Google Service Account Authentication PHP - php

Question

I am trying to authenticate a service account so that I can use the access token with the client JSON_API library.
I have viewed these articles:
https://code.google.com/p/google-api-php-client/source/browse/trunk/examples/prediction/serviceAccount.php
https://code.google.com/p/google-api-php-client/wiki/UsingTheLibrary
https://developers.google.com/storage/docs/authentication#service_accounts
https://developers.google.com/accounts/docs/OAuth2#scenarios
Here's my PHP Code
<?php
require_once 'google-api-php-client/src/Google_Client.php';
const CLIENT_ID = "";
const SERVICE_ACCOUNT_NAME = "";
const KEY_FILE = "super secret path of course ;)";
$client = new Google_Client();
// Loads the key into PKCS 12 format
$key = file_get_contents(KEY_FILE);
$client->setAssertionCredentials(new Google_AssertionCredentials(
SERVICE_ACCOUNT_NAME,
array('https://www.googleapis.com/auth/prediction'),
$key
)
);
$client->setClientId(CLIENT_ID);
$auth = $client->authenticate();
print $auth ? "Returned true" : "Returned false";
print "<br>";
print is_null($client->getAccessToken()) ? "It's null" : "Works";
?>
Here's my output:
Returned true
It's null

Answer 1

I finally figured out how to authenticate using the PHP API library after using a mixture of different resources.
Here's my authentication class for the google php api libray
<?php
require_once 'google-api-php-client/src/Google_Client.php';
require_once 'google-api-php-client/src/contrib/Google_StorageService.php';
class Model_Storage_Auth
{
const CLIENT_ID = "someuniquenumber.apps.googleusercontent.com";
const SERVICE_ACCOUNT_NAME = "myserviceaccountname#developer.gserviceaccount.com";
const KEY_FILE = "/supersecretpath/key.p12";
const ACCESS_TOKEN = 'access_token';
const APP_NAME = 'My App Name';
private $google_client;
function __construct()
{
$this->google_client = new Google_Client();
$this->google_client->setApplicationName(self::APP_NAME);
}
public function getToken()
{
if(!is_null($this->google_client->getAccessToken())){}
elseif(!is_null(Session::get(self::ACCESS_TOKEN, null)))
{
$this->google_client->setAccessToken(Session::get(self::ACCESS_TOKEN, null));
}
else
{
$scope = array();
$scope[] = 'https://www.googleapis.com/auth/devstorage.full_control';
$key = file_get_contents(self::KEY_FILE);
$this->google_client->setAssertionCredentials(new Google_AssertionCredentials(
self::SERVICE_ACCOUNT_NAME,
$scope,
$key)
);
$this->google_client->setClientId(self::CLIENT_ID);
Google_Client::$auth->refreshTokenWithAssertion();
$token = $this->google_client->getAccessToken();
Session::set(self::ACCESS_TOKEN, $token);
}
return $this->google_client->getAccessToken();
}
}

Answer 2

A couple things to check:
First, I assume that CLIENT_ID and SERVICE_ACCOUNT_NAME are being set to your actual client ID and service account name, not just empty strings, right?
Second, you're using the OAuth scope https://www.googleapis.com/auth/prediction but trying to use that to access GCS. You'll want to either use read-only, read-write, or full-control scope, which you can find here. For example, if you wanted read-write access, you'd use the scope https://www.googleapis.com/auth/devstorage.read_write.