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How to: Use Separate X.509 Certificates for Signing and Encryption

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This topic shows how to configure Windows Communication Foundation (WCF) to use different certificates for message signing and encryption on both the client and service.

To enable separate certificates to be used for signing and encryption, a custom client or service credentials (or both) must be created because WCF does not provide an API to set multiple client or service certificates. Additionally, a security token manager must be provided to leverage the multiple certificates' information and to create an appropriate security token provider for specified key usage and message direction.

The following diagram shows the main classes used, the classes they inherit from (shown by an upward-pointing arrow), and the return types of certain methods and properties.

Chart showing how client credentials are used

For more information about custom credentials, see Walkthrough: Creating Custom Client and Service Credentials.

In addition, you must create a custom identity verifier, and link it to a security binding element in a custom binding. You must also use the custom credentials instead of the default credentials.

The following diagram shows the classes involved in the custom binding, and how the custom identity verifier is linked. There are several binding elements involved, all of which inherit from BindingElement. The AsymmetricSecurityBindingElement has the LocalClientSecuritySettings property, which returns an instance of IdentityVerifier, from which MyIdentityVerifier is customized.

Chart showing a custom binding element

For more information about creating a custom identity verifier, see How to: How to: Create a Custom Client Identity Verifier.

To use separate certificates for signing and encryption

  1. Define a new client credentials class that inherits from the ClientCredentials class. Implement four new properties to allow multiple certificates specification: ClientSigningCertificate, ClientEncryptingCertificate, ServiceSigningCertificate, and ServiceEncryptingCertificate. Also override the CreateSecurityTokenManager method to return an instance of the customized ClientCredentialsSecurityTokenManager class that is defined in the next step.

    public class MyClientCredentials : ClientCredentials
{
    X509Certificate2 clientSigningCert;
    X509Certificate2 clientEncryptingCert;
    X509Certificate2 serviceSigningCert;
    X509Certificate2 serviceEncryptingCert;

    public MyClientCredentials()
    {
    }

    protected MyClientCredentials(MyClientCredentials other)
        : base(other)
    {
        this.clientEncryptingCert = other.clientEncryptingCert;
        this.clientSigningCert = other.clientSigningCert;
        this.serviceEncryptingCert = other.serviceEncryptingCert;
        this.serviceSigningCert = other.serviceSigningCert;
    }

    public X509Certificate2 ClientSigningCertificate
    {
        get
        {
            return this.clientSigningCert;
        }
        set
        {
            this.clientSigningCert = value;
        }
    }

    public X509Certificate2 ClientEncryptingCertificate
    {
        get
        {
            return this.clientEncryptingCert;
        }
        set
        {
            this.clientEncryptingCert = value;
        }
    }

    public X509Certificate2 ServiceSigningCertificate
    {
        get
        {
            return this.serviceSigningCert;
        }
        set
        {
            this.serviceSigningCert = value;
        }
    }

    public X509Certificate2 ServiceEncryptingCertificate
    {
        get
        {
            return this.serviceEncryptingCert;
        }
        set
        {
            this.serviceEncryptingCert = value;
        }
    }

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

    protected override ClientCredentials CloneCore()
    {
        return new MyClientCredentials(this);
    }
}

    Public Class MyClientCredentials
    Inherits ClientCredentials

    Private clientSigningCert As X509Certificate2
    Private clientEncryptingCert As X509Certificate2
    Private serviceSigningCert As X509Certificate2
    Private serviceEncryptingCert As X509Certificate2

    Public Sub New()
    End Sub

    Protected Sub New(ByVal other As MyClientCredentials)
        MyBase.New(other)
        Me.clientEncryptingCert = other.clientEncryptingCert
        Me.clientSigningCert = other.clientSigningCert
        Me.serviceEncryptingCert = other.serviceEncryptingCert
        Me.serviceSigningCert = other.serviceSigningCert
    End Sub

