I have been implementing Jhipster at my work and loving it. I was asked to implement a security validation that one user should not be allowed to edit the entity created by other user. For this I need two things:
First, in all entities, add a ManytoOne relation with User entity.
In Backend put a validation in controller while updating the entity to check if current logged in user is same as what is stored in DB. In front end also same logic to show/hide edit button.
I have done a POC for this and it works but is little ugly, check the code:
public ResponseEntity<Entry> updateEntry(#RequestBody Entry entry) throws URISyntaxException {
log.debug("REST request to update Entry : {}", entry);
if (entry.getId() == null) {
throw new BadRequestAlertException("Invalid id", ENTITY_NAME, "idnull");
}
//here is my logic
Optional<Entry> entry_db = entryRepository.findOneWithEagerRelationships(entry.getId());
if(!entry_db.get().getUser().getId().equals(userService.getUserWithAuthorities().get().getId())) {
//throw someexception
}
//
Entry result = entryRepository.save(entry);
return ResponseEntity.ok()
.headers(HeaderUtil.createEntityUpdateAlert(ENTITY_NAME, entry.getId().toString()))
.body(result);
}
Is there any better or OOTB way of doing this??? may be something in spring security i am not aware of??
Thanks for help!!
This is a job for Spring Security Expression-Based Access Control, in particular you could annotate your method with #PreFilter and a custom PermissionEvaluator you would implement with similar logic as in your POC. The PermissionEvaluator could be generic and applied to several entity types if you define an Owned interface that models the ownership with a method like User getOwner() and that all your entity classes would implement.
See https://docs.spring.io/spring-security/site/docs/current/reference/html5/#el-access
The annotated method should be in a service rather than in a resource controller.
Also, UserService alone will not help you in finding the current authenticated user, you should use JHipster's SecurityUtils first and then ÙserService if you need more data about it.
SITUATION:
I have a Model and based on a users Role I want to allow the user to only update certain parts of the model. Lets say the Model has three fields. (My Model is obviously more complex than this)
MyObject
Field1
Field2
Field3
My View looks something like this:
Html.TextBoxFor(#Model.Field1)
Html.TextBoxFor(#Model.Field2)
#if(UserIsAdmin())
Html.TextBoxFor(#Model.Field3)
else
#Model.Field3
Bearing with me on the syntax (and the poor design of the example), you can see what I'm trying to do. Upon the user posting the form my controller would just take the MyObject and save it back to the database, we are using EF.
QUESTION:
My question is, is there a way to stop a user from forging a POST to be able to save data he/she should not be able to. My current idea would be to do a check in the controller to see if the user modified values he should not have. Or I could save fields individually, but neither is a convient solution.
Is there a better one?
Thanks!
Additional Info:
Not sure if this artical is relevant at all: http://blog.stevensanderson.com/2008/09/01/prevent-cross-site-request-forgery-csrf-using-aspnet-mvcs-antiforgerytoken-helper/
All three fields are from the same database table and I'm using EF to get and save the entity.
You want to make sure the user is only able to update permitted fields.
You decided that the way to achieve this is to prevent the user "forging" a response using e.g. firebug, or F12 developer tools, or GreaseMonkey, and have asked how to do this.
But the correct/best method is to check which fields the user is attempting to update, and only update those which he is permitted to update. Then it doesn't matter if they forge the request or not, they still won't be able to access anything they shouldn't. In other words, check access rights at the point of access.
Anti-forgery tokens are there to solve a separate problem, namely XSRF.
Use a viewmodel that accepts only the fields that should be updated and then populate the model with those values. You could use something like AutoMapper for mapping between the two.
My current idea would be to do a check in the controller to see if the user modified values he should not have. Or I could save fields individually, but neither is a convient solution.
You're on the right track with that idea. A typical Add() operation would look like this:
public class FooController : Controller
{
public ActionResult Add(FooViewModel viewModel)
{
if (ModelState.IsValid)
{
FooDataModel dataModel = FooMapper.MapToDataModel(viewModel, User);
FooRepository.Add(dataModel);
}
}
}
Like #VimalStan said, your FooViewModel is then a model that contains only the fields you want to let the user update. Also this still doesn't solve your problem, which should be done in your mapper (in this case FooMapper) and still check every field as #Ben suggested:
public static class FooMapper
{
public static FooDataModel Map(FooViewModel viewModel, IPrincipal user)
{
var dataModel = new FooDataModel();
dataModel.Field1 = viewModel.Field1;
dataModel.Field2 = viewModel.Field2;
if (IsAllowedToUpdateField3(user))
{
dataModel.Field3 = viewModel.Field3;
}
return dataModel;
}
public static bool IsAllowedToUpdateField3(IPrincipal user)
{
return false; // your logic
}
}
In my MVC application I have Player and Coach objects, and a user can be one or the other. I also have Team objects and what I want to know is how I prevent a user who is in a list of Players or is the Coach of a Team gaining access to a route like /Teams/Details/2 where 2 is the id of a team other than that which he/she is part of.
