【Java】# 请求https时证书不可信 PKIX SunCertPathBuilderException：unable to find valid certification....

背景：当使用 Java 请求 https协议的服务时，报 ’unable to find valid certification path to requested target’ 异常

解决方式1：将请求服务的证书导入到 JDK的 cacerts中

• 通过浏览器先访问网址，然后将证书进行导出（以 Edge浏览器为例）

  

• 以管理员身份打开cmd，进入到 “%JAVA_HOME%/jre/lib/\security”目录下，执行以下命令

  keytool -import -keystore cacerts -alias server -file 证书的位置
      -file：指定证书文件的位置
      -keystore：安装证书到的位置
      -alias：指定证书的别名
  

• 输入密钥库默认口令：changeit，输入 “Y”信任此证书即可

解决方式2：使用Java类生成证书

• InstallCert.java类会连接到给定的host，开始握手过程。如果出现异常会打印到控制台并且会显示服务端所使用的证书，此时它会问是否要把证书加入到keystore中。
• 如果不想加，输入”q”,否则输入”1”.
• 当输入”1”后，InstallCert.java 会显示证书的有关信息，然后把证书导入到一个名为”jssecacerts”的keystore中（生成在当前目录），只需要把这个文件拷贝到 %JAVA_HOME%/jre/lib/security 目录中即可

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;

public class InstallCert {
    public static void main(String[] args) {
        try {
            installCert("110.242.68.4", 443);  // https://www.baidu.com
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

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

    /**
     * 安装证书
     *
     * @param requestUrl 请求https服务的地址
     * @param port       https默认端口为 443
     * @throws Exception
     */
    public static void installCert(String requestUrl, int port) throws Exception {
        // 密钥库默认口令，一般默认changeit
        String pwd = "changeit";
        char[] passphrase = pwd.toCharArray();

        File file = new File("jssecacerts");
        if (!file.isFile()) {
            char sep = File.separatorChar;
            File dir = new File(System.getProperty("java.home") + sep + "lib" + sep + "security");
            file = new File(dir, "jssecacerts");
            if (!file.isFile()) {
                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 " + requestUrl + ":" + port + "...");
        SSLSocket socket = (SSLSocket) factory.createSocket(requestUrl, port);
        socket.setSoTimeout(10000);
        try {
            System.out.println("Starting SSL handshake...");
            socket.startHandshake();
            socket.close();
            System.out.println("\nNo 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("\nServer sent " + chain.length + " certificate(s):\n");
        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 = requestUrl + "-" + (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 + "'");
    }

    /**
     * 转为16进制
     *
     * @param bytes
     * @return
     */
    private static String toHexString(byte[] bytes) {
        StringBuilder sb = new StringBuilder(bytes.length * 3);
        for (int b : bytes) {
            b &= 0xff;
            sb.append(HEX_DIGITS[b >> 4]);
            sb.append(HEX_DIGITS[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) {
            throw new UnsupportedOperationException();
        }

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

原因：服务端的证书没有被Java认证，所以导致请求失败

Java程序对受信证书的查找顺序：

• javax.net.ssl.trustStore

  就是 System.setProperty(“javax.net.ssl.trustStore”, “D:\cacert.keystore”);

  或者通过JVM参数指定：-Djavax.net.ssl.trustStore=D:\cacert.keystore

• %JAVA_HOME%\jre\lib\security\jssecacerts 【推荐】

  默认没有jssecacerts，一般把cacerts复制成jssecacerts，然后再使用keytool来修改它。

  jsse的全称是Java Secure Socket Extension。

• %JAVA_HOME%\jre\lib\security\cacerts

  通常情况下不建议通过-Djavax.net.ssl.trustStore=D:\cacert.keystore来直接修改keystore文件的位置，因为这样会造成系统中其他模块可能找不到自己对应的证书了。