content: /*
   * Copyright (C) 2019 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.locksettings;
  
  import android.os.SystemProperties;
  import android.util.Slog;
  
  import com.android.internal.annotations.VisibleForTesting;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.file.Paths;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Properties;
  import java.util.Set;
  
  /**
   * A class that maintains a mapping of which password slots are used by alternate OS images when
   * dual-booting a device. Currently, slots can either be owned by the host OS or a live GSI.
   * This mapping is stored in /metadata/password_slots/slot_map using Java Properties.
   *
   * If a /metadata partition does not exist, GSIs are not supported, and PasswordSlotManager will
   * simply not persist the slot mapping.
   */
  public class PasswordSlotManager {
      private static final String TAG = "PasswordSlotManager";
  
      private static final String GSI_RUNNING_PROP = "ro.gsid.image_running";
      private static final String SLOT_MAP_DIR = "/metadata/password_slots";
  
      // This maps each used password slot to the OS image that created it. Password slots are
      // integer keys/indices into secure storage. The OS image is recorded as a string. The factory
      // image is "host" and GSIs are "gsi<N>" where N >= 1.
      private Map<Integer, String> mSlotMap;
  
      // Cache the active slots until loadSlotMap() is called.
      private Set<Integer> mActiveSlots;
  
      public PasswordSlotManager() {
      }
  
      @VisibleForTesting
      protected String getSlotMapDir() {
          return SLOT_MAP_DIR;
      }
  
      @VisibleForTesting
      protected int getGsiImageNumber() {
          return SystemProperties.getInt(GSI_RUNNING_PROP, 0);
      }
  
      /**
       * Notify the manager of which slots are definitively in use by the current OS image.
       *
       * @throws RuntimeException
       */
      public void refreshActiveSlots(Set<Integer> activeSlots) throws RuntimeException {
          if (mSlotMap == null) {
              mActiveSlots = new HashSet<Integer>(activeSlots);
              return;
          }
  
          // Update which slots are owned by the current image.
          final HashSet<Integer> slotsToDelete = new HashSet<Integer>();
          for (Map.Entry<Integer, String> entry : mSlotMap.entrySet()) {
              // Delete possibly stale entries for the current image.
              if (entry.getValue().equals(getMode())) {
                  slotsToDelete.add(entry.getKey());
              }
          }
          for (Integer slot : slotsToDelete) {
              mSlotMap.remove(slot);
          }
  
          // Add slots for the current image.
          for (Integer slot : activeSlots) {
              mSlotMap.put(slot, getMode());
          }
  
          saveSlotMap();
      }
  
      /**
       * Mark the given slot as in use by the current OS image.
       *
       * @throws RuntimeException
       */
      public void markSlotInUse(int slot) throws RuntimeException {
          ensureSlotMapLoaded();
          if (mSlotMap.containsKey(slot) && !mSlotMap.get(slot).equals(getMode())) {
              throw new RuntimeException("password slot " + slot + " is not available");
          }
          mSlotMap.put(slot, getMode());
          saveSlotMap();
      }
  
      /**
       * Mark the given slot as no longer in use by the current OS image.
       *
       * @throws RuntimeException
       */
      public void markSlotDeleted(int slot) throws RuntimeException {
          ensureSlotMapLoaded();
          if (mSlotMap.containsKey(slot) && !mSlotMap.get(slot).equals(getMode())) {
              throw new RuntimeException("password slot " + slot + " cannot be deleted");
          }
          mSlotMap.remove(slot);
          saveSlotMap();
      }
  
      /**
       * Return the set of slots used across all OS images.
       *
       * @return Integer set of all used slots.
       */
      public Set<Integer> getUsedSlots() {
          ensureSlotMapLoaded();
          return Collections.unmodifiableSet(mSlotMap.keySet());
      }
  
      private File getSlotMapFile() {
          return Paths.get(getSlotMapDir(), "slot_map").toFile();
      }
  
      private String getMode() {
          int gsiIndex = getGsiImageNumber();
          if (gsiIndex > 0) {
              return "gsi" + gsiIndex;
          }
          return "host";
      }
  
      @VisibleForTesting
      protected Map<Integer, String> loadSlotMap(InputStream stream) throws IOException {
          final HashMap<Integer, String> map = new HashMap<Integer, String>();
          final Properties props = new Properties();
          props.load(stream);
          for (String slotString : props.stringPropertyNames()) {
              final int slot = Integer.parseInt(slotString);
              final String owner = props.getProperty(slotString);
              map.put(slot, owner);
          }
          return map;
      }
  
      private Map<Integer, String> loadSlotMap() {
          // It's okay if the file doesn't exist.
          final File file = getSlotMapFile();
          if (file.exists()) {
              try (FileInputStream stream = new FileInputStream(file)) {
                  return loadSlotMap(stream);
              } catch (Exception e) {
                  Slog.e(TAG, "Could not load slot map file", e);
              }
          }
          return new HashMap<Integer, String>();
      }
  
      private void ensureSlotMapLoaded() {
          if (mSlotMap == null) {
              mSlotMap = loadSlotMap();
              if (mActiveSlots != null) {
                  refreshActiveSlots(mActiveSlots);
                  mActiveSlots = null;
              }
          }
      }
  
      @VisibleForTesting
      protected void saveSlotMap(OutputStream stream) throws IOException {
          if (mSlotMap == null) {
              return;
          }
          final Properties props = new Properties();
          for (Map.Entry<Integer, String> entry : mSlotMap.entrySet()) {
              props.setProperty(entry.getKey().toString(), entry.getValue());
          }
          props.store(stream, "");
      }
  
      private void saveSlotMap() {
          if (mSlotMap == null) {
              return;
          }
          if (!getSlotMapFile().getParentFile().exists()) {
              Slog.w(TAG, "Not saving slot map, " + getSlotMapDir() + " does not exist");
              return;
          }
  
          try (FileOutputStream fos = new FileOutputStream(getSlotMapFile())) {
              saveSlotMap(fos);
          } catch (IOException e) {
              Slog.e(TAG, "failed to save password slot map", e);
          }
      }
  }
  