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buddy-auth - Auth/Authz facilities for ring based apps.

Introduction

buddy-auth is a module that provides authentication and authorization facilites or ring and ring based web applications.

Project Maturity

Since buddy-auth is a young project there may be some API breakage.

Install

The simplest way to use buddy-auth in a clojure project is by including it in your project.clj dependency vector:

[buddy/buddy-auth "2.1.0"]

This package is intended to be used with jdk7 or jdk8.

Authentication

Introduction

The buddy’s approach for authentication is pretty simple and explicit. In contrast to the vast majority of authentication libraries that I know, buddy does not mix authentication process with the authorization.

It is implemented as a pluggable backend that can be picked as is or you can implement a new one with simple steps. This is a list of builtin backends:

Table 1. List of builtin backends.
Backend nameNamespace

Http Basic

buddy.auth.backends/basic

Session

buddy.auth.backends/session

Token

buddy.auth.backends/token

Signed JWT

buddy.auth.backends/jws

Encrypted JWT

buddy.auth.backends/jwe

If you are not happy with the built-in backends, you can implement your own and use it with buddy-auth middleware without any problems.

The authentication process works mainly in two steps:

  1. parse: that is responsible for analyzing the request and read the auth related data (e.g. Authorization header, url params, etc..)

  2. auth: with the data obtained from parse step just try to authenticate the the request (e.g. simple access to database for obtain the possible user, using a self contained jws/jwe token, check a key in the session, etc…​)

This step does not raise any exceptions and is completely transparent to the user. The authentication process responsibility is to determine if a request is anonymous or is authenticated, nothing more.

Backends

Http-Basic

The HTTP Basic authentication backend is one of the simplest and most insecure authentication systems, but is a good first step to understanding how buddy-auth authentication works.

Example ring handler/view
(require '[ring.util.response :refer (response)])

;; Simple ring handler. This can also be a compojure router handler
;; or anything else compatible with ring middleware.

(defn my-handler
  [request]
  (if (:identity request)
    (response (format "Hello %s" (:identity request)))
    (response "Hello Anonymous")))

The basic step to check if a request is authenticated or not, is just to check if it comes with an :identity key and it contains a logical true (exists and contains something different to nil or false).

This is how the authentication backend should be setup:

(require '[buddy.auth.backends :as backends])

(defn my-authfn
  [request authdata]
  (let [username (:username authdata)
        password (:password authdata)]
    username))

(def backend (backends/basic {:realm "MyApi"
                              :authfn my-authfn}))

The authfn is responsible for the second step of authentication. It receives the parsed auth data from request and should return a logical true value (e.g a user id, user instance, mainly something different to nil and false). And it will be called only if step 1 (parse) returns something.

And finally, you should wrap your ring handler with authentication middleware:

(require '[buddy.auth.middleware :refer [wrap-authentication]])

;; Define the main handler with *app* name wrapping it
;; with authentication middleware using an instance of the
;; just created http-basic backend.

;; Define app var with handler wrapped with _buddy-auth_'s authentication
;; middleware using the previously defined backend.

(def app (wrap-authentication my-handler backend))

From now, all requests that reach my-handler will be properly authenticated.

You can see a complete example of using this backend here.

Session

The session backend has the simplest implementation because it relies entirely on ring session support.

The authentication process of this backend consists of checking the :identity keyword in session. If it exists and is a logical true, it is automatically forwarded to the request under the :identity property.

Example creating a session backend instance and wrapping our handler
(require '[buddy.auth.backends :as backends])

;; Create an instance
(def backend (backends/session))

;; Wrap the ring handler.
(def app (-> my-handler
             (wrap-authentication backend)))

You can see a complete example of using this backend here.

Token

This is a backend that uses tokens for authenticating the user. It behaves very similarly to the basic-auth backend with the difference that instead of authenticating with credentials it authenticates with a simple token.

