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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 CAE67C2BB1D for ; Wed, 15 Apr 2020 02:49:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B2C352072D for ; Wed, 15 Apr 2020 02:49:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393004AbgDOCts (ORCPT ); Tue, 14 Apr 2020 22:49:48 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:47065 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728305AbgDOCtl (ORCPT ); Tue, 14 Apr 2020 22:49:41 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01422;MF=tianjia.zhang@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0Tva366D_1586918970; Received: from 30.27.118.45(mailfrom:tianjia.zhang@linux.alibaba.com fp:SMTPD_---0Tva366D_1586918970) by smtp.aliyun-inc.com(127.0.0.1); Wed, 15 Apr 2020 10:49:30 +0800 Subject: Re: [PATCH 0/2] support to read and tune appraise mode in runtime To: Mimi Zohar , dmitry.kasatkin@gmail.com, jmorris@namei.org, serge@hallyn.com, zhangliguang@linux.alibaba.com Cc: linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Nayna Jain References: <20200409033907.102833-1-tianjia.zhang@linux.alibaba.com> <1586814958.7311.92.camel@linux.ibm.com> <1586871674.7311.189.camel@linux.ibm.com> From: Tianjia Zhang Message-ID: <8afd9d82-b957-2be9-6132-411d28fa80dc@linux.alibaba.com> Date: Wed, 15 Apr 2020 10:49:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <1586871674.7311.189.camel@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/4/14 21:41, Mimi Zohar wrote: > On Tue, 2020-04-14 at 11:36 +0800, Tianjia Zhang wrote: >> >> On 2020/4/14 5:55, Mimi Zohar wrote: >>> On Thu, 2020-04-09 at 11:39 +0800, Tianjia Zhang wrote: >>>> Support the read and write operations of ima_appraise by adding a >>>> securifyfs file 'appraise_mode'. >>>> >>>> In order to tune appraise mode in runtime, writing a PKCS#7 signature >>>> corresponding the signed content is required. The content should be off, >>>> enforce, log or fix. Given a simple way to archive this: >>>> >>>> $ echo -n off > mode >>>> $ openssl smime -sign -nocerts -noattr -binary \ >>>> -in mode -inkey \ >>>> -signer -outform der -out mode.p7s >>>> $ sudo cat mode.p7s \ >>>> > /sys/kernel/security/ima/appraise_mode >>>> >>>> Note that the signing key must be a trust key located in >>>> system trusted keyring. So even the root privilege cannot >>>> simply disable the enforcement. >>> >>> There are major problems with disabling IMA appraisal.  This patch set >>> proposes disabling IMA appraisal without even providing the motivation >>> for such support. >>> >>> A lot of effort went into preventing custom IMA policies from >>> disabling appraising the kexec or kernel module signatures.  In >>> addition, the "lockdown" patch set was upstreamed permitting IMA >>> signature verification.  This patch set would break both of these >>> features. >>> >>> IMA relies on its own keyring for verifying file signatures, not the >>> builtin or secondary trusted kernel keyrings. >>> >>> Two methods already exist - xattr and appended signatures - for >>> verifying file signatures.  This patch set assumes creating and >>> signing a file, which is then written to a securityfs file.  Like for >>> loading a custom IMA policy, instead of cat'ing the file, write the >>> pathname to the securityfs file. >>> >>> If you must define a new IMA method for verifying file signatures, >>> then it needs to be generic and added to ima_appraise_measurement(). >>>  (Refer to the new IMA appended signature support.) >>> >>> Mimi >>> >>>> >>>> Tianjia Zhang (2): >>>> ima: support to read appraise mode >>>> ima: support to tune appraise mode in runtime >>>> >>>> security/integrity/ima/ima_fs.c | 134 +++++++++++++++++++++++++++++++- >>>> 1 file changed, 133 insertions(+), 1 deletion(-) >>>> >> >> Thanks for your suggestion, the way to close the appraise mode here is >> indeed a bit rude, I will reconsider again according to your suggestions. >> >> In addition, [PATCH 1/2] ima: support to read appraise mode, by the way, >> see if this patch is acceptable. > > My comments were not meant as suggestions, but as an explanation as to > how IMA works.  More details follow. > > IMA is based on policy.  That decision was made a long time ago.  It > allowed distros to configure IMA, allowing customers to experiment > with it.  You have one opportunity to totally change the boot time > policy rules, by loading a custom policy.  After that, rules may only > be added. > > There is no valid reason for "turning off" the policy once it has been > enabled.  It breaks existing expectations. > > Mimi > Thank you very much for your explanation. I'm sorry I may not have stated clearly. I didn't have to change the working mode of IMA. I was convinced by you to give up the idea of "turn off" the appraise. However, it should be possible to support appraise mode reading. Right?