Restrict the ability to set SELinux enforcing mode to init.

Also make su and shell permissive in non-user builds to allow
use of setenforce without violating the neverallow rule.

Change-Id: Ie76ee04e90d5a76dfaa5f56e9e3eb7e283328a3f
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>

Android.mk

@@ -11,8 +11,10 @@ MLS_SENS=1
 MLS_CATS=1024
 
 ifeq ($(TARGET_BUILD_VARIANT),user)
+	BOARD_SEPOLICY_IGNORE+=external/sepolicy/shell.te
 	BOARD_SEPOLICY_IGNORE+=external/sepolicy/su.te
 else
+	BOARD_SEPOLICY_IGNORE+=external/sepolicy/shell_user.te
 	BOARD_SEPOLICY_IGNORE+=external/sepolicy/su_user.te
 endif
 

domain.te

@@ -131,8 +131,8 @@ neverallow { domain -relabeltodomain } *:dir_file_class_set relabelto;
 ### neverallow rules
 ###
 
-# Only init should be able to load SELinux policies
-neverallow { domain -init } kernel:security load_policy;
+# Only init should be able to load SELinux policies and set enforcing mode.
+neverallow { domain -init } kernel:security { load_policy setenforce };
 
 # Only init, ueventd and system_server should be able to access HW RNG
 neverallow { domain -init -system_server -ueventd -unconfineddomain } hw_random_device:chr_file *;

init.te

@@ -8,4 +8,4 @@ relabelto_domain(init)
 allow init unlabeled:filesystem mount;
 
 allow init {fs_type dev_type file_type}:dir_file_class_set relabelto;
-allow init kernel:security load_policy;
+allow init kernel:security { load_policy setenforce };

shell.te

@@ -6,3 +6,6 @@ unconfined_domain(shell)
 # Run app_process.
 # XXX Split into its own domain?
 app_domain(shell)
+
+# shell is also permissive to permit setenforce.
+permissive shell;

shell_user.te

+# Domain for shell processes spawned by ADB
+type shell, domain;
+type shell_exec, exec_type, file_type;
+unconfined_domain(shell)
+
+# Run app_process.
+# XXX Split into its own domain?
+app_domain(shell)

su.te

@@ -4,3 +4,6 @@ domain_auto_trans(shell, su_exec, su)
 
 # su is unconfined.
 unconfined_domain(su)
+
+# su is also permissive to permit setenforce.
+permissive su;

te_macros

@@ -250,13 +250,9 @@ allow $1 rootfs:file r_file_perms;
 
 #####################################
 # selinux_manage_policy(domain)
-# Ability to manage policy files,
-# trigger runtime reload, change
-# enforcing mode, manipulate booleans
-# and access kernel logs.
+# Ability to manage policy files and
+# trigger runtime reload.
 define(`selinux_manage_policy', `
-selinux_setenforce($1)
-selinux_setbool($1)
 security_access_policy($1)
 unix_socket_connect($1, property, init)
 allow $1 security_file:dir create_dir_perms;

unconfined.te

@@ -17,7 +17,7 @@
 ######################################################
 
 allow unconfineddomain self:capability_class_set *;
-allow unconfineddomain kernel:security ~load_policy;
+allow unconfineddomain kernel:security ~{ load_policy setenforce };
 allow unconfineddomain kernel:system *;
 allow unconfineddomain self:memprotect *;
 allow unconfineddomain domain:process *;