下载https站点证书并导入本地jre证书库

在使用java的api请求https地址时，可能会报下面这个错误：

• 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
  或者：

• Exception in thread “main” 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

  原因：客户端找不到服务端的证书(无法验证服务端的安全性)。
  解决方法：
• 忽略证书信任问题
  or
• 从目标网站获得、或者请其提供有效证书

java安全相关的知识简述

　　JSSE是一个SSL和TLS的纯Java实现，通过JSSE可以很容易地编程实现对HTTPS站点的访问。但是，如果该站点的证书未经权威机构的验证，JSSE将拒绝信任该证书从而不能访问HTTPS站点。
　　JSSE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：
　　⑴ 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校验证书。
　　⑵ 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。
　　⑶ 若 jssecacerts不存在，则找cacerts文件(随JDK一起发行，含有数量有限的可信任的基本证书)，此时TrustStore文件就是cacerts。

方法 1）忽略安全认证

Java提供了一种非常简洁的方法来访问HTTPS网页，即使用类HttpsURLConnection、URL等。这几个类为支持HTTPS对JSSE相关类做了进一步的封装，例子如下：

• test1方法直接去访问https://mf.joobank.com报错，原因是找不到有效的证书路径
• test2方法忽略安全认证就不会报错

import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.URL;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;

/**
 * @author Evan
 */
public class Test {
    public static void main(String[] args) throws Exception {
        test1();
        //test2();
    }

    private static void test2() throws NoSuchAlgorithmException, NoSuchProviderException, KeyManagementException, IOException {
        URL reqURL = new URL("https://mf.joobank.com/");
        //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HttpsURLConnection对象，并设置其SSLSocketFactory对象
        HttpsURLConnection httpsConn = (HttpsURLConnection) reqURL.openConnection();
        httpsConn.setSSLSocketFactory(ssf);
        //向服务端发送数据
        httpsConn.setDoOutput(true);
        httpsConn.setRequestMethod("POST");
        OutputStreamWriter out = new OutputStreamWriter(httpsConn.getOutputStream(), "utf-8");
        out.write("java");
        out.flush();
        out.close();

        //读取响应内容
        InputStreamReader in = new InputStreamReader(httpsConn.getInputStream());
        int respInt = in.read();
        while (respInt != -1) {
            System.out.print((char) respInt);
            respInt = in.read();
        }
    }

    private static void test1() throws IOException {
        URL reqURL = new URL("https://mf.joobank.com/");
        HttpsURLConnection httpsConn = (HttpsURLConnection) reqURL.openConnection();

        //向服务端发送数据
        httpsConn.setDoOutput(true);
        httpsConn.setRequestMethod("POST");
        OutputStreamWriter out = new OutputStreamWriter(httpsConn.getOutputStream(), "utf-8");
        out.write("java");
        out.flush();
        out.close();

        //读取响应内容
        InputStreamReader in = new InputStreamReader(httpsConn.getInputStream());
        int respInt = in.read();
        while (respInt != -1) {
            System.out.print((char) respInt);
            respInt = in.read();
        }
    }
}

import javax.net.ssl.X509TrustManager;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

public class MyX509TrustManager implements X509TrustManager {
    @Override
    public void checkClientTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
       //不需要对客户端进行认证，因此我们只需要执行默认的信任管理器的这个方法
    }

    @Override
    public void checkServerTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
       //简单不做任何处理，即一个空的函数体，由于不会抛出异常，它就会信任任何证书。
    }

    @Override
    public X509Certificate[] getAcceptedIssuers() {
        //返回受信任的X509证书数组。
        return new X509Certificate[0];
    }
}

除了忽略证书校验也可以将服务端证书添加到本地JRE证书库解决报错~

方法 2）导入证书：

• 导入证书方法1）通过浏览器打开目标网站，下载证书
  点击安全-有效-详细信息-复制到文件，保存格式选择第一种即可
  
  
  
  证书下载到本地后要使用jdk的keytool工具导入JRE证书库，重启java应用生效：

• 查看当前证书库
  keytool -list -keystore D:\software\java\jdk8\jdk1.8.0_71\jre\lib\security\cacerts -storepass changeit

• 导入证书到当前证书库
  keytool -import -trustcacerts -alias zhubang -keystore D:\software\java\jdk8\jdk1.8.0_71\jre\lib\security\cacerts -file d:\zhubang.cer -storepass changeit
• 指定别名查看
  keytool -list -alias zhubang -keystore D:\software\java\jdk8\jdk1.8.0_71\jre\lib\security\cacerts -storepass changeit

• 删除指定别名的证书
  keytool -delete -alias zhubang -keystore D:\software\java\jdk8\jdk1.8.0_71\jre\lib\security\cacerts -storepass changeit

• 导入证书方法2）通过java代码（工具类），下载证书

import javax.net.ssl.*;
import java.io.*;
import java.security.KeyStore;
import java.security.MessageDigest;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

