Refresh token grant
Access tokens eventually expire; however some grants respond with a refresh token which enables the client to refresh the access token.
Flow
The client sends a POST request with following body parameters to the authorization server:
grant_typewith the valuerefresh_tokenrefresh_tokenwith the refresh tokenclient_idwith the the client’s IDclient_secretwith the client’s secretscopewith a space-delimited list of requested scope permissions. This is optional; if not sent the original scopes will be used, otherwise you can request a reduced set of scopes.
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 new JWT signed with the authorization server’s private keyrefresh_tokenan encrypted payload that can be used to refresh the access token when it expires
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();
$accessTokenRepository = new AccessTokenRepository();
$scopeRepository = new ScopeRepository();
$refreshTokenRepository = new RefreshTokenRepository();
// 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
);
$grant = new \League\OAuth2\Server\Grant\RefreshTokenGrant($refreshTokenRepository);
$grant->setRefreshTokenTTL(new \DateInterval('P1M')); // new refresh tokens will expire after 1 month
// Enable the refresh token grant on the server
$server->enableGrantType(
$grant,
new \DateInterval('PT1H') // new access tokens will expire after an hour
);
Implementation
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 to respond to the request
try {
return $server->respondToAccessTokenRequest($request, $response);
} catch (\League\OAuth2\Server\Exception\OAuthServerException $exception) {
return $exception->generateHttpResponse($response);
} catch (\Exception $exception) {
$body = new Stream('php://temp', 'r+');
$body->write($exception->getMessage());
return $response->withStatus(500)->withBody($body);
}
});