/*
* $Id: TokenProcessor.java 471754 2006-11-06 14:55:09Z husted $
*
* 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.struts.util;
import org.apache.struts.Globals;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/**
* TokenProcessor is responsible for handling all token related functionality.
* The methods in this class are synchronized to protect token processing from
* multiple threads. Servlet containers are allowed to return a different
* HttpSession object for two threads accessing the same session so it is not
* possible to synchronize on the session.
*
* @since Struts 1.1
*/
public class TokenProcessor {
/**
* The singleton instance of this class.
*/
private static TokenProcessor instance = new TokenProcessor();
/**
* The timestamp used most recently to generate a token value.
*/
private long previous;
/**
* Protected constructor for TokenProcessor. Use TokenProcessor.getInstance()
* to obtain a reference to the processor.
*/
protected TokenProcessor() {
super();
}
/**
* Retrieves the singleton instance of this class.
*/
public static TokenProcessor getInstance() {
return instance;
}
/**
* <p>Return <code>true</code> if there is a transaction token stored in
* the user's current session, and the value submitted as a request
* parameter with this action matches it. Returns <code>false</code>
* under any of the following circumstances:</p>
*
* <ul>
*
* <li>No session associated with this request</li>
*
* <li>No transaction token saved in the session</li>
*
* <li>No transaction token included as a request parameter</li>
*
* <li>The included transaction token value does not match the transaction
* token in the user's session</li>
*
* </ul>
*
* @param request The servlet request we are processing
*/
public synchronized boolean isTokenValid(HttpServletRequest request) {
return this.isTokenValid(request, false);
}
/**
* Return <code>true</code> if there is a transaction token stored in the
* user's current session, and the value submitted as a request parameter
* with this action matches it. Returns <code>false</code>
*
* <ul>
*
* <li>No session associated with this request</li> <li>No transaction
* token saved in the session</li>
*
* <li>No transaction token included as a request parameter</li>
*
* <li>The included transaction token value does not match the transaction
* token in the user's session</li>
*
* </ul>
*
* @param request The servlet request we are processing
* @param reset Should we reset the token after checking it?
*/
public synchronized boolean isTokenValid(HttpServletRequest request,
boolean reset) {
// Retrieve the current session for this request
HttpSession session = request.getSession(false);
if (session == null) {
return false;
}
// Retrieve the transaction token from this session, and
// reset it if requested
String saved =
(String) session.getAttribute(Globals.TRANSACTION_TOKEN_KEY);
if (saved == null) {
return false;
}
if (reset) {
this.resetToken(request);
}
// Retrieve the transaction token included in this request
String token = request.getParameter(Globals.TOKEN_KEY);
if (token == null) {
return false;
}
return saved.equals(token);
}
/**
* Reset the saved transaction token in the user's session. This
* indicates that transactional token checking will not be needed on the
* next request that is submitted.
*
* @param request The servlet request we are processing
*/
public synchronized void resetToken(HttpServletRequest request) {
HttpSession session = request.getSession(false);
if (session == null) {
return;
}
session.removeAttribute(Globals.TRANSACTION_TOKEN_KEY);
}
/**
* Save a new transaction token in the user's current session, creating a
* new session if necessary.
*
* @param request The servlet request we are processing
*/
public synchronized void saveToken(HttpServletRequest request) {
HttpSession session = request.getSession();
String token = generateToken(request);
if (token != null) {
session.setAttribute(Globals.TRANSACTION_TOKEN_KEY, token);
}
}
/**
* Generate a new transaction token, to be used for enforcing a single
* request for a particular transaction.
*
* @param request The request we are processing
*/
public synchronized String generateToken(HttpServletRequest request) {
HttpSession session = request.getSession();
return generateToken(session.getId());
}
/**
* Generate a new transaction token, to be used for enforcing a single
* request for a particular transaction.
*
* @param id a unique Identifier for the session or other context in which
* this token is to be used.
*/
public synchronized String generateToken(String id) {
try {
long current = System.currentTimeMillis();
if (current == previous) {
current++;
}
previous = current;
byte[] now = new Long(current).toString().getBytes();
MessageDigest md = MessageDigest.getInstance("MD5");
md.update(id.getBytes());
md.update(now);
return toHex(md.digest());
} catch (NoSuchAlgorithmException e) {
return null;
}
}
/**
* Convert a byte array to a String of hexadecimal digits and return it.
*
* @param buffer The byte array to be converted
*/
private String toHex(byte[] buffer) {
StringBuffer sb = new StringBuffer(buffer.length * 2);
for (int i = 0; i < buffer.length; i++) {
sb.append(Character.forDigit((buffer[i] & 0xf0) >> 4, 16));
sb.append(Character.forDigit(buffer[i] & 0x0f, 16));
}
return sb.toString();
}
}