How to Prevent CSRF in Play [2.0] Using Scala?

Question

A lot of web frameworks have a standard setup for generating forms with auth tokens.

Do I have to create such measures manually, or does Play come with a build in means of prevening CSRF?

The documentation on the Play website doesn't seem to address this.

Answer 1

I use the play2-authenticitytoken module:

The authenticity token is a way around one of the most serious internet security threats: CRSF attacks. It ensures that the client submitting a form is the one who received the page (and not a hacker who stole your session data).

How it works:

In a nutshell:

1. on every form post, we add a hidden parameter containing a uuid
2. the uuid is signed and its signature is stored in the session (which translated into a cookie)

When the user submits the form, we get: the uuid, the signature and the other form inputs.

1. We sign the incoming uuid again
2. Validation passes if the signatures match (session.sign=uuid.sign)

Should an attacker inject a different id, he will never figure how to generate the correct signature.