java.security.MessageDigest的使用(2),生成安全令牌!

时候,我们需要产生一个数据,这个数据保存了用户的信息,但加密后仍然有可能被人使用,即便他人不确切的了解详细信息...

好比,我们在上网的时候,很多网页都会有一个信息,是否保存登录信息,以便下次可以直接登录而不必再次输入账户,密码等...而通常这样需要Cookie保存用户信息,当然,这个信息是加密信息,且一般都加了时间戳等验证信息的...

登陆时,读取cookie,解析cookie的信息,以及如时间戳等附加信息.如果没有时间戳...那么任何人只要有这个cookie,复制cookie到他的电脑中,然后登陆相同的页面,即便盗用者并不知道用户的信息是什么,也能登陆...

所以,时间戳就类似我们所说的安全令牌.

方式,将用户信息MD5加密后,再将时间戳MD5加密,然后按照特定的处理,将加密后的用户信息以及时间戳,ip地址等信息再次处理,加密后,生成cookie保存客户端...这样就避免了前面所说的安全问题...

java.security.MessageDigest,在创建安全令牌上,比MD5更简便.因为update方法!!!

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package cn.vicky.utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
* 令牌处理器
*
* @author Vicky
* @emial eclipser@163.com
*
*/
public class TokenProcessor {

private static TokenProcessor instance = new TokenProcessor();

private long previous;

protected TokenProcessor() {
}

public static TokenProcessor getInstance() {
return instance;
}

public synchronized String generateToken(String msg, boolean timeChange) {
try {

long current = System.currentTimeMillis();
if (current == previous) current++;
previous = current;
MessageDigest md = MessageDigest.getInstance("MD5");
md.update(msg.getBytes());
if (timeChange) {
// byte now[] = (current+"").toString().getBytes();
byte now[] = (new Long(current)).toString().getBytes();
md.update(now);
}
return toHex(md.digest());
} catch (NoSuchAlgorithmException e) {
return null;
}
}

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] & 240) >> 4, 16));
sb.append(Character.forDigit(buffer[i] & 15, 16));
}

return sb.toString();
}
}
package cn.vicky.utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
* 令牌处理器
*
* @author Vicky
* @emial eclipser@163.com
*
*/
public class TokenProcessor {

private static TokenProcessor instance = new TokenProcessor();

private long previous;

protected TokenProcessor() {
}

public static TokenProcessor getInstance() {
return instance;
}

public synchronized String generateToken(String msg, boolean timeChange) {
try {

long current = System.currentTimeMillis();
if (current == previous) current++;
previous = current;
MessageDigest md = MessageDigest.getInstance("MD5");
md.update(msg.getBytes());
if (timeChange) {
// byte now[] = (current+"").toString().getBytes();
byte now[] = (new Long(current)).toString().getBytes();
md.update(now);
}
return toHex(md.digest());
} catch (NoSuchAlgorithmException e) {
return null;
}
}

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] & 240) >> 4, 16));
sb.append(Character.forDigit(buffer[i] & 15, 16));
}

return sb.toString();
}
}


测试

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@Test
public void testGenerateToken(){

String token = new TokenProcessor().generateToken("Vicky",true);

System.err.println(token);

String token2 = new TokenProcessor().generateToken("Vicky",false);

System.err.println(token2);
}

@Test
public void testGenerateToken(){

String token = new TokenProcessor().generateToken("Vicky",true);

System.err.println(token);

String token2 = new TokenProcessor().generateToken("Vicky",false);

System.err.println(token2);
}


执行后打印:

69ff8ae72232da59a613ecc830ed7c7a
020c290593cef84aeac4ea2c269d326d

再次执行打印:

d8e38257652deaa76de81c8225801482
020c290593cef84aeac4ea2c269d326d

可见,第1打印的数据,是一直变换的.因为他加入了时间戳

而第2条打印的数据却是不变的,因为他只是简单的MD5加密

这样的安全令牌在很多大型框架中都会涉及,比如说顶顶大名的Struts.这里,我以servlet为实例,向request请求加入安全令牌!

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package cn.vicky.struts.util;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

/**
*
* @author Vicky
* @email eclipser@163.com
*
*/
public class TokenProcessor {

private static TokenProcessor instance = new TokenProcessor();

private long previous;

protected TokenProcessor() {
}

public static TokenProcessor getInstance() {
return instance;
}

public synchronized boolean isTokenValid(HttpServletRequest request) {
return isTokenValid(request, false);
}

public synchronized boolean isTokenValid(HttpServletRequest request,
boolean reset) {

HttpSession session = request.getSession(false);
if (session == null
return false;
String saved = (String) session
.getAttribute("cn.vicky.struts.action.TOKEN");
if (saved == null)
return false;

if (reset)
resetToken(request);
String token = request
.getParameter("cn.vicky.struts.taglib.html.TOKEN");
if (token == null)
return false;
else
return saved.equals(token);
}


public synchronized void resetToken(HttpServletRequest request) {
HttpSession session = request.getSession(false);
if (session == null) {
return;
} else {
session.removeAttribute("cn.vicky.struts.action.TOKEN");
return;
}
}


public synchronized void saveToken(HttpServletRequest request) {
HttpSession session = request.getSession();
String token = generateToken(request);
if (token != null)
session.setAttribute("cn.vicky.struts.action.TOKEN", token);
}


public synchronized String generateToken(HttpServletRequest request) {
HttpSession session = request.getSession();
return generateToken(session.getId());
}


public synchronized String generateToken(String id) {
try {

long current = System.currentTimeMillis();
if (current == previous)
current++;
previous = current;

// byte now[] = (current+"").toString().getBytes();
byte now[] = (new Long(current)).toString().getBytes();
MessageDigest md = MessageDigest.getInstance("MD5");

md.update(id.getBytes());
md.update(now);
System.out.println(md.digest().length);
return toHex(md.digest());
} catch (NoSuchAlgorithmException e) {
return null;
}
}


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] & 240) >> 4, 16));
sb.append(Character.forDigit(buffer[i] & 15, 16));
}

return sb.toString();
}
}



本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/eclipser1987/archive/2010/01/08/5159106.aspx