oauth2-server/auth-server-client-credentials.md

layout	title	permalink
default	Authorization server with client credentials grant	/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.

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 $clientRepository = new ClientRepository(); $accessTokenRepository = new AccessTokenRepository(); $scopeRepository = new ScopeRepository();

$privateKeyPath = 'file://path/to/private.key'; $publicKeyPath = 'file://path/to/public.key';

// Setup the authorization server $server = new Server( $clientRepository, $accessTokenRepository, $scopeRepository, $privateKeyPath, $publicKeyPath );

// Enable the client credentials grant on the server with a token TTL of 1 hour $server->enableGrantType( new ClientCredentialsGrant(), new \DateInterval('PT1H') ); {% endhighlight %}

Implementation

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
$server = $app->getContainer()->get(Server::class);

try {
    // A successful response with an access token
    return $server->respondToRequest($request, $response);
    
} catch (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);
}

}); {% endhighlight %}