What is the reason for the "Login timeout" setting and functionality?

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If an application redirects the user to the Keycloak login page, and it sits there for more than the "Login timeout" (default 5 minutes), then when the users enters a username and password, instead of a login, she is greeted by:

You took too long to login. Login process starting from beginning.

login page timed out

To avoid this, one can change "Realm Settings → Tokens → Login timeout" to e.g. 10000 days which is 27 years, which should ensure this never happens in reality.

But before we go ahead and effectively disable this timeout, we'd like to ask: What is the purpose of this timeout? Somebody apparently went to the trouble of implementing it, but what is it protecting against? What are the (security?) consequences of disabling it?

keycloak
1 Answers

As far as I know, it is mostly used as an additional mechanism to avoid session fixation attacks. For instance, in a company a user goes for a coffee and leaves the computer on, and then the hacker sees the opportunity and manually sets in the Browser URL the current login session ID (or just copies it). Now if the system is configured in a way that the session ID does not change in-between the pre and the pos login phases. Then after the victim has successfully authenticated, the hacker will be able to use, without having to insert any authentication, the session that the victim is currently on;

The higher the timeout is, the wider will be the window of opportunity for such attacks to happen. Login timeout is just another layer of protection to avoid such issues, as it is session expiration, changing the Session ID between the pre-login and pos-login phase, among others.

More formally one can read in (source).

Initial Login Timeout This extra protection mechanism tries to force the renewal of the session ID pre-authentication, avoiding scenarios where a previously used (or manually set) session ID is reused by the next victim using the same computer, for example, in session fixation attacks.

And from the OWASP.org

Session Fixation is an attack that permits an attacker to hijack a valid user session. The attack explores a limitation in the way the web application manages the session ID, more specifically the vulnerable web application. When authenticating a user, it doesn’t assign a new session ID, making it possible to use an existent session ID. The attack consists of obtaining a valid session ID (e.g. by connecting to the application), inducing a user to authenticate himself with that session ID, and then hijacking the user-validated session by the knowledge of the used session ID. The attacker has to provide a legitimate Web application session ID and try to make the victim’s browser use it.

A fairly good explanation on how the session fixation attacks works and how to prevent it here and here.

Now I am not a security expert, but I would say that if you have other preventing mechanisms in place such as change the session ID, you should be fine. However, on the other side of the coin, do you really need that much time to login? And is that much of an annoyance to just refresh again?

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