Arakne / ArakneUtils

 * This file is part of ArakneUtils.

 *

 * ArakneUtils is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * ArakneUtils 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 Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with ArakneUtils.  If not, see <https://www.gnu.org/licenses/>.

 *

 * Copyright (c) 2017-2020 Vincent Quatrevieux

 */

package fr.arakne.utils.encoding;

import java.io.UnsupportedEncodingException;

import java.net.URLDecoder;

import java.net.URLEncoder;

import java.nio.charset.StandardCharsets;

import java.security.SecureRandom;

/**

 * Handle key for Dofus packets

 */

final public class Key {

    static private SecureRandom random;

    private XorCipher cipher;

    public Key(String key) {

        this.key = key;

    }

    @Override

    public String toString() {

        return key;

    }

    /**

     * Get the cipher related to this key

     * The cipher instance is saved into the key

     *

     * @return The cipher instance

     */

    public XorCipher cipher() {

        if (cipher == null) {

            cipher = new XorCipher(key);

        }

        return cipher;

    }

    /**

     * Encode the key to hexadecimal string

     *

     * @return The encoded key

     * @see Key#parse(String) For parse the encoded key

     */

    public String encode() {

        final String raw;

        try {

            raw = URLEncoder.encode(key, StandardCharsets.UTF_8.toString());

        } catch (UnsupportedEncodingException e) {

            throw new IllegalStateException("Invalid UTF-8 key", e);

        }

        StringBuilder encrypted = new StringBuilder(raw.length() * 2);

        for (int i = 0; i < raw.length(); ++i) {

            final char c = raw.charAt(i);

            if (c < 16) {

                encrypted.append('0');

            }

            encrypted.append(Integer.toHexString(c));

        }

        return encrypted.toString();

    }

    /**

     * Parse an hexadecimal key string

     *

     * https://github.com/Emudofus/Dofus/blob/1.29/dofus/aks/Aks.as#L232

     *

     * @param input Key to parse

     *

     * @return The key instance

     *

     * @throws IllegalArgumentException When invalid key is given

     * @throws NumberFormatException When invalid hexadecimal string is given

     *

     * @see Key#encode() For generate the hexadecimal string

     */

    static public Key parse(String input) {

        if (input.length() % 2 != 0) {

            throw new IllegalArgumentException("Invalid key");

        }

        final char[] keyArr = new char[input.length() / 2];

        for (int i = 0; i < input.length(); i += 2) {

            keyArr[i / 2] = (char) Integer.parseInt(input.substring(i, i + 2), 16);

        }

        try {

            return new Key(URLDecoder.decode(new String(keyArr), StandardCharsets.UTF_8.toString()));

        } catch (UnsupportedEncodingException e) {

            throw new IllegalArgumentException("Invalid UTF-8 character");

        }

    }

    /**

     * Generate a new random key, with length of 128 characters

     * The generated key contains only displayable characters

     *

     * @return The generated key

     */

    /**

     * Generate a new random key

     * The generated key contains only displayable characters

     *

     * @param size The key size

     *

     * @return The generated key

     */

    static public Key generate(int size) {

        if (random == null) {

            random = new SecureRandom();

        }

        return generate(size, random);

    }

    /**

     * Generate a new random key

     * The generated key contains only displayable characters

     *

     * @param size The key size

     * @param random The random number generator

     *

     * @return The generated key

     */

    static public Key generate(int size, SecureRandom random) {

        final char[] keyArr = new char[size];

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

            keyArr[i] = (char) (random.nextInt(127 - 32) + 32);

        }

        return new Key(new String(keyArr));

    }

}