security: rework selinux, smack, ima, apparmor detection logic

Always cache the results, and bypass low-level security calls when
the respective subsystem is not enabled.

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/src/udev/smack-util.c b/src/udev/smack-util.c
new file mode 100644
index 0000000000..93c0d4a347
--- /dev/null
+++ b/src/udev/smack-util.c
@@ -0,0 +1,42 @@
+/***
+  This file is part of eudev, forked from systemd.
+
+  Copyright 2013 Intel Corporation
+
+  Author: Auke Kok <auke-jan.h.kok@intel.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <unistd.h>
+#include <string.h>
+#ifdef HAVE_XATTR
+#include <attr/xattr.h>
+#endif
+
+#include "smack-util.h"
+
+bool use_smack(void) {
+#ifdef HAVE_SMACK
+        static int use_smack_cached = -1;
+
+        if (use_smack_cached < 0)
+                use_smack_cached = access("/sys/fs/smackfs/", F_OK) >= 0;
+
+        return use_smack_cached;
+#else
+        return false;
+#endif
+
+}