Token Authenticator

Article
12/10/2009

This sample demonstrates how to implement a custom token authenticator. A token authenticator in Windows Communication Foundation (WCF) is used for validating the token used with the message, verifying that it is self-consistent, and authenticating the identity associated with the token.

Custom token authenticators are useful in a variety of cases, such as:

When you want to override the default authentication mechanism associated with a token.
When you are building a custom token.

This sample demonstrates the following:

How a client can authenticate using a username/password pair.
How the server can validate the client credentials using a custom token authenticator.
How the WCF service code ties in with the custom token authenticator.
How the server can be authenticated using the server's X.509 certificate.

This sample also shows how the caller's identity is accessible from WCF after the custom token authentication process.

The service exposes a single endpoint for communicating with the service, defined using the App.config configuration file. The endpoint consists of an address, a binding, and a contract. The binding is configured with a standard wsHttpBinding, with the security mode set to message - the default mode of the wsHttpBinding. This sample sets the standard wsHttpBinding to use client username authentication. The service also configures the service certificate using serviceCredentials behavior. The securityCredentials behavior allows you to specify a service certificate. A service certificate is used by a client to authenticate the service and provide message protection. The following configuration references the localhost certificate installed during the sample setup as described in the following setup instructions.

<system.serviceModel>
    <services>
      <service 
          name="Microsoft.ServiceModel.Samples.CalculatorService"
          behaviorConfiguration="CalculatorServiceBehavior">
        <host>
          <baseAddresses>
            <!-- configure base address provided by host -->
            <add baseAddress ="https://localhost:8000/servicemodelsamples/service" />
          </baseAddresses>
        </host>
        <!-- use base address provided by host -->
        <endpoint address=""
                  binding="wsHttpBinding"
                  bindingConfiguration="Binding1" 
                  contract="Microsoft.ServiceModel.Samples.ICalculator" />
      </service>
    </services>

    <bindings>
      <wsHttpBinding>
        <binding name="Binding1">
          <security mode="Message">
            <message clientCredentialType="UserName" />
          </security>
        </binding>
      </wsHttpBinding>
    </bindings>

    <behaviors>
      <serviceBehaviors>
        <behavior name="CalculatorServiceBehavior">
          <serviceDebug includeExceptionDetailInFaults="False" />
          <!-- 
          The serviceCredentials behavior allows one to define a service certificate.
          A service certificate is used by a client to authenticate the service and provide message protection.
          This configuration references the "localhost" certificate installed during the setup instructions.
....        -->
          <serviceCredentials>
            <serviceCertificate findValue="localhost" storeLocation="LocalMachine" storeName="My" x509FindType="FindBySubjectName" />
          </serviceCredentials>
        </behavior>
      </serviceBehaviors>
    </behaviors>

  </system.serviceModel>

The client endpoint configuration consists of a configuration name, an absolute address for the service endpoint, the binding, and the contract. The client binding is configured with the appropriate Mode and clientCredentialType.

<system.serviceModel>
    <client>
      <endpoint name=""
                address="https://localhost:8000/servicemodelsamples/service" 
                binding="wsHttpBinding" 
                bindingConfiguration="Binding1" 
                contract="Microsoft.ServiceModel.Samples.ICalculator">
      </endpoint>
    </client>

    <bindings>
      <wsHttpBinding>
        <binding name="Binding1">
          <security mode="Message">
            <message clientCredentialType="UserName" />
          </security>
        </binding>
      </wsHttpBinding>
    </bindings>
  </system.serviceModel>

The client implementation sets the user name and password to use.

static void Main()
{
     ...
     client.ClientCredentials.UserNamePassword.UserName = username;
     client.ClientCredentials.UserNamePassword.Password = password;
     ...
}

Custom Token Authenticator

Use the following steps to create a custom token authenticator:

Write a custom token authenticator.

