oauth - Google API OAuth2, Service Account, "error" : "invalid_grant"

Question

I'm trying to use service account to sync calendars from Dynamics CRM software to Google. During this I faced lack of documentation on google API for .net, especially regarding authorization. Most of Google samples can't be even compiled because of outdated libraries and classes used.

So I found some example over interned and receive error. Could someone please look on my sample and tell what am I doing wrong?

Preparatory steps:

1. I created a project in my private Google account.
2. In project developer console, under APIS & AUTH -> Credentials, I generated Service Account. Then clicked on "Generate P12 key" and downloaded the .p12 file.
3. Under APIS & AUTH -> APIs, switched on "Calendar API"

Then created console app and managed to install OAuth and Calendar nuget packages. There are:

1. Google APIs Auth Client Library, Google.Apis.Auth 1.8.1
2. Google APIs Client Library, Google.Apis 1.8.1
3. Google APIs Core Client Library, Id: Google.Apis.Core 1.8.1
4. Google.APIs.Calendar.v3 Client Library, Google.Apis.Calendar.V3 1.8.1.860

There is a code found and adapted to my needs:

using System;
using System.Security.Cryptography.X509Certificates;
using Google.Apis.Calendar.v3;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;

namespace CrmToGoogleCalendar
{
    class Program
    {

        static void Connect()
        {
            var certificate = new X509Certificate2("My Project-ee7facaa2bb1.p12", "notasecret", X509KeyStorageFlags.Exportable);


            var serviceAccountEmail = "506310960175-q2k8hjl141bml57ikufinsh6n8qiu93b@developer.gserviceaccount.com";
            var userAccountEmail = "<my email>@gmail.com";
            var credential = new ServiceAccountCredential(new ServiceAccountCredential.Initializer(serviceAccountEmail) 
                {
                    User = userAccountEmail,
                    Scopes = new[] { CalendarService.Scope.Calendar }
                }
                .FromCertificate(certificate));

            var service = new CalendarService(new BaseClientService.Initializer()
            {
                ApplicationName = "Test calendar sync app",
                HttpClientInitializer = credential

            });

            var calList = service.CalendarList.List().Execute().Items;


            foreach (var cal in calList)
            {
                Console.WriteLine(cal.Id);
            }
        }


        static void Main(string[] args)
        {
            Connect();
        }
    }
}

The communication with Google API which I see in the app and Fiddler is:

Request :

Host: HTTPS accounts.google.com, URL: /o/oauth2/token
Assertion: long binary string
grant_type: urn:ietf:params:oauth:grant-type:jwt-bearer

Response:

HTTP/1.1 400 Bad Request Content-Type: application/json Cache-Control: no-cache, no-store, max-age=0, must-revalidate Pragma: no-cache Expires: Fri, 01 Jan 1990 00:00:00 GMT Date: Thu, 24 Jul 2014 06:12:18 GMT X-Content-Type-Options: nosniff X-Frame-Options: SAMEORIGIN X-XSS-Protection: 1; mode=block Server: GSE Alternate-Protocol: 443:quic Transfer-Encoding: chunked

1f { "error" : "invalid_grant" } 0

Please help and thanks in advance!

Answer 1

After some investigations I found, that Google API does not work as expected with your personal account @gmail.com. You should have organization domain account in Google in format you@your_organisation_domain

Then, what is also pretty confusing, there is documentation at Google Drive API page, with "Delegate domain-wide authority to your service account" section not mentioned at Calendar API page. There are 7 steps in the section, are required to be done.

BTW with personal account administration site admin.google.com is even unavailable. So it's impossible to perform these 7 steps with @gmail.com account.

Then, when client is authorised in Google Apps Admin Console > Security > Advanced settings > Manage OAuth Client access the code starts to work.

There is a code that works for me:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography.X509Certificates;
using Google.Apis.Calendar.v3;
using Google.Apis.Calendar.v3.Data;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;

namespace CrmToGoogleCalendar
{
    class Program
    {

        static void Connect()
        {
            Console.WriteLine("Calendar via OAuth2 Service Account Sample");

            var certificate = new X509Certificate2("My MC Project-3f38defdf4e4.p12", "notasecret", X509KeyStorageFlags.Exportable);
            var serviceAccountEmail = "795039984093-c6ab1mknpediih2eo9cb70mc9jpu9h03@developer.gserviceaccount.com";
            var userAccountEmail = "me@testdomain.com"; 
            var credential = new ServiceAccountCredential(new ServiceAccountCredential.Initializer(serviceAccountEmail) 
                {
                    User = userAccountEmail,
                    Scopes = new[] { CalendarService.Scope.Calendar }
                }
                .FromCertificate(certificate));

            var service = new CalendarService(new BaseClientService.Initializer()
            {
                ApplicationName = "Test calendar sync app",
                HttpClientInitializer = credential

            });

            /* Get list of calendars */
            var calList = service.CalendarList.List().Execute().Items;
            var myCalendar = calList.First(@c => @c.Id == userAccountEmail);

