Label adb keys file and allow access to it.

The /adb_keys entry will only take effect if a restorecon is
applied by init.rc on a kernel that includes the rootfs labeling
support, but does no harm otherwise.

The /data/misc/adb labeling ensures correct labeling of the adb_keys
file created if the device has ro.adb.secure=1 set.

Allow adbd to read the file.

Change-Id: I97b3d86a69681330bba549491a2fb39df6cf20ef
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
diff --git a/file_contexts b/file_contexts
index 1e4b5a6..c4c4a09 100644
--- a/file_contexts
+++ b/file_contexts
@@ -3,7 +3,7 @@
 /			u:object_r:rootfs:s0
 
 # Data files
-/adb_keys		u:object_r:rootfs:s0
+/adb_keys		u:object_r:adb_keys_file:s0
 /default.prop		u:object_r:rootfs:s0
 /fstab\..*		u:object_r:rootfs:s0
 /init\..*		u:object_r:rootfs:s0
@@ -175,6 +175,7 @@
 /data/misc/wifi(/.*)?		u:object_r:wifi_data_file:s0
 /data/misc/camera(/.*)?	u:object_r:camera_calibration_file:s0
 /data/misc/dhcp(/.*)?           u:object_r:dhcp_data_file:s0
+/data/misc/adb(/.*)?            u:object_r:adb_keys_file:s0
 # App sandboxes
 /data/data/.*		u:object_r:app_data_file:s0
 # Wallpaper file.