/*
    * 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.shiro.realm.activedirectory;
  
  import org.apache.shiro.authc.AuthenticationInfo;
  import org.apache.shiro.authc.AuthenticationToken;
  import org.apache.shiro.authc.SimpleAuthenticationInfo;
  import org.apache.shiro.authc.UsernamePasswordToken;
  import org.apache.shiro.authz.AuthorizationInfo;
  import org.apache.shiro.authz.SimpleAuthorizationInfo;
  import org.apache.shiro.realm.Realm;
  import org.apache.shiro.realm.ldap.AbstractLdapRealm;
  import org.apache.shiro.realm.ldap.LdapContextFactory;
  import org.apache.shiro.realm.ldap.LdapUtils;
  import org.apache.shiro.subject.PrincipalCollection;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.naming.NamingEnumeration;
  import javax.naming.NamingException;
  import javax.naming.directory.Attribute;
  import javax.naming.directory.Attributes;
  import javax.naming.directory.SearchControls;
  import javax.naming.directory.SearchResult;
  import javax.naming.ldap.LdapContext;
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.LinkedHashSet;
  import java.util.Locale;
  import java.util.Map;
  import java.util.Set;
  
  
  /**
   * A {@link Realm} that authenticates with an active directory LDAP
   * server to determine the roles for a particular user.  This implementation
   * queries for the user's groups and then maps the group names to roles using the
   * {@link #groupRolesMap}.
   *
   * @since 0.1
   */
  public class ActiveDirectoryRealm extends AbstractLdapRealm {
  
      /*--------------------------------------------
      |             C O N S T A N T S             |
      ============================================*/
  
      private static final Logger LOGGER = LoggerFactory.getLogger(ActiveDirectoryRealm.class);
  
      private static final String ROLE_NAMES_DELIMETER = ",";
  
      /*--------------------------------------------
      |    I N S T A N C E   V A R I A B L E S    |
      ============================================*/
  
      /**
       * Mapping from fully qualified active directory
       * group names (e.g. CN=Group,OU=Company,DC=MyDomain,DC=local)
       * as returned by the active directory LDAP server to role names.
       */
      private Map<String, String> groupRolesMap;
  
      /*--------------------------------------------
      |         C O N S T R U C T O R S           |
      ============================================*/
  
      public void setGroupRolesMap(Map<String, String> groupRolesMap) {
          this.groupRolesMap = groupRolesMap;
      }
  
      /*--------------------------------------------
      |               M E T H O D S               |
      ============================================*/
  
      /**
       * Builds an {@link AuthenticationInfo} object by querying the active directory LDAP context for the
       * specified username.  This method binds to the LDAP server using the provided username and password -
       * which, if successful, indicates that the password is correct.
       * <p/>
       * This method can be overridden by subclasses to query the LDAP server in a more complex way.
       *
       * @param token              the authentication token provided by the user.
       * @param ldapContextFactory the factory used to build connections to the LDAP server.
      * @return an {@link AuthenticationInfo} instance containing information retrieved from LDAP.
      * @throws NamingException if any LDAP errors occur during the search.
      */
     protected AuthenticationInfo queryForAuthenticationInfo(AuthenticationToken token, LdapContextFactory ldapContextFactory)
             throws NamingException {
 
         UsernamePasswordToken upToken = (UsernamePasswordToken) token;
 
         // Binds using the username and password provided by the user.
         LdapContext ctx = null;
         try {
             ctx = ldapContextFactory.getLdapContext(upToken.getUsername(), String.valueOf(upToken.getPassword()));
         } finally {
             LdapUtils.closeContext(ctx);
         }
 
         return buildAuthenticationInfo(upToken.getUsername(), upToken.getPassword());
     }
 
     protected AuthenticationInfo buildAuthenticationInfo(String username, char[] password) {
         return new SimpleAuthenticationInfo(username, password, getName());
     }
 
