Opt-out for always-on VPN

Always-on VPN is a feature introduced in N. Since then, all VPN apps
targeting N+ are assumed to support the feature, and the user or the DPC
can turn on / off always-on for any such VPN app. However, a few VPN
apps are not designed to support the always-on feature. Enabling
always-on for these apps will result in undefined behavior and confusing
"Always-on VPN disconnected" notification.

This feature provides a new manifest meta-data field through which a VPN
app can opt out of the always-on feature explicitly. This will stop the
always-on feature from being enabled for the app, both by the user and
by the DPC, and will clear its existing always-on state.

A @hide API is provided to check whether an app supports always-on VPN.
Documentation is updated to reflect the behavior change.

Bug: 36650087
Test: runtest --path java/com/android/server/connectivity/VpnTest.java
Test: cts-tradefed run cts --module CtsDevicePolicyManagerTestCases --test 'com.android.cts.devicepolicy.MixedDeviceOwnerTest#testAlwaysOnVpnUnsupportedPackage'
Test: cts-tradefed run cts --module CtsDevicePolicyManagerTestCases --test 'com.android.cts.devicepolicy.MixedDeviceOwnerTest#testAlwaysOnVpnUnsupportedPackageReplaced'
Test: cts-tradefed run cts --module CtsDevicePolicyManagerTestCases --test 'com.android.cts.devicepolicy.MixedProfileOwnerTest#testAlwaysOnVpnUnsupportedPackage'
Test: cts-tradefed run cts --module CtsDevicePolicyManagerTestCases --test 'com.android.cts.devicepolicy.MixedProfileOwnerTest#testAlwaysOnVpnUnsupportedPackageReplaced'
Test: cts-tradefed run cts --module CtsDevicePolicyManagerTestCases --test 'com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testAlwaysOnVpnUnsupportedPackage'
Test: cts-tradefed run cts --module CtsDevicePolicyManagerTestCases --test 'com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testAlwaysOnVpnUnsupportedPackageReplaced'

Change-Id: I477897a29175e3994d4ecf8ec546e26043c90f13
Merged-In: I477897a29175e3994d4ecf8ec546e26043c90f13
(cherry picked from commit 9369e61e2d)

core/java/android/net/ConnectivityManager.java

@@ -834,6 +834,29 @@ public class ConnectivityManager {
         }
     }
 
+    /**
+     * Checks if a VPN app supports always-on mode.
+     *
+     * In order to support the always-on feature, an app has to
+     * <ul>
+     *     <li>target {@link VERSION_CODES#N API 24} or above, and
+     *     <li>not opt out through the {@link VpnService#METADATA_SUPPORTS_ALWAYS_ON} meta-data
+     *         field.
+     * </ul>
+     *
+     * @param userId The identifier of the user for whom the VPN app is installed.
+     * @param vpnPackage The canonical package name of the VPN app.
+     * @return {@code true} if and only if the VPN app exists and supports always-on mode.
+     * @hide
+     */
+    public boolean isAlwaysOnVpnPackageSupportedForUser(int userId, @Nullable String vpnPackage) {
+        try {
+            return mService.isAlwaysOnVpnPackageSupported(userId, vpnPackage);
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
     /**
      * Configures an always-on VPN connection through a specific application.
      * This connection is automatically granted and persisted after a reboot.

core/java/android/net/IConnectivityManager.aidl

@@ -123,6 +123,7 @@ interface IConnectivityManager
     VpnInfo[] getAllVpnInfo();
 
     boolean updateLockdownVpn();
+    boolean isAlwaysOnVpnPackageSupported(int userId, String packageName);
     boolean setAlwaysOnVpnPackage(int userId, String packageName, boolean lockdown);
     String getAlwaysOnVpnPackage(int userId);
 

services/core/java/com/android/server/ConnectivityService.java

@@ -128,9 +128,9 @@ import com.android.server.LocalServices;
 import com.android.server.am.BatteryStatsService;
 import com.android.server.connectivity.DataConnectionStats;
 import com.android.server.connectivity.KeepaliveTracker;
+import com.android.server.connectivity.LingerMonitor;
 import com.android.server.connectivity.MockableSystemProperties;
 import com.android.server.connectivity.Nat464Xlat;
-import com.android.server.connectivity.LingerMonitor;
 import com.android.server.connectivity.NetworkAgentInfo;
 import com.android.server.connectivity.NetworkDiagnostics;
 import com.android.server.connectivity.NetworkMonitor;
@@ -1515,6 +1515,12 @@ public class ConnectivityService extends IConnectivityManager.Stub
         ConnectivityManager.enforceChangePermission(mContext);
     }
 
+    private void enforceSettingsPermission() {
+        mContext.enforceCallingOrSelfPermission(
+                android.Manifest.permission.NETWORK_SETTINGS,
+                "ConnectivityService");
+    }
+
     private void enforceTetherAccessPermission() {
         mContext.enforceCallingOrSelfPermission(
                 android.Manifest.permission.ACCESS_NETWORK_STATE,
@@ -3645,6 +3651,21 @@ public class ConnectivityService extends IConnectivityManager.Stub
         }
     }
 
