If I disable anonymous browsing of an MVC site and only allow NTLM authenticate users access, I presume any page simply decorated with the
[Authorize]
attribute will pass, so if I want to only allow user limited access to parts of the site, I'll need to do add them to an AD group and use that to apply the filter?
[Authorize] by default will only look for IsAuthenticated flag. So yes, applying[Authorize] without additional param will allow all logged in users.
To limit, you can use Roles/Group (NOT OUs). It will check the IsInRole (from IPrincipal).
Related
I would like to know that how [Authorize] attribute recognize that this user is authenticate?
If user is valid then we call FormsAuthentication.SetAuthCookie() method and as per MSDN this method:
Creates an authentication ticket for the supplied user name and adds it to the cookies collection of the response, or to the URL if you are using cookieless authentication.
Is [Authorize] attribute checks authentication ticket or cookies collection?
[Authorize] does not deal with any authentication mechanism itself. It merely looks in the users IIdentity for the IsAuthenticated flag. It will also look in the users IsMemberOf method, for authorization based on roles.
All the work to decode the authentication ticket is done in the early stages of the app pipeline, which sets those flags. By the time the Authorization Attribute methods are called, all that work has already been done and is stored in the users runtime data.
You can easily check the source code for the Authorize attribute, and you will see that it's quite simple in nature. It just returns true or false based on some simple lookups.
It's become more complicated in .net core, where it's based on policies and what not, but the original MVC implementation was quite simple.
My answer relates to ASP.NET Core I'm not sure if you asked about classic ASP.NET but this should be similar.
There's a middleware that you have to add for [Authorize] to work. ASP.NET Core provides this middleware out of the box and you can add your custom authentication handlers too.
You can check how it's implemented by reading: https://github.com/aspnet/Security/tree/dev/src
For example you want to use JWT bearer authentication, you have to add JWT bearer middleware, this is simply extension of AuthenticationBuilder: https://github.com/aspnet/Security/blob/dev/src/Microsoft.AspNetCore.Authentication.JwtBearer/JwtBearerExtensions.cs which calls AddScheme under the hood.
You want to use cookie based authentication you just call AddCookie which is also extension that calls AddScheme under the hood: https://github.com/aspnet/Security/blob/dev/src/Microsoft.AspNetCore.Authentication.Cookies/CookieExtensions.cs
Usage of it is documented here: https://learn.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/identity-2x?view=aspnetcore-2.1
See also Using the [Authorize] Attribute
Web API provides a built-in authorization filter, AuthorizeAttribute. This filter checks whether the user is authenticated. If not, it returns HTTP status code 401 (Unauthorized), without invoking the action.
If you are interested how this filter works under the hood you can check it here.
You must be authenticated before you can be authorized, this is the logic responsible for it: https://github.com/aspnet/Security/blob/644f34e90d35b369efdce9c11ab1db42e0a7f4a7/src/Microsoft.AspNetCore.Authorization.Policy/PolicyEvaluator.cs#L91
In summary
how [Authorize] attribute knows that this user is authenticated.
Authorize attribute alone doesn't know if this user is authenticated. This is handled by authentication middleware and depends stricly on the scheme it tries to authenticate with. It simply tries to authenticate with schemes you have added(cookie,jwt etc.) by calling HttpContext.AuthenticateAsync which is simply calling AuthenticationService.AuthenticateAsync under the hood and sets HttpContext.User from the result ClaimsPrincipal, which is simply result from schema handler like jwt handler for instance. I think this should give you more in-depth idea how this works.
Generally if you're starting new project I don't recommend using classic ASP.NET and prepare for the future with .NET Core as everything is now going in this direction. ASP.NET 5 ( I also refer to it as "classic") is pretty much dead now.
I have gone through many blog articles describing how to validate users in our web applications using [ValidateAntiForgeryToken] attribute. But this has limitations such as can be used only with HTTPPOST methods. My requirement is I have a MVC 5 application which returning sensitive data (Ex: bank statements) using HTTPGET methods. How to authorize/protect these action methods from anonymous users ?.
I want to write a token based authorization mechanism.
You are correct - the ValidateAntiForgeryToken mitigates against Cross-Site-REquest-Forgery (CSRF). It is specific to POST's, as it can correlate the a response issued by a server, and the HTML posted from a user. There is no concept of CSRF for GETs.
To protect GETS from anonymous users, use the [Authorize] attribute on any methods that you require users to be logged into the websites. If they are not, they will be redirected to the login section, as configured in your web.config.
I have a ASP.NET MVC website.
I don't really manage users, but I do a login to an external API and then I store a "ASPXFORMSAUTH" cookie.
It's a WCF service. In my controller, I call :
MyWcfServiceClient.Login()
In the AfterReceiveReply, I store the response of the service in a variable :
cookie = httpResponse.Headers[HttpResponseHeader.SetCookie];
Then In the controller, I get this cookie and store it using :
Response.Cookies.Add(cookie);
I'm a beginner with ASP.NET MVC, but can I use the [Authorize] attribute to allow the access to the controllers methods only if the request contains this cookie ? And [AllowAnonymous] on the methods before the API login.
