init: split security functions out of init.cpp

This change splits out the selinux initialization and supporting
functionality into selinux.cpp and splits the security related
initialization of the rng, etc to security.cpp.  It also provides
additional documentation for SEPolicy loading as this has been
requested by some teams.

It additionally cleans up sehandle and sehandle_prop.  The former is
static within selinux.cpp and new wrapper functions are created around
selabel_lookup*() to better serve the users.  The latter is moved to
property_service.cpp as it is isolated to that file for its usage.

Test: boot bullhead
Merged-In: Idc95d493cebc681fbe686b5160502f36af149f60
Change-Id: Idc95d493cebc681fbe686b5160502f36af149f60
(cherry picked from commit 9afb86b25d8675927cb37c86119a7ecf19f74819)
diff --git a/init/property_service.cpp b/init/property_service.cpp
index fd14bd6..bd42913 100644
--- a/init/property_service.cpp
+++ b/init/property_service.cpp
@@ -68,6 +68,8 @@
 
 static int property_set_fd = -1;
 
+static struct selabel_handle* sehandle_prop;
+
 void property_init() {
     if (__system_property_area_init()) {
         LOG(ERROR) << "Failed to initialize property area";
@@ -740,11 +742,30 @@
     load_recovery_id_prop();
 }
 
+static int SelinuxAuditCallback(void* data, security_class_t /*cls*/, char* buf, size_t len) {
+    property_audit_data* d = reinterpret_cast<property_audit_data*>(data);
+
+    if (!d || !d->name || !d->cr) {
+        LOG(ERROR) << "AuditCallback invoked with null data arguments!";
+        return 0;
+    }
+
+    snprintf(buf, len, "property=%s pid=%d uid=%d gid=%d", d->name, d->cr->pid, d->cr->uid,
+             d->cr->gid);
+    return 0;
+}
+
 void start_property_service() {
+    sehandle_prop = selinux_android_prop_context_handle();
+
+    selinux_callback cb;
+    cb.func_audit = SelinuxAuditCallback;
+    selinux_set_callback(SELINUX_CB_AUDIT, cb);
+
     property_set("ro.property_service.version", "2");
 
     property_set_fd = CreateSocket(PROP_SERVICE_NAME, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
-                                   false, 0666, 0, 0, nullptr, sehandle);
+                                   false, 0666, 0, 0, nullptr);
     if (property_set_fd == -1) {
         PLOG(ERROR) << "start_property_service socket creation failed";
         exit(1);