Let’s see an example:

(require '[buddy.auth.backends :as backends])

;; Define a in-memory relation between tokens and users:
(def tokens {:2f904e245c1f5 :admin
             :45c1f5e3f05d0 :foouser})

;; Define an authfn, function with the responsibility
;; to authenticate the incoming token and return an
;; identity instance

(defn my-authfn
  [request token]
  (let [token (keyword token)]
    (get tokens token nil)))

;; Create an instance
(def backend (backends/token {:authfn my-authfn}))

;; Wrap the ring handler.
(def app (-> my-handler
             (wrap-authentication backend)))

The process of authentication of this backend consists in parsing the "Authorization" header, extracting the token and in case the token is extracted successfully, call the authfn with extracted token.

This is a possible aspect of the authorization header
Authorization: Token 45c1f5e3f05d0

The authfn should return something that will be associated to the :identity key in the request.

The responsability of buddy is just parse request and call the user function authenticate it. The token building and storage is a user responsability.

You can see a complete example of using this backend here.

Signed JWT

Is a backend that uses signed and self contained tokens to authenticate the user.

It behaves very similarly to the Token backend (previously explained) with the difference that this one does not need additional user defined logic to validate tokens, because as we previously said, everything is self contained.

This type of token mechanism enables a complete stateless authentication because the server does not need to store the token and related information, the token will contain all the needed information for authentication.

Let’s see a demonstrative example:

(require '[buddy.auth.backends :as backends])
(require '[buddy.auth.middleware :refer (wrap-authentication)])

(def secret "mysecret")
(def backend (backends/jws {:secret secret}))

;; and wrap your ring application with
;; the authentication middleware

(def app (-> your-ring-app
             (wrap-authentication backend)))

Now you should have a login endpoint in your ring application that will have the responsibility of generating valid tokens:

(require '[buddy.sign.jwt :as jwt])
(require '[cheshire.core :as json])

(defn login-handler
  [request]
  (let [data (:form-params request)
        user (find-user (:username data)   ;; (implementation ommited)
                        (:password data))
        token (jwt/sign {:user (:id user)} secret)]
    {:status 200
     :body (json/encode {:token token})
     :headers {:content-type "application/json"})))

For more details about jwt, see the buddy-sign documentation.

Some valuable resources for learning about stateless authentication are:

You can see a complete example of using this backend here.

Encrypted JWT

This backend is almost identical to the previous one (signed JWT).

The main difference is that the backend uses JWE (Json Web Encryption) instead of JWS (Json Web Signature) and it has the advantage that the content of the token is encrypted instead of simply signed. This is useful when token may contain some additional user information that should not be public.

It will look similar to the previous (jws) example but instead using jwe with asymmetric key encryption algorithm:

(require '[buddy.auth.backends :as backends])
(require '[buddy.auth.middleware :refer (wrap-authentication)])
(require '[buddy.sign.jwe :as jwe])
(require '[buddy.core.keys :as keys])

(def pubkey (keys/public-key "pubkey.pem"))
(def privkey (keys/private-key "privkey.pem"))

(def backend
  (backends/jwe {:secret privkey
                 :options {:alg :rsa-oaep
                           :enc :a128-hs256}}))

;; and wrap your ring application with
;; the authentication middleware

(def app (-> your-ring-app
             (wrap-authentication backend)))

The corresponding login endpoint should have a similar aspect to this:

(require '[buddy.sign.jwt :as jwt])
(require '[cheshire.core :as json])

(defn login-handler
  [request]
  (let [data (:form-params request)
        user (find-user (:username data)   ;; (implementation ommited)
                        (:password data))
        token (jwt/encrypt {:user (:id user)} pubkey
                           {:alg :rsa-oaep :enc :a128-hs256})]
    {:status 200
     :body (json/encode {:token token})
     :headers {:content-type "application/json"})))

In order to use any asymmetric encryption algorithm, you should have private/public key pair. If you don’t have one, don’t worry, it is very easy to generate it using openssl, see this faq entry.

You can see a complete example of using this backend here.

Authorization

The second part of the auth process is authorization.

The authorization system is split into two parts: generic authorization and access-rules (explained in the next section).

