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Tue, 12 Jan 2021 13:25:14 -0500 X-MC-Unique: kWs__zQOOj2JdUs2RA0VDA-1 Received: from [192.168.0.104] (c-73-42-176-67.hsd1.wa.comcast.net [73.42.176.67]) by linux.microsoft.com (Postfix) with ESMTPSA id 7792220B6C40; Tue, 12 Jan 2021 10:25:11 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 7792220B6C40 To: Paul Moore , Tushar Sugandhi References: <20210108040708.8389-1-tusharsu@linux.microsoft.com> <20210108040708.8389-9-tusharsu@linux.microsoft.com> From: Lakshmi Ramasubramanian Message-ID: <1b076701-3af8-6997-82ae-7196c263a7f4@linux.microsoft.com> Date: Tue, 12 Jan 2021 10:25:11 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-loop: dm-devel@redhat.com X-Mailman-Approved-At: Wed, 13 Jan 2021 09:20:09 -0500 Cc: sashal@kernel.org, dm-devel@redhat.com, snitzer@redhat.com, selinux@vger.kernel.org, Stephen Smalley , James Morris , zohar@linux.ibm.com, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, tyhicks@linux.microsoft.com, casey@schaufler-ca.com, linux-integrity@vger.kernel.org, gmazyland@gmail.com, agk@redhat.com Subject: Re: [dm-devel] [PATCH v10 8/8] selinux: include a consumer of the new IMA critical data hook X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" On 1/12/21 8:27 AM, Paul Moore wrote: > On Thu, Jan 7, 2021 at 11:07 PM Tushar Sugandhi > wrote: >> From: Lakshmi Ramasubramanian >> >> SELinux stores the active policy in memory, so the changes to this data >> at runtime would have an impact on the security guarantees provided >> by SELinux. Measuring in-memory SELinux policy through IMA subsystem >> provides a secure way for the attestation service to remotely validate >> the policy contents at runtime. >> >> Measure the hash of the loaded policy by calling the IMA hook >> ima_measure_critical_data(). Since the size of the loaded policy >> can be large (several MB), measure the hash of the policy instead of >> the entire policy to avoid bloating the IMA log entry. >> >> To enable SELinux data measurement, the following steps are required: >> >> 1, Add "ima_policy=critical_data" to the kernel command line arguments >> to enable measuring SELinux data at boot time. >> For example, >> BOOT_IMAGE=/boot/vmlinuz-5.10.0-rc1+ root=UUID=fd643309-a5d2-4ed3-b10d-3c579a5fab2f ro nomodeset security=selinux ima_policy=critical_data >> >> 2, Add the following rule to /etc/ima/ima-policy >> measure func=CRITICAL_DATA label=selinux >> >> Sample measurement of the hash of SELinux policy: >> >> To verify the measured data with the current SELinux policy run >> the following commands and verify the output hash values match. >> >> sha256sum /sys/fs/selinux/policy | cut -d' ' -f 1 >> >> grep "selinux-policy-hash" /sys/kernel/security/integrity/ima/ascii_runtime_measurements | tail -1 | cut -d' ' -f 6 >> >> Note that the actual verification of SELinux policy would require loading >> the expected policy into an identical kernel on a pristine/known-safe >> system and run the sha256sum /sys/kernel/selinux/policy there to get >> the expected hash. >> >> Signed-off-by: Lakshmi Ramasubramanian >> Suggested-by: Stephen Smalley >> Reviewed-by: Tyler Hicks >> --- >> Documentation/ABI/testing/ima_policy | 3 +- >> security/selinux/Makefile | 2 + >> security/selinux/ima.c | 64 ++++++++++++++++++++++++++++ >> security/selinux/include/ima.h | 24 +++++++++++ >> security/selinux/include/security.h | 3 +- >> security/selinux/ss/services.c | 64 ++++++++++++++++++++++++---- >> 6 files changed, 149 insertions(+), 11 deletions(-) >> create mode 100644 security/selinux/ima.c >> create mode 100644 security/selinux/include/ima.h > > I remain concerned about the possibility of bypassing a measurement by > tampering with the time, but I appear to be the only one who is > worried about this so I'm not going to block this patch on those > grounds. > > Acked-by: Paul Moore Thanks Paul. -lakshmi -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel 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=-24.