Updated client credentials grant

auth-server-client-credentials.md

@@ -6,25 +6,39 @@ permalink: /authorization-server/client-credentials-grant/
 
 # Client credentials grant
 
-This grant is similar to the resource owner credentials grant except only the client’s credentials are used to authenticate a request for an access token. Again this grant should only be allowed to be used by trusted clients.
-
 This grant is suitable for machine-to-machine authentication, for example for use in a cron job which is performing maintenance tasks over an API. Another example would be a client making requests to an API that don’t require user’s permission.
 
+## Flow
+
+The client sends a POST request with following body parameters to the authorization server:
+
+* `grant_type` with the value `client_credentials`
+* `client_id` with the the client's ID
+* `client_secret` with the client's secret
+* `scope` with a space-delimited list of requested scope permissions.
+
+The authorization server will respond with a JSON object containing the following properties:
+
+* `token_type` with the value `Bearer`
+* `expires_in` with an integer representing the TTL of the access token
+* `access_token` a JWT signed with the authorization server's private key
+
 ## Setup
 
 Wherever you initialize your objects, initialize a new instance of the authorization server and bind the storage interfaces and authorization code grant:
 
 {% highlight php %}
-// Your implementation of the required repositories
+// Init our repositories
 $clientRepository = new ClientRepository();
 $accessTokenRepository = new AccessTokenRepository();
 $scopeRepository = new ScopeRepository();
 
+// Path to public and private keys
 $privateKeyPath = 'file://path/to/private.key';
 $publicKeyPath = 'file://path/to/public.key';
         
 // Setup the authorization server
-$server = new Server(
+$server = new \League\OAuth2\Server\Server(
     $clientRepository,
     $accessTokenRepository,
     $scopeRepository,
@@ -34,7 +48,7 @@ $server = new Server(
 
 // Enable the client credentials grant on the server with a token TTL of 1 hour
 $server->enableGrantType(
-    new ClientCredentialsGrant(),
+    new \League\OAuth2\Server\Grant\ClientCredentialsGrant(),
     new \DateInterval('PT1H')
 );
 {% endhighlight %}
@@ -46,19 +60,17 @@ The client will request an access token so create an `/access_token` endpoint.
 {% highlight php %}
 $app->post('/access_token', function (ServerRequestInterface $request, ResponseInterface $response) use ($app) {
 
-    // Retrieve the authorization server from the DI container
+    /* @var \League\OAuth2\Server\Server $server */
     $server = $app->getContainer()->get(Server::class);
 
+    // Try to respond to the request 
     try {
-        // A successful response with an access token
         return $server->respondToRequest($request, $response);
         
-    } catch (OAuthServerException $exception) {
+    } catch (\League\OAuth2\Server\Exception\OAuthServerException $exception) {
-        // A correctly formatted OAuth error response
         return $exception->generateHttpResponse($response);
         
     } catch (\Exception $exception) {
-        // An unknown server error
         $body = new Stream('php://temp', 'r+');
         $body->write($exception->getMessage());
         return $response->withStatus(500)->withBody($body);