authutil is https://github.com/luci/luci-go/blob/2137b3a9aced8586950358f4ca0f76b379a54ced/client/cmd/authutil/main.go
It is a tool to produce OAuth2 access token given service account keys or using interactive login through the browser. It also understands LUCI_CONTEXT[local_auth] protocol to grab tokens inside Swarming tasks.
It is useful from various scripts that want to make Oauth2-authenticated calls. We are going to make it generally available in PATH in LUCI-supported environments (Swarming, Buildbot and depot_tools).
Since 'authutil' name is very vague, we also going to rename it to 'luci-auth'.
Comment 1 by bugdroid1@chromium.org
, Feb 6 2018