I've got a situation where I use multiple authorization filters to enforce different conditions independent of one another:
<UserLevelCanAccessThings>
<UserHasPaidForThings>
Partial Public Class ThingsController
Inherits Controller
Function EditThing() As ActionResult
...
Return View()
End Function
<OverrideUserIsPaid>
Function PayToUnlockThings() As ActionResult
...
Return View()
End Function
End Class
Now I've got a situation where I need to have an action bypass only one of the filters. For instance, suppose you're allowed to access this controller to work with Things if you've achieved a high enough level (first filter) and you've then paid for that access (second filter).
The Pay method needs to enforce the first condition but NOT the second, because I don't want to block the user from paying because he's not paid when he's trying to pay!
(I know I could move the Pay method somewhere else, but in my actual situation this isn't desirable. This is just an example to illustrate what I'm asking.)
A global OverrideAuthorization attribute turns off ALL authorization, but I need to be more selective about it. How can I do that?
Following this answer by Darin, I did this:
Public Class OverrideUserIsPaidAttribute
Inherits AuthorizeAttribute
Public Overrides Sub OnAuthorization(filterContext As AuthorizationContext)
'no op
End Sub
End Class
Public Class UserIsPaidAttribute
Inherits AuthorizeAttribute
Public Overrides Sub OnAuthorization(filterContext As AuthorizationContext)
'get all other filters attached to this action, controller, or globally
Dim otherFilters = filterContext.ActionDescriptor.GetCustomAttributes(True).AsEnumerable '.Where(Function(x) TypeOf x Is IAuthorizationFilter And Not TypeOf x Is OverridePlayerIsPaidAttribute).AsEnumerable(Of IAuthorizationFilter)()
otherFilters = otherFilters.Union(filterContext.ActionDescriptor.ControllerDescriptor.GetCustomAttributes(True))
otherFilters = otherFilters.Union(GlobalFilters.Filters.Select(Function(x) x.Instance))
'if any of them is an override, bail out before validating
If otherFilters.OfType(Of UserIsPaidAttribute).Count > 0 Then Return
'regular validation here
End Sub
Basically, it enhances the UserIsPaid authorization to check the attributes of the action, the controller, and global filters to see if there is an override specified, and, if so, simply doesn't do its own authorization. This seems clean enough to me, but I'm open to suggestions.
I have a requirement to encapsulate pieces of business logic within a transaction in an OData Web API service. Some of these pieces will need to accept one or more entities.
An example use case might be StockProduct and this might accept a Product entity and a Location entity. It would create the product and update stock records for the Location.
The approach I've taken is to create an unbound OData action that accepts these entities so that both of these can be operated on in a single transaction. Unfortunately neither can Entities be used as an ODataActionParameter nor can they be part of a class and used as a complex parameter.
I can think of a two ways around this:
Create a DTO class that is not an entity that is a mirror of each of my mirror classes and convert from DTO to Model within my action. The problem here is that I already have a DTO for each Model eg. Product.cs and ProductDTO.cs and don't really want to have to create a third class. (Currently, the ProductDTO.cs is used for Posts, Puts, Patches and Deletes and the Product.cs is used for Gets).
Abandon OData actions and create a simple end point that accepts whatever I like. I'm not keen on going down the second route as I'd like to use OData exclusively.
Any thoughts or suggestions?
You can use the ActionConfiguration.EntityParameter() method to bind an entity as a parameter to your OData action method.
Here is an example:
ActionConfiguration validate = ModelBuilder.EntityType<TEntity>()
.Collection.Action("Validate");
validate.Namespace = "Importation";
validate.EntityParameter<TEntity>(typeof(TEntity).Name);
validate.CollectionParameter<string>("UniqueFields");
validate.Returns<ValidationResult>();
However, note that the ModelState will not check against the content of the supplied Entity and will set any missing properties to null and properties exceeding the StringLength(x) annotation in your model will still pass. If you wish to validate the entity itself after, use this bit of code in your action method:
[HttpPost]
public virtual IHttpActionResult Validate(ODataActionParameters parameters)
{
//First we check if the parameters are correct for the entire action method
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
else
{
//Then we cast our entity parameter in our entity object and validate
//it through the controller's Validate<TEntity> method
TEntity Entity = (TEntity)parameters[typeof(TEntity).Name];
Validate(Entity, typeof(TEntity).Name);
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
IEnumerable<string> uniqueFields = parameters["UniqueFields"] as IEnumerable<string>;
bool result = Importer.Validate(Entity, uniqueFields);
return Ok(result);
}
}
As for your StockProductDTO, it seems to me that this is an new Business Entity by itself and should be treated as such.
