"Remember Me On This Computer" - How Should It Work?

I regularly use 2 or 3 machines simultaneously, and have "remember me" on all of them. If one of them disconnected the others that would be very annoying, so I wouldn't recommend it.

Traditionally it would use a time-out, the cookie expires after a certain length of time (or when the user signs out).

It all depends on your security model. If you are writing an internal company application where you only ever expect one user to be on one computer then you might want to have tighter restrictions than gmail.

Also, bear in mind the possibility of Denial of Service - if an action on one machine can force another machine to be unusable this could be use to prevent a legitimate user from taking control back in certain scenarios.

Logging on from another machine should not invalidate the login associated with a cookie on a different machine. However if the users logsout or "not you? login here" this should clear the cookie on which the user is working.

By the way stealing a cookie can be made hard, by insisting on https and making it not for scripting.

By adding "; HttpOnly" to the out put of your cookie this will make the cookie unavailable to javascript e.g.

HTTP/1.1 200 OK
Cache-Control: private
Content-Type: text/html; charset=utf-8
Content-Encoding: gzip
Vary: Accept-Encoding
Server: Microsoft-IIS/7.0
Set-Cookie: ASP.NET_SessionId=ig2fac55; path=/; HttpOnly
X-AspNet-Version: 2.0.50727
Set-Cookie: user=t=bfabf0b1c1133a822; path=/; HttpOnly
X-Powered-By: ASP.NET
Date: Tue, 26 Aug 2008 10:51:08 GMT
Content-Length: 2838

you can read more about this

• for .Net
• Firefox support
• Jeff - Codings hard, lets go shopping

The remember me cookie should identify the machine as well. It should be related to the machine because there are places where you want to be remembered and other places where you don't (home vs work).

Expiration date is set usually to a reasonable period (two weeks) or after the user has explicitly logged off from the machine,