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

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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

 * 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,

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package com.sun.crypto.provider;

import java.util.Arrays;

import java.nio.ByteBuffer;

import javax.crypto.MacSpi;

import javax.crypto.SecretKey;

import java.security.*;

import java.security.spec.*;

/**

 * This class constitutes the core of HMAC-<MD> algorithms, where

 * <MD> can be SHA1 or MD5, etc. See RFC 2104 for spec.

 *

 * It also contains the implementation classes for SHA-224, SHA-256,

 * SHA-384, and SHA-512 HMACs.

 *

 * @author Jan Luehe

 */

abstract class HmacCore extends MacSpi implements Cloneable {

    private MessageDigest md;

    private byte[] k_ipad; // inner padding - key XORd with ipad

    private byte[] k_opad; // outer padding - key XORd with opad

    private boolean first;       // Is this the first data to be processed?

    private final int blockLen;

    /**

     * Standard constructor, creates a new HmacCore instance using the

     * specified MessageDigest object.

     */

    HmacCore(MessageDigest md, int bl) {

        this.md = md;

        this.blockLen = bl;

        this.k_ipad = new byte[blockLen];

        this.k_opad = new byte[blockLen];

        first = true;

    }

    /**

     * Standard constructor, creates a new HmacCore instance instantiating

     * a MessageDigest of the specified name.

     */

    HmacCore(String digestAlgorithm, int bl) throws NoSuchAlgorithmException {

        this(MessageDigest.getInstance(digestAlgorithm), bl);

    }

    /**

     * Returns the length of the HMAC in bytes.

     *

     * @return the HMAC length in bytes.

     */

    protected int engineGetMacLength() {

        return this.md.getDigestLength();

    }

    /**

     * Initializes the HMAC with the given secret key and algorithm parameters.

     *

     * @param key the secret key.

     * @param params the algorithm parameters.

     *

     * @exception InvalidKeyException if the given key is inappropriate for

     * initializing this MAC.

     * @exception InvalidAlgorithmParameterException if the given algorithm

     * parameters are inappropriate for this MAC.

     */

    protected void engineInit(Key key, AlgorithmParameterSpec params)

            throws InvalidKeyException, InvalidAlgorithmParameterException {

        if (params != null) {

            throw new InvalidAlgorithmParameterException

                ("HMAC does not use parameters");

        }

        if (!(key instanceof SecretKey)) {

            throw new InvalidKeyException("Secret key expected");

        }

        byte[] secret = key.getEncoded();

        if (secret == null) {

            throw new InvalidKeyException("Missing key data");

        }

        // if key is longer than the block length, reset it using

        // the message digest object.

        if (secret.length > blockLen) {

            byte[] tmp = md.digest(secret);

            // now erase the secret

            Arrays.fill(secret, (byte)0);

            secret = tmp;

        }

        // XOR k with ipad and opad, respectively

        for (int i = 0; i < blockLen; i++) {

            int si = (i < secret.length) ? secret[i] : 0;

            k_ipad[i] = (byte)(si ^ 0x36);

            k_opad[i] = (byte)(si ^ 0x5c);

        }

        // now erase the secret

        Arrays.fill(secret, (byte)0);

        secret = null;

        engineReset();

    }

    /**

     * Processes the given byte.

     *

     * @param input the input byte to be processed.

     */

    protected void engineUpdate(byte input) {

        if (first == true) {

            // compute digest for 1st pass; start with inner pad

            md.update(k_ipad);

            first = false;

        }

        // add the passed byte to the inner digest

        md.update(input);

    }

    /**

     * Processes the first <code>len</code> bytes in <code>input</code>,

     * starting at <code>offset</code>.

     *

     * @param input the input buffer.

     * @param offset the offset in <code>input</code> where the input starts.

     * @param len the number of bytes to process.

     */

    protected void engineUpdate(byte input[], int offset, int len) {

        if (first == true) {

            // compute digest for 1st pass; start with inner pad

            md.update(k_ipad);

            first = false;

        }

        // add the selected part of an array of bytes to the inner digest

        md.update(input, offset, len);

    }

    /**

     * Processes the <code>input.remaining()</code> bytes in the ByteBuffer

     * <code>input</code>.

     *

     * @param input the input byte buffer.

     */

    protected void engineUpdate(ByteBuffer input) {

        if (first == true) {

            // compute digest for 1st pass; start with inner pad

            md.update(k_ipad);

            first = false;

        }

        md.update(input);

    }

    /**

     * Completes the HMAC computation and resets the HMAC for further use,

     * maintaining the secret key that the HMAC was initialized with.

     *

     * @return the HMAC result.

     */

    protected byte[] engineDoFinal() {

        if (first == true) {

            // compute digest for 1st pass; start with inner pad

            md.update(k_ipad);

        } else {

            first = true;

        }

        try {

            // finish the inner digest

            byte[] tmp = md.digest();

            // compute digest for 2nd pass; start with outer pad

            md.update(k_opad);

            // add result of 1st hash

            md.update(tmp);

            md.digest(tmp, 0, tmp.length);

            return tmp;

        } catch (DigestException e) {

            // should never occur

            throw new ProviderException(e);

        }

    }

    /**

     * Resets the HMAC for further use, maintaining the secret key that the

     * HMAC was initialized with.

     */

    protected void engineReset() {

        if (first == false) {

            md.reset();

            first = true;

        }

    }

    /*

     * Clones this object.

     */

    public Object clone() throws CloneNotSupportedException {

        HmacCore copy = (HmacCore) super.clone();

        copy.md = (MessageDigest) md.clone();

        copy.k_ipad = k_ipad.clone();

        copy.k_opad = k_opad.clone();

        return copy;

    }

    // nested static class for the HmacSHA224 implementation

    public static final class HmacSHA224 extends HmacCore {

        public HmacSHA224() throws NoSuchAlgorithmException {

            super("SHA-224", 64);

        }

    }

    // nested static class for the HmacSHA256 implementation

    public static final class HmacSHA256 extends HmacCore {

        public HmacSHA256() throws NoSuchAlgorithmException {

            super("SHA-256", 64);

        }

    }

    // nested static class for the HmacSHA384 implementation

    public static final class HmacSHA384 extends HmacCore {

        public HmacSHA384() throws NoSuchAlgorithmException {

            super("SHA-384", 128);

        }

    }

    // nested static class for the HmacSHA512 implementation

    public static final class HmacSHA512 extends HmacCore {

        public HmacSHA512() throws NoSuchAlgorithmException {

            super("SHA-512", 128);

        }

    }

}