Implement Windows Authentication and Security in WCF Service

In this article, I'll explain how we can implement windows authentication with transport level security in intranet environment.

Windows authentication

In a typical Intranet environment, a client and a service are usually .NET applications. Windows authentication is the most suitable authentication type in an Intranet where client credentials stored in windows accounts & groups. An Intranet environment addresses a wide range of business applications. Developers have more control in this environment.

For Intranet, you can use netTcpBinding,NetNamedPipeBinding and NetMsmqBinding for secure and fast communication.

Windows credential is default credential type and transport security is default security mode for these bindings.

Protection Level

You can set Transport Security protection level through WCF:

• None: WCF doesn't protect message transfer from client to service.
• Signed: WCF ensures that message have come only from authenticated caller. WCF checks validity of message by checking Checksum at service side. It provides authenticity of message.
• Encrypted & Signed: Message is signed as well as encrypted. It provides integrity, privacy and authenticity of message.

Configuration in WCF Service for Windows Authentication

Service is hosted on netTcpBinding with credential type windows and protection level as EncryptedAndSigned.

var tcpbinding = new NetTcpBinding(SecurityMode.Transport);
//Client credential will be used of windows user
tcpbinding.Security.Transport.ClientCredentialType =
     TcpClientCredentialType.Windows;
// When configured for EncryptAndSign protection level, WCF both signs the message and encrypts
//its content. The Encrypted and Signed protection level provides integrity,
//privacy, and authenticity.
tcpbinding.Security.Transport.ProtectionLevel =
     System.Net.Security.ProtectionLevel.EncryptAndSign;
Client credential type can be set by TcpClientCredentialType enum
public enum TcpClientCredentialType
{
    None,
    Windows,
    Certificate
}

Protection level can be set by ProtectionLevel enum.

     // Summary:
     //     Indicates the security services requested for an authenticated stream.
    public enum ProtectionLevel
    {
         // Summary:
         //     Authentication only.
        None = 0,
         //
         // Summary:
         //     Sign data to help ensure the integrity of transmitted data.
        Sign = 1,
         //
         // Summary:
         //     Encrypt and sign data to help ensure the confidentiality and integrity of
         //     transmitted data.
        EncryptAndSign = 2,
    }

WCF Service Code

Service Host

    class Program
    {
        static void Main(string[] args)
        {
            Uri baseAddress = new Uri("http://localhost:8045/MarketService");
            using (var productHost = new ServiceHost(typeof(MarketDataProvider)))
            {
                 var tcpbinding = new NetTcpBinding(SecurityMode.Transport);

                 //Client credential will be used of windows user
                 tcpbinding.Security.Transport.ClientCredentialType =
               TcpClientCredentialType.Windows;

                 // When configured for EncryptAndSign protection level, WCF both signs the message and encrypts
                 //its content. The Encrypted and Signed protection level provides integrity,
                 //privacy, and authenticity.
                 tcpbinding.Security.Transport.ProtectionLevel =
                System.Net.Security.ProtectionLevel.EncryptAndSign;
 
                 ServiceEndpoint productEndpoint = productHost;

                 AddServiceEndpoint(typeof(IMarketDataProvider), tcpbinding,
                "net.tcp://localhost:8000/MarketService");
 
                 ServiceEndpoint producthttpEndpoint = productHost.AddServiceEndpoint(
                typeof(IMarketDataProvider), new BasicHttpBinding(),
                "http://localhost:8045/MarketService");
 
                productHost.Open();
                Console.WriteLine("The Market service is running and is listening on:");
                Console.WriteLine("{0} ({1})",
                         productEndpoint.Address.ToString(),
                         productEndpoint.Binding.Name);
                Console.WriteLine("{0} ({1})",
                         producthttpEndpoint.Address.ToString(),
                         producthttpEndpoint.Binding.Name);
                Console.WriteLine("\nPress any key to stop the service.");
                Console.ReadKey();
            }
        }
    }

Alternatively, you can configure the binding using a config file:

   <bindings>
         <netTcpBinding>
               <binding name = "TCPWindowsSecurity">
                      <security mode = "Transport">
                            <transport
                               clientCredentialType = "Windows"
                               protectionLevel = "EncryptAndSign"/>
                      </security>
               </binding>
         </netTcpBinding>
   </bindings>  

Run WCF Service

Client Application

       static void Main(string[] args)
       {
            try
            {
                Console.WriteLine("Connecting to Service..");
                var proxy = new ServiceClient(new NetTcpBinding(),
                new EndpointAddress("net.tcp://localhost:8000/MarketService"));
                Console.WriteLine("MSFT Price:{0}", proxy.GetMarketPrice("MSFT.NSE"));
                Console.WriteLine("Getting price for Google");
                double price = proxy.GetMarketPrice("GOOG.NASDAQ");
            }

            catch (FaultException ex)
            {
                Console.WriteLine("Service Error:" + ex.Detail.ValidationError);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Service Error:" + ex.Message);
            }
            Console.ReadLine();
       }

ServiceClient is custom class which inherits ClientBase<T> class in System.ServiceModel namespace to create channels and communication with service on endpoints.

    public class ServiceClient : ClientBase, IMarketDataProvider
    {
        public ServiceClient() { }
        public ServiceClient(string endpointConfigurationName) :
            base(endpointConfigurationName) { }
 
        public ServiceClient(string endpointConfigurationName, string remoteAddress) :
            base(endpointConfigurationName, remoteAddress) { }
 
        public ServiceClient(string endpointConfigurationName,
            System.ServiceModel.EndpointAddress remoteAddress) :
            base(endpointConfigurationName, remoteAddress){ }

        public ServiceClient(System.ServiceModel.Channels.Binding binding,
            System.ServiceModel.EndpointAddress remoteAddress) :
            base(binding, remoteAddress){ }

        ///
        /// IMarketDataProvider method
        ///  

        public double GetMarketPrice(string symbol)
        {
            return base.Channel.GetMarketPrice(symbol);
        }
    }

Verify User credentials in Service

You can see caller information in WCF service by ServiceSecurityContext class. Every operation on a secured WCF service has a security call context. The security call context is represented by the class ServiceSecurityContext.The main use for the security call context is for custom security mechanisms, as well as analysis and auditing.

ServiceSecurityContext.Current in Quickwatch window.

Send Alternate Windows credentials to Service

WCF also give option to send alternate windows credential from client. By default it send logged in user credential. You can send alternate credential like below

proxy.ClientCredentials.Windows.ClientCredential.Domain = "mydomain";proxy.ClientCredentials.Windows.ClientCredential.UserName = "ABC";proxy.ClientCredentials.Windows.ClientCredential.Password = "pwd";

Now If I run client application with changed credentials, if credentials are of valid windows user, service will authenticate caller else it will reject caller request. In my case I deliberately gives wrong credential to produce reject exception.

Service sends "System.Security.Authentication.InvalidCredentialException with message "The server has rejected the client credentials."

I hope you understood windows authentication concept here. If you have any question please feel free to send me comments.