obtain ssl certificate information - .net

Question

i am looking to get the data from any given domain names SSL certificate. For example I want to put in any website address e.g. "http://stackoverflow.com" and my code would firstly check if an SSL certificate exists. If it does then I want it to pull out the expiry date of the certificate. [ i am reading Domainnames from DB ] Example :http://www.digicert.com/help/

i need to create a web service to check expiry date. how can i implement it?? - I have looked up loads of different things such as RequestCertificateValidationCallback and ClientCertificates etc. Since i am new to this, i am not sure what has to be done.

I could be completely wrong (hence why I need help) but would I create a HTTPWebRequest and then somehow request the client certificate and specific elements that way?

i tried the example provided @SSL certificate pre-fetch .NET , but i am getting forbitten 403 error.

Any help would be much appreciated - Thank you.

This is the code i have written which is throwing 403 forbidden error.

        Uri u = new Uri("http://services.efi.com/");
        ServicePoint sp = ServicePointManager.FindServicePoint(u);

        string groupName = Guid.NewGuid().ToString();
        HttpWebRequest req = HttpWebRequest.Create(u) as HttpWebRequest;
        req.Accept = "*/*";
        req.ConnectionGroupName = groupName;

        using (WebResponse resp = req.GetResponse())
        {
            // Ignore response, and close the response.
        }
        sp.CloseConnectionGroup(groupName);

        // Implement favourite null check pattern here on sp.Certificate
        string expiryDate = sp.Certificate.GetExpirationDateString();

        string str = expiryDate;

Answer 1

This works fine:

namespace ConsoleApplication1
{
  using System;
  using System.Net;
  using System.Net.Security;
  using System.Security.Cryptography.X509Certificates;

  class Program
  {
    static void Main()
    {
      ServicePointManager.ServerCertificateValidationCallback += ServerCertificateValidationCallback;

      var request = WebRequest.Create("https://www.google.com");

      var response = request.GetResponse();

      Console.WriteLine("Done.");
      Console.ReadLine();

    }

    private static bool ServerCertificateValidationCallback(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
    {
      Console.WriteLine("Certificate expires on " + certificate.GetExpirationDateString());

      return true;
    }
  }
}

Answer 2

You are getting a "403 forbidden" status because that's what the server returns when you access that page. I see the same thing when I browse to that Uri using IE. This status indicates that you don't have permission to access the Url, so perhaps you should try your code on a page that you have access to.

Also, you're unlikely to see a certificate on a http connection - you might want to try https instead.