The new model object filtering is a fascinating area in my mind.  One thing 
we've implemented (before Acegi had its own filtering) is the ability to 
filter down to the property level on an object.  In other words, you can 
secure a specific property and if someone doesn't have clearance then the 
property will be cleared.  This introduces all sorts of interesting problems 
in some scenarios.  For example, in our case the value objects passed back 
and forth between clients and server side services double as our Hibernate 
data object model.  In other words, we don't have separate value objects but 
instead use a single data object model for both data access and service 
invocation.  This gets quite tricky when you combine it with property level 
filtering.  Imagine a service method that returns a model object with several 
properties filtered out.  The user then makes some changes to the object and 
sends it back in another service call to be updated.  What the user sends 
back to the server is a partial object in that some of the properties are 
blank since they were secured from the client to begin with.  If you 
persisted the object as-is, then Hibernate would blindly write those cleared 
property values back to the DB - very bad.  Oh, and don't forget that some 
properties could be secured for a particular client so that they are 
read-only or even write-only.  And don't forget to throw a security exception 
if the client tries to pass a value in a non-writeable field.  And then 
there's recursive data structures to contend with... property values that are 
themselves collections of securable objects... and if you filtered a 
collection of securable objects from a property, and the client returns that 
object to the server to be updated, how do you determine if the client 
legitimately removed an object from the collection, or if the object was 
filtered due to security?  You wouldn't want to have hibernate persist the 
collection as-is, or it would remove from the DB objects that were only 
filtered for security reasons.  Fun stuff, eh?

  - Andy


On Thursday 30 December 2004 01:49 pm, Vladimir Horev wrote:
> Hello list!
>
> I'm planning to write a MSc thesis on the subject of business tier
> security. My idea was to take part of some open source project (acegi)
> and develop some component that I could use in my thesis. Could you
> recommend me something on that?
>
> regards, Vladimir
>
>
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