App.java

package com.salesforce.app;

import java.io.IOException;
import java.net.URISyntaxException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.security.cert.X509Certificate;
import java.security.cert.CertificateFactory;
import java.util.Base64;
import java.util.Base64.Encoder;
import java.util.Base64.Decoder;
import java.util.HashMap;
import java.util.Map;
import java.io.FileInputStream;
import javax.xml.bind.DatatypeConverter;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import com.google.gson.*;
import java.security.cert.X509Certificate;
import com.nimbusds.jose.jwk.RSAKey;
import com.nimbusds.jose.util.X509CertUtils;
import java.security.*;
import java.security.interfaces.*;
import java.util.*;
import com.nimbusds.jose.jwk.*;
import com.nimbusds.jose.jwk.gen.*;

public class App {
    public static void main(String[] args) {
        System.out.println("JWKS Generator");
        try {
            Gson gson = new Gson();
            System.out.println(generateJWK(args[0], args[0]));
            System.out.println();
            System.out.println("-------manual-JWK----");
            System.out.println(gson.toJson(generateJWK(args[0], args[0])));
            System.out.println("-------manual-JWK----");
            FileInputStream fin = new FileInputStream(args[0]);
            CertificateFactory f = CertificateFactory.getInstance("X.509");
            X509Certificate certificate = (X509Certificate) f.generateCertificate(fin);
            X509Certificate cert = X509CertUtils.parse(certificate.getEncoded());
            RSAKey rsaJWK = RSAKey.parse(cert);
            System.out.println("-------om.nimbusds.jose.jwk.RSAKey-JWK----");
            System.out.println(rsaJWK.toPublicJWK());
            System.out.println("-------om.nimbusds.jose.jwk.RSAKey-JWK----");

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static Map<String, Object> generateJWK(String env, String location) {
        Map<String, Object> values = new HashMap<>();
        try {
            FileInputStream fin = new FileInputStream(location);
            CertificateFactory f = CertificateFactory.getInstance("X.509");
            X509Certificate certificate = (X509Certificate) f.generateCertificate(fin);
            String thumbprint = getThumbprint(certificate);

            System.out.println("Subject DN : " + certificate.getSubjectDN().getName());
            System.out.println("Issuer : " + certificate.getIssuerDN().getName());
            System.out.println("Not After: " + certificate.getNotAfter());
            System.out.println("Not Before: " + certificate.getNotBefore());
            System.out.println("version: " + certificate.getVersion());
            System.out.println("serial number : " + certificate.getSerialNumber());

            PublicKey pk = certificate.getPublicKey();
            RSAPublicKey rsa = (RSAPublicKey) pk;
            values.put("kty", rsa.getAlgorithm()); // getAlgorithm() returns kty not algorithm
            values.put("kid", env);
            values.put("x5t", thumbprint);
            values.put("n", Base64.getUrlEncoder().encodeToString(rsa.getModulus().toByteArray()));
            values.put("e", Base64.getUrlEncoder().encodeToString(rsa.getPublicExponent().toByteArray()));
            values.put("alg", "RS256");
            values.put("use", "sig");
        } catch (Exception e) {
            e.printStackTrace();
        }
        return values;
    }

    private static String getThumbprint(X509Certificate cert)
            throws NoSuchAlgorithmException, CertificateEncodingException {
        MessageDigest md = MessageDigest.getInstance("SHA-1");
        byte[] der = cert.getEncoded();
        md.update(der);
        byte[] digest = md.digest();
        String digestHex = DatatypeConverter.printHexBinary(digest);
        return digestHex.toLowerCase();
    }

}