RE: Session Management and IP address - experiences?

["Fling, Steven" <sfling () oppenheimerfunds com>]

One way to handle this is reactively (monitor and alerting of such activity) vs. proactively (blocking access).  With 
common monitoring tools you can set up rules to alert when a new IP is attempting to access an existing session, but 
prevent such alerts for know ISPs that utilize IP pooling techniques.  Support staff can then apply human intelligence 
in the moment to determine if access needs to be cut off at the firewall level for the suspect IP.

=========================
Steve Fling
Manager of External Touchpoints
OppenheimerFunds, Inc.
303-768-3200 p
303-768-1096 f
sfling () oppenheimerfunds com <mailto:sfling () oppenheimerfunds com> 
=========================


-----Original Message-----
From: David Wall @ Yozons, Inc. [mailto:dwall () yozons com]
Sent: Thursday, September 02, 2004 1:40 PM
To: webappsec () lists securityfocus com
Subject: Re: Session Management and IP address - experiences?


> It is common knowledge, that things like loadbalanced proxies, where the
ip
> address might change within a running session, interfere with this kind of
> security enhanced session management.

It's pretty common, especially for those using the biggest ISPs who use
these schemes.  Most others come from a single proxy or NAT/gw so the IP
wouldn't change.

> Is it perhaps exceptable, as it happens only in rare cases? If this is the
> case, one might present the user another login where he can prove his
> identity again and continue with the session.

But what ACTUAL problem are you trying to avoid?  Have you seen someone step
in the middle of one of your users activities, steal a session cookie, and
then impersonate them?  If not, perhaps you are solving problems you don't
really have, so why put the headache in for those who will have issues
because they are being such proxies?

> (It is another story that session-ip-binding wouldn't solve the whole
> problem, as there are several szenarios, where an attacker might use the
> same proxy etc. as the victim...)

Exactly, which also leads to the question of why bother?

Perhaps if IPv6 ever gets into widespread use (ha ha ha?!) this will be
powerful because such proxies may no longer be there.  Today, it seems like
solving a problem that perhaps doesn't exist.  Couple a good session id
(random and long) with SSL and you'll find most of your security violations
result from bad passwords and social engineering attacks -- they are much
easier to hack than stepping in the middle of a session...

David



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