/*

 * Copyright (c) 2011, 2015, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/**

 * @see SignUsingSHA2withRSA.sh

 */

import java.security.*;

import java.util.*;

public class SignUsingSHA2withRSA {

    private static final byte[] toBeSigned = new byte[] {

        0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x10

    };

    private static List<byte[]> generatedSignatures = new ArrayList<>();

    public static void main(String[] args) throws Exception {

        Provider[] providers = Security.getProviders("Signature.SHA256withRSA");

        if (providers == null) {

            System.out.println("No JCE providers support the " +

                "'Signature.SHA256withRSA' algorithm");

            System.out.println("Skipping this test...");

            return;

        } else {

            System.out.println("The following JCE providers support the " +

                "'Signature.SHA256withRSA' algorithm: ");

            for (Provider provider : providers) {

                System.out.println("    " + provider.getName());

            }

        }

        System.out.println("-------------------------------------------------");

        KeyStore ks = KeyStore.getInstance("Windows-MY", "SunMSCAPI");

        ks.load(null, null);

        System.out.println("Loaded keystore: Windows-MY");

        Enumeration<String> e = ks.aliases();

        PrivateKey privateKey = null;

        PublicKey publicKey = null;

        while (e.hasMoreElements()) {

            String alias = e.nextElement();

            if (alias.equals("6753664")) {

                System.out.println("Loaded entry: " + alias);

                privateKey = (PrivateKey) ks.getKey(alias, null);

                publicKey = (PublicKey) ks.getCertificate(alias).getPublicKey();

            }

        }

        if (privateKey == null || publicKey == null) {

            throw new Exception("Cannot load the keys need to run this test");

        }

        System.out.println("-------------------------------------------------");

        generatedSignatures.add(signUsing("SHA256withRSA", privateKey));

        generatedSignatures.add(signUsing("SHA384withRSA", privateKey));

        generatedSignatures.add(signUsing("SHA512withRSA", privateKey));

        System.out.println("-------------------------------------------------");

        verifyUsing("SHA256withRSA", publicKey, generatedSignatures.get(0));

        verifyUsing("SHA384withRSA", publicKey, generatedSignatures.get(1));

        verifyUsing("SHA512withRSA", publicKey, generatedSignatures.get(2));

        System.out.println("-------------------------------------------------");

    }

    private static byte[] signUsing(String signAlgorithm,

        PrivateKey privateKey) throws Exception {

        // Must explicitly specify the SunMSCAPI JCE provider

        // (otherwise SunJCE is chosen because it appears earlier in the list)

        Signature sig1 = Signature.getInstance(signAlgorithm, "SunMSCAPI");

        if (sig1 == null) {

            throw new Exception("'" + signAlgorithm + "' is not supported");

        }

        System.out.println("Using " + signAlgorithm + " signer from the " +

            sig1.getProvider().getName() + " JCE provider");

        System.out.println("Using key: " + privateKey);

        sig1.initSign(privateKey);

        sig1.update(toBeSigned);

        byte [] sigBytes = null;

        try {

            sigBytes = sig1.sign();

            System.out.println("Generated RSA signature over a " +

                toBeSigned.length + "-byte data (signature length: " +

                sigBytes.length * 8 + " bits)");

            System.out.println(String.format("0x%0" +

                (sigBytes.length * 2) + "x",

                new java.math.BigInteger(1, sigBytes)));

        } catch (SignatureException se) {

                System.out.println("Error generating RSA signature: " + se);

        }

        return sigBytes;

    }

    private static void verifyUsing(String signAlgorithm, PublicKey publicKey,

        byte[] signature) throws Exception {

        // Must explicitly specify the SunMSCAPI JCE provider

        // (otherwise SunJCE is chosen because it appears earlier in the list)

        Signature sig1 = Signature.getInstance(signAlgorithm, "SunMSCAPI");

        if (sig1 == null) {

            throw new Exception("'" + signAlgorithm + "' is not supported");

        }

        System.out.println("Using " + signAlgorithm + " verifier from the "

            + sig1.getProvider().getName() + " JCE provider");

        System.out.println("Using key: " + publicKey);

        System.out.println("\nVerifying RSA Signature over a " +

            toBeSigned.length + "-byte data (signature length: " +

            signature.length * 8 + " bits)");

        System.out.println(String.format("0x%0" + (signature.length * 2) +

            "x", new java.math.BigInteger(1, signature)));

        sig1.initVerify(publicKey);

        sig1.update(toBeSigned);

        if (sig1.verify(signature)) {

            System.out.println("Verify PASSED\n");

        } else {

            throw new Exception("Verify FAILED");

        }

    }

}