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=-10.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 585F7C433ED for ; Mon, 3 May 2021 15:13:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0E0266121D for ; Mon, 3 May 2021 15:13:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230094AbhECPOd (ORCPT ); Mon, 3 May 2021 11:14:33 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:10630 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229717AbhECPOc (ORCPT ); Mon, 3 May 2021 11:14:32 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 143F48st116650; Mon, 3 May 2021 11:13:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : subject : from : to : cc : date : in-reply-to : references : content-type : content-transfer-encoding : mime-version; s=pp1; bh=eDaj1jhHxQmBJpYcYXGZmB0FUavn6iXflGZ8LWwhdYw=; b=H493hy7LW/Y5Pb7XwZCWR4m+ONi6RANVJH1DiJIs/Y1aE7K2pcvFzRIFEHglyPj/Gx+3 biMVVDqyyyRBTGD230hoIdb1UIeFvoQC/f2J2wW8oxBu60h4R3E9At0+Nsg3bAlGoh4X qnFxKkD+tQy+gC/Ol5lnKzZ2uSUnfBx9a8822K+58M3yTOrue/ZmyhqT9okvmsTD5CIq MYxeol2Nq+QmFkKnAF4jg8yyzoXHZJ58PfADHf4lUj4gG6xt5oXxMgHB0OkOGSRLxxHT rEakgxLq8z4C5mE+jPTjUQYIR4hYOgDTOqKQBA8Q8Lf5Y5wkLKQe2g/O7FdJIlSvT2XX cw== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 38ahy4uavm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 03 May 2021 11:13:33 -0400 Received: from m0098416.ppops.net (m0098416.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 143F4hx2120473; Mon, 3 May 2021 11:13:32 -0400 Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0b-001b2d01.pphosted.com with ESMTP id 38ahy4uaun-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 03 May 2021 11:13:32 -0400 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.0.43/8.16.0.43) with SMTP id 143FCr7Z000398; Mon, 3 May 2021 15:13:31 GMT Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by ppma06ams.nl.ibm.com with ESMTP id 388x8hgs8v-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 03 May 2021 15:13:30 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 143FDSU527853092 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 3 May 2021 15:13:28 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 907695205F; Mon, 3 May 2021 15:13:28 +0000 (GMT) Received: from li-f45666cc-3089-11b2-a85c-c57d1a57929f.ibm.com (unknown [9.211.45.89]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 6067552052; Mon, 3 May 2021 15:13:26 +0000 (GMT) Message-ID: <33ddeb6108699f47ba47d5f002403ffeca5f9531.camel@linux.ibm.com> Subject: Re: [PATCH v5 09/12] evm: Allow setxattr() and setattr() for unmodified metadata From: Mimi Zohar To: Roberto Sassu , "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 Date: Mon, 03 May 2021 11:13:25 -0400 In-Reply-To: <06edfc9f779447b9b93f26628327d1e5@huawei.com> References: <20210407105252.30721-1-roberto.sassu@huawei.com> <20210407105252.30721-10-roberto.sassu@huawei.com> <8493d7e2b0fefa4cd3861bd6b7ee6f2340aa7434.camel@linux.ibm.com> <06edfc9f779447b9b93f26628327d1e5@huawei.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.28.5 (3.28.5-14.el8) X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: NX_CnYn1o6Hj1UvnM9Aqd-BiXjSLY9I2 X-Proofpoint-GUID: ysFaGwSzJmublxH3DOS1djooJuMuKeF- Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-05-03_10:2021-05-03,2021-05-03 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 lowpriorityscore=0 mlxlogscore=999 phishscore=0 adultscore=0 clxscore=1015 impostorscore=0 spamscore=0 suspectscore=0 mlxscore=0 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2105030104 Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Mon, 2021-05-03 at 14:48 +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. > > 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. This example is mixing security.evm types. Please clarify. > > 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. Agreed. Mimi