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/*
 * 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.log4j.net;

import java.io.IOException;
import java.io.InputStream;
import java.io.InvalidClassException;
import java.io.ObjectInputStream;
import java.io.ObjectStreamClass;
import java.util.ArrayList;
import java.util.List;

/**
 * HardenedObjectInputStream restricts the set of classes that can be deserialized to a set of explicitly whitelisted
 * classes. This prevents certain type of attacks from being successful.
 *
 * 
 * It is assumed that classes in the "java.lang" and "java.util" packages are always authorized.
 * 
 *
 * @author Ceki Gülcü
 * @since 1.2.18
 * 
 * === Copied from the logback project with permission ==
 */
public class HardenedObjectInputStream extends ObjectInputStream {

    static final String ARRAY_CLASS_PREFIX = "[L";
    final List whitelistedClassNames;
    final static String[] JAVA_PACKAGES = new String[] { "java.lang", "java.util", ARRAY_CLASS_PREFIX + "java.lang" };

    public HardenedObjectInputStream(InputStream in, String[] whilelist) throws IOException {
        super(in);

        this.whitelistedClassNames = new ArrayList();
        if (whilelist != null) {
            for (int i = 0; i < whilelist.length; i++) {
                this.whitelistedClassNames.add(whilelist[i]);
            }
        }
    }

    public HardenedObjectInputStream(InputStream in, List whitelist) throws IOException {
        super(in);

        this.whitelistedClassNames = new ArrayList();
        this.whitelistedClassNames.addAll(whitelist);
    }

    @Override
    protected Class resolveClass(ObjectStreamClass anObjectStreamClass) throws IOException, ClassNotFoundException {

        String incomingClassName = anObjectStreamClass.getName();

        if (!isWhitelisted(incomingClassName)) {
            throw new InvalidClassException("Unauthorized deserialization attempt", incomingClassName);
        }

        return super.resolveClass(anObjectStreamClass);
    }

    private boolean isWhitelisted(String incomingClassName) {
        for (int i = 0; i < JAVA_PACKAGES.length; i++) {
            if (incomingClassName.startsWith(JAVA_PACKAGES[i]))
                return true;
        }
        for (String whiteListed : whitelistedClassNames) {
            if (incomingClassName.equals(whiteListed))
                return true;
        }
        return false;
    }

    protected void addToWhitelist(List additionalAuthorizedClasses) {
        whitelistedClassNames.addAll(additionalAuthorizedClasses);
    }
}