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.

1 files changed, 41 insertions, 0 deletions

diff --git a/src/shared/apparmor-util.c b/src/shared/apparmor-util.c
new file mode 100644
index 0000000000..2b85da1e4a
--- /dev/null
+++ b/src/shared/apparmor-util.c
@@ -0,0 +1,41 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2013 Lennart Poettering
+
+  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 "util.h"
+#include "fileio.h"
+#include "apparmor-util.h"
+
+static int use_apparmor_cached = -1;
+
+bool use_apparmor(void) {
+
+        if (use_apparmor_cached < 0) {
+                _cleanup_free_ char *p = NULL;
+
+                use_apparmor_cached =
+                        read_one_line_file("/sys/module/apparmor/parameters/enabled", &p) >= 0 &&
+                        parse_boolean(p) > 0;
+        }
+
+        return use_apparmor_cached;
+}