Only enforce per-app process and file isolation via SELinux for third party apps, not platform apps.
Platform (any of the apps signed by build keys, i.e. platform|release|shared|media) apps expect to be able to share files with each other or with third party apps by passing open files or pathnames over Binder. Therefore, we switch to only enforcing the per-app process and file isolation via SELinux on third party apps, not platform apps.
Make the platform app domains mlstrustedsubjects so that they can access any files created by third party apps.
Introduce a new platform_app_data_file type for platform apps so that we can mark it as a mlstrustedobject and allow third party apps to read/write files created by the platform apps.
Specify this new type for the platform app entries in seapp_contexts.
Remove levelFromUid=true for the platform apps in seapp_contexts since we are no longer enforcing per-app separation among them.
diff --git a/seapp_contexts b/seapp_contexts
index 502206a..088937b 100644
--- a/seapp_contexts
+++ b/seapp_contexts
@@ -33,8 +33,8 @@
user=nfc domain=nfc type=nfc_data_file
user=radio domain=radio type=radio_data_file
user=app_* domain=untrusted_app type=app_data_file levelFromUid=true
-user=app_* seinfo=platform domain=platform_app levelFromUid=true
-user=app_* seinfo=shared domain=shared_app levelFromUid=true
-user=app_* seinfo=media domain=media_app levelFromUid=true
-user=app_* seinfo=release domain=release_app levelFromUid=true
-user=app_* seinfo=release name=com.android.browser domain=browser_app levelFromUid=true
+user=app_* seinfo=platform domain=platform_app type=platform_app_data_file
+user=app_* seinfo=shared domain=shared_app type=platform_app_data_file
+user=app_* seinfo=media domain=media_app type=platform_app_data_file
+user=app_* seinfo=release domain=release_app type=platform_app_data_file
+user=app_* seinfo=release name=com.android.browser domain=browser_app type=platform_app_data_file