[SettingsProvider] enforce permission on openFile

Prevent third-party apps to write to ring tone files without permission.

BUG: 222687217
Test: manual debug app
Test: will add a CTS
Change-Id: I759b9674172e2bdb518c1dccfff0f20047343bf0

packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java

@@ -818,6 +818,9 @@ public class SettingsProvider extends ContentProvider {
             getContext().enforceCallingPermission(Manifest.permission.INTERACT_ACROSS_USERS,
                     "Access files from the settings of another user");
         }
+        if (mode.contains("w")) {
+            enforceWritePermission(Manifest.permission.WRITE_SETTINGS);
+        }
         uri = ContentProvider.getUriWithoutUserId(uri);
 
         final String cacheRingtoneSetting;