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=ham 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 7D324C433E0 for ; Tue, 12 Jan 2021 18:25:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 476602311D for ; Tue, 12 Jan 2021 18:25:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406325AbhALSZx (ORCPT ); Tue, 12 Jan 2021 13:25:53 -0500 Received: from linux.microsoft.com ([13.77.154.182]:34916 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391199AbhALSZw (ORCPT ); Tue, 12 Jan 2021 13:25:52 -0500 Received: from [192.168.0.104] (c-73-42-176-67.hsd1.wa.comcast.net [73.42.176.67]) by linux.microsoft.com (Postfix) with ESMTPSA id 7792220B6C40; Tue, 12 Jan 2021 10:25:11 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 7792220B6C40 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1610475911; bh=qy3ti2dFqNqzP6FP7vg6YhFp5uWu+v5fID15lyNEIuw=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=eKZLZ8Sgxg1EPb8LG5UCoPzpgpSvDYjqzZiuualeGjnsgxXxl3SherhBga/kP7ANP ej7DuYEWImAjRGsusPXz+nj/LZ3ydA9wQyUnhSNCZkPqhtfSDp58m6w5F6PYm1fSNe BbcDvx2wKTWMa/WiQNYpbpUwOJybcWnLkwIozeEg= Subject: Re: [PATCH v10 8/8] selinux: include a consumer of the new IMA critical data hook To: Paul Moore , Tushar Sugandhi Cc: zohar@linux.ibm.com, Stephen Smalley , casey@schaufler-ca.com, agk@redhat.com, snitzer@redhat.com, gmazyland@gmail.com, tyhicks@linux.microsoft.com, sashal@kernel.org, James Morris , linux-integrity@vger.kernel.org, selinux@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com References: <20210108040708.8389-1-tusharsu@linux.microsoft.com> <20210108040708.8389-9-tusharsu@linux.microsoft.com> From: Lakshmi Ramasubramanian Message-ID: <1b076701-3af8-6997-82ae-7196c263a7f4@linux.microsoft.com> Date: Tue, 12 Jan 2021 10:25:11 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On 1/12/21 8:27 AM, Paul Moore wrote: > On Thu, Jan 7, 2021 at 11:07 PM Tushar Sugandhi > wrote: >> From: Lakshmi Ramasubramanian >> >> SELinux stores the active policy in memory, so the changes to this data >> at runtime would have an impact on the security guarantees provided >> by SELinux. Measuring in-memory SELinux policy through IMA subsystem >> provides a secure way for the attestation service to remotely validate >> the policy contents at runtime. >> >> Measure the hash of the loaded policy by calling the IMA hook >> ima_measure_critical_data(). Since the size of the loaded policy >> can be large (several MB), measure the hash of the policy instead of >> the entire policy to avoid bloating the IMA log entry. >> >> To enable SELinux data measurement, the following steps are required: >> >> 1, Add "ima_policy=critical_data" to the kernel command line arguments >> to enable measuring SELinux data at boot time. >> For example, >> BOOT_IMAGE=/boot/vmlinuz-5.10.0-rc1+ root=UUID=fd643309-a5d2-4ed3-b10d-3c579a5fab2f ro nomodeset security=selinux ima_policy=critical_data >> >> 2, Add the following rule to /etc/ima/ima-policy >> measure func=CRITICAL_DATA label=selinux >> >> Sample measurement of the hash of SELinux policy: >> >> To verify the measured data with the current SELinux policy run >> the following commands and verify the output hash values match. >> >> sha256sum /sys/fs/selinux/policy | cut -d' ' -f 1 >> >> grep "selinux-policy-hash" /sys/kernel/security/integrity/ima/ascii_runtime_measurements | tail -1 | cut -d' ' -f 6 >> >> Note that the actual verification of SELinux policy would require loading >> the expected policy into an identical kernel on a pristine/known-safe >> system and run the sha256sum /sys/kernel/selinux/policy there to get >> the expected hash. >> >> Signed-off-by: Lakshmi Ramasubramanian >> Suggested-by: Stephen Smalley >> Reviewed-by: Tyler Hicks >> --- >> Documentation/ABI/testing/ima_policy | 3 +- >> security/selinux/Makefile | 2 + >> security/selinux/ima.c | 64 ++++++++++++++++++++++++++++ >> security/selinux/include/ima.h | 24 +++++++++++ >> security/selinux/include/security.h | 3 +- >> security/selinux/ss/services.c | 64 ++++++++++++++++++++++++---- >> 6 files changed, 149 insertions(+), 11 deletions(-) >> create mode 100644 security/selinux/ima.c >> create mode 100644 security/selinux/include/ima.h > > I remain concerned about the possibility of bypassing a measurement by > tampering with the time, but I appear to be the only one who is > worried about this so I'm not going to block this patch on those > grounds. > > Acked-by: Paul Moore Thanks Paul. -lakshmi