Sample Code for Two-Way Authentication During the Access to a Cluster

import org.apache.commons.io.IOUtils;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.HttpHost;
import org.apache.http.nio.conn.ssl.SSLIOSessionStrategy;
import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHits;
import org.elasticsearch.search.builder.SearchSourceBuilder;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.KeyStore;
import java.security.SecureRandom;
import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.TrustManagerFactory;
public class ESSecuredClientWithCerDemo {
    private static final String KEY_STORE_PWD = "";
    private static final String TRUST_KEY_STORE_PWD = "";
    private static final String CA_JKS_PATH = "ca.jks";
    private static final String CLIENT_JKS_PATH = "client.jks";
    private static final String ELB_ADDRESS = "127.0.0.1";
    private static final int ELB_PORT = 9200;
    private static final String CSS_USERNAME = "user";
    private static final String CSS_PWD = "";
    public static void main(String[] args) {
       // Create a client.
        RestHighLevelClient client = initESClient(ELB_ADDRESS, CSS_USERNAME, CSS_PWD);
        try {
         // Search match_all, which is equivalent to {\"query\": {\"match_all\": {}}}.
            SearchRequest searchRequest = new SearchRequest();
            SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
            searchSourceBuilder.query(QueryBuilders.matchAllQuery());
            searchRequest.source(searchSourceBuilder);
            // query
            SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
            System.out.println("query result: " + searchResponse.toString());
            SearchHits hits = searchResponse.getHits();
            for (SearchHit hit : hits) {
                System.out.println(hit.getSourceAsString());
            }
            System.out.println("query success");
            Thread.sleep(2000L);
        } catch (InterruptedException | IOException e) {
            e.printStackTrace();
        } finally {
            IOUtils.closeQuietly(client);
        }
    }
    private static RestHighLevelClient initESClient(String clusterAddress, String userName, String password) {
        final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(userName, password));
        SSLContext ctx = null;
        try {
            KeyStore ks = getKeyStore(CLIENT_JKS_PATH, KEY_STORE_PWD, "JKS");
            KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
            kmf.init(ks, KEY_STORE_PWD.toCharArray());
            KeyStore tks = getKeyStore(CA_JKS_PATH, TRUST_KEY_STORE_PWD, "JKS");
            TrustManagerFactory tmf = TrustManagerFactory.getInstance("SunX509");
            tmf.init(tks);
            ctx = SSLContext.getInstance("SSL", "SunJSSE");
            ctx.init(kmf.getKeyManagers(), tmf.getTrustManagers(), new SecureRandom());
        } catch (Exception e) {
            e.printStackTrace();
        }
        SSLIOSessionStrategy sessionStrategy = new SSLIOSessionStrategy(ctx, new HostnameVerifier() {
            @Override
            public boolean verify(String arg0, SSLSession arg1) {
                return true;
            }
        });
        SecuredHttpClientConfigCallback httpClientConfigCallback = new SecuredHttpClientConfigCallback(sessionStrategy,
            credentialsProvider);
        RestClientBuilder builder = RestClient.builder(new HttpHost(clusterAddress, ELB_PORT, "https"))
            .setHttpClientConfigCallback(httpClientConfigCallback);
        RestHighLevelClient client = new RestHighLevelClient(builder);
        return client;
    }
    private static KeyStore getKeyStore(String path, String pwd, String type) {
        KeyStore keyStore = null;
        FileInputStream is = null;
        try {
            is = new FileInputStream(path);
            keyStore = KeyStore.getInstance(type);
            keyStore.load(is, pwd.toCharArray());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            IOUtils.closeQuietly(is);
        }
        return keyStore;
    }
}

import org.apache.http.client.CredentialsProvider;
import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
import org.apache.http.nio.conn.ssl.SSLIOSessionStrategy;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.common.Nullable;
import java.util.Objects;
class SecuredHttpClientConfigCallback implements RestClientBuilder.HttpClientConfigCallback {
    @Nullable
    private final CredentialsProvider credentialsProvider;
    /**
     * The {@link SSLIOSessionStrategy} for all requests to enable SSL / TLS encryption.
     */
    private final SSLIOSessionStrategy sslStrategy;
    /**
     * Create a new {@link SecuredHttpClientConfigCallback}.
     *
     * @param credentialsProvider The credential provider, if a username/password have been supplied
     * @param sslStrategy         The SSL strategy, if SSL / TLS have been supplied
     * @throws NullPointerException if {@code sslStrategy} is {@code null}
     */
    SecuredHttpClientConfigCallback(final SSLIOSessionStrategy sslStrategy,
        @Nullable final CredentialsProvider credentialsProvider) {
        this.sslStrategy = Objects.requireNonNull(sslStrategy);
        this.credentialsProvider = credentialsProvider;
    }
    /**
     * Get the {@link CredentialsProvider} that will be added to the HTTP client.
     *
     * @return Can be {@code null}.
     */
    @Nullable
    CredentialsProvider getCredentialsProvider() {
        return credentialsProvider;
    }
    /**
     * Get the {@link SSLIOSessionStrategy} that will be added to the HTTP client.
     *
     * @return Never {@code null}.
     */
    SSLIOSessionStrategy getSSLStrategy() {
        return sslStrategy;
    }
    /**
     * Sets the {@linkplain HttpAsyncClientBuilder#setDefaultCredentialsProvider(CredentialsProvider) credential provider},
     *
     * @param httpClientBuilder The client to configure.
     * @return Always {@code httpClientBuilder}.
     */
    @Override
    public HttpAsyncClientBuilder customizeHttpClient(final HttpAsyncClientBuilder httpClientBuilder) {
        // enable SSL / TLS
        httpClientBuilder.setSSLStrategy(sslStrategy);
        // enable user authentication
        if (credentialsProvider != null) {
            httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
        }
        return httpClientBuilder;
    }
}