Is it possible to authenticate server to server with Google Calendar API? - oauth

So I read the following on the Authorizing Requests to the Google Calendar API page written by Google folks.
Your application must use OAuth 2.0 to authorize requests. No other authorization protocols are supported. If your application uses Google Sign-In, some aspects of authorization are handled for you.
My knowledge of OAuth 2.0 is limited so I'm not sure if that means that I cannot get a one-time auth token for a user?
I'm building an app that will need to CRUD events for a user in the background based on other stuff. So I can't have the user authenticate over and over again. Is there a way around here?
If not, is there an Google Calendar alternative that has a dependable API that I could use?

When the user authenticates your application you are given an Access token (good for one hour) and a refresh token. You should save the refresh token, when ever you need to access the users data you can take the refresh token and ask Google to give you a new access token. It is the access token which gives you access to there account.
I wrote a tutorial that tries to explain Oauth2 how to set it up and how it works. Google Developer console Oauth2

Related

Need help Implementing OpenID connect/ OAuth2 flow using React-native, Spring Rest Api and ADFS 4.0

I have really hard time trying to understand mostly how should I implement my authorization flow. I think I have the authentication flow mostly correctly implemented using the technologies I've listed in the title. Here's what I want to achieve:
Basically I have a mobile app built using React-Native and I have made a restful API for this mobile app to use. I am currently at the point that I have implemented authentication using ADFS 4.0. My mobile app directly uses the ADFS endpoints to authenticate the user and I am able to receive the id_token and access token correctly from there. But here comes the part that I have no clue what to do next. Before I used openID, I had my own authentication and just an OAuth2 flow in my Spring REST Api and everytime I made a request from the mobile app to the API, I provided the access token in the headers, and used it to verify from the authorization server that the user is indeed authenticated and also received some crucial information about the user to use in my API. But now since I use OpenID-Connect and ADFS 4.0 for the authentication, I have the cruicial information I need in my API in the id_token. The question is, what exactly should i send to my API now from the mobile app, the id_token, access token or both? Given the access token to the userinfo endpoint at the ADFS returns the subject of the owner of the token. Like is there any way I could receive the users info using the subject or what exactly should I do. I've tried to research this subject a lot, but I am still very confused..
Send the access token to the API in the Bearer header. In the API, validate the token and, if required, do user info lookup. A Spring example of mine here if it helps.
Happy to answer any follow on questions ..

Long lived access token for Google OAuth 2.0

I'm building an application that needs to have access to Google Drive and Google Sheets. I want the user to go to https://mydomain.appspot.com/authenticate to go through the Google login flow and authenticate themselves so that the backend receives access tokens for both Google Drive and Google Sheets.
After that I want the backend to be able to access Drive and Sheets without user interaction. For example, I would like a scheduled task to run every hour and retrieve some data from Drive and Sheets. I want the backend to use the token it received when the user authenticated themselves.
Is this possible? I really hope so. I have been looking here and I don't really find anything that can help me. https://developers.google.com/sheets/api/guides/authorizing
The backend is developed in Java and deployed on Google App Engine.
A long lived access token is actually called a refresh token. You will need to have your users authenticate your application then you will receive a refresh token. the refresh token can then be used to request a new access token from the Google authentication servers when ever you need.
Note: Do not get yourself side tracked with serviced accounts its not the same thing. You can run automated scripts using a refresh token gained from Oauth2, googles terminology is just a little confusing.
Check out the official google java client library it should handle most of it for you. Using OAuth 2.0 with the Google API Client Library for Java
You need to setup Offline Access as defined at:
https://developers.google.com/identity/protocols/OAuth2WebServer#offline
After a user grants offline access to the requested scopes, you can continue to use the API client to access Google APIs on the user's behalf when the user is offline. The client object will refresh the access token as needed.

3-legs in OAuth 2.0

I'm making a program uses Youtube API for testing purpose.
Because my program is an installed-application, I've found a picture pointing out how to implement authentication.
It's what I have:
Immediately, I'm confused. According to this figure, I don't know why Google Servers just returns Authorization code after User login and consent.
Why doesn't Google Servers return Token instantly?
You are Confused because, I guess, you have missed 3rd leg "User". Authorization code represents the User Consent.
Google server returns Authorization code when User grants the permission to your app to get his/her data from google server(resource server). if user denies the permission Google server wont generate the Authorization code and your app wont be able to get access token.
Another use of Authorization_code is to keep resource owners credentials secret. Authorization code is shared with client and client exchanged that code for access_token.
Find more Information about Oauth 2.0 in this article.

What does "offline" access in OAuth mean?

