/*

 * Copyright (c) 1997, 2011, 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.

 */

package com.sun.crypto.provider;

import java.io.*;

import sun.security.util.*;

import java.math.BigInteger;

import java.security.AlgorithmParametersSpi;

import java.security.spec.AlgorithmParameterSpec;

import java.security.spec.InvalidParameterSpecException;

import javax.crypto.spec.DHParameterSpec;

/**

 * This class implements the parameter set used by the

 * Diffie-Hellman key agreement as defined in the PKCS #3 standard.

 *

 * @author Jan Luehe

 *

 */

public final class DHParameters extends AlgorithmParametersSpi {

    // The prime (p).

    private BigInteger p = BigInteger.ZERO;

    // The base (g).

    private BigInteger g = BigInteger.ZERO;

    // The private-value length (l)

    private int l = 0;

    protected void engineInit(AlgorithmParameterSpec paramSpec)

        throws InvalidParameterSpecException {

            if (!(paramSpec instanceof DHParameterSpec)) {

                throw new InvalidParameterSpecException

                    ("Inappropriate parameter specification");

            }

            this.p = ((DHParameterSpec)paramSpec).getP();

            this.g = ((DHParameterSpec)paramSpec).getG();

            this.l = ((DHParameterSpec)paramSpec).getL();

    }

    protected void engineInit(byte[] params) throws IOException {

        try {

            DerValue encodedParams = new DerValue(params);

            if (encodedParams.tag != DerValue.tag_Sequence) {

                throw new IOException("DH params parsing error");

            }

            encodedParams.data.reset();

            this.p = encodedParams.data.getBigInteger();

            this.g = encodedParams.data.getBigInteger();

            // Private-value length is OPTIONAL

            if (encodedParams.data.available() != 0) {

                this.l = encodedParams.data.getInteger();

            }

            if (encodedParams.data.available() != 0) {

                throw new IOException

                    ("DH parameter parsing error: Extra data");

            }

        } catch (NumberFormatException e) {

            throw new IOException("Private-value length too big");

        }

    }

    protected void engineInit(byte[] params, String decodingMethod)

        throws IOException {

            engineInit(params);

    }

    protected <T extends AlgorithmParameterSpec>

        T engineGetParameterSpec(Class<T> paramSpec)

        throws InvalidParameterSpecException {

        if (DHParameterSpec.class.isAssignableFrom(paramSpec)) {

            return paramSpec.cast(new DHParameterSpec(this.p, this.g, this.l));

        } else {

            throw new InvalidParameterSpecException

                ("Inappropriate parameter Specification");

        }

    }

    protected byte[] engineGetEncoded() throws IOException {

        DerOutputStream out = new DerOutputStream();

        DerOutputStream bytes = new DerOutputStream();

        bytes.putInteger(this.p);

        bytes.putInteger(this.g);

        // Private-value length is OPTIONAL

        if (this.l > 0) {

            bytes.putInteger(this.l);

        }

        out.write(DerValue.tag_Sequence, bytes);

        return out.toByteArray();

    }

    protected byte[] engineGetEncoded(String encodingMethod)

        throws IOException {

            return engineGetEncoded();

    }

    /*

     * Returns a formatted string describing the parameters.

     */

    protected String engineToString() {

        String LINE_SEP = System.getProperty("line.separator");

        StringBuffer strbuf

            = new StringBuffer("SunJCE Diffie-Hellman Parameters:"

                               + LINE_SEP + "p:" + LINE_SEP

                               + Debug.toHexString(this.p)

                               + LINE_SEP + "g:" + LINE_SEP

                               + Debug.toHexString(this.g));

        if (this.l != 0)

            strbuf.append(LINE_SEP + "l:" + LINE_SEP + "    " + this.l);

        return strbuf.toString();

    }

}