Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966099AbbBEADN (ORCPT ); Wed, 4 Feb 2015 19:03:13 -0500 Received: from h2.hallyn.com ([78.46.35.8]:40640 "EHLO h2.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755666AbbBEADL (ORCPT ); Wed, 4 Feb 2015 19:03:11 -0500 Date: Thu, 5 Feb 2015 01:03:09 +0100 From: "Serge E. Hallyn" To: Andy Lutomirski Cc: "Serge E. Hallyn" , Christoph Lameter , "Andrew G. Morgan" , Serge Hallyn , Serge Hallyn , Jonathan Corbet , Aaron Jones , "Ted Ts'o" , LSM List , lkml , Andrew Morton Subject: Re: [RFC] Implement ambient capability set. Message-ID: <20150205000309.GA23013@mail.hallyn.com> References: <20150204211617.GA20787@mail.hallyn.com> <20150204212743.GA21475@mail.hallyn.com> <20150204215158.GA21613@mail.hallyn.com> <20150204220211.GB21613@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 Content-Length: 3813 Lines: 85 Quoting Andy Lutomirski (luto@amacapital.net): > On Wed, Feb 4, 2015 at 2:02 PM, Serge E. Hallyn wrote: > > Quoting Serge E. Hallyn (serge@hallyn.com): > >> Quoting Andy Lutomirski (luto@amacapital.net): > >> > On Wed, Feb 4, 2015 at 1:27 PM, Serge E. Hallyn wrote: > >> > > Quoting Andy Lutomirski (luto@amacapital.net): > >> > >> On Wed, Feb 4, 2015 at 1:16 PM, Serge E. Hallyn wrote: > >> > >> > Quoting Andy Lutomirski (luto@amacapital.net): > >> > >> >> On Wed, Feb 4, 2015 at 10:49 AM, Christoph Lameter wrote: > >> > >> >> > + > >> > >> >> > + if (!cap_valid(arg2)) > >> > >> >> > + return -EINVAL; > >> > >> >> > + > >> > >> >> > + new =prepare_creds(); > >> > >> >> > + if (arg3 == 0) > >> > >> >> > + cap_lower(new->cap_ambient, arg2); > >> > >> >> > + else > >> > >> >> > + cap_raise(new->cap_ambient, arg2); > >> > >> >> > + return commit_creds(new); > >> > >> >> > + > >> > >> >> > >> > >> >> This let you add capabilities you don't even have to cap_ambient. I'm > >> > >> >> fine with that as long as the cap evolution rule changes, as above. > >> > >> > > >> > >> > How about if instead we do restrict it to what's in pP? I don't > >> > >> > want CAP_SETPCAP to become a cheap way to get all caps back. With > >> > >> > or without NNP. > >> > >> > >> > >> We'd also have to modify everything that can change pP to change pA as > >> > >> well if we went this route. I'd be okay with that, but it would make > >> > >> the patch much larger, and I'm not entirely sure I see the benefit. > >> > >> It would keep the number of possible states smaller, which could be > >> > >> nice. > >> > > > >> > > Do you mean if we didn't require NNP? I'm suggesting that even if > >> > > we require NNP we should restrict any new bits added to pA to be > >> > > in pP at the prctl call. Then whether or not to drop them from > >> > > pA when they are dropped from pP, I'm not yet certain. > >> > > >> > I mean regardless of whether we require NNP. > >> > > >> > I think that, unless we change the evolution rule, we would need to > >> > drop from pA when bits are dropped from pP to preserve the idea that > >> > dropping bits from pP drops them for good (as long as ruid != 0 or > >> > some securebit is set). > >> > >> Ok, so iiuc the rules would be: > >> > >> 1. must set nnp and have ns_capable(CAP_SETPCAP) to > >> call prctl(PR_SET_AMBIENT_WHATEVER) > >> > >> 2. adding bits to pA requires they be in pP at prctl time > >> > >> 3. dropping bits from pP drops them also from pA > > I'm still unconvinced that 2 and 3 is better than using pP & pA in > execve, but I could go either way on that. > > >> > >> 4. at exec, fP |= pA; pA' = pA > > > > Actually I'm tempted to say that if fP is not empty, then we stick with current > > rules for fP/pP and clear out pA. If fP is empty, then fP = pA > > > > Then, if fP is not empty on the file, we either drop nnp at exec (or > > don't use nnp at all), or we refuse exec if fP > pA. > > We can't drop nnp at exec. > > > > > We definately do not want to run a file which has capability X > > in fP, when X is not in pA. > > Confused. This will break everything, including Christoph's use case. > The status quo for running ping from bash has pA == 0 and fP != 0. Sorry, I meant only if pA is not empty. But it sounds like we've in any case not hit on anything that will actually work for Christoph. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/