Thanks in advance!
Since you want to restrict an id that they aren't a part of, this seems like a situation where you can Inherit from the AuthorizeAttribute and provide your implementation for AuthorizeCore
Your implementation could check their role/team id and decide what to do / redirect.
public class TeamAuthorize : AuthorizeAttribute
{
protected override bool AuthorizeCore(HttpContextBase httpContext)
{
return UserIsInTeam(httpContext); //whatever code you are using to check if the team id is right
}
}
You can now apply it like any other attribute.
[TeamAuthorize]
The very simplest solution would be to change the URLs from using IDs to random GUIDs. You would almost eliminate the chance of someone guessing another valid value. Of course, this is not secure by definition (mostly because someone could get the other URL from history or another source), but in some scenarios this is enough.
A better solution is to create a new attribute based on IActionFilter interface that implements OnActionExecuting method and checks the ID by using this.ControllerContext.HttpContext.User.Identity.Name and this.RouteData.Values["id"]. You will then apply this attribute to your controller methods.
In our current system we implemented row level security in controller methods by just adding the code that verifies the user permissions as the first line in each method. The checking code is the same as with the attribute and it requires the same amount of code to add. This approach has one additional benefit - it is easier to implement scenarios like where a coach would be able to see the details of other teams but not modify them (we have one action and view for both reading and updating depending on permissions).
You would also use the last approach if you need to go to the database to check the permissions and you are using IoC frameworks such as Ninject with constructor based injection - since you will not have access to those values in the attribute.
After a pair programming session, an interesting question came up which I think I know the answer for.
Question: Is there any other desired way in ASP.NET MVC to retain 'state' other than writing to database or a text file?
I'm going to define state here to mean that we have a collection of person objects, we create a new one, and go to another page, and expect to see the newly created person. (so no Ajax)
My thoughts are we don't want any kung-fu ViewState or other mechanisms, this framework is about going back to a stateless web.
What about user session? There are plenty of valid use cases to store things in session. And what about a distributed caching system like memcached? You also seem to leave out the query string - which is an excellent state saver (?page=2). To me those seem like other desirable methods to save state across requests...?
My thoughts are we don't want any kung-fu ViewState or other mechanisms, this framework is about going back to a stateless web.
The example you provided is pretty easy to do without any sort of "view state kung fu" using capabilities that are already in MVC. "User adds a person and sees that on the next screen." Let me code up a simple PersonController that does exactly what you want:
public ActionResult Add()
{
return View(new Person());
}
[HttpPost]
public ActionResult Add(PersonViewModel myNewPersonViewModel)
{
//validate, user entered everything correctly
if(!ModelState.IsValid)
return View();
//map model to my database/entity/domain object
var myNewPerson = new Person()
{
FirstName = myNewPersonViewModel.FirstName,
LastName = myNewPersonViewModel.LastName
}
// 1. maintains person state, sends the user to the next view in the chain
// using same action
if(MyDataLayer.Save(myNewPerson))
{
var persons = MyDataLayer.GetPersons();
persons.Add(myNewPersion);
return View("PersonGrid", persons);
}
//2. pass along the unique id of person to a different action or controller
//yes, another database call, but probably not a big deal
if(MyDataLayer.Save(myNewPerson))
return RedirecToAction("PersonGrid", ...etc pass the int as route value);
return View("PersonSaveError", myNewPersonViewModel);
}
Now, what I'm sensing is that you want person on yet another page after PersonSaveSuccess or something else. In that case, you probably want to use TempData[""] which is a single serving session and only saves state from one request to another or manage the traditional Session[""] yourself somehow.
What is confusing to me is you're probably going to the db to get all your persons anyway. If you save a person it should be in your persons collection in the next call to your GetPersons(). If you're not using Ajax, than what state are you trying to persist?
ASP.NET MVC offers a cleaner way of working with session storage using model binding. You can write a custom model binder that can supply instances from session to your action methods. Look it up.
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.