Pass privapp specifier for selinux labeling

Allow privileged apps to run in their own priv_app domain.

Motivation:
Untrusted_app is overprivileged due to the inclusion of privileged
apps like gmscore, play store and finsky. Moving these and other
privileged apps to their own domain reduces the permissions required
by untrusted_app.

A separate priv_app domain also protects priv-apps by further
isolating them from third party apps.

Bug: 22033466
Change-Id: I8e6ae5677c5a978301c453d0aa51ebed4459f5a0

services/core/java/com/android/server/pm/SELinuxMMAC.java

@@ -100,6 +100,9 @@ public final class SELinuxMMAC {
     private static final String SEAPP_HASH_FILE =
             Environment.getDataDirectory().toString() + "/system/seapp_hash";
 
+    // Append privapp to existing seinfo label
+    private static final String PRIVILEGED_APP_STR = ":privapp";
+
     /**
      * Load the mac_permissions.xml file containing all seinfo assignments used to
      * label apps. The loaded mac_permissions.xml file is determined by the
@@ -313,6 +316,9 @@ public final class SELinuxMMAC {
             }
         }
 
+        if (pkg.applicationInfo.isPrivilegedApp())
+            pkg.applicationInfo.seinfo += PRIVILEGED_APP_STR;
+
         if (DEBUG_POLICY_INSTALL) {
             Slog.i(TAG, "package (" + pkg.packageName + ") labeled with " +
                     "seinfo=" + pkg.applicationInfo.seinfo);