How do I use an SSL client certificate with Apache HttpClient?

I think the main difference is that in java, you usually put the key and the certificate to a key store and use it from there. Like you mention often people do want to use a separate library for it, like mentioned httpcomponents client (just like you’re using requests library in your python example).

Here’s an example of using a client certificate from a key store, using the previously mentioned library:

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.ssl.SSLContexts;
import org.apache.http.util.EntityUtils;
import org.junit.Test;

import javax.net.ssl.SSLContext;
import java.io.InputStream;
import java.security.KeyStore;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

public class MyClientCertTest {

    private static final String KEYSTOREPATH = "/clientkeystore.jks"; // or .p12
    private static final String KEYSTOREPASS = "keystorepass";
    private static final String KEYPASS = "keypass";

    KeyStore readStore() throws Exception {
        try (InputStream keyStoreStream = this.getClass().getResourceAsStream(KEYSTOREPATH)) {
            KeyStore keyStore = KeyStore.getInstance("JKS"); // or "PKCS12"
            keyStore.load(keyStoreStream, KEYSTOREPASS.toCharArray());
            return keyStore;
        }
    }
    @Test
    public void readKeyStore() throws Exception {
        assertNotNull(readStore());
    }
    @Test
    public void performClientRequest() throws Exception {
        SSLContext sslContext = SSLContexts.custom()
                .loadKeyMaterial(readStore(), KEYPASS.toCharArray()) // use null as second param if you don't have a separate key password
                .build();

        HttpClient httpClient = HttpClients.custom().setSSLContext(sslContext).build();
        HttpResponse response = httpClient.execute(new HttpGet("https://slsh.iki.fi/client-certificate/protected/"));
        assertEquals(200, response.getStatusLine().getStatusCode());
        HttpEntity entity = response.getEntity();

        System.out.println("----------------------------------------");
        System.out.println(response.getStatusLine());
        EntityUtils.consume(entity);
    }
}

Maven pom for dependency versions:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.acme</groupId>
    <artifactId>httptests</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.3</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.9</version>
                <!-- this is not needed, but useful if you want to debug what's going
                     on with your connection -->
                <configuration>
                    <argLine>-Djavax.net.debug=all</argLine>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

I’ve also published a simple test page for testing a client certificate.


Just to demonstrate that it can be done, below is an example of using client certificate just using standard java api, without extra libraries.

import org.junit.Test;

import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.KeyManager;
import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.security.KeyStore;

public class PlainJavaHTTPS2Test {

    @Test
    public void testJKSKeyStore() throws Exception {
        final String KEYSTOREPATH = "clientkeystore.jks";
        final char[] KEYSTOREPASS = "keystorepass".toCharArray();
        final char[] KEYPASS = "keypass".toCharArray();

        try (InputStream storeStream = this.getClass().getResourceAsStream(KEYSTOREPATH)) {
            setSSLFactories(storeStream, "JKS", KEYSTOREPASS, KEYPASS);
        }
        testPlainJavaHTTPS();
    }
    @Test
    public void testP12KeyStore() throws Exception {
        final String KEYSTOREPATH = "clientkeystore.p12";
        final char[] KEYSTOREPASS = "keystorepass".toCharArray();
        final char[] KEYPASS = "keypass".toCharArray();

        try (InputStream storeStream = this.getClass().getResourceAsStream(KEYSTOREPATH)) {
            setSSLFactories(storeStream, "PKCS12", KEYSTOREPASS, KEYPASS);
        }
        testPlainJavaHTTPS();
    }
    private static void setSSLFactories(InputStream keyStream, String keystoreType, char[] keyStorePassword, char[] keyPassword) throws Exception
    {
        KeyStore keyStore = KeyStore.getInstance(keystoreType);

        keyStore.load(keyStream, keyStorePassword);

        KeyManagerFactory keyFactory =
                KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());

        keyFactory.init(keyStore, keyPassword);

        KeyManager[] keyManagers = keyFactory.getKeyManagers();

        SSLContext sslContext = SSLContext.getInstance("SSL");
        sslContext.init(keyManagers, null, null);
        SSLContext.setDefault(sslContext);
    }

    public void testPlainJavaHTTPS() throws Exception {
        String httpsURL = "https://slsh.iki.fi/client-certificate/protected/";
        URL myUrl = new URL(httpsURL);
        HttpsURLConnection conn = (HttpsURLConnection)myUrl.openConnection();
        try (InputStream is = conn.getInputStream()) {
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader br = new BufferedReader(isr);

            String inputLine;

            while ((inputLine = br.readLine()) != null) {
                System.out.println(inputLine);
            }
        }
    }
}

And here’s a third version with least amount of code, but which relies on the fact that a) keystore is a file on disk, not within jar, and b) key password must be identical to keystore password.

import org.junit.BeforeClass;
import org.junit.Test;

import java.net.URL;
import java.io.*;
import javax.net.ssl.HttpsURLConnection;

public class PlainJavaHTTPSTest {

    @BeforeClass
    public static void setUp() {
        System.setProperty("javax.net.ssl.keyStore", "/full/path/to/clientkeystore-samepassword.jks");
        System.setProperty("javax.net.ssl.keyStorePassword", "keystorepass");
    }

    @Test
    public void testPlainJavaHTTPS() throws Exception {
        String httpsURL = "https://slsh.iki.fi/client-certificate/protected/";
        URL myUrl = new URL(httpsURL);
        HttpsURLConnection conn = (HttpsURLConnection)myUrl.openConnection();
        try (InputStream is = conn.getInputStream()) {
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader br = new BufferedReader(isr);

            String inputLine;

            while ((inputLine = br.readLine()) != null) {
                System.out.println(inputLine);
            }
        }
    }
}

The properties set above in code can of course be also given as startup parameters, -Djavax.net.ssl.keyStore=/full/path/to/clientkeystore-samepassword.jks and -Djavax.net.ssl.keyStorePassword=keystorepass.

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