yegor256/takes

/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2014-2024 Yegor Bugayenko
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package org.takes.facets.auth.codecs;

import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import javax.crypto.Mac;
import org.takes.facets.auth.Identity;

/**
 * MAC codec which sign identity with provided algorithm and key.
 * @since 1.11.1
 */
public final class CcSigned implements Codec {
    /**
     * Origin codec.
     */
    private final Codec cdc;

    /**
     * MAC algorithm.
     */
    private final String alg;

    /**
     * Secret key.
     */
    private final Key key;

    /**
     * Ctor.
     * @param origin Origin codec
     * @param algorithm Algorithm name
     * @param secret Secret key
     */
    public CcSigned(
        final Codec origin,
        final String algorithm,
        final Key secret
    ) {
        this.cdc = origin;
        this.alg = algorithm;
        this.key = secret;
    }

    @Override
    public byte[] encode(final Identity identity) throws IOException {
        final byte[] encoded = this.cdc.encode(identity);
        final byte[] signature = this.mac().doFinal(encoded);
        final byte[] signed = new byte[encoded.length + signature.length];
        System.arraycopy(encoded, 0, signed, 0, encoded.length);
        System.arraycopy(
            signature,
            0,
            signed,
            encoded.length,
            signature.length
        );
        return signed;
    }

    @Override
    public Identity decode(final byte[] bytes) throws IOException {
        final Mac mac = this.mac();
        if (bytes.length < mac.getMacLength()) {
            throw new IOException("Invalid data size");
        }
        final byte[] signature = new byte[mac.getMacLength()];
        final byte[] encoded = new byte[bytes.length - signature.length];
        System.arraycopy(bytes, 0, encoded, 0, encoded.length);
        System.arraycopy(
            bytes,
            encoded.length,
            signature,
            0,
            signature.length
        );
        final byte[] actual = mac.doFinal(encoded);
        if (!Arrays.equals(actual, signature)) {
            throw new IOException("Bad signature");
        }
        return this.cdc.decode(encoded);
    }

    /**
     * Obtain MAC instance.
     * @return Initialized MAC
     * @throws IOException If algorithm missed or invalid key
     */
    private Mac mac() throws IOException {
        try {
            final Mac mac = Mac.getInstance(this.alg);
            mac.init(this.key);
            return mac;
        } catch (final NoSuchAlgorithmException | InvalidKeyException err) {
            throw new IOException(err);
        }
    }
}