Generate certificate chain in java

Question

The question is how to generate certificate chains programmatically in Java. In other words, I would like to perform in java the operations detailed here: http://fusesource.com/docs/broker/5.3/security/i382664.html

Besically, I can create the RSA keys for a new client:

private KeyPair genRSAKeyPair(){
    // Get RSA key factory:
    KeyPairGenerator kpg = null;
    try {
        kpg = KeyPairGenerator.getInstance("RSA");
    } catch (NoSuchAlgorithmException e) {
        log.error(e.getMessage());
        e.printStackTrace();
        return null;
    }
    // Generate RSA public/private key pair:
    kpg.initialize(RSA_KEY_LEN);
    KeyPair kp = kpg.genKeyPair();
    return kp;

}

and I generate the corresponding certificate:

private X509Certificate generateCertificate(String dn, KeyPair pair, int days, String algorithm)
  throws GeneralSecurityException, IOException  {
    PrivateKey privkey = pair.getPrivate();
    X509CertInfo info = new X509CertInfo();
    Date from = new Date();
    Date to = new Date(from.getTime() + days * 86400000l);
    CertificateValidity interval = new CertificateValidity(from, to);
    BigInteger sn = new BigInteger(64, new SecureRandom());
    X500Name owner = new X500Name(dn);

    info.set(X509CertInfo.VALIDITY, interval);
    info.set(X509CertInfo.SERIAL_NUMBER, new CertificateSerialNumber(sn));
    info.set(X509CertInfo.SUBJECT, new CertificateSubjectName(owner));
    info.set(X509CertInfo.ISSUER, new CertificateIssuerName(owner));
    info.set(X509CertInfo.KEY, new CertificateX509Key(pair.getPublic()));
    info.set(X509CertInfo.VERSION, new CertificateVersion(CertificateVersion.V3));
    AlgorithmId algo = new AlgorithmId(AlgorithmId.md5WithRSAEncryption_oid);
    info.set(X509CertInfo.ALGORITHM_ID, new CertificateAlgorithmId(algo));

    // Sign the cert to identify the algorithm that's used.
    X509CertImpl cert = new X509CertImpl(info);
    cert.sign(privkey, algorithm);

    // Update the algorith, and resign.
    algo = (AlgorithmId)cert.get(X509CertImpl.SIG_ALG);
    info.set(CertificateAlgorithmId.NAME + "." + CertificateAlgorithmId.ALGORITHM, algo);
    cert = new X509CertImpl(info);
    cert.sign(privkey, algorithm);
    return cert;

}

Then I generate the cert signing request and I save it to csrFile file:

public static void writeCertReq(File csrFile, String alias, String keyPass, KeyStore ks) 
        throws KeyStoreException, 
               NoSuchAlgorithmException, 
               InvalidKeyException, 
               IOException, 
               CertificateException, 
               SignatureException, 
               UnrecoverableKeyException {

    Object objs[] = getPrivateKey(ks, alias, keyPass.toCharArray());
    PrivateKey privKey = (PrivateKey) objs[0];

    PKCS10 request = null;

    Certificate cert = ks.getCertificate(alias);
    request = new PKCS10(cert.getPublicKey());
    String sigAlgName = "MD5WithRSA";
    Signature signature = Signature.getInstance(sigAlgName);
    signature.initSign(privKey);
    X500Name subject = new X500Name(((X509Certificate) cert).getSubjectDN().toString());
    X500Signer signer = new X500Signer(signature, subject);
    request.encodeAndSign(signer);
    request.print(System.out);
    FileOutputStream fos = new FileOutputStream(csrFile);
    PrintStream ps = new PrintStream(fos);
    request.print(ps);
    fos.close();
}

where

private static Object[] getPrivateKey(KeyStore ks, String alias, char keyPass[]) 
        throws UnrecoverableKeyException, KeyStoreException, NoSuchAlgorithmException {
    key = null;        
    key = ks.getKey(alias, keyPass);
    return (new Object[]{ (PrivateKey) key, keyPass });
}

Now I should sign the CSR with the CA private key, but I cannot see how to achive that in java. I have "my own" CA private key in my jks.

Besides, once I manage to sign the CSR I should chain the CA cert with the signed CSR: how that can be done in java?

I would prefer not to use bc or other external libs, just "sun.security" classes.

Thank you.

Answer 1

I believe the code example in the post http://www.pixelstech.net/article/1406726666-Generate-certificate-in-Java----2 will show you how to generate certificate chain with pure Java. It doesn't require you to use Bouncy Castle.