Scott Hanselman

Sharing Authorization Cookies between ASP.NET 4.x and ASP.NET Core 1.0

October 02, 2016 Comment on this post [15] Posted in ASP.NET | ASP.NET MVC
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ASP.NET Core 1.0 runs on ASP.NET 4.6 nicelyASP.NET Core 1.0 is out, as is .NET Core 1.0 and lots of folks are making great cross-platform web apps. These are Web Apps that are built on .NET Core 1.0 and run on Windows, Mac, or Linux.

However, some people don't realize that ASP.NET Core 1.0 (that's the web framework bit) runs on either .NET Core or .NET Framework 4.6 aka "Full Framework."

Once you realize that it can be somewhat liberating. If you want to check out the new ASP.NET Core 1.0 and use the unified controllers to make web apis or MVC apps with Razor you can...even if you don't need or care about cross-platform support. Maybe your libraries use COM objects or Windows-specific stuff. ASP.NET Core 1.0 works on .NET Framework 4.6 just fine.

Another option that folks don't consider when talk of "porting" their apps comes up at work is - why not have two apps? There's no reason to start a big porting exercise if your app works great now. Consider that you can have a section of your site by on ASP.NET Core 1.0 and another be on ASP.NET 4.x and the two apps could share authentication cookies. The user would never know the difference.

Barry Dorrans from our team looked into this, and here's what he found. He's interested in your feedback, so be sure to file issues on his GitHub Repo with your thoughts, bugs, and comments. This is a work in progress and at some point will be updated into the official documentation.

Sharing Authorization Cookies between ASP.NET 4.x and .NET Core

Barry is building a GitHub repro here with two sample apps and a markdown file to illustrate clearly how to accomplish cookie sharing.

When you want to share logins with an existing ASP.NET 4.x app and an ASP.NET Core 1.0 app, you'll be creating a login cookie that can be read by both applications. It's certainly possible for you, Dear Reader, to "hack something together" with sessions and your own custom cookies, but please let this blog post and Barry's project be a warning. Don't roll your own crypto. You don't want to accidentally open up one or both if your apps to hacking because you tried to extend auth/auth in a naïve way.

First, you'll need to make sure each application has the right NuGet packages to interop with the security tokens you'll be using in your cookies.

Install the interop packages into your applications.

  1. ASP.NET 4.5

    Open the nuget package manager, or the nuget console and add a reference to Microsoft.Owin.Security.Interop.

  2. ASP.NET Core

    Open the nuget package manager, or the nuget console and add a reference to Microsoft.AspNetCore.DataProtection.Extensions.

Make sure the Cookie Names are identical in each application

Barry is using CookieName = ".AspNet.SharedCookie" in the example, but you just need to make sure they match.

services.AddIdentity<ApplicationUser, IdentityRole>(options =>
options.Cookies = new Microsoft.AspNetCore.Identity.IdentityCookieOptions
ApplicationCookie = new CookieAuthenticationOptions
AuthenticationScheme = "Cookie",
LoginPath = new PathString("/Account/Login/"),
AccessDeniedPath = new PathString("/Account/Forbidden/"),
AutomaticAuthenticate = true,
AutomaticChallenge = true,
CookieName = ".AspNet.SharedCookie"


Remember the CookieName property must have the same value in each application, and the AuthenticationType (ASP.NET 4.5) and AuthenticationScheme (ASP.NET Core) properties must have the same value in each application.

Be aware of your cookie domains if you use them

Browsers naturally share cookies between the same domain name. For example if both your sites run in subdirectories under then cookies will automatically be shared.

However if your sites run on subdomains a cookie issued to a subdomain will not automatically be sent by the browser to a different subdomain, for example, would not share cookies with

If your sites run on subdomains you can configure the issued cookies to be shared by setting the CookieDomain property in CookieAuthenticationOptions to be the parent domain.

Try to do everything over HTTPS and be aware that if a Cookie has its Secure flag set it won't flow to an insecure HTTP URL.

Select a common data protection repository location accessible by both applications

From Barry's instructions, his sample will use a shared DP folder, but you have options:

This sample will use a shared directory (C:\keyring). If your applications aren't on the same server, or can't access the same NTFS share you can use other keyring repositories.

.NET Core 1.0 includes key ring repositories for shared directories and the registry.

.NET Core 1.1 will add support for Redis, Azure Blob Storage and Azure Key Vault.

You can develop your own key ring repository by implementing the IXmlRepository interface.

Configure your applications to use the same cookie format

You'll configure each app - ASP.NET 4.5 and ASP.NET Core - to use the AspNetTicketDataFormat for their cookies.

