Service Applications and Google Analytics API V3: Server-to-server OAuth2 authentication?

Question

I'm trying to make a server application to routinely pull Google Analytics data from my own GA account. Note, it is a personal, server-side application accessing my own data, i.e. there is no end-user accessing this application.

As such, I registered my application in the Google API Console as a Service Application, which gave me a Client ID and a Private Key. It is my understanding that Service Applications do NOT use Application Secret and Redirect URL as there is no end-user in this server-to-server authentication flow. Indeed, the Google API Console gave me no Secret and did not prompt me for a Redirect URL.

Unfortunately, I can not figure out how to authenticate my Service Application within Google's PHP Client API. There is extensive documentation on authenticating web applications with an end-user.

Google's documentation suggests it is possible to authenticate server-to-server by signing a JWT request with the private key. I just can't figure out how to do within the PHP client API (although I've browsed the source and there's definitely a script that signs a request with the private key.)

Am I missing something here? How can I perform authentication for a Service Application with my private key and the Google PHP client API?

Edited for clarity

Answer 1

UPDATE July 21st, 2012

Google Analytics API V3 now supports OAuth2 tokens returned by a .p12-signed JWT request. That is, we can now use the Analytics API w/ service accounts.

Currently pulling 4 years of day-by-day metrics, just for the hell of it.

Here's a quick 'n' dirty step-by-step:

1. Go to the Google API Console and create a new app

2. In the Services tab, flip the Google Analytics switch

3. In the API Access tab, click Create an OAuth2.0 Client ID

   • enter your name, upload a logo, and click Next

   • select the Service account option and press Create client ID

   • download your private key

4. Now you're back on the API Access page. You'll see a section called Service account with a Client ID and Email address

   • Copy the email address (something like ####@developer.gserviceaccount.com)

   • Visit your GA Admin and add this email as a user to your properties

   • This is a must; you'll get cryptic errors otherwise.

5. Get the latest Google PHP Client API via Github

   git submodule add https://github.com/google/google-api-php-client.git google-api-php-client-read-only
   

6. Rock 'n' roll (thanks all for tips on updated class names):

   // api dependencies
   require_once(PATH_TO_API . 'Google/Client.php');
   require_once(PATH_TO_API . 'Google/Service/Analytics.php');
   
   // create client object and set app name
   $client = new Google_Client();
   $client->setApplicationName(APP_NAME); // name of your app
   
   // set assertion credentials
   $client->setAssertionCredentials(
     new Google_Auth_AssertionCredentials(
   
       APP_EMAIL, // email you added to GA
   
       array('https://www.googleapis.com/auth/analytics.readonly'),
   
       file_get_contents(PATH_TO_PRIVATE_KEY_FILE)  // keyfile you downloaded
   
   ));
   
   // other settings
   $client->setClientId(CLIENT_ID);           // from API console
   $client->setAccessType('offline_access');  // this may be unnecessary?
   
   // create service and get data
   $service = new Google_Service_Analytics($client);
   $service->data_ga->get($ids, $startDate, $endDate, $metrics, $optParams);
   

 

_{original workaround below}

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It seems that, despite ambiguous documentation, most Google APIs do not support service accounts yet, including Google Analytics. They cannot digest OAuth2 tokens returned by a .p12 signed JWT request. So, as of right now, you cannot use Google Analytics API V3 with a service account.

Workaround:

1. In the Google API console, create a client application.

2. Follow the steps in the Google PHP Client API examples to generate a client_auth_url using your client_id, client_secret, and redirect_uri

3. Login to Google using cURL. (Be sure to use a cookie file!)

4. Open the client_auth_url in cURL and complete the form. Make sure you set curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 0); and curl_setopt($ch, CURLOPT_HEADER, 1); as the authorization_code will be in the Location: header of the response.

5. Using your client_id, client_secret, redirect_uri, and the activation code from Step 4, post a request to the Google's OAuth2 Token machine. Make sure you include grant_type = "authorization_code" in your post fields.

6. Hurray, you now have a refresh_token that never expires, and a working access_token! Post a request to the Google's OAuth2 Token machine with your client_id, client_secret, redirect_uri, and refresh_token when your access_token expires and you'll get a new one.