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.kerberos;
  
  import org.apache.kafka.common.config.SaslConfigs;
  import org.apache.kafka.common.security.auth.AuthenticateCallbackHandler;
  
  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.PasswordCallback;
  import javax.security.auth.callback.UnsupportedCallbackException;
  import javax.security.auth.login.AppConfigurationEntry;
  import javax.security.sasl.AuthorizeCallback;
  import javax.security.sasl.RealmCallback;
  
  /**
   * Callback handler for SASL/GSSAPI clients.
   */
  public class KerberosClientCallbackHandler implements AuthenticateCallbackHandler {
  
      @Override
      public void configure(Map<String, ?> configs, String saslMechanism, List<AppConfigurationEntry> jaasConfigEntries) {
          if (!saslMechanism.equals(SaslConfigs.GSSAPI_MECHANISM))
              throw new IllegalStateException("Kerberos callback handler should only be used with GSSAPI");
      }
  
      @Override
      public void handle(Callback[] callbacks) throws UnsupportedCallbackException {
          for (Callback callback : callbacks) {
              if (callback instanceof NameCallback) {
                  NameCallback nc = (NameCallback) callback;
                  nc.setName(nc.getDefaultName());
              } else if (callback instanceof PasswordCallback) {
                  String errorMessage = "Could not login: the client is being asked for a password, but the Kafka" +
                               " client code does not currently support obtaining a password from the user.";
                  errorMessage += " Make sure -Djava.security.auth.login.config property passed to JVM and" +
                               " the client is configured to use a ticket cache (using" +
                               " the JAAS configuration setting 'useTicketCache=true)'. Make sure you are using" +
                               " FQDN of the Kafka broker you are trying to connect to.";
                  throw new UnsupportedCallbackException(callback, errorMessage);
              } else if (callback instanceof RealmCallback) {
                  RealmCallback rc = (RealmCallback) callback;
                  rc.setText(rc.getDefaultText());
              } else if (callback instanceof AuthorizeCallback) {
                  AuthorizeCallback ac = (AuthorizeCallback) callback;
                  String authId = ac.getAuthenticationID();
                  String authzId = ac.getAuthorizationID();
                  ac.setAuthorized(authId.equals(authzId));
                  if (ac.isAuthorized())
                      ac.setAuthorizedID(authzId);
              }  else {
                  throw new UnsupportedCallbackException(callback, "Unrecognized SASL ClientCallback");
              }
          }
      }
  
      @Override
      public void close() {
      }
  }
  