DataSigner.java

package org.heat.dofus.network;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import org.fungsi.Try;
import org.heat.dofus.network.netty.NettyDataReader;
import org.heat.dofus.network.netty.NettyDataWriter;
import org.heat.shared.Md5;
import org.heat.shared.RsaHandler;

import java.security.SecureRandom;

/**
 * Author: romain
 * Date: 23/10/2017
 */
public class DataSigner {
    private final SecureRandom generator;
    private final RsaHandler rsa;

    private static final String ANKAMA_HEADER = "ASKF";
    private static final String SIGN_HEADER = "AKSD";

    public DataSigner(String privateKey) {
        this.rsa = Try
                .of(() -> new RsaHandler(null, privateKey, RsaHandler.RSA_PKCS1_PADDING))
                .getOrThrow();
        this.generator = new SecureRandom();
    }

    public ByteBuf sign(ByteBuf data, boolean includeData) throws Exception {
        NettyDataReader reader = NettyDataReader.of(data);
        NettyDataWriter writer = NettyDataWriter.of(Unpooled.buffer());


        byte random = (byte) generator.nextInt(8);

        NettyDataWriter hash = NettyDataWriter.of(Unpooled.buffer());
        hash.writeInt8(random);
        hash.writeUInt16(data.readableBytes());
        hash.writeUTFBytes(Md5.hash(reader.readUTF(data.readableBytes()).getBytes()));

        byte[] array = hash.getUnderlyingBuf().array();
        for (int i = 2; i < array.length; i++)
            array[i] = (byte) (array[i] ^ random);

        hash.setPosition(0);
        byte[] ciphered = rsa.encrypt(hash.getUnderlyingBuf().array(), true);
        writer.writeUTFBytes(ANKAMA_HEADER);
        writer.writeInt16((short) 1);
        writer.writeInt32(ciphered.length);
        writer.writeBytes(ciphered);

        if (includeData)
            writer.writeBytes(data.array());

        return writer.getUnderlyingBuf();
    }
}