Share cookies or session data between cross domain using ASP.NET C#

Question

We have a shared state management server and aim to transfer session values between two domains: modern.com and 180algos.com. Both domains redirect to a common page, freelogin.aspx, which is hosted exclusively on modern.com. On this page, I need to retrieve the session["sitename"] value.

For example:

1. modern.com/password.aspx stores session["sitename"] = "V3".
2. 180algos.com/login.aspx stores session["sitename"] = "360algos".
3. Without using a redirect or query string, we access freelogin.aspx directly, such as https://modern.com/freelogin.aspx. On this page, I need to identify the originating site and handle the session value accordingly.

freelogin.aspx.cs

if (session["sitename"] == "V3")

{

    // From the modern site 

}

else if (session["sitename"] == "360algos")

{

    // From the 180algos site

}

How can I implement this functionality in ASP.NET using alternative approaches, such as sessions, cookies, or JWTs?

If I access the page directly using https://modern.com/freelogin.aspx, the stored session value should be retrieved.

Note :-

1. Should not use any redirection/query string ex:- Response.Redirect("https://freelogin.aspx?sitename=V3");
2. Is it possible to transfer data across different domains?

Answer 1

Hi @Ashok Kumar,

For subdomains in the same root domain only - you can use wildcard cookies by specifying a subdomain. For example, sv1.test.com and sv2.test.com will both use test.com

For using a single cookie across root domains - you can't do that. It violates the trust rules - otherwise my application could read your other cookies. In sites that "seem" to share cookies, it's common to redirect to the other domain to verify the value, then redirect back to the other domain. The value can then be posted, set in a hidden form field or in a query string.

Best regards,
Lan Huang

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