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Wed, 11 Aug 2021 23:53:26 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 05AEC60BF1; Wed, 11 Aug 2021 23:53:26 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 24837181A0F7; Wed, 11 Aug 2021 23:53:24 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 17BNrMlg012111 for ; Wed, 11 Aug 2021 19:53:22 -0400 Received: by smtp.corp.redhat.com (Postfix) id 965A6604CC; Wed, 11 Aug 2021 23:53:22 +0000 (UTC) Received: from x2.localnet (unknown [10.22.8.17]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5B067620DE; Wed, 11 Aug 2021 23:53:17 +0000 (UTC) From: Steve Grubb To: "linux-integrity@vger.kernel.org" , linux-audit@redhat.com, Mimi Zohar Subject: Re: [PATCH v7 0/5] IMA: restrict the accepted digest algorithms for the security.ima xattr Date: Wed, 11 Aug 2021 19:53:15 -0400 Message-ID: <2072391.irdbgypaU6@x2> Organization: Red Hat In-Reply-To: References: <20210811114037.201887-1-simon.thoby@viveris.fr> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-loop: linux-audit@redhat.com Cc: "dmitry.kasatkin@gmail.com" , BARVAUX Didier , THOBY Simon X-BeenThere: linux-audit@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Linux Audit Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=linux-audit-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hello, On Wednesday, August 11, 2021 3:40:51 PM EDT Mimi Zohar wrote: > On Wed, 2021-08-11 at 11:40 +0000, THOBY Simon wrote: > Other than the two questions on " IMA: add a policy option to restrict > xattr hash algorithms on appraisal" patch, the patch set is looking > good. > > thanks, > > Mimi > > > Here is also a short description of the new audit messages, but I can > > send it in a followup mail if that is not the proper place: > > > > When writing the xattr with an algorithm not built in the kernel (here > > the > > kernel was built with CONFIG_CRYPTO_MD5 unset), e.g. with > > > > "evmctl ima_hash -a md5 /usr/bin/strace": > > audit(1628066120.418:121): pid=1344 uid=0 auid=0 ses=1 > > subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 op=set_data > > cause=unavailable-hash-algorithm comm="evmctl" name="/usr/bin/strace" > > dev="dm-0" ino=2632657 res=0 errno=0> Is this audit event accurate? I seem to be seeing name=value=value. I'm hoping this is a copy/paste/mail client issue. -Steve > > With the same command and the policy rule > > > > "appraise func=SETXATTR_CHECK appraise_algos=sha256,sha384,sha512", we get: > > audit(1628066210.141:127): pid=1362 uid=0 auid=0 ses=1 > > subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 op=set_data > > cause=denied-hash-algorithm comm="evmctl" name="/usr/bin/strace" > > dev="dm-0" ino=2632657 res=0 errno=0> > > Note that the cause is now 'denied-hash-algorithm' instead of > > 'unavailable-hash-algorithm'. We get that audit message for any algorithm > > outside of sha256/384/512 (including algorithms not compiled in the > > kernel > > like MD5). In a sense, 'denied-hash-algorithm' takes predecence over > > 'unavailable-hash-algorithm'. > > > > When appraising files, e.g. trying to execute a file whose xattr was > > hashed with sha1 while the policy rule > > > > "appraise func=BPRM_CHECK fowner=0 appraise_algos=sha256" is enabled: > > audit(1628066349.230:130): pid=1369 uid=0 auid=0 ses=1 > > subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 > > op=collect_data cause=denied-hash-algorithm comm="bash" > > name="/usr/bin/strace" dev="dm-0" ino=2632657 res=0 errno=0> > > This series is based on the following repo/branch: > > repo: > > https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.g > > it branch: next-integrity-testing > > commit e37be5343ae2b9419aea1442b07e5d2428b437b4 ("Merge branch > > 'ima-buffer-measurement-changes-v4' into next-integrity") > -- > Linux-audit mailing list > Linux-audit@redhat.com > https://listman.redhat.com/mailman/listinfo/linux-audit -- Linux-audit mailing list Linux-audit@redhat.com https://listman.redhat.com/mailman/listinfo/linux-audit