[C#] Bypass testcookie-nginx-module bot protection

testcookie_bypass.cs

/*
  Author: Moien007
  Source: https://gist.github.com/moien007/06656aa4032c45b629a507dd4dcb6fd6
  Description:
  Bypass testcookie-nginx-module bot protection
  Web host providers like Byethost uses that module so...
*/

using System;
using System.Linq;
using System.Threading.Tasks;
using System.Security.Cryptography;
using System.Net;
using System.Net.Http;

namespace Gist
{
    class CustomWebClient
    {
        const string TestCookieSign = "aes.js";

        public static byte[] Get(string url)
        {
            var address = new Uri(url);
            var cookieContainer = new CookieContainer();
            using (var handler = new HttpClientHandler() { CookieContainer = cookieContainer })
            using (var client = new HttpClient(handler))
            {
                var content = client.GetAsync(address).WaitResult().Content;
                var script = content.ReadAsStringAsync().WaitResult();

                if (!script.Contains(TestCookieSign))
                {
                    return content.ReadAsByteArrayAsync().WaitResult();
                }

                var test = Decrypt(script);
                cookieContainer.Add(new Cookie("__test", test) { Domain = address.Host });
                
                content = client.GetAsync(address).WaitResult().Content;
                if (content.ReadAsStringAsync().WaitResult().Contains(TestCookieSign))
                {
                    throw new Exception();
                }

                return content.ReadAsByteArrayAsync().WaitResult();
            }
        }

        public static byte[] Post(string url, byte[] data)
        {
            var address = new Uri(url);
            var cookieContainer = new CookieContainer();
            using (var handler = new HttpClientHandler() { CookieContainer = cookieContainer })
            using (var client = new HttpClient(handler))
            using (var post = new ByteArrayContent(data))
            {
                var content = client.PostAsync(address, post).WaitResult().Content;
                var script = content.ReadAsStringAsync().WaitResult();

                if (!script.Contains(TestCookieSign))
                {
                    return content.ReadAsByteArrayAsync().WaitResult();
                }

                var test = Decrypt(script);
                cookieContainer.Add(new Cookie("__test", test) { Domain = address.Host });

                content = client.PostAsync(address, post).WaitResult().Content;
                if (content.ReadAsStringAsync().WaitResult().Contains(TestCookieSign))
                {
                    throw new Exception();
                }

                return content.ReadAsByteArrayAsync().WaitResult();
            }
        }

        static string Decrypt(string script)
        {
            var split = script.Split(new[] { "toNumbers(\"", "\")" }, StringSplitOptions.RemoveEmptyEntries)
                        .Where(s => s.Length == 32)
                        .ToArray();

            if (split.Length != 3)
                throw new Exception();

            var key = StringToByteArray(split[0]);
            var iv = StringToByteArray(split[1]);
            var bytesIn = StringToByteArray(split[2]);

            var aes = Aes.Create();
            aes.Padding = PaddingMode.None;
            aes.Mode = CipherMode.CBC;
            aes.BlockSize = 128;
            aes.KeySize = 128;
            aes.Key = key;
            aes.IV = iv;

            var decrypter = aes.CreateDecryptor();
            var decrypted = decrypter.TransformFinalBlock(bytesIn, 0, bytesIn.Length);

            decrypter.Dispose();
            aes.Dispose();

            return BitConverter.ToString(decrypted).Replace("-", "").ToLower();
        }

        static byte[] StringToByteArray(string hex) // Taken from https://stackoverflow.com/a/321404/9248173
        {
            return Enumerable.Range(0, hex.Length)
                             .Where(x => x % 2 == 0)
                             .Select(x => Convert.ToByte(hex.Substring(x, 2), 16))
                             .ToArray();
        }
    }

    static class ExtensionMethods
    {
        public static T WaitResult<T>(this Task<T> task)
        {
            task.Wait();
            return task.Result;
        }
    }
}