How to Ignore a Certificate Error with C# 2.0 Webclient - Without the Certificate

How to ignore a certificate error with c# 2.0 WebClient - without the certificate

The SSL certificate is for a machine to establish a trust relationship. If you type in one IP address, and end up talking to another, that sounds the same as a DNS hijack security fault, the kind of thing SSL is intending to help you avoid - and perhaps something you don't want to put up with from "them".

If you may end up talking to more than machine (ideally they would make it appear as one for you), you will need a certificate for each of the possible machines to initiate trust.

To ignore trust (I've only ever had to do this temporarily in development scenarios) the following snippet may work for you, but I strongly recommend you consider the impact of ignoring trust before using it:

public static void InitiateSSLTrust()
{
    try
    {
        //Change SSL checks so that all checks pass
        ServicePointManager.ServerCertificateValidationCallback =
           new RemoteCertificateValidationCallback(
                delegate
                { return true; }
            );
    }
    catch (Exception ex)
    {
        ActivityLog.InsertSyncActivity(ex);
    }
}

C# Ignore certificate errors?

Add a certificate validation handler. Returning true will allow ignoring the validation error:

ServicePointManager
    .ServerCertificateValidationCallback += 
    (sender, cert, chain, sslPolicyErrors) => true;

bypass invalid SSL certificate in .net core

ServicePointManager.ServerCertificateValidationCallback isn't supported in .Net Core.

Current situation is that it will be a
a new ServerCertificateCustomValidationCallback method for the upcoming 4.1.* System.Net.Http contract (HttpClient). .NET Core team are finalizing the 4.1 contract now. You can read about this in here on github

You can try out the pre-release version of System.Net.Http 4.1 by using the sources directly here in CoreFx or on the MYGET feed:
https://dotnet.myget.org/gallery/dotnet-core

Current WinHttpHandler.ServerCertificateCustomValidationCallback definition on Github

If WebClient adds a cert to request.ClientCertificates will the cert be found at context.Request.ClientCertificate in the web app?

The reason why the certificate is not showing up in the HttpContext is the certificate authentication hasn’t been established yet between the client-side and the server-side.
Simply speaking, when the web application is hosted in IIS, we disable other authentication modes in IIS and enable the IIS client certificate mapping authentication. the server requires a client certificate when the client tries to access the website/service.







Subsequently, the below function method will have a returned value.

public ActionResult About()
    {
        var result = System.Web.HttpContext.Current.Request.ClientCertificate;
        ViewBag.Message = result.Subject+result.ServerSubject;
        return View();
}

Please refer to the documentation for what is IIS Client Certificate Mapping Authentication and how to implement it in IIS.

https://learn.microsoft.com/en-us/iis/configuration/system.webserver/security/authentication/iisclientcertificatemappingauthentication/

https://learn.microsoft.com/en-us/troubleshoot/iis/configure-many-to-one-client-mappings

https://learn.microsoft.com/en-us/iis/manage/configuring-security/configuring-one-to-one-client-certificate-mappings

Feel free to let me know if there is anything I can help with.

How to ignore the certificate check when ssl

Since there is only one global ServicePointManager, setting ServicePointManager.ServerCertificateValidationCallback will yield the result that all subsequent requests will inherit this policy. Since it is a global "setting" it would be prefered to set it in the Application_Start method in Global.asax.

Setting the callback overrides the default behaviour and you can yourself create a custom validation routine.

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