[off-list ref],linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,linux-f2fs-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,jfs-discussion-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,ocfs2-devel-N0ozoZBvEnrZJqsBc5GL+g@public.gmane.org,linux-unionfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,reiserfs-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,selinux-+05T5uksL2qpZYMLLGbcSA@public.gmane.org,linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,kernel-hardening-ZwoEplunGu1jrUoiu81ncdBPR1lH4CV8@public.gmane.org
From: Nicolas Belouin <redacted>
Message-ID: [off-list ref]
On October 21, 2017 7:25:21 PM GMT+02:00, Casey Schaufler [off-list ref] wrote:
On 10/21/2017 6:45 AM, Nicolas Belouin wrote:
quoted
with CAP_SYS_ADMIN being bloated, the usefulness of using it to
flag a process to be entrusted for e.g reading and writing trusted
xattr is near zero.
CAP_TRUSTED aims to provide userland with a way to mark a process as
entrusted to do specific (not specially admin-centered) actions. It
would for example allow a process to red/write the trusted xattrs.
Please explain how this is different from CAP_MAC_ADMIN in
any existing use case. If it is significantly different, how
would the two interact?
From my point of view, CAP_MAC_ADMIN allows one to read/write security xattrs, those are meant to describe security policies. As far as I know of, trusted xattrs are intended for a privileged process to read or write arbitrary data. I don't have any real world example in mind that use trusted xattrs, but I'll try to find one.
quoted
Signed-off-by: Nicolas Belouin <redacted>
---
include/uapi/linux/capability.h | 6 +++++-
security/selinux/include/classmap.h | 5 +++--
2 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/capability.h
b/include/uapi/linux/capability.h
quoted
index ce230aa6d928..27e457b93c84 100644
--- a/include/uapi/linux/capability.h
+++ b/include/uapi/linux/capability.h
@@ -369,7 +369,11 @@ struct vfs_ns_cap_data {
#define CAP_SYS_MOUNT 38
-#define CAP_LAST_CAP CAP_SYS_MOUNT
+/* Allow read/write trusted xattr */
+
+#define CAP_TRUSTED 39
+
+#define CAP_LAST_CAP CAP_TRUSTED
#define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
diff --git a/security/selinux/include/classmap.h
b/security/selinux/include/classmap.h
quoted
index a873dce97fd5..f5dc8e109f5a 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -24,9 +24,10 @@
"audit_control", "setfcap"
#define COMMON_CAP2_PERMS "mac_override", "mac_admin", "syslog", \
- "wake_alarm", "block_suspend", "audit_read", "sys_mount"
+ "wake_alarm", "block_suspend", "audit_read", "sys_mount", \
+ "trusted"
-#if CAP_LAST_CAP > CAP_SYS_MOUNT
+#if CAP_LAST_CAP > CAP_TRUSTED
#error New capability defined, please update COMMON_CAP2_PERMS.
#endif
Nicolas