Java and SSL certificates

I have found out that to ensure maxium security/validity I have to import the SSL certificate that my website uses into my application

You are partially right when you make that statement. You do not need to import your SSL certificate. It is sufficient that the StartSSL CA certificate be imported.

Additionally, there is no such thing as importing a certificate into a Java application. SSL support in Java relies on the concept of keystores and truststores, and not on some certificate packaged within your application. If you are publishing your application to be downloaded and executed by end-users, there is no need for your to publish your certificate or for that matter your private key in your application. The private key, and the associated certificate would be stored in a keystore, that only you may access.

The end-users of your application would rely on the SSL support within the Java runtime, that would enable the application to establish SSL connections to sites, after the server-certificate is verified. The Java runtime ships with a default set of CA certificates in a truststore, and the only prerequisite for SSL connections to be successfully established is that the SSL certificate of the server be issued by one of the CAs in the truststore. The certificates of StartSSL are not present in the truststore of the Java runtime, atleast as of version 6, and therefore:

• You could instruct your end users to perform the activity of importing the StartSSL CA certificate into the Java truststore. Links that may help include this StartSSL forum thread (only the first 4 steps are needed to import the CA certs into a truststore), a GitHub project, and this blog post; a disclaimer - I haven't attempted using any of those and you ought to be using it at your own risk.

• Or, you could initialize your application with your own truststore using the -Djavax.net.ssl.trustStore=<path_to_truststore> -Djavax.net.ssl.trustStorePassword=<truststore_password> JVM startup flags, or execute the following code before initializing SSL connections:

  System.setProperty("javax.net.ssl.trustStore","<path_to_truststore>");
  System.setProperty("javax.net.ssl.trustStorePassword","<truststore_password>");
  

  This is a viable approach only if your application is a Java SE application that does not happen to be an applet (or an application with similar restrictions on how the truststore is specified).

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It would also help to read up the Java keytool documentation.

The following method loads the default (cacerts) keystore, checks to see if a certificate is installed, and installs it if not. It eliminates the need to manually run the keystore command on any servers.

It assumes that the default keystore password (changeit) is unchanged, update CACERTS_PASSWORD if not. Note that the method saves the keystore after adding a certificate, so after being run once the certificate will permanently be in the store.

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;

/**
 * Add a certificate to the cacerts keystore if it's not already included
 */
public class SslUtil {
    private static final String CACERTS_PATH = "/lib/security/cacerts";

    // NOTE: DO NOT STORE PASSWORDS IN PLAIN TEXT CODE, LOAD AT RUNTIME FROM A SECURE CONFIG
    // DEFAULT CACERTS PASSWORD IS PROVIDED HERE AS A QUICK, NOT-FOR-PRODUCTION WORKING EXAMPLE
    // ALSO, CHANGE THE DEFAULT CACERTS PASSWORD, AS IT IMPLORES YOU TO!
    private static final String CACERTS_PASSWORD = "changeit";

    /**
     * Add a certificate to the cacerts keystore if it's not already included
     * 
     * @param alias The alias for the certificate, if added
     * @param certInputStream The certificate input stream
     * @throws KeyStoreException
     * @throws NoSuchAlgorithmException
     * @throws CertificateException
     * @throws IOException
     */
    public static void ensureSslCertIsInKeystore(String alias, InputStream certInputStream)
            throws KeyStoreException, NoSuchAlgorithmException, CertificateException, IOException{
        //get default cacerts file
        final File cacertsFile = new File(System.getProperty("java.home") + CACERTS_PATH);
        if (!cacertsFile.exists()) {
            throw new FileNotFoundException(cacertsFile.getAbsolutePath());
        }

        //load cacerts keystore
        FileInputStream cacertsIs = new FileInputStream(cacertsFile);
        final KeyStore cacerts = KeyStore.getInstance(KeyStore.getDefaultType());
        cacerts.load(cacertsIs, CACERTS_PASSWORD.toCharArray());
        cacertsIs.close();

        //load certificate from input stream
        final CertificateFactory cf = CertificateFactory.getInstance("X.509");
        final Certificate cert = cf.generateCertificate(certInputStream);
        certInputStream.close();

        //check if cacerts contains the certificate
        if (cacerts.getCertificateAlias(cert) == null) {
            //cacerts doesn't contain the certificate, add it
            cacerts.setCertificateEntry(alias, cert);
            //write the updated cacerts keystore
            FileOutputStream cacertsOs = new FileOutputStream(cacertsFile);
            cacerts.store(cacertsOs, CACERTS_PASSWORD.toCharArray());
            cacertsOs.close();
        }
    }
}

Use it like so:

SslUtil.ensureSslCertIsInKeystore("startssl", new FileInputStream("/path/to/cert.crt"));