content: /*
   * Copyright (C) 2018 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 static android.content.pm.PackageManager.PERMISSION_GRANTED;
  
  import android.content.Context;
  import android.hardware.ISensorPrivacyListener;
  import android.hardware.ISensorPrivacyManager;
  import android.os.Environment;
  import android.os.Handler;
  import android.os.IBinder;
  import android.os.Looper;
  import android.os.RemoteCallbackList;
  import android.os.RemoteException;
  import android.util.ArrayMap;
  import android.util.AtomicFile;
  import android.util.Log;
  import android.util.Xml;
  
  import com.android.internal.annotations.GuardedBy;
  import com.android.internal.util.FastXmlSerializer;
  import com.android.internal.util.XmlUtils;
  import com.android.internal.util.function.pooled.PooledLambda;
  
  import org.xmlpull.v1.XmlPullParser;
  import org.xmlpull.v1.XmlPullParserException;
  import org.xmlpull.v1.XmlSerializer;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.util.NoSuchElementException;
  
  /** @hide */
  public final class SensorPrivacyService extends SystemService {
  
      private static final String TAG = "SensorPrivacyService";
  
      private static final String SENSOR_PRIVACY_XML_FILE = "sensor_privacy.xml";
      private static final String XML_TAG_SENSOR_PRIVACY = "sensor-privacy";
      private static final String XML_ATTRIBUTE_ENABLED = "enabled";
  
      private final SensorPrivacyServiceImpl mSensorPrivacyServiceImpl;
  
      public SensorPrivacyService(Context context) {
          super(context);
          mSensorPrivacyServiceImpl = new SensorPrivacyServiceImpl(context);
      }
  
      @Override
      public void onStart() {
          publishBinderService(Context.SENSOR_PRIVACY_SERVICE, mSensorPrivacyServiceImpl);
      }
  
      class SensorPrivacyServiceImpl extends ISensorPrivacyManager.Stub {
  
          private final SensorPrivacyHandler mHandler;
          private final Context mContext;
          private final Object mLock = new Object();
          @GuardedBy("mLock")
          private final AtomicFile mAtomicFile;
          @GuardedBy("mLock")
          private boolean mEnabled;
  
          SensorPrivacyServiceImpl(Context context) {
              mContext = context;
              mHandler = new SensorPrivacyHandler(FgThread.get().getLooper(), mContext);
              File sensorPrivacyFile = new File(Environment.getDataSystemDirectory(),
                      SENSOR_PRIVACY_XML_FILE);
              mAtomicFile = new AtomicFile(sensorPrivacyFile);
              synchronized (mLock) {
                  mEnabled = readPersistedSensorPrivacyEnabledLocked();
              }
          }
  
          /**
           * Sets the sensor privacy to the provided state and notifies all listeners of the new
           * state.
           */
          @Override
          public void setSensorPrivacy(boolean enable) {
              enforceSensorPrivacyPermission();
              synchronized (mLock) {
                  mEnabled = enable;
                  FileOutputStream outputStream = null;
                  try {
                      XmlSerializer serializer = new FastXmlSerializer();
                      outputStream = mAtomicFile.startWrite();
                      serializer.setOutput(outputStream, StandardCharsets.UTF_8.name());
                      serializer.startDocument(null, true);
                      serializer.startTag(null, XML_TAG_SENSOR_PRIVACY);
                      serializer.attribute(null, XML_ATTRIBUTE_ENABLED, String.valueOf(enable));
                      serializer.endTag(null, XML_TAG_SENSOR_PRIVACY);
                      serializer.endDocument();
                      mAtomicFile.finishWrite(outputStream);
                  } catch (IOException e) {
                      Log.e(TAG, "Caught an exception persisting the sensor privacy state: ", e);
                      mAtomicFile.failWrite(outputStream);
                  }
              }
              mHandler.onSensorPrivacyChanged(enable);
          }
  
          /**
           * Enforces the caller contains the necessary permission to change the state of sensor
           * privacy.
           */
          private void enforceSensorPrivacyPermission() {
              if (mContext.checkCallingOrSelfPermission(
                      android.Manifest.permission.MANAGE_SENSOR_PRIVACY) == PERMISSION_GRANTED) {
                  return;
              }
              throw new SecurityException(
                      "Changing sensor privacy requires the following permission: "
                              + android.Manifest.permission.MANAGE_SENSOR_PRIVACY);
          }
  
          /**
           * Returns whether sensor privacy is enabled.
           */
          @Override
          public boolean isSensorPrivacyEnabled() {
              synchronized (mLock) {
                  return mEnabled;
              }
          }
  
