/*

 * Copyright (c) 2014, 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

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package com.oracle.security.ucrypto;

import java.io.IOException;

import java.util.Arrays;

import java.security.AlgorithmParametersSpi;

import java.security.spec.AlgorithmParameterSpec;

import java.security.spec.InvalidParameterSpecException;

import javax.crypto.spec.GCMParameterSpec;

import sun.security.util.*;

/**

 * This class implements the parameter set used with GCM mode

 * which is defined in RFC5084 as follows:

 *

 * <pre>

 * GCMParameters ::= SEQUENCE {

 *   aes-nonce        OCTET STRING, -- recommended size is 12 octets

 *   aes-ICVlen       AES-GCM-ICVlen DEFAULT 12 }

 *

 * where

 * AES-GCM-ICVlen ::= INTEGER (12 | 13 | 14 | 15 | 16)

 * NOTE: however, NIST 800-38D also lists 4 (32bit) and 8 (64bit)

 * as possible AES-GCM-ICVlen values, so we allow all 6 values.

 * </pre>

 *

 */

public final class GCMParameters extends AlgorithmParametersSpi {

    private byte[] iv; // i.e. aes-nonce

    private int tLen; // i.e. aes-ICVlen, in bytes

    public GCMParameters() {}

    private void setValues(byte[] iv, int tLen) throws IOException {

        if (iv == null) {

            throw new IOException("IV cannot be null");

        }

        if (tLen != 4 && tLen != 8 && (tLen < 12 || tLen > 16)) {

            throw new IOException("Unsupported tag length: " + tLen);

        }

        this.iv = iv;

        this.tLen = tLen;

    }

    protected byte[] engineGetEncoded() throws IOException {

        DerOutputStream out = new DerOutputStream();

        DerOutputStream bytes = new DerOutputStream();

        bytes.putOctetString(iv);

        bytes.putInteger(tLen);

        out.write(DerValue.tag_Sequence, bytes);

        return out.toByteArray();

    }

    protected byte[] engineGetEncoded(String format) throws IOException {

        // ignore format for now

        return engineGetEncoded();

    }

    protected <T extends AlgorithmParameterSpec>

            T engineGetParameterSpec(Class<T> paramSpec)

        throws InvalidParameterSpecException {

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

            return paramSpec.cast(new GCMParameterSpec(tLen*8, iv.clone()));

        } else {

            throw new InvalidParameterSpecException

                ("Inappropriate parameter specification. Received " +

                paramSpec.getClass().getName());

        }

    }

    protected void engineInit(AlgorithmParameterSpec paramSpec)

        throws InvalidParameterSpecException {

        if (!(paramSpec instanceof GCMParameterSpec)) {

            throw new InvalidParameterSpecException

                ("Inappropriate parameter specification. Received " +

                paramSpec.getClass().getName());

        }

        GCMParameterSpec gcmSpec = (GCMParameterSpec) paramSpec;

        try {

            setValues(gcmSpec.getIV(), gcmSpec.getTLen()/8);

        } catch (IOException ioe) {

            throw new InvalidParameterSpecException(ioe.getMessage());

        }

    }

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

        DerValue val = new DerValue(encoded);

        if (val.tag == DerValue.tag_Sequence) {

            val.data.reset();

            setValues(val.data.getOctetString(), val.data.getInteger());

        } else {

            throw new IOException("GCM parameter parsing error: SEQ tag expected." +

                " Received: " + val.tag);

        }

    }

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

        throws IOException {

        // ignore format for now

        engineInit(encoded);

    }

    protected String engineToString() {

        return ("IV=" + Arrays.toString(iv) + ", tLen=" + tLen * 8);

    }

}