Minestom/src/main/java/net/minestom/server/extras/mojangAuth/CipherBase.java

package net.minestom.server.extras.mojangAuth;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import org.jetbrains.annotations.NotNull;

import javax.crypto.Cipher;
import javax.crypto.ShortBufferException;

public class CipherBase {

    private final Cipher cipher;
    private byte[] inTempArray = new byte[0];
    private byte[] outTempArray = new byte[0];

    protected CipherBase(@NotNull Cipher cipher) {
        this.cipher = cipher;
    }

    private byte[] bufToByte(ByteBuf buffer) {
        int remainingBytes = buffer.readableBytes();

        // Need to resize temp array
        if (inTempArray.length < remainingBytes) {
            inTempArray = new byte[remainingBytes];
        }

        buffer.readBytes(inTempArray, 0, remainingBytes);
        return inTempArray;
    }

    protected ByteBuf decrypt(ChannelHandlerContext channelHandlerContext, ByteBuf byteBufIn) throws ShortBufferException {
        int remainingBytes = byteBufIn.readableBytes();
        byte[] bytes = bufToByte(byteBufIn);

        ByteBuf outputBuffer = channelHandlerContext.alloc().heapBuffer(cipher.getOutputSize(remainingBytes));
        outputBuffer.writerIndex(cipher.update(bytes, 0, remainingBytes, outputBuffer.array(), outputBuffer.arrayOffset()));

        return outputBuffer;
    }

    protected void encrypt(ByteBuf byteBufIn, ByteBuf byteBufOut) throws ShortBufferException {
        int remainingBytes = byteBufIn.readableBytes();
        byte[] bytes = bufToByte(byteBufIn);
        int newSize = cipher.getOutputSize(remainingBytes);

        // Need to resize temp array
        if (outTempArray.length < newSize) {
            outTempArray = new byte[newSize];
        }

        byteBufOut.writeBytes(outTempArray, 0, cipher.update(bytes, 0, remainingBytes, outTempArray));
    }
}