Google has REST APIs for almost all of the services offered on Google Cloud. These APIs are technology neutral and can be consumed by programming languages that support REST API calls or HTTPS requests. These REST APIs use the OAuth 2.0 protocol for the authentication mechanism and authorization to use specified services in specified modes. To authenticate and access Google Cloud services via OAuth, an application needs to implement the following methods:

• Download the OAuth credentials for Google Cloud from the cloud console, using it in the application to authenticate.
• Get the access token by specifying the services to use and the permissions needed to use them in your application. These permissions must already be set for the credentials via cloud console or API with admin credentials.
• Use the access token in all the subsequent API calls by passing it in HTTP header for the API calls to access the services for which it was issued.
• The access token is valid for an hour and it must be refreshed if it expires or it is revoked by an admin.