    Public Property ClientSigningCertificate() As X509Certificate2
        Get
            Return Me.clientSigningCert
        End Get
        Set(ByVal value As X509Certificate2)
            Me.clientSigningCert = value
        End Set
    End Property

    Public Property ClientEncryptingCertificate() As X509Certificate2
        Get
            Return Me.clientEncryptingCert
        End Get
        Set(ByVal value As X509Certificate2)
            Me.clientEncryptingCert = value
        End Set
    End Property

    Public Property ServiceSigningCertificate() As X509Certificate2
        Get
            Return Me.serviceSigningCert
        End Get
        Set(ByVal value As X509Certificate2)
            Me.serviceSigningCert = value
        End Set
    End Property

    Public Property ServiceEncryptingCertificate() As X509Certificate2
        Get
            Return Me.serviceEncryptingCert
        End Get
        Set(ByVal value As X509Certificate2)
            Me.serviceEncryptingCert = value
        End Set
    End Property

    Public Overrides Function CreateSecurityTokenManager() As SecurityTokenManager
        Return New MyClientCredentialsSecurityTokenManager(Me)
    End Function

    Protected Overrides Function CloneCore() As ClientCredentials
        Return New MyClientCredentials(Me)
    End Function

End Class

  2. Define a new client security token manager that inherits from the ClientCredentialsSecurityTokenManager class. Override the CreateSecurityTokenProvider method to create an appropriate security token provider. The requirement parameter (a SecurityTokenRequirement) provides the message direction and key usage.

    internal class MyClientCredentialsSecurityTokenManager :
    ClientCredentialsSecurityTokenManager
{
    MyClientCredentials credentials;

    public MyClientCredentialsSecurityTokenManager(
        MyClientCredentials credentials): base(credentials)
    {
        this.credentials = credentials;
    }

    public override SecurityTokenProvider CreateSecurityTokenProvider(
        SecurityTokenRequirement requirement)
    {
        SecurityTokenProvider result = null;
        if (requirement.TokenType == SecurityTokenTypes.X509Certificate)
        {
            MessageDirection direction = requirement.GetProperty
                <MessageDirection>(ServiceModelSecurityTokenRequirement.
                MessageDirectionProperty);
            if (direction == MessageDirection.Output)
            {
                if (requirement.KeyUsage == SecurityKeyUsage.Signature)
                {
                    result = new X509SecurityTokenProvider(
                        this.credentials.ClientSigningCertificate);
                }
                else
                {
                    result = new X509SecurityTokenProvider(this.credentials.
                        ServiceEncryptingCertificate);
                }
            }
            else
            {
                if (requirement.KeyUsage == SecurityKeyUsage.Signature)
                {
                    result = new X509SecurityTokenProvider(this.
                        credentials.ServiceSigningCertificate);
                }
                else
                {
                    result = new X509SecurityTokenProvider(credentials.
                        ClientEncryptingCertificate);
                }
            }
        }
        else
        {
            result = base.CreateSecurityTokenProvider(requirement);
        }

        return result;
    }

    public override SecurityTokenAuthenticator
        CreateSecurityTokenAuthenticator(SecurityTokenRequirement
        tokenRequirement, out SecurityTokenResolver outOfBandTokenResolver)
    {
        return base.CreateSecurityTokenAuthenticator(tokenRequirement,
            out outOfBandTokenResolver);
    }
}

    Friend Class MyClientCredentialsSecurityTokenManager
    Inherits ClientCredentialsSecurityTokenManager

    Private credentials As MyClientCredentials

    Public Sub New(ByVal credentials As MyClientCredentials)
        MyBase.New(credentials)
        Me.credentials = credentials
    End Sub

