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=-13.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 89E5FC433DF for ; Mon, 20 Jul 2020 17:34:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E7042070A for ; Mon, 20 Jul 2020 17:34:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="VNdAmeiW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732961AbgGTReL (ORCPT ); Mon, 20 Jul 2020 13:34:11 -0400 Received: from linux.microsoft.com ([13.77.154.182]:37202 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726812AbgGTReL (ORCPT ); Mon, 20 Jul 2020 13:34:11 -0400 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 7E77B20B4909; Mon, 20 Jul 2020 10:34:10 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 7E77B20B4909 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1595266450; bh=IZbk6/wtyJwvcs8UDH0IEXfn70iZQSY+5CSfF+kU3Rc=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=VNdAmeiW7jXcjnKnfNMnaEBf/ezZled7360IOAy1VUzHALwt7jjuWoAkwpSXHpul/ 4qfljZOmlJYttBy+0X7xXG+shb+uBTxDvlNY08zkr5FvlqeFMYE2GE92azX5ggHui+ +DsrMVMna+iBrldPtiweIP24gad0m/PYLoQGCPlg= Subject: Re: [PATCH v3 4/5] LSM: Define SELinux function to measure security state To: Stephen Smalley Cc: Mimi Zohar , Casey Schaufler , James Morris , linux-integrity@vger.kernel.org, SElinux list , LSM List , linux-kernel References: <20200717222819.26198-1-nramas@linux.microsoft.com> <20200717222819.26198-5-nramas@linux.microsoft.com> From: Lakshmi Ramasubramanian Message-ID: Date: Mon, 20 Jul 2020 10:34:06 -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: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/20/20 10:06 AM, Stephen Smalley wrote: >> The above will ensure the following sequence will be measured: >> #1 State A - Measured >> #2 Change from State A to State B - Measured >> #3 Change from State B back to State A - Since the measured data is >> same as in #1, the change will be measured only if the event name is >> different between #1 and #3 > > Perhaps the timestamp / sequence number should be part of the hashed > data instead of the event name? If the timestamp/seqno is part of the hashed data, on every call to measure IMA will add a new entry in the IMA log. This would fill up the IMA log - even when there is no change in the measured data. To avoid that I keep the last measurement in SELinux and measure only when there is a change with the timestamp in the event name. > I can see the appraiser wanting to know two things: > 1) The current state of the system (e.g. is it enforcing, is the > currently loaded policy the expected one?). > 2) Has the system ever been in an unexpected state (e.g. was it > temporarily switched to permissive or had an unexpected policy > loaded?) Yes - you are right. The appraiser will have to look at the entire IMA log (and the corresponding TPM PCR data) to know the above. Time t0 => State of the system measured Time tn => State changed and the new state measured Time tm => State changed again and the new state measured. Say, the measurement at "Time tn" was an illegal change, the appraiser would know. > > I applied the patch series on top of the next-integrity branch, added > measure func=LSM_STATE to ima-policy, and booted that kernel. I get > the following entries in ascii_runtime_measurements, but seemingly > missing the final field: > > 10 8a09c48af4f8a817f59b495bd82971e096e2e367 ima-ng > sha256:21c3d7b09b62b4d0b3ed15ba990f816b94808f90b76787bfae755c4b3a44cd24 > selinux-state > 10 e610908931d70990a2855ddb33c16af2d82ce56a ima-ng > sha256:c8898652afd5527ef4eaf8d85f5fee1d91fcccee34bc97f6e55b96746bedb318 > selinux-policy-hash > > Thus, I cannot verify. What am I missing? > Looks like the template used is ima-ng which doesn't include the measured buffer. Please set template to "ima-buf" in the policy. For example, measure func=LSM_STATE template=ima-buf thanks, -lakshmi