pragmatic-penguin pragmatic-penguin - 3 months ago 27
Java Question

How do you generate a CSR in Java without signing it by the requester?

Basically, I need to isolate the data of the constructed CSR (Certificate Signing Request) prior to it being first signed by the entity making the request, preferably in Java. Many thanks in advance!

It would also be useful to note how to subsequently append the signature to the CSR as the CSR data will be initially signed by an HSM.

Answer

I hope this helps:

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;


import javax.security.auth.x500.X500Principal;

import sun.security.pkcs10.*;
import sun.security.x509.*;

public class GenerateCSR {
    private static PublicKey publicKey = null;
    private static PrivateKey privateKey = null;
    private static KeyPairGenerator keyGen = null;
    private static GenerateCSR gcsr = null;

    private GenerateCSR() {
        try {
            keyGen = KeyPairGenerator.getInstance("RSA");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        keyGen.initialize(2048, new SecureRandom());
        KeyPair keypair = keyGen.generateKeyPair();
        publicKey = keypair.getPublic();
        privateKey = keypair.getPrivate();
    }

    public static GenerateCSR getInstance() {
        if (gcsr == null)
            gcsr = new GenerateCSR();
        return gcsr;
    }

    public String getCSR(String cn) throws Exception {
        byte[] csr = generatePKCS10(cn, "Java", "JournalDev", "Cupertino",
                "California", "USA");
        return new String(csr);
    }

    /**
     *
     * @param CN
     *            Common Name, is X.509 speak for the name that distinguishes
     *            the Certificate best, and ties it to your Organization
     * @param OU
     *            Organizational unit
     * @param O
     *            Organization NAME
     * @param L
     *            Location
     * @param S
     *            State
     * @param C
     *            Country
     * @return
     * @throws Exception
     */
    private static byte[] generatePKCS10(String CN, String OU, String O,
            String L, String S, String C) throws Exception {
        // generate PKCS10 certificate request
        String sigAlg = "MD5WithRSA";
        PKCS10 pkcs10 = new PKCS10(publicKey);
        Signature signature = Signature.getInstance(sigAlg);
        signature.initSign(privateKey);
        // common, orgUnit, org, locality, state, country
        X500Principal principal = new X500Principal( "CN=Ole Nordmann, OU=ACME, O=Sales, C=NO");

   //     pkcs10CertificationRequest kpGen = new PKCS10CertificationRequest(sigAlg, principal, publicKey, null, privateKey);  
     //   byte[] c = kpGen.getEncoded();  
        X500Name x500name=null;
        x500name= new X500Name(principal.getEncoded());
      pkcs10.encodeAndSign(x500name, signature);
        ByteArrayOutputStream bs = new ByteArrayOutputStream();
        PrintStream ps = new PrintStream(bs);
        pkcs10.print(ps);
        byte[] c = bs.toByteArray();
        try {
            if (ps != null)
                ps.close();
            if (bs != null)
                bs.close();
        } catch (Throwable th) {
        }
        return c;
    }

    public PublicKey getPublicKey() {
        return publicKey;
    }

    public PrivateKey getPrivateKey() {
        return privateKey;
    }

    public static void main(String[] args) throws Exception {
        GenerateCSR gcsr = GenerateCSR.getInstance();

        System.out.println("Public Key:\n"+gcsr.getPublicKey().toString());

        System.out.println("Private Key:\n"+gcsr.getPrivateKey().toString());
        String csr = gcsr.getCSR("journaldev.com <http://www.journaldev.com>");
        System.out.println("CSR Request Generated!!");
        System.out.println(csr);
    }

}
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