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 javax.crypto.Mac;
  import javax.crypto.spec.SecretKeySpec;
  import javax.security.sasl.SaslException;
  import java.nio.charset.StandardCharsets;
  import java.security.InvalidKeyException;
  import java.security.NoSuchAlgorithmException;
  
  /**
   * 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 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(StandardCharsets.US_ASCII), HMACMD5);
              Mac mac = Mac.getInstance(HMACMD5);
              mac.init(key);
  
              byte[] bytes = mac.doFinal(challenge);
  
              StringBuilder hash = new StringBuilder(getUsername());
              hash.append(' ');
              for (byte b : bytes) {
                 String hex = Integer.toHexString(0xFF & b);
                 if (hex.length() == 1) {
                    hash.append('0');
                 }
                 hash.append(hex);
              }
  
              sentResponse = true;
              return hash.toString().getBytes(StandardCharsets.US_ASCII);
           } 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.isEmpty() && password != null && !password.isEmpty();
     }
  }
  