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Fri, 3 Dec 2021 02:31:24 +0000 (GMT) Received: from sbct-3.pok.ibm.com (unknown [9.47.158.153]) by b03ledav001.gho.boulder.ibm.com (Postfix) with ESMTP; Fri, 3 Dec 2021 02:31:23 +0000 (GMT) From: Stefan Berger To: linux-integrity@vger.kernel.org Cc: zohar@linux.ibm.com, serge@hallyn.com, christian.brauner@ubuntu.com, containers@lists.linux.dev, dmitry.kasatkin@gmail.com, ebiederm@xmission.com, krzysztof.struczynski@huawei.com, roberto.sassu@huawei.com, mpeters@redhat.com, lhinds@redhat.com, lsturman@redhat.com, puiterwi@redhat.com, jejb@linux.ibm.com, jamjoom@us.ibm.com, linux-kernel@vger.kernel.org, paul@paul-moore.com, rgb@redhat.com, linux-security-module@vger.kernel.org, jmorris@namei.org, Stefan Berger Subject: [RFC v2 00/19] ima: Namespace IMA with audit support in IMA-ns Date: Thu, 2 Dec 2021 21:30:59 -0500 Message-Id: <20211203023118.1447229-1-stefanb@linux.ibm.com> X-Mailer: git-send-email 2.31.1 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 0EK4HKMpon8NZH4l2kTpFl-pDNb6BxFB X-Proofpoint-ORIG-GUID: 5w3h-Zfycv5jWrWjnpdxERRtlFTna9ut X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2021-12-02_16,2021-12-02_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 lowpriorityscore=0 bulkscore=0 phishscore=0 clxscore=1015 spamscore=0 priorityscore=1501 mlxscore=0 mlxlogscore=999 impostorscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2112030012 Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org The goal of this series of patches is to start with the namespacing of IMA and support auditing within an IMA namespace (IMA-ns) as the first step. In this series the IMA namespace is piggy backing on the user namespace and therefore an IMA namespace gets created when a user namespace is created. The advantage of this is that the user namespace can provide the keys infrastructure that IMA appraisal support will need later on. We chose the goal of supporting auditing within an IMA namespace since it requires the least changes to IMA. Following this series, auditing within an IMA namespace can be activated by a user running the following lines that rely on a statically linked busybox to be installed on the host for execution within the minimal container environment: mkdir -p rootfs/{bin,mnt,proc} cp /sbin/busybox rootfs/bin PATH=/bin unshare --user --map-root-user --mount-proc --pid --fork \ --root rootfs busybox sh -c \ "busybox mount -t securityfs /mnt /mnt; \ busybox echo 'audit func=BPRM_CHECK mask=MAY_EXEC' > /mnt/ima/policy; \ busybox cat /mnt/ima/policy" Following the audit log on the host the last line cat'ing the IMA policy inside the namespace would have been audited. Unfortunately the auditing line is not distinguishable from one stemming from actions on the host. The hope here is that Richard Brigg's container id support for auditing would help resolve the problem. The following lines added to a suitable IMA policy on the host would cause the execution of the commands inside the container (by uid 1000) to be measured and audited as well on the host, thus leading to two auditing messages for the 'busybox cat' above and log entries in IMA's system log. echo -e "measure func=BPRM_CHECK mask=MAY_EXEC uid=1000\n" \ "audit func=BPRM_CHECK mask=MAY_EXEC uid=1000\n" \ > /sys/kernel/security/ima/policy The goal of supporting measurement and auditing by the host, of actions occurring within IMA namespaces, is that users, particularly root, should not be able to evade the host's IMA policy just by spawning new IMA namespaces, running programs there, and discarding the namespaces again. This is achieved through 'hierarchical processing' of file accesses that are evaluated against the policy of the namespace where the action occurred and against all namespaces' and their policies leading back to the root IMA namespace (init_ima_ns). The patch series adds support for a virtualized SecurityFS with a few new API calls that are used by IMA namespacing so that only the data relevant to the IMA namespace are shown. The files and directories of other security subsystems (TPM, evm, Tomoyo, safesetid) are not showing up when secruityfs is mounted inside a user namespace. Much of the code leading up to the virtualization of SecurityFS deals with moving IMA's variables from various files into the IMA