We have a number of security features blocking access to various OData v4 (Microsoft OData v4 implementation) actions based on user roles and permissions. To some extent it is record-level access rights. These security checks are implemented in controller actions themselves, namely the data is filtered directly in the EF LINQ query filter based SQL joins to user permissions. However, as long as [Queryable(MaxExpansionDepth = 0)] is not applied everywhere (which we don't want) we have found that any user can tack on $expand to any URL and get any related entity he pleases, without going through the security checks of the actions defined for each of the standard entity routes. For example, if /OData/Projects/ is accessible to a user but /OData/Projects(5)/Employees/ to access employees associated with project 5 is not accessible because of security checks applied to that route within the body of the controller action implementation, the user can just access /OData/Projects(5)?$expand=Employees($expand=SalaryInfo).
There doesn't seem to be any way to block this that I've found, other than blocking navigation properties altogether via MaxExpansionDepth.
What would be ideal is if, since the OData EDM already knows about entities and the Web API routes they're associated with, therefore all navigation properties could be set up to be fed through the existing OData Web API controller action for that entity. In other words, it would be ideal if /OData/Projects(5)?expand=Employees($expand=SalaryInfo) was handled by OData itself to "join" to /OData/Employees/ on /OData/Projects(5) and then to /OData/Employees/Salary, using those contoller actions, rather than through a SQL join via EF, just by nature of the fact that the EDM knows that those entities map to those routes. This way we can define our authorization logic in exactly one place (controller actions) while still enjoying the $expand syntax flexibility. Am I hoping for something stupidly unreasonable?
I've seen this solution but then the problem becomes we would have separate definitions of security, unless the definition of security in that solution itself invokes the action, even then it's only a blocker and not a conditional data filter as we have implemented.
If not, we will have to settle for peppering [Queryable(MaxExpansionDepth = 0)] on every single vulnerable API endpoint in our system.
Related
I have been looking at BreezeJS and I want to try it but I searched a lot and still cannot understand how security is handled while using Breeze. Here is what I know:
According to a post on IdeaBlade forums (creators of BreezeJS), we only need a single Api Controller for all of our entities. The Api controller will contain one MetaData method, one Get method for each entity, one Save method, one Delete method. So this way we only need one EntityManager on client side configured with one service endpoint.
My questions:
My understanding of "single controller for all entities" is correct?
If my understanding is correct then how can we apply security on our controller? If I want a user with certain role to access only certain entities, I obviously cannot put an Authorize filter on my controller or method. May be I want a certain user to have read-only access while other users having read-write access on a certain entity. May be I only want to return aggregated data to user while restricting access to full details.
Please help. Thanks.
I've been doing a lot of tutorials for different MVC frameworks, and it seems very typical for Authorization to take place in the Controller. Why?
My thought is the Controller should only be used to orchestrate Model actions, to handle redirection and to handle error events. These are the things that are dependent on the specific request. Putting Authorization in the Controller seems like you're going to have to duplicate the authorization whenever you're using the same Model action in different Controller actions or different Controllers. If Auth is in the Model, you have consistent requirements for carrying out an action or state change on the data.
I've been googling and looking at other questions such as Should authorization be part of the model or controller? but I don't really see why it's the accepted convention.
Is there a specific reason I'm missing for putting Authorization in the controller over the model?
To sum up points in the comments:
Controllers are responsible for altering the state of the model layer and the current view. Nothing else.
Authorization belongs where an action is being carried out, if you're following a strict MVC pattern this would most likely be the model, and a Controller is certainly not responsible for authorizing the use of model actions.
Cookies should be treated like any other datastore: abstracted and used within the models, not directly by controllers.
Authentication and Authorization are separate issues, though they both usually go in the model layer, because they usually involve checks against values in datastores (such as cookies).
Is there a specific reason I'm missing for putting Authorization in the controller over the model?
Well, the most common reason I can imagine is laziness. I don't mean that morally, it's just far easier to flunge some authorization concept on top into a layer that is more close to the concrete request then to have differentiated access on the model layer. To have authorization with the models is a much higher design.
To add some more practical advice to the answer, I think you should analyse for each program where and for what you would want to introduce authorization. The needs for that can be (extremely) different.
Then only in the next step you should think about which design is most beneficial to introduce authorization and authentication to fulfill these needs.
In an MVC approach, you need to put security in a location where:
it cannot be circumvented
it can be configured, managed and updated easily
This applies - as a matter of fact - to any architecture / type of application.
