android/ui: switch lateinint app instance to optional

updates tailscale/corp#12430

The app instance is set in onCreate, but this has a chance to race
with the intent handlers throwing a null pointer exception.

This should ultimately be corrected in the API interface on the caller side, on but
that fix runs deep and still requires care on the part of the caller.  This will,
at least, error out gracefully rather than crashing the application process at the
expense of an action potentially failing.

Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>

android/src/main/java/com/tailscale/ipn/App.kt

@@ -55,15 +55,15 @@ class App : UninitializedApp(), libtailscale.AppContext {
             .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
             .addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN)
             .build()
-    private lateinit var appInstance: App
+    private var appInstance: App? = null
 
     /**
      * Initializes the app (if necessary) and returns the singleton app instance. Always use this
      * function to obtain an App reference to make sure the app initializes.
      */
     @JvmStatic
-    fun get(): App {
+    fun get(): App? {
-      appInstance.initOnce()
+      appInstance?.initOnce()
       return appInstance
     }
   }
@@ -82,6 +82,8 @@ class App : UninitializedApp(), libtailscale.AppContext {
 
   override fun onCreate() {
     super.onCreate()
+    appInstance = this
+
     createNotificationChannel(
         STATUS_CHANNEL_ID,
         getString(R.string.vpn_status),
@@ -92,7 +94,7 @@ class App : UninitializedApp(), libtailscale.AppContext {
         getString(R.string.taildrop_file_transfers),
         getString(R.string.notifications_delivered_when_a_file_is_received_using_taildrop),
         NotificationManagerCompat.IMPORTANCE_DEFAULT)
-    appInstance = this
+
     setUnprotectedInstance(this)
   }
 
@@ -128,7 +130,8 @@ class App : UninitializedApp(), libtailscale.AppContext {
     applicationScope.launch {
       Notifier.state.collect { state ->
         val ableToStartVPN = state > Ipn.State.NeedsMachineAuth
-        // If VPN is stopped, show a disconnected notification. If it is running as a foregrround service, IPNService will show a connected notification.
+        // If VPN is stopped, show a disconnected notification. If it is running as a foregrround
+        // service, IPNService will show a connected notification.
         if (state == Ipn.State.Stopped) {
           notifyStatus(false)
         }
@@ -345,11 +348,11 @@ open class UninitializedApp : Application() {
     // File for shared preferences that are not encrypted.
     private const val UNENCRYPTED_PREFERENCES = "unencrypted"
 
-    private lateinit var appInstance: UninitializedApp
+    private var appInstance: UninitializedApp? = null
     lateinit var notificationManager: NotificationManagerCompat
 
     @JvmStatic
-    fun get(): UninitializedApp {
+    fun get(): UninitializedApp? {
       return appInstance
     }
   }

android/src/main/java/com/tailscale/ipn/IPNService.kt

@@ -27,13 +27,13 @@ open class IPNService : VpnService(), libtailscale.IPNService {
   override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int =
       when (intent?.action) {
         ACTION_STOP_VPN -> {
-          App.get().setWantRunning(false)
+          App.get()?.setWantRunning(false)
           close()
           START_NOT_STICKY
         }
         ACTION_START_VPN -> {
           showForegroundNotification()
-          App.get().setWantRunning(true)
+          App.get()?.setWantRunning(true)
           Libtailscale.requestVPN(this)
           START_STICKY
         }
@@ -41,15 +41,15 @@ open class IPNService : VpnService(), libtailscale.IPNService {
           // This means we were started by Android due to Always On VPN.
           // We show a non-foreground notification because we weren't
           // started as a foreground service.
-          App.get().notifyStatus(true)
+          App.get()?.notifyStatus(true)
-          App.get().setWantRunning(true)
+          App.get()?.setWantRunning(true)
           Libtailscale.requestVPN(this)
           START_STICKY
         }
         else -> {
           // This means that we were restarted after the service was killed
           // (potentially due to OOM).
-          if (UninitializedApp.get().isAbleToStartVPN()) {
+          if (UninitializedApp.get()?.isAbleToStartVPN() == true) {
             showForegroundNotification()
             App.get()
             Libtailscale.requestVPN(this)
@@ -78,7 +78,7 @@ open class IPNService : VpnService(), libtailscale.IPNService {
   private fun showForegroundNotification() {
     startForeground(
         UninitializedApp.STATUS_NOTIFICATION_ID,
-        UninitializedApp.get().buildStatusNotification(true))
+        UninitializedApp.get()?.buildStatusNotification(true))
   }
 