The sample implements a custom token authenticator that validates that the username has a valid email format. It derives the UserNameSecurityTokenAuthenticator. The most important method in this class is ValidateUserNamePasswordCore. In this method, the authenticator validates the format of the username and also that the host name is not from a rogue domain. If both conditions are met, then it returns a read-only collection of IAuthorizationPolicy instances that is then used to provide claims that represent the information stored inside the username token.

protected override ReadOnlyCollection<IAuthorizationPolicy> ValidateUserNamePasswordCore(string userName, string password)
{
    if (!ValidateUserNameFormat(userName))
        throw new SecurityTokenValidationException("Incorrect UserName format");

    ClaimSet claimSet = new DefaultClaimSet(ClaimSet.System, new Claim(ClaimTypes.Name, userName, Rights.PossessProperty));
    List<IIdentity> identities = new List<IIdentity>(1);
    identities.Add(new GenericIdentity(userName));
    List<IAuthorizationPolicy> policies = new List<IAuthorizationPolicy>(1);
    policies.Add(new UnconditionalPolicy(ClaimSet.System, claimSet, DateTime.MaxValue.ToUniversalTime(), identities));
    return policies.AsReadOnly();
}

Provide an authorization policy that is returned by custom token authenticator.

This sample provides its own implementation of IAuthorizationPolicy called UnconditionalPolicy that returns set of claims and identities that were passed to it in its constructor.

class UnconditionalPolicy : IAuthorizationPolicy
{
    String id = Guid.NewGuid().ToString();
    ClaimSet issuer;
    ClaimSet issuance;
    DateTime expirationTime;
    IList<IIdentity> identities;

    public UnconditionalPolicy(ClaimSet issuer, ClaimSet issuance, DateTime expirationTime, IList<IIdentity> identities)
    {
        if (issuer == null)
            throw new ArgumentNullException("issuer");
        if (issuance == null)
            throw new ArgumentNullException("issuance");

        this.issuer = issuer;
        this.issuance = issuance;
        this.identities = identities;
        this.expirationTime = expirationTime;
    }

    public string Id
    {
        get { return this.id; }
    }

    public ClaimSet Issuer
    {
        get { return this.issuer; }
    }

    public DateTime ExpirationTime
    {
        get { return this.expirationTime; }
    }

    public bool Evaluate(EvaluationContext evaluationContext, ref object state)
    {
        evaluationContext.AddToTarget(this, this.issuance);

        if (this.identities != null)
        {
            object value;
            IList<IIdentity> contextIdentities;
            if (!evaluationContext.Properties.TryGetValue("Identities", out value))
            {
                contextIdentities = new List<IIdentity>(this.identities.Count);
                evaluationContext.Properties.Add("Identities", contextIdentities);
            }
            else
            {
                contextIdentities = value as IList<IIdentity>;
            }
            foreach (IIdentity identity in this.identities)
            {
                contextIdentities.Add(identity);
            }
        }

        evaluationContext.RecordExpirationTime(this.expirationTime);
        return true;
    }
}

Write a custom security token manager.

The SecurityTokenManager is used to create a SecurityTokenAuthenticator for specific SecurityTokenRequirement objects that are passed to it in the CreateSecurityTokenAuthenticator method. The security token manager is also used to create token providers and token serializers, but those are not covered by this sample. In this sample, the custom security token manager inherits from ServiceCredentialsSecurityTokenManager class and overrides the CreateSecurityTokenAuthenticator method to return custom username token authenticator when the passed token requirements indicate that username authenticator is requested.

    public class MySecurityTokenManager : ServiceCredentialsSecurityTokenManager
    {
        MyUserNameCredential myUserNameCredential;

        public MySecurityTokenManager(MyUserNameCredential myUserNameCredential)
            : base(myUserNameCredential)
        {
            this.myUserNameCredential = myUserNameCredential;
        }

        public override SecurityTokenAuthenticator CreateSecurityTokenAuthenticator(SecurityTokenRequirement tokenRequirement, out SecurityTokenResolver outOfBandTokenResolver)
        {
            if (tokenRequirement.TokenType ==  SecurityTokenTypes.UserName)
            {
                outOfBandTokenResolver = null;
                return new MyTokenAuthenticator();
            }
            else
            {
                return base.CreateSecurityTokenAuthenticator(tokenRequirement, out outOfBandTokenResolver);
            }
        }
    }

Write a custom service credential.

The service credentials class is used to represent the credentials that are configured for the service and creates a security token manager that is used to obtain token authenticators, token providers and token serializers.

public class MyUserNameCredential : ServiceCredentials
{

    public MyUserNameCredential()
        : base()
    {
    }

    protected override ServiceCredentials CloneCore()
    {
        return new MyUserNameCredential();
    }

    public override SecurityTokenManager CreateSecurityTokenManager()
    {
        return new MySecurityTokenManager(this);
    }

}

Configure the service to use the custom service credential.

