MARKUS

using NetSparkleUpdater.Interfaces;

using System;

using System.Collections.Generic;

using System.IO;

using System.Net;

using System.Net.Security;

using System.Security.Cryptography.X509Certificates;

using System.Text;

namespace NetSparkleUpdater.Downloaders

{

    /// <summary>

    /// Class that takes care of downloading data for an app cast. Allows

    /// you to send extra JSON with your request for the app cast information.

    /// </summary>

    public class WebRequestAppCastDataDownloader : IAppCastDataDownloader

    {

        private string _appcastUrl = "";

        /// <summary>

        /// Default constructor for the app cast data downloader. Basically

        /// does nothing. :)

        /// </summary>

        public WebRequestAppCastDataDownloader()

        {

        }

        /// <summary>

        /// If true, don't check the validity of SSL certificates

        /// </summary>

        public bool TrustEverySSLConnection { get; set; } = false;

        /// <summary>

        /// If not "", sends extra JSON via POST to server with the web request for update information and for the DSA signature.

        /// </summary>

        public string ExtraJsonData { get; set; } = "";

        /// <inheritdoc/>

        public string DownloadAndGetAppCastData(string url)

        {

            _appcastUrl = url;

            // configure ssl cert link

            ServicePointManager.ServerCertificateValidationCallback += ValidateRemoteCertificate;

            var response = GetWebContentResponse(url);

            if (response != null)

            {

                try

                {

                    using (StreamReader reader = new StreamReader(response.GetResponseStream(), GetAppCastEncoding()))

                    {

                        return reader.ReadToEnd();

                    }

                }

                catch

                {

                }

            }

            ServicePointManager.ServerCertificateValidationCallback -= ValidateRemoteCertificate;

            return null;

        }

        /// <inheritdoc/>

        public Encoding GetAppCastEncoding()

        {

            return Encoding.UTF8;

        }

        /// <summary>

        /// Download the app cast from the given URL.

        /// Performs a GET request by default. If ExtraJsonData is set,

        /// uses a POST request and sends the JSON data along with the

        /// request.

        /// </summary>

        /// <param name="url">the URL to download the app cast from</param>

        /// <returns>the response from the web server if creating the request

        /// succeeded; null otherwise. The response is not guaranteed to have

        /// succeeded!</returns>

        public WebResponse GetWebContentResponse(string url)

        {

            WebRequest request = WebRequest.Create(url);

            if (request != null)

            {

                if (request is FileWebRequest)

                {

                    var fileRequest = request as FileWebRequest;

                    if (fileRequest != null)

                    {

                        return request.GetResponse();

                    }

                }

                if (request is HttpWebRequest)

                {

                    HttpWebRequest httpRequest = request as HttpWebRequest;

                    httpRequest.UseDefaultCredentials = true;

                    httpRequest.Proxy.Credentials = CredentialCache.DefaultNetworkCredentials;

                    if (TrustEverySSLConnection)

                    {

                        httpRequest.ServerCertificateValidationCallback += (sender, certificate, chain, sslPolicyErrors) => true;

                    }

                    // http://stackoverflow.com/a/10027534/3938401

                    if (!string.IsNullOrWhiteSpace(ExtraJsonData))

                    {

                        httpRequest.ContentType = "application/json";

                        httpRequest.Method = "POST";

                        using (var streamWriter = new StreamWriter(httpRequest.GetRequestStream()))

                        {

                            streamWriter.Write(ExtraJsonData);

                            streamWriter.Flush();

                            streamWriter.Close();

                        }

                    }

                    // request the cast and build the stream

                    return httpRequest.GetResponse();

                }

            }

            return null;

        }

        /// <summary>

        /// Determine if the remote X509 certificate is valid

        /// </summary>

        /// <param name="sender">the web request</param>

        /// <param name="certificate">the certificate</param>

        /// <param name="chain">the chain</param>

        /// <param name="sslPolicyErrors">how to handle policy errors</param>

        /// <returns><c>true</c> if the cert is valid</returns>

        private bool ValidateRemoteCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)

        {

            if (TrustEverySSLConnection)

            {

                // verify if we talk about our app cast dll 

                if (sender is HttpWebRequest req && req.RequestUri.Equals(new Uri(_appcastUrl)))

                {

                    return true;

                }

            }

            // check our cert                 

            return sslPolicyErrors == SslPolicyErrors.None && certificate is X509Certificate2 cert2 && cert2.Verify();

        }

    }

}