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.authenticator;
  
  import org.apache.kafka.common.config.SaslConfigs;
  import org.apache.kafka.common.internals.SecurityManagerCompatibility;
  import org.apache.kafka.common.security.auth.AuthenticateCallbackHandler;
  import org.apache.kafka.common.security.auth.SaslExtensions;
  import org.apache.kafka.common.security.auth.SaslExtensionsCallback;
  import org.apache.kafka.common.security.scram.ScramExtensionsCallback;
  import org.apache.kafka.common.security.scram.internals.ScramMechanism;
  
  import java.util.List;
  import java.util.Map;
  
  import javax.security.auth.Subject;
  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;
  
  /**
   * Default callback handler for Sasl clients. The callbacks required for the SASL mechanism
   * configured for the client should be supported by this callback handler. See
   * <a href="https://docs.oracle.com/javase/8/docs/technotes/guides/security/sasl/sasl-refguide.html">Java SASL API</a>
   * for the list of SASL callback handlers required for each SASL mechanism.
   *
   * For adding custom SASL extensions, a {@link SaslExtensions} may be added to the subject's public credentials
   */
  public class SaslClientCallbackHandler implements AuthenticateCallbackHandler {
  
      private String mechanism;
  
      @Override
      public void configure(Map<String, ?> configs, String saslMechanism, List<AppConfigurationEntry> jaasConfigEntries) {
          this.mechanism  = saslMechanism;
      }
  
      @Override
      public void handle(Callback[] callbacks) throws UnsupportedCallbackException {
          Subject subject = SecurityManagerCompatibility.get().current();
          for (Callback callback : callbacks) {
              if (callback instanceof NameCallback) {
                  NameCallback nc = (NameCallback) callback;
                  if (subject != null && !subject.getPublicCredentials(String.class).isEmpty()) {
                      nc.setName(subject.getPublicCredentials(String.class).iterator().next());
                  } else
                      nc.setName(nc.getDefaultName());
              } else if (callback instanceof PasswordCallback) {
                  if (subject != null && !subject.getPrivateCredentials(String.class).isEmpty()) {
                      char[] password = subject.getPrivateCredentials(String.class).iterator().next().toCharArray();
                      ((PasswordCallback) callback).setPassword(password);
                  } else {
                      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.";
                      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 if (callback instanceof ScramExtensionsCallback) {
                  if (ScramMechanism.isScram(mechanism) && subject != null && !subject.getPublicCredentials(Map.class).isEmpty()) {
                      @SuppressWarnings("unchecked")
                      Map<String, String> extensions = (Map<String, String>) subject.getPublicCredentials(Map.class).iterator().next();
                      ((ScramExtensionsCallback) callback).extensions(extensions);
                  }
              } else if (callback instanceof SaslExtensionsCallback) {
                  if (!SaslConfigs.GSSAPI_MECHANISM.equals(mechanism) &&
                          subject != null && !subject.getPublicCredentials(SaslExtensions.class).isEmpty()) {
                      SaslExtensions extensions = subject.getPublicCredentials(SaslExtensions.class).iterator().next();
                      ((SaslExtensionsCallback) callback).extensions(extensions);
                  }
              }  else {
                  throw new UnsupportedCallbackException(callback, "Unrecognized SASL ClientCallback");
              }
          }
      }
  
      @Override
      public void close() {
      }
  }
  