 
     /**
      * Builds an {@link org.apache.shiro.authz.AuthorizationInfo} object by querying the active directory LDAP context for the
      * groups that a user is a member of.  The groups are then translated to role names by using the
      * configured {@link #groupRolesMap}.
      * <p/>
      * This implementation expects the <tt>principal</tt> argument to be a String username.
      * <p/>
      * Subclasses can override this method to determine authorization data (roles, permissions, etc.) in a more
      * complex way.  Note that this default implementation does not support permissions, only roles.
      *
      * @param principals         the principal of the Subject whose account is being retrieved.
      * @param ldapContextFactory the factory used to create LDAP connections.
      * @return the AuthorizationInfo for the given Subject principal.
      * @throws NamingException if an error occurs when searching the LDAP server.
      */
     protected AuthorizationInfo queryForAuthorizationInfo(PrincipalCollection principals,
                                                           LdapContextFactory ldapContextFactory) throws NamingException {
 
         String username = (String) getAvailablePrincipal(principals);
 
         // Perform context search
         LdapContext ldapContext = ldapContextFactory.getSystemLdapContext();
 
         Set<String> roleNames;
 
         try {
             roleNames = getRoleNamesForUser(username, ldapContext);
         } finally {
             LdapUtils.closeContext(ldapContext);
         }
 
         return buildAuthorizationInfo(roleNames);
     }
 
     protected AuthorizationInfo buildAuthorizationInfo(Set<String> roleNames) {
         return new SimpleAuthorizationInfo(roleNames);
     }
 
     protected Set<String> getRoleNamesForUser(String username, LdapContext ldapContext) throws NamingException {
         Set<String> roleNames;
         roleNames = new LinkedHashSet<String>();
 
         SearchControls searchControls = new SearchControls();
         searchControls.setSearchScope(SearchControls.SUBTREE_SCOPE);
 
         String userPrincipalName = username;
         if (principalSuffix != null
                 && !userPrincipalName.toLowerCase(Locale.ROOT).endsWith(principalSuffix.toLowerCase(Locale.ROOT))) {
             userPrincipalName += principalSuffix;
         }
 
         Object[] searchArguments = new Object[] {userPrincipalName};
 
         NamingEnumeration answer = ldapContext.search(searchBase, searchFilter, searchArguments, searchControls);
 
         while (answer.hasMoreElements()) {
             SearchResult sr = (SearchResult) answer.next();
 
             if (LOGGER.isDebugEnabled()) {
                 LOGGER.debug("Retrieving group names for user [" + sr.getName() + "]");
             }
 
             Attributes attrs = sr.getAttributes();
 
             if (attrs != null) {
                 NamingEnumeration ae = attrs.getAll();
                 while (ae.hasMore()) {
                     Attribute attr = (Attribute) ae.next();
 
                     if (attr.getID().equals("memberOf")) {
 
                         Collection<String> groupNames = LdapUtils.getAllAttributeValues(attr);
 
                         if (LOGGER.isDebugEnabled()) {
                             LOGGER.debug("Groups found for user [" + username + "]: " + groupNames);
                         }
 
                         Collection<String> rolesForGroups = getRoleNamesForGroups(groupNames);
                         roleNames.addAll(rolesForGroups);
                     }
                 }
             }
         }
         return roleNames;
     }
 
     /**
      * This method is called by the default implementation to translate Active Directory group names
      * to role names.  This implementation uses the {@link #groupRolesMap} to map group names to role names.
      *
      * @param groupNames the group names that apply to the current user.
      * @return a collection of roles that are implied by the given role names.
      */
     protected Collection<String> getRoleNamesForGroups(Collection<String> groupNames) {
         Set<String> roleNames = new HashSet<String>(groupNames.size());
 
         if (groupRolesMap != null) {
             for (String groupName : groupNames) {
                 String strRoleNames = groupRolesMap.get(groupName);
                 if (strRoleNames != null) {
                     for (String roleName : strRoleNames.split(ROLE_NAMES_DELIMETER)) {
 
                         if (LOGGER.isDebugEnabled()) {
                             LOGGER.debug("User is member of group [" + groupName + "] so adding role [" + roleName + "]");
                         }
 
                         roleNames.add(roleName);
 
                     }
                 }
             }
         }
         return roleNames;
     }
 
 }