    Public Overrides Function CreateSecurityTokenProvider(ByVal requirement As SecurityTokenRequirement) As SecurityTokenProvider
        Dim result As SecurityTokenProvider = Nothing
        If requirement.TokenType = SecurityTokenTypes.X509Certificate Then
            Dim direction = requirement.GetProperty(Of MessageDirection)(ServiceModelSecurityTokenRequirement.MessageDirectionProperty)
            If direction = MessageDirection.Output Then
                If requirement.KeyUsage = SecurityKeyUsage.Signature Then
                    result = New X509SecurityTokenProvider(Me.credentials.ClientSigningCertificate)
                Else
                    result = New X509SecurityTokenProvider(Me.credentials.ServiceEncryptingCertificate)
                End If
            Else
                If requirement.KeyUsage = SecurityKeyUsage.Signature Then
                    result = New X509SecurityTokenProvider(Me.credentials.ServiceSigningCertificate)
                Else
                    result = New X509SecurityTokenProvider(credentials.ClientEncryptingCertificate)
                End If
            End If
        Else
            result = MyBase.CreateSecurityTokenProvider(requirement)
        End If

        Return result
    End Function

    Public Overrides Function CreateSecurityTokenAuthenticator(ByVal tokenRequirement As SecurityTokenRequirement, _
                                                               <System.Runtime.InteropServices.Out()> ByRef outOfBandTokenResolver As SecurityTokenResolver) As SecurityTokenAuthenticator
        Return MyBase.CreateSecurityTokenAuthenticator(tokenRequirement, _
                                                       outOfBandTokenResolver)
    End Function

End Class

  3. Define a new service credentials class that inherits from the ServiceCredentials class. Implement four new properties to allow multiple certificates specification: ClientSigningCertificate, ClientEncryptingCertificate, ServiceSigningCertificate, and ServiceEncryptingCertificate. Also override the CreateSecurityTokenManager method to return an instance of the customized ServiceCredentialsSecurityTokenManager class that is defined in the next step.

    public class MyServiceCredentials : ServiceCredentials
{
    X509Certificate2 clientSigningCert;
    X509Certificate2 clientEncryptingCert;
    X509Certificate2 serviceSigningCert;
    X509Certificate2 serviceEncryptingCert;

    public MyServiceCredentials()
    {
    }

    protected MyServiceCredentials(MyServiceCredentials other)
        : base(other)
    {
        this.clientEncryptingCert = other.clientEncryptingCert;
        this.clientSigningCert = other.clientSigningCert;
        this.serviceEncryptingCert = other.serviceEncryptingCert;
        this.serviceSigningCert = other.serviceSigningCert;
    }

    public X509Certificate2 ClientSigningCertificate
    {
        get
        {
            return this.clientSigningCert;
        }
        set
        {
            this.clientSigningCert = value;
        }
    }

    public X509Certificate2 ClientEncryptingCertificate
    {
        get
        {
            return this.clientEncryptingCert;
        }
        set
        {
            this.clientEncryptingCert = value;
        }
    }

    public X509Certificate2 ServiceSigningCertificate
    {
        get
        {
            return this.serviceSigningCert;
        }
        set
        {
            this.serviceSigningCert = value;
        }
    }

    public X509Certificate2 ServiceEncryptingCertificate
    {
        get
        {
            return this.serviceEncryptingCert;
        }
        set
        {
            this.serviceEncryptingCert = value;
        }
    }

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

    protected override ServiceCredentials CloneCore()
    {
        return new MyServiceCredentials(this);
    }
}

    Public Class MyServiceCredentials
    Inherits ServiceCredentials

    Private clientSigningCert As X509Certificate2
    Private clientEncryptingCert As X509Certificate2
    Private serviceSigningCert As X509Certificate2
    Private serviceEncryptingCert As X509Certificate2

    Public Sub New()
    End Sub

    Protected Sub New(ByVal other As MyServiceCredentials)
        MyBase.New(other)
        Me.clientEncryptingCert = other.clientEncryptingCert
        Me.clientSigningCert = other.clientSigningCert
        Me.serviceEncryptingCert = other.serviceEncryptingCert
        Me.serviceSigningCert = other.serviceSigningCert
    End Sub

    Public Property ClientSigningCertificate() As X509Certificate2
        Get
            Return Me.clientSigningCert
        End Get
        Set(ByVal value As X509Certificate2)
            Me.clientSigningCert = value
        End Set
    End Property

