Google API : Unattended reading of calendar. How to login?

Question

I thought this one was going to be a breeze. Hence I'm stuck at the very beginning :-(

I created a Google Calendar where users can add events using a 'shared' dedicated login. Then I need to write a PHP script on my server to read the events in a given time frame.

I thought the API key described here would be enough. But it's not.

 curl https://www.googleapis.com/calendar/v3/users/me/calendarList?key=mykey

says Login required.

So I read about OAuth2.0 and how I need user to authenticate. The problem is my script is not interactive (although hardcoding the login in the script is not a problem to me: The info is not life-critical). So I read about Service Accounts but it looks like it's for non-user info.

Question: How do I code my script to force a given login without involving a human?

Note: This SO question seemed promising but the answer is for API version 2.0, which seems obsoleted.

Answer 1

The first thing you need to do is obtain an access token. This will require a human. Assuming you're using the Google APIs PHP Client, it can be done with this script (run from the command line).

NOTE: The snippet below works with a Client ID for Installed Applications. Make sure you create a client ID of this type in the Google API Access console.

require_once '../../src/apiClient.php';
defined('STDIN') or define('STDIN', fopen('php://stdin', 'r'));

$client = new apiClient();
// Visit https://code.google.com/apis/console to create your client id and cient secret
$client->setClientId('INSERT_CLIENT_ID');
$client->setClientSecret('INSERT_CLIENT_SECRET');
$client->setRedirectUri('urn:ietf:wg:oauth:2.0:oob');
$client->setScopes(array(
    'https://www.googleapis.com/auth/calendar',
    'https://www.googleapis.com/auth/calendar.readonly',
));

$authUrl = $client->createAuthUrl();

print "Please visit:\n$authUrl\n\n";
print "Please enter the auth code:\n";
$authCode = trim(fgets(STDIN));

$_GET['code'] = $authCode;
$token = $client->authenticate();
var_dump($token);

This will give you a json encoded string containing your accessToken and refreshToken. The accessToken expires after 1 hour, but don't worry. The refreshToken will not expire (unless you uninstall the application), and can be used to obtain a new refreshToken. The client library takes care of this part.

Next, save the full json string token (not only the access_token property in a safe place and make sure it can't be read by others. Your app can then call $client->setAccessToken($token) where $token was looked up from the safe location (Again, $token is the full json-encoded string, not limited to its access_token property).

Now, you can make authenticated request to the Calendar APIs!

require_once '../../src/apiClient.php';
require_once '../../src/contrib/apiCalendarService.php';
session_start();

$client = new apiClient();
$client->setApplicationName("Google Calendar PHP Sample Application");
$cal = new apiCalendarService($client);

$client->setAccessToken($tokenFromSafePlace);

$calList = $cal->calendarList->listCalendarList();
print "<h1>Calendar List</h1><pre>" . print_r($calList, true) . "</pre>";

Answer 2

Using the latest version of the client library (for the v3 api?) to get the token you need:

require_once 'Google/Client.php';
defined('STDIN') or define('STDIN', fopen('php://stdin', 'r'));

$client = new Google_Client();
// Visit https://console.developers.google.com/ to create your application and client id for a native app.
$client->setClientId('YOUR_CLIENT_ID');
$client->setClientSecret('YOUR_CLIENT_SECRET');
$client->setRedirectUri('urn:ietf:wg:oauth:2.0:oob');
$client->setScopes(array(
    'https://www.googleapis.com/auth/calendar',
    'https://www.googleapis.com/auth/calendar.readonly',
));

$authUrl = $client->createAuthUrl();

print "Please visit:\n$authUrl\n\n";
print "Please enter the auth code:\n";
$authCode = trim(fgets(STDIN));

$_GET['code'] = $authCode;
$token = $client->authenticate($authCode);
var_dump($token);

To get the calendar list you then need the following code:

require_once 'Google/Client.php';
require_once 'Google/Service/Calendar.php';

$client = new Google_Client();
$client->setApplicationName("My Calendar example");
// token you got from the previous code
$client->setAccessToken($token);

$calendarService = new Google_Service_Calendar($client);
$calendarList = $calendarService->calendarList;

$calList = $calendarList->listCalendarList();
print "<h1>Calendar List</h1><pre>" . print_r($calList, true) . "</pre>";