          /**
           * Returns the state of sensor privacy from persistent storage.
           */
          private boolean readPersistedSensorPrivacyEnabledLocked() {
              // if the file does not exist then sensor privacy has not yet been enabled on
              // the device.
              if (!mAtomicFile.exists()) {
                  return false;
              }
              boolean enabled;
              try (FileInputStream inputStream = mAtomicFile.openRead()) {
                  XmlPullParser parser = Xml.newPullParser();
                  parser.setInput(inputStream, StandardCharsets.UTF_8.name());
                  XmlUtils.beginDocument(parser, XML_TAG_SENSOR_PRIVACY);
                  parser.next();
                  String tagName = parser.getName();
                  enabled = Boolean.valueOf(parser.getAttributeValue(null, XML_ATTRIBUTE_ENABLED));
              } catch (IOException | XmlPullParserException e) {
                  Log.e(TAG, "Caught an exception reading the state from storage: ", e);
                  // Delete the file to prevent the same error on subsequent calls and assume sensor
                  // privacy is not enabled.
                  mAtomicFile.delete();
                  enabled = false;
              }
              return enabled;
          }
  
          /**
           * Persists the state of sensor privacy.
           */
          private void persistSensorPrivacyState() {
              synchronized (mLock) {
                  FileOutputStream outputStream = null;
                  try {
                      XmlSerializer serializer = new FastXmlSerializer();
                      outputStream = mAtomicFile.startWrite();
                      serializer.setOutput(outputStream, StandardCharsets.UTF_8.name());
                      serializer.startDocument(null, true);
                      serializer.startTag(null, XML_TAG_SENSOR_PRIVACY);
                      serializer.attribute(null, XML_ATTRIBUTE_ENABLED, String.valueOf(mEnabled));
                      serializer.endTag(null, XML_TAG_SENSOR_PRIVACY);
                      serializer.endDocument();
                      mAtomicFile.finishWrite(outputStream);
                  } catch (IOException e) {
                      Log.e(TAG, "Caught an exception persisting the sensor privacy state: ", e);
                      mAtomicFile.failWrite(outputStream);
                  }
              }
          }
  
          /**
           * Registers a listener to be notified when the sensor privacy state changes.
           */
          @Override
          public void addSensorPrivacyListener(ISensorPrivacyListener listener) {
              if (listener == null) {
                  throw new NullPointerException("listener cannot be null");
              }
              mHandler.addListener(listener);
          }
  
          /**
           * Unregisters a listener from sensor privacy state change notifications.
           */
          @Override
          public void removeSensorPrivacyListener(ISensorPrivacyListener listener) {
              if (listener == null) {
                  throw new NullPointerException("listener cannot be null");
              }
              mHandler.removeListener(listener);
          }
      }
  
      /**
       * Handles sensor privacy state changes and notifying listeners of the change.
       */
      private final class SensorPrivacyHandler extends Handler {
          private static final int MESSAGE_SENSOR_PRIVACY_CHANGED = 1;
  
          private final Object mListenerLock = new Object();
  
          @GuardedBy("mListenerLock")
          private final RemoteCallbackList<ISensorPrivacyListener> mListeners =
                  new RemoteCallbackList<>();
          private final ArrayMap<ISensorPrivacyListener, DeathRecipient> mDeathRecipients;
          private final Context mContext;
  
          SensorPrivacyHandler(Looper looper, Context context) {
              super(looper);
              mDeathRecipients = new ArrayMap<>();
              mContext = context;
          }
  
          public void onSensorPrivacyChanged(boolean enabled) {
              sendMessage(PooledLambda.obtainMessage(SensorPrivacyHandler::handleSensorPrivacyChanged,
                      this, enabled));
              sendMessage(
                      PooledLambda.obtainMessage(SensorPrivacyServiceImpl::persistSensorPrivacyState,
                              mSensorPrivacyServiceImpl));
          }
  
          public void addListener(ISensorPrivacyListener listener) {
              synchronized (mListenerLock) {
                  DeathRecipient deathRecipient = new DeathRecipient(listener);
                  mDeathRecipients.put(listener, deathRecipient);
                  mListeners.register(listener);
              }
          }
  
          public void removeListener(ISensorPrivacyListener listener) {
              synchronized (mListenerLock) {
                  DeathRecipient deathRecipient = mDeathRecipients.remove(listener);
                  if (deathRecipient != null) {
                      deathRecipient.destroy();
                  }
                  mListeners.unregister(listener);
              }
          }
  
          public void handleSensorPrivacyChanged(boolean enabled) {
              final int count = mListeners.beginBroadcast();
              for (int i = 0; i < count; i++) {
                  ISensorPrivacyListener listener = mListeners.getBroadcastItem(i);
                  try {
                      listener.onSensorPrivacyChanged(enabled);
                  } catch (RemoteException e) {
                      Log.e(TAG, "Caught an exception notifying listener " + listener + ": ", e);
                  }
              }
              mListeners.finishBroadcast();
          }
      }
  
      private final class DeathRecipient implements IBinder.DeathRecipient {
  
          private ISensorPrivacyListener mListener;
  
          DeathRecipient(ISensorPrivacyListener listener) {
              mListener = listener;
              try {
                  mListener.asBinder().linkToDeath(this, 0);
              } catch (RemoteException e) {
              }
          }
  
          @Override
          public void binderDied() {
              mSensorPrivacyServiceImpl.removeSensorPrivacyListener(mListener);
          }
  
          public void destroy() {
              try {
                  mListener.asBinder().unlinkToDeath(this, 0);
              } catch (NoSuchElementException e) {
              }
          }
      }
  }
  