    Public Property ClientEncryptingCertificate() As X509Certificate2
        Get
            Return Me.clientEncryptingCert
        End Get
        Set(ByVal value As X509Certificate2)
            Me.clientEncryptingCert = value
        End Set
    End Property

    Public Property ServiceSigningCertificate() As X509Certificate2
        Get
            Return Me.serviceSigningCert
        End Get
        Set(ByVal value As X509Certificate2)
            Me.serviceSigningCert = value
        End Set
    End Property

    Public Property ServiceEncryptingCertificate() As X509Certificate2
        Get
            Return Me.serviceEncryptingCert
        End Get
        Set(ByVal value As X509Certificate2)
            Me.serviceEncryptingCert = value
        End Set
    End Property

    Public Overrides Function CreateSecurityTokenManager() As SecurityTokenManager
        Return New MyServiceCredentialsSecurityTokenManager(Me)
    End Function

    Protected Overrides Function CloneCore() As ServiceCredentials
        Return New MyServiceCredentials(Me)
    End Function

End Class

  4. Define a new service security token manager that inherits from the ServiceCredentialsSecurityTokenManager class. Override the CreateSecurityTokenProvider method to create an appropriate security token provider given the passed-in message direction and key usage.

    internal class MyServiceCredentialsSecurityTokenManager :
    ServiceCredentialsSecurityTokenManager
{
    MyServiceCredentials credentials;

    public MyServiceCredentialsSecurityTokenManager(
        MyServiceCredentials credentials)
        : base(credentials)
    {
        this.credentials = credentials;
    }

    public override SecurityTokenProvider CreateSecurityTokenProvider(
        SecurityTokenRequirement requirement)
    {
        SecurityTokenProvider result = null;
        if (requirement.TokenType == SecurityTokenTypes.X509Certificate)
        {
            MessageDirection direction = requirement.
                GetProperty<MessageDirection>(
                ServiceModelSecurityTokenRequirement.
                MessageDirectionProperty);
            if (direction == MessageDirection.Input)
            {
                if (requirement.KeyUsage == SecurityKeyUsage.Exchange)
                {
                    result = new X509SecurityTokenProvider(
                        credentials.ServiceEncryptingCertificate);
                }
                else
                {
                    result = new X509SecurityTokenProvider(
                        credentials.ClientSigningCertificate);
                }
            }
            else
            {
                if (requirement.KeyUsage == SecurityKeyUsage.Signature)
                {
                    result = new X509SecurityTokenProvider(
                        credentials.ServiceSigningCertificate);
                }
                else
                {
                    result = new X509SecurityTokenProvider(
                        credentials.ClientEncryptingCertificate);
                }
            }
        }
        else
        {
            result = base.CreateSecurityTokenProvider(requirement);
        }
        return result;
    }
}

    Friend Class MyServiceCredentialsSecurityTokenManager
    Inherits ServiceCredentialsSecurityTokenManager

    Private credentials As MyServiceCredentials

    Public Sub New(ByVal credentials As MyServiceCredentials)
        MyBase.New(credentials)
        Me.credentials = credentials
    End Sub

    Public Overrides Function CreateSecurityTokenProvider(ByVal requirement As SecurityTokenRequirement) As SecurityTokenProvider
        Dim result As SecurityTokenProvider = Nothing
        If requirement.TokenType = SecurityTokenTypes.X509Certificate Then
            Dim direction = requirement.GetProperty(Of MessageDirection)(ServiceModelSecurityTokenRequirement.MessageDirectionProperty)
            If direction = MessageDirection.Input Then
                If requirement.KeyUsage = SecurityKeyUsage.Exchange Then
                    result = New X509SecurityTokenProvider(credentials.ServiceEncryptingCertificate)
                Else
                    result = New X509SecurityTokenProvider(credentials.ClientSigningCertificate)
                End If
            Else
                If requirement.KeyUsage = SecurityKeyUsage.Signature Then
                    result = New X509SecurityTokenProvider(credentials.ServiceSigningCertificate)
                Else
                    result = New X509SecurityTokenProvider(credentials.ClientEncryptingCertificate)
                End If
            End If
        Else
            result = MyBase.CreateSecurityTokenProvider(requirement)
        End If
        Return result
    End Function

