/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements. See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.logging.log4j.util;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InvalidObjectException;
  import java.io.ObjectInputStream;
  import java.io.ObjectStreamClass;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.List;
  
  /**
   * Extended ObjectInputStream that only allows certain classes to be deserialized.
   *
   * @since 2.8.2
   */
  public class FilteredObjectInputStream extends ObjectInputStream {
  
      private static final List<String> REQUIRED_JAVA_CLASSES = Arrays.asList(
              "java.math.BigDecimal",
              "java.math.BigInteger",
              // for Message delegate
              "java.rmi.MarshalledObject",
              "[B"
      );
  
      private static final List<String> REQUIRED_JAVA_PACKAGES = Arrays.asList(
              "java.lang.",
              "java.time",
              "java.util.",
              "org.apache.logging.log4j.",
              "[Lorg.apache.logging.log4j."
      );
  
      private final Collection<String> allowedClasses;
  
      public FilteredObjectInputStream() throws IOException, SecurityException {
          super();
          this.allowedClasses = new HashSet<>();
      }
  
      public FilteredObjectInputStream(final InputStream in) throws IOException {
          super(in);
          this.allowedClasses = new HashSet<>();
      }
  
      public FilteredObjectInputStream(final Collection<String> allowedClasses) throws IOException, SecurityException {
          super();
          this.allowedClasses = allowedClasses;
      }
  
      public FilteredObjectInputStream(final InputStream in, final Collection<String> allowedClasses) throws IOException {
          super(in);
          this.allowedClasses = allowedClasses;
      }
  
      public Collection<String> getAllowedClasses() {
          return allowedClasses;
      }
  
      @Override
      protected Class<?> resolveClass(final ObjectStreamClass desc) throws IOException, ClassNotFoundException {
          final String name = desc.getName();
          if (!(isAllowedByDefault(name) || allowedClasses.contains(name))) {
              throw new InvalidObjectException("Class is not allowed for deserialization: " + name);
          }
          return super.resolveClass(desc);
      }
  
      private static boolean isAllowedByDefault(final String name) {
          return isRequiredPackage(name) || REQUIRED_JAVA_CLASSES.contains(name);
      }
  
      private static boolean isRequiredPackage(final String name) {
          for (final String packageName : REQUIRED_JAVA_PACKAGES) {
              if (name.startsWith(packageName)) {
                  return true;
              }
          }
          return false;
      }
  
 }