From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934693Ab3BSWKK (ORCPT ); Tue, 19 Feb 2013 17:10:10 -0500 Received: from e7.ny.us.ibm.com ([32.97.182.137]:34646 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933538Ab3BSWKI (ORCPT ); Tue, 19 Feb 2013 17:10:08 -0500 Message-ID: <1361310864.13508.20.camel@falcor1.watson.ibm.com> Subject: Re: [PATCH 2/2] ima: Support appraise_type=imasig_optional From: Mimi Zohar To: Vivek Goyal Cc: "Kasatkin, Dmitry" , linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 19 Feb 2013 16:54:24 -0500 In-Reply-To: <20130218182114.GB25922@redhat.com> References: <20130212185725.GC23410@redhat.com> <20130213132920.GA3540@redhat.com> <20130213143807.GC3540@redhat.com> <20130213153013.GB6750@redhat.com> <1360794421.3524.495.camel@falcor1.watson.ibm.com> <20130214150303.GA16671@redhat.com> <1360855815.3524.615.camel@falcor1.watson.ibm.com> <20130218182114.GB25922@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 (3.2.3-3.fc16) Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13021922-5806-0000-0000-00001FDD261B Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2013-02-18 at 13:21 -0500, Vivek Goyal wrote: > On Thu, Feb 14, 2013 at 10:30:15AM -0500, Mimi Zohar wrote: > > On Thu, 2013-02-14 at 10:03 -0500, Vivek Goyal wrote: > > > On Wed, Feb 13, 2013 at 05:27:01PM -0500, Mimi Zohar wrote: > > > > > > [..] > > > > > Yep, I got that. Default policy gets overruled when a new policy is > > > > > loaded. > > > > > > > > > > In secureboot mode, somehow above rule needs to take effect by default. > > > > > One option would be that kernel can enforce above rule. > > > > > (I guess by adding it to both default_list as well as policy list). > > > > > > > > The default policy is empty, but can be replaced with boot command line > > > > options. The existing options are ima_tcb and/ ima_appraise_tcb. > > > > Please feel free to define an additional policy. > > > > > > I think just defining a new command line option is not sufficient > > > for secureboot use case. > > > > > > - One can easily remove kernel command line option without breaking > > > booting and easily bypass secureboot restrictions. > > > > > - I guess this is one mandated rule by secureboot. There might still > > > be a user policy which can co-exist with this rule. > > > > > > So to me this is not a new policy. It is just one mandatory rule which > > > gets appended to any policy in secureboot mode. Think of it as mandatory > > > rule imposed by kernel for any policy user can define. And in secureboot > > > mode a user can not get rid of this rule. (Otherwise it breaks user > > > space signing and one can bypass secureboot and boot into unsigned > > > kernel). > > > > Your rule allows both signed and unsigned files to be executed. Signed > > files will just have more capabilities. The ima_appraise_tcb option > > requires all files owned by root to be signed, otherwise access is > > denied. The two policies simply can not co-exist. > > Thinking loud. I guess we might have to extend ima policy/rules to allow > multiple appraise rules to co-exist. And access permission will finally > depend on if all the rules in same category return success. ima_appraise_tcb rules: dont_appraise fsmagic=PROC_SUPER_MAGIC . . . dont_appraise fsmagic=SELINUX_MAGIC appraise fowner=0 ima_secureboot: appraise fowner=0 func=bprm appraise_type=optional The ima_appraise_tcb appraise rule includes everything that would match the ima_secureboot rule. It isn't possible to combine the two policies. Mimi