Identifying WCF Client ID

Question

I have a WCF web service that exposes several business methods. I also have two clients - an asp.net GUI and a data migration application that both connect to the wcf backend to invoke various business transactions.

I need my backend to be able to identify and distinguish between which wcf client has made a call to some variant logic.

Is there a way that my WCF service is able to identify clients connected to it? Also is there a way to use a signed key to prevent a client from spoofing their identity?

Answer 1

You can solve this via a custom header.

You can add a custom header as part of the endpoint in the client application's configuration file. You would then make each client's custom header different. For example, in the ASP.NET version:

        <endpoint
            name="basicHttpEndpoint"
            address="http://localhost:8972"
            binding="basicHttpBinding"
            contract="MySeriveContractLib.IMyService"
            >
            <headers>
                <ClientIdentification>ASP_Client</ClientIdentification>
            </headers>
        </endpoint>

Then the service can check the header value like so:

public void MyServiceMethod()
{
   var opContext = OperationContext.Current;
   var requestContext = opContext.RequestContext;
   var headers = requestContext.RequestMessage.Headers;
   int headerIndex = headers.FindHeader("ClientIdentification", "");
   var clientString = headers.GetHeader<string>(headerIndex);
   if clientString=="ASP_Client"
   {
       // ...
   }
   else
   {
      // ...
   }
}

Answer 2

In order to identify the type of caller (ASP.NET vs. WInforms or whatever), you probably need to add a custom header to your WCF messages - there's no way the service can know anything about the calling client unless it's part of the message or the headers sent. For this, your best bet is to write a WCF Message Inspector - and this blog post here will show you how to do this.

As for security - depends on your environment. In a corporate LAN behind a firewall - use the Windows credentials. If you're "outside facing", your best bet would be to install digital certificates on the clients to verify their identity.

WCF Guru Juval Löwy has a really good article on MSDN Magazine, Declarative WCF Security, that describes five common security scenarios in WCF and how to implement them. Highly recommended reading.