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 * 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.

 *

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package jdk.test.lib;

import java.security.*;

import java.security.spec.*;

import java.util.*;

public class RSAUtil {

    public enum SignatureType {

        RSA_PKCS1_5,

        RSA_PSS,

    }    

    // collection of all supported RSA PKCS1.5 algorithms

    // note that the entries are ordered by required key sizes

    private static final String[] PKCS1_5_ALGS = {

        // these requires key size 768

        "SHA384withRSA", "SHA512withRSA",

        // these are supported by min key size 512

        "MD2withRSA", "MD5withRSA", "SHA1withRSA",

        "SHA224withRSA", "SHA512/224withRSA",

        "SHA256withRSA", "SHA512/256withRSA"

    };

    private static final int PKCS1_5_INDEX_768 = 0;

    private static final int PKCS1_5_INDEX_512 = 2;

    // collection of all supported RSA-PSS algorithms

    // note that the entries are ordered by required key sizes

    private static final String[] PSS_ALGS = {

        // these requires key size 2048

        "SHA512withRSAandMGF1",

        // these requires key size 1024

        "SHA384withRSAandMGF1",

        // these requires key size 768

        "SHA256withRSAandMGF1", "SHA512/256withRSAandMGF1",

        // these are supported by min key size 512

        "SHA1withRSAandMGF1", "SHA224withRSAandMGF1",

        "SHA512/224withRSAandMGF1"

    };

    private static final int PSS_INDEX_2048 = 0;

    private static final int PSS_INDEX_1024 = 1;

    private static final int PSS_INDEX_768 = 2;

    private static final int PSS_INDEX_512 = 4;

    public static Iterable<String> getSignatureAlgorithms(int keysize,

            SignatureType type) throws RuntimeException {

        List<String> algos;

        Iterable<String> result;

        switch (type) {

            case RSA_PKCS1_5:

                algos = new ArrayList<>(Arrays.asList(PKCS1_5_ALGS));

                if (keysize >= 768) {

                    result = algos.subList(PKCS1_5_INDEX_768, PKCS1_5_ALGS.length);

                } else {

                    result = algos.subList(PKCS1_5_INDEX_512, PKCS1_5_ALGS.length);

                }

                break;

            case RSA_PSS:

                algos = new ArrayList<>(Arrays.asList(PSS_ALGS));

                if (keysize >= 2048) {

                    result = algos.subList(PSS_INDEX_2048, PSS_ALGS.length);

                } else if (keysize >= 1024) {

                    result = algos.subList(PSS_INDEX_1024, PSS_ALGS.length);

                } else if (keysize >= 768) {

                    result = algos.subList(PSS_INDEX_768, PSS_ALGS.length);

                } else {

                    result = algos.subList(PSS_INDEX_512, PSS_ALGS.length);

                }

                break;

            default:

                throw new RuntimeException("Unsupported RSA signature algorithm type: " + type);

        }

        return result;

    }

    private static final String RSA_SIG_SUFFIX = "withRSA";

    private static final String RSAPSS_SIG_SUFFIX = "RSA-PSS";

    private static final String RSAPSS_SIG_SUFFIX2 = "withRSAandMGF1";

    public static AlgorithmParameterSpec generateDefaultParameter(String sigalg)

            throws RuntimeException {

        if (sigalg.regionMatches(true,

                sigalg.length() - RSA_SIG_SUFFIX.length(),

                RSA_SIG_SUFFIX, 0, RSA_SIG_SUFFIX.length())) {

            // RSA PKCS#1.5 signatures do not use parameters

            return null;

        } else if (sigalg.regionMatches(true,

                sigalg.length() - RSAPSS_SIG_SUFFIX.length(),

                RSAPSS_SIG_SUFFIX, 0, RSAPSS_SIG_SUFFIX.length())) {

            // no default parameters for RSA-PSS signature.

            // RSA-PSS signature with different PSS parameters

            // are tested under Known Answer Tests

            throw new RuntimeException("No default parameter generation for RSA-PSS");

        } else if (sigalg.regionMatches(true,

                sigalg.length() - RSAPSS_SIG_SUFFIX2.length(),

                RSAPSS_SIG_SUFFIX2, 0, RSAPSS_SIG_SUFFIX2.length())) {

            // should be the expanded/friendly name for RSA-PSS

            // use the same digest algo as in its name and its

            // output length as the salt length

            String digest = sigalg.substring(0,

                sigalg.length() - RSAPSS_SIG_SUFFIX2.length()).toUpperCase();

            if (digest.startsWith("SHA") && digest.indexOf("-") == -1) {

                // convert to standard name

                digest = "SHA-" + digest.substring(3);

            }

            // verify the digest algorithm by trying the getInstance call

            try {

                MessageDigest md = MessageDigest.getInstance(digest);

                System.out.println("Digest in PSS parameter: " + digest);

                return new PSSParameterSpec(digest, "MGF1",

                    new MGF1ParameterSpec(digest), md.getDigestLength(), 1);

            } catch (NoSuchAlgorithmException e) {

                throw new RuntimeException(e);

            }

        } else {

            throw new RuntimeException("Unsupported RSA signature " + sigalg);

        }

    }

}