OAuth2 by Clojure

oauth.clj

(ns backend.google.oauth
  (:require [cheshire.core :refer [parse-string generate-string]]
            [mount.core :refer [defstate]]
            [buddy.core.keys :as keys]
            [buddy.core.dsa :as dsa]
            [backend.config :refer [env]]
            [org.httpkit.client :as http])
  (:import org.apache.commons.codec.binary.Base64))
(def access_token (atom nil))
(defstate private-key :start (-> env
                                 :google
                                 :private_key
                                 (keys/str->private-key)))
(defn unixtime-now
  ([]
   (-> (java.util.Date.)
       (.getTime)
       (/ 1000)
       (.longValue))))
(defn- enc-header []
  (-> {:alg "RS256"
       :typ "JWT"}
      (generate-string)
      (.getBytes "UTF-8")
      (Base64/encodeBase64String)))
(defn- enc-claim []
  (-> {:iss "worker@code-speech.iam.gserviceaccount.com"
       :scope "https://www.googleapis.com/auth/cloud-platform"
       :aud "https://www.googleapis.com/oauth2/v4/token"
       :exp (+ 3600 (unixtime-now))
       :iat (unixtime-now)}
      (generate-string)
      (.getBytes "UTF-8")
      (Base64/encodeBase64URLSafeString)))
(defn sig []
  (let [h (enc-header)
        c (enc-claim)
        s (-> (clojure.string/join "." [h c])
              (dsa/sign {:key private-key :alg :rsassa-pkcs15+sha256})
              (Base64/encodeBase64URLSafeString))]
    (clojure.string/join "." [h c s])))
(defn access-token []
  (reset! access_token
          (-> @(http/post "https://www.googleapis.com/oauth2/v4/token"
                          {:form-params
                           {:grant_type "urn:ietf:params:oauth:grant-type:jwt-bearer"
                            :assertion (sig)}})
              :body
              (parse-string true)
              :access_token)))