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=-25.0 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, URIBL_BLOCKED,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 93571C433E6 for ; Thu, 14 Jan 2021 20:02:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 521A723359 for ; Thu, 14 Jan 2021 20:02:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730129AbhANUCI (ORCPT ); Thu, 14 Jan 2021 15:02:08 -0500 Received: from linux.microsoft.com ([13.77.154.182]:60802 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729249AbhANUCI (ORCPT ); Thu, 14 Jan 2021 15:02:08 -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 5DECF20B6C40; Thu, 14 Jan 2021 12:01:27 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 5DECF20B6C40 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1610654487; bh=Kv9kA9hyCrmK+ukDmZ0hqeRpgOqREfsVmhG/uF3QqmQ=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=qfD6W4Blr3Xs9NTKINaaLofPVakW4k7UKe2ummHWz0zZjqFhiOFZyEOvB3gsO7F5x qG2qJoiG8nDARMycZDhUHBe2HYAr4diUOU5hJQVQoswqR1a2+aJdq+BLEmL7JkVfe2 +nfpkes7s5Wbm5q3m290ttDgem/iPkbAZBrz2mec= Subject: Re: [PATCH] selinux: include a consumer of the new IMA critical data hook To: Tyler Hicks , Paul Moore Cc: zohar@linux.ibm.com, Stephen Smalley , tusharsu@linux.microsoft.com, casey@schaufler-ca.com, agk@redhat.com, snitzer@redhat.com, gmazyland@gmail.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 References: <20210114191522.4001-1-nramas@linux.microsoft.com> <20210114195813.GA81268@sequoia> From: Lakshmi Ramasubramanian Message-ID: <276c70ac-0d12-88f8-2d75-c88e68ef8490@linux.microsoft.com> Date: Thu, 14 Jan 2021 12:01:26 -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: <20210114195813.GA81268@sequoia> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org On 1/14/21 11:58 AM, Tyler Hicks wrote: > On 2021-01-14 14:29:09, Paul Moore wrote: >> On Thu, Jan 14, 2021 at 2:15 PM Lakshmi Ramasubramanian >> wrote: >>> >>> 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 >>> Acked-by: Paul Moore >>> Reviewed-by: Tyler Hicks >>> --- >>> Documentation/ABI/testing/ima_policy | 3 +- >>> security/selinux/Makefile | 2 + >>> security/selinux/ima.c | 44 +++++++++++++++++++ >>> security/selinux/include/ima.h | 24 +++++++++++ >>> security/selinux/include/security.h | 3 +- >>> security/selinux/ss/services.c | 64 ++++++++++++++++++++++++---- >>> 6 files changed, 129 insertions(+), 11 deletions(-) >>> create mode 100644 security/selinux/ima.c >>> create mode 100644 security/selinux/include/ima.h >> >> I think this has changed enough that keeping the "Acked-by" and >> "Reviewed-by" tags is probably not a good choice. I took a quick look >> and this still looks okay from a SELinux perspective, I'll leave Mimi >> to comment on it from a IMA perspective. Thanks for reviewing the change Paul. >> >> Unless Tyler has reviewed this version prior to your posting, it might >> be a good idea to remove his "Reviewed-by" unless he has a chance to >> look this over again before it is merged. > > Thanks for calling this out. I hadn't reviewed it prior to the posting > but I was keeping an eye on the thread. > > This new revision still looks good to me and I like the idea of > controlling re-measurements via policy. So, > > Reviewed-by: Tyler Hicks Thanks for the quick response Tyler. -lakshmi