The generic one is based on exceptions, and consists in raising an unauthorized exception in case the request is considered unauthorized. The access rules system is based on some kind of rules attached to the handler or an URI and that rules determine if a request is authorized or not.

Exception-Based

This authorization approach is based on wrapping everything in a try/catch block which only handles specific exceptions. When an unauthorized exception is caught, it executes a specific function to handle it or reraises the exception.

With this approach you can define your own middlewared/decorators using custom authorization logic with fast skip, raising an unauthorized exception using the throw-unauthorized function.

Example ring handler raising an unauthorized exception.
(require '[buddy.auth :refer [authenticated? throw-unauthorized]])
(require '[ring.util.response :refer (response redirect)])

(defn home-controller
  [request]
  (when (not (authenticated? request))
    (throw-unauthorized {:message "Not authorized"}))
  (response "Hello World"))

Just like the authentication system, authorization is also implemented using plugable backends.

All built-in backends already implement the authorization protocol with default behavior. The default behavior can be overridden passing the :unauthorized-handler option to the backend constructor:

(require '[buddy.auth.backends :as backends])
(require '[buddy.auth.middleware :refer [wrap-authentication wrap-authorization]])

;; Simple self defined handler for unauthorized requests.
(defn my-unauthorized-handler
  [request metadata]
  (-> (response "Unauthorized request")
      (assoc :status 403)))

(def backend (backends/basic
              {:realm "API"
               :authfn my-auth-fn
               :unauthorized-handler my-unauthorized-handler}))

(def app (-> your-handler
             (wrap-authentication backend)
             (wrap-authorization backend)))

Access Rules

The access rules system is another part of authorization. It consists of matching an url to specific access rules logic.

The access rules consist of an ordered list that contains mappings between urls and rule handlers using clout url matching syntax or regular expressions.

This is an example of an access rule using the clout syntax.
[{:uri "/foo"
  :handler user-access}
This is an example of an access rule with more than one url matching using the clout syntax.
[{:uris ["/foo" "/bar"]
  :handler user-access}
The same example but using regular expressions.
[{:pattern #"^/foo$"
  :handler user-access}

An access rule can also match against certain HTTP methods, by using the :request-method option. :request-method can be a keyword or a set of keywords.

An example of an access rule that matches only GET requests.
[{:uri "/foo"
  :handler user-access
  :request-method :get}

Rules Handlers

The rule handler is a plain function that accepts a request as a parameter and should return accessrules/success or accessrules/error.

The success is a simple mark that means that handlers pass the validation and error is a mark that means the opposite, that the handler does not pass the validation. Instead of returning plain boolean values, this approach allows handlers to return errors messages or even a ring response.

This is a simple example of the aspect of one rule handler.
(require '[buddy.auth.accessrules :refer (success error)])

(defn authenticated-user
  [request]
  (if (:identity request)
    true
    (error "Only authenticated users allowed")))

These values are considered success marks: true and success instances. These are considered error marks: nil, false, and error instances. Error instances may contain a string as an error message or a ring response hash-map.

Also, a rule handler can be a composition of several rule handlers using logical operators.

This is the aspect of composition of rule-handlers
{:and [authenticated-user other-handler]}
{:or [authenticated-user other-handler]}

;; Logical expressions can be nested as deep as you wish
;; with hypotetical rule handlers with self descriptive name.
{:or [should-be-admin
      {:and [should-be-safe
             should-be-authenticated]}]}}

This is an example of how a composed rule handler can be used in an access rules list:

[{:pattern #"^/foo$"
  :handler {:and [authenticated-user admin-user]}}]

Additionally, if you are using clout based syntax for matching access rules, the request in a rule handler will contain :match-params with clout matched uri params.

Usage

Now, knowing how access rules and rule handlers can be defined, it is time to see how we can use it in our ring applications.

buddy-auth exposes two ways to do it:

  • Using a wrap-access-rules middleware.

  • Using a restrict decorator for assigning specific rules handlers to concrete ring handler.

