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=-16.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,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 97886C388F9 for ; Fri, 23 Oct 2020 22:50:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E2412137B for ; Fri, 23 Oct 2020 22:50:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="oB1UhE8M" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758365AbgJWWuy (ORCPT ); Fri, 23 Oct 2020 18:50:54 -0400 Received: from linux.microsoft.com ([13.77.154.182]:35334 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758363AbgJWWuy (ORCPT ); Fri, 23 Oct 2020 18:50:54 -0400 Received: from [192.168.86.21] (c-71-197-163-6.hsd1.wa.comcast.net [71.197.163.6]) by linux.microsoft.com (Postfix) with ESMTPSA id 9CF4220B4905; Fri, 23 Oct 2020 15:50:52 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 9CF4220B4905 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1603493453; bh=51mgwXigRi3atgRXO7/qeI9rkW4VOXGqrl7CREykoC8=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=oB1UhE8Mwjj2hC32U8VKu5Fv4YAqtmu14D18ybG6Ynbp4bjTodMVMCcO39GKwBF0e RsBMxDUxLt+kM4xGamw27sTktTv6GAKG143EYkFMQSxDkhaNEWNlVJGv5z/VXpMGVE 03PbGPdTsRAs9TcgNoiaWXY8D7yOZLUdJBTC8bz8= Subject: Re: [PATCH v4 4/6] IMA: add policy to measure critical data from kernel components To: Mimi Zohar , stephen.smalley.work@gmail.com, casey@schaufler-ca.com, agk@redhat.com, snitzer@redhat.com, gmazyland@gmail.com Cc: tyhicks@linux.microsoft.com, sashal@kernel.org, jmorris@namei.org, nramas@linux.microsoft.com, 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: <20200923192011.5293-1-tusharsu@linux.microsoft.com> <20200923192011.5293-5-tusharsu@linux.microsoft.com> <37aa4e6f5db6c53f4021f829ec09388d55d28208.camel@linux.ibm.com> From: Tushar Sugandhi Message-ID: <87499f4e-d1d1-916c-24d2-0228bcacad26@linux.microsoft.com> Date: Fri, 23 Oct 2020 15:50:52 -0700 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: <37aa4e6f5db6c53f4021f829ec09388d55d28208.camel@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: On 2020-10-22 2:15 p.m., Mimi Zohar wrote: > Hi Tushar, > > The above Subject line should be truncated to "IMA: add policy to > measure critical data". > > On Wed, 2020-09-23 at 12:20 -0700, Tushar Sugandhi wrote: >> There would be several candidate kernel components suitable for IMA >> measurement. Not all of them would have support for IMA measurement. > > This intro is besides the point. The patch description should describe > what is meant by "critical data". > Thanks. I will fix the description to address this. >> Also, system administrators may not want to measure data for all of >> them, even when they support IMA measurement. >> An IMA policy option >> specific to various kernel components is needed to measure their >> respective critical data. >> >> This policy option needs to be constrained to measure data for >> specific kernel components that are specified as input values to the >> policy option. >> >> Add a new IMA policy option - "data_sources:=" to allow measuring >> various critical kernel components. This policy option would enable the >> system administrators to limit the measurement to the components >> listed in "data_sources:=", if the components support IMA measurement. >> >> The new policy option "data_sources:=" is different from the existing >> policy option "keyrings:=". >> >> In case of "keyrings:=", a policy may measure all keyrings (when >> "keyrings:=" option is not provided for func KEY_CHECK), or may >> constrain which keyrings need to be measured (when "keyrings:=" option >> is provided for func KEY_CHECK). >> >> But unlike "keyrings:=", the entries in "data_sources:=" would have >> different data format. Further, the components listed in >> "data_sources:=" need to be modified to call IMA to measure their >> data. Therefore, unlike "keyrings:=", IMA shouldn't measure all of the >> components by default, when "data_sources:=" is not specified. Because >> measuring non-vetted components just by specifying them as a policy >> option value may impact the overall reliability of the system. >> >> To address this, "data_sources:=" should be a mandatory policy option >> for func=CRITICAL_DATA. This func is introduced in the 5th patch in this >> series). And the compile-time vetting functionality described above is >> introduced in the 6th patch in this series. >> >> Signed-off-by: Tushar Sugandhi > > I don't understand what you mean by "non-vetted" components, nor how > measuring critical data may impact the overall reliability of the > system. > Tushar: Before we introduced the mechanism to check supported data-sources at compile time (patch 6/6 of this series), there was a back-and-forth on whether “data_sources:=” should be a mandatory policy option, or optional like “keyrings:=”. And we decided to make the “data_sources:=” mandatory. But now that we have the compile time check (patch 6/6 of this series), we can switch to make “data_sources:=” optional (with the default to allow measuring all critical data – just like what you suggested below). I will make the code and description changes accordingly. > The system owner or adminstrator defines what they want to measure, > including "critical data", based on the policy rules. They might > decide that they want to constrain which "critical data" is measured by > specifying "data_sources:=", but that decision is their perogative. > The default should allow measuring all critical data. > Makes sense. To summarize, we will make the decision which sources to measure- based on the sources defined in the allow list (in patch 6) and the sources defined in “data_sources:=”. If “data_sources:=” is not present, we will measure all sources defined in the allow list. Hope my this understanding is correct based on your feedback. > A simple example of "critical data" could be some in memory structure, > along the lines of __ro_after_init, or hash of the memory structure. > Once the data structure is initialized, the "critical data" measurement > shouldn't change. From the attestation server perspective, the IMA > measurement list would contain a single record unless the critical data > changes. The attestation server doesn't need to know anything about > the initial value, just that it has changed in order to trigger some > sort alert. Yes agreed. After the updates (based on your feedback) I stated above, the behavior should remain consistent with what you described here. > > thanks, > > Mimi >