Google PHP Client API: Insufficient Permission

Question

I have PHP code that use Google PHP Client API to use Drive service.

<?php
require_once 'Google/Client.php';
require_once 'Google/Service/Drive.php';

const CLIENT_ID = '[MYCLIENTID]';
const SERVICE_ACCOUNT_NAME = '[MYSERVICEACCOUNID]';

// Make sure you keep your key.p12 file in a secure location, and isn't
// readable by others.
const KEY_FILE = './[MYPRIVATEKEY].p12';

// Load the key in PKCS 12 format (you need to download this from the
// Google API Console when the service account was created.
$client = new Google_Client();
$client->setApplicationName("Google Drive Sample");

$key = file_get_contents(KEY_FILE);
$client->setClientId(CLIENT_ID);
$client->setAssertionCredentials(new Google_Auth_AssertionCredentials(
  SERVICE_ACCOUNT_NAME,
  array('https://www.googleapis.com/auth/drive'),
  $key)
);

$client->setClientId(CLIENT_ID);

if ($client->getAuth()->isAccessTokenExpired()) {
  $client->getAuth()->refreshTokenWithAssertion();
}

// Get the json encoded access token.
$token = $client->getAccessToken();

echo "<pre>";
$service = new Google_Service_Drive($client);
$service->apps->listApps();
echo "</pre>";
?>

I had CLIENT_ID, SERVICE_ACCOUNT_NAME and KEY_FILE correctly installed. When I run the code I get the following error messages:

Fatal error:  Uncaught exception 'Google_Service_Exception' with message 'Error calling GET https://www.googleapis.com/drive/v2/apps: (403) Insufficient Permission' in C:\xampp\htdocs\oauth\Google\Http\REST.php:79
Stack trace:
#0 C:\xampp\htdocs\oauth\Google\Http\REST.php(44): Google_Http_REST::decodeHttpResponse(Object(Google_Http_Request))
#1 C:\xampp\htdocs\oauth\Google\Client.php(499): Google_Http_REST::execute(Object(Google_Client), Object(Google_Http_Request))
#2 C:\xampp\htdocs\oauth\Google\Service\Resource.php(195): Google_Client->execute(Object(Google_Http_Request))
#3 C:\xampp\htdocs\oauth\Google\Service\Drive.php(1281): Google_Service_Resource->call('list', Array, 'Google_Service_...')
#4 C:\xampp\htdocs\oauth\drive_client.php(41): Google_Service_Drive_Apps_Resource->listApps()
#5 {main}
  thrown in C:\xampp\htdocs\oauth\Google\Http\REST.php on line 79

What may be wrong with the code?

Answer 1

The apps#list method requires authorization with the scope https://www.googleapis.com/auth/drive.apps.readonly. Just add it to the array of scopes:

$client->setAssertionCredentials(new Google_Auth_AssertionCredentials(
  SERVICE_ACCOUNT_NAME,
  array('https://www.googleapis.com/auth/drive', 'https://www.googleapis.com/auth/drive.apps.readonly'),
  $key)
);

Answer 2

You must even disable Google drive api for your project in Developer Console under Apis & auth