Expose a SystemApi method to prepare a VPN without consent.

This is NOT designed to be called normally. Most apps (even
system-privileged ones) should request user consent before launching a
VPN. However, it is needed to support flows where consent can be
obtained through other means external to the VPN flow itself.

The API requires a system-privileged permission, CONTROL_VPN.

Bug: 18327583
Change-Id: I1bcdcf0fb5707faeb861ec4535e7ccffea369ae7

core/java/android/net/VpnService.java

@@ -19,6 +19,7 @@ package android.net;
 import static android.system.OsConstants.AF_INET;
 import static android.system.OsConstants.AF_INET6;
 
+import android.annotation.SystemApi;
 import android.app.Activity;
 import android.app.PendingIntent;
 import android.app.Service;
@@ -163,6 +164,32 @@ public class VpnService extends Service {
         return VpnConfig.getIntentForConfirmation();
     }
 
+    /**
+     * Version of {@link #prepare(Context)} which does not require user consent.
+     *
+     * <p>Requires {@link android.Manifest.permission#CONTROL_VPN} and should generally not be
+     * used. Only acceptable in situations where user consent has been obtained through other means.
+     *
+     * <p>Once this is run, future preparations may be done with the standard prepare method as this
+     * will authorize the package to prepare the VPN without consent in the future.
+     *
+     * @hide
+     */
+    @SystemApi
+    public static void prepareAndAuthorize(Context context) {
+        IConnectivityManager cm = getService();
+        String packageName = context.getPackageName();
+        try {
+            // Only prepare if we're not already prepared.
+            if (!cm.prepareVpn(packageName, null)) {
+                cm.prepareVpn(null, packageName);
+            }
+            cm.setVpnPackageAuthorization(true);
+        } catch (RemoteException e) {
+            // ignore
+        }
+    }
+
     /**
      * Protect a socket from VPN connections. After protecting, data sent
      * through this socket will go directly to the underlying network,

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

@@ -2813,9 +2813,8 @@ public class ConnectivityService extends IConnectivityManager.Stub
     }
 
     /**
-     * Prepare for a VPN application. This method is used by VpnDialogs
+     * Prepare for a VPN application. This method is used by system-privileged apps.
-     * and not available in ConnectivityManager. Permissions are checked
+     * Permissions are checked in Vpn class.
-     * in Vpn class.
      * @hide
      */
     @Override
@@ -2829,8 +2828,8 @@ public class ConnectivityService extends IConnectivityManager.Stub
 
     /**
      * Set whether the current VPN package has the ability to launch VPNs without
-     * user intervention. This method is used by system UIs and not available
+     * user intervention. This method is used by system-privileged apps.
-     * in ConnectivityManager. Permissions are checked in Vpn class.
+     * Permissions are checked in Vpn class.
      * @hide
      */
     @Override