Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934147AbbBDWCR (ORCPT ); Wed, 4 Feb 2015 17:02:17 -0500 Received: from h2.hallyn.com ([78.46.35.8]:39139 "EHLO h2.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932735AbbBDWCP (ORCPT ); Wed, 4 Feb 2015 17:02:15 -0500 Date: Wed, 4 Feb 2015 23:02:11 +0100 From: "Serge E. Hallyn" To: "Serge E. Hallyn" Cc: Andy Lutomirski , 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: <20150204220211.GB21613@mail.hallyn.com> References: <20150204211617.GA20787@mail.hallyn.com> <20150204212743.GA21475@mail.hallyn.com> <20150204215158.GA21613@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150204215158.GA21613@mail.hallyn.com> 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: 3116 Lines: 70 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 > > 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 definately do not want to run a file which has capability X in fP, when X is not in pA. > Christoph, would these suffice for your use caes? -- 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/