diff --git a/include/cutils/multiuser.h b/include/cutils/multiuser.h
index 4f23776..5bd9c7b 100644
--- a/include/cutils/multiuser.h
+++ b/include/cutils/multiuser.h
@@ -32,6 +32,7 @@
 extern uid_t multiuser_get_uid(userid_t user_id, appid_t app_id);
 
 extern gid_t multiuser_get_cache_gid(userid_t user_id, appid_t app_id);
+extern gid_t multiuser_get_ext_gid(userid_t user_id, appid_t app_id);
 extern gid_t multiuser_get_shared_gid(userid_t user_id, appid_t app_id);
 
 /* TODO: switch callers over to multiuser_get_shared_gid() */
diff --git a/include/private/android_filesystem_config.h b/include/private/android_filesystem_config.h
index 7db28d8..8e2bc1c 100644
--- a/include/private/android_filesystem_config.h
+++ b/include/private/android_filesystem_config.h
@@ -127,6 +127,7 @@
 #define AID_MEDIA_VIDEO   1056 /* GID for video files on internal media storage */
 #define AID_MEDIA_IMAGE   1057 /* GID for image files on internal media storage */
 #define AID_TOMBSTONED    1058  /* tombstoned user */
+#define AID_MEDIA_OBB     1059 /* GID for OBB files on internal media storage */
 /* Changes to this file must be made in AOSP, *not* in internal branches. */
 
 #define AID_SHELL         2000  /* adb and debug shell user */
@@ -165,6 +166,9 @@
 #define AID_CACHE_GID_START  20000 /* start of gids for apps to mark cached data */
 #define AID_CACHE_GID_END    29999 /* end of gids for apps to mark cached data */
 
+#define AID_EXT_GID_START    30000 /* start of gids for apps to mark external data */
+#define AID_EXT_GID_END      39999 /* end of gids for apps to mark external data */
+
 #define AID_SHARED_GID_START 50000 /* start of gids for apps in each user to share */
 #define AID_SHARED_GID_END   59999 /* end of gids for apps in each user to share */
 
diff --git a/libcutils/multiuser.c b/libcutils/multiuser.c
index 0ef337d..08d4d6c 100644
--- a/libcutils/multiuser.c
+++ b/libcutils/multiuser.c
@@ -37,6 +37,14 @@
     }
 }
 
+gid_t multiuser_get_ext_gid(userid_t user_id, appid_t app_id) {
+    if (app_id >= AID_APP_START && app_id <= AID_APP_END) {
+        return multiuser_get_uid(user_id, (app_id - AID_APP_START) + AID_EXT_GID_START);
+    } else {
+        return -1;
+    }
+}
+
 gid_t multiuser_get_shared_gid(userid_t user_id, appid_t app_id) {
     if (app_id >= AID_APP_START && app_id <= AID_APP_END) {
         return multiuser_get_uid(user_id, (app_id - AID_APP_START) + AID_SHARED_GID_START);
diff --git a/libcutils/tests/multiuser_test.cpp b/libcutils/tests/multiuser_test.cpp
index 2307ea8..c5f58b4 100644
--- a/libcutils/tests/multiuser_test.cpp
+++ b/libcutils/tests/multiuser_test.cpp
@@ -58,6 +58,14 @@
     EXPECT_EQ(1020000, multiuser_get_cache_gid(10, 10000));
 }
 
+TEST(MultiuserTest, TestExt) {
+    EXPECT_EQ(-1, multiuser_get_ext_gid(0, 0));
+    EXPECT_EQ(-1, multiuser_get_ext_gid(0, 1000));
+    EXPECT_EQ(30000, multiuser_get_ext_gid(0, 10000));
+    EXPECT_EQ(-1, multiuser_get_ext_gid(0, 50000));
+    EXPECT_EQ(1030000, multiuser_get_ext_gid(10, 10000));
+}
+
 TEST(MultiuserTest, TestShared) {
     EXPECT_EQ(-1, multiuser_get_shared_gid(0, 0));
     EXPECT_EQ(-1, multiuser_get_shared_gid(0, 1000));