From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:39374 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751878AbdJYRS0 (ORCPT ); Wed, 25 Oct 2017 13:18:26 -0400 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v9PHHfli066402 for ; Wed, 25 Oct 2017 13:18:26 -0400 Received: from e06smtp12.uk.ibm.com (e06smtp12.uk.ibm.com [195.75.94.108]) by mx0a-001b2d01.pphosted.com with ESMTP id 2dtxfnset3-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 25 Oct 2017 13:18:25 -0400 Received: from localhost by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 25 Oct 2017 18:18:23 +0100 Subject: Re: [PATCH v3 2/2] ima: check signature enforcement against cmdline param instead of CONFIG From: Mimi Zohar To: "Bruno E. O. Meneguele" Cc: linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, serge@hallyn.com, james.l.morris@oracle.com, dmitry.kasatkin@gmail.com, rusty@rustcorp.com.au, jeyu@kernel.org Date: Wed, 25 Oct 2017 13:18:17 -0400 In-Reply-To: <20171025150544.GC26762@glitch> References: <1508885697.3164.5.camel@linux.vnet.ibm.com> <20171025150544.GC26762@glitch> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Message-Id: <1508951897.7367.16.camel@linux.vnet.ibm.com> Sender: linux-integrity-owner@vger.kernel.org List-ID: On Wed, 2017-10-25 at 13:05 -0200, Bruno E. O. Meneguele wrote: > On 24-10, Mimi Zohar wrote: > > On Tue, 2017-10-24 at 15:37 -0200, Bruno E. O. Meneguele wrote: > > > When the user requests MODULE_CHECK policy and its kernel is compiled > > > with CONFIG_MODULE_SIG_FORCE not set, all modules would not load, just > > > those loaded in initram time. One option the user would have would be > > > set a kernel cmdline param (module.sig_enforce) to true, but the IMA > > > module check code doesn't rely on this value, it checks just > > > CONFIG_MODULE_SIG_FORCE. > > > > > > This patch solves this problem checking for the exported value of > > > module.sig_enforce cmdline param intead of CONFIG_MODULE_SIG_FORCE, > > > which holds the effective value (CONFIG || param). > > > > > > Signed-off-by: Bruno E. O. Meneguele > > > --- > > > security/integrity/ima/ima_main.c | 6 +++--- > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c > > > index e4ab8ef8016e..d11a7fcc5c8b 100644 > > > --- a/security/integrity/ima/ima_main.c > > > +++ b/security/integrity/ima/ima_main.c > > > @@ -356,12 +356,12 @@ void ima_post_path_mknod(struct dentry *dentry) > > > */ > > > int ima_read_file(struct file *file, enum kernel_read_file_id read_id) > > > { > > > + bool sig_enforce = is_module_sig_enforced(); > > > + > > > if (!file && read_id == READING_MODULE) { > > > > The only reason for getting here is that you're using the old module > > load syscall. Is there a reason for not using the new one, which > > passes the file descriptor? > Basicaly because the way kmod handles compressed (gz/xz) modules. The > way it's today would require major changes in the code or some kind of > memfd_create() + xattrs reassignement in order to finit_module() be used > correctly. > > Considering it would take some time to be accepted or even to figure out > the correct way to tackle it, the current IMA module check code works > aside kernel module signature validation, which is fine for now for me, > but has the problem that this patch tries to solve in the > CONFIG_MODULE_SIG_FORCE check (ignoring module.sig_enforce cmdline > param). Thank you for the reasoning. BTW, these patches are now queued. > > > -#ifndef CONFIG_MODULE_SIG_FORCE > > > - if ((ima_appraise & IMA_APPRAISE_MODULES) && > > > + if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) && > > > (ima_appraise & IMA_APPRAISE_ENFORCE)) > > > return -EACCES; /* INTEGRITY_UNKNOWN */ > > > -#endif > > > return 0; /* We rely on module signature checking */ > > > } > > > return 0; > > > > >