content: /*
   * 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.kafka.common.security.plain.internals;
  
  import org.apache.kafka.common.KafkaException;
  import org.apache.kafka.common.security.JaasContext;
  import org.apache.kafka.common.security.auth.AuthenticateCallbackHandler;
  import org.apache.kafka.common.security.plain.PlainAuthenticateCallback;
  import org.apache.kafka.common.security.plain.PlainLoginModule;
  import org.apache.kafka.common.utils.Utils;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.Map;
  
  import javax.security.auth.callback.Callback;
  import javax.security.auth.callback.NameCallback;
  import javax.security.auth.callback.UnsupportedCallbackException;
  import javax.security.auth.login.AppConfigurationEntry;
  
  public class PlainServerCallbackHandler implements AuthenticateCallbackHandler {
  
      private static final String JAAS_USER_PREFIX = "user_";
      private List<AppConfigurationEntry> jaasConfigEntries;
  
      @Override
      public void configure(Map<String, ?> configs, String mechanism, List<AppConfigurationEntry> jaasConfigEntries) {
          this.jaasConfigEntries = jaasConfigEntries;
      }
  
      @Override
      public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException {
          String username = null;
          for (Callback callback: callbacks) {
              if (callback instanceof NameCallback)
                  username = ((NameCallback) callback).getDefaultName();
              else if (callback instanceof PlainAuthenticateCallback) {
                  PlainAuthenticateCallback plainCallback = (PlainAuthenticateCallback) callback;
                  boolean authenticated = authenticate(username, plainCallback.password());
                  plainCallback.authenticated(authenticated);
              } else
                  throw new UnsupportedCallbackException(callback);
          }
      }
  
      protected boolean authenticate(String username, char[] password) throws IOException {
          if (username == null)
              return false;
          else {
              String expectedPassword = JaasContext.configEntryOption(jaasConfigEntries,
                      JAAS_USER_PREFIX + username,
                      PlainLoginModule.class.getName());
              return expectedPassword != null && Utils.isEqualConstantTime(password, expectedPassword.toCharArray());
          }
      }
  
      @Override
      public void close() throws KafkaException {
      }
  
  }
  