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

Sorry, but despite your desires, and besides writing all of your crypto code and including it with your project (not recommended), I’d recommend using Bouncy Castle here.

Specifically, please refer to https://stackoverflow.com/a/7366757/751158 – which includes code for exactly what you’re looking to do.