Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966663AbbBDQMI (ORCPT ); Wed, 4 Feb 2015 11:12:08 -0500 Received: from mail-yh0-f52.google.com ([209.85.213.52]:64268 "EHLO mail-yh0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965355AbbBDQMG (ORCPT ); Wed, 4 Feb 2015 11:12:06 -0500 MIME-Version: 1.0 In-Reply-To: <20150204155617.GE16726@mail.hallyn.com> References: <20150202171257.GD24351@ubuntumail> <20150203155544.GE2923@mail.hallyn.com> <20150203172653.GB4748@mail.hallyn.com> <20150204155617.GE16726@mail.hallyn.com> Date: Wed, 4 Feb 2015 08:12:04 -0800 X-Google-Sender-Auth: 4esiwLafdEwrwfuB18hapTzrJxw Message-ID: Subject: Re: [capabilities] Allow normal inheritance for a configurable set of capabilities From: "Andrew G. Morgan" To: "Serge E. Hallyn" Cc: Christoph Lameter , Serge Hallyn , Serge Hallyn , Andy Lutomirski , Jonathan Corbet , Aaron Jones , "Ted Ts'o" , linux-security-module@vger.kernel.org, lkml , akpm@linuxfoundation.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2978 Lines: 73 I was thinking more like this: int override = secure(SECURE_AMBIENT_PRIVS) && cap_isclear(caps->inheritable.cap); CAP_FOR_EACH_U32(i) { __u32 permitted = caps->permitted.cap[i]; __u32 inheritable = override ? new->cap_bset.cap[i] : caps->inheritable.cap[i]; [...] Cheers Andrew On Wed, Feb 4, 2015 at 7:56 AM, Serge E. Hallyn wrote: > 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/