-18 at 16:55 -0800, Eric W. Biederman wrote:

> I expect by the time this makes it to "out of the box" experiences on
> enterprise distros, useradd and friends will be giving out 1000 or so uids
> to new accounts.

Hmm...how would that work?  Would it be something that would happen at
PAM time, like a module that looks up some file in /etc and says "OK
this uid gets this range" and uploads that to the kernel? 

This whole idea of a normal uid getting *other* slave uids is cool but
scary at the same time.  So much infrastructure in what I think of as
"General Purpose Linux"[1] is built up around a uid - resource
restrictions and authentication for example.

I guess as long as we're sure that all cases where a "uid" crosses a
user namespace (say socket credentials) and appears as the right thing,
it may be secure.

> I think the user namespace will do what you need. Certainly it appears
> that everything in your example binary will be allowed by the time it is
> done.

That's cool, I will keep an eye on what you guys are doing.  Looks like
the containers list on linuxfoundation.org is the right one to follow?

[1] The code that's shared between RHEL and Debian roughly between the
kernel and GNOME, discarding the pointless "packaging" differences

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