You can use a batch request to perform multiple operations within a single request. This allows you to use your existing controllers for inserting your two objects.
https://aspnetwebstack.codeplex.com/wikipage?title=Web+API+Request+Batching
I have an asp.net mvc app which has membership implemented.
So a user has to log in. Each user belongs to a organisation (multi-tenancy).
How would I handle the organisation parameter globaly? I was thinking this could be a good thing for a global filter because all the data needs to be filtered for the given organisation. And the organisation is connected with the username but not in the same table.
for example I have a index action like this
public ActionResult Index()
{
var result = _repository.GetListByOrganisation(organisation);
return View(result);
}
I was thinking about having a global attribute thats queries the db for an organisation based on a giving username. Since my controller already contains the authorize attribute I have the user name. It would be nice to cache the organisation (session, controllercontext) and not query the organisation from db on each request.
Is this a way to implement something like this? Or are there other ways which would be better? And how can I set a property on the controller / controllercontext from whithin a filter?
So any thoughts on this as well as comments would be great...
I would do this via DI.
You can use either a third-party DI container or your own code. Either way, you want to set the organization ID on a per-request basis.
So you'll be creating a unit of work and injecting that in your controller. For the sake of simplicity, let's pretend that your unit of work is the _repository field in your sample code, even though most real-world apps are more complex.
You add a constructor parameter to the controller:
public FooController(IFooRepository repository)
{
this._repository = repository;
}
...and an organization ID on FooRepository:
public class FooRepository: IFooRepository
{
public FooRepository(long organizationId)
{
this._organizationId = organizationId;
}
}
Now in either your DI container setup or a MVC controller factory, you set this all up:
builder.Register(c => new FooRepository(GetOrgIdForCurrentUser()).As<IFooRepository>();
builder.Register(c => new FooController(c.Resolve<IFooRepository>());
Perhaps you could have the organization embedded on the URL, for example if your route looks like this /{organization}/{controller}/{action}
then you'll get URLs like
/bigorg/products/list
/smallorg/products/list
and you'll receive the organization in your controller either a parameter to your method or via the RouteData object.
Preamble: this is a bit of a philosophical question. I'm looking more for the "right" way to do this rather than "a" way to do this.
Let's imagine I have some products, and an ASP.NET MVC application performing CRUD on those products:-
mysite.example/products/1
mysite.example/products/1/edit
I'm using the repository pattern, so it doesn't matter where these products come from:-
public interface IProductRepository
{
IEnumberable<Product> GetProducts();
....
}
Also my Repository describes a list of Users, and which products they are managers for (many-many between Users and Products). Elsewhere in the application, a Super-Admin is performing CRUD on Users and managing the relationship between Users and the Products they are permitted to manage.
Anyone is allowed to view any product, but only users who are designated as "admins" for a particular product are allowed to invoke e.g. the Edit action.
How should I go about implementing that in ASP.NET MVC? Unless I've missed something, I can't use the built-in ASP.NET Authorize attribute as first I'd need a different role for every product, and second I won't know which role to check for until I've retrieved my Product from the Repository.
Obviously you can generalise from this scenario to most content-management scenarios - e.g. Users are only allowed to edit their own Forum Posts. StackOverflow users are only allowed to edit their own questions - unless they've got 2000 or more rep...
The simplest solution, as an example, would be something like:-
public class ProductsController
{
public ActionResult Edit(int id)
{
Product p = ProductRepository.GetProductById(id);
User u = UserService.GetUser(); // Gets the currently logged in user
if (ProductAdminService.UserIsAdminForProduct(u, p))
{
return View(p);
}
else
{
return RedirectToAction("AccessDenied");
}
}
}
My issues:
Some of this code will need to be repeated - imagine there are several operations (Update, Delete, SetStock, Order, CreateOffer) depending on the User-Products relationship. You'd have to copy-paste several times.
It's not very testable - you've got to mock up by my count four objects for every test.
It doesn't really seem like the controller's "job" to be checking whether the user is allowed to perform the action. I'd much rather a more pluggable (e.g. AOP via attributes) solution. However, would that necessarily mean you'd have to SELECT the product twice (once in the AuthorizationFilter, and again in the Controller)?
Would it be better to return a 403 if the user isn't allowed to make this request? If so, how would I go about doing that?
I'll probably keep this updated as I get ideas myself, but I'm very eager to hear yours!
Thanks in advance!
