From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mimi Zohar Date: Mon, 02 Dec 2019 18:18:34 +0000 Subject: Re: [PATCH v9 5/6] IMA: Add support to limit measuring keys Message-Id: <1575310714.4793.420.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="maccentraleurope" Content-Transfer-Encoding: base64 List-Id: References: <20191127015654.3744-1-nramas@linux.microsoft.com> <20191127015654.3744-6-nramas@linux.microsoft.com> <1574880741.4793.292.camel@linux.ibm.com> <18b30666-7c44-f81e-8515-189052007e47@linux.microsoft.com> In-Reply-To: <18b30666-7c44-f81e-8515-189052007e47@linux.microsoft.com> To: Lakshmi Ramasubramanian , linux-integrity@vger.kernel.org Cc: eric.snowberg@oracle.com, dhowells@redhat.com, matthewgarrett@google.com, sashal@kernel.org, jamorris@linux.microsoft.com, linux-kernel@vger.kernel.org, keyrings@vger.kernel.org T24gV2VkLCAyMDE5LTExLTI3IGF0IDE2OjQ0IC0wODAwLCBMYWtzaG1pIFJhbWFzdWJyYW1hbmlh 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 2 Dec 2019 18:18:37 -0000 Received: from d06av24.portsmouth.uk.ibm.com (d06av24.portsmouth.uk.ibm.com [9.149.105.60]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id xB2IIaDa52363282 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 2 Dec 2019 18:18:36 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 444FB42041; Mon, 2 Dec 2019 18:18:36 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2E96C4203F; Mon, 2 Dec 2019 18:18:35 +0000 (GMT) Received: from localhost.localdomain (unknown [9.85.147.107]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 2 Dec 2019 18:18:35 +0000 (GMT) Subject: Re: [PATCH v9 5/6] IMA: Add support to limit measuring keys From: Mimi Zohar To: Lakshmi Ramasubramanian , linux-integrity@vger.kernel.org Cc: eric.snowberg@oracle.com, dhowells@redhat.com, matthewgarrett@google.com, sashal@kernel.org, jamorris@linux.microsoft.com, linux-kernel@vger.kernel.org, keyrings@vger.kernel.org Date: Mon, 02 Dec 2019 13:18:34 -0500 In-Reply-To: <18b30666-7c44-f81e-8515-189052007e47@linux.microsoft.com> References: <20191127015654.3744-1-nramas@linux.microsoft.com> <20191127015654.3744-6-nramas@linux.microsoft.com> <1574880741.4793.292.camel@linux.ibm.com> <18b30666-7c44-f81e-8515-189052007e47@linux.microsoft.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19120218-0028-0000-0000-000003C39241 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19120218-0029-0000-0000-00002486A8F0 Message-Id: <1575310714.4793.420.camel@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-02_04:2019-11-29,2019-12-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=0 lowpriorityscore=0 mlxscore=0 clxscore=1015 mlxlogscore=999 spamscore=0 phishscore=0 suspectscore=2 adultscore=0 bulkscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912020155 Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Wed, 2019-11-27 at 16:44 -0800, Lakshmi Ramasubramanian wrote: > On 11/27/19 10:52 AM, Mimi Zohar wrote: > > Hi Mimi, > > >> +static bool ima_match_keyring(struct ima_rule_entry *rule, > >> + const char *keyring) > >> +{ > >> + /* > >> + * "keyrings=" is specified in the policy in the format below: > >> + * keyrings=.builtin_trusted_keys|.ima|.evm > >> + * > >> + * Each keyring name in the option is separated by a '|' and > >> + * the last keyring name is null terminated. > >> + * > >> + * The given keyring is considered matched only if > >> + * the whole keyring name matched a keyring name specified > >> + * in the "keyrings=" option. > >> + */ > >> + p = strstr(rule->keyrings, keyring); > >> + if (p) { > >> + /* > >> + * Found a substring match. Check if the character > >> + * at the end of the keyring name is | (keyring name > >> + * separator) or is the terminating null character. > >> + * If yes, we have a whole string match. > >> + */ > >> + p += strlen(keyring); > >> + if (*p == '|' || *p == '\0') > >> + return true; This code checks that the keyring name isn't suffixed, but not prefixed. > >> + } > >> + > > > > Using "while strsep()" would simplify this code, removing the need for > > such a long comment. > > > > Mimi > > strsep() modifies the source string (replaces the delimiter with '\0' > and also updates the source string pointer). I am not sure it can be > used for our scenario. Please correct me if I am wrong. > > Initial IMA policy: > ------------------- > measure func=KEY_CHECK > keyrings=.ima|.evm|.builtin_trusted_keys|.blacklist template=ima-buf > > Policy after adding a key to .ima keyring: > ------------------------------------------ > measure func=KEY_CHECK keyrings=.evm|.builtin_trusted_keys|.blacklist > template=ima-buf > > Policy after adding a key to a keyring that is not listed in the policy: > ------------------------------------------------------------------------ > measure func=KEY_CHECK keyrings= template=ima-buf > > ******************************************************************************** > > Please see the description from the man page for strsep(): > > http://man7.org/linux/man-pages/man3/strsep.3.html > > char *strsep(char **stringp, const char *delim); > > This function finds the first token in the string *stringp, that is > delimited by one of the bytes in the string delim. This token is > terminated by overwriting the delimiter with a null byte ('\0'), and > *stringp is updated to point past the token. Yes, you would have to make a copy of the string before using strsep().  You could always use kstrdup(), remembering to free it, or allocate the memory just once, and then just use memcpy. Mimi