Strange behavior: lots of logins by one user

[Losen, Stephen C (scl)]

Hi Manolo,

I suspect a redirect loop.  The user logs in to the IDP and the IDP passes the assertion to the browser. The browser presents the assertion to the SP.  For some reason the SP rejects the login, perhaps because the user is missing from the SP’s own user database, or an attribute value is missing or unacceptable to the  SP.  Instead of displaying an error page, the SP redirects the browser back to the SP’s own login URL.  This would be reasonable if the SP were displaying its own username/password page. (When login fails, let the user try again.)  But in the case of SAML, redirecting back to the SP login URL results in a redirect to your IDP to authenticate again.  The user has a valid SSO session, so the IDP silently gives the browser another assertion and the browser presents it to the SP, which rejects it and redirects to the SP login URL again, etc.  The browser address window at the top probably shows at least two URLs flickering back and forth, and each trip through the loop gets logged on the IDP as a successful login.

The solution is not on the IDP.  It is behaving normally and correctly.  The culprit is the SP, which should display an error instead of redirecting to login again.  If the SP has a configuration “dashboard” then this behavior may be configurable.  Otherwise you need to notify the SP admins.

Or I suppose you could configure “Forced Authentication” for the troublesome SP.  This will cause your IDP to display its login page rather than silently redirect.  I think you can do this in conf/relying-party.xml with an override for the SP.  A quick check of the IDP wiki shows this is possible if you are running IDP 3.4.

Stephen C. Losen
ITS - Systems and Storage
University of Virginia
scl at virginia.edu<mailto:scl at virginia.edu>    434-924-0640

From: users [mailto:users-bounces at shibboleth.net] On Behalf Of Manolo Garcia Alvarez
Sent: Wednesday, January 30, 2019 5:49 AM
To: Shib Users <users at shibboleth.net>
Subject: Strange behavior: lots of logins by one user

Hi,

we are using Shibboleth as an IdP with a lot of SP's for a community of about 50.000 active users, without problems so far. Nevertheless, our idp-audit shows a strange behavior of some users: a few number of users are registering successful logins in a short period of time (1 hour typically):

This is one of them:

[image.png]

The bump on the graph shows just one user (login amartingil) who has more than 1800 logins in one hour according to the idp-login.log, so it's clear that's not possible for one real user. In this example, the SP is Google and all the logins are registered in one of three the servers that are running Shibboleth. That's just one case, but we find this everyday with another set of users and another period of time. I can attach the relevant parts of the logs if it's useful.

I have done some research in the list and internet but I can't find anybody with the same problem. Is there someone with the same problem or information about this issue?

Thanks a lot !

________________________________
Manolo García
Arquitectura i Sistemes
Universitat Oberta de Catalunya

93 326 (3451) | 689 88 30 93 | mgarciaal at uoc.edu<mailto:mgarciaal at uoc.edu>
Parc Mediterrani de la Tecnologia (edifici B3)
Av. Carl Friedrich Gauss, 5.
08860 Castelldefels
[Universitat Oberta de Catalunya]
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