Specifically, in MVC, imagine you put authorization in the view. For instance you decide to control who can approve a transaction by enabling / disabling a button. A user of your view will not be able to approve a transaction if he/she is not allowed. Imagine now that you expose your controller over an API rather than a view. The approve authorization check now needs to be reimplemented in the API layer.
This example shows you are better off moving authorization away from the view / the different end-points and into a common, central point - your controller.
Similarly, if you want to control access to large sets of data (e.g. medical records), you ideally want to put the authorization in the model. This is both for performance reasons and for security reasons: you'd rather have the controller handle less data and you should always strive to protect as close as possible to the source of the sensitive data.
Note that having authorization hooks / checks in the view, controller, and model at the same time may lead to an altogether enhanced experience. See authorization in the view as a "safety / usability" mechanism whereby a user is only presenetd with those relevant menus and widgets on screen based on their permissions. If they were malicious and knew their way around the UI to the controller, authorization there would still kick in.
Finally, generally speaking, you want to decouple non-functional requirements / logic from functional requirements / logic. Much like you do not implement logging in code but use a configurable framework (e.g. Log4J) or you rely on the container for authentication (e.g. HTTP BASIC in Apache Tomcat), you want to use an externalized authorization framework such as Claims-based authorization in the Microsofct MVC4 world, Spring Security in Java, CanCan in Ruby, or XACML, a standard part of the same body as SAML (OASIS) and which will let you apply authorization to any type of application and any layer.
Authorization as an entire process should be involved in both: Controller and Model layers.
But, all the logc (SQL queries, etc) should definitely happen in the model.
Controller is kind of an intermediate layer between the view (representation) and the Model.
But, you simply cannot throw away the Controller from this scheme, because Controller is responsible for handling Sessions and Cookies. Without these two things all your Authentication/Authorization logic is useless, because it is stateless by its nature. Sessions and Cookies bring state to it.
Moreover, as you correctly mentioned, Controller is responsible for redirects.
I'm developing a fairly standard web application with Wicket, Spring & Hibernate. I've been using wicket-auth-roles and spring-security to authenticate users, and now want to add more fine grained authorizations to my applications.
In my applications users are members of groups, and groups have access to a subset of Hibernate objects that I use as wicket IModel objects. As such the decision whether or not a user may view certain page does not depend on the page path, but on the page model. (Most implementations of authorization for Wicket I've seen either grant access to a url or restrict it; they do not perform any checks on the model object.)
At present I've implemented this restriction as a custom IAuthorizationStrategy like this:
#Override
public boolean isActionAuthorized(final Component component, final Action action) {
if (!(component instanceof GenePage))
// We only check access to the GenePage for now
return true;
// Figure out from component what Gene the user is trying to view
Gene gene = (Gene) component.getDefaultModelObject();
User user = MySession.get().getUserModel().getObject();
return geneDAO.hasAccess(user, gene);
}
The problem with this implementation is that it fully composes the page and only in Page#onConfigure throws an uncaught UnauthorizedActionException. So far I've been unable to catch this exception, so it's logged as a problem even though it's part of the normal program flow. Fully composing the page also triggers a few actions in my page constructor and Page#onInitialize that I would only like to run if the user may actually view the Page.
Can anyone recommend me a better approach to restrict page access based on whether users have access to the Model object?
Solutions that tie in anywhere along the stack using Hibernate, Spring, Spring Security, Wicket and/or Wicket-Auth-Roles would be preferred. I know there are other wicket auth-integrations out there, so if you feel those could help in this instance, please let me know!
I feel that you expect a weird behaviour. This authz mechanism is designed to protect against Insecure Direct Object Reference Vulnerabilities. So you should not use it as a "part of the normal program flow". If you have kind of valid use cases then such kind of "hasAccess" failures should be handled somehow differently as valid behaviour, you should use some other mechanism, probably something custom built, as in most cases it will be very specific to your application.
We have Implemented REST Based Architecture for our ASP.NET MVC3 App.
We are pondering over the architectural decision to implement a custom Authorization for the contracts we are exposing through our service.
e.g. Any valid authenticated user may get access to a particular Method implementation of the contract and might want to access some other user's info (getting a list of items from the data through Stored Proc) , we need to check after we get back this Items list that whether this authenticated User has proper permissions to access this. The permission check is based on a heavy business logic , hence Attribute based authorization might not be helpful in this scenario as only after getting back the data we might decide the access permission check.
Please advice how to implement this security model inside our REST Service.
