clojure - Set Ring-Anti-Forgery CSRF header token

Question

I'm attempting to implement the Ring-Anti-Forgery library via setting the X-CSRF-Token in the header.

Since I am using static html files I found the built-in hiccup helper, which sets the token in the form, to be useless.

This is my first stab at using Clojure for web development so I'm guessing that I am completely missing what should be obvious to someone with experience.

The instructions from the README state:

The middleware also looks for the token in the X-CSRF-Token and X-XSRF-Token header fields. This behavior can be customized further using the :read-token option:

(defn get-custom-token [request]
  (get-in request [:headers "x-forgery-token"]))

(def app
  (-> handler
      (wrap-anti-forgery {:read-token get-custom-token})
      (wrap-session)))

I have added the above to handler.clj without any success.

project.clj

(defproject hooktale "0.0.1"
  :description "Hooktale iOS App Website"
  :url "http://www.hooktale.com"
  :repositories {"sonartype releases" "https://oss.sonatype.org/content/repositories/releases/"}
  :source-paths ["src/clj" "src/cljs"]
  :dependencies [[org.clojure/clojure "1.5.1"]
                 [org.clojure/clojurescript "0.0-2080"]
                 [org.clojure/java.jdbc "0.3.0-beta2"]
                 [compojure "1.1.6"]
                 [com.mchange/c3p0 "0.9.5-pre5"]
                 [org.postgresql/postgresql "9.3-1100-jdbc4"]
                 [ring-anti-forgery "0.3.0"]]
  :plugins [[lein-ring "0.8.8"]
            [lein-cljsbuild "1.0.1-SNAPSHOT"]]
  :ring {:handler hooktale.handler/app}
  :profiles {:dev {:plugins [[javax.servlet/servlet-api "2.5"]
                             [ring-mock "0.1.5"]]
                   :cljsbuild {:builds [{:source-paths ["src/cljs"]
                                         :compiler {:optimizations :advanced
                                                    :pretty-print false
                                                    :output-to "resources/public/js/trout.js"}}]}}})

handler.clj

(ns hooktale.handler
  (:require [compojure.core :refer [defroutes GET POST]]
            [compojure.handler :refer [site]]
            [compojure.route :refer [resources not-found]]
            [clojure.java.io :refer [resource]]
            [ring.middleware.anti-forgery :refer :all]
            [ring.middleware.session :refer [wrap-session]]
            [hooktale.controllers.prospect :refer [create-prospect]]))

(defn get-custom-token [request]
  (get-in request [:headers "x-forgery-token"]))

(defroutes app-routes
  (GET "/" [] (resource "public/index.html"))
  (POST "/" [email] (create-prospect email))
  (resources "/")
  (not-found "Not Found"))

(def app
  (->
   (site app-routes)
   (wrap-anti-forgery {:read-token get-custom-token})
   (wrap-session)))

Sending a request to the page returns the following info:

curl -I localhost:3000

HTTP/1.1 200 OK
Date: Fri, 06 Dec 2013 16:30:45 GMT
Set-Cookie: ring-session=0b2a477f-9352-4fd8-a3c3-a6b6f8d9e063;Path=/
Content-Length: 0
Server: Jetty(7.6.8.v20121106)

curl -X POST -d '{:email "[email protected]"}' localhost:3000

<h1>Invalid anti-forgery token</h1>

The function in ring.middleware.anti-forgery that I thought would allow me to set the token in the header without having to set the hidden token value inside the form field.

(defn- default-request-token [request]
  (or (-> request form-params (get "__anti-forgery-token"))
      (-> request :headers (get "x-csrf-token"))
      (-> request :headers (get "x-xsrf-token"))))

If I am reading it correctly, it will check for the token in the form, if not there it will check for the x-csrf-token then the x-xsrf-token in the header.

I seem to be having difficulty in actually setting the value of x-csrf-token or x-xsrf-token in the header.

Curl responses

View the Cookie set by ring-session:

curl -I localhost:3000

HTTP/1.1 200 OK
Date: Fri, 06 Dec 2013 19:52:22 GMT
Set-Cookie: ring-session=b02dd6f8-74b8-4ce0-a1d6-07251dadb9aa;Path=/
Content-Length: 0
Server: Jetty(7.6.8.v20121106)

Setting the X-CSRF-Token:

curl -v --header "X-CSRF-Token: b02dd6f8-74b8-4ce0-a1d6-07251dadb9aa;Path=/" -X POST -d '{:email "[email protected]"}' localhost:3000

* Adding handle: conn: 0x7fd3ab004000
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 0 (0x7fd3ab004000) send_pipe: 1, recv_pipe: 0
* About to connect() to localhost port 3000 (#0)
*   Trying ::1...
* Connected to localhost (::1) port 3000 (#0)
> POST / HTTP/1.1
> User-Agent: curl/7.30.0
> Host: localhost:3000
> Accept: */*
> X-CSRF-Token: b02dd6f8-74b8-4ce0-a1d6-07251dadb9aa;Path=/
> Content-Length: 27
> Content-Type: application/x-www-form-urlencoded
>
* upload completely sent off: 27 out of 27 bytes
< HTTP/1.1 403 Forbidden
< Date: Fri, 06 Dec 2013 19:54:52 GMT
< Content-Type: text/html;charset=ISO-8859-1
< Content-Length: 35
* Server Jetty(7.6.8.v20121106) is not blacklisted
< Server: Jetty(7.6.8.v20121106)
<
* Connection #0 to host localhost left intact
<h1>Invalid anti-forgery token</h1>

Answer 1

I created a repository https://github.com/edbond/CSRF with example. Readme describes process needed to POST requests with CSRF token.

In short (for API calls, curl):

1. Get CSRF Token and session cookie from server (server will store CSRF token inside your session which identified by cookie)

2. Send X-CSRF-Token and cookie along with POST request (server will compare CSRF token with that stored inside your session identified by cookie)

cookie -> session -> CSRF-Token

For HTML, form POSTing it should be enough to include (anti-forgery-field) to forms. Note, you can also send form field instead of header using curl.

HTH