commit 935bd3e31574ea83db84797b0dee2a6581a19cdf
author Nick Kralevich <nnk@google.com> Wed Jun 26 15:37:26 2013 -0700
committer Nick Kralevich <nnk@google.com> Tue Sep 03 15:55:00 2013 -0700
tree 50a90b98a7703f80fe3553ee8fd86e684540bcb9
parent 56fa0ac6b6e4ca790c0169c21a3106e09cab672c

init: allow disabling selinux via a kernel command line

Create a new "androidboot.selinux" option, to control how userspace
handles SELinux. This kernel command line can have three options:

* disabled
* permissive
* enforcing

"disabled" completely disables userspace support for SELinux. No
policy is ever loaded, nor is the SELinux filesystem /sys/fs/selinux
ever mounted.

"permissive" loads the SELinux policy, but puts SELinux into
permissive mode. SELinux policy violations are logged, but not rejected.

"enforcing", the default, loads the SELinux policy, and places
SELinux into enforcing mode. Policy violations are rejected.

This change addresses post review comments for change
b710ed21dec88c0dde8209264df054c842561589 .

Change-Id: I912583db8e6a0e9c63380de32ad8ffc47a8a440f

init/init.c

diff --git a/init/init.c b/init/init.c
index 4ae5c06..294c2c4 100644
--- a/init/init.c
+++ b/init/init.c
@@ -790,8 +790,52 @@
     sehandle_prop = selinux_android_prop_context_handle();
 }
 
+static bool selinux_is_disabled(void)
+{
+    char tmp[PROP_VALUE_MAX];
+
+    if (access("/sys/fs/selinux", F_OK) != 0) {
+        /* SELinux is not compiled into the kernel, or has been disabled
+         * via the kernel command line "selinux=0".
+         */
+        return true;
+    }
+
+    if ((property_get("ro.boot.selinux", tmp) != 0) && (strcmp(tmp, "disabled") == 0)) {
+        /* SELinux is compiled into the kernel, but we've been told to disable it. */
+        return true;
+    }
+
+    return false;
+}
+
+static bool selinux_is_enforcing(void)
+{
+    char tmp[PROP_VALUE_MAX];
+
+    if (property_get("ro.boot.selinux", tmp) == 0) {
+        /* Property is not set.  Assume enforcing */
+        return true;
+    }
+
+    if (strcmp(tmp, "permissive") == 0) {
+        /* SELinux is in the kernel, but we've been told to go into permissive mode */
+        return false;
+    }
+
+    if (strcmp(tmp, "enforcing") != 0) {
+        ERROR("SELinux: Unknown value of ro.boot.selinux. Got: \"%s\". Assuming enforcing.\n", tmp);
+    }
+
+    return true;
+}
+
 int selinux_reload_policy(void)
 {
+    if (selinux_is_disabled()) {
+        return -1;
+    }
+
     INFO("SELinux: Attempting to reload policy files\n");
 
     if (selinux_android_reload_policy() == -1) {
@@ -816,8 +860,7 @@
 
 static void selinux_initialize(void)
 {
-    if (access("/sys/fs/selinux", F_OK) != 0) {
-        // SELinux is not compiled into this kernel. Fail gracefully.
+    if (selinux_is_disabled()) {
         return;
     }
 
@@ -829,7 +872,9 @@
     }
 
     selinux_init_all_handles();
-    security_setenforce(1);
+    bool is_enforcing = selinux_is_enforcing();
+    INFO("SELinux: security_setenforce(%d)\n", is_enforcing);
+    security_setenforce(is_enforcing);
 }
 
 int main(int argc, char **argv)