Connecting to Google Sheets

The adapter supports authentication schemes using user accounts, service accounts, GCP instance accounts, and API keys for authentication. Each of these types of accounts have different AuthSchemes, but all of them use the OAuth standard for authentication.

Access	AuthScheme	Notes
User Accounts	OAuth	Can use embedded credentials if access from a Desktop application. See Desktop Applications, below.
Service Accounts	OAuthJWT	Depends on whether the data will be JSON or PFX files. See Authenticating as a Service, below.
GCP Instance Acct	GCPInstanceAccount	For use on a GCP virtual machine.
API Key	Token	Also, set APIKey to True. To create an API key in the Google Cloud Console, click Create credentials > API Key. To restrict the key before using it in production, select Restrict and choose one of the available restrictions.

The following sections focus on authentication as a User, and authentication as a Service.

Authenticating as a User (OAuth)

The following subsections describe how to authenticate to Google Sheets from a User account (AuthScheme OAuth) via three common authentication flows:

• Desktop: a connection to a server on the user's local machine, frequently used for testing and prototyping. Authenticated via either embedded OAuth or custom OAuth.
• Web: access to data via a shared website. Authenticated via custom OAuth only.
• Headless Server: a dedicated computer that provides services to other computers and their users, which is configured to operate without a monitor and keyboard. Authenticated via embedded OAuth or custom OAuth.

For information about how to create a custom OAuth application, and why you might want to create one even for auth flows that have embedded OAuth credentials, see Creating a Custom OAuth Application. For a complete list of connection string properties available in Google Sheets, see Connection.

Desktop Applications

CData provides an embedded OAuth application that simplifies authentication at the desktop. You can also authenticate from the desktop via a custom OAuth application, which you configure and register at the Google Sheets console. For further information, see Creating a Custom OAuth Application.

Before you connect, set the following variables:

• InitiateOAuth: GETANDREFRESH. Used to automatically get and refresh the OAuthAccessToken.
• Custom OAuth applications only:
  • OAuthClientId: The client Id assigned when you registered your custom OAuth application.
  • OAuthClientSecret: The client secret assigned when you registered your custom OAuth application.
  • CallbackURL: The redirect URI defined when you registered your custom OAuth application.

When you connect, the adapter opens Google Sheets's OAuth endpoint in your default browser. Log in and grant permissions to the application.

After you grant permissions to the application, the adapter completes the OAuth process:

1. The adapter obtains an access token from Google Sheets and uses it to request data.
2. The OAuth values are saved in the path specified in OAuthSettingsLocation. These values persist across connections.

When the access token expires, the adapter refreshes it automatically.

Web Applications

Authenticating via the Web requires you to create and register a custom OAuth application with Google Sheets, as described in Creating a Custom OAuth Application. You can then use the adapter to get and manage the OAuth token values.

This section describes how to get the OAuth access token, how to have the driver refresh the OAuth access token automatically, and how to refresh the OAuth access token manually.

Get the OAuth access token:

1. Set the following connection properties to obtain the OAuthAccessToken:
   • OAuthClientId: The client Id in your application settings.
   • OAuthClientSecret: The client secret in your application settings.

2. Call stored procedures to complete the OAuth exchange:
   • Call the GetOAuthAuthorizationURL stored procedure. Set the AuthMode input to WEB and the CallbackURL to the Redirect URI you specified in your application settings. The stored procedure returns the URL to the OAuth endpoint.
   • Navigate to the URL that the stored procedure returned in Step 1. Log in and authorize the web application. You are redirected back to the callback URL.
   • Call the GetOAuthAccessToken stored procedure. Set the AuthMode input to WEB. Set the Verifier input to the code parameter in the query string of the redirect URI.

After you obtain the access and refresh tokens, you can connect to data and refresh the OAuth access token automatically.

Automatic refresh of the OAuth access token:

To have the adapter automatically refresh the OAuth access token, do the following:

1. The first time you connect to data, set the following connection parameters:
   • InitiateOAuth: REFRESH.
   • OAuthClientId: The client Id in your application settings.
   • OAuthClientSecret: The client secret in your application settings.
   • OAuthAccessToken: The access token returned by GetOAuthAccessToken.
   • OAuthSettingsLocation: The path where you want the adapter to save the OAuth values, which persist across connections.
2. On subsequent data connections, set the following:
   • InitiateOAuth
   • OAuthSettingsLocation

Manual refresh of the OAuth access token:

The only value needed to manually refresh the OAUth access token is the OAuth refresh token.

1. To manually refresh the OAuthAccessToken after the ExpiresIn period (returned by GetOAuthAccessToken) has elapsed, call the RefreshOAuthAccessToken stored procedure.
2. Set the following connection properties:
   • OAuthClientId: The Client Id in your application settings.
   • OAuthClientSecret: The Client Secret in your application settings.

3. Call RefreshOAuthAccessToken with OAuthRefreshToken set to the OAuth refresh token returned by GetOAuthAccessToken.
4. After the new tokens have been retrieved, set the OAuthAccessToken property to the value returned by RefreshOAuthAccessToken. This opens a new connection.

