转：Java中用HttpsURLConnection访问Https链接的问题

在web应用交互过程中，有很多场景需要保证通信数据的安全；在前面也有好多篇文章介绍了在Web Service调用过程中用WS-Security来保证接口交互过程的安全性，值得注意的是，该种方式基于的传输协议仍然是Http，采用这种方式可扩 展性和数据交互效率比较高；另外一种实现方式就是用Https，他是在协议层对Http的再次封装，加入了SSL/TLS，采用该协议进行通信的数据全部 都会被加密，由于目前Web开发编程中对此都有了一定程度的封装，所以采用Https对外提供服务，除了证书以外，对编程能力的要求并不高，相对于前者门 槛较低，但是由于对双方通信的所有数据都进行加密，而且交互过程中还有多次握手等，所以效率较低；以下就介绍下在Java中访问Https链接时会出现的 一些问题；

在Java中要访问Https链接时，会用到一个关键类HttpsURLConnection；参见如下实现代码：

// 创建URL对象
URL myURL = new URL("https://www.sun.com");

// 创建HttpsURLConnection对象，并设置其SSLSocketFactory对象
HttpsURLConnection httpsConn = (HttpsURLConnection) myURL
        .openConnection();

// 取得该连接的输入流，以读取响应内容
InputStreamReader insr = new InputStreamReader(httpsConn
        .getInputStream());

// 读取服务器的响应内容并显示
int respInt = insr.read();
while (respInt != -1) {
    System.out.print((char) respInt);
    respInt = insr.read();
}

           // 创建URL对象
           URL myURL = new URL("https://www.sun.com");

           // 创建HttpsURLConnection对象，并设置其SSLSocketFactory对象
           HttpsURLConnection httpsConn = (HttpsURLConnection) myURL
                   .openConnection();

           // 取得该连接的输入流，以读取响应内容
           InputStreamReader insr = new InputStreamReader(httpsConn
                   .getInputStream());

           // 读取服务器的响应内容并显示
           int respInt = insr.read();
           while (respInt != -1) {
               System.out.print((char) respInt);
               respInt = insr.read();
           }

在取得connection的时候和正常浏览器访问一样，仍然会验证服务端的证书是否被信任（权威机构发行或者被权威机构签名）；如果服务端证书不被信任，则默认的实现就会有问题，一般来说，用SunJSSE会抛如下异常信息：
javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

上面提到SunJSSE，JSSE（Java Secure Socket Extension）是实现Internet安全通信的一系列包的集合。它是一个SSL和TLS的纯Java实现，可以透明地提供数据加密、服务器认证、 信息完整性等功能，可以使我们像使用普通的套接字一样使用JSSE建立的安全套接字。JSSE是一个开放的标准，不只是Sun公司才能实现一个 SunJSSE，事实上其他公司有自己实现的JSSE，然后通过JCA就可以在JVM中使用。
关于JSSE的详细信息参考官网Reference：http://java.sun.com/j2se/1.5.0/docs/guide/security/jsse/JSSERefGuide.html；
以及Java Security Guide：http://java.sun.com/j2se/1.5.0/docs/guide/security/；

在深入了解JSSE之前，需要了解一个有关Java安全的概念：客户端的TrustStore文件。客户端的TrustStore文件中保存着被客 户端所信任的服务器的证书信息。客户端在进行SSL连接时，JSSE将根据这个文件中的证书决定是否信任服务器端的证书。在SunJSSE中，有一个信任 管理器类负责决定是否信任远端的证书，这个类有如下的处理规则：
1、若系统属性javax.net.sll.trustStore指定了TrustStore文件，那么信任管理器就去jre安装路径下的lib/security/目录中寻找并使用这个文件来检查证书。
2、若该系统属性没有指定TrustStore文件，它就会去jre安装路径下寻找默认的TrustStore文件，这个文件的相对路径为：lib/security/jssecacerts。
3、若jssecacerts不存在，但是cacerts存在（它随J2SDK一起发行，含有数量有限的可信任的基本证书），那么这个默认的TrustStore文件就是lib/security/cacerts。

