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

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Message-ID: <CALCETrW9ckw=7-1JSyFkenhFu2_1MvVqjA+inOmsuuWemGaU0w@mail.gmail.com>
Date:	Mon, 30 Mar 2015 07:31:22 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Andrew Lutomirski <luto@...nel.org>,
	"Ted Ts'o" <tytso@....edu>,
	Andrew Morton <akpm@...uxfoundation.org>,
	"Andrew G. Morgan" <morgan@...nel.org>,
	Linux API <linux-api@...r.kernel.org>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Austin S Hemmelgarn <ahferroin7@...il.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	Aaron Jones <aaronmdjones@...il.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Markku Savela <msa@...h.iki.fi>,
	Kees Cook <keescook@...omium.org>,
	Jonathan Corbet <corbet@....net>
Subject: Re: [RFC] capabilities: Ambient capabilities

On Mar 30, 2015 7:55 AM, "Christoph Lameter" <cl@...ux.com> wrote:
>
> On Sat, 14 Mar 2015, Andrew G. Morgan wrote:
>
> >
> > I thought I did. Please implement a lockable secure bit and I will
>
> Would this suffice? It puts the CAP_SETPCAP limitation back to how it
> was in my earlier patch.
>

I really don't like that variant.  CAP_SETPCAP is dangerous and so
absurdly powerful that people really shouldn't hand it out.

I'll submit a new version this week with the securebits.  Sorry for the delay.

--Andy

>
>
> Subject: ambient caps: Allow disabling with SETPCAP
>
> Do not allow setting ambient caps if CAP_SETPCAP is not set.
>
> Signed-off-by: Christoph Lameter <cl@...ux.com>
>
> Index: linux/security/commoncap.c
> ===================================================================
> --- linux.orig/security/commoncap.c
> +++ linux/security/commoncap.c
> @@ -962,6 +962,9 @@ int cap_task_prctl(int option, unsigned
>                 if (((!cap_valid(arg3)) | arg4 | arg5))
>                         return -EINVAL;
>
> +               if (!ns_capable(current_user_ns(), CAP_SETPCAP))
> +                       return -EPERM;
> +
>                 if (arg2 == PR_CAP_AMBIENT_GET) {
>                         return !!cap_raised(current_cred()->cap_ambient, arg3);
>                 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
--
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