Here are couple of examples of how we could do it:

Using wrap-access-rules middleware.
;; Rules handlers used on this example are ommited for code clarity
;; Each handler represents authorization logic indicated by its name.

(def rules [{:pattern #"^/admin/.*"
             :handler {:or [admin-access operator-access]}}
            {:pattern #"^/login$"
             :handler any-access}
            {:pattern #"^/.*"
             :handler authenticated-access}])

;; Define default behavior for not authorized requests
;;
;; This function works like a default ring compatible handler
;; and should implement the default behavior for requests
;; which are not authorized by any defined rule

(defn on-error
  [request value]
  {:status 403
   :headers {}
   :body "Not authorized"})

;; Wrap the handler with access rules (and run with jetty as example)
(defn -main
  [& args]
  (let [options {:rules rules :on-error on-error}
        app     (wrap-access-rules your-app-handler options)]
    (run-jetty app {:port 3000})))

If a request uri does not match any regular expression then the default policy is used. The default policy in buddy-auth is allow but you can change the default behavior specifying a :reject value in the :policy option.

Additionally, instead of specifying the global on-error handler, you can set a specific behavior on a specific access rule, or use the :redirect option to simply redirect a user to specific url.

Let’s see an example.
(def rules [{:pattern #"^/admin/.*"
             :handler {:or [admin-access operator-access]}
             :redirect "/notauthorized"}
            {:pattern #"^/login$"
             :handler any-access}
            {:pattern #"^/.*"
             :handler authenticated-access
             :on-error (fn [req _] (response "Not authorized ;)"))}])

The access rule options always takes precedence over the global ones.

Then, if you don’t want an external rules list and simply want to apply some rules to specific ring views/handlers, you can use the restrict decorator. Let’s see it in action:

(require '[buddy.auth.accessrules :refer [restrict]])

(defn home-controller
  [request]
  {:body "Hello World" :status 200})

(defroutes app
  (GET "/" [] (restrict home-controller {:handler should-be-authenticated
                                         :on-error on-error}))

Examples

Http Basic Auth Example

This example tries to show the way to setup http basic auth in a simple ring based application.

Just run the following commands:

git clone https://github.com/funcool/buddy-auth.git
cd ./buddy-auth/
lein with-profile +httpbasic-example run

And redirect your browser to http://localhost:3000/.

The credentials are: admin / secret and test / secret.

You can see the example code here: https://github.com/funcool/buddy-auth/tree/master/examples/httpbasic

Session Auth Example

This example tries to show the way to setup session based auth in a simple ring based application.

Just run the following commands:

git clone https://github.com/funcool/buddy-auth.git
cd ./buddy-auth/
lein with-profile +session-example run

And redirect your browser to http://localhost:3000/.

The credentials are: admin / secret and test / secret.

You can see the example code here: https://github.com/funcool/buddy-auth/tree/master/examples/session

Token Auth Example

This example tries to show the way to setup token based auth in a simple ring based application.

Just run the following commands:

git clone https://github.com/funcool/buddy-auth.git
cd ./buddy-auth/
lein with-profile +token-example run

You can use curl for play with the authentication example:

Obtain the token performing a login request.
$ curl -v -X POST -H "Content-Type: application/json" -d '{"username": "admin", "password": "secret"}' http://localhost:3000/login
* Connected to localhost (::1) port 3000 (#0)
> POST /login HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/7.46.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 43
>
* upload completely sent off: 43 out of 43 bytes
< HTTP/1.1 200 OK
< Date: Mon, 04 Jan 2016 13:54:02 GMT
< Content-Type: application/json; charset=utf-8
< Content-Length: 44
< Server: Jetty(9.2.10.v20150310)
<
* Connection #0 to host localhost left intact
{"token":"fe562338bf1604bd175722e32a4d7115"}
Perform an authenticated request (using previously obtained token).
$ curl -v -X GET -H "Content-Type: application/json" -H "Authorization: Token fe562338bf1604bd175722e32a4d7115" http://localhost:3000/
* Connected to localhost (::1) port 3000 (#0)
> GET / HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/7.46.0
> Accept: */*
> Content-Type: application/json
> Authorization: Token fe562338bf1604bd175722e32a4d7115
>
< HTTP/1.1 200 OK
< Date: Mon, 04 Jan 2016 13:54:40 GMT
< Content-Type: application/json; charset=utf-8
< Content-Length: 55
< Server: Jetty(9.2.10.v20150310)
<
* Connection #0 to host localhost left intact
{"status":"Logged","message":"hello logged user:admin"}

