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Java语言里用HttpsURLConnection访问Https链接的相关疑难问题

编程语言 zhangyunpengchang 29℃ 0评论

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();
        }

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();
        }



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;







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