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=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 9B55FC433ED for ; Mon, 3 May 2021 14:48:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F376611C2 for ; Mon, 3 May 2021 14:48:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229731AbhECOtq convert rfc822-to-8bit (ORCPT ); Mon, 3 May 2021 10:49:46 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:2987 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229641AbhECOtp (ORCPT ); Mon, 3 May 2021 10:49:45 -0400 Received: from fraeml712-chm.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4FYm145kwmz6wljg; Mon, 3 May 2021 22:43:04 +0800 (CST) Received: from fraeml714-chm.china.huawei.com (10.206.15.33) by fraeml712-chm.china.huawei.com (10.206.15.61) 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 16:48:50 +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 16:48:50 +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/30eEKbqlkQ5rVFkKrRv8yAgAAwwJA= Date: Mon, 3 May 2021 14:48:50 +0000 Message-ID: <06edfc9f779447b9b93f26628327d1e5@huawei.com> References: <20210407105252.30721-1-roberto.sassu@huawei.com> <20210407105252.30721-10-roberto.sassu@huawei.com> <8493d7e2b0fefa4cd3861bd6b7ee6f2340aa7434.camel@linux.ibm.com> In-Reply-To: <8493d7e2b0fefa4cd3861bd6b7ee6f2340aa7434.camel@linux.ibm.com> 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: > 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. The status is always reset if evm_protect_xattr() returns 0. This does not change. Not making INTEGRITY_PASS_IMMUTABLE conditional would cause issues. Suppose that the status is INTEGRITY_FAIL. Writing the same xattr would cause evm_protect_xattr() to return 0 and the HMAC to be updated. > I'm wondering if making INTEGRITY_PASS_IMMUTABLE conditional would > prevent the file from being resigned. INTEGRITY_FAIL_IMMUTABLE should be enough to continue the operation. Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli > > 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. > > thanks, > > Mimi