c# - Ignore bad certificate - .NET CORE

Question

I'm writing a .NET Core app to poll a remote server and transfer data as it appears. This is working perfectly in PHP because the PHP is ignoring the certificate (which is also a problem in browsers) but we want to move this to C# .NET CORE because this is the only remaining PHP in the system.

We know the server is good, but for various reasons the certificate can't / won't be updated any time soon.

The request is using HttpClient:

        HttpClient httpClient = new HttpClient();
        try
        {
            string url = "https://URLGoesHere.php";
            MyData md = new MyData();  // this is some data we need to pass as a json
            string postBody = JsonConvert.SerializeObject(md);
            httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));                
            HttpResponseMessage wcfResponse = await httpClient.PostAsync(url, new StringContent(postBody, Encoding.UTF8, "application/json"));
            Console.WriteLine(wcfResponse.Content);
        }
        catch (HttpRequestException hre)
        {
        // This exception is being triggered
        }

Having researched this it seems the universal recommendation is to use ServicePointManager, but this is not available in .NET Core and I'm having trouble finding the recommended replacement.

Is there a simple or better way to do this in .NET Core?

Answer 1

Instead of new HttpClient() you want something akin to

var handler = new System.Net.Http.HttpClientHandler();
using (var httpClient = new System.Net.Http.HttpClient(handler))
{
    handler.ServerCertificateCustomValidationCallback = (request, cert, chain, errors) =>
    {
        // Log it, then use the same answer it would have had if we didn't make a callback.
        Console.WriteLine(cert);
        return errors == SslPolicyErrors.None;
    };

    ...
}

That should work on Windows, and on Linux where libcurl is compiled to use openssl. With other curl backends Linux will throw an exception.