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.spark.network.sasl;
  
  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.AuthorizeCallback;
  import javax.security.sasl.RealmCallback;
  import javax.security.sasl.Sasl;
  import javax.security.sasl.SaslException;
  import javax.security.sasl.SaslServer;
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.util.Map;
  
  import com.google.common.base.Preconditions;
  import com.google.common.base.Throwables;
  import com.google.common.collect.ImmutableMap;
  import io.netty.buffer.Unpooled;
  import io.netty.handler.codec.base64.Base64;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A SASL Server for Spark which simply keeps track of the state of a single SASL session, from the
   * initial state to the "authenticated" state. (It is not a server in the sense of accepting
   * connections on some socket.)
   */
  public class SparkSaslServer implements SaslEncryptionBackend {
    private static final Logger logger = LoggerFactory.getLogger(SparkSaslServer.class);
  
    /**
     * This is passed as the server name when creating the sasl client/server.
     * This could be changed to be configurable in the future.
     */
    static final String DEFAULT_REALM = "default";
  
    /**
     * The authentication mechanism used here is DIGEST-MD5. This could be changed to be
     * configurable in the future.
     */
    static final String DIGEST = "DIGEST-MD5";
  
    /**
     * Quality of protection value that includes encryption.
     */
    static final String QOP_AUTH_CONF = "auth-conf";
  
    /**
     * Quality of protection value that does not include encryption.
     */
    static final String QOP_AUTH = "auth";
  
    /** Identifier for a certain secret key within the secretKeyHolder. */
    private final String secretKeyId;
    private final SecretKeyHolder secretKeyHolder;
    private SaslServer saslServer;
  
    public SparkSaslServer(
        String secretKeyId,
        SecretKeyHolder secretKeyHolder,
        boolean alwaysEncrypt) {
      this.secretKeyId = secretKeyId;
      this.secretKeyHolder = secretKeyHolder;
  
      // Sasl.QOP is a comma-separated list of supported values. The value that allows encryption
      // is listed first since it's preferred over the non-encrypted one (if the client also
      // lists both in the request).
      String qop = alwaysEncrypt ? QOP_AUTH_CONF : String.format("%s,%s", QOP_AUTH_CONF, QOP_AUTH);
      Map<String, String> saslProps = ImmutableMap.<String, String>builder()
        .put(Sasl.SERVER_AUTH, "true")
        .put(Sasl.QOP, qop)
        .build();
      try {
        this.saslServer = Sasl.createSaslServer(DIGEST, null, DEFAULT_REALM, saslProps,
          new DigestCallbackHandler());
      } catch (SaslException e) {
        throw Throwables.propagate(e);
      }
    }
  
    /**
     * Determines whether the authentication exchange has completed successfully.
     */
    public synchronized boolean isComplete() {
      return saslServer != null && saslServer.isComplete();
    }
  
    /** Returns the value of a negotiated property. */
    public Object getNegotiatedProperty(String name) {
      return saslServer.getNegotiatedProperty(name);
    }
  
    /**
     * Used to respond to server SASL tokens.
     * @param token Server's SASL token
     * @return response to send back to the server.
     */
    public synchronized byte[] response(byte[] token) {
      try {
        return saslServer != null ? saslServer.evaluateResponse(token) : new byte[0];
      } catch (SaslException e) {
        throw Throwables.propagate(e);
      }
    }
  
    /**
     * Disposes of any system resources or security-sensitive information the
     * SaslServer might be using.
     */
    @Override
    public synchronized void dispose() {
      if (saslServer != null) {
        try {
          saslServer.dispose();
        } catch (SaslException e) {
          // ignore
        } finally {
          saslServer = null;
        }
      }
    }
  
    @Override
    public byte[] wrap(byte[] data, int offset, int len) throws SaslException {
      return saslServer.wrap(data, offset, len);
    }
  
    @Override
    public byte[] unwrap(byte[] data, int offset, int len) throws SaslException {
      return saslServer.unwrap(data, offset, len);
    }
  
    /**
     * Implementation of javax.security.auth.callback.CallbackHandler for SASL DIGEST-MD5 mechanism.
     */
    private class DigestCallbackHandler implements CallbackHandler {
      @Override
      public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException {
        for (Callback callback : callbacks) {
          if (callback instanceof NameCallback) {
            logger.trace("SASL server callback: setting username");
            NameCallback nc = (NameCallback) callback;
            nc.setName(encodeIdentifier(secretKeyHolder.getSaslUser(secretKeyId)));
          } else if (callback instanceof PasswordCallback) {
            logger.trace("SASL server callback: setting password");
            PasswordCallback pc = (PasswordCallback) callback;
            pc.setPassword(encodePassword(secretKeyHolder.getSecretKey(secretKeyId)));
          } else if (callback instanceof RealmCallback) {
            logger.trace("SASL server callback: setting realm");
            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);
            }
            logger.debug("SASL Authorization complete, authorized set to {}", ac.isAuthorized());
          } else {
            throw new UnsupportedCallbackException(callback, "Unrecognized SASL DIGEST-MD5 Callback");
          }
        }
      }
    }
  
    /* Encode a byte[] identifier as a Base64-encoded string. */
    public static String encodeIdentifier(String identifier) {
      Preconditions.checkNotNull(identifier, "User cannot be null if SASL is enabled");
      return Base64.encode(Unpooled.wrappedBuffer(identifier.getBytes(StandardCharsets.UTF_8)))
        .toString(StandardCharsets.UTF_8);
    }
  
    /** Encode a password as a base64-encoded char[] array. */
    public static char[] encodePassword(String password) {
      Preconditions.checkNotNull(password, "Password cannot be null if SASL is enabled");
      return Base64.encode(Unpooled.wrappedBuffer(password.getBytes(StandardCharsets.UTF_8)))
        .toString(StandardCharsets.UTF_8).toCharArray();
    }
  }
  