+    @Override
+    public boolean isAlwaysOnVpnPackageSupported(int userId, String packageName) {
+        enforceSettingsPermission();
+        enforceCrossUserPermission(userId);
+
+        synchronized (mVpns) {
+            Vpn vpn = mVpns.get(userId);
+            if (vpn == null) {
+                Slog.w(TAG, "User " + userId + " has no Vpn configuration");
+                return false;
+            }
+            return vpn.isAlwaysOnPackageSupported(packageName);
+        }
+    }
+
     @Override
     public boolean setAlwaysOnVpnPackage(int userId, String packageName, boolean lockdown) {
         enforceConnectivityInternalPermission();

tests/net/java/com/android/server/connectivity/VpnTest.java

@@ -27,13 +27,16 @@ import android.annotation.UserIdInt;
 import android.app.AppOpsManager;
 import android.app.NotificationManager;
 import android.content.Context;
-import android.content.Intent;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
+import android.content.pm.ResolveInfo;
+import android.content.pm.ServiceInfo;
 import android.content.pm.UserInfo;
 import android.net.NetworkInfo.DetailedState;
 import android.net.UidRange;
-import android.os.Build;
+import android.net.VpnService;
+import android.os.Build.VERSION_CODES;
+import android.os.Bundle;
 import android.os.INetworkManagementService;
 import android.os.Looper;
 import android.os.UserHandle;
@@ -45,22 +48,22 @@ import android.util.ArraySet;
 
 import com.android.internal.net.VpnConfig;
 
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Map;
-import java.util.Set;
-
 import org.mockito.Answers;
-import org.mockito.ArgumentCaptor;
 import org.mockito.InOrder;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+
 /**
  * Tests for {@link Vpn}.
  *
  * Build, install and run with:
- *  runtest --path src/com/android/server/connectivity/VpnTest.java
+ *  runtest --path java/com/android/server/connectivity/VpnTest.java
  */
 public class VpnTest extends AndroidTestCase {
     private static final String TAG = "VpnTest";
@@ -116,7 +119,7 @@ public class VpnTest extends AndroidTestCase {
 
         // Used by {@link Notification.Builder}
         ApplicationInfo applicationInfo = new ApplicationInfo();
-        applicationInfo.targetSdkVersion = Build.VERSION_CODES.CUR_DEVELOPMENT;
+        applicationInfo.targetSdkVersion = VERSION_CODES.CUR_DEVELOPMENT;
         when(mContext.getApplicationInfo()).thenReturn(applicationInfo);
 
         doNothing().when(mNetService).registerObserver(any());
@@ -314,6 +317,40 @@ public class VpnTest extends AndroidTestCase {
         order.verify(mNetService).setAllowOnlyVpnForUids(eq(true), aryEq(entireUser));
     }
 
+    @SmallTest
+    public void testIsAlwaysOnPackageSupported() throws Exception {
+        final Vpn vpn = createVpn(primaryUser.id);
+
+        ApplicationInfo appInfo = new ApplicationInfo();
+        when(mPackageManager.getApplicationInfoAsUser(eq(PKGS[0]), anyInt(), eq(primaryUser.id)))
+                .thenReturn(appInfo);
+
+        ServiceInfo svcInfo = new ServiceInfo();
+        ResolveInfo resInfo = new ResolveInfo();
+        resInfo.serviceInfo = svcInfo;
+        when(mPackageManager.queryIntentServicesAsUser(any(), eq(PackageManager.GET_META_DATA),
+                eq(primaryUser.id)))
+                .thenReturn(Collections.singletonList(resInfo));
+
+        // null package name should return false
+        assertFalse(vpn.isAlwaysOnPackageSupported(null));
+
+        // Pre-N apps are not supported
+        appInfo.targetSdkVersion = VERSION_CODES.M;
+        assertFalse(vpn.isAlwaysOnPackageSupported(PKGS[0]));
+
+        // N+ apps are supported by default
+        appInfo.targetSdkVersion = VERSION_CODES.N;
+        assertTrue(vpn.isAlwaysOnPackageSupported(PKGS[0]));
+
+        // Apps that opt out explicitly are not supported
+        appInfo.targetSdkVersion = VERSION_CODES.CUR_DEVELOPMENT;
+        Bundle metaData = new Bundle();
+        metaData.putBoolean(VpnService.METADATA_SUPPORTS_ALWAYS_ON, false);
+        svcInfo.metaData = metaData;
+        assertFalse(vpn.isAlwaysOnPackageSupported(PKGS[0]));
+    }
+
     @SmallTest
     public void testNotificationShownForAlwaysOnApp() {
         final UserHandle userHandle = UserHandle.of(primaryUser.id);