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.celeborn.common.network.sasl;
  
  import static org.apache.celeborn.common.network.sasl.SaslUtils.*;
  
  import java.util.Map;
  
  import javax.annotation.Nullable;
  import javax.annotation.concurrent.GuardedBy;
  import javax.security.auth.callback.Callback;
  import javax.security.auth.callback.CallbackHandler;
  import javax.security.auth.callback.NameCallback;
  import javax.security.auth.callback.PasswordCallback;
  import javax.security.auth.callback.UnsupportedCallbackException;
  import javax.security.sasl.RealmCallback;
  import javax.security.sasl.RealmChoiceCallback;
  import javax.security.sasl.Sasl;
  import javax.security.sasl.SaslClient;
  import javax.security.sasl.SaslException;
  
  import com.google.common.base.Preconditions;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A SASL Client for Celeborn which simply keeps track of the state of a single SASL session, from
   * the initial state to the "authenticated" state. This client initializes the protocol via a
   * firstToken, which is then followed by a set of challenges and responses.
   *
   * <p>TODO: Currently, we have hardcoded Sasl mechanism to be DIGEST-MD5 for connection auth. We
   * should make this configurable in the future (see:
   * https://issues.apache.org/jira/browse/CELEBORN-1158).
   */
  public class CelebornSaslClient {
    private static final Logger logger = LoggerFactory.getLogger(CelebornSaslClient.class);
  
    @GuardedBy("this")
    private SaslClient saslClient;
  
    public CelebornSaslClient(
        String saslMechanism,
        @Nullable Map<String, String> saslProps,
        @Nullable CallbackHandler authCallbackHandler) {
      Preconditions.checkNotNull(saslMechanism);
      initializeSaslProviders();
      try {
        this.saslClient =
            Sasl.createSaslClient(
                new String[] {saslMechanism},
                null,
                null,
                DEFAULT_REALM,
                saslProps,
                authCallbackHandler);
      } catch (SaslException e) {
        throw new IllegalArgumentException(e);
      }
    }
  
    /** Used to initiate SASL handshake with server. */
    public synchronized byte[] firstToken() {
      if (saslClient != null && saslClient.hasInitialResponse()) {
        try {
          return saslClient.evaluateChallenge(EMPTY_BYTE_ARRAY);
        } catch (SaslException e) {
          throw new IllegalArgumentException(e);
        }
      } else {
        return EMPTY_BYTE_ARRAY;
      }
    }
  
    /** Determines whether the authentication exchange has completed. */
    public synchronized boolean isComplete() {
      return saslClient != null && saslClient.isComplete();
    }
  
    /** Returns the value of a negotiated property. */
    public synchronized Object getNegotiatedProperty(String name) {
      return saslClient.getNegotiatedProperty(name);
    }
  
    /**
     * Respond to server's SASL token.
     *
     * @param token contains server's SASL token
     * @return client's response SASL token
     */
    public synchronized byte[] response(byte[] token) {
      try {
        return saslClient != null ? saslClient.evaluateChallenge(token) : EMPTY_BYTE_ARRAY;
      } catch (SaslException e) {
        throw new RuntimeException(e);
      }
    }
  
    /**
     * Disposes of any system resources or security-sensitive information the SaslClient might be
     * using.
     */
    public synchronized void dispose() {
      if (saslClient != null) {
        try {
          saslClient.dispose();
        } catch (SaslException e) {
          // ignore
        } finally {
          saslClient = null;
        }
      }
    }
  
    /**
     * Implementation of javax.security.auth.callback.CallbackHandler that works with share secrets.
     */
    static class ClientCallbackHandler implements CallbackHandler {
  
      private final String id;
      private final String password;
  
      public ClientCallbackHandler(String id, String password) {
        this.id = Preconditions.checkNotNull(id, "id");
        this.password = Preconditions.checkNotNull(password, "password");
      }
  
      @Override
      public void handle(Callback[] callbacks) throws UnsupportedCallbackException {
  
        for (Callback callback : callbacks) {
          if (callback instanceof NameCallback) {
            logger.trace("SASL client callback: setting username");
            NameCallback nc = (NameCallback) callback;
            nc.setName(encodeIdentifier(id));
          } else if (callback instanceof PasswordCallback) {
            logger.trace("SASL client callback: setting password");
            PasswordCallback pc = (PasswordCallback) callback;
            pc.setPassword(encodePassword(password));
          } else if (callback instanceof RealmCallback) {
            logger.trace("SASL client callback: setting realm");
            RealmCallback rc = (RealmCallback) callback;
            rc.setText(rc.getDefaultText());
          } else if (callback instanceof RealmChoiceCallback) {
            // ignore (?)
          } else {
            throw new UnsupportedCallbackException(callback, "Unrecognized callback: " + callback);
          }
        }
      }
    }
  }
  