namespace structure called 'ima_namespace'. When it comes to determining the current IMA namespace I took the approach to get the current IMA namespace (get_current_ns()) on the top level and pass the pointer all the way down to those functions that now need access to the ima_namespace to get to their variables. This later on comes in handy once hierarchical processing is implemented in this series where we walk the list of namespaces backwards and again need to pass the pointer into functions. A side-effect of IMA being a child of the user namespace becomes apparent when virtualizing SecurityFS which has the effect that the filesystem code needs to take an additional reference to the user namespace (for the keyed filesystem), which in turn leads to the problem that the one additional reference doesn't allow the user namespace to be deleted. The work-around for this is to introduce an early teardown reference counter and related IMA function that gets invoked when the user namespace reference counter has reached a certain value, '1'. Freeing the filesystem then finally also leads to the deletion of the user namespace. This patch also introduces CAP_INTEGRITY_ADMIN as a subset of CAP_SYS_ADMIN's capabilities that allows access to the IMA policy via reduced capabilities. We would again later on use this capability to allow users to set file extended attributes for IMA appraisal support. The basis for this series of patches is Linux v5.15. My tree with these patches is here: https://github.com/stefanberger/linux-ima-namespaces/tree/v5.15%2Bimans.20211119.v4 Regards, Stefan v2: - Folllwed Christian's suggestion to virtualize securitytfs; no more securityfs_ns - Followed James's advice for late 'population' of securityfs for IMA namespaces - Squashed 2 patches dealing with capabilities - Added missing 'depends on USER_NS' to Kconfig - Added missing 'static' to several functions Denis Semakin (1): capabilities: Introduce CAP_INTEGRITY_ADMIN Mehmet Kayaalp (2): ima: Define ns_status for storing namespaced iint data ima: Namespace audit status flags Stefan Berger (16): ima: Add IMA namespace support ima: Move delayed work queue and variables into ima_namespace ima: Move IMA's keys queue related variables into ima_namespace ima: Move policy related variables into ima_namespace ima: Move ima_htable into ima_namespace ima: Move measurement list related variables into ima_namespace ima: Only accept AUDIT rules for IMA non-init_ima_ns namespaces for now ima: Implement hierarchical processing of file accesses securityfs: Prefix global variables with securityfs_ securityfs: Pass static variables as parameters from top level functions securityfs: Extend securityfs with namespacing support ima: Move some IMA policy and filesystem related variables into ima_namespace ima: Use integrity_admin_ns_capable() to check corresponding capability userns: Introduce a refcount variable for calling early teardown function ima/userns: Define early teardown function for IMA namespace ima: Setup securityfs for IMA namespace include/linux/capability.h | 6 + include/linux/ima.h | 129 ++++++++++ include/linux/security.h | 15 ++ include/linux/user_namespace.h | 21 +- include/uapi/linux/capability.h | 7 +- init/Kconfig | 13 + kernel/user.c | 9 +- kernel/user_namespace.c | 16 ++ security/inode.c | 239 ++++++++++++++++--- security/integrity/ima/Makefile | 4 +- security/integrity/ima/ima.h | 147 ++++++++---- security/integrity/ima/ima_api.c | 33 ++- security/integrity/ima/ima_appraise.c | 26 +- security/integrity/ima/ima_asymmetric_keys.c | 8 +- security/integrity/ima/ima_fs.c | 215 ++++++++++++++--- security/integrity/ima/ima_init.c | 14 +- security/integrity/ima/ima_init_ima_ns.c | 77 ++++++ security/integrity/ima/ima_main.c | 128 ++++++---- security/integrity/ima/ima_ns.c | 119 +++++++++ security/integrity/ima/ima_ns_status.c | 132 ++++++++++ security/integrity/ima/ima_policy.c | 142 ++++++----- security/integrity/ima/ima_queue.c | 75 +++--- security/integrity/ima/ima_queue_keys.c | 73 +++--- security/integrity/ima/ima_template.c | 4 +- security/selinux/include/classmap.h | 4 +- 25 files changed, 1324 insertions(+), 332 deletions(-) create mode 100644 security/integrity/ima/ima_init_ima_ns.c create mode 100644 security/integrity/ima/ima_ns.c create mode 100644 security/integrity/ima/ima_ns_status.c