.NET Core Identity Server 4 Authentication VS Identity Authentication

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TL;DR

IdentityServer = token encryption and validation services via OAuth 2.0/OpenId-Connect

ASP.NET Identity = current Identity Management strategy in ASP.NET

How can I authenticate similar to the way done in previous version’s of .Net does the old way still work or is there a newer version.

I see no reason why you couldn’t achieve the old way in ASP.NET Core, but in general, that strategy was replaced with ASP.NET Identity, and ASP.NET Identity is alive and well in ASP.NET Core.

https://docs.microsoft.com/en-us/aspnet/core/security/authentication/identity

ASP.NET Identity uses a backing store like SQL Server to hold user information like username, password (hashed), email, phone and easily be extended to hold FirstName, LastName or whatever else. So, there really no reason to encrypt user information into a cookie and pass it back and forth from client to server. It supports notions like user claims, user tokens, user roles, and external logins. Here are the entities in ASP.NET Identity:

  • AspNetUsers
  • AspNetUserRoles
  • AspNetUserClaims
  • AspNetUserLogins (for linking external identity providers, like Google, AAD)
  • AspNetUserTokens (for storing things like access_tokens and refresh_tokens amassed by the user)

What are the pros and cons of using your own token server verses creating your own custom principle?

A token server would be a system that generates a simple data structure containing Authorization and/or Authentication information. Authorization usually takes the for of a token named access_token. This would be the “keys to the house”, so to speak, letting you through the doorway and into the residence of a protected resource, usually a web api. For Authentication, the id_token contains a unique identifier for a user/person. While it is common to put such an identifier in the access_token, there is now a dedicated protocol for doing that: OpenID-Connect.

The reason to have your own Security Token Service (STS), would to be to safeguard your information assets, via cryptography, and control which clients (applications) can access those resources. Furthermore, the standards for identity controls now exist in OpenID-Connect specifications. IdentityServer is an example of a OAuth 2.0 Authorization Server combined with an OpenID-Connect Authentication server.

But none of this is necessary if you just want a user table in your application. You don’t need a token server- just use ASP.NET Identity. ASP.NET Identity maps your User to a ClaimsIdentity object on the server- no need for a custom IPrincipal class.

When using a cloud based solution or a separate Token server how would you Integrate that with your current application, would I would still need a users table in my application how would you associate the two?

See these tutorials for integrating separate identity solutions with an application:
https://identityserver4.readthedocs.io/en/latest/quickstarts/0_overview.html
https://auth0.com/docs/quickstart/webapp/aspnet-core

At a minimum you would need a two column table mapping the username to the external provider’s user identifier. This is what the AspNetUserLogins table does in ASP.NET Identity. The rows in that table however are dependent on the being a User record in AspNetUsers.

ASP.NET Identity supports external providers like Google, Microsoft, Facebook, any OpenID-Connect provider, Azure AD are already there. (Google and Microsoft have already implemented the OpenID-Connect protocol so you don’t need their custom integration packages either, like this one, for example). Also, ADFS is not yet available on ASP.NET Core Identity.

See this doc to get started with external providers in ASP.NET Identity:

https://docs.microsoft.com/en-us/aspnet/core/security/authentication/social/

Being that there are so many different solutions how can I create an enterprise application, to allow Login through Gmail/Facebook while still being able to expand to other SSO’s

As explained above, ASP.NET Identity already does this. It’s fairly easy to create an “External Providers” table and data drive your external login process. So when a new “SSO” comes along, just add a new row with the properties like the provider’s url, the client id and secret they give you. ASP.NET Identity already has the UI built in there Visual Studio templates, but see Social Login for cooler buttons.

Summary

If you just need a users table with password sign in capabilities and a user profile, then ASP.NET Identity is perfect. No need to involve external authorities. But, if have many applications needing to access many apis, then an independent authority to secure and validate identity and access tokens makes sense. IdentityServer is a good fit, or see openiddict-core, or Auth0 for a cloud solution.

My apologies is this isn’t hitting the mark or if it is too introductory. Please feel free to interact to get to the bulls-eye you are looking for.

Addendum: Cookie Authentication

To do bare bones authentication with cookies, follow these steps. But, to my knowledge a custom claims principal is not supported. To achieve the same effect, utilize the Claims list of the ClaimPrincipal object.

Create a new ASP.NET Core 1.1 Web Application in Visual Studio 2015/2017 choosing “No Authentication” in the dialog. Then add package: 

Microsoft.AspNetCore.Authentication.Cookies

Under the Configure method in Startup.cs place this (before app.UseMvc):

app.UseCookieAuthentication(new CookieAuthenticationOptions
{
    AuthenticationScheme = "MyCookieMiddlewareInstance",
    LoginPath = new PathString("/Controller/Login/"),
    AutomaticAuthenticate = true,
    AutomaticChallenge = true
});

Then build a login ui and post the html Form to an Action Method like this:

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Login(String username, String password, String returnUrl = null)
{
    ViewData["ReturnUrl"] = returnUrl;
    if (ModelState.IsValid)
    {
        // check user's password hash in database
        // retrieve user info

        var claims = new List<Claim>
        {
            new Claim(ClaimTypes.Name, username),
            new Claim("FirstName", "Alice"),
            new Claim("LastName", "Smith")
        };

        var identity = new ClaimsIdentity(claims, "Password");

        var principal = new ClaimsPrincipal(identity);

        await HttpContext.Authentication.SignInAsync("MyCookieMiddlewareInstance", principal);

        return RedirectToLocal(returnUrl);
    }

    ModelState.AddModelError(String.Empty, "Invalid login attempt.");

    return View();
}

The HttpContext.User object should have your custom claims and are easily retrievable the List collection of the ClaimPrincipal.

I hope this suffices, as a full Solution/Project seems a bit much for a StackOverflow post.

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