content: /*
   * Copyright (C) 2012 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.updates;
  
  import com.android.server.EventLogTags;
  import com.android.internal.util.HexDump;
  
  import android.content.BroadcastReceiver;
  import android.content.Context;
  import android.content.Intent;
  import android.net.Uri;
  import android.util.EventLog;
  import android.util.Slog;
  
  import java.io.File;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  
  import libcore.io.IoUtils;
  import libcore.io.Streams;
  
  public class ConfigUpdateInstallReceiver extends BroadcastReceiver {
  
      private static final String TAG = "ConfigUpdateInstallReceiver";
  
      private static final String EXTRA_REQUIRED_HASH = "REQUIRED_HASH";
      private static final String EXTRA_VERSION_NUMBER = "VERSION";
  
      protected final File updateDir;
      protected final File updateContent;
      protected final File updateVersion;
  
      public ConfigUpdateInstallReceiver(String updateDir, String updateContentPath,
                                         String updateMetadataPath, String updateVersionPath) {
          this.updateDir = new File(updateDir);
          this.updateContent = new File(updateDir, updateContentPath);
          File updateMetadataDir = new File(updateDir, updateMetadataPath);
          this.updateVersion = new File(updateMetadataDir, updateVersionPath);
      }
  
      @Override
      public void onReceive(final Context context, final Intent intent) {
          new Thread() {
              @Override
              public void run() {
                  try {
                      // get the content path from the extras
                      byte[] altContent = getAltContent(context, intent);
                      // get the version from the extras
                      int altVersion = getVersionFromIntent(intent);
                      // get the previous value from the extras
                      String altRequiredHash = getRequiredHashFromIntent(intent);
                      // get the version currently being used
                      int currentVersion = getCurrentVersion();
                      // get the hash of the currently used value
                      String currentHash = getCurrentHash(getCurrentContent());
                      if (!verifyVersion(currentVersion, altVersion)) {
                          Slog.i(TAG, "Not installing, new version is <= current version");
                      } else if (!verifyPreviousHash(currentHash, altRequiredHash)) {
                          EventLog.writeEvent(EventLogTags.CONFIG_INSTALL_FAILED,
                                              "Current hash did not match required value");
                      } else {
                          // install the new content
                          Slog.i(TAG, "Found new update, installing...");
                          install(altContent, altVersion);
                          Slog.i(TAG, "Installation successful");
                          postInstall(context, intent);
                      }
                  } catch (Exception e) {
                      Slog.e(TAG, "Could not update content!", e);
                      // keep the error message <= 100 chars
                      String errMsg = e.toString();
                      if (errMsg.length() > 100) {
                          errMsg = errMsg.substring(0, 99);
                      }
                      EventLog.writeEvent(EventLogTags.CONFIG_INSTALL_FAILED, errMsg);
                  }
              }
          }.start();
      }
  
      private Uri getContentFromIntent(Intent i) {
          Uri data = i.getData();
          if (data == null) {
              throw new IllegalStateException("Missing required content path, ignoring.");
          }
          return data;
      }
  
      private int getVersionFromIntent(Intent i) throws NumberFormatException {
          String extraValue = i.getStringExtra(EXTRA_VERSION_NUMBER);
          if (extraValue == null) {
              throw new IllegalStateException("Missing required version number, ignoring.");
          }
          return Integer.parseInt(extraValue.trim());
      }
  
      private String getRequiredHashFromIntent(Intent i) {
          String extraValue = i.getStringExtra(EXTRA_REQUIRED_HASH);
          if (extraValue == null) {
              throw new IllegalStateException("Missing required previous hash, ignoring.");
          }
          return extraValue.trim();
      }
  
      private int getCurrentVersion() throws NumberFormatException {
          try {
              String strVersion = IoUtils.readFileAsString(updateVersion.getCanonicalPath()).trim();
              return Integer.parseInt(strVersion);
          } catch (IOException e) {
              Slog.i(TAG, "Couldn't find current metadata, assuming first update");
              return 0;
          }
      }
  
      private byte[] getAltContent(Context c, Intent i) throws IOException {
          Uri content = getContentFromIntent(i);
          InputStream is = c.getContentResolver().openInputStream(content);
          try {
              return Streams.readFullyNoClose(is);
          } finally {
              is.close();
          }
      }
  
      private byte[] getCurrentContent() {
          try {
              return IoUtils.readFileAsByteArray(updateContent.getCanonicalPath());
          } catch (IOException e) {
              Slog.i(TAG, "Failed to read current content, assuming first update!");
              return null;
          }
      }
  
      private static String getCurrentHash(byte[] content) {
          if (content == null) {
              return "0";
          }
          try {
              MessageDigest dgst = MessageDigest.getInstance("SHA512");
              byte[] fingerprint = dgst.digest(content);
              return HexDump.toHexString(fingerprint, false);
          } catch (NoSuchAlgorithmException e) {
              throw new AssertionError(e);
          }
      }
  
      protected boolean verifyVersion(int current, int alternative) {
          return (current < alternative);
      }
  
      private boolean verifyPreviousHash(String current, String required) {
          // this is an optional value- if the required field is NONE then we ignore it
          if (required.equals("NONE")) {
              return true;
          }
          // otherwise, verify that we match correctly
          return current.equals(required);
      }
  
      protected void writeUpdate(File dir, File file, byte[] content) throws IOException {
          FileOutputStream out = null;
          File tmp = null;
          try {
              // create the parents for the destination file
              File parent = file.getParentFile();
              parent.mkdirs();
              // check that they were created correctly
              if (!parent.exists()) {
                  throw new IOException("Failed to create directory " + parent.getCanonicalPath());
              }
              // create the temporary file
              tmp = File.createTempFile("journal", "", dir);
              // mark tmp -rw-r--r--
              tmp.setReadable(true, false);
              // write to it
              out = new FileOutputStream(tmp);
              out.write(content);
              // sync to disk
              out.getFD().sync();
              // atomic rename
              if (!tmp.renameTo(file)) {
                  throw new IOException("Failed to atomically rename " + file.getCanonicalPath());
              }
          } finally {
              if (tmp != null) {
                  tmp.delete();
              }
              IoUtils.closeQuietly(out);
          }
      }
  
      protected void install(byte[] content, int version) throws IOException {
          writeUpdate(updateDir, updateContent, content);
          writeUpdate(updateDir, updateVersion, Long.toString(version).getBytes());
      }
  
      protected void postInstall(Context context, Intent intent) {
      }
  }
  