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Accessing the client certificate when using SSL

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To authenticate the client the client can send a certificate. To do this in Nancy you need one of three hosting solutions: Aspnet, WCF, OWIN or Hosting.Self. Here is shown howto configure all three to work with SSL and client certificates.

Configuration of Aspnet.

If the web.config file within the system.webServer tag we need to specify we want to be able to receive a ClientCertificate. Like this:

  <access sslFlags="SslNegotiateCert"/>
    <clientCertificateMappingAuthentication enabled="true"/>

You may get an error telling you this:

This configuration section cannot be used at this path. This happens when the section is locked at a parent level. Locking is either by default (overrideModeDefault="Deny"), or set explicitly by a location tag with overrideMode="Deny" or the legacy allowOverride="false".

This is solved by editing your applicationhost.config and setting the overrideModeDefault to Allow for the following elements.

<section name="access" overrideModeDefault="Allow" />
<section name="clientCertificateMappingAuthentication" overrideModeDefault="Allow" />

See here how to enable SSL for IISexpress.

See here how to do it on IIS.

Configuration of WCF

Nothing is ever easy with WCF configuration, this is no exception.

Lets start with the basic host:

private static readonly Uri BaseUri = new Uri("");

var host = new WebServiceHost(
    new NancyWcfGenericService(new DefaultNancyBootstrapper()),

We need to tell the binding we want to use Transport Security and we need to tell it to expect a certificate from the client. We also need to tell WCF not to worry about whether the certificate is valid. Or at least determine ourselves what valid is.


var binding = new WebHttpBinding();
binding.Security.Mode = WebHttpSecurityMode.Transport;
binding.Security.Transport.ClientCredentialType = HttpClientCredentialType.Certificate;

Custom validation of the certificate.

public class Auth : X509CertificateValidator
    public override void Validate(System.Security.Cryptography.X509Certificates.X509Certificate2 certificate)

Tell the host where to find the Validator

host.Credentials.ClientCertificate.Authentication.CertificateValidationMode = System.ServiceModel.Security.X509CertificateValidationMode.Custom;
host.Credentials.ClientCertificate.Authentication.CustomCertificateValidator = new Auth();


Add the endpoint:


Tell the host where to find the server certificate:

host.Credentials.ServiceCertificate.SetCertificate(StoreLocation.LocalMachine, StoreName.My, X509FindType.FindByThumbprint, "30 3b 4a db 5a eb 17 ee ac 00 d8 57 66 93 a9 08 c0 1e 0b 71");

Open it:


Command line configuration

But this wont work you need to run a netsh command like this: where certhash is the thumbprint of the server certificate without spaces.

netsh http add sslcert ipport= certhash=303b4adb5aeb17eeac00d8576693a908c01e0b71 appid={00112233-4455-6677-8899-AABBCCDDEEFF} clientcertnegotiation=enable

Configuration of OWIN

It'll just be there if the host sends it on.

If you use IIS as a host. You'll need to do the same config as with Aspnet. And you'll need an OWIN Aspnet host that supports the ClientCertificate. The one in the OWIN demo in Nancy does. The one by @prabirshrestha also does.

Configuration of Hosting.Self

It starts with a commandline command like the one in wcf: (remember the certhash is the thumbprint without spaces)

netsh http add sslcert ipport= certhash=303b4adb5aeb17eeac00d8576693a908c01e0b71 appid={00112233-4455-6677-8899-AABBCCDDEEFF} clientcertnegotiation=enable

Then you can just set the url of the selfhost to https://localhost:1234 and it'll work. The selfhost will automatically rewrite localhost to + if it has administrative rights. Allowing the selfhost to listen on all ipaddresses.

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