Store the OAuth refresh token so that you can use it to manually refresh the OAuth access token after it has expired.

Headless Machines

If you need to log in to a resource that resides on a headless machine, you must authenticate on another device that has an internet browser. You can do this in either of the following ways:

• Option 1: Obtain the OAuthVerifier value.
• Option 2: Install the adapter on a machine with an internet browser and transfer the OAuth authentication values after you authenticate through the usual browser-based flow.

After you execute either Option 1 or Option 2, configure the driver to automatically refresh the access token on the headless machine.

Option 1: Obtaining and Exchanging a Verifier Code

To obtain a verifier code, you must authenticate at the OAuth authorization URL. Do the following:

1. Authenticate from the machine with an internet browser, and obtain the OAuthVerifier connection property.

   If you are using the embedded OAuth application, call the GetOAuthAuthorizationURL stored procedure. Open the URL returned by the stored procedure in a browser.

   If you are using a custom OAuth application, set the following properties:

   • InitiateOAuth: OFF.
   • OAuthClientId: The client Id assigned when you registered your application.
   • OAuthClientSecret: The client secret assigned when you registered your application.

2. Call the GetOAuthAuthorizationURL stored procedure. The stored procedure returns the CallbackURL established when the custom OAuth application was registered. (See Creating a Custom OAuth Application.)

   Copy this URL and paste it into a new browser tab.

3. Log in and grant permissions to the adapter. The OAuth application redirects you the redirect URI, with a parameter called code appended. Note the value of this parameter; you will need it later, to configure the OAuthVerifier connection property.

4. Exchange the OAuth verifier code for OAuth refresh and access tokens. On the headless machine, set the following connection properties to obtain the OAuth authentication values:

   • InitiateOAuth: REFRESH.
   • OAuthVerifier: The noted verifier code (the value of the code parameter in the redirect URI).
   • OAuthSettingsLocation: persist the encrypted OAuth authentication values to the specified file.
   • Custom OAuth applications only:
     • OAuthClientId: The client Id in your custom OAuth application settings.
     • OAuthClientSecret: The client secret in the custom OAuth application settings.

5. Test the connection to generate the OAuth settings file.

6. After you re-set the following properties, you are ready to connect:

   • InitiateOAuth: REFRESH.
   • OAuthSettingsLocation: The file containing the encrypted OAuth authentication values. To enable the automatic refreshing of the access token, be sure that this file gives read and write permissions to the adapter.
   • Custom OAuth applications only:
     • OAuthClientId: The client Id assigned when you registered your application.
     • OAuthClientSecret: The client secret assigned when you registered your application.

Option 2: Transferring OAuth Settings

Prior to connecting on a headless machine, you must install and create a connection with the driver on a device that supports an internet browser. Set the connection properties as described above in "Desktop Applications".

After completing the instructions in "Desktop Applications", the resulting authentication values are encrypted and written to the path specified by OAuthSettingsLocation. The default filename is OAuthSettings.txt.

Test the connection to generate the OAuth settings file, then copy the OAuth settings file to your headless machine.

To connect to data via the headless machine, set the following connection properties:

• InitiateOAuth: REFRESH
• OAuthSettingsLocation: The path to the OAuth settings file you copied from the machine with the browser. To enable automatic refreshing of the access token, ensure that this file gives read and write permissions to the adapter.
• Custom OAuth applications only:
  • OAuthClientId: The client Id assigned when you registered your custom OAuth application.
  • OAuthClientSecret: The client secret assigned when you registered your custom OAuth application.

Authenticating as a Service (OAuthJWT)

Authenticating to Google Sheets from a Service account (AuthScheme OAuth) requires:

• The creation of a new service account (see Creating a Custom OAuth Application); and
• A copy of the accounts certificate.

You must also set the following properties, which are specific to the preferred medium:

JSON File Properties

• AuthScheme: OAuthJWT.
• InitiateOAuth: GETANDREFRESH.
• OAuthJWTCertType: GOOGLEJSON.
• OAuthJWTCert: The path to the Google-provided .json file.
• OAuthJWTSubject (optional): The email address of the user whose data you want to access. Only set this value if the service account is part of a GSuite domain and you want to enable delegation.

PFX File Properties

• AuthScheme: OAuthJWT.
• InitiateOAuth: GETANDREFRESH.
• OAuthJWTCertType: PFXFILE.
• OAuthJWTCert: The path to the Google-provided .pfx file.
• OAuthJWTIssuer: The email address of the service account. This address usually includes the domain iam.gserviceaccount.com.
• OAuthJWTCertPassword (optional): The .pfx file password. In most cases you must provide this since Google encrypts PFX certificates.
• OAuthJWTCertSubject (optional): Set this only if you are using a OAuthJWTCertType which stores multiple certificates. Should not be set for PFX certificates generated by Google.
• OAuthJWTSubject (optional): The email address of the user whose data you want to access. Only set this value if the service account is part of a GSuite domain and you want to enable delegation.