diff --git a/api/system-current.txt b/api/system-current.txt
index 9cfe604..2b72763 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -3186,6 +3186,10 @@
     field public static final String EXTRA_PACKAGE_NAME = "packageName";
   }
 
+  public class NetworkStack {
+    field public static final String PERMISSION_MAINLINE_NETWORK_STACK = "android.permission.MAINLINE_NETWORK_STACK";
+  }
+
   public final class RouteInfo implements android.os.Parcelable {
     ctor public RouteInfo(android.net.IpPrefix, java.net.InetAddress, String, int);
     method public int getType();
diff --git a/api/test-current.txt b/api/test-current.txt
index 1384f0b..e4f999b 100644
--- a/api/test-current.txt
+++ b/api/test-current.txt
@@ -669,6 +669,10 @@
     method public boolean satisfiedByNetworkCapabilities(android.net.NetworkCapabilities);
   }
 
+  public class NetworkStack {
+    field public static final String PERMISSION_MAINLINE_NETWORK_STACK = "android.permission.MAINLINE_NETWORK_STACK";
+  }
+
   public final class RouteInfo implements android.os.Parcelable {
     ctor public RouteInfo(android.net.IpPrefix, java.net.InetAddress, String, int);
     method public int getType();
diff --git a/core/java/android/net/NetworkStack.java b/core/java/android/net/NetworkStack.java
index ac6bff0..ec38ac1 100644
--- a/core/java/android/net/NetworkStack.java
+++ b/core/java/android/net/NetworkStack.java
@@ -20,7 +20,9 @@
 
 import android.annotation.NonNull;
 import android.annotation.Nullable;
+import android.annotation.SystemApi;
 import android.annotation.SystemService;
+import android.annotation.TestApi;
 import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
@@ -46,9 +48,22 @@
  * @hide
  */
 @SystemService(Context.NETWORK_STACK_SERVICE)
+@SystemApi
+@TestApi
 public class NetworkStack {
     private static final String TAG = NetworkStack.class.getSimpleName();
 
+    /**
+     * Permission granted only to the NetworkStack APK, defined in NetworkStackStub with signature
+     * protection level.
+     * @hide
+     */
+    @SystemApi
+    @TestApi
+    public static final String PERMISSION_MAINLINE_NETWORK_STACK =
+            "android.permission.MAINLINE_NETWORK_STACK";
+
+    /** @hide */
     public static final String NETWORKSTACK_PACKAGE_NAME = "com.android.mainline.networkstack";
 
     private static final int NETWORKSTACK_TIMEOUT_MS = 10_000;
@@ -66,12 +81,14 @@
         void onNetworkStackConnected(INetworkStackConnector connector);
     }
 
+    /** @hide */
     public NetworkStack() { }
 
     /**
      * Create a DHCP server according to the specified parameters.
      *
      * <p>The server will be returned asynchronously through the provided callbacks.
+     * @hide
      */
     public void makeDhcpServer(final String ifName, final DhcpServingParamsParcel params,
             final IDhcpServerCallbacks cb) {
@@ -88,6 +105,7 @@
      * Create an IpClient on the specified interface.
      *
      * <p>The IpClient will be returned asynchronously through the provided callbacks.
+     * @hide
      */
     public void makeIpClient(String ifName, IIpClientCallbacks cb) {
         requestConnector(connector -> {
@@ -103,6 +121,7 @@
      * Create a NetworkMonitor.
      *
      * <p>The INetworkMonitor will be returned asynchronously through the provided callbacks.
+     * @hide
      */
     public void makeNetworkMonitor(
             NetworkParcelable network, String name, INetworkMonitorCallbacks cb) {
@@ -153,6 +172,7 @@
      * the system server on devices that do not support the network stack module. The network stack
      * connector will then be delivered asynchronously to clients that requested it before it was
      * started.
+     * @hide
      */
     public void start(Context context) {
         mNetworkStackStartRequested = true;
diff --git a/packages/NetworkStack/Android.bp b/packages/NetworkStack/Android.bp
index b0522f2..d656593 100644
--- a/packages/NetworkStack/Android.bp
+++ b/packages/NetworkStack/Android.bp
@@ -41,4 +41,5 @@
         "NetworkStackLib"
     ],
     manifest: "AndroidManifest.xml",
+    required: ["NetworkStackPermissionStub"],
 }
\ No newline at end of file
diff --git a/packages/NetworkStack/AndroidManifest.xml b/packages/NetworkStack/AndroidManifest.xml
index 5ab833b..ac55bfa 100644
--- a/packages/NetworkStack/AndroidManifest.xml
+++ b/packages/NetworkStack/AndroidManifest.xml
@@ -25,6 +25,8 @@
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
     <uses-permission android:name="android.permission.CONNECTIVITY_INTERNAL" />
     <uses-permission android:name="android.permission.NETWORK_SETTINGS" />
+    <!-- Signature permission defined in NetworkStackStub -->
+    <uses-permission android:name="android.permission.MAINLINE_NETWORK_STACK" />
     <!-- Launch captive portal app as specific user -->
     <uses-permission android:name="android.permission.INTERACT_ACROSS_USERS_FULL" />
     <uses-permission android:name="android.permission.NETWORK_STACK" />
diff --git a/packages/NetworkStackPermissionStub/Android.bp b/packages/NetworkStackPermissionStub/Android.bp
new file mode 100644
index 0000000..94870c9
--- /dev/null
+++ b/packages/NetworkStackPermissionStub/Android.bp
@@ -0,0 +1,27 @@
+//
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+// Stub APK to define permissions for NetworkStack
+android_app {
+    name: "NetworkStackPermissionStub",
+    // TODO: mark app as hasCode=false in manifest once soong stops complaining about apps without
+    // a classes.dex.
+    srcs: ["src/**/*.java"],
+    platform_apis: true,
+    certificate: "platform",
+    privileged: true,
+    manifest: "AndroidManifest.xml",
+}
diff --git a/packages/NetworkStackPermissionStub/AndroidManifest.xml b/packages/NetworkStackPermissionStub/AndroidManifest.xml
new file mode 100644
index 0000000..2ccf5ff
--- /dev/null
+++ b/packages/NetworkStackPermissionStub/AndroidManifest.xml
@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+-->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.android.mainline.networkstack.permissionstub">
+    <!--
+    This package only exists to define the below permissions, and enforce that they are only
+    granted to apps sharing the same signature.
+    Permissions defined here are intended to be used only by the NetworkStack: both
+    NetworkStack and this stub APK are to be signed with a dedicated certificate to ensure
+    that, with the below permissions being signature permissions.
+
+    This APK *must* be installed, even if the NetworkStack app is not installed, because otherwise,
+    any application will be able to define this permission and the system will give that application
+    full access to the network stack.
+     -->
+    <permission android:name="android.permission.MAINLINE_NETWORK_STACK"
+                android:protectionLevel="signature"/>
+
+    <application android:name="com.android.server.NetworkStackPermissionStub"/>
+</manifest>
\ No newline at end of file
diff --git a/packages/NetworkStackPermissionStub/src/com/android/server/NetworkStackPermissionStub.java b/packages/NetworkStackPermissionStub/src/com/android/server/NetworkStackPermissionStub.java
new file mode 100644
index 0000000..01e59d2
--- /dev/null
+++ b/packages/NetworkStackPermissionStub/src/com/android/server/NetworkStackPermissionStub.java
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server;
+
+import android.app.Application;
+
+/**
+ * Empty application for NetworkStackStub that only exists because soong builds complain if APKs
+ * have no source file.
+ */
+public class NetworkStackPermissionStub extends Application {
+}