In order for the service to use the custom service credential, we delete the default service credential class after capturing the service certificate that is already preconfigured in the default service credential, and configure the new service credential instance to use the preconfigured service certificates and add this new service credential instance to service behaviors.
```
ServiceCredentials sc = serviceHost.Credentials;
X509Certificate2 cert = sc.ServiceCertificate.Certificate;
MyUserNameCredential serviceCredential = new MyUserNameCredential();
serviceCredential.ServiceCertificate.Certificate = cert;
serviceHost.Description.Behaviors.Remove((typeof(ServiceCredentials)));
serviceHost.Description.Behaviors.Add(serviceCredential);
```

To display the caller's information, you can use the PrimaryIdentity as shown in the following code. The Current contains claims information about the current caller.

static void DisplayIdentityInformation()
{
    Console.WriteLine("\t\tSecurity context identity  :  {0}", 
            ServiceSecurityContext.Current.PrimaryIdentity.Name);
     return;
}

When you run the sample, the operation requests and responses are displayed in the client console window. Press ENTER in the client window to shut down the client.

Setup Batch File

The Setup.bat batch file included with this sample allows you to configure the server with relevant certificates to run a self-hosted application that requires server certificate based security. This batch file must be modified to work across machines or to work in a non-hosted case.

The following provides a brief overview of the different sections of the batch files so that they can be modified to run in appropriate configuration.

Creating the server certificate.

The following lines from the Setup.bat batch file create the server certificate to be used. The %SERVER_NAME% variable specifies the server name. Change this variable to specify your own server name. The default in this batch file is localhost.
```
echo ************
echo Server cert setup starting
echo %SERVER_NAME%
echo ************
echo making server cert
echo ************
makecert.exe -sr LocalMachine -ss MY -a sha1 -n CN=%SERVER_NAME% -sky exchange -pe
```
Installing the server certificate into client's trusted certificate store.

The following lines in the Setup.bat batch file copy the server certificate into the client trusted people store. This step is required because certificates generated by Makecert.exe are not implicitly trusted by the client system. If you already have a certificate that is rooted in a client trusted root certificate—for example, a Microsoft issued certificate—this step of populating the client certificate store with the server certificate is not required.
```
certmgr.exe -add -r LocalMachine -s My -c -n %SERVER_NAME% -r CurrentUser -s TrustedPeople
```
Note

The setup batch file is designed to be run from a Windows SDK Command Prompt. It requires that the MSSDK environment variable point to the directory where the SDK is installed. This environment variable is automatically set within a Windows SDK Command Prompt.

To set up and build the sample

Ensure that you have performed the One-Time Set Up Procedure for the Windows Communication Foundation Samples.
To build the solution, follow the instructions in Building the Windows Communication Foundation Samples.

To run the sample on the same machine

Make sure that the path includes the folder where Makecert.exe is located.
Run Setup.bat from the sample installation folder. This installs all the certificates required for running the sample.
Launch service.exe from service\bin.
Launch client.exe from \client\bin. Client activity is displayed on the client console application.
If the client and service are not able to communicate, see Troubleshooting Tips for WCF Samples.

To run the sample across machines

Create a directory on the service machine for the service binaries.
Copy the service program files to the service directory on the service machine. Also copy the Setup.bat and Cleanup.bat files to the service machine.
You must have a server certificate with the subject name that contains the fully-qualified domain name of the machine. The service App.config file must be updated to reflect this new certificate name. You can create one by using the Setup.bat if you set the %SERVER_NAME% variable to fully-qualified host name of the machine on which the service will run.
Copy the server certificate into the CurrentUser-TrustedPeople store of the client. You do not need to do this except when the server certificate is issued by a client trusted issuer.
In the App.config file on the service machine, change the value of the base address to specify a fully-qualified machine name instead of localhost.
On the service machine, run service.exe from a command prompt.
Copy the client program files from the \client\bin\ folder, under the language-specific folder, to the client machine.
In the Client.exe.config file on the client machine, change the address value of the endpoint to match the new address of your service.
On the client machine, launch Client.exe from a command prompt.
If the client and service are not able to communicate, see Troubleshooting Tips for WCF Samples.

To clean up after the sample

Run Cleanup.bat in the samples folder once you have finished running the sample.

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