Add API for NetworkStack to start captive portal

Endpoints protected with INTERACT_ACROSS_USERS_FULL, such as
startActivityAsUser, should only be used by modules signed with the
platform cert. The NetworkStack needs to have the system server start
the application so this restriction can be applied.

Bug: 123846255
Test: flashed, captive portal works from primary and secondary user
Change-Id: Ib3e427b3fd03ced80c02985e795f79b096a2ec9a

core/java/android/net/ConnectivityManager.java

@@ -3866,6 +3866,25 @@ public class ConnectivityManager {
         }
     }
 
+    /**
+     * Requests that the system open the captive portal app with the specified extras.
+     *
+     * <p>This endpoint is exclusively for use by the NetworkStack and is protected by the
+     * corresponding permission.
+     * @param appExtras Extras to include in the app start intent.
+     * @hide
+     */
+    @SystemApi
+    @TestApi
+    @RequiresPermission(NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK)
+    public void startCaptivePortalApp(Bundle appExtras) {
+        try {
+            mService.startCaptivePortalAppInternal(appExtras);
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
     /**
      * Determine whether the device is configured to avoid bad wifi.
      * @hide

core/java/android/net/IConnectivityManager.aidl

@@ -27,6 +27,7 @@ import android.net.NetworkQuotaInfo;
 import android.net.NetworkRequest;
 import android.net.NetworkState;
 import android.net.ProxyInfo;
+import android.os.Bundle;
 import android.os.IBinder;
 import android.os.Messenger;
 import android.os.ParcelFileDescriptor;
@@ -167,6 +168,7 @@ interface IConnectivityManager
     void setAcceptUnvalidated(in Network network, boolean accept, boolean always);
     void setAvoidUnvalidated(in Network network);
     void startCaptivePortalApp(in Network network);
+    void startCaptivePortalAppInternal(in Bundle appExtras);
 
     boolean getAvoidBadWifi();
     int getMultipathPreference(in Network Network);

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

@@ -3230,6 +3230,25 @@ public class ConnectivityService extends IConnectivityManager.Stub
         });
     }
 
+    /**
+     * NetworkStack endpoint to start the captive portal app. The NetworkStack needs to use this
+     * endpoint as it does not have INTERACT_ACROSS_USERS_FULL itself.
+     * @param appExtras Bundle to use as intent extras for the captive portal application.
+     *                  Must be treated as opaque to avoid preventing the captive portal app to
+     *                  update its arguments.
+     */
+    @Override
+    public void startCaptivePortalAppInternal(Bundle appExtras) {
+        mContext.checkCallingOrSelfPermission(NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK);
+
+        final Intent appIntent = new Intent(ConnectivityManager.ACTION_CAPTIVE_PORTAL_SIGN_IN);
+        appIntent.putExtras(appExtras);
+        appIntent.setFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT | Intent.FLAG_ACTIVITY_NEW_TASK);
+
+        Binder.withCleanCallingIdentity(() ->
+                mContext.startActivityAsUser(appIntent, UserHandle.CURRENT));
+    }
+
     public boolean avoidBadWifi() {
         return mMultinetworkPolicyTracker.getAvoidBadWifi();
     }