那遇到这种情况，怎么处理呢？有以下两种方案：
1、按照以上信任管理器的规则，将服务端的公钥导入到jssecacerts，或者是在系统属性中设置要加载的trustStore文件的路径；证书导入可以用如下命令：keytool -import -file src_cer_file –keystore dest_cer_store；至于证书可以通过浏览器导出获得；
2、实现自己的证书信任管理器类，比如MyX509TrustManager，该类必须实现X509TrustManager接口中的三个method；然后在HttpsURLConnection中加载自定义的类，可以参见如下两个代码片段，其一为自定义证书信任管理器，其二为connect时的代码：

   package test;

   import java.io.FileInputStream;
   import java.security.KeyStore;
   import java.security.cert.CertificateException;
   import java.security.cert.X509Certificate;

   import javax.net.ssl.TrustManager;
   import javax.net.ssl.TrustManagerFactory;
   import javax.net.ssl.X509TrustManager;

   public class MyX509TrustManager implements X509TrustManager {

       /*
        * The default X509TrustManager returned by SunX509. We'll delegate
        * decisions to it, and fall back to the logic in this class if the
        * default X509TrustManager doesn't trust it.
        */
       X509TrustManager sunJSSEX509TrustManager;

       MyX509TrustManager() throws Exception {
           // create a "default" JSSE X509TrustManager.

           KeyStore ks = KeyStore.getInstance("JKS");
           ks.load(new FileInputStream("trustedCerts"),
               "passphrase".toCharArray());

           TrustManagerFactory tmf =
           TrustManagerFactory.getInstance("SunX509", "SunJSSE");

            tmf.init(ks);

         TrustManager tms [] = tmf.getTrustManagers();

         /*
          * Iterate over the returned trustmanagers, look
          * for an instance of X509TrustManager. If found,
          * use that as our "default" trust manager.
          */
         for (int i = 0; i < tms.length; i++) {
             if (tms[i] instanceof X509TrustManager) {
                 sunJSSEX509TrustManager = (X509TrustManager) tms[i];
                 return;
             }
         }

         /*
          * Find some other way to initialize, or else we have to fail the
          * constructor.
          */
         throw new Exception("Couldn't initialize");
     }

     /*
      * Delegate to the default trust manager.
      */
     public void checkClientTrusted(X509Certificate[] chain, String authType)
                 throws CertificateException {
         try {
             sunJSSEX509TrustManager.checkClientTrusted(chain, authType);
         } catch (CertificateException excep) {
             // do any special handling here, or rethrow exception.
         }
     }

     /*
      * Delegate to the default trust manager.
      */
     public void checkServerTrusted(X509Certificate[] chain, String authType)
                 throws CertificateException {
         try {
             sunJSSEX509TrustManager.checkServerTrusted(chain, authType);
         } catch (CertificateException excep) {
             /*
              * Possibly pop up a dialog box asking whether to trust the
              * cert chain.
              */
         }
     }

     /*
      * Merely pass this through.
      */
     public X509Certificate[] getAcceptedIssuers() {
         return sunJSSEX509TrustManager.getAcceptedIssuers();
     }
}

          // 创建SSLContext对象，并使用我们指定的信任管理器初始化
         TrustManager[] tm = { new MyX509TrustManager() };
         SSLContext sslContext = SSLContext.getInstance("SSL", "SunJSSE");

         sslContext.init(null, tm, new java.security.SecureRandom());

         // 从上述SSLContext对象中得到SSLSocketFactory对象
         SSLSocketFactory ssf = sslContext.getSocketFactory();

         // 创建URL对象
         URL myURL = new URL("https://ebanks.gdb.com.cn/sperbank/perbankLogin.jsp");

         // 创建HttpsURLConnection对象，并设置其SSLSocketFactory对象
         HttpsURLConnection httpsConn = (HttpsURLConnection) myURL.openConnection();
         httpsConn.setSSLSocketFactory(ssf);

         // 取得该连接的输入流，以读取响应内容
         InputStreamReader insr = new InputStreamReader(httpsConn.getInputStream());

