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Wed, 11 Aug 2021 19:40:54 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F05C94C052; Wed, 11 Aug 2021 19:40:52 +0000 (GMT) Received: from li-f45666cc-3089-11b2-a85c-c57d1a57929f.ibm.com (unknown [9.160.36.65]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 11 Aug 2021 19:40:52 +0000 (GMT) Message-ID: Subject: Re: [PATCH v7 0/5] IMA: restrict the accepted digest algorithms for the security.ima xattr From: Mimi Zohar To: THOBY Simon , "dmitry.kasatkin@gmail.com" , "linux-integrity@vger.kernel.org" , BARVAUX Didier Cc: linux-audit@redhat.com Date: Wed, 11 Aug 2021 15:40:51 -0400 In-Reply-To: <20210811114037.201887-1-simon.thoby@viveris.fr> References: <20210811114037.201887-1-simon.thoby@viveris.fr> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.28.5 (3.28.5-16.el8) X-TM-AS-GCONF: 00 X-Proofpoint-GUID: bFqnP9XBW_lefSwqjA5v9vF3cphPNZEt X-Proofpoint-ORIG-GUID: OQXI5cr_vAZZdY6hBum6dWSsqjrRRyUZ Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-11_06:2021-08-11,2021-08-11 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 mlxscore=0 malwarescore=0 bulkscore=0 suspectscore=0 impostorscore=0 phishscore=0 mlxlogscore=999 lowpriorityscore=0 priorityscore=1501 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108110133 Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org [Cc'ing linux-audit] Hi Simon, 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 > > 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.git > branch: next-integrity-testing > commit e37be5343ae2b9419aea1442b07e5d2428b437b4 ("Merge branch 'ima-buffer-measurement-changes-v4' into next-integrity")