/**
 * 工具类功能描述：
 * 下载指定网站的https证书保存到本地
 *
 * 使用方法：
 * 根据运行提示信息，输入1，回车，在当前目录下生成名为:jssecacerts 的证书
 * 将证书放置到$JAVA_HOME/jre/lib/security目录下重启java程序即可生效，切记该JDK的jre是当前工程所用的环境
 * 或者根据刚才生成的文件jssecacerts，生成.cer文件，然后通过import导入JRE下的cacerts证书库，这样就不需要把jssecacerts放到JRE目录下
 * 命令如下：
 * keytool -export -alias xxx -keystore {文件路径}/jssecacerts -rfc -file yyy.cer
 * 其中別名xxx要和生成jssecacerts时用的别名一致
 *
 * @author Evan
 */
public class InstallCacerts {

    /**
     * 要访问的HTTPS服务的主机名:端口，如访问 https://mf.joobank.com
     */
    public static final String HOSTNAME = "mf.joobank.com";

    public static void main(String[] args) throws Exception {
        args = new String[]{HOSTNAME};
        String host;
        int port;
        char[] passphrase;
        if ((args.length == 1) || (args.length == 2)) {
            String[] c = args[0].split(":");
            host = c[0];
            port = (c.length == 1) ? 443 : Integer.parseInt(c[1]);
            //java keytool默认的密码是changeit
            String p = (args.length == 1) ? "changeit" : args[1];
            passphrase = p.toCharArray();
        } else {
            System.out.println("Usage: java InstallCacerts <host>[:port] [passphrase]");
            return;
        }

        File file = new File("jssecacerts");
        if (file.isFile() == false) {
            File dir = new File(System.getProperty("java.home") + File.separatorChar + "lib" + File.separatorChar + "security");
            //先看默认的证书库jssecacerts是否存在
            file = new File(dir, "jssecacerts");
            //如果不存在则使用cacerts(它随J2SDK一起发行,含有数量有限的可信任的基本证书)
            if (file.isFile() == false) {
                file = new File(dir, "cacerts");
            }
        }
        System.out.println("Loading KeyStore " + file + "...");
        InputStream in = new FileInputStream(file);
        KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
        ks.load(in, passphrase);
        in.close();

        SSLContext context = SSLContext.getInstance("TLS");
        TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
        tmf.init(ks);
        X509TrustManager defaultTrustManager = (X509TrustManager) tmf.getTrustManagers()[0];
        SavingTrustManager tm = new SavingTrustManager(defaultTrustManager);
        context.init(null, new TrustManager[]{tm}, null);
        SSLSocketFactory factory = context.getSocketFactory();

        System.out.println("Opening connection to " + host + ":" + port + "...");
        SSLSocket socket = (SSLSocket) factory.createSocket(host, port);
        socket.setSoTimeout(10000);
        try {
            System.out.println("Starting SSL handshake...");
            socket.startHandshake();
            socket.close();
            System.out.println();
            System.out.println("No errors, certificate is already trusted");
        } catch (SSLException e) {
            System.out.println();
            e.printStackTrace(System.out);
        }

        X509Certificate[] chain = tm.chain;
        if (chain == null) {
            System.out.println("Could not obtain server certificate chain");
            return;
        }

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        System.out.println();
        System.out.println("Server sent " + chain.length + " certificate(s):");
        System.out.println();
        MessageDigest sha1 = MessageDigest.getInstance("SHA1");
        MessageDigest md5 = MessageDigest.getInstance("MD5");
        for (int i = 0; i < chain.length; i++) {
            X509Certificate cert = chain[i];
            System.out.println(" " + (i + 1) + " Subject " + cert.getSubjectDN());
            System.out.println("   Issuer  " + cert.getIssuerDN());
            sha1.update(cert.getEncoded());
            System.out.println("   sha1    " + toHexString(sha1.digest()));
            md5.update(cert.getEncoded());
            System.out.println("   md5     " + toHexString(md5.digest()));
            System.out.println();
        }

        System.out.println("Enter certificate to add to trusted keystore or 'q' to quit: [1]");
        String line = reader.readLine().trim();
        int k;
        try {
            k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1;
        } catch (NumberFormatException e) {
            System.out.println("KeyStore not changed");
            return;
        }

        X509Certificate cert = chain[k];
        String alias = host + "-" + (k + 1);
        ks.setCertificateEntry(alias, cert);

        OutputStream out = new FileOutputStream("jssecacerts");
        ks.store(out, passphrase);
        out.close();

        System.out.println();
        System.out.println(cert);
        System.out.println();
        System.out.println("Added certificate to keystore 'jssecacerts' using alias '" + alias + "'");

    }

    private static final char[] HEXDIGITS = "0123456789abcdef".toCharArray();

    private static String toHexString(byte[] bytes) {
        StringBuilder sb = new StringBuilder(bytes.length * 3);
        for (int b : bytes) {
            b &= 0xff;
            sb.append(HEXDIGITS[b >> 4]);
            sb.append(HEXDIGITS[b & 15]);
            sb.append(' ');
        }
        return sb.toString();
    }

    private static class SavingTrustManager implements X509TrustManager {

        private final X509TrustManager tm;
        private X509Certificate[] chain;

        SavingTrustManager(X509TrustManager tm) {
            this.tm = tm;
        }

        @Override
        public X509Certificate[] getAcceptedIssuers() {
            throw new UnsupportedOperationException();
        }

        @Override
        public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            throw new UnsupportedOperationException();
        }

        @Override
        public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            this.chain = chain;
            tm.checkServerTrusted(chain, authType);
        }
    }

}