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

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

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 * 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

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 * accompanied this code).

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package com.sun.crypto.provider;

import java.io.IOException;

import java.security.AlgorithmParametersSpi;

import java.security.spec.AlgorithmParameterSpec;

import java.security.spec.InvalidParameterSpecException;

import javax.crypto.spec.IvParameterSpec;

import sun.security.util.*;

/**

 * This class implements the parameter set used with the ChaCha20-Poly1305

 * algorithm.  The parameter definition comes from

 * <a href="https://tools.ietf.org/html/rfc8103"><i>RFC 8103</i></a>

 * and is defined according to the following ASN.1:

 *

 * <pre>

 * id-alg-AEADChaCha20Poly1305 OBJECT IDENTIFIER ::=

 *        { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)

 *          pkcs9(9) smime(16) alg(3) 18 }

 *

 * AEADChaCha20Poly1305Nonce ::= OCTET STRING (SIZE(12))

 * </pre>

 *

 * The AlgorithmParameters may be instantiated either by its name

 * ("ChaCha20-Poly1305") or via its OID (1.2.840.113549.1.9.16.3.18)

 */

public final class ChaCha20Poly1305Parameters extends AlgorithmParametersSpi {

    private static final String DEFAULT_FMT = "ASN.1";

    private byte[] nonce;

    public ChaCha20Poly1305Parameters() {}

    /**

     * Initialize the ChaCha20Poly1305Parameters using an IvParameterSpec.

     *

     * @param paramSpec the {@code IvParameterSpec} used to configure

     *      this object.

     *

     * @throws InvalidParameterSpecException if an object of a type other

     *      than {@code IvParameterSpec} is used.

     */

    @Override

    protected void engineInit(AlgorithmParameterSpec paramSpec)

        throws InvalidParameterSpecException {

        if (!(paramSpec instanceof IvParameterSpec)) {

            throw new InvalidParameterSpecException

                ("Inappropriate parameter specification");

        }

        IvParameterSpec ivps = (IvParameterSpec)paramSpec;

        // Obtain the nonce

        nonce = ivps.getIV();

        if (nonce.length != 12) {

            throw new InvalidParameterSpecException("ChaCha20-Poly1305 nonce" +

                    " must be 12 bytes in length");

        }

    }

    /**

     * Initialize the ChaCha20Poly1305Parameters from a DER encoded

     * parameter block.

     *

     * @param encoded the DER encoding of the nonce as an OCTET STRING.

     *

     * @throws IOException if the encoded nonce is not 12 bytes long or a DER

     *      decoding error occurs.

     */

    @Override

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

        DerValue val = new DerValue(encoded);

        // Get the nonce value

        nonce = val.getOctetString();

        if (nonce.length != 12) {

           throw new IOException(

                   "ChaCha20-Poly1305 nonce must be 12 bytes in length");

        }

    }

    /**

     * Initialize the ChaCha20Poly1305Parameters from a DER encoded

     * parameter block.

     *

     * @param encoded the DER encoding of the nonce and initial block counter.

     * @param decodingMethod the decoding method.  The only currently accepted

     *      value is "ASN.1"

     *

     * @throws IOException if the encoded nonce is not 12 bytes long, a DER

     *      decoding error occurs, or an unsupported decoding method is

     *      provided.

     */

    @Override

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

            throws IOException {

        if (decodingMethod == null ||

                decodingMethod.equalsIgnoreCase(DEFAULT_FMT)) {

            engineInit(encoded);

        } else {

            throw new IOException("Unsupported parameter format: " +

                    decodingMethod);

        }

    }

    /**

     * Return an IvParameterSpec with the same parameters as those

     * held in this object.

     *

     * @param paramSpec the class name of the spec.  In this case it should

     *      be {@code IvParameterSpec.class}.

     *

     * @return a {@code IvParameterSpec} object containing the nonce

     *      value held in this object.

     *

     * @throws InvalidParameterSpecException if a class other than

     *      {@code IvParameterSpec.class} was specified in the paramSpec

     *      parameter.

     */

    @Override

    protected <T extends AlgorithmParameterSpec>

            T engineGetParameterSpec(Class<T> paramSpec)

        throws InvalidParameterSpecException {

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

            return paramSpec.cast(new IvParameterSpec(nonce));

        } else {

            throw new InvalidParameterSpecException

                ("Inappropriate parameter specification");

        }

    }

    /**

     * Return the encoded parameters in ASN.1 form.

     *

     * @return a byte array containing the DER-encoding for the

     *      ChaCha20-Poly1305 parameters.  This will be the nonce

     *      encoded as a DER OCTET STRING.

     *

     * @throws IOException if any DER encoding error occurs.

     */

    @Override

    protected byte[] engineGetEncoded() throws IOException {

        DerOutputStream out = new DerOutputStream();

        out.write(DerValue.tag_OctetString, nonce);

        return out.toByteArray();

    }

    /**

     * Return the encoded parameters in ASN.1 form.

     *

     * @param encodingMethod the encoding method to be used.  This parameter

     *      must be "ASN.1" as it is the only currently supported encoding

     *      format.  If the parameter is {@code null} then the default

     *      encoding format will be used.

     *

     * @return a byte array containing the DER-encoding for the

     *      ChaCha20-Poly1305 parameters.

     *

     * @throws IOException if any DER encoding error occurs or an unsupported

     *      encoding method is provided.

     */

    @Override

    protected byte[] engineGetEncoded(String encodingMethod)

        throws IOException {

        if (encodingMethod == null ||

                encodingMethod.equalsIgnoreCase(DEFAULT_FMT)) {

            return engineGetEncoded();

        } else {

            throw new IOException("Unsupported encoding format: " +

                    encodingMethod);

        }

    }

    /**

     * Creates a formatted string describing the parameters.

     *

     * @return a string representation of the ChaCha20 parameters.

     */

    @Override

    protected String engineToString() {

        String LINE_SEP = System.lineSeparator();

        HexDumpEncoder encoder = new HexDumpEncoder();

        StringBuilder sb = new StringBuilder(LINE_SEP + "nonce:" +

                LINE_SEP + "[" + encoder.encodeBuffer(nonce) + "]");

        return sb.toString();

    }

}