Re: Single terminal login

[Matt Wirges <wirges () purdue edu>]

stevenr () mastek com wrote:
> Hi
>
> I have worked with web based applications since quite some time. One issue to which I have not found a satisfactory answer yet is that of a problem with Single Terminal Login in a web based application. 
>
> By Single Terminal Login, I mean that if one user logs into a web application (say JSP based), s/he should not be able to login from another machine or even another browser from the same machine. This can be achieved easily by setting a "logged in" flag on the server side using a DB or LDAP etc. When the user clicks on the Logout link, the flag is reset and only then the user can login from another browser/window. Now the hitch. If the user closes the browser directly, or the power goes out, or browser hangs and has to be killed, the flag remains as "logged in". In short user cannot login into the system again. The one workaround used commonly, is setting a timeout after which the user can login again, where a "last active time" is maintained for each user. Every login request is cross-checked against this time and if the difference is greater than some threshold value, the user is able to login again.  But this means that everytime the user does something the "last active 
time" will have to be updated, which will be expensive in a high traffic site. Also, the threshold value is always a 
hot topic of debate :-)
> Does anyone know a better or a different approach to this? Would be helpful if someone knows some site/papers for this. 
> Have googled but havent come across any myself.
>
> - Steve
>
> "He who laughs last probably made a backup..." 
>
>
>
> MASTEK
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Steve,

  What we've done in the past on a few applications is simply close the 
old session the next time the user logs in.  For example, one of the 
applications I worked on is a web interface for incident response.  One 
of its features is time tracking to see how long a responder has worked 
on an incident.  So if the responder closes his web browser or his 
session expires, i.e. he doesn't log out via the application, the 
session remains active in the session table until the next time he logs 
in.  When the user logs in again, the system asks him to enter the time 
when he last used it and then closes the session updating it with his 
logout time and initiates the new session.

In other applications I've simply just auto-closed the session when a 
new login is detected.


-matt

--
Matthew Wirges
IT Security and Policy Analyst
Security and Policy
Information Technology at Purdue
wirges () purdue edu :: (765)49-62307
www.itap.purdue.edu/security