/*
    * DavMail POP/IMAP/SMTP/CalDav/LDAP Exchange Gateway
    * Copyright (C) 2012  Mickael Guessant
    *
    * This program is free software; you can redistribute it and/or
    * modify it under the terms of the GNU General Public License
    * as published by the Free Software Foundation; either version 2
    * of the License, or (at your option) any later version.
    *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
   */
  package davmail.http;
  
  import davmail.Settings;
  import org.apache.log4j.Logger;
  
  import javax.security.auth.login.AppConfigurationEntry;
  import javax.security.auth.login.Configuration;
  import java.util.HashMap;
  
  /**
   * Custom JAAS login configuration.
   * Equivalent to the following configuration:
   * spnego-client {
   * com.sun.security.auth.module.Krb5LoginModule required useTicketCache=true renewTGT=true;
   * };
   * spnego-server {
   * com.sun.security.auth.module.Krb5LoginModule required isInitiator=false useKeyTab=false storeKey=true;
   * };
   * <p/>
   */
  public class KerberosLoginConfiguration extends Configuration {
      protected static final Logger LOGGER = Logger.getLogger(KerberosLoginConfiguration.class);
      protected static final AppConfigurationEntry[] CLIENT_LOGIN_MODULE;
      protected static final AppConfigurationEntry[] SERVER_LOGIN_MODULE;
  
      static {
          HashMap<String, String> clientLoginModuleOptions = new HashMap<>();
          if (LOGGER.isDebugEnabled()) {
              clientLoginModuleOptions.put("debug", "true");
          }
  
          clientLoginModuleOptions.put("useTicketCache", "true");
          clientLoginModuleOptions.put("renewTGT", "true");
  
          String krb5ccName = System.getenv().get("KRB5CCNAME");
          if (krb5ccName != null && !krb5ccName.isEmpty()) {
              clientLoginModuleOptions.put("ticketCache", krb5ccName);
          } else if (Settings.isLinux()) {
              LOGGER.warn("KRB5CCNAME environment variable not set, this may cause Kerberos authentication to fail if default_ccache_name is set to KEYRING");
          }
  
          CLIENT_LOGIN_MODULE = new AppConfigurationEntry[]{new AppConfigurationEntry(
                  "com.sun.security.auth.module.Krb5LoginModule",
                  AppConfigurationEntry.LoginModuleControlFlag.REQUIRED,
                  clientLoginModuleOptions)};
  
          HashMap<String, String> serverLoginModuleOptions = new HashMap<>();
          if (LOGGER.isDebugEnabled()) {
              serverLoginModuleOptions.put("debug", "true");
          }
  
          serverLoginModuleOptions.put("isInitiator", "false"); // acceptor (server) mode
          serverLoginModuleOptions.put("useKeyTab", "false"); // do not use credentials stored in keytab file
          serverLoginModuleOptions.put("storeKey", "true"); // store credentials in subject
          SERVER_LOGIN_MODULE = new AppConfigurationEntry[]{new AppConfigurationEntry(
                  "com.sun.security.auth.module.Krb5LoginModule",
                  AppConfigurationEntry.LoginModuleControlFlag.REQUIRED,
                  serverLoginModuleOptions)};
      }
  
      @Override
      public AppConfigurationEntry[] getAppConfigurationEntry(String name) {
          if ("spnego-client".equals(name)) {
              return CLIENT_LOGIN_MODULE;
          } else if ("spnego-server".equals(name)) {
              return SERVER_LOGIN_MODULE;
          } else {
              return null;
          }
      }
  
      @Override
      public void refresh() {
          // nothing to do
      }
  }