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=-5.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 CEDDFC433E1 for ; Wed, 5 Aug 2020 19:57:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B07672076E for ; Wed, 5 Aug 2020 19:57:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="CMnzX/Bk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727999AbgHET5l (ORCPT ); Wed, 5 Aug 2020 15:57:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45406 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727865AbgHEQns (ORCPT ); Wed, 5 Aug 2020 12:43:48 -0400 Received: from mail-qt1-x841.google.com (mail-qt1-x841.google.com [IPv6:2607:f8b0:4864:20::841]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 04E86C034612; Wed, 5 Aug 2020 05:46:04 -0700 (PDT) Received: by mail-qt1-x841.google.com with SMTP id c12so24490446qtn.9; Wed, 05 Aug 2020 05:46:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=th4R0mCDoEKdxtP92DcRMWCvQNUwMm704tc+tQsZ6e8=; b=CMnzX/BkmrlbcfiKr7JDmYk704xsWGknJKvd+HQfxigZlMYUd2JDxLZZJ7AM4TB3Tu xU1b2tTVbUxTEcVS0keHcGIOcvDbg0Mc9e44uwsdob+ZBmNGkINJPYUrbXW1+jGpvTLK q6HKh3ivwm3nAHOgsJQDTdhdUercSIIvr6v7SehaOwRjst4uDAortgK+6vcDK5Dt5wZ8 7kUHi9Unn4E4nmWDGVLlM94Hu3Od0H2KdOl1Ckkp64W9ckafVFOmZQUWzAWqj8Ku24va Sz1jmJ4MtajaF/nWDfSRh9FPkplHRF/31M1d8qwy/IO2PlKYQYUCF5z60bd5zaEURRNn opGA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=th4R0mCDoEKdxtP92DcRMWCvQNUwMm704tc+tQsZ6e8=; b=PJU27bSOqH20mghqx6QETZ0jSO+leoLP6wgwFCxeCMoJxxR1avg5sGLxBV5C+cPUlc DWT59RCsiIlY1lNKB2ljAAxaaye8nYTELA9ol90rCBwnZ4fRp3mypKEu4ClarcOlNlo/ Mj5hbDAFi2xQ1B9ayJsfebza8jQN/03qzPHK4pD58uZlkqzVokPhxZ+jiG4PctwxOjkL o5GmfBbc9GkYf7yef6Jd0KTixNhiE6um2UNKuFWC7xQEfVGkC86IYOm2RJYVlOfYePhi s0sT/DQyDxxqH440UK1xmxoCxUCQEtLeMFR9C2+65b5SWVkUO/2o7UierPSmAlPjdwao NSuQ== X-Gm-Message-State: AOAM5328/6BBHHHxelk2/fXz5Nva/BZcrwv045lqswa5StGURkOzNZQl DqdRMnnhaq0sKbou7glOiZG7CberAiY= X-Google-Smtp-Source: ABdhPJxrH4/VsLOKixqcHuZDqId9PnSjHLiReskUJRab0cl4DnJUCIsc2KvflzT6+UowANCjwPVYXw== X-Received: by 2002:ac8:6f51:: with SMTP id n17mr3057373qtv.233.1596631562731; Wed, 05 Aug 2020 05:46:02 -0700 (PDT) Received: from [192.168.1.190] (pool-96-244-118-111.bltmmd.fios.verizon.net. [96.244.118.111]) by smtp.gmail.com with ESMTPSA id j15sm1410469qkl.63.2020.08.05.05.46.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Aug 2020 05:46:01 -0700 (PDT) Subject: Re: [PATCH v6 1/4] IMA: Add func to measure LSM state and policy To: Mimi Zohar , Lakshmi Ramasubramanian , casey@schaufler-ca.com Cc: tyhicks@linux.microsoft.com, sashal@kernel.org, jmorris@namei.org, linux-integrity@vger.kernel.org, selinux@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200805004331.20652-1-nramas@linux.microsoft.com> <20200805004331.20652-2-nramas@linux.microsoft.com> <4b9d2715d3ef3c8f915ef03867cfb1a39c0abc54.camel@linux.ibm.com> From: Stephen Smalley Message-ID: Date: Wed, 5 Aug 2020 08:46:00 -0400 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: <4b9d2715d3ef3c8f915ef03867cfb1a39c0abc54.camel@linux.ibm.com> Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: 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.