Medusa.net/Medusa.Core/Middlewares/BodyParsingMiddleware.cs

using KbinXml.Net;
using Medusa.Core.Utils;
using System.Security.Cryptography;
using System.Text;
using System.Xml.Linq;

namespace Medusa.Core.Middlewares
{
    public class BodyParsingMiddleware(RequestDelegate next)
    {
        static readonly byte[] Key =
            Convert.FromHexString("00000000000069D74627D985EE2187161570D08D93B12455035B6DF0D8205DF5");

        private readonly RequestDelegate _next = next;

        public async Task Invoke(HttpContext context)
        {
            if(context.Request.Method == "GET")
            {
                await _next(context);
                return;
            }

            var body = await ParseRequest(context);

            context.Items["Encoding"] = body.Declaration.Encoding;
            var bodyString = body.ToString();
            context.Request.Body = new MemoryStream(Encoding.GetEncoding(932).GetBytes(bodyString));

            await _next(context);
        }

        public async Task<XDocument> ParseRequest(HttpContext context)
        {
            var isCompressed = context.Request.Headers["X-Compress"].ToString().Contains("lz77");
            var info = context.Request.Headers["X-Eamuse-Info"].FirstOrDefault();
            var contentLength = context.Request.Headers.ContentLength ?? 0;
            byte[] data = new byte[(int)contentLength];
            await context.Request.Body.ReadAsync(data.AsMemory(0, (int)contentLength));

            if(info is not null)
            {
                string[] infoParts = info.Split('-');

                for(int i = 0; i < 6; i++)
                {
                    Key[i] = Convert.ToByte((infoParts[1] + infoParts[2]).Substring(i << 1, 2), 0x10);
                }

                byte[] rc4Key = MD5.HashData(Key);
                data = RC4.Decrypt(rc4Key, data);
            }

            if(isCompressed)
            {
                data = LZ77.Decompress(data);
            }

            var returnData = new XDocument();

            try
            {
                returnData = KbinConverter.ReadXmlLinq(data);
            } catch (Exception e)
            {
                Console.WriteLine(e);
            }
            //Data is now xml in konami binary form
            return returnData;
        }
    }
}