sepolicy: restrict /vendor/app from most coredomains

The change makes 'vendor_app_file' accessible only to few platform
domains like dex2oat, idmap, installd, system_server and appdomain.

Bug: 36681210
Test: Boot sailfish (treble device) from wiped flashall
Test: Connect to wifi and launch chrome to load few websites.
Test: Launch camera and record + playback video

Change-Id: Ib8757fedbf2e19c8381c8cd0f8f2693b2345534b
Signed-off-by: Sandeep Patil <sspatil@google.com>

private/app.te

@@ -94,6 +94,10 @@ allow { appdomain -ephemeral_app -untrusted_v2_app } toolbox_exec:file rx_file_p
 allow appdomain system_file:dir r_dir_perms;
 allow appdomain system_file:lnk_file { getattr open read };
 
+# Allow apps access to /vendor/app except for privileged
+# apps which cannot be in /vendor.
+r_dir_file({ appdomain -ephemeral_app -untrusted_v2_app }, vendor_app_file)
+
 # Execute dex2oat when apps call dexclassloader
 allow appdomain dex2oat_exec:file rx_file_perms;
 

public/dex2oat.te

@@ -3,6 +3,8 @@ type dex2oat, domain, domain_deprecated;
 type dex2oat_exec, exec_type, file_type;
 
 r_dir_file(dex2oat, apk_data_file)
+# Access to /vendor/app
+r_dir_file(dex2oat, vendor_app_file)
 
 allow dex2oat tmpfs:file { read getattr };
 

public/domain.te

@@ -131,11 +131,6 @@ full_treble_only(`
     # through linker/loader.
     allow domain vendor_file:dir { getattr search };
 
-    # TODO: b/36681210, find out who needs access and only allow
-    # specific domains for Treble
-    allow domain vendor_app_file:dir r_dir_perms;
-    allow domain vendor_app_file:file { read open getattr };
-
     # Some apps (com.android.phone) need to be able to open
     # symlinked libraries
     # TODO: b/36806861
@@ -689,6 +684,31 @@ full_treble_only(`
   }:sock_file ~{ append getattr ioctl read write };
 ')
 
+# On TREBLE devices, a limited set of files in /vendor are accessible to
+# only a few whitelisted coredomains to keep system/vendor separation.
+full_treble_only(`
+    # Limit access to /vendor/app except for whitelisted domains
+    neverallow {
+        coredomain
+        -appdomain
+        -dex2oat
+        -idmap
+        -init
+        -installd
+        -system_server
+    } vendor_app_file:dir { open read getattr search };
+
+    neverallow {
+        coredomain
+        -appdomain
+        -dex2oat
+        -idmap
+        -init
+        -installd
+        -system_server
+    } vendor_app_file:{ file lnk_file } r_file_perms;
+')
+
 # Only authorized processes should be writing to files in /data/dalvik-cache
 neverallow {
   domain
@@ -908,6 +928,7 @@ neverallow {
   userdebug_or_eng(`-uncrypt')
 } shell_data_file:file open;
 
+
 # servicemanager is the only process which handles list request
 neverallow * ~servicemanager:service_manager list;
 

public/idmap.te

@@ -9,3 +9,6 @@ allow idmap resourcecache_data_file:file { getattr read write };
 # Open and read from target and overlay apk files passed by argument.
 allow idmap apk_data_file:file r_file_perms;
 allow idmap apk_data_file:dir search;
+
+# Allow apps access to /vendor/app
+r_dir_file(idmap, vendor_app_file)

public/installd.te

@@ -27,6 +27,8 @@ selinux_check_context(installd)
 r_dir_file(installd, rootfs)
 # Scan through APKs in /system/app and /system/priv-app
 r_dir_file(installd, system_file)
+# Scan through APKs in /vendor/app
+r_dir_file(installd, vendor_app_file)
 # Get file context
 allow installd file_contexts_file:file r_file_perms;
 # Get seapp_context