linux-kernel - Re: [RFC] capabilities: Ambient capabilities

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Message-ID: <CALCETrUdNp18ZeOC8pRYn_YPUp8nFyH7aS+dFoBf34XNmER-nA@mail.gmail.com>
Date:	Fri, 24 Apr 2015 15:55:08 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	"Ted Ts'o" <tytso@....edu>, "Andrew G. Morgan" <morgan@...nel.org>,
	Andrew Morton <akpm@...uxfoundation.org>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Linux API <linux-api@...r.kernel.org>,
	Austin S Hemmelgarn <ahferroin7@...il.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	Aaron Jones <aaronmdjones@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Markku Savela <msa@...h.iki.fi>,
	Kees Cook <keescook@...omium.org>,
	Jonathan Corbet <corbet@....net>
Subject: Re: [RFC] capabilities: Ambient capabilities

On Apr 24, 2015 2:15 PM, "Serge E. Hallyn" <serge@...lyn.com> wrote:
>
> On Fri, Apr 24, 2015 at 01:18:44PM -0700, Andy Lutomirski wrote:
> > On Fri, Apr 24, 2015 at 1:13 PM, Christoph Lameter <cl@...ux.com> wrote:
> > > On Fri, 24 Apr 2015, Andy Lutomirski wrote:
> > >
> > >> That's sort of what my patch does -- you need CAP_SETPCAP to switch
> > >> the securebit.
> > >>
> > >> But Christoph's patch required it to add caps to the ambient set, right?
> > >
> > > Yes but you seem to be just adding one additional step without too much of
> > > a benefit because you still need CAP_SETPCAP.
> > >
> >
> > No, because I set the default to on :)
>
> Right - I definately prefer
>
> . default off
> . CAP_SETPCAP required to turn it on (for self and children)
> . once on, anyone can copy bits from (whatever we decided) to pA.
>

Why default off?  If there's some weird reason that switching it on
could cause a security problem, then I'd agree, but I haven't spotted
a reason yet.

--Andy
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