/*

 * Copyright (c) 2013, 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.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.GCMParameterSpec;

import sun.misc.HexDumpEncoder;

import sun.security.util.*;

/**

 * This class implements the parameter set used with

 * GCM encryption, which is defined in RFC 5084 as follows:

 *

 * <pre>

 *    GCMParameters ::= SEQUENCE {

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

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

 *

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

 *

 * </pre>

 *

 * @author Valerie Peng

 * @since 1.8

 */

public final class GCMParameters extends AlgorithmParametersSpi {

    // the iv

    private byte[] iv;

    // the tag length in bytes

    private int tLen;

    public GCMParameters() {}

    protected void engineInit(AlgorithmParameterSpec paramSpec)

        throws InvalidParameterSpecException {

        if (!(paramSpec instanceof GCMParameterSpec)) {

            throw new InvalidParameterSpecException

                ("Inappropriate parameter specification");

        }

        GCMParameterSpec gps = (GCMParameterSpec) paramSpec;

        // need to convert from bits to bytes for ASN.1 encoding

        this.tLen = gps.getTLen()/8;

        this.iv = gps.getIV();

    }

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

        DerValue val = new DerValue(encoded);

        // check if IV or params

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

            byte[] iv = val.data.getOctetString();

            int tLen;

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

                tLen = val.data.getInteger();

                if (tLen < 12 || tLen > 16 ) {

                    throw new IOException

                        ("GCM parameter parsing error: unsupported tag len: " +

                         tLen);

                }

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

                    throw new IOException

                        ("GCM parameter parsing error: extra data");

                }

            } else {

                tLen = 12;

            }

            this.iv = iv.clone();

            this.tLen = tLen;

        } else {

            throw new IOException("GCM parameter parsing error: no SEQ tag");

        }

    }

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

        throws IOException {

        engineInit(encoded);

    }

    protected <T extends AlgorithmParameterSpec>

            T engineGetParameterSpec(Class<T> paramSpec)

        throws InvalidParameterSpecException {

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

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

        } else {

            throw new InvalidParameterSpecException

                ("Inappropriate parameter specification");

        }

    }

    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 encodingMethod)

        throws IOException {

        return engineGetEncoded();

    }

    /*

     * Returns a formatted string describing the parameters.

     */

    protected String engineToString() {

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

        HexDumpEncoder encoder = new HexDumpEncoder();

        StringBuilder sb

            = new StringBuilder(LINE_SEP + "    iv:" + LINE_SEP + "["

                + encoder.encodeBuffer(iv) + "]");

        sb.append(LINE_SEP + "tLen(bits):" + LINE_SEP + tLen*8 + LINE_SEP);

        return sb.toString();

    }

}