When your application requests private user data, the request must be authorized by an authenticated user who has access to that data. This is called user-centric OAuth 2.0 flow. If your application doesn't need to access user data, then you should use a server-centric OAuth 2.0 flow based on a service account. For more information about these two OAuth flows and authentication in general, see Cloud Storage Authentication. This page describes the different type of credentials you can create and use with Cloud Storage for both user-centric flows and server-centric OAuth 2.0 flows.
Identifying your application
Any request your application sends to the Cloud Storage JSON API that requires authorization needs to identify your application to Google. There are two ways to identify your application: using an OAuth 2.0 token (which also authorizes the request) and/or using the application's API key. Here's how to determine which of those options to use:
- If the request requires authorization (such as a request for an individual's private data), then the application must provide an OAuth 2.0 token with the request. The application may also provide the API key, but it doesn't have to.
- If the request doesn't require authorization (such as a request for public data), then no identification is required; however, the application may still provide the API key, an OAuth 2.0 token, or both.
About authorization protocols
Authorizing requests with OAuth 2.0
Requests to the Cloud Storage JSON API for non-public user data must be authorized by an authenticated user.
The details of the authorization process, or "flow," for OAuth 2.0 vary somewhat depending on what kind of application you're writing. The following general process applies to all application types:
- When you create your application, you register it using the Google Cloud Console. Google then provides information you'll need later, such as a client ID and a client secret.
- Activate the Cloud Storage JSON API in the Google Cloud Console. (If the API isn't listed in the Cloud Console, then skip this step.)
- When your application needs access to user data, it asks Google for a particular scope of access.
- Google displays a consent screen to the user, asking them to authorize your application to request some of their data.
- If the user approves, then Google gives your application a short-lived access token.
- Your application requests user data, attaching the access token to the request.
- If Google determines that your request and the token are valid, it returns the requested data.
Some flows include additional steps, such as using refresh tokens to acquire new access tokens. For detailed information about flows for various types of applications, see Google's OAuth 2.0 documentation.
Here's the OAuth 2.0 scope information for the Cloud Storage JSON API:
||Read/write and ACL management access to Cloud Storage.|
||Read/write access to Cloud Storage.|
||Read-only access to Cloud Storage.|
To request access using OAuth 2.0, your application needs the scope information, as well as information that Google supplies when you register your application (such as the client ID and the client secret).
Acquiring and using an API key
To acquire an API key:
- Open the Credentials page in the Cloud Console.
This API supports two types of credentials.
Create whichever credentials are appropriate for your project:
OAuth 2.0: Whenever your application requests private user data, it must send an OAuth 2.0 token along with the request. Your application first sends a client ID and, possibly, a client secret to obtain a token. You can generate OAuth 2.0 credentials for web applications, service accounts, or installed applications.
For more information, see the OAuth 2.0 documentation.
API keys: The key identifies your project and provides API access, quota, and reports.
The API supports several types of restrictions on API keys. If the API key that you need doesn't already exist, then create an API key in the Console by clicking Create credentials > API key. You can restrict the key before using it in production by clicking Restrict key and selecting one of the Restrictions.
To keep your API keys secure, follow the best practices for securely using API keys.
After you have an API key, your application can append the query parameter
key=yourAPIKey to all request URLs.
The API key is safe for embedding in URLs; it doesn't need any encoding.
- Obtain and experiment with OAuth 2.0 tokens using the OAuth 2.0 Playground.
- Learn more about Cloud Storage authentication.