            /* CREATE EVENT */
            var event1 = new Event()
                {
                    Kind = "calendar#event",
                    Summary = "Calendar event via API",
                    Description = "Programmatically created",
                    Status = "confirmed",
                    Organizer = new Event.OrganizerData() {
                        Email = userAccountEmail
                    },
                    Start = new EventDateTime()
                        {
                            DateTime = DateTime.Now.AddDays(1)
                        },
                    End = new EventDateTime()
                    {
                        DateTime = DateTime.Now.AddDays(1).AddHours(1)
                    },
                    ColorId = "6",
                    Reminders = new Event.RemindersData()
                        {
                            UseDefault = false,
                            Overrides = new List<EventReminder>(
                                new [] {
                                    new EventReminder()
                                        {
                                            Method = "popup",
                                            Minutes = 60
                                        }
                                })
                        }
                };

            event1 = service.Events.Insert(event1, myCalendar.Id).Execute();
            Console.WriteLine("Created event Id: {0}", event1.Id);


            /* ENLIST EVENTS */
            Console.WriteLine("calendar id={0}", myCalendar.Id);
            var events = service.Events.List(myCalendar.Id).Execute();
            foreach (var @event in events.Items)
            {
                Console.WriteLine("Event ID: {0}, ICalUID: {1}", @event.Id, @event.ICalUID);
                Console.WriteLine("  Name: {0}", @event.Summary);
                Console.WriteLine("  Description: {0}", @event.Description);
                Console.WriteLine("  Status: {0}", @event.Status);
                Console.WriteLine("  Color: {0}", @event.ColorId);
                Console.WriteLine("  Attendees: {0}", @event.Attendees == null ? "" : @event.Attendees.Select(a => a.Email).ToString());
                Console.WriteLine("  Kind: {0}", @event.Kind);
                Console.WriteLine("  Location: {0}", @event.Location);
                Console.WriteLine("  Organizer: {0}", @event.Organizer.Email);
                Console.WriteLine("  Recurrence: {0}", @event.Recurrence == null ? "no recurrence" : String.Join(",", @event.Recurrence));
                Console.WriteLine("  Start: {0}", @event.Start.DateTime == null ? @event.Start.Date : @event.Start.DateTime.ToString());
                Console.WriteLine("  End: {0}", @event.End.DateTime == null ? @event.End.Date : @event.End.DateTime.ToString());
                Console.WriteLine("  Reminders: {0}", @event.Reminders.UseDefault.Value ? "Default" : "Not defailt, " + 
                    (@event.Reminders.Overrides == null ? "no overrides" : String.Join(",", @event.Reminders.Overrides.Select(reminder => reminder.Method + ":" + reminder.Minutes)))
                    );
                Console.WriteLine("=====================");
            }

            Console.ReadKey();
        }


        static void Main(string[] args)
        {
            Connect();
        }
    }
}

The output produced looks so:

Calendar via OAuth2 Service Account Sample
Created event Id: jkits4dnpq6oflf99mfqf1kdo0
calendar id=me@testdomain.com
Event ID: 1logvocs77jierahutgv962sus, ICalUID: 1logvocs77jierahutgv962sus@google.com
  Name: test event
  Description: test description2
  Status: confirmed
  Color: 
  Attendees: 
  Kind: calendar#event
  Location: location2
  Organizer: me@testdomain.com
  Recurrence: RRULE:FREQ=WEEKLY;BYDAY=TH
  Start: 2014-07-31
  End: 2014-08-01
  Reminders: Not defailt, email:10,popup:10
=====================
Event ID: 1logvocs77jierahutgv962sus_20140814, ICalUID: 1logvocs77jierahutgv962sus@google.com
  Name: test event updated
  Description: test description2
  Status: confirmed
  Color: 
  Attendees: 
  Kind: calendar#event
  Location: location2
  Organizer: me@testdomain.com
  Recurrence: no recurrence
  Start: 2014-08-14
  End: 2014-08-15
  Reminders: Not defailt, email:10
=====================
Event ID: 974hqdhh8jhv5sdobkggmdvvd8, ICalUID: 974hqdhh8jhv5sdobkggmdvvd8@google.com
  Name: One hour event
  Description: test description
  Status: confirmed
  Color: 7
  Attendees: 
  Kind: calendar#event
  Location: Meeting Room Hire, Broadway, 255 The Bdwy, Broadway, NSW 2007, Australia
  Organizer: me@testdomain.com
  Recurrence: no recurrence
  Start: 1/08/2014 10:00:00 AM
  End: 1/08/2014 11:00:00 AM
  Reminders: Default
=====================
Event ID: jkits4dnpq6oflf99mfqf1kdo0, ICalUID: jkits4dnpq6oflf99mfqf1kdo0@google.com
  Name: Calendar event via API
  Description: Programmatically created
  Status: confirmed
  Color: 6
  Attendees: 
  Kind: calendar#event
  Location: 
  Organizer: me@testdomain.com
  Recurrence: no recurrence
  Start: 2/08/2014 12:30:50 PM
  End: 2/08/2014 1:30:50 PM
  Reminders: Not defailt, popup:60
=====================

First event is recurrent weekly whole day event series. Second is updated single event of the first (has the same UID). Third is single event for one hour. The last is created by code above.

Hope this will help others to economy their time.