Since attribute based auth seemingly won't work for you, then you'll need to determine if they fit the role you need:
HttpContext.Current.User.IsInRole()
After that your controller simply returns an HttpUnauthorizedResult which is an ActionResult.
So check your business logic, if they aren't authorized, then return HttpUnauthorizedResult and you are done.
http://msdn.microsoft.com/en-us/library/system.web.mvc.httpunauthorizedresult.httpunauthorizedresult(v=vs.98).aspx
I'm writing a web application with some ACL requirements: a user can make changes to some items, some items may be editable by several users, administrator can edit anything and a manager can edit everything within her organization etc.
I'm using the Play! framework, and by the looks of the Secure module, it seems that the place to put authorization concerns is in the Controllers. However, it seems to me that the authorization issues are part of the business logic, and therefore should be in the model. Furthermore, I'm starting to see duplicated logic in the controllers that I need to refactor out.
On the other hand, adding authorization to the model means that I'd have to have some way of getting the current user from within the model, which doesn't seem right. Alternatively, I could add a "current_user" parameter to every model method, but that seems even worse.
So what is the common practice? Can/should I put authorization code in the model, or keep it in the controller?
I think this is a grey area. One could argue that the user access is part of the mapping between the HTTP world and the Object-Oriented world. This is what the controller is intended for (hence the heavy use of statics), to transform the incoming request, ready to process the business rules on the domain model.
I would suggest that the controller logic is absolutely the right place for controlling the access to the model, especially as this is managed largely at an annotation level, and the authentication is abstracted off to a Security class.
Authorization should neither be part of controller or domain model.
Instead it should be in the service layer.
Controller should just act as dispatcher and delegate between HTTP and application service.
It's the application service where the orchestration takes place. This is the best place for placing authorization.
Suppose user A is authorized to access data from domain X, but not authorized for even a read access for data from domain Y. If authorization is placed in the controller, then user A gets authorized in the controller X, and via the service calls can access data from domain Y, which is not what we expected.
Since domain models communicate with each other on service layer, hence it best to place the authorization on the same level.
In most cases, the security should be one (or more) layer above the Model. Security is a domain on it's own, restricting access to a lower level layer.
I don't think the security should be done at the controller level.
In my opinion, this should look like that:
View -> Controller -> Security -> Model
The security layer could be a façade or a proxy over the model, protecting access, but be transparent to the controller.
However, if the views are to be modified depending on the access rights of the user, some checks might have to happen at the controller level (like setting the value of a CanEdit boolean property on the ViewModel).
I personally really like the way the Play! Secure module handles this (the tutorial is ever-helpful here). If you don't mind using the #Before annotation, it's pretty painless.
I am at this stage and intending to handle this in the following way:
No form validation by JS, instead via HTTPS ajax
An Ajax php class
Form data sent to a model as its data for concrete validation for
common type such as email and password (likely assoc array validation will be reused by other classes so this is definately a model area).
if no error a lookup in a User table for the credentials email /
password credentials passed to a Controller with the authentication
type such as login / signup / password reset
the controller then produces the required output view or sets user logged in session etc
This is based in Laravel but I have my own library as want it independent of laravel and just loosely based for this vital requirement.
The point being that the Model looks up the required credentials as data, then sends to the Controller as it does not care how it should be processed. I think this is the only way to make this area a definitive responsibility between each of the components.
From my personal experience with MVC frameworks I would say:
Model is an object that is representing database table it should be
pure and should not contain any additional logic.
Controller is the place where are made the decisions and other
custom logic, so the authorization should be in the controller. It
could be designed some hook that can check if the user is authorized
or not in all needed places so you wont have a code repetition DRY.
The best way to give permission to user if you are using a typical
REST architecture is to make a token , save it in the databse and on
client side and verify this token on every request. If you are using
web browser app you can use server-side sessions for authorization (
Its much more easier).
So my propose is to keep the authorization logic in the Controller.
I'll use Rails as an example. The authorization library, pundit, places authorization firmly within the "model" domain - this is enforced through their helper methods.
Suppose you have a ShoppingBag model. You might want to create a ShoppingBag
class ShoppingBagController
def create
authorize ShoppingBag.new, current_user
end
end
It works really well if you have a 1-1 mapping between a model and a controller. But what if you need a second controller on the same model? Now you're stuck!
class DiscountedShoppingBagController
def create
authorize ShoppingBag.new, current_user # does not work for us. we want a slightly different authorization, on the same model.
end
end
It's for that reason I dislike pundit, and CanCanCan. Authorization at the controller level, for me, is ideal. Doing so on the model level limits me too much, without any commensurate gain.