You can see the example code here: https://github.com/funcool/buddy-auth/tree/master/examples/token

JWE Token Auth Example

This example tries to show the way to setup jwe stateless token based auth in a simple ring based application.

Just run the following commands:

git clone https://github.com/funcool/buddy-auth.git
cd ./buddy-auth/
lein with-profile +token-example run

You can use curl for play with the authentication example:

Obtain the token performing a login request.
$ curl -v -X POST -H "Content-Type: application/json" -d '{"username": "admin", "password": "secret"}' http://localhost:3000/login
* Connected to localhost (::1) port 3000 (#0)
> POST /login HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/7.46.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 43
>
* upload completely sent off: 43 out of 43 bytes
< HTTP/1.1 200 OK
< Date: Mon, 04 Jan 2016 13:52:11 GMT
< Content-Type: application/json; charset=utf-8
< Content-Length: 189
< Server: Jetty(9.2.10.v20150310)
<
* Connection #0 to host localhost left intact
{"token":"eyJhbGciOiJBMjU2S1ciLCJ0eXAiOiJKV1MiLCJlbmMiOiJBMTI4R0NNIn0.Q672y_lD3bOU_qm5U0RDKS-YszRHfkFu.vDZaAJPz8uL5q1A4.LonJtHZMA_Ty53YBmr1zpE7-SIbTJgVgme--Tjj25dHN.goYEyM3JZgYlbARo8CDk0g"}
Perform an authenticated request (using previously obtained token).
$ curl -v -X GET -H "Content-Type: application/json" -H "Authorization: Token eyJhbGciOiJBMjU2S1ciLCJ0eXAiOiJKV1MiLCJlbmMiOiJBMTI4R0NNIn0.Q672y_lD3bOU_qm5U0RDKS-YszRHfkFu.vDZaAJPz8uL5q1A4.LonJtHZMA_Ty53YBmr1zpE7-SIbTJgVgme--Tjj25dHN.goYEyM3JZgYlbARo8CDk0g" http://localhost:3000/
* Connected to localhost (::1) port 3000 (#0)
> GET / HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/7.46.0
> Accept: */*
> Content-Type: application/json
> Authorization: Token eyJhbGciOiJBMjU2S1ciLCJ0eXAiOiJKV1MiLCJlbmMiOiJBMTI4R0NNIn0.Q672y_lD3bOU_qm5U0RDKS-YszRHfkFu.vDZaAJPz8uL5q1A4.LonJtHZMA_Ty53YBmr1zpE7-SIbTJgVgme--Tjj25dHN.goYEyM3JZgYlbARo8CDk0g
>
< HTTP/1.1 200 OK
< Date: Mon, 04 Jan 2016 13:52:59 GMT
< Content-Type: application/json; charset=utf-8
< Content-Length: 84
< Server: Jetty(9.2.10.v20150310)
<
* Connection #0 to host localhost left intact
{"status":"Logged","message":"hello logged user {:user \"admin\", :exp 1451919131}"}

You can see the example code here: https://github.com/funcool/buddy-auth/tree/master/examples/jwe

Signed JWT Auth Example

This example tries to show the way to setup jws stateless token based auth in a simple ring based application.

