TGC cookies protection info

[Trenton D. Adams]

Absolutely, I totally agree. It's not a good idea to use non-SSLed services. 

----- Original Message ----- 
From: "Andrew Petro" <apetro at unicon.net> 
To: "Yale CAS mailing list" <cas at tp.its.yale.edu> 
Sent: Friday, February 22, 2008 11:30:35 AM (GMT-0700) America/Denver 
Subject: Re: TGC cookies protection info 


Trenton, 

You're quite right, it is important that the target service use SSL as well. It is trivial to intercept the *session cookie* that you will almost certainly establish with that particular service if the service does not use SSL. It's also trivial to listen in on traffic and even to forge responses in a non-SSL environment. It's a matter of degree, but I would strongly recommend not relying on the difficulty of intercepting a ticket under a regime of non-SSLed target services as a factor lending security to a system using CAS. 

However, I would emphasize: no matter whether the target service uses SSL or not, or anything else it does, or if it's compromised, or if evil people with nefarious intentions wrote it and are running it, or anything else: there's *nothing* that the service to which you're trying to authenticate can do to get access to the Ticket Granting Cookie or primary credentials themselves. The service ticket for the specific purpose of authenticating to that application can be exposed by a compromised target service, but the compromised target service cannot access the ticket granting cookie and so cannot accomplish authentication to other services i.e. illicit proxies. 

Andrew 



Trenton D. Adams wrote: 

Hi Guys, 

I agree with Andrew.  The only risk is if your service is not using SSL as well.  In cases like that, it is trivial to intercept the cookie, and use it to gain access to the site the user was attempting to gain access to.  But, even this requires a high level of access to networks between the user and the service server.  i.e. Perhaps a disgruntled employee at an ISP somewhere in between.  So, even in the case when not using an SSL enabled service, it is pretty difficult to intercept a ticket. 

----- "Andrew Petro" <apetro at unicon.net> wrote: 


Chris, 

The ticket granting cookie is typically an SSL-vended, tightly-scoped 

(just for your CAS server), session-scoped (expired by your browser 
when 
your browser session ends) cookie. 

I say typically because all these things are configurable, but I 
strongly recommend you don't change the defaults on any of these 
aspects 
of the cookie. 

There are two perspectives to examine cookie security. One perspective 

is security on the web. 

Since the cookie is SSL-vended, the Adversary cannot obtain it by 
evesdropping on the line. Since it is tightly scoped (and SSL-vended), 

the browser will not re-present this cookie on requests to sites other 

than the CAS server. Since the cookie is not used to authenticate to 
other sites (rather, the cookie is re-presented to CAS, which then 
issues a shorter-lived transactional service ticket conveyed via 
request 
parameter on a redirect rather than as a cookie), other sites do not 
have access to this cookie. 

So, "How secure is the TGC?" The TGC is "very secure", in that 
industry-standard methods for protecting session cookies are applied 
to 
protect what is effectively a CAS server session cookie. It is no 
easier 
for the Adversary to steal a TGC from the browser over the web than it 

is to steal any other secure session cookie, such as that you use to 
access your bank's account management web application during the 
course 
of an active session. 


There's another perspective for considering TGC security -- what if 
the 
Adversary has direct access to the end user's computer? What if the 
computer is compromised, or physically stolen during the course of an 

active session in which the TGC is still resident? 

Since it is session-scoped, typical browsers will not commit it to 
disk 
and will delete it when a browser session ends normally, so the window 

of opportunity is narrow. Nonetheless, the popular expression among 
computer security professionals goes something like "physical access 
to 
the computer is equivalent to root access", and that is apt here. A 
compromised web browser, operating system, or physically accessed 
machine can have spyware installed, a compromised browser installed, 
to 
capture the primary credentials when they are presented to CAS, to 
capture TGCs, or really to do anything else. Compromised computers are 
a 
bad thing. CAS makes this no worse, but it doesn't magically solve 
it. 

To put this in perspective, if I access my online bank account web 
interface from a compromised computer, I necessarily reveal all the 
credentials necessary to access my account from that computer, at 
least 
for the course of that session. 

If one were inclined to implement all those fun rotating security 
questions, distinctions between public and personal computers, IP 
address tracking to prevent cookies from being presented from 
different 
IP addresses during the course of a session (personally, I truly 
despise 
this misfeature), while CAS doesn't tend to have these features out of 

the box, it certainly offers an extensible platform in which they can 
be 
implemented. Spring Web Flow for the win. 

Andrew 






Hi, 

I've successfully installed and configure CAS to use my LDAP user 
database. I'm almost on production stage :) 

My IT asked me about "How secure is the TGC?" meaning is it possible 
for 


a hacker to steal a TGC from a user browser, and use it to 
impersonate a 


user. 

I read in the doc and powerpoints that the TGC was 'private' and 
'protected' but I dunno exactely what it means. 

Can anyone tell me more about TGC protection? How much are they 
secured? 


Best, 

Chris 

_______________________________________________ 
Yale CAS mailing list 
cas at tp.its.yale.edu http://tp.its.yale.edu/mailman/listinfo/cas _______________________________________________ 
Yale CAS mailing list 
cas at tp.its.yale.edu http://tp.its.yale.edu/mailman/listinfo/cas __ 
    This communication is intended for the use of the recipient to whom it
    is addressed, and may contain confidential, personal, and or privileged
    information. Please contact us immediately if you are not the intended
    recipient of this communication, and do not copy, distribute, or take
    action relying on it. Any communications received in error, or
    subsequent reply, should be deleted or destroyed.
---
_______________________________________________
Yale CAS mailing list cas at tp.its.yale.edu http://tp.its.yale.edu/mailman/listinfo/cas 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://tp.its.yale.edu/pipermail/cas/attachments/20080222/19fc19a3/attachment.html