Subject: Re: [PATCH] Smack: replace capable() with ns_capable()
To: "Serge E. Hallyn" <serge@hallyn.com>
References: <1437737174-29451-1-git-send-email-sungbae.yoo@samsung.com>
 <1437738032.2190.2.camel@samsung.com>
 <000001d0c80b$55bdec50$0139c4f0$@samsung.com>
 <55B7936E.2080007@schaufler-ca.com> <20150728150636.GA1656@mail.hallyn.com>
Cc: Sungbae Yoo <sungbae.yoo@samsung.com>,
        "'Lukasz Pawelczyk'" <l.pawelczyk@samsung.com>,
        "'James Morris'" <james.l.morris@oracle.com>,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org,
        Casey Schaufler <casey@schaufler-ca.com>
From: Casey Schaufler <casey@schaufler-ca.com>
Message-ID: <55B7A996.8010704@schaufler-ca.com>
Date: Tue, 28 Jul 2015 09:11:02 -0700
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On 7/28/2015 8:06 AM, Serge E. Hallyn wrote:
> On Tue, Jul 28, 2015 at 07:36:30AM -0700, Casey Schaufler wrote:
>> On 7/26/2015 6:27 PM, Sungbae Yoo wrote:
>>> So, Do you agree to allow the process to change its own labels?
>> No. This requires CAP_MAC_ADMIN. Smack is mandatory access control.
>> Being in a namespace (as they are implemented today) is not sufficient.
> "requires CAP_MAC_ADMIN" should probably read "requires
> CAP_MAC_ADMIN against initial user namespace."  Any unprivileged
> user can unshare a user_ns and get CAP_MAC_ADMIN.

As you say. Since the inode's xattrs are common you need
privilege relative to the initial namespace.

>
> I'm terribly sorry I'm not yet caught up on the smack-lsm thread.
> But intuitively I'd think that you'd want a way for smack policy
> to say "this label is allowed to create a user-ns which will be
> allowed to CAP_MAC_ADMIN", so then smack_capable() can use that
> information to cleanly deny CAP_MAC_ADMIN in namespaces.
>
> -serge
>

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