Writing a WCF secure data service for Excel PowerPivot

Question

I am having trouble recording a secure WCF data service that PowerPivot will use. The service works fine, and I can easily receive data in PowerPivot.

My problem is that when I enter the user ID and password for the data channel in PowerPivot (in the advanced data transfer settings), I cannot access them from inside the WCF service. I would like to use both the user ID and password for authentication with the database, but first I need to get them. :)

Are there any good examples of how to write a secure WCF data service specifically for PowerPivot?

Many thanks.

Answer 1

I struggled with the same, and after some research I found this blog post that made me go for a ride:

http://pfelix.wordpress.com/2011/04/21/wcf-web-api-self-hosting-https-and-http-basic-authentication/

In short, there is some work that you must do to allow the Principal to switch to a service call.

Answer 2

MSDN has a complete downloadable sample.

Basic Authentication WCF Data Service for PowerPivot Clients

https://code.msdn.microsoft.com/office/WCF-Data-Service-with-547e9341

Update

Ok, now I used the code in the link (which I was learning while I was writing). I know that it works, so here is a sample code:

1. HTTP ( 401).

namespace WebHostBasicAuth.Modules
{
    public class BasicAuthHttpModule : IHttpModule
    {
        private const string Realm = "My Realm";

        public void Init(HttpApplication context)
        {
            // Register event handlers
            context.AuthenticateRequest += OnApplicationAuthenticateRequest;
            context.EndRequest += OnApplicationEndRequest;
        }

        private static void SetPrincipal(IPrincipal principal)
        {
            Thread.CurrentPrincipal = principal;
            if (HttpContext.Current != null)
            {
                HttpContext.Current.User = principal;
            }
        }

        // TODO: Here is where you would validate the username and password.
        private static bool CheckPassword(string username, string password)
        {
            return username == "user" && password == "password";
        }

        private static void AuthenticateUser(string credentials)
        {
            try
            {
                var encoding = Encoding.GetEncoding("iso-8859-1");
                credentials = encoding.GetString(Convert.FromBase64String(credentials));

                int separator = credentials.IndexOf(':');
                string name = credentials.Substring(0, separator);
                string password = credentials.Substring(separator + 1);

                if (CheckPassword(name, password))
                {
                    var identity = new GenericIdentity(name);
                    SetPrincipal(new GenericPrincipal(identity, null));
                }
                else
                {
                    // Invalid username or password.
                    HttpContext.Current.Response.StatusCode = 401;
                }
            }
            catch (FormatException)
            {
                // Credentials were not formatted correctly.
                HttpContext.Current.Response.StatusCode = 401;
            }
        }

        private static void OnApplicationAuthenticateRequest(object sender, EventArgs e)
        {
            var request = HttpContext.Current.Request;
            var authHeader = request.Headers["Authorization"];
            if (authHeader != null)
            {
                var authHeaderVal = AuthenticationHeaderValue.Parse(authHeader);

                // RFC 2617 sec 1.2, "scheme" name is case-insensitive
                if (authHeaderVal.Scheme.Equals("basic",
                        StringComparison.OrdinalIgnoreCase) &&
                    authHeaderVal.Parameter != null)
                {
                    AuthenticateUser(authHeaderVal.Parameter);
                }
            }
        }

        // If the request was unauthorized, add the WWW-Authenticate header 
        // to the response.
        private static void OnApplicationEndRequest(object sender, EventArgs e)
        {
            var response = HttpContext.Current.Response;
            if (response.StatusCode == 401)
            {
                response.Headers.Add("WWW-Authenticate",
                    string.Format("Basic realm=\"{0}\"", Realm));
            }
        }

        public void Dispose() 
        {
        }
    }
}

2. IIS web.config.

  <system.webServer>
    <modules>
      <add name="BasicAuthHttpModule" 
        type="WebHostBasicAuth.Modules.BasicAuthHttpModule, YourAssemblyName"/>
    </modules>
  ...

Excel PowerPivot

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