End Class

To use multiple certificates on the client

  1. Create a custom binding. The security binding element must operate in duplex mode to allow different security token providers to be present for requests and responses. One way to do this is to use a duplex-capable transport or to use the CompositeDuplexBindingElement as shown in the following code. Link the customized IdentityVerifier which is defined in the next step to the security binding element. Replace the default client credentials with the customized client credentials previously created.

                EndpointAddress serviceEndpoint =
                new EndpointAddress(new Uri("http://localhost:6060/service"));

            CustomBinding binding = new CustomBinding();

            AsymmetricSecurityBindingElement securityBE =
                SecurityBindingElement.CreateMutualCertificateDuplexBindingElement(
                MessageSecurityVersion.
WSSecurity10WSTrustFebruary2005WSSecureConversationFebruary2005WSSecurityPolicy11BasicSecurityProfile10);
            // Add a custom IdentityVerifier because the service uses two certificates
            // (one for signing and one for encryption) and an endpoint identity that
            // contains a single identity claim.
            securityBE.LocalClientSettings.IdentityVerifier = new MyIdentityVerifier();
            binding.Elements.Add(securityBE);

            CompositeDuplexBindingElement compositeDuplex =
                new CompositeDuplexBindingElement();
            compositeDuplex.ClientBaseAddress = new Uri("http://localhost:6061/client");
            binding.Elements.Add(compositeDuplex);

            binding.Elements.Add(new OneWayBindingElement());

            binding.Elements.Add(new HttpTransportBindingElement());

            using (ChannelFactory<IMyServiceChannel> factory =
                new ChannelFactory<IMyServiceChannel>(binding, serviceEndpoint))
            {
                MyClientCredentials credentials = new MyClientCredentials();
                SetupCertificates(credentials);
                factory.Endpoint.Behaviors.Remove(typeof(ClientCredentials));
                factory.Endpoint.Behaviors.Add(credentials);

                IMyServiceChannel channel = factory.CreateChannel();
                Console.WriteLine(channel.Hello("world"));
                channel.Close();
            }

    Dim serviceEndpoint As New EndpointAddress(New Uri("http://localhost:6060/service"))

Dim binding As New CustomBinding()

Dim securityBE = SecurityBindingElement.CreateMutualCertificateDuplexBindingElement(MessageSecurityVersion.WSSecurity10WSTrustFebruary2005WSSecureConversationFebruary2005WSSecurityPolicy11BasicSecurityProfile10)
' Add a custom IdentityVerifier because the service uses two certificates 
' (one for signing and one for encryption) and an endpoint identity that 
' contains a single identity claim.
securityBE.LocalClientSettings.IdentityVerifier = New MyIdentityVerifier()
binding.Elements.Add(securityBE)

Dim compositeDuplex As New CompositeDuplexBindingElement()

compositeDuplex.ClientBaseAddress = New Uri("http://localhost:6061/client")

With binding.Elements
    .Add(compositeDuplex)
    .Add(New OneWayBindingElement())
    .Add(New HttpTransportBindingElement())
End With

Using factory As New ChannelFactory(Of IMyServiceChannel)(binding, serviceEndpoint)
    Dim credentials As New MyClientCredentials()
    SetupCertificates(credentials)

    With factory.Endpoint.Behaviors
        .Remove(GetType(ClientCredentials))
        .Add(credentials)
    End With

    Dim channel = factory.CreateChannel()
    Console.WriteLine(channel.Hello("world"))
    channel.Close()
End Using

  2. Define a custom IdentityVerifier. The service has multiple identities because different certificates are used to encrypt the request and to sign the response.