Cookie Sharing with ASP.NET Core and ASP.NET Full Framework

According to his repo, this gets us started with Cookie Sharing for Identity, but there still needs to be clearer guidance on how share the Identity 3.0 database between the two frameworks.

The interop shim does not enabling the sharing of identity databases between applications. ASP.NET 4.5 uses Identity 1.0 or 2.0, ASP.NET Core uses Identity 3.0. If you want to share databases you must update the ASP.NET Identity 2.0 applications to use the ASP.NET Identity 3.0 schemas. If you are upgrading from Identity 1.0 you should migrate to Identity 2.0 first, rather than try to go directly to 3.0.

Sound off in the Issues over on GitHub if you would like to see this sample (or another) expanded to show more Identity DB sharing. It looks to be very promising work.

Sponsor: Big thanks to Telerik for sponsoring the blog this week! 60+ ASP.NET Core controls for every need. The most complete UI toolset for x-platform responsive web and cloud development.Try now 30 days for free!

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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October 02, 2016 21:12
Is there a change that Core/ .Net Core will support forms Authentication. (.ASPXAUTH) We are running a site with millions of users with Forms Authentication in a SharePoint Site (web site) and we are building a new part based on .Net core. Currently I understand that we need to change the way to autenticate in the web site. (all other examples I have seen on this is based on having a MVC site on .Net 4)
October 03, 2016 7:14
Scott what I would love to see is a simple Core MVC WebApi and Angular 2 application walk-through. Keep it really simple. Data input, output and display. Some of the tutorials are just to much. Too many frameworks, libs, docker and a million other things. Can we just get back to some roots 101 stuff? Can you help me out?
October 03, 2016 8:34
Now that's great @Scott. And +1 @Chris Go. That's exactly what bigger portion of the world would want to see. U know, for the rest of us. N I am sure, @Scott knows that.
October 03, 2016 8:53
Wouldn't a JWT authentication implementation be easier, cleaner, and more extensible than cookie sharing like this? Setup a separate login website to manage token creation, then redirect to 4.5 and Core 1.0 sites passing the token around. Separating concerns.
October 03, 2016 11:59
@ChrisGo something like this?
October 03, 2016 12:25
@ChrisGo If You are looking for C# developer friendly SPA framework, just try DotVVM - .NET-based Framework for Line-of-Business Web Apps (based on MVVM pattern principles, without tons of javascript code/libs)
October 03, 2016 18:02
Thanks for the links, I have Pluralsight as well would not mind seeing a 4 hour course on my request as well. Doesn't need to be 100% free or anything.
October 03, 2016 18:08
@Scott ASP.NET Core 1.0 actually runs on .NET 4.5.1 full framework or higher.
October 03, 2016 22:46
Really it should be noted that this is about sharing with ASP.NET *MVC*. Like Peakman, I would like to see something about ASP.NET WebForms and new ASP.NET Core authentication sharing. We have an extremely large project ... that is working just fine, mind you. But if we want to start moving towards .NET Core, there's an awful lot to rewrite w/out much benefit other than being on the latest trend...
October 04, 2016 2:19
I would reaaaallly like to see an example of using WS Federation in ASP.Net Core targeting the full .Net Framework. There are a lot of people operating with ADFS, so WS Federation is a must. But there are no good examples out there, it is a missing piece of the ASP.Net Core puzzle.
October 04, 2016 3:11
So webforms really hasn't got the extensibility points we need to enable cookie sharing.

For those of you in those situations I'd suggest looking at federated login as a solution. Webforms supports OpenID Connect or WS-Fed.

You'd then use IdentityServer to handle all your logins, and hold your user database. Your apps would direct to it for login, then bounce back to your application where you'd drop an authentication cookie according to your application needs, be it webforms, MVC, or MVC core.
October 04, 2016 3:12
However if you drag your webforms app kicking and screaming to be hosted under Katana, then the cookie sharing does work, because both webforms and MVC under Katana and .NET 4.5.1 share the same cookie middleware.

You can see that in the VS2013 and beyond templates.
October 04, 2016 3:14
@Stephen - We're well aware of the need for WS-Fed in core, but we're still waiting for the classes we need to appear in .NET Core. You can keep an eye on that work at
October 06, 2016 20:16
I have done something similar in Classic ASP + .NET when part of functionality needed to be upgraded to .NET but everything else still runs on Classic ASP. 2 apps sit on 2 different app servers, only to be combined together by a Apache on front.
October 07, 2016 14:54
It all seems a world of troubles if you follow this. I will stay at .NET 4.6.1 for the next 12 months.
Core brings not more but less to the table.

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Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.