What exactly does the word "offline" mean with regard to the offline access granted by an OAuth server?
Does it mean that the resource server will return data about the user even when the user is logged out of the third-party application or when the user is logged out of the OAuth resource server such as Facebook or Google or Twitter?
Offline access is IMO a really bad name for it, and I think its a term only
Google uses its not in the RFC for OAuth as far as I remember.
What is Google offline access?
When you request offline access the Google Authentication server returns a
refresh token. Refresh tokens give your application the ability to
request data on behalf of the user when the user is not present and in front of
your application.
Example of an app needing offline access
Let's say I have a Super Awesome app that downloads your Google Analytics Data,
makes it into a nice PDF file and emails it to you every morning with your
stats. For this to work my application needs to have the ability to access
your Google Analytics data when you are not around, to give me permission to do
that. So Super Awesome app would request offline access and the
authentication server would return a refresh token. With that refresh token
Super awesome app can request a new access token whenever it wants and get your
Google Analytics data.
Example of an app not needing offline access
Let's try Less Awesome app that lets you upload files to Google Drive. Less
Awesome app doesn't need to access your Google drive account when you're not
around. It only needs to access it when you are online. So in theory it
wouldn't need offline access. But in practice it does, it still gets a refresh
token so that it won't have to ask you for permission again (this is where I
think the naming is incorrect).
Helpful quote from the OpenStack documentation:
If a refresh token is present in the authorization code exchange, then it
can be used to obtain new access tokens at any time. This is called
offline access, because the user does not have to be present at the browser
when the application obtains a new access token.
The truth about offline access
The thing is that in a lot of cases the authentication server will return the
refresh token to you no matter what: You don't have to actually ask for anything –
it gives it to you. Giving you the ability to access the users data when they
aren't around. Users don't know that you could access their data without them
being there. It's only the JavaScript library and I think the PHP library
that hide the refresh token from you, but it's there.
Example
By just posting (i.e. HTTP POST request):
https://accounts.google.com/o/oauth2/token?code={AuthCode}&
client_id={ClientId}.apps.googleusercontent.com&client_secret={ClientSecret}&
redirect_uri=urn:ietf:wg:oauth:2.0:oob&grant_type=authorization_code
Here is the response:
{
"access_token": "ya29.1.AADtN_VSBMC2Ga2lhxsTKjVQ_ROco8VbD6h01aj4PcKHLm6qvHbNtn-_BIzXMw",
"token_type": "Bearer",
"expires_in": 3600,
"refresh_token": "1/J-3zPA8XR1o_cXebV9sDKn_f5MTqaFhKFxH-3PUPiJ4"
}
I now have offline access to this users data, and I never told them that I
would have it. More details be found in this short article: Google 3 legged
OAuth2 flow.
Useful reading
Using OAuth 2.0 for Web Server Applications
Understanding Refresh Tokens
By design the access tokens returned by the OAuth flow expire after a period of time (1 hour for Google access tokens), as a safety mechanism. This means that any application that wants to work with a user's data needs the user to have recently gone through the OAuth flow, aka be online. Requesting offline access provides the application a refresh token it can use to generate new access tokens, allowing it to access user data long after the data has gone through the OAuth flow, aka when they are offline.
Getting offline access is needed when your application continues to run when the user isn't present. For instance, if there is some nightly batch process, or if your application responds to external events like push notifications. However if you only access user data while the user is actively using your application then there is no need for offline access. Just send the user through the OAuth flow every time you need n access token, and if they've previously granted access to your application the authorization page will instantly close, making the process nearly invisible to the user.
For Google APIs, you can request offline access by including the parameter access_type=offline in the authorization URL you present to your users. Offline access, and hence refresh tokens, is requested automatically when using the Installed Application flow.

Avoid first Google OAuth 2.0 authorization

I've made an app who use OAuth from Google to access to Google Sites API. It works perfectly, but I want less user action, especially the first time when you must accept google's permissions, get authorization token, to get access and refresh token.
I want to know if it's possible to avoid all this steps (for users, and do this behind the application), in the code with HTTP requests for example or google libs, and just have to inform a google account (mail/password) to get an access/refresh token.
Have you any tips or knowledge about this ?
Thanks by advance
As i was using google analytics api i made some research and the minimum process is:
user click authenticate link on your web page, then is redirected to external google webpage when is prompted securely for login and password. and nothing else.
This oauth refresh token you can automate then - read about this in google docs - there is some info about this. i made all by changing a little simple hello world analytics app from google code.
As i remember You had to know what class in php is, and changing oauth wrapper in simple apps. It can store and process refresh tokens automatically - user needs to enter login and password as i said but it can be stored in cookies, so made once.

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