Simple small OAuth flow for Epicgames new login system, 2FA support

EpicFortniteAuthFlow.cs

using System;
using System.Linq;
using System.Net;
using Newtonsoft.Json;
using RestSharp;

namespace FNFlowAuthNETCore
{
    public class EpicFortniteAuthFlow
    {
        static void Main(string[] args)
        {
            new EpicFortniteAuthFlow();
        }

        public EpicFortniteAuthFlow()
        {
            var email = "";
            var password = "";

            Console.WriteLine(GetOAuthToken(email, password));
            Console.ReadKey();
        }

        public string GetOAuthToken(string email, string password, CookieContainer cookieJar = null, string authMethod = null)
        {
            if (cookieJar == null)
                cookieJar = new CookieContainer();

            var client = new RestClient("https://www.epicgames.com/id/api/")
            {
                CookieContainer = cookieJar
            };

            var csrfRes = client.Execute(new RestRequest("csrf", Method.GET));

            var token = csrfRes.Cookies.First(x => x.Name == "XSRF-TOKEN").Value;
            var loginRequest = new RestRequest(!string.IsNullOrEmpty(authMethod) ? "login/mfa" : "login", Method.POST)
                .AddHeader("Content-Type", "application/x-www-form-urlencoded")
                .AddHeader("x-xsrf-token", token);

            if (!string.IsNullOrEmpty(authMethod))
            {
                try
                {
                    Console.Write("Two factor detected, write the 6 number code from 2FA: ");
                    var authKey = Int32.Parse(Console.ReadLine());

                    var twoStep = client.Execute(loginRequest
                        .AddParameter("code", authKey)
                        .AddParameter("method", authMethod)
                        .AddParameter("rememberDevice", false));

                    if (twoStep.StatusCode == HttpStatusCode.BadRequest)
                        return "WRONG AUTHENTICATED 2AUTH KEY";
                }
                catch (Exception)
                {
                    return "WRONG AUTHENTICATED 2AUTH KEY";
                }
            }
            else
            {
                IRestResponse loginRes = client.Execute(loginRequest
                    .AddParameter("email", email)
                    .AddParameter("password", password)
                    .AddParameter("rememberMe", true));

                if (loginRes.StatusCode == HttpStatusCode.Conflict)
                    return GetOAuthToken(email, password, cookieJar);

                if (loginRes.StatusCode == HttpStatusCode.RequestHeaderFieldsTooLarge)
                    return GetOAuthToken(email, password, cookieJar, (string) JsonConvert.DeserializeObject<dynamic>(loginRes.Content)["metadata"].twoFactorMethod);
            }

            var exchangeRes = client.Execute(
                new RestRequest("exchange", Method.POST)
                    .AddHeader("x-xsrf-token", token));

            var oauthClient = new RestClient("https://account-public-service-prod03.ol.epicgames.com/account/api/oauth/token");
            var oauthRes = oauthClient.Execute(
                new RestRequest(Method.POST)
                    .AddHeader("Content-Type", "application/x-www-form-urlencoded")
                    .AddHeader("Authorization", "basic MzQ0NmNkNzI2OTRjNGE0NDg1ZDgxYjc3YWRiYjIxNDE6OTIwOWQ0YTVlMjVhNDU3ZmI5YjA3NDg5ZDMxM2I0MWE=")
                    .AddParameter("grant_type", "exchange_code")
                    .AddParameter("exchange_code", JsonConvert.DeserializeObject<dynamic>(exchangeRes.Content)["code"])
                    .AddParameter("includePerms", true)
                    .AddParameter("token_type", "eg1"));

            return JsonConvert.DeserializeObject<dynamic>(oauthRes.Content)["access_token"];
        }

    }
}

Sorry, I am not fully sure that I understand your use-case of what you are trying to do. This is an old gist of how you did it earlier in an easy way. I am not planning to create a gist/version of what you are trying to do above.

@hamed-estsoft @iXyles

var credentials = Convert.ToBase64String(Encoding.ASCII.GetBytes(CLIENT_ID:CLIENT_SECRET));

Client_ID + CLIENT_SECRET both code are stored in binary,
but luckily I can read base64 decode and this is what it looks like:
Authorization Header is present: basic MzQ0NmNkNzI2OTRjNGE0NDg1ZDgxYjc3YWRiYjIxNDE6OTIwOWQ0YTVlMjVhNDU3ZmI5YjA3NDg5ZDMxM2I0MWE= code is above..
Decoded Username:Password= 3446cd72694c4a4485d81b77adbb2141:9209d4a5e25a457fb9b07489d313b41a

so ez..