Compojure-api and Buddy

00_notes.md

• (:identity req) is auth backend independent way to access user data
• login and logout implementation depends on auth backend
• :current-user doesn't imply that authentication is required, route should also have :auth-rules if authentication is required

access.clj

(ns backend.access
  (:require [buddy.auth :refer [authenticated?]]))

(defn authenticated [req]
  (authenticated? req))

(defn admin [req]
  (and (authenticated? req)
       (#{:admin} (:role (:identity req)))))

restructure.clj

(ns backend.restructure
  (:require [compojure.api.meta :refer [restructure-param]]
            [backend.access :as access]))

(defn access-error [req val]
  (unauthorized val))

(defn wrap-rule [handler rule]
  (-> handler
      (wrap-access-rules {:rules [{:pattern #".*"
                                   :handler rule}]
                          :on-error access-error})))

(defmethod restructure-param :auth-rules
  [_ rule acc]
  (update-in acc [:middlewares] conj [wrap-rule rule]))

(defmethod restructure-param :current-user
  [_ binding acc]
  (update-in acc [:letks] into [binding `(:identity ~'+compojure-api-request+)]))

session_handler.clj

(ns backend.handler
  (:require [ring.util.http-response :refer [ok unauthorized forbidden]]
            [ring.middleware.session :refer [wrap-session]]
            [compojure.api.sweet :refer :all]
            [buddy.auth :refer [authenticated? throw-unauthorized]]
            [buddy.auth.backends.session :refer [session-backend]]
            [buddy.auth.accessrules :refer [wrap-access-rules]]
            [buddy.auth.middleware :refer [wrap-authentication wrap-authorization]]
            [backend.access :as access]
            backend.restructure))

; FIXME: From config
(def cookie-name "backend-session")

(def auth-backend
  ; By default responds with 401 or 403 if unauthorized
  (session-backend))

(defn wrap-app-session [handler]
  (-> handler
      (wrap-authorization auth-backend)
      (wrap-authentication auth-backend)
      (wrap-session {:cookie-name cookie-name})))

(defapi app'
  {:swagger {:ui "/api-docs"
             :spec "/swagger.json"}}

  (POST "/login" []
    (assoc-in (ok) [:session :identity] {:_id 1, :username "juho", :role :admin}))
  
  (POST "/logout" []
    (assoc-in (ok) [:session :identity] nil))

  (GET "/foo" []
    :auth-rules access/authenticated
    ; :auth-rules {:or [access/authenticated access/other-predicate]}
    ; :auth-rules {:and [access/authenticated access/other-predicate]}
    :current-user user
    (ok user))

(def app
  (-> app'
      wrap-app-session))

token_handler.clj

(ns backend.handler
  (:require [ring.util.http-response :refer [ok unauthorized forbidden]]
            [compojure.api.sweet :refer :all]
            [buddy.auth :refer [authenticated? throw-unauthorized]]
            [buddy.sign.jwt :as jwt]
            [buddy.auth.backends :as backends]
            [buddy.auth.accessrules :refer [wrap-access-rules]]
            [buddy.auth.middleware :refer [wrap-authentication wrap-authorization]]
            [backend.access :as access]
            backend.restructure))

(def secret "FIXME")

(def auth-backend
  (backends/jws {:secret secret
                 :authfn (fn [token-data]
                           ;; TODO: This option can be used (I think) to
                           ;; validate e.g. token expiration date (return nil if not valid)
                           ;; or to retrieve the real data from database based on value of token
                           token-data)}))

(defn wrap-app [handler]
  (-> handler
      ;; TODO: If token only contains token-id which refers to database,
      ;; middleware could be added here to load the data from DB?
      (wrap-authorization auth-backend)
      (wrap-authentication auth-backend)))

(defapi app
  {:swagger {:ui "/api-docs"
             :spec "/swagger.json"
             ;; Adds field to Swagger-UI to provide the value for Authorization header
             :data {:securityDefinitions {:api_key {:type "apiKey" :name "Authorization" :in "header"}}}}}

  (POST "/login" []
    ;; Then token is provided, this value is added to request :identity if the token is valid
    ;; It is good idea to add some data here for token validation, like expiration date
    ;; or token id that is used to validate token against database.
    (ok {:token (jwt/sign {:_id 1 :username "juho"} secret)}))

  (GET "/foo" []
    :auth-rules access/authenticated
    ; :auth-rules {:or [access/authenticated access/other-predicate]}
    ; :auth-rules {:and [access/authenticated access/other-predicate]}
    :current-user user
    (ok user))

(def app
  (-> app'
      wrap-app))

@Deraen thank you so much for publishing this gist! Really helped me pull the pieces together on the Buddy addition to my Compojure API project. ✨