content: /*
   * Copyright 2017 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.net.watchlist;
  
  import android.annotation.Nullable;
  import android.util.Log;
  import android.util.proto.ProtoOutputStream;
  
  import com.android.internal.annotations.VisibleForTesting;
  import com.android.internal.util.HexDump;
  import com.android.service.NetworkWatchlistReportProto;
  import com.android.service.NetworkWatchlistAppResultProto;
  
  import java.io.ByteArrayOutputStream;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  
  /**
   * Helper class to encode and generate serialized DP encoded watchlist proto report.
   */
  class ReportEncoder {
  
      private static final String TAG = "ReportEncoder";
  
      // Report version number, as file format / parameters can be changed in later version, we need
      // to have versioning on watchlist report format
      private static final int REPORT_VERSION = 1;
  
      private static final int WATCHLIST_HASH_SIZE = 32;
  
      /**
       * Apply DP on watchlist results, and generate a serialized watchlist report ready to store
       * in DropBox.
       */
      @Nullable
      static byte[] encodeWatchlistReport(WatchlistConfig config, byte[] userSecret,
              List<String> appDigestList, WatchlistReportDbHelper.AggregatedResult aggregatedResult) {
          Map<String, Boolean> resultMap = PrivacyUtils.createDpEncodedReportMap(
                  config.isConfigSecure(), userSecret, appDigestList, aggregatedResult);
          return serializeReport(config, resultMap);
      }
  
      /**
       * Convert DP encoded watchlist report into proto format.
       *
       * @param encodedReportMap DP encoded watchlist report.
       * @return Watchlist report in proto format, which will be shared in Dropbox. Null if
       * watchlist report cannot be generated.
       */
      @Nullable
      @VisibleForTesting
      static byte[] serializeReport(WatchlistConfig config,
              Map<String, Boolean> encodedReportMap) {
          // TODO: Handle watchlist config changed case
          final byte[] watchlistHash = config.getWatchlistConfigHash();
          if (watchlistHash == null) {
              Log.e(TAG, "No watchlist hash");
              return null;
          }
          if (watchlistHash.length != WATCHLIST_HASH_SIZE) {
              Log.e(TAG, "Unexpected hash length");
              return null;
          }
          final ByteArrayOutputStream reportOutputStream = new ByteArrayOutputStream();
          final ProtoOutputStream proto = new ProtoOutputStream(reportOutputStream);
  
          // Set report version to report
          proto.write(NetworkWatchlistReportProto.REPORT_VERSION, REPORT_VERSION);
          proto.write(NetworkWatchlistReportProto.WATCHLIST_CONFIG_HASH,
                  HexDump.toHexString(watchlistHash));
  
          // Set app digest, encoded_isPha pair to report
          for (Map.Entry<String, Boolean> entry : encodedReportMap.entrySet()) {
              String key = entry.getKey();
              byte[] digest = HexDump.hexStringToByteArray(key);
              boolean encodedResult = entry.getValue();
              long token = proto.start(NetworkWatchlistReportProto.APP_RESULT);
              proto.write(NetworkWatchlistAppResultProto.APP_DIGEST, key);
              proto.write(NetworkWatchlistAppResultProto.ENCODED_RESULT, encodedResult);
              proto.end(token);
          }
          proto.flush();
          return reportOutputStream.toByteArray();
      }
  }
  