linux-kernel - [RFC PATCH 1/2] security, capabilities: create CAP

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Message-Id: <20171021134558.21195-1-nicolas@belouin.fr>
Date:   Sat, 21 Oct 2017 15:45:57 +0200
From:   Nicolas Belouin <nicolas@...ouin.fr>
To:     Jan Kara <jack@...e.com>, "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <yuchao0@...wei.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Dave Kleikamp <shaggy@...nel.org>,
        Mark Fasheh <mfasheh@...sity.com>,
        Joel Becker <jlbec@...lplan.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Phillip Lougher <phillip@...ashfs.org.uk>,
        Richard Weinberger <richard@....at>,
        Artem Bityutskiy <dedekind1@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Serge Hallyn <serge@...lyn.com>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Eric Paris <eparis@...isplace.org>,
        James Morris <james.l.morris@...cle.com>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        jfs-discussion@...ts.sourceforge.net, ocfs2-devel@....oracle.com,
        linux-unionfs@...r.kernel.org, reiserfs-devel@...r.kernel.org,
        linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov,
        linux-api@...r.kernel.org, kernel-hardening@...ts.openwall.com
Cc:     Nicolas Belouin <nicolas@...ouin.fr>
Subject: [RFC PATCH 1/2] security, capabilities: create CAP_TRUSTED

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.

Signed-off-by: Nicolas Belouin <nicolas@...ouin.fr>
---
 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
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
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
 
-- 
2.14.2