for me +1 if it does not interfere with other stuff.

Jörn Zaefferer wrote:
Hi,

my application currently uses CryptedUrlWebRequestCodingStrategy to
protect against CRSF attacks. Afaik 1.3.5 will include an update that
generates the key based on user sessions:
http://issues.apache.org/jira/browse/WICKET-1782
According to Johan Compagner, there are still issues with that
approach, though I don't know if that has been fixed:
http://www.nabble.com/Wicket-not-secure--to19556259.html#a19557593

Anyway, the point of this mail is to bring up a different strategy for
CSRF protection, the double-submitted-cookie. Discussion of that are
here http://www.codinghorror.com/blog/archives/001175.html which links
to this article, including a whitepaper:
http://freedom-to-tinker.com/blog/wzeller/popular-websites-vulnerable-cross-site-request-forgery-attacks

The basic idea is:

"When a user visits a site, the site should generate a
(cryptographically strong) pseudorandom value and set it as a cookie
on the user's machine. The site should require every form submission
to include this pseudorandom value as a form value and also as a
cookie value. When a POST request is sent to the site, the request
should only be considered valid if the form value and the cookie value
are the same. When an attacker submits a form on behalf of a user, he
can only modify the values of the form. An attacker cannot read any
data sent from the server or modify cookie values, per the same-origin
policy. This means that while an attacker can send any value he wants
with the form, he will be unable to modify or read the value stored in
the cookie. Since the cookie value and the form value must be the
same, the attacker will be unable to successfully submit a form unless
he is able to guess the pseudorandom value."

For Wicket, this would mean: Generate a pseudorandom value and set is
as a session cookie, when the cookie doesn't yet exist. Insert a
hidden input into each form with the generated value. Validate that
the value equals the cookie when submitting a form. The input and
validation can be abstracted into a Form subclass (or even add it to
Wicket's Form class...).

That really easy to implement, is much more efficient (generate only
one value per user/browser session, store it on the client, not the
server) and is now the most common strategy to protect against CSRF
attacks. I've read a lot about CSRF, and this strategy seems the only
one both easy enough to implement and without holes.

What do you think? Should Wicket support that out-of-the-box?

Jörn

--
-Wicket for love

Nino Martinez Wael
Java Specialist @ Jayway DK
http://www.jayway.dk
+45 2936 7684


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