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.activemq.transport.amqp.client.sasl;
  
  import java.io.UnsupportedEncodingException;
  import java.security.InvalidKeyException;
  import java.security.NoSuchAlgorithmException;
  
  import javax.crypto.Mac;
  import javax.crypto.spec.SecretKeySpec;
  import javax.security.sasl.SaslException;
  
  /**
   * Implements the SASL PLAIN authentication Mechanism.
   *
   * User name and Password values are sent without being encrypted.
   */
  public class CramMD5Mechanism extends AbstractMechanism {
  
      private static final String ASCII = "ASCII";
      private static final String HMACMD5 = "HMACMD5";
      private boolean sentResponse;
  
      @Override
      public int getPriority() {
          return PRIORITY.HIGH.getValue();
      }
  
      @Override
      public String getName() {
          return "CRAM-MD5";
      }
  
      @Override
      public byte[] getInitialResponse() {
          return EMPTY;
      }
  
      @Override
      public byte[] getChallengeResponse(byte[] challenge) throws SaslException {
          if (!sentResponse && challenge != null && challenge.length != 0) {
              try {
                  SecretKeySpec key = new SecretKeySpec(getPassword().getBytes(ASCII), HMACMD5);
                  Mac mac = Mac.getInstance(HMACMD5);
                  mac.init(key);
  
                  byte[] bytes = mac.doFinal(challenge);
  
                  StringBuffer hash = new StringBuffer(getUsername());
                  hash.append(' ');
                  for (int i = 0; i < bytes.length; i++) {
                      String hex = Integer.toHexString(0xFF & bytes[i]);
                      if (hex.length() == 1) {
                          hash.append('0');
                      }
                      hash.append(hex);
                  }
  
                  sentResponse = true;
                  return hash.toString().getBytes(ASCII);
              } catch (UnsupportedEncodingException e) {
                  throw new SaslException("Unable to utilise required encoding", e);
              } catch (InvalidKeyException e) {
                  throw new SaslException("Unable to utilise key", e);
              } catch (NoSuchAlgorithmException e) {
                  throw new SaslException("Unable to utilise required algorithm", e);
              }
          } else {
              return EMPTY;
          }
      }
  
      @Override
      public boolean isApplicable(String username, String password) {
          return username != null && username.length() > 0 && password != null && password.length() > 0;
      }
  }
  