         // 读取服务器的响应内容并显示
         int respInt = insr.read();
         while (respInt != -1) {
             System.out.print((char) respInt);
             respInt = insr.read();
         }

   package test;

   import java.io.FileInputStream;
   import java.security.KeyStore;
   import java.security.cert.CertificateException;
   import java.security.cert.X509Certificate;

   import javax.net.ssl.TrustManager;
   import javax.net.ssl.TrustManagerFactory;
   import javax.net.ssl.X509TrustManager;

   public class MyX509TrustManager implements X509TrustManager {

       /*
        * The default X509TrustManager returned by SunX509. We'll delegate
        * decisions to it, and fall back to the logic in this class if the
        * default X509TrustManager doesn't trust it.
        */
       X509TrustManager sunJSSEX509TrustManager;

       MyX509TrustManager() throws Exception {
           // create a "default" JSSE X509TrustManager.

           KeyStore ks = KeyStore.getInstance("JKS");
           ks.load(new FileInputStream("trustedCerts"),
               "passphrase".toCharArray());

           TrustManagerFactory tmf =
           TrustManagerFactory.getInstance("SunX509", "SunJSSE");

            tmf.init(ks);

         TrustManager tms [] = tmf.getTrustManagers();

         /*
          * Iterate over the returned trustmanagers, look
          * for an instance of X509TrustManager. If found,
          * use that as our "default" trust manager.
          */
         for (int i = 0; i < tms.length; i++) {
             if (tms[i] instanceof X509TrustManager) {
                 sunJSSEX509TrustManager = (X509TrustManager) tms[i];
                 return;
             }
         }

         /*
          * Find some other way to initialize, or else we have to fail the
          * constructor.
          */
         throw new Exception("Couldn't initialize");
     }

     /*
      * Delegate to the default trust manager.
      */
     public void checkClientTrusted(X509Certificate[] chain, String authType)
                 throws CertificateException {
         try {
             sunJSSEX509TrustManager.checkClientTrusted(chain, authType);
         } catch (CertificateException excep) {
             // do any special handling here, or rethrow exception.
         }
     }

     /*
      * Delegate to the default trust manager.
      */
     public void checkServerTrusted(X509Certificate[] chain, String authType)
                 throws CertificateException {
         try {
             sunJSSEX509TrustManager.checkServerTrusted(chain, authType);
         } catch (CertificateException excep) {
             /*
              * Possibly pop up a dialog box asking whether to trust the
              * cert chain.
              */
         }
     }

     /*
      * Merely pass this through.
      */
     public X509Certificate[] getAcceptedIssuers() {
         return sunJSSEX509TrustManager.getAcceptedIssuers();
     }
}

          // 创建SSLContext对象，并使用我们指定的信任管理器初始化
         TrustManager[] tm = { new MyX509TrustManager() };
         SSLContext sslContext = SSLContext.getInstance("SSL", "SunJSSE");

         sslContext.init(null, tm, new java.security.SecureRandom());

         // 从上述SSLContext对象中得到SSLSocketFactory对象
         SSLSocketFactory ssf = sslContext.getSocketFactory();

         // 创建URL对象
         URL myURL = new URL("https://ebanks.gdb.com.cn/sperbank/perbankLogin.jsp");

         // 创建HttpsURLConnection对象，并设置其SSLSocketFactory对象
         HttpsURLConnection httpsConn = (HttpsURLConnection) myURL.openConnection();
         httpsConn.setSSLSocketFactory(ssf);

         // 取得该连接的输入流，以读取响应内容
         InputStreamReader insr = new InputStreamReader(httpsConn.getInputStream());

         // 读取服务器的响应内容并显示
         int respInt = insr.read();
         while (respInt != -1) {
             System.out.print((char) respInt);
             respInt = insr.read();
         }

对于以上两种实现方式，各有各的优点，第一种方式不会破坏JSSE的安全性，但是要手工导入证书，如果服务器很多，那每台服务器的JRE都必须做相同的操作；第二种方式灵活性更高，但是要小心实现，否则可能会留下安全隐患；

转自：http://hi.baidu.com/wzbg/blog/item/258a59cb81da5c13be09e68e.html