    Note

    In the following sample, the provided custom identity verifier does not perform any endpoint identity checking for demonstration purposes. This is not recommended practice for production code.

    class MyIdentityVerifier : IdentityVerifier
{
    IdentityVerifier defaultVerifier;

    public MyIdentityVerifier()
    {
        this.defaultVerifier = IdentityVerifier.CreateDefault();
    }

    public override bool CheckAccess(EndpointIdentity identity,
        AuthorizationContext authContext)
    {
        // The following implementation is for demonstration only, and
        // does not perform any checks regarding EndpointIdentity.
        // Do not use this for production code.
        return true;
    }

    public override bool TryGetIdentity(EndpointAddress reference,
        out EndpointIdentity identity)
    {
        return this.defaultVerifier.TryGetIdentity(reference, out identity);
    }
}


    Friend Class MyIdentityVerifier
    Inherits IdentityVerifier

    Private defaultVerifier As IdentityVerifier

    Public Sub New()
        Me.defaultVerifier = IdentityVerifier.CreateDefault()
    End Sub

    Public Overrides Function CheckAccess(ByVal identity As EndpointIdentity, ByVal authContext As AuthorizationContext) As Boolean
        ' The following implementation is for demonstration only, and
        ' does not perform any checks regarding EndpointIdentity.
        ' Do not use this for production code.
        Return True
    End Function

    Public Overrides Function TryGetIdentity(ByVal reference As EndpointAddress, <System.Runtime.InteropServices.Out()> ByRef identity As EndpointIdentity) As Boolean
        Return Me.defaultVerifier.TryGetIdentity(reference, identity)
    End Function

End Class

To use multiple certificates on the service

  1. Create a custom binding. The security binding element must operate in a duplex mode to allow different security token providers to be present for requests and responses. As with the client, use a duplex-capable transport or use CompositeDuplexBindingElement as shown in the following code. Replace the default service credentials with the customized service credentials previously created.

                Uri serviceEndpoint = new Uri("http://localhost:6060/service");
            using (ServiceHost host = new ServiceHost(typeof(Service), serviceEndpoint))
            {
                CustomBinding binding = new CustomBinding();
                binding.Elements.Add(SecurityBindingElement.
                    CreateMutualCertificateDuplexBindingElement(
MessageSecurityVersion.WSSecurity10WSTrustFebruary2005WSSecureConversationFebruary2005WSSecurityPolicy11BasicSecurityProfile10));
                binding.Elements.Add(new CompositeDuplexBindingElement());
                binding.Elements.Add(new OneWayBindingElement());
                binding.Elements.Add(new HttpTransportBindingElement());

                MyServiceCredentials credentials = new MyServiceCredentials();
                SetupCertificates(credentials);
                host.Description.Behaviors.Remove(typeof(ServiceCredentials));
                host.Description.Behaviors.Add(credentials);

                ServiceEndpoint endpoint = host.AddServiceEndpoint(
                    typeof(IMyService), binding, "");
                host.Open();

                Console.WriteLine("Service started, press ENTER to stop...");
                Console.ReadLine();
            }

    Dim serviceEndpoint As New Uri("http://localhost:6060/service")
Using host As New ServiceHost(GetType(Service), serviceEndpoint)
    Dim binding As New CustomBinding()

    With binding.Elements
        .Add(SecurityBindingElement.CreateMutualCertificateDuplexBindingElement(MessageSecurityVersion.WSSecurity10WSTrustFebruary2005WSSecureConversationFebruary2005WSSecurityPolicy11BasicSecurityProfile10))
        .Add(New CompositeDuplexBindingElement())
        .Add(New OneWayBindingElement())
        .Add(New HttpTransportBindingElement())
    End With

    Dim credentials As New MyServiceCredentials()
    SetupCertificates(credentials)
    With host.Description.Behaviors
        .Remove(GetType(ServiceCredentials))
        .Add(credentials)
    End With

    Dim endpoint = host.AddServiceEndpoint(GetType(IMyService), binding, "")
    host.Open()

    Console.WriteLine("Service started, press ENTER to stop...")
    Console.ReadLine()
End Using

See also