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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.

 *

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

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 */

/**

 * @test

 * @summary verify that DHKeyPairGenerator returns keys of the expected size

 * (modulus and exponent)

 * -and-

 *      DHKeyPairGenerator is using BigInteger.setBit

 * @author Andreas Sterbenz

 */

import java.math.BigInteger;

import java.util.Arrays;

import java.security.*;

import javax.crypto.*;

import javax.crypto.interfaces.*;

import javax.crypto.spec.*;

/*

 * NOTE:  BigInteger's bitlength() doesn't report leading zeros, only

 * the number of bits needed to actually represent the number.  i.e.

 *

 *     new BigInteger("4").bitLength() = 3

 *

 * Since the private key x can vary 1 <= x <= p-2, we can't do any

 * bitlength-based calculations here.  But we can check that p conforms

 * as expected.

 *

 * If not specified, we're currently using an lsize of Math.max(384, psize/2).

 */

public class TestExponentSize {

    /*

     * Sizes and values for various lengths.

     */

    private enum Sizes {

        private final int intSize;

        private final BigInteger bigIntValue;

        Sizes(int size) {

            intSize = size;

            byte [] bits = new byte[intSize/8];

            Arrays.fill(bits, (byte)0xff);

            bigIntValue = new BigInteger(1, bits);

        }

        int getIntSize() {

            return intSize;

        }

        BigInteger getBigIntValue() {

            return bigIntValue;

        }

    }

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

        KeyPair kp;

        KeyPairGenerator kpg = KeyPairGenerator.getInstance("DH", "SunJCE");

        kp = kpg.generateKeyPair();

        checkKeyPair(kp, Sizes.ten24, Sizes.five12);

        DHPublicKey publicKey = (DHPublicKey)kp.getPublic();

        BigInteger p = publicKey.getParams().getP();

        BigInteger g = publicKey.getParams().getG();

        kpg.initialize(Sizes.ten24.getIntSize());

        kp = kpg.generateKeyPair();

        checkKeyPair(kp, Sizes.ten24, Sizes.five12);

        kpg.initialize(new DHParameterSpec(p, g, Sizes.ten24.getIntSize()));

        kp = kpg.generateKeyPair();

        checkKeyPair(kp, Sizes.ten24, Sizes.ten24);

        kpg.initialize(new DHParameterSpec(p, g, Sizes.five12.getIntSize()));

        kp = kpg.generateKeyPair();

        checkKeyPair(kp, Sizes.ten24, Sizes.five12);

        kpg.initialize(new DHParameterSpec(p, g, Sizes.two56.getIntSize()));

        kp = kpg.generateKeyPair();

        checkKeyPair(kp, Sizes.ten24, Sizes.two56);

        kpg.initialize(Sizes.five12.getIntSize());

        kp = kpg.generateKeyPair();

        checkKeyPair(kp, Sizes.five12, Sizes.three84);

        kpg.initialize(Sizes.seven68.getIntSize());

        kp = kpg.generateKeyPair();

        checkKeyPair(kp, Sizes.seven68, Sizes.three84);

        System.out.println("OK");

    }

    private static void checkKeyPair(KeyPair kp, Sizes modulusSize,

            Sizes exponentSize) throws Exception {

        System.out.println("Checking (" + modulusSize + ", " +

            exponentSize + ")");

        DHPrivateKey privateKey = (DHPrivateKey)kp.getPrivate();

        BigInteger p = privateKey.getParams().getP();

        BigInteger x = privateKey.getX();

        if (p.bitLength() != modulusSize.getIntSize()) {

            throw new Exception("Invalid modulus size: " + p.bitLength());

        }

        if (x.bitLength() > exponentSize.getIntSize()) {

            throw new Exception("X has more bits than expected: " +

                x.bitLength());

        }

        BigInteger pMinus2 =

            p.subtract(BigInteger.ONE).subtract(BigInteger.ONE);

        if ((x.compareTo(BigInteger.ONE) < 0 ||

                (x.compareTo(pMinus2)) > 0)) {

            throw new Exception(

                "X outside range 1<=x<p-2:  x: " + x + " p: " + p);

        }

    }

}