Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966681AbbBDP40 (ORCPT ); Wed, 4 Feb 2015 10:56:26 -0500 Received: from h2.hallyn.com ([78.46.35.8]:33672 "EHLO h2.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966247AbbBDP4V (ORCPT ); Wed, 4 Feb 2015 10:56:21 -0500 Date: Wed, 4 Feb 2015 16:56:17 +0100 From: "Serge E. Hallyn" To: Christoph Lameter Cc: "Andrew G. Morgan" , "Serge E. Hallyn" , Serge Hallyn , Serge Hallyn , Andy Lutomirski , Jonathan Corbet , Aaron Jones , "Ted Ts'o" , linux-security-module@vger.kernel.org, lkml , akpm@linuxfoundation.org Subject: Re: [capabilities] Allow normal inheritance for a configurable set of capabilities Message-ID: <20150204155617.GE16726@mail.hallyn.com> References: <20150202171257.GD24351@ubuntumail> <20150203155544.GE2923@mail.hallyn.com> <20150203172653.GB4748@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: 2426 Lines: 57 Quoting Christoph Lameter (cl@linux.com): > On Wed, 4 Feb 2015, Andrew G. Morgan wrote: > > > I'm not generally in favor of this. Mostly because this seems to be a > > mini-root kind of inheritance that propagates privilege to binaries > > that aren't prepared for privilege. I don't really buy the mmap code > > concern because the model as it stands says that you trust the binary > > (and all of the various ways it was programmed to execute code) with > > specific privileges. If the binary mmap's some code (PAM modules come > > to mind) then that is part of what it was programmed to/allowed to do. > > > > That being said, if you really really want this kind of thing, then > > make it a single secure bit (with another lock on/off bit) which, when > > set, makes: fI default to X. > > > > pP' = (X & fP) | (pI & fI) > > > > That way the per-process bounding set still works as advertised and > > you don't need to worry about the existing semantics being violated. > > Ok but then also fI needs to be set to X so that the binary f invokes > can also inherit. So if we copy the inheritable flags to fI then we > wont be needing the bounding set anymore. > > The changes to brpm_caps_from_vfs_cap would then > be only the following? (substitute capable(CAP_INHERIT_BY_DEFAULT through > any other means like PRCTL if wanted). > > > Index: linux/security/commoncap.c > =================================================================== > --- linux.orig/security/commoncap.c 2015-02-04 09:44:25.000000000 -0600 > +++ linux/security/commoncap.c 2015-02-04 09:45:59.381572756 -0600 > @@ -350,6 +350,9 @@ static inline int bprm_caps_from_vfs_cap > __u32 permitted = caps->permitted.cap[i]; > __u32 inheritable = caps->inheritable.cap[i]; > > + if (capable(CAP_INHERIT_BY_DEFAULT) > + new->cap_inheritable.cap[i] = inheritable; > + > /* > * pP' = (X & fP) | (pI & fI) > */ Not quite - I think more like if (secure(SECURE_AMBIENT_PRIVS)) new->cap_inheritable.cap[i] = inheritable; Then ns_capable(CAP_INHERIT_BY_DEFAULT), or perhaps rather ns_capable(CAP_SETPCAP), would be required in order to set SECURE_AMBIENT_PRIVS, which is off by default. -- 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/