using System;

using System.Net;

using System.Net.Security;

using System.Security.Cryptography.X509Certificates;

using System.Linq;

using System.Collections;

using System.Collections.Generic;

using System.Net.Sockets;

​

public class Program

{

    public static void Main(string[] args)

    {

        // Valid Chain

        Connect("www.google.com");

        // Invalid Chain

        Connect("incomplete-chain.badssl.com");

    }

​

    private static void Connect(string url)

    {

        try

        {

            new SslStream(new TcpClient(url, 443).GetStream(), false,

            new RemoteCertificateValidationCallback(ServerCertificateValidationCallback))

            .AuthenticateAsClient(url);

        }

        catch { }

    }

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

    {

        if (sslPolicyErrors != SslPolicyErrors.None)

        {

            return false;

        }

​

        var certs = chain.ChainPolicy.ExtraStore;

​

        Console.WriteLine("Certificate Subjects:");

        foreach (var x in certs)

        {

            Console.WriteLine(x.Subject);

        }

​

        // Add root certificate

        var store = GetRootCertificates().Select(x => x.Subject).ToList();

​

        // Assert each parent's subject is the child's issuer

        var result = false;

​

        for (var i = certs.Count - 1; i >= 0; i--)

        {

            if (i > 0)

            {

                if (certs[i].Issuer != certs[i - 1].Subject)

                {

                    result = false;

                    break;

                }

            }

​

            if (store.Contains(certs[i].Issuer))

            {

                result = true;

                break;

            }

        }

​

        // This is True and I want it to be False

        Console.WriteLine($"This chain is {(result ? "" : "not ")}valid");

        Console.WriteLine();

​

        return result;

    }

    private static List<X509Certificate2> GetRootCertificates()

    {

       var certificates = new List<X509Certificate2>();

​

        var stores = new[]

        {

            new X509Store(StoreName.Root, StoreLocation.LocalMachine),

            new X509Store(StoreName.Root, StoreLocation.CurrentUser)

        };

​

        var certCollection = new X509Certificate2Collection();

        foreach (var store in stores)

        {

            try

            {

                store.Open(OpenFlags.ReadOnly);

​

                foreach (X509Certificate2 x509 in store.Certificates)

                {

                    certificates.Add(x509);

                }

            }

            finally

            {

                store.Close();

            }

        }

​

        return certificates;

    }

}