From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753480AbbIJOB0 (ORCPT ); Thu, 10 Sep 2015 10:01:26 -0400 Received: from h2.hallyn.com ([78.46.35.8]:41345 "EHLO h2.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752157AbbIJOBY (ORCPT ); Thu, 10 Sep 2015 10:01:24 -0400 Date: Thu, 10 Sep 2015 09:01:20 -0500 From: "Serge E. Hallyn" To: David Drysdale Cc: "Serge E. Hallyn" , "Eric W. Biederman" , Andy Lutomirski , "linux-kernel@vger.kernel.org" Subject: Re: RFC: fsyscall Message-ID: <20150910140120.GA28071@mail.hallyn.com> References: <874mj4o7yd.fsf@x220.int.ebiederm.org> <8737yomrwm.fsf@x220.int.ebiederm.org> <87mvwwfngy.fsf@x220.int.ebiederm.org> <20150910134350.GC27602@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 10, 2015 at 02:51:28PM +0100, David Drysdale wrote: > On Thu, Sep 10, 2015 at 2:43 PM, Serge E. Hallyn wrote: > > On Tue, Sep 08, 2015 at 07:25:17PM -0500, Eric W. Biederman wrote: > >> Andy Lutomirski writes: > >> > >> > On Tue, Sep 8, 2015 at 4:07 PM, Eric W. Biederman wrote: > >> > >> >> Perhaps I had missed it but I don't recall capsicum being able to wrap > >> >> things like reboot(2). > >> >> > >> > > >> > Ah, so you want to be able to grant BPF-defined capabilities :) > >> > >> Pretty much. > >> > >> Where I am focusing is turning Posix capabilities into real > >> capabilities. I would not mind if the functionality was a bit more > >> general. Say to be able to handle things like security labels, or > >> anywhere else you might reasonably be asked can you do X? > >> > >> But I would be happy if we just managed to wrap the Posix capabilities > >> and turned them into real capablilities. > > > > If there were a clever way to exec an open fd, then you could do this > > execveat(fd, "", argv, envp, AT_EMPTY_PATH) ? ??? I looked for it but I don't have a manpage for it. I see it at man7.org though. Thanks :) > > by passing an fd to a copy of /bin/reboot which has fP=CAP_SYS_BOOT, > > or prefereably fI=CAP_SYS_BOOT,fE=1 and leave pI=CAP_SYS_BOOT in the > > task. > > > > A cleaner way to do this is to have a service which can reboot, which > > looks at unix socket peercreds to determine whether the granter may > > reboot, then passes it an fd which the granter may pass to a grantee. > > Then the grantee passes the fd to the service, which recognizes it and > > reboots. > > > > -serge