Just run the following commands:

git clone https://github.com/funcool/buddy-auth.git
cd ./buddy-auth/
lein with-profile +jws-example run

You can use curl for play with the authentication example:

Obtain the token performing a login request.
$ curl -v -X POST -H "Content-Type: application/json" -d '{"username": "admin", "password": "secret"}' http://localhost:3000/login
> POST /login HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/7.46.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 43
>
* upload completely sent off: 43 out of 43 bytes
< HTTP/1.1 200 OK
< Date: Mon, 04 Jan 2016 13:49:30 GMT
< Content-Type: application/json; charset=utf-8
< Content-Length: 180
< Server: Jetty(9.2.10.v20150310)
<
* Connection #0 to host localhost left intact
{"token":"eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXUyJ9.eyJ1c2VyIjoiYWRtaW4iLCJleHAiOjE0NTE5MTg5NzB9.Kvpr1jW7JBCZYUlFjAf7xnqMZSTpSVggAgiZ6_RGZuTi1wUuP_-E8MJff23GuCwpT9bbbHNTk84uV2cdg7rKTw"}
Perform an authenticated request (using previously obtained token).
$ curl -v -X GET -H "Content-Type: application/json" -H "Authorization: Token eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXUyJ9.eyJ1c2VyIjoiYWRtaW4iLCJleHAiOjE0NTE5MTg5NzB9.Kvpr1jW7JBCZYUlFjAf7xnqMZSTpSVggAgiZ6_RGZuTi1wUuP_-E8MJff23GuCwpT9bbbHNTk84uV2cdg7rKTw" http://localhost:3000/
* Connected to localhost (::1) port 3000 (#0)
> GET / HTTP/1.1
> Host: localhost:3000
> User-Agent: curl/7.46.0
> Accept: */*
> Content-Type: application/json
> Authorization: Token eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXUyJ9.eyJ1c2VyIjoiYWRtaW4iLCJleHAiOjE0NTE5MTg5NzB9.Kvpr1jW7JBCZYUlFjAf7xnqMZSTpSVggAgiZ6_RGZuTi1wUuP_-E8MJff23GuCwpT9bbbHNTk84uV2cdg7rKTw
>
< HTTP/1.1 200 OK
< Date: Mon, 04 Jan 2016 13:50:15 GMT
< Content-Type: application/json; charset=utf-8
< Content-Length: 84
< Server: Jetty(9.2.10.v20150310)
<
* Connection #0 to host localhost left intact
{"status":"Logged","message":"hello logged user {:user \"admin\", :exp 1451918970}"}

You can see the example code here: https://github.com/funcool/buddy-auth/tree/master/examples/jws

FAQ

What is the difference with Friend?

buddy-auth authorization/authentication facilities are more low level and less opinionated than friend, and allow you to easily build other high level abstractions over them. Technically, friend abstraction can be built on top of buddy-auth.

How can I use buddy with liberator?

By design, buddy has authorization and authentication well separated. This helps a lot if you want use only one part of it (ex: authentication only) without including the other.

In summary: yes, you can use buddy-auth with liberator.

Can I use buddy-auth with pedestal?

Although is not mentioned in this documentation, you can use buddy-auth with pedestal withoy any problems.

https://juxt.pro/blog/posts/securing-your-clojurescript-app.html

Can I use buddy-auth with catacumba?

Not directly.

The design of buddy-auth api is intrinsically blocking just because ring and ring based abstractions are also blocking. However catacumba is asyncronous toolkit and it comes with its own, builtint variant of buddy-auth designed for asynchronous workflow (reusing the underlying buddy-sign, buddy-core and buddy-hashers modules).

Developers Guide

Contributing

Unlike Clojure and other Clojure contributed libraries buddy-auth does not have many restrictions for contributions. Just open an issue or pull request.

Philosophy

Five most important rules:

  • Beautiful is better than ugly.

  • Explicit is better than implicit.

  • Simple is better than complex.

  • Complex is better than complicated.

  • Readability counts.

All contributions to buddy-auth should keep these important rules in mind.

Get the Code

buddy-auth is open source and can be found on github.

You can clone the public repository with this command:

git clone https://github.com/funcool/buddy-auth

Run tests

For running tests just execute this:

lein test

License

buddy-auth is licensed under Apache 2.0 License. You can see the complete text of the license on the root of the repository on LICENSE file.

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