Multiple & SubDomain's cookie in asp.net Core Identity - asp.net-core

Question

I have a webpage which uses multiple URLS for the same application:
for example:
*.MyWebPage.com.au
*.YourWebPage.com.au
So it will use subdomains on multiple urls. The problem is I need to allow for the user to be authenticated on all subdomains of the url which they have logged into.
For example, if they login via www.mywebpage.com.au the cookie needs to be set for *.mywebpage.com.au or if they login via www.yourwebpage.com.au the cookie should be *.yourwebpage.com.au.
Most of the documentation in allowing subdomains for ASP.NET core identity points to the startup.cs (or startup.auth.cs) file and entering something like this:`
app.UseCookieAuthentication(new CookieAuthenticationOptions()
{
CookieDomain = "mywebpage.com.au"
});`
this will not work for me because I dont want a fixed domain, I just want to allow for all the users to have access to all the subdomains for the url they have signed in at. I can obviously get their url at the time of login via the request, but I need to dynamically set the cookiedomain at this point.

Answer 1

What I didnt realise when I started was the difference between Identity and CookieAuthentication.
Since I was using Identity
app.UseIdentity();
app.UseCookieAuthentication was not the solution.
I finally found my solution by implementing ICookieManager.
Here is my solution:
in Startup.cs:
services.AddIdentity<ApplicationUser, IdentityRole>(options =>
{
options.Password.RequireDigit = false;
options.Password.RequiredLength = 5;
options.Password.RequireNonAlphanumeric = false;
options.Password.RequireLowercase = false;
options.Password.RequireUppercase = false;
options.Cookies.ApplicationCookie.CookieManager = new CookieManager(); //Magic happens here
}).AddEntityFrameworkStores<ApplicationDbContext>()
.AddDefaultTokenProviders();
now in a class I have called CookieManager.cs:
public class CookieManager : ICookieManager
{
#region Private Members
private readonly ICookieManager ConcreteManager;
#endregion
#region Prvate Methods
private string RemoveSubdomain(string host)
{
var splitHostname = host.Split('.');
//if not localhost
if (splitHostname.Length > 1)
{
return string.Join(".", splitHostname.Skip(1));
}
else
{
return host;
}
}
#endregion
#region Public Methods
public CookieManager()
{
ConcreteManager = new ChunkingCookieManager();
}
public void AppendResponseCookie(HttpContext context, string key, string value, CookieOptions options)
{
options.Domain = RemoveSubdomain(context.Request.Host.Host); //Set the Cookie Domain using the request from host
ConcreteManager.AppendResponseCookie(context, key, value, options);
}
public void DeleteCookie(HttpContext context, string key, CookieOptions options)
{
ConcreteManager.DeleteCookie(context, key, options);
}
public string GetRequestCookie(HttpContext context, string key)
{
return ConcreteManager.GetRequestCookie(context, key);
}
#endregion

Answer 2

In addition to #michael's solution:
ICookie: ICookie Interface is an abstraction layer on top of http cookie object, which secures the data.
ICookieManager: Cookie Manager is an abstraction layer on top of ICookie Interface. This extends the Cookie behavior in terms of <TSource> generic support, Func<TResult>.This is implemented by DefaultCookieManager class. ICookie Interface is a depedenacy of this class.
Usage of CookieManager:
Add CookieManager in startup Configure Service.
Access the CookieManager API.
And the source code is available on git by Nemi Chand.

Answer 3

How many main domains are there? If there are not too many, you can add several CookieAuthenticationOptions. Like this:
app.UseCookieAuthentication(new CookieAuthenticationOptions
{
AuthenticationScheme = "mywebpage.com.au",
CookieDomain = "mywebpage.com.au",
});
app.UseCookieAuthentication(new CookieAuthenticationOptions
{
AuthenticationScheme = "yourwebpage.com.au",
CookieDomain = "yourwebpage.com.au",
});
If there are too many main domains, you will need to write your own cookie provider.

Answer 4

Addition to #michael's answer:
How to "handle the deletecookie event, adding options.Domain = RemoveSubdomain(context.Request.Host.Host)":
just add
options.Domain= RemoveSubdomain(context.Request.Host.Host);
before
ConcreteManager.DeleteCookie(context, key, options);
in
CookieManager.DeleteCoockie(..){..};
And don't forget to call CookieManager.DeleteCoockie on logout!
PS Also, if you need to be able to login both on subdomain.example.com and on example.com - you need to modify AppendResponseCookie(..){..}, or you will get only TLD (.com/.ru etc) here