Edit
Just to add a bit of detail here. The issue I'm having is that I want the business rule "Only users with permission may edit products" to be contained in one and only one place. I feel that the same code which determines whether a user can GET or POST to the Edit action should also be responsible for determining whether to render the "Edit" link on the Index or Details views. Maybe that's not possible/not feasible, but I feel like it should be...
Edit 2
Starting a bounty on this one. I've received some good and helpful answers, but nothing that I feel comfortable "accepting". Bear in mind that I'm looking for a nice clean method to keep the business logic that determines whether or not the "Edit" link on the index view will be displayed in the same place that determines whether or not a request to Products/Edit/1 is authorised or not. I'd like to keep the pollution in my action method to an absolute minimum. Ideally, I'm looking for an attribute-based solution, but I accept that may be impossible.
First of all, I think you already half-way figured it, becuase you stated that
as first I'd need a different role for every product, and second I won't know which role to check for until I've retrieved my Product from the Repository
I've seen so many attempts at making role-based security do something it was never intended to do, but you are already past that point, so that's cool :)
The alternative to role-based security is ACL-based security, and I think that is what you need here.
You will still need to retrieve the ACL for a product and then check if the user has the right permission for the product. This is so context-sensitive and interaction-heavy that I think that a purely declarative approach is both too inflexible and too implicit (i.e. you may not realize how many database reads are involved in adding a single attribute to some code).
I think scenarios like this are best modeled by a class that encapsulates the ACL logic, allowing you to either Query for decision or making an Assertion based on the current context - something like this:
var p = this.ProductRepository.GetProductById(id);
var user = this.GetUser();
var permission = new ProductEditPermission(p);
If you just want to know whether the user can edit the product, you can issue a Query:
bool canEdit = permission.IsGrantedTo(user);
If you just want to ensure that the user has rights to continue, you can issue an Assertion:
permission.Demand(user);
This should then throw an exception if the permission is not granted.
This all assumes that the Product class (the variable p) has an associated ACL, like this:
public class Product
{
public IEnumerable<ProductAccessRule> AccessRules { get; }
// other members...
}
You might want to take a look at System.Security.AccessControl.FileSystemSecurity for inspiration about modeling ACLs.
If the current user is the same as Thread.CurrentPrincipal (which is the case in ASP.NET MVC, IIRC), you can simplyfy the above permission methods to:
bool canEdit = permission.IsGranted();
or
permission.Demand();
because the user would be implicit. You can take a look at System.Security.Permissions.PrincipalPermission for inspiration.
From what you are describing it sounds like you need some form of user access control rather than role based permissions. If this is the case then it needs to be implemented throughout your business logic. Your scenario sounds like you can implement it in your service layer.
Basically you have to implement all functions in your ProductRepository from the perspective of the current user and the products are tagged with permissions for that user.
It sounds more difficult than it actually is. First off you need a user token interface that contains the user information of uid and role list (if you want to use roles). You can use IPrincipal or create your own along the lines of
public interface IUserToken {
public int Uid { get; }
public bool IsInRole(string role);
}
Then in your controller you parse the user token into your Repository constructor.
IProductRepository ProductRepository = new ProductRepository(User); //using IPrincipal
If you're using FormsAuthentication and a custom IUserToken then you can create a Wrapper around the IPrincipal so your ProductRepository is created like:
IProductRepository ProductRepository = new ProductRepository(new IUserTokenWrapper(User));
Now all your IProductRepository functions should access the user token to check permissions. For example:
public Product GetProductById(productId) {
Product product = InternalGetProductById(UserToken.uid, productId);
if (product == null) {
throw new NotAuthorizedException();
}
product.CanEdit = (
UserToken.IsInRole("admin") || //user is administrator
UserToken.Uid == product.CreatedByID || //user is creator
HasUserPermissionToEdit(UserToken.Uid, productId) //other custom permissions
);
}
If you wondering about getting a list of all products, in your data access code you can query based on permission. In your case a left join to see if the many-to-many table contains the UserToken.Uid and the productId. If the right side of the join is present you know the user has permission to that product and then you can set your Product.CanEdit boolean.
Using this method you can then use the following, if you like, in your View (where Model is your Product).
<% if(Model.CanEdit) { %>
Edit
<% } %>
or in your controller
public ActionResult Get(int id) {
Product p = ProductRepository.GetProductById(id);
if (p.CanEdit) {
return View("EditProduct");
}
else {
return View("Product");
}
}
The benefit to this method is that the security is built in to your service layer (ProductRepository) so it is not handled by your controllers and cannot be bypassed by your controllers.
