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.kerberos;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * This class implements parsing and handling of Kerberos principal names. In
   * particular, it splits them apart and translates them down into local
   * operating system names.
   */
  public class KerberosShortNamer {
  
      /**
       * A pattern for parsing a auth_to_local rule.
       */
      private static final Pattern RULE_PARSER = Pattern.compile("((DEFAULT)|((RULE:\\[(\\d*):([^\\]]*)](\\(([^)]*)\\))?(s/([^/]*)/([^/]*)/(g)?)?/?(L|U)?)))");
  
      /* Rules for the translation of the principal name into an operating system name */
      private final List<KerberosRule> principalToLocalRules;
  
      public KerberosShortNamer(List<KerberosRule> principalToLocalRules) {
          this.principalToLocalRules = principalToLocalRules;
      }
  
      public static KerberosShortNamer fromUnparsedRules(String defaultRealm, List<String> principalToLocalRules) {
          List<String> rules = principalToLocalRules == null ? Collections.singletonList("DEFAULT") : principalToLocalRules;
          return new KerberosShortNamer(parseRules(defaultRealm, rules));
      }
  
      private static List<KerberosRule> parseRules(String defaultRealm, List<String> rules) {
          List<KerberosRule> result = new ArrayList<>();
          for (String rule : rules) {
              Matcher matcher = RULE_PARSER.matcher(rule);
              if (!matcher.lookingAt()) {
                  throw new IllegalArgumentException("Invalid rule: " + rule);
              }
              if (rule.length() != matcher.end())
                  throw new IllegalArgumentException("Invalid rule: `" + rule + "`, unmatched substring: `" + rule.substring(matcher.end()) + "`");
              if (matcher.group(2) != null) {
                  result.add(new KerberosRule(defaultRealm));
              } else {
                  result.add(new KerberosRule(defaultRealm,
                          Integer.parseInt(matcher.group(5)),
                          matcher.group(6),
                          matcher.group(8),
                          matcher.group(10),
                          matcher.group(11),
                          "g".equals(matcher.group(12)),
                          "L".equals(matcher.group(13)),
                          "U".equals(matcher.group(13))));
  
              }
          }
          return result;
      }
  
      /**
       * Get the translation of the principal name into an operating system
       * user name.
       * @return the short name
       * @throws IOException
       */
      public String shortName(KerberosName kerberosName) throws IOException {
          String[] params;
          if (kerberosName.hostName() == null) {
              // if it is already simple, just return it
              if (kerberosName.realm() == null)
                  return kerberosName.serviceName();
              params = new String[]{kerberosName.realm(), kerberosName.serviceName()};
          } else {
              params = new String[]{kerberosName.realm(), kerberosName.serviceName(), kerberosName.hostName()};
          }
          for (KerberosRule r : principalToLocalRules) {
              String result = r.apply(params);
              if (result != null)
                  return result;
          }
          throw new NoMatchingRule("No rules apply to " + kerberosName + ", rules " + principalToLocalRules);
      }
  
      @Override
      public String toString() {
          return "KerberosShortNamer(principalToLocalRules = " + principalToLocalRules + ")";
      }
  
  }
  