How To Hack WCF - New Technology, Old Hacking Tricks

First of I'd like to thank Guy for his excellent screencast - very convenient, so thanks.

Specifically I liked introductory screencast for WCF which can be found here: http://blogs.microsoft.co.il/blogs/bursteg/pages/WCF-Introduction-Demo-_2800_ScreenCast_2900_.aspx

It is dubbed in Hebrew, but the screens are flipping in so logical way so that one who does not understand Hebrew will be fine - go for it - recommended a lot for WCF newbies like me.

My interest was to understand the pipeline that the WCF Message goes through before it is put on the transport. The idea was to inject some custom modules (Inspectors) in the pipeline. Why? Is not it clear? To mess around with the message - tamper it in it raw format before it goes down to the transport signed and protected. Why? To show that it DOES NOT matter what communication technology you use - HTTP, Remoting, MSMQ, WCF, RMI, CORBA, DCOM, MQ, <<fill in your own here>> - the basic principle of VALIDATING INPUT ON THE SERVER SIDE is immutable.

Here I showed it for Web Services App Architecture with Security in mind - Video, Part I (that was easy - Fiddler is of much help here)

Then remoting came along - same result, here App Architecture with Security in mind - Video, Part II

Now it is mighty WCF.

I used excellent demo from Madhu here http://blogs.msdn.com/madhuponduru/archive/2006/07/19/671922.aspx that explained how to build IClientMessageInspector (NOTE - demo that works!)

So here is the service contract:

and the implementation:

and the client side validation:

here is the client rejects the input:

and here is the result of server processing for good input:

after adding the custom message inspector, I am offered to tamper the massage before it is sent to the service and the resulting reply from the service is in red at the bottom:

Conclusion

Does that mean that the communication technologies are bad? - NO, it is the way WE use it.

Here is an basic example for input validation in Web Services Web Service Input Validation - it has link to regex usage that you can use on the server side for input validation.

Enjoy