In the previous post, we have stated the several problems not being able to configure ProtectionLevel for different endpoint declaratively using configuration files. In this post, we address this issue and thereby, describe how to specify ProtectionLevel for multiple endpoints of a service using .config file.

Outline. In this post, we start by stating motivation of specifing ProtectionLevel for multiple endpoints of a service declaritvely instead of programmatically. Then, we discuss the steps to achieve it.

Motivation: ProtectionLevel for Multiple Endpoints

Basically, ProtectionLevel enforces a security requirement on request and response messages in the channel, and all the consumer of the message must conform to that requirement; anything otherwise results in runtime exception. In the last post, we have described how to configure ProtectionLevel at different level of WCF messaging stack and observed that it can only be set programmatically in the contract of a WCF service, which unfortunately has impacts on all the preconfigured bindings.

For instance, consider that we would like to have two different endpoints to use different ProtectionLevel. In addition, we want to make it configurable so that we can the security behavior of the endpoint conveniently after it has been deployed.

Are these requirements practical? To answer that, consider following case: we have only one endpoint and we are using message level security with wsHttpBinding (or ws2007httpbinding preferable one for internet based WCF Service). For internet users consuming this service, we are using ProtectionLevel.EncryptAndSign because of the security requirement imposed for our application. However, in case of local intranet, we don’t want to take the overhead of
ProtectionLevel.EncryptAndSign rather would like to use ProtectionLevel.Sign to make the service a bit more responsive and efficient by getting rid of the overhead of encryption of requests and responses. Most importantly, we don’t need ProtectionLevel.EncryptAndSign for the messages in this context as per security policy. Out of the box, there is no features available that can enable the use of different ProtectionLevel in these cases.

Obviously, there is one naive approach to host to service twice by compiling the code in 2 different ProtectionLevel. At 1 to 10 scale, how would you rate this solution ? Ok , then let’s move on…

Thus, what we need is to make two different endpoints to work with different ProtectionLevel, and using custom endpoint behavior, it can be achieved. Thus, the internet users will be able to use the wsHttpBinding with default ProtectionLevel, while the intranet users use the less secure– ProtectionLevel.Sign. The next section shows how to achieve this.

ProtectionLevel Configuration via Custom Endpoint Behavior

To do this, we have following these steps.First we have to create a Custom EndpointBehavior by implementing IEndpointBehavior as below –

Then, we create a BehaviorElement by extending BehaviorExtensionElement to make the behavior configurable through config file.

Thus the coding part this done. Let’s start configuring. To do so, first thing that needs to be done is to add a behaviorExtensions inside system.serviceModel>behaviorExtensions specifying the newly created custom Endpoint behavior :

Then, we create a endpoint behavior like below:

Now, if we need to use a similar ProtectionLevel that we configured at the previous step in any endpoint , we simply need to add it as behaviorConfiguration, and we are done.

More on MessageSecurityBehavior

So far, we have described how to configure ProtectionLevel at runtime. Next we explain MessageSecurityBehavior. By changing the ChannelProtectionRequirement of an Endpoint, the new custom behavior impacts requests and responses of the channel. Moreover, the contract also binds to the configured ProtectionLevel. Then, the two different MessagePartSpecification was created, where 1^st one is an empty MessagePartSpecification, and 2^nd one refers to the MessagePartSpecification which contains body.

Depending of different value ProtectionLevel, the MessagePartSpecification are set to ChannelProtectionRequirements.

For instance, in case ProtectionLevel.Sign, in OutgoingSignatureParts and IncomingSignatureParts of ChannelProtectionRequirements MessagePartSpecification that included Body is being added to be signed from client to the server and again back to client from server. However, in this case , encryption is not needed, so in OutgoingEncryptionParts and IncomingEncryptionParts , empty MessagePartSpecification is added, and that results in unencrypted messages.

Conclusion

In this post, we show how to declaritively specify the ProtectionLevel for multiple endpoints exposed by a WCF service. Though it’s not difficult to update the ProtectionLevel at runtime, we must note that client and server always conform to the ProtectionLevel requirement, and as a consequence, updating the ProtectionLevel at runtime might results in updating the clients configuration/code.

Additional Links

1. WCF Security: WCF Performance & ProtectionLevel – Part 1 : https://adilakhter.wordpress.com/2009/08/06/wcf-security-wcf-performance-protectionlevel-part-1/
2. Custom WCF Behaviors through App.Config :http://winterdom.com/2006/10/customwcfbehaviorsthroughappconfig
3. Configuring ProtectionLevel : http://blogs.msdn.com/drnick/archive/2008/03/10/configuring-protection-level.aspx
4. Fundamentals of WCF Security : http://www.code-magazine.com/article.aspx?quickid=0611051