Skip to content

Get a token for an external account

Source: R/credentials_external_account.R
credentials_external_account.Rd

[Experimental] Workload identity federation is a new (as of April 2021) keyless authentication mechanism that allows applications running on a non-Google Cloud platform, such as AWS, to access Google Cloud resources without using a conventional service account token. This eliminates the dilemma of how to safely manage service account credential files.

Unlike service accounts, the configuration file for workload identity federation contains no secrets. Instead, it holds non-sensitive metadata. The external application obtains the needed sensitive data "on-the-fly" from the running instance. The combined data is then used to obtain a so-called subject token from the external identity provider, such as AWS. This is then sent to Google's Security Token Service API, in exchange for a very short-lived federated access token. Finally, the federated access token is sent to Google's Service Account Credentials API, in exchange for a short-lived GCP access token. This access token allows the external application to impersonate a service account and inherit the permissions of the service account to access GCP resources.

This feature is still experimental in gargle and currently only supports AWS. It also requires installation of the suggested packages aws.signature and aws.ec2metadata. Workload identity federation can be used with other platforms, such as Microsoft Azure or any identity provider that supports OpenID Connect. If you would like gargle to support this token flow for additional platforms, please open an issue on GitHub and describe your use case.

Usage

credentials_external_account(
  scopes = "https://www.googleapis.com/auth/cloud-platform",
  path = "",
  ...
)

Arguments

scopes

A character vector of scopes to request. Pick from those listed at https://developers.google.com/identity/protocols/oauth2/scopes.

For certain token flows, the "https://www.googleapis.com/auth/userinfo.email" scope is unconditionally included. This grants permission to retrieve the email address associated with a token; gargle uses this to index cached OAuth tokens. This grants no permission to view or send email and is generally considered a low-value scope.

path

JSON containing the workload identity configuration for the external account, in one of the forms supported for the txt argument of jsonlite::fromJSON() (probably, a file path, although it could be a JSON string). The instructions for generating this configuration are given at Configuring workload identity federation.

Note that external account tokens are a natural fit for use as Application Default Credentials, so consider storing the configuration file in one of the standard locations consulted for ADC, instead of providing path explicitly. See credentials_app_default() for more.

...

Additional arguments passed to all credential functions.

Value

A WifToken() or NULL.

See also

There is substantial setup necessary, both on the GCP and AWS side, to use this authentication method. These two links provide, respectively, a high-level overview and step-by-step instructions.

Other credential functions: credentials_app_default(), credentials_byo_oauth2(), credentials_gce(), credentials_service_account(), credentials_user_oauth2(), token_fetch()

Examples

if (FALSE) {
credentials_external_account()
}