Secure Account Activation with ASP.NET Identity

Distribution of credentials to new users of a system is often done in an insecure way, with passwords being sent over unsecure e-mail. With ASP.NET Identity, the password recovery functionality can be used to create a secure account activation mechanism.

The scenario for ASP.NET Identity, in the default MVC template is to let users self register. Then there are mechanisms to confirm the e-mail address, to make sure that the user actually is in control of the given e-mail address. There are also support for letting the user associate the account with external sign on solutions such as Google, Facebook and Twitter. That’s perfectly fine, but not for most applications I build.

I’m building line of business applications. They are actually often exposed on the Internet as they need to be available for partners. But, they are not meant to be available through self registration for anyone on the Internet. Those applications are invite only. That means that a user account is created for a new user. Then that user somehow has to be notified that the account has been created. The usual way to do that is to create the account, set a good password like “ChangeMe123” and send the user a mail with the new credentials. There are two problems with this

  1. A lot of users don’t get the hint and keep the “ChangeMe123” password.
  2. The e-mail can be sitting unread for a long time in the inbox, until someone gets hold of it – and the account.

Fortunately, there is a much more secure way to do account activation with ASP.NET Identity without much coding at all – by reusing the password recovery mechanism.

Catching the System.Web/Owin Cookie Monster

CookieMonster-SittingCookies set through the Owin API sometimes mysteriously disappear. The problem is that deep within System.Web, there has been a cookie monster sleeping since the dawn of time (well, at least since .NET and System.Web was released). The monster has been sleeping for all this time, but now, with the new times arriving with Owin, the monster is awake. Being starved from the long sleep, it eats cookies set through the Owin API for breakfast. Even if the cookies are properly set, they are eaten by the monster before the Set-Cookie headers are sent out to the client browser. This typically results in heisenbugs affecting sign in and sign out functionality.

TL;DR

The problem is that System.Web has its own master source of cookie information and that isn’t the Set-Cookie header. Owin only knows about the Set-Cookie header. A workaround is to make sure that any cookies set by Owin are also set in the HttpContext.Current.Response.Cookies collection.

This is exactly what my Kentor.OwinCookieSaver middleware does. It should be added in to the Owin pipeline (typically in Startup.Auth.cs), before any middleware that handles cookies.

app.UseKentorOwinCookieSaver();

The cookie saver middleware preserves cookies set by other middleware. Unfortunately it is not reliable for cookies set by the application code (such as in MVC Actions). The reason is that the System.Web cookie handling code might be run after the application code, but before the middleware. For cookies set by the application code, the workaround by storing a dummy value in the sessions is more safe.

Using Owin External Login without ASP.NET Identity

ASP.NET MVC5 has excellent support for external social login providers (Google, Facebook, Twitter) integrating with the ASP.NET Identity system. But what if we want to use external logins directly without going through ASP.NET Identity? Using external logins together with ASP.NET Identity is very simple to get started with, but it requires all users to register with the application. External logins are just another authentication method against the internal ASP.NET Identity user. In some cases there is no need for that internal database, it would be better to get rid of it and use the external login providers without ASP.NET Identity. That’s possible, but requires a bit of manual coding.

For public facing web applications I think that it is often a good idea to use ASP.NET Identity as it doesn’t tie the user to a specific login provider. But if we are fine with using one and only one specific login provider for each user it’s possible to skip ASP.NET Identity. It could be an organization that heavily relies on Google Apps already so that all users are known to have Google accounts. It could be an application that uses SAML2 based federative login through Kentor.AuthServices.

In this post I’ll start with a freshly created ASP.NET MVC Application without any authentication at all and make it use Google authentication, without ASP.NET Identity being involved at all. The complete code is available on my GitHub account.

Writing an Owin Authentication Middleware

Owin and Katana offers a flexible pipeline for external authentication with existing providers for authentication by Google, Facebook, Twitter and more. It is also possible to write your own custom authentication provider and get full integration with the Owin external authentication pipeline and ASP.NET Identity.

Anatomy of an Owin Authentication Middleware

For this post I’ve created a dummy authentication middleware that interacts properly with the authentication pipeline, but always returns the same user name. From now on I will use the names from that dummy for the different classes.

A typical Katana middleware is made up of 5 classes.

  1. The main DummyAuthenticationMiddleware class.
  2. The internal DummyAuthenticationHandler class doing the actual work.
  3. A DummyAuthenticationOptions class for handling settings.
  4. An extension method in DummyAuthenticationExtensions for easy setup of the middleware by the client application.
  5. An simple internal Constants class holding constants for the middleware.

Understanding the Owin External Authentication Pipeline

Owin makes it easy to inject new middleware into the processing pipeline. This can be leveraged to inject breakpoints in the pipeline, to inspect the state of the Owin context during authentication.

When creating a new MVC 5.1 project a Startup.Auth.cs file is added to the project that configures the Owin pipeline with authentication middleware. Two middleware for authentication are enabled through calls to app.UseCookieAuthentication() and app.UseExternalSignInCookie. There are also commented out sections for Microsoft, Twitter, Facebook and Google authentication. This post will use Google Authentication as an example and also add some “dummy” middleware that makes it possible to set breakpoints and inspect the authentication pipeline.

Inserting Breakpoint Middleware

The middleware is executed in the order they are listed in the file, so by inserting a simple middleware between the existing, it is possible to inspect how each middleware interact with the authentication pipeline.

The injected middleware is just a few lines of code, but it allows two breakpoints to be set: on the opening and closing braces, which enables inspection before and after the call to the next middleware.

app.Use(async (context, next) =>
{
  await next.Invoke();
});
Software Development is a Job – Coding is a Passion

I'm Anders Abel, a systems architect and developer working for Kentor in Stockholm, Sweden.

profile for Anders Abel at Stack Overflow, Q&A for professional and enthusiast programmers

Code for most posts is available on my GitHub account.

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