How to get HTTP Response in .NET Core despite certificate error

Question

I have made a small console app in .NET Core for making REST/Http requests using .pfx/.p12 certificates during the validation process. The app works just fine when I provide it with a correct certificate with a correct password. But it crashes whenever I

• load an invalid certificate
• mistype the password associated to the certificate
• if I tell the application not to load a certificate even though a certificate is needed.

More specifically I get the following exceptions:

System.Net.Http.HttpRequestException: 'The SSL connection could not be established, see inner exception.'

AuthenticationException: Authentication failed, see inner exception.

Win32Exception: The message received was unexpected or badly formatted

I would much rather get the HTTP response corresponding to an invalid invocation, which seems to be what I get when I use SOAPUI.

I use the following method for making a HttpClientHandler:

private static HttpClientHandler GetClientHandler(string certificate, string password)
{
    
    X509Certificate2 certPfx;

    try {
        certPfx = new X509Certificate2(certificate, password);
    }
    catch(CryptographicException e) {
        Console.WriteLine($ "Error occured while trying to load certificate: {e.Message}");
        return null;
    }

    var clientHandler = new HttpClientHandler();
    clientHandler.SslProtocols = SslProtocols.Tls12;
    clientHandler.ClientCertificateOptions = ClientCertificateOption.Manual;
    clientHandler.ClientCertificates.Add(certPfx);
    clientHandler.ServerCertificateCustomValidationCallback += (HttpRequestMessage req, X509Certificate2 cert2, X509Chain chain, SslPolicyErrors err) = >true;
    return clientHandler;
}

And I use the following code for making the POST request:

using(var client = handler != null ? new HttpClient(handler, true) : new HttpClient())
{
    
    AddHeaders(client, headers);

    var httpContent = new StringContent(request.ToString(), Encoding.UTF8, "application/xml");

    Console.WriteLine("Response from service:");
    Console.WriteLine("----------------------");
    var response = await client.PostAsync(endpoint, httpContent);

    var responseString = await response.Content.ReadAsStringAsync();

    Console.WriteLine(responseString);
    Console.WriteLine("----------------------");
    Console.WriteLine("----------------------");
}