The main point is that the security is placed in your business logic and not in your controller.
The copy paste solutions really become tedious after a while, and is really annoying to maintain. I would probably go with a custom attribute doing what you need. You can use the excellent .NET Reflector to see how the AuthorizeAttribute is implemented and perform your own logic to it.
What it does is inheriting FilterAttribute and implementing IAuthorizationFilter. I can't test this at the moment, but something like this should work.
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, Inherited = true, AllowMultiple = true)]
public class ProductAuthorizeAttribute : FilterAttribute, IAuthorizationFilter
{
public void OnAuthorization(AuthorizationContext filterContext)
{
if (filterContext == null)
{
throw new ArgumentNullException("filterContext");
}
object productId;
if (!filterContext.RouteData.Values.TryGetValue("productId", out productId))
{
filterContext.Result = new HttpUnauthorizedResult();
return;
}
// Fetch product and check for accessrights
if (user.IsAuthorizedFor(productId))
{
HttpCachePolicyBase cache = filterContext.HttpContext.Response.Cache;
cache.SetProxyMaxAge(new TimeSpan(0L));
cache.AddValidationCallback(new HttpCacheValidateHandler(this.Validate), null);
}
else
filterContext.Result = new HttpUnauthorizedResult();
}
private void Validate(HttpContext context, object data, ref HttpValidationStatus validationStatus)
{
// The original attribute performs some validation in here as well, not sure it is needed though
validationStatus = HttpValidationStatus.Valid;
}
}
You could probably also store the product/user that you fetch in the filterContext.Controller.TempData so you can fetch it in the controller, or store it in some cache.
Edit: I just noticed the part about the edit link. The best way I can think of is factoring out the authorization part from the attribute and make a HttpHelper for it that you can use in your view.
I tend to think that authorization is part of your business logic (or at least outside of your controller logic anyway). I agree with kevingessner above, in that the authorization check should be part of the call to fetch the item. In his OnException method, you could show the login page (or whatever you have configured in the web.config) by something like this:
if (...)
{
Response.StatusCode = 401;
Response.StatusDescription = "Unauthorized";
HttpContext.Response.End();
}
And instead of making UserRepository.GetUserSomehowFromTheRequest() calls in all the action methods, I would do this once (in an override of the Controller.OnAuthorization method for example), then stick that data somewhere in your controller base class for later use (e.g. a property).
I think that it's unrealistic, and a violation of the separation of concerns, to expect to have controller/model code control what the view renders. The controller/model code can set a flag, in the view model, that the view can use to determine what it should do, but I don't think that you should expect a single method to be used by both controller/model and view to control both access to and rendering of the model.
Having said that you could approach this in either of two ways -- both would involve a view model that carries some annotations used by the view in addition to the actual model. In the first case, you can use an attribute to control access to the action. This would be my preference, but would involve decorating each method independently -- unless all of the actions in a controller have the same access attributes.
I've developed a "role or owner" attribute for just this purpose. It verifies that the user is in a particular role or is the owner of the data being produced by the method. Ownership, in my case, is controlled by the presence of a foreign key relationship between the user and the data in question -- that is, you have a ProductOwner table and there needs to be a row containing the product/owner pair for the product and current user. It differs from the normal AuthorizeAttribute in that when the ownership or role check fails, the user is directed to an error page, not the login page. In this case, each method would need to set a flag in the view model that indicates that the model can be edited.
Alternatively, you could implement similar code in the ActionExecuting/ActionExecuted methods of the controller (or a base controller so that it applies consistently across all controllers). In this case, you would need to write some code to detect what kind of action is being executed so you know whether to abort the action based on the ownership of the product in question. The same method would set the flag to indicate that the model can be edited. In this case, you'd probably need a model hierarchy so you could cast the model as an editable model so that you can set the property regardless of the specific model type.
This option seems more coupled to me than using the attribute and arguably more complicated. In the case of the attribute you can design it so that it takes the various table and property names as attributes to the attribute and uses reflection to get the proper data from your repository based on the attribute's properties.
Answering my own question (eep!), Chapter 1 of Professional ASP.NET MVC 1.0 (the NerdDinner tutorial) recommends a similar solution to mine above:
public ActionResult Edit(int id)
{
Dinner dinner = dinnerRepositor.GetDinner(id);
if(!dinner.IsHostedBy(User.Identity.Name))
return View("InvalidOwner");
return View(new DinnerFormViewModel(dinner));
}
Asides from making me hungry for my dinner, this doesn't really add anything as the tutorial goes on to repeat the code implementing the business rule immediately in the matching POST Action Method, and in the Details view (actually in a child partial of the Details view)
Does that violate SRP? If the business rule changed (so that e.g. anyone who had RSVP'd could edit the dinner), you'd have to change both GET and POST methods, and the View (and the GET and POST methods and View for the Delete operation too, although that's technically a seperate business rule).
