Client credentials grant
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_typewith the valueclient_credentialsclient_idwith the client’s IDclient_secretwith the client’s secretscopewith a space-delimited list of requested scope permissions.
The authorization server will respond with a JSON object containing the following properties:
token_typewith the valueBearerexpires_inwith an integer representing the TTL of the access tokenaccess_tokena 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:
// Init our repositories
$clientRepository = new ClientRepository(); // instance of ClientRepositoryInterface
$scopeRepository = new ScopeRepository(); // instance of ScopeRepositoryInterface
$accessTokenRepository = new AccessTokenRepository(); // instance of AccessTokenRepositoryInterface
// Path to public and private keys
$privateKey = 'file://path/to/private.key';
//$privateKey = new CryptKey('file://path/to/private.key', 'passphrase'); // if private key has a pass phrase
$encryptionKey = 'lxZFUEsBCJ2Yb14IF2ygAHI5N4+ZAUXXaSeeJm6+twsUmIen'; // generate using base64_encode(random_bytes(32))
// Setup the authorization server
$server = new \League\OAuth2\Server\AuthorizationServer(
$clientRepository,
$accessTokenRepository,
$scopeRepository,
$privateKey,
$encryptionKey
);
// Enable the client credentials grant on the server
$server->enableGrantType(
new \League\OAuth2\Server\Grant\ClientCredentialsGrant(),
new \DateInterval('PT1H') // access tokens will expire after 1 hour
);
Implementation
Please note: These examples here demonstrate usage with the Slim Framework; Slim is not a requirement to use this library, you just need something that generates PSR7-compatible HTTP requests and responses.
The client will request an access token so create an /access_token endpoint.
$app->post('/access_token', function (ServerRequestInterface $request, ResponseInterface $response) use ($app) {
/* @var \League\OAuth2\Server\AuthorizationServer $server */
$server = $app->getContainer()->get(AuthorizationServer::class);
try {
// Try to respond to the request
return $server->respondToAccessTokenRequest($request, $response);
} catch (\League\OAuth2\Server\Exception\OAuthServerException $exception) {
// All instances of OAuthServerException can be formatted into a HTTP response
return $exception->generateHttpResponse($response);
} catch (\Exception $exception) {
// Unknown exception
$body = new Stream('php://temp', 'r+');
$body->write($exception->getMessage());
return $response->withStatus(500)->withBody($body);
}
});