   private fun configIntent(): PendingIntent {

android/src/main/java/com/tailscale/ipn/MainActivity.kt

@@ -11,7 +11,6 @@ import android.content.RestrictionsManager
 import android.content.pm.ActivityInfo
 import android.content.res.Configuration.SCREENLAYOUT_SIZE_LARGE
 import android.content.res.Configuration.SCREENLAYOUT_SIZE_MASK
-import android.net.VpnService
 import android.os.Bundle
 import android.provider.Settings
 import android.util.Log
@@ -117,7 +116,7 @@ class MainActivity : ComponentActivity() {
           if (granted) {
             Log.d("VpnPermission", "VPN permission granted")
             viewModel.setVpnPrepared(true)
-            App.get().startVPN()
+            App.get()?.startVPN()
           } else {
             Log.d("VpnPermission", "VPN permission denied")
             viewModel.setVpnPrepared(false)
@@ -285,7 +284,7 @@ class MainActivity : ComponentActivity() {
   private fun login(urlString: String) {
     // Launch coroutine to listen for state changes. When the user completes login, relaunch
     // MainActivity to bring the app back to focus.
-    App.get().applicationScope.launch {
+    App.get()?.applicationScope?.launch {
       try {
         Notifier.state.collect { state ->
           if (state > Ipn.State.NeedsMachineAuth) {
@@ -324,20 +323,20 @@ class MainActivity : ComponentActivity() {
 
   override fun onResume() {
     super.onResume()
+    App.get()?.let {
       val restrictionsManager =
           this.getSystemService(Context.RESTRICTIONS_SERVICE) as RestrictionsManager
-    lifecycleScope.launch(Dispatchers.IO) { MDMSettings.update(App.get(), restrictionsManager) }
+      lifecycleScope.launch(Dispatchers.IO) { MDMSettings.update(it, restrictionsManager) }
     }
-
-  override fun onStart() {
-    super.onStart()
   }
 
   override fun onStop() {
     super.onStop()
+    App.get()?.let {
       val restrictionsManager =
           this.getSystemService(Context.RESTRICTIONS_SERVICE) as RestrictionsManager
-    lifecycleScope.launch(Dispatchers.IO) { MDMSettings.update(App.get(), restrictionsManager) }
+      lifecycleScope.launch(Dispatchers.IO) { MDMSettings.update(it, restrictionsManager) }
+    }
   }
 
   private fun openApplicationSettings() {

android/src/main/java/com/tailscale/ipn/QuickToggleService.java

@@ -64,11 +64,17 @@ public class QuickToggleService extends TileService {
     public void onClick() {
         boolean r;
         synchronized (lock) {
-            r = UninitializedApp.get().isAbleToStartVPN();
+            UninitializedApp app = UninitializedApp.get();
+            if (app == null) {
+                return;
+            }
+            r = app.isAbleToStartVPN();
         }
         if (r) {
             // Get the application to make sure it initializes
-            App.get();
+            if (App.get() == null) {
+                return;
+            }
             onTileClick();
         } else {
             // Start main activity.

android/src/main/java/com/tailscale/ipn/StartVPNWorker.java

@@ -28,8 +28,12 @@ public final class StartVPNWorker extends Worker {
     @Override
     public Result doWork() {
         UninitializedApp app = UninitializedApp.get();
-        boolean ableToStartVPN = app.isAbleToStartVPN();
+        if (app == null) {
-        if (ableToStartVPN) {
+            android.util.Log.e("StartVPNWorker", "App is not yet initialized, returning failure.");
+            return Result.failure();
+        }
+
+        if (app.isAbleToStartVPN()) {
             if (VpnService.prepare(app) == null) {
                 // We're ready and have permissions, start the VPN
                 app.startVPN();

android/src/main/java/com/tailscale/ipn/StopVPNWorker.java

@@ -23,7 +23,13 @@ public final class StopVPNWorker extends Worker {
     @NonNull
     @Override
     public Result doWork() {
-        UninitializedApp.get().stopVPN();
+        UninitializedApp app = UninitializedApp.get();
+        if (app == null) {
+            android.util.Log.e("StopVPNWorker", "App is not yet initialized, returning failure.");
+            return Result.failure();
+        }
+
+        app.stopVPN();
         return Result.success();
     }
 }

android/src/main/java/com/tailscale/ipn/UseExitNodeWorker.kt

@@ -10,7 +10,6 @@ import androidx.work.CoroutineWorker
 import androidx.work.Data
 import androidx.work.WorkerParameters
 import com.tailscale.ipn.UninitializedApp.Companion.STATUS_CHANNEL_ID
-import com.tailscale.ipn.UninitializedApp.Companion.STATUS_EXIT_NODE_FAILURE_NOTIFICATION_ID
 import com.tailscale.ipn.ui.localapi.Client
 import com.tailscale.ipn.ui.model.Ipn
 import com.tailscale.ipn.ui.notifier.Notifier
@@ -18,40 +17,40 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 
-class UseExitNodeWorker(
+class UseExitNodeWorker(appContext: Context, workerParams: WorkerParameters) :
-    appContext: Context,
+    CoroutineWorker(appContext, workerParams) {
-    workerParams: WorkerParameters
-) : CoroutineWorker(appContext, workerParams) {
   override suspend fun doWork(): Result {
-        val app = UninitializedApp.get()
+    val app = UninitializedApp.get() ?: return Result.failure()
+
     suspend fun runAndGetResult(): String? {
       val exitNodeName = inputData.getString(EXIT_NODE_NAME)
 
