Xamarin .Net Core HttpClientHandler Method Not Implemented(VS for Mac) - xamarin

Question

I am writing a .net core(Standard 1.6) library that connects to my WebAPI. The WebApi requires a client certificate.
The .net core library is something being called from a Xamarin iOS app.
I cannot for the life of me send an HTTP request with a Client Certificate header.
I can use the library and post to the API with a client certificate from Visual Studio 2017 on a windows machine.
When I move the same project into my Xamarin iOS app using VS for Mac I get:
"Method Not Implemented" when setting the SslProtocol or adding the client certificate:
var handler = new HttpClientHandler();
handler.ClientCertificateOptions = ClientCertificateOption.Manual;
handler.SslProtocols = SslProtocols.Tls12;
handler.ClientCertificates.Add(new X509Certificate2(certificate));
Relevant libraries:
using System.Net;
using System.Net.Http;
using System.Security;
using System.Security.Cryptography.X509Certificates;
Any help would be greatly appreciated.

Answer 1

Alright, this took me quite a while but i was able to send a client certificate in a web request to use for client auth on our server.
First, as awesome as Xamarin and .netCore are, they are missing alot of the methods .net developers are used to. I was not able to build a crossplatform request that would work on both Android and ios such as the HttpWebRequest.
For ios, i created a custom class that inherits from:NSUrlConnectionDataDelegate
I then override the:
public override void WillSendRequestForAuthenticationChallenge(NSUrlConnection
connection, NSUrlAuthenticationChallenge challenge)
{
byte[] cert = System.IO.File.ReadAllBytes("clientCertificate.pfx");
NSUrlCredential credential = iSecurity.ImportPK12File(cert, "certPassword");
challenge.Sender.UseCredential(credential, challenge);
}
I then created a class that returns the credential:
//cert is a byte array of a .pfx file included in the resource file
//iSecurity Custom class
NSUrlCredential credential = iSecurity.ImportPK12File(cert, "certpassword");
public static NSUrlCredential ImportPK12File(byte[] fileBytes, string passPhrase)
{
var cert = new X509Certificate2(fileBytes, passPhrase);
var options = NSDictionary.FromObjectAndKey(NSObject.FromObject(passPhrase), SecImportExport.Passphrase);
NSDictionary[] importStatus;
SecStatusCode statusCode = SecImportExport.ImportPkcs12(fileBytes, options, out importStatus);
if(statusCode != SecStatusCode.Success){
throw new Exception("Error importing certificate. ");
}
NSObject obj = importStatus[0]["trust"];
IntPtr secTrustRef = obj.Handle;
var identityHandle = importStatus[0][SecImportExport.Identity];
var identity = new SecIdentity(identityHandle.Handle);
var certificate = new SecCertificate(cert.GetRawCertData());
SecCertificate[] certificates = { certificate };
return NSUrlCredential.FromIdentityCertificatesPersistance(identity, certificates, NSUrlCredentialPersistence.ForSession);
}
You may also be able to override this method and send the creds:
public override void ReceivedAuthenticationChallenge(NSUrlConnection connection, NSUrlAuthenticationChallenge challenge)
{
base.ReceivedAuthenticationChallenge(connection, challenge);
}
And i may move it to there but in order to fire this off you create the delegate of your class that inherits from :NSUrlConnectionDataDelegate
and add this to your connection. Any request fired through this connection will override the method and pass the certificate.