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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 BC87EC433ED for ; Mon, 3 May 2021 15:33:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8FC9261027 for ; Mon, 3 May 2021 15:33:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230419AbhECPdv convert rfc822-to-8bit (ORCPT ); Mon, 3 May 2021 11:33:51 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:2990 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230396AbhECPdr (ORCPT ); Mon, 3 May 2021 11:33:47 -0400 Received: from fraeml707-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4FYmxL2qmLz6snwd; Mon, 3 May 2021 23:24:54 +0800 (CST) Received: from fraeml714-chm.china.huawei.com (10.206.15.33) by fraeml707-chm.china.huawei.com (10.206.15.35) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Mon, 3 May 2021 17:32:52 +0200 Received: from fraeml714-chm.china.huawei.com ([10.206.15.33]) by fraeml714-chm.china.huawei.com ([10.206.15.33]) with mapi id 15.01.2176.012; Mon, 3 May 2021 17:32:52 +0200 From: Roberto Sassu To: Mimi Zohar , "mjg59@google.com" CC: "linux-integrity@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Christian Brauner , Andreas Gruenbacher Subject: RE: [PATCH v5 09/12] evm: Allow setxattr() and setattr() for unmodified metadata Thread-Topic: [PATCH v5 09/12] evm: Allow setxattr() and setattr() for unmodified metadata Thread-Index: AQHXK5xeSg6sM/30eEKbqlkQ5rVFkKrRv8yAgABEE/D//+S7AIAAIuSw Date: Mon, 3 May 2021 15:32:52 +0000 Message-ID: References: <20210407105252.30721-1-roberto.sassu@huawei.com> <20210407105252.30721-10-roberto.sassu@huawei.com> <8493d7e2b0fefa4cd3861bd6b7ee6f2340aa7434.camel@linux.ibm.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.221.98.153] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Mimi Zohar [mailto:zohar@linux.ibm.com] > Sent: Monday, May 3, 2021 5:26 PM > On Mon, 2021-05-03 at 15:11 +0000, Roberto Sassu wrote: > > > From: Mimi Zohar [mailto:zohar@linux.ibm.com] > > > Sent: Monday, May 3, 2021 3:00 PM > > > On Wed, 2021-04-07 at 12:52 +0200, Roberto Sassu wrote: > > > > > > > diff --git a/security/integrity/evm/evm_main.c > > > b/security/integrity/evm/evm_main.c > > > > @@ -389,6 +473,11 @@ static int evm_protect_xattr(struct > > > user_namespace *mnt_userns, > > > > if (evm_status == INTEGRITY_FAIL_IMMUTABLE) > > > > return 0; > > > > > > > > + if (evm_status == INTEGRITY_PASS_IMMUTABLE && > > > > + !evm_xattr_change(mnt_userns, dentry, xattr_name, xattr_value, > > > > + xattr_value_len)) > > > > + return 0; > > > > + > > > > > > If the purpose of evm_protect_xattr() is to prevent allowing an invalid > > > security.evm xattr from being re-calculated and updated, making it > > > valid, INTEGRITY_PASS_IMMUTABLE shouldn't need to be conditional. > Any > > > time there is an attr or xattr change, including setting it to the > > > existing value, the status flag should be reset. > > > > > > I'm wondering if making INTEGRITY_PASS_IMMUTABLE conditional would > > > prevent the file from being resigned. > > > > > > > if (evm_status != INTEGRITY_PASS) > > > > integrity_audit_msg(AUDIT_INTEGRITY_METADATA, > > > d_backing_inode(dentry), > > > > dentry->d_name.name, > > > "appraise_metadata", > > > > > > This would then be updated to if not INTEGRITY_PASS or > > > INTEGRITY_PASS_IMMUTABLE. The subsequent "return" would need to > be > > > updated as well. > > > > I agree on the first suggestion, to reduce the number of log messages. > > For the second, if you meant that we should return 0 if the status is > > INTEGRITY_PASS_IMMUTABLE, I thought we wanted to deny xattr > > changes when there is an EVM portable signature. > > Why? I must be missing something. As long as we're not relying on the > cached status, allowing the file metadata to be updated shouldn't be an > issue. We may want to prevent accidental changes, for example. Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli