[RFC 15/20] capabilities: Introduce CAP_INTEGRITY_ADMIN

Stefan Berger
2021-11-30T16:07:37Z

From: Denis Semakin <denis.semakin@huawei.com>

This patch introduces CAP_INTEGRITY_ADMIN, a new capability that allows
to setup IMA (Integrity Measurement Architecture) policies per container
for non-root users.

The main purpose of this new capability is discribed in this document:
https://kernsec.org/wiki/index.php/IMA_Namespacing_design_considerations
It is said: "setting the policy should be possibly without the powerful
CAP_SYS_ADMIN and there should be the opportunity to gate this with a new
capability CAP_INTEGRITY_ADMIN that allows a user to set the IMA policy
during container runtime.."

In other words it should be possible to setup IMA policies while not
giving too many privilges to the user, therefore splitting the
CAP_INTEGRITY_ADMIN off from CAP_SYS_ADMIN.

Signed-off-by: Denis Semakin <denis.semakin@huawei.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
include/linux/capability.h | 6 ++++++
include/uapi/linux/capability.h | 7 ++++++-
security/selinux/include/classmap.h | 4 ++--
3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 65efb74c3585..ea6d58acb95e 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -278,4 +278,10 @@ int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
const void **ivalue, size_t size);

+static inline bool integrity_admin_ns_capable(struct user_namespace *ns)
+{
+ return ns_capable(ns, CAP_INTEGRITY_ADMIN) ||
+ ns_capable(ns, CAP_SYS_ADMIN);
+}
+
#endif /* !_LINUX_CAPABILITY_H */
diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
index 463d1ba2232a..48b08e4b3895 100644
--- a/include/uapi/linux/capability.h
+++ b/include/uapi/linux/capability.h
@@ -417,7 +417,12 @@ struct vfs_ns_cap_data {

#define CAP_CHECKPOINT_RESTORE 40

-#define CAP_LAST_CAP CAP_CHECKPOINT_RESTORE
+/* Allow setup IMA policy per container independently */
+/* No necessary to be superuser */
+
+#define CAP_INTEGRITY_ADMIN 41
+
+#define CAP_LAST_CAP CAP_INTEGRITY_ADMIN

#define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)

diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 35aac62a662e..7ff532b90f09 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -28,9 +28,9 @@

#define COMMON_CAP2_PERMS "mac_override", "mac_admin", "syslog", \
"wake_alarm", "block_suspend", "audit_read", "perfmon", "bpf", \
- "checkpoint_restore"
+ "checkpoint_restore", "integrity_admin"

-#if CAP_LAST_CAP > CAP_CHECKPOINT_RESTORE
+#if CAP_LAST_CAP > CAP_INTEGRITY_ADMIN
#error New capability defined, please update COMMON_CAP2_PERMS.
#endif

--
2.31.1