-            val exitNodeId = if (exitNodeName.isNullOrEmpty()) {
+      val exitNodeId =
+          if (exitNodeName.isNullOrEmpty()) {
             null
           } else {
-                if (!app.isAbleToStartVPN()) {
+            if (app.isAbleToStartVPN() != true) {
               return app.getString(R.string.vpn_is_not_ready_to_start)
             }
 
             val peers =
                 (Notifier.netmap.value
-                        ?: run { return@runAndGetResult app.getString(R.string.tailscale_is_not_setup) })
+                        ?: run {
-                        .Peers ?: run { return@runAndGetResult app.getString(R.string.no_peers_found) }
+                          return@runAndGetResult app.getString(R.string.tailscale_is_not_setup)
+                        })
+                    .Peers
+                    ?: run {
+                      return@runAndGetResult app.getString(R.string.no_peers_found)
+                    }
 
-                val filteredPeers = peers.filter {
+            val filteredPeers = peers.filter { it.displayName == exitNodeName }.toList()
-                    it.displayName == exitNodeName
-                }.toList()
 
             if (filteredPeers.isEmpty()) {
               return app.getString(R.string.no_peers_with_name_found, exitNodeName)
             } else if (filteredPeers.size > 1) {
               return app.getString(R.string.multiple_peers_with_name_found, exitNodeName)
             } else if (!filteredPeers[0].isExitNode) {
-                    return app.getString(
+              return app.getString(R.string.peer_with_name_is_not_an_exit_node, exitNodeName)
-                        R.string.peer_with_name_is_not_an_exit_node,
-                        exitNodeName
-                    )
             }
 
             filteredPeers[0].StableID
@@ -65,7 +64,8 @@ class UseExitNodeWorker(
       val scope = CoroutineScope(Dispatchers.Default + Job())
       var result: String? = null
       Client(scope).editPrefs(prefsOut) {
-                result = if (it.isFailure) {
+        result =
+            if (it.isFailure) {
               it.exceptionOrNull()?.message
             } else {
               null
@@ -88,7 +88,8 @@ class UseExitNodeWorker(
           PendingIntent.getActivity(
               app, 1, intent, PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE)
 
-            val notification = NotificationCompat.Builder(app, STATUS_CHANNEL_ID)
+      val notification =
+          NotificationCompat.Builder(app, STATUS_CHANNEL_ID)
               .setSmallIcon(R.drawable.ic_notification)
               .setContentTitle(app.getString(R.string.use_exit_node_intent_failed))
               .setContentText(result)

android/src/main/java/com/tailscale/ipn/mdm/MDMSettingsDefinitions.kt

@@ -44,7 +44,7 @@ class AlwaysNeverUserDecidesMDMSetting(key: String, localizedTitle: String) :
   override fun getFrom(bundle: Bundle?, app: App): AlwaysNeverUserDecides {
     val storedString =
         bundle?.getString(key)
-            ?: App.get().getEncryptedPrefs().getString(key, null)
+            ?: App.get()?.getEncryptedPrefs()?.getString(key, null)
             ?: "user-decides"
     return when (storedString) {
       "always" -> {
@@ -64,7 +64,7 @@ class ShowHideMDMSetting(key: String, localizedTitle: String) :
     MDMSetting<ShowHide>(ShowHide.Show, key, localizedTitle) {
   override fun getFrom(bundle: Bundle?, app: App): ShowHide {
     val storedString =
-        bundle?.getString(key) ?: App.get().getEncryptedPrefs().getString(key, null) ?: "show"
+        bundle?.getString(key) ?: App.get()?.getEncryptedPrefs()?.getString(key, null) ?: "show"
     return when (storedString) {
       "hide" -> {
         ShowHide.Hide

android/src/main/java/com/tailscale/ipn/ui/util/AndroidTVUtil.kt

@@ -14,7 +14,11 @@ import com.tailscale.ipn.ui.util.AndroidTVUtil.isAndroidTV
 
 object AndroidTVUtil {
   fun isAndroidTV(): Boolean {
-    val pm = UninitializedApp.get().packageManager
+    // Not ideal, but this is invoked from a Composable, at which point,
+    // we *will* have an Uninitialized app instance.  If this method is being
+    // called extremely early in the app lifecycle, you may get the wrong
+    // answer here.
+    val pm = UninitializedApp.get()?.packageManager ?: return false
     return (pm.hasSystemFeature(PackageManager.FEATURE_TELEVISION) ||
         pm.hasSystemFeature(PackageManager.FEATURE_LEANBACK))
   }

android/src/main/java/com/tailscale/ipn/ui/viewModel/IpnViewModel.kt

@@ -152,11 +152,11 @@ open class IpnViewModel : ViewModel() {
   }
 
   fun startVPN() {
-    UninitializedApp.get().startVPN()
+    UninitializedApp.get()?.startVPN()
   }
 
   fun stopVPN() {
-    UninitializedApp.get().stopVPN()
+    UninitializedApp.get()?.stopVPN()
   }
 
   // Login/Logout