Force a user to re-enter credentials before submit - asp.net-mvc

Question

Using MVC5, i have an application which a user must be logged into, and then can perform standard actions on some data (create, edit, delete).
I would like to add a credentials prompt, whenever a certain task if performed. So say for example a user is editing a row of data. I want them to be prompted to enter their login credentials again when they hit the Save button, before the row is updated. To be clear, they are ALREADY logged in, i just want to force them to re-confirm their credentials before being allowed to save.
How can i do this in the controller? I want a seperate screen/popup to show, asking for username and password (which will then be checked to ensure correct user credentials) before allowing update of the data.
I looked at creating a new method in the controller, which is passed a username and password, which looks after checking the users credentials again. But how do I go about calling this from the Edit screen, when I also need a popup to appear? Do i go down the route of adding a hidden div on the Edit view, which shows when the user clicks the Save button, and it then calls the method?

Answer 1

Generally, you're expected to attempt a solution, first. Then, if you run into specific issues, you can ask a question about those specific issues. I will tell you that this should be relatively straight-forward. All you need is for the user to re-enter their password. Just add a password input to your edit form and bind it to something on your view model, or you can simply bind it directly to an action parameter, in addition to your view model:
[HttpPost]
public ActionResult MyAction(MyViewModel model, string password)
If you want it to be done in a popup, simply include the popup HTML within the form (so the that the input in the popup will be part of the form) or you'll need to use JavaScript to set another input within the form, which would be bound to either a view model property or action param. Either way, the point is that the password should be posted along with the rest of the form data.
Once inside your post action, you can verify the password by manually:
var user = await UserManager.FindByIdAsync(User.Identity.GetUserId());
var verifyPassword = UserManager.PasswordHasher.VerifyHashedPassword(user.PasswordHash, password);
if (verifyPassword == PasswordVerificationResult.Failed)
{
ModelState.AddModelError("", "Password incorrect.");
// If password is incorrect, ModelState will be invalid now
}
if (ModelState.IsValid)
{
// save posted data
}

Answer 2

It sounds like you'd ideally want an action which you can call asynchronously from the client. While this can take the form of a standard MVC controller action, you may want to consider building this into a Web API controller (Generally we would use Web API controllers to serve up non-HTML responses). You can read more about Web API in many places on the web so I won't go into that now, but let's say you have a HttpResponseMessage result method which looks like this:
[HttpPost]
public HttpResponseMessage CheckCredentials(string username, string password)
{
// Check user credentials and return either one of the following results:
// If credentials valid
return Request.CreateResponse(HttpStatusCode.OK);
// If not valid
return Request.CreateErrorResponse(HttpStatusCode.BadRequest);
}
Using this pattern you could return a '200 OK' response for valid credentials and a '400 Bad Request' for invalid credentials.
As you already stated, you could have the HTML content required for authentication prompt hidden on the page. When the user performs an action which requires authentication, you could render the popup. When the user submits the popup you could fire off an asynchronous request to the Web API endpoint which you created earlier. Depending on the response you get back, you either proceed with the task or prompt for credentials again with an error message.
Obviously as you'd be sending user credentials over a we request, make sure you're making use of HTTPS.
EDIT:
As Chris mentioned below, this solution leaves your 'quick check' in the hands of the client. While this is fine when you simply want to provide a way to stop the user from easily carrying out an action without re-entering their credentials, you should not rely entirely on it.
You could store the username and password as hidden fields and include them with your main synchronous POST. This would allow you to check that the user entered valid credentials from the server.