Re: [PATCH] Smack: replace capable() with ns_capable()

[Casey Schaufler <casey@schaufler-ca.com>]

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
>