[Zope-dev] (optional) CSRF protection in zope.formlib

[Jan-Wijbrand Kolman]

Hi,

I've been working on CSRF protection for zope.formlib.

I have a "csrfprotection" branch in my zope.formlib fork on github. The 
changes against the current zope.formlib mainline can be found here:

https://github.com/janwijbrand/zope.formlib/compare/csrfprotection

When creating form components based on zope.formlib.form.FormBase, one 
can enable this protection just by setting the attribute ``protected`` 
to True on the component.

This implementation is based on the following assumptions:

* We do not want to keep server-side state(!)

* An "attacker" that attempts CSRF cannot get to information stored in 
cookies that are meant for the domain of the (forged) request.

* The token stored in the cookie is sufficiently random and long, to be 
practically "unguessable" by the attacker.

* The form submit is deemed valid as long as the token in the cookie is 
identical to a hidden input value that is part of the form submit.

My questions:

* Do you find this feature useful enough to be, in principle, included 
in zope.formlib?

* I'd like to kindly request someone to review my branch and provide 
feedback.

The included test cases describe a few more questions and concerns about 
this implementation.

Thank you in advance!

kind regards, jw