From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D2F3C433E1 for ; Wed, 5 Aug 2020 16:27:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19310206DA for ; Wed, 5 Aug 2020 16:27:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727023AbgHEQ1i (ORCPT ); Wed, 5 Aug 2020 12:27:38 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:51340 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726854AbgHEQZf (ORCPT ); Wed, 5 Aug 2020 12:25:35 -0400 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 075FCMQe159374; Wed, 5 Aug 2020 11:17:32 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 32qvn5wm3h-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 05 Aug 2020 11:17:31 -0400 Received: from m0098417.ppops.net (m0098417.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 075FCTrZ160219; Wed, 5 Aug 2020 11:17:31 -0400 Received: from ppma04ams.nl.ibm.com (63.31.33a9.ip4.static.sl-reverse.com [169.51.49.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 32qvn5wm26-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 05 Aug 2020 11:17:31 -0400 Received: from pps.filterd (ppma04ams.nl.ibm.com [127.0.0.1]) by ppma04ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 075FG2rA017045; Wed, 5 Aug 2020 15:17:29 GMT Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by ppma04ams.nl.ibm.com with ESMTP id 32n0184h78-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 05 Aug 2020 15:17:28 +0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 075FHQA927722030 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 5 Aug 2020 15:17:26 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 65909A404D; Wed, 5 Aug 2020 15:17:26 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D9037A4040; Wed, 5 Aug 2020 15:17:24 +0000 (GMT) Received: from li-f45666cc-3089-11b2-a85c-c57d1a57929f.ibm.com (unknown [9.160.95.205]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 5 Aug 2020 15:17:24 +0000 (GMT) Message-ID: <27b7772ef645e10d1fe3cbe56a02d02f42f75db5.camel@linux.ibm.com> Subject: Re: [PATCH v6 1/4] IMA: Add func to measure LSM state and policy From: Mimi Zohar To: Stephen Smalley Cc: Lakshmi Ramasubramanian , Casey Schaufler , Tyler Hicks , sashal@kernel.org, James Morris , linux-integrity@vger.kernel.org, SElinux list , LSM List , linux-kernel Date: Wed, 05 Aug 2020 11:17:24 -0400 In-Reply-To: References: <20200805004331.20652-1-nramas@linux.microsoft.com> <20200805004331.20652-2-nramas@linux.microsoft.com> <4b9d2715d3ef3c8f915ef03867cfb1a39c0abc54.camel@linux.ibm.com> <31d00876438d2652890ab8bf6ba2e80f554ca7a4.camel@linux.ibm.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.28.5 (3.28.5-12.el8) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-08-05_10:2020-08-03,2020-08-05 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 spamscore=0 priorityscore=1501 lowpriorityscore=0 phishscore=0 malwarescore=0 adultscore=0 suspectscore=0 impostorscore=0 mlxlogscore=999 bulkscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008050124 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Wed, 2020-08-05 at 10:27 -0400, Stephen Smalley wrote: > On Wed, Aug 5, 2020 at 9:20 AM Mimi Zohar wrote: > > On Wed, 2020-08-05 at 09:03 -0400, Stephen Smalley wrote: > > > On Wed, Aug 5, 2020 at 8:57 AM Mimi Zohar wrote: > > > > On Wed, 2020-08-05 at 08:46 -0400, Stephen Smalley wrote: > > > > > On 8/4/20 11:25 PM, Mimi Zohar wrote: > > > > > > > > > > > Hi Lakshmi, > > > > > > > > > > > > There's still a number of other patch sets needing to be reviewed > > > > > > before my getting to this one. The comment below is from a high level. > > > > > > > > > > > > On Tue, 2020-08-04 at 17:43 -0700, Lakshmi Ramasubramanian wrote: > > > > > > > Critical data structures of security modules need to be measured to > > > > > > > enable an attestation service to verify if the configuration and > > > > > > > policies for the security modules have been setup correctly and > > > > > > > that they haven't been tampered with at runtime. A new IMA policy is > > > > > > > required for handling this measurement. > > > > > > > > > > > > > > Define two new IMA policy func namely LSM_STATE and LSM_POLICY to > > > > > > > measure the state and the policy provided by the security modules. > > > > > > > Update ima_match_rules() and ima_validate_rule() to check for > > > > > > > the new func and ima_parse_rule() to handle the new func. > > > > > > I can understand wanting to measure the in kernel LSM memory state to > > > > > > make sure it hasn't changed, but policies are stored as files. Buffer > > > > > > measurements should be limited to those things that are not files. > > > > > > > > > > > > Changing how data is passed to the kernel has been happening for a > > > > > > while. For example, instead of passing the kernel module or kernel > > > > > > image in a buffer, the new syscalls - finit_module, kexec_file_load - > > > > > > pass an open file descriptor. Similarly, instead of loading the IMA > > > > > > policy data, a pathname may be provided. > > > > > > > > > > > > Pre and post security hooks already exist for reading files. Instead > > > > > > of adding IMA support for measuring the policy file data, update the > > > > > > mechanism for loading the LSM policy. Then not only will you be able > > > > > > to measure the policy, you'll also be able to require the policy be > > > > > > signed. > > > > > > > > > > To clarify, the policy being measured by this patch series is a > > > > > serialized representation of the in-memory policy data structures being > > > > > enforced by SELinux. Not the file that was loaded. Hence, this > > > > > measurement would detect tampering with the in-memory policy data > > > > > structures after the policy has been loaded. In the case of SELinux, > > > > > one can read this serialized representation via /sys/fs/selinux/policy. > > > > > The result is not byte-for-byte identical to the policy file that was > > > > > loaded but can be semantically compared via sediff and other tools to > > > > > determine whether it is equivalent. > > > > > > > > Thank you for the clarification. Could the policy hash be included > > > > with the other critical data? Does it really need to be measured > > > > independently? > > > > > > They were split into two separate functions because we wanted to be > > > able to support using different templates for them (ima-buf for the > > > state variables so that the measurement includes the original buffer, > > > which is small and relatively fixed-size, and ima-ng for the policy > > > because it is large and we just want to capture the hash for later > > > comparison against known-good). Also, the state variables are > > > available for measurement always from early initialization, whereas > > > the policy is only available for measurement once we have loaded an > > > initial policy. > > > > Ok, measuring the policy separately from other critical data makes > > sense. Instead of measuring the policy, which is large, measure the > > policy hash. > > I think that was the original approach. However, I had concerns with > adding code to SELinux to compute a hash over the policy versus > leaving that to IMA's existing policy and mechanism. If that's > preferred I guess we can do it that way but seems less flexible and > duplicative. Whether IMA or SELinux calculates the in memory policy hash, it should not impact the original purpose of this patch set - measuring critical state. It's unclear whether this patch set needs to be limited to LSM critical state. Measuring the in memory policy, if needed, should be a separate patch set. Mimi