EDIT :
So it should work just adding the [Authorize] attribute ?
I'm calling the controller method using ajax, and the value of Request.Headers["Cookie"] is .ASPXAUTH=1D415AF723......
But I get the ajax error callback...
Am I missing something ?
[Authorize] will allow access to authorized users only.
You can either put it at the top of the controller so it applies to all functions on the controller or in front of individual functions. its more powerful than that though as you can allow only specific users or roles. documentation here
The allow [AllowAnonymous] is used when you have added some sort of Authorize to the whole controller but want to allow access for all to a function on the controller. its not required if the controller doesn't have an authorize attribute on it. example here I think the default MVC account in visual studio uses this on the account controller for password rest and login.
I'm not fully sure since I haven't tried it before. But if you set the correct cookies (the default aspx auth cookie) the AuthorizeAttribute should prevent you from reaching the controller if you aren't authorized. Have you tried using the authorize attribute on a controller and logging in using your external API? Because it might just work out of the box.
Another option is to extend the default attribute by making your own. See the following articles for more information about this.
Article from John Galloway
Another question here on SO about extending the Authorize attribute
MSDN Article about the Authorize attribute
I have some intranet asp.net mvc3 app ,which is available for both LDAP authenticated and anonymous users.All of them are using IE. One of the views should be available for both of them, depending on status some columns should be hidden,etc.
I don't want anonymous users to receive popup authentication dialog,but can't see no way of solving problem.If I add Authorize() attribute ,it forces anonymous user to input user/password, if I remove this attribute everyone is treated as anonymous.
How can be this obstacle solved?
In your controller check to see if the user is authenticated and perform actions based off that conclusion.
if (User.Identity.IsAuthenticated){
//Handle Case
}
I'm reading up on ASP .NET MVC, and I just got to a section talking about the Authorize attribute. It's saying that the Authorize attribute is used to check that a user is authenticated against a Controller. Is this true? I know that the attribute is designed to be used for authorization purposes, but is it also a best practice to use this attribute for authentication?
If not, what is the best practice for verifying (not performing) authentication?
If so, why is it done this way? Am I missing something?
Authorize attribute can be used to check to see whether the user is logged in. It can also be used to check if the user is a member of a specific role and has a specific name.
It essentially does the same thing handled by <authorization> section in web.config when using Web forms.
It doesn't specify the authentication method. It's handled by <authentication> section in web.config just like Web forms.
EDIT (clarification about authentication and authorization):
Authentication is identity verification. That is, you check to see who the user is. This can be performed by checking a user name and password, checking your Windows authentication token, scanning retina, voice identification or whatever else.
Authorization is the act of limiting access to a specific resource to users that satisfy a certain criteria. To be able to authorize a user to a resource, you should know the rights the user have. To check that, you should know who the user is in the first place. So the user have to be authenticated.
Essentially an empty [Authorize] attribute does authorization, not authentication. It doesn't check who you are. It just checks if the one who you verified to be does have access to the resource or not. However, its authorization criteria is "anyone successfully authenticated." You can specify a different criteria. So, indeed it's doing authorization, not authentication.
Authorize does indeed check that the user is authenticated, otherwise it would not be able to determine the roles for the user or which user (other than the anonymous one) the current user is. That is, in order to be authorized, if anonymous access is not allowed, you have to be authenticated first. Below is the relevant snippet from the AuthorizeCore method in the RTM version (from http://www.codeplex.com/aspnet).
// This method must be thread-safe since it is called by the thread-safe OnCacheAuthorization() method.
protected virtual bool AuthorizeCore(HttpContextBase httpContext) {
if (httpContext == null) {
throw new ArgumentNullException("httpContext");
}
IPrincipal user = httpContext.User;
if (!user.Identity.IsAuthenticated) {
return false;
}
...
If AuthorizeCore returns false in OnAuthorization, then the AuthorizationContext.Result is set to a new HttpUnauthorizedResult which will result in the user being redirected to the login page (in FormsAuthentication) or an error.
EDIT: After reading your comments to other answers, I would say that you ARE missing the point. Technically it is only doing authorization. One level of authorization, the minimum, is that you need to be authenticated to perform an action. You get this by not specifying any users or roles for the Authorize attribute. Any user or role is allowed, as long as it is authenticated. By specifying users and/or roles that act as filters you narrow down the scope of the action and the user needs not only be authenticated (so you can check the name/role membership), but also qualify based on the filter.
Authentication and Authorization are two different concerns.
Authentication verifies that the user is who he says he is, almost always done in most web apps by verifying that he/she has some knowledge (like a password) that only he/she should know.
Authorization verifies that an authenticated user has the permissions to do something. Only administrators can access admin pages for instance.
Since we can get the roles of a person only once logged in, it is possible to use the Authorize attribute to test for authentication.
Take a look at this blog post and see how the author implements both a custom Authorize and Authentication attribute:
Securing your controller actions
You'll see that the Authorize attribute has to check for authentication, since only authenticated users can have a role.