210 lines
6.6 KiB
Go
210 lines
6.6 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package google
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import (
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"context"
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"encoding/json"
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"errors"
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"fmt"
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"net/url"
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"strings"
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"time"
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"cloud.google.com/go/compute/metadata"
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"golang.org/x/oauth2"
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"golang.org/x/oauth2/jwt"
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)
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// Endpoint is Google's OAuth 2.0 endpoint.
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var Endpoint = oauth2.Endpoint{
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AuthURL: "https://accounts.google.com/o/oauth2/auth",
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TokenURL: "https://oauth2.googleapis.com/token",
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AuthStyle: oauth2.AuthStyleInParams,
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}
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// JWTTokenURL is Google's OAuth 2.0 token URL to use with the JWT flow.
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const JWTTokenURL = "https://oauth2.googleapis.com/token"
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// ConfigFromJSON uses a Google Developers Console client_credentials.json
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// file to construct a config.
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// client_credentials.json can be downloaded from
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// https://console.developers.google.com, under "Credentials". Download the Web
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// application credentials in the JSON format and provide the contents of the
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// file as jsonKey.
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func ConfigFromJSON(jsonKey []byte, scope ...string) (*oauth2.Config, error) {
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type cred struct {
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ClientID string `json:"client_id"`
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ClientSecret string `json:"client_secret"`
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RedirectURIs []string `json:"redirect_uris"`
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AuthURI string `json:"auth_uri"`
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TokenURI string `json:"token_uri"`
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}
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var j struct {
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Web *cred `json:"web"`
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Installed *cred `json:"installed"`
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}
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if err := json.Unmarshal(jsonKey, &j); err != nil {
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return nil, err
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}
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var c *cred
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switch {
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case j.Web != nil:
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c = j.Web
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case j.Installed != nil:
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c = j.Installed
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default:
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return nil, fmt.Errorf("oauth2/google: no credentials found")
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}
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if len(c.RedirectURIs) < 1 {
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return nil, errors.New("oauth2/google: missing redirect URL in the client_credentials.json")
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}
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return &oauth2.Config{
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ClientID: c.ClientID,
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ClientSecret: c.ClientSecret,
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RedirectURL: c.RedirectURIs[0],
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Scopes: scope,
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Endpoint: oauth2.Endpoint{
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AuthURL: c.AuthURI,
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TokenURL: c.TokenURI,
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},
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}, nil
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}
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// JWTConfigFromJSON uses a Google Developers service account JSON key file to read
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// the credentials that authorize and authenticate the requests.
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// Create a service account on "Credentials" for your project at
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// https://console.developers.google.com to download a JSON key file.
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func JWTConfigFromJSON(jsonKey []byte, scope ...string) (*jwt.Config, error) {
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var f credentialsFile
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if err := json.Unmarshal(jsonKey, &f); err != nil {
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return nil, err
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}
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if f.Type != serviceAccountKey {
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return nil, fmt.Errorf("google: read JWT from JSON credentials: 'type' field is %q (expected %q)", f.Type, serviceAccountKey)
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}
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scope = append([]string(nil), scope...) // copy
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return f.jwtConfig(scope), nil
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}
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// JSON key file types.
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const (
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serviceAccountKey = "service_account"
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userCredentialsKey = "authorized_user"
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)
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// credentialsFile is the unmarshalled representation of a credentials file.
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type credentialsFile struct {
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Type string `json:"type"` // serviceAccountKey or userCredentialsKey
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// Service Account fields
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ClientEmail string `json:"client_email"`
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PrivateKeyID string `json:"private_key_id"`
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PrivateKey string `json:"private_key"`
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TokenURL string `json:"token_uri"`
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ProjectID string `json:"project_id"`
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// User Credential fields
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// (These typically come from gcloud auth.)
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ClientSecret string `json:"client_secret"`
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ClientID string `json:"client_id"`
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RefreshToken string `json:"refresh_token"`
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}
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func (f *credentialsFile) jwtConfig(scopes []string) *jwt.Config {
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cfg := &jwt.Config{
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Email: f.ClientEmail,
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PrivateKey: []byte(f.PrivateKey),
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PrivateKeyID: f.PrivateKeyID,
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Scopes: scopes,
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TokenURL: f.TokenURL,
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}
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if cfg.TokenURL == "" {
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cfg.TokenURL = JWTTokenURL
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}
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return cfg
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}
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func (f *credentialsFile) tokenSource(ctx context.Context, scopes []string) (oauth2.TokenSource, error) {
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switch f.Type {
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case serviceAccountKey:
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cfg := f.jwtConfig(scopes)
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return cfg.TokenSource(ctx), nil
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case userCredentialsKey:
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cfg := &oauth2.Config{
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ClientID: f.ClientID,
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ClientSecret: f.ClientSecret,
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Scopes: scopes,
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Endpoint: Endpoint,
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}
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tok := &oauth2.Token{RefreshToken: f.RefreshToken}
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return cfg.TokenSource(ctx, tok), nil
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case "":
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return nil, errors.New("missing 'type' field in credentials")
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default:
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return nil, fmt.Errorf("unknown credential type: %q", f.Type)
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}
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}
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// ComputeTokenSource returns a token source that fetches access tokens
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// from Google Compute Engine (GCE)'s metadata server. It's only valid to use
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// this token source if your program is running on a GCE instance.
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// If no account is specified, "default" is used.
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// If no scopes are specified, a set of default scopes are automatically granted.
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// Further information about retrieving access tokens from the GCE metadata
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// server can be found at https://cloud.google.com/compute/docs/authentication.
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func ComputeTokenSource(account string, scope ...string) oauth2.TokenSource {
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return oauth2.ReuseTokenSource(nil, computeSource{account: account, scopes: scope})
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}
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type computeSource struct {
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account string
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scopes []string
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}
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func (cs computeSource) Token() (*oauth2.Token, error) {
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if !metadata.OnGCE() {
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return nil, errors.New("oauth2/google: can't get a token from the metadata service; not running on GCE")
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}
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acct := cs.account
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if acct == "" {
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acct = "default"
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}
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tokenURI := "instance/service-accounts/" + acct + "/token"
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if len(cs.scopes) > 0 {
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v := url.Values{}
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v.Set("scopes", strings.Join(cs.scopes, ","))
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tokenURI = tokenURI + "?" + v.Encode()
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}
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tokenJSON, err := metadata.Get(tokenURI)
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if err != nil {
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return nil, err
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}
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var res struct {
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AccessToken string `json:"access_token"`
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ExpiresInSec int `json:"expires_in"`
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TokenType string `json:"token_type"`
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}
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err = json.NewDecoder(strings.NewReader(tokenJSON)).Decode(&res)
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if err != nil {
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return nil, fmt.Errorf("oauth2/google: invalid token JSON from metadata: %v", err)
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}
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if res.ExpiresInSec == 0 || res.AccessToken == "" {
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return nil, fmt.Errorf("oauth2/google: incomplete token received from metadata")
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}
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tok := &oauth2.Token{
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AccessToken: res.AccessToken,
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TokenType: res.TokenType,
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Expiry: time.Now().Add(time.Duration(res.ExpiresInSec) * time.Second),
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}
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// NOTE(cbro): add hidden metadata about where the token is from.
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// This is needed for detection by client libraries to know that credentials come from the metadata server.
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// This may be removed in a future version of this library.
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return tok.WithExtra(map[string]interface{}{
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"oauth2.google.tokenSource": "compute-metadata",
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"oauth2.google.serviceAccount": acct,
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}), nil
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}
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