Is pulling the logic out into some kind of permissions arbitrator object (as I've done above) as good as it gets?
You're on the right track, but you can encapsulate all of the permission check into a single method like GetProductForUser, which takes a product, user, and the required permission. By throwing an exception that's caught in the controller's OnException handler, the handling is all in one place:
enum Permission
{
Forbidden = 0,
Access = 1,
Admin = 2
}
public class ProductForbiddenException : Exception
{ }
public class ProductsController
{
public Product GetProductForUser(int id, User u, Permission perm)
{
Product p = ProductRepository.GetProductById(id);
if (ProductPermissionService.UserPermission(u, p) < perm)
{
throw new ProductForbiddenException();
}
return p;
}
public ActionResult Edit(int id)
{
User u = UserRepository.GetUserSomehowFromTheRequest();
Product p = GetProductForUser(id, u, Permission.Admin);
return View(p);
}
public ActionResult View(int id)
{
User u = UserRepository.GetUserSomehowFromTheRequest();
Product p = GetProductForUser(id, u, Permission.Access);
return View(p);
}
public override void OnException(ExceptionContext filterContext)
{
if (typeof(filterContext.Exception) == typeof(ProductForbiddenException))
{
// handle me!
}
base.OnException(filterContext);
}
}
You just have to provide ProductPermissionService.UserPermission, to return a user's permission on a given product.By using a Permission enum (I think I've got the right syntax...) and comparing permissions with <, Admin permissions imply Access permissions, which is pretty much always right.
You can use a XACML based implementation. This way you can externalize authorization and also have a repository for your policies outside of your code.
Let’s say I'm developing a helpdesk application that will be used by multiple departments. Every URL in the application will include a key indicating the specific department. The key will always be the first parameter of every action in the system. For example
http://helpdesk/HR/Members
http://helpdesk/HR/Members/PeterParker
http://helpdesk/HR/Categories
http://helpdesk/Finance/Members
http://helpdesk/Finance/Members/BruceWayne
http://helpdesk/Finance/Categories
The problem is that in each action on each request, I have to take this parameter and then retrieve the Helpdesk Department model from the repository based on that key. From that model I can retrieve the list of members, categories etc., which is different for each Helpdesk Department. This obviously violates DRY.
My question is, how can I create a base controller, which does this for me so that the particular Helpdesk Department specified in the URL is available to all derived controllers, and I can just focus on the actions?
I have a similar scenario in one of my projects, and I'd tend to use a ModelBinder rather than using a separate inheritance hierarchy. You can make a ModelBinder attribute to fetch the entity/entites from the RouteData:
public class HelpdeskDepartmentBinder : CustomModelBinderAttribute, IModelBinder {
public override IModelBinder GetBinder() {
return this;
}
public object GetValue(ControllerContext controllerContext, string modelName, Type modelType, ModelStateDictionary modelState) {
//... extract appropriate value from RouteData and fetch corresponding entity from database.
}
}
...then you can use it to make the HelpdeskDepartment available to all your actions:
public class MyController : Controller {
public ActionResult Index([HelpdeskDepartmentBinder] HelpdeskDepartment department) {
return View();
}
}
Disclaimer: I'm currently running MVC Preview 5, so some of this may be new.
The best-practices way: Just implement a static utility class that provides a method that does the model look-up, taking the RouteData from the action as a parameter. Then, call this method from all actions that require the model.
The kludgy way, for only if every single action in every single controller needs the model, and you really don't want to have an extra method call in your actions: In your Controller-implementing-base-class, override ExecuteCore(), use the RouteData to populate the model, then call the base.ExecuteCore().
You can create a base controller class via normal C# inheritance:
public abstract class BaseController : Controller
{
}
public class DerivedController : BaseController
{
}
You can use this base class only for controllers which require a department. You do not have to do anything special to instantiate a derived controller.
Technically, this works fine. There is some risk from a design point of view, however. If, as you say, all of your controllers will require a department, this is fine. If only some of them will require a department, it might still be fine. But if some controllers require a department, and other controllers require some other inherited behavior, and both subsets intersect, then you could find yourself in a multiple inheritance problem. This would suggest that inheritance would not be the best design to solve your stated problem.