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=-1.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,UNPARSEABLE_RELAY 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 80D2AC10F08 for ; Thu, 21 Feb 2019 14:49:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 529A920700 for ; Thu, 21 Feb 2019 14:49:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="kLJlcN9n" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728406AbfBUOtY (ORCPT ); Thu, 21 Feb 2019 09:49:24 -0500 Received: from userp2130.oracle.com ([156.151.31.86]:36622 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727594AbfBUOtX (ORCPT ); Thu, 21 Feb 2019 09:49:23 -0500 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x1LEhsCO180137; Thu, 21 Feb 2019 14:49:19 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=content-type : mime-version : subject : from : in-reply-to : date : cc : content-transfer-encoding : message-id : references : to; s=corp-2018-07-02; bh=gU4/lIIXfp5axGfGZemOTwBmY15/bZEdGRpknUuohV8=; b=kLJlcN9neikNjCFWfa93W88rTRw3dfIhYRUZKe9ZhE/yH/x0nLJOXdUiNPqNHKA2K/Z8 Vab68LRp0J4hFQKQPRBU7nyMcexJMpKG7yO6i3sT3AWCwxs5fTFYPUGsex6NZSv/TotO PqTA8DJumJQpZPiZQi+6F1m+ODhTeMq32ywlFZrfUd9d0Kzdw3SAMacxNmoqIUCMVOl0 r5f7zLblr1GoycHmu+bS//Aixvy7jNWXmTFs5o/C8CbpAal7hTTwBibb5EveZq+Vg+zn 7c6fIlmNLD/gmDO44hEv65UBiKe0hlYIUIaLXs+DjDbqeJGekI12ASDLU4+hee2qYMkb lA== Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by userp2130.oracle.com with ESMTP id 2qp9xu8ey9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 21 Feb 2019 14:49:19 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x1LEnI2Q007552 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 21 Feb 2019 14:49:18 GMT Received: from abhmp0013.oracle.com (abhmp0013.oracle.com [141.146.116.19]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x1LEnHgF031964; Thu, 21 Feb 2019 14:49:17 GMT Received: from anon-dhcp-171.1015granger.net (/68.61.232.219) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 21 Feb 2019 06:49:17 -0800 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.2 \(3445.102.3\)) Subject: Re: [PATCH RFC 0/4] IMA on NFS prototype From: Chuck Lever In-Reply-To: <1550665596.17768.32.camel@linux.ibm.com> Date: Thu, 21 Feb 2019 09:49:16 -0500 Cc: Linux NFS Mailing List , linux-integrity@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <71608AB6-ED45-43BA-A520-0DC2DA7D1C44@oracle.com> References: <20190214203336.6469.34750.stgit@manet.1015granger.net> <1550623002.17768.10.camel@linux.ibm.com> <1550665596.17768.32.camel@linux.ibm.com> To: Mimi Zohar X-Mailer: Apple Mail (2.3445.102.3) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9173 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902210108 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org > On Feb 20, 2019, at 7:26 AM, Mimi Zohar wrote: >=20 > On Tue, 2019-02-19 at 22:51 -0500, Chuck Lever wrote: >>> On Feb 19, 2019, at 7:36 PM, Mimi Zohar wrote: >>>=20 >>> Hi Chuck, >>>=20 >>>> EVM is not supported in this prototype. NFS does not support = several >>>> of the xattrs that are protected by EVM: SMACK64, Posix ACLs, and >>>> Linux file capabilities are not supported, which makes EVM more >>>> difficult to support on NFS mounts. >>>=20 >>> There's no requirement for all of these xattrs to exist. If an = xattr >>> does exist, then it is included in the security.evm hmac/signature. >>=20 >> Understood. The issue is that if they exist on a file residing on an = NFS server, >> such xattrs would not be visible to clients. My understanding is that = then EVM >> verification would fail on such files on NFS clients. >>=20 >> We could possibly make EVM work in limited scenarios until such time = that >> the NFS protocol can make those xattrs available to NFS clients. I = hope that >> having only security.ima is useful at least for experimenting and = maybe more. >>=20 >> However, if folks think having security.evm also is needed, that is = straight- >> forward... just saying that there are currently other limits in NFS = that make a >> full EVM implementation problematic. >=20 > Thank you for the explanation. Yes, I think there is a benefit of > having a file signature, without EVM. It's been pointed out to me that a malicious actor inserted between an NFS server and an NFS client can concurrently substitute the IMA signature and a file's content with that of another file on the same NFS share. This could be used to substitute /etc/group for /etc/passwd, for example. Both files are unchanged and have verifiable IMA signatures. The /etc/group file contains a passwd-like entry for root in it, but without a password field. That would allow the actor to gain root access on the NFS client. NFS can mitigate this substitution by using Kerberos 5 integrity to protect wire traffic from tampering. However, a malicious NFS server could also perform this substitution, and krb5i would not be able to detect it. I'm wondering if there's a mechanism within IMA's toolset to detect such a substitution on an NFS client. -- Chuck Lever