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" <[EMAIL PROTECTED]> 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
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