oauth2: fix expiration time window check

Before CL 68017, the test verified that tokens expire exactly one day
after they are issued, within the time that Exchange() takes to execute.
A refactoring in the CL extended this time window to a whole day, making
the check much more lenient.

See: https://go-review.googlesource.com/c/oauth2/+/168017
Change-Id: I479db429f64b25a711624817c13f068b4675163e
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/630495
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Sean Liao <sean@liao.dev>
Auto-Submit: Sean Liao <sean@liao.dev>
Reviewed-by: Carlos Amedee <carlos@golang.org>

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2009 The Go Authors. All rights reserved.
+Copyright 2009 The Go Authors.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are
@@ -10,7 +10,7 @@ notice, this list of conditions and the following disclaimer.
 copyright notice, this list of conditions and the following disclaimer
 in the documentation and/or other materials provided with the
 distribution.
-   * Neither the name of Google Inc. nor the names of its
+   * Neither the name of Google LLC nor the names of its
 contributors may be used to endorse or promote products derived from
 this software without specific prior written permission.
 

README.md

@@ -5,15 +5,6 @@
 
 oauth2 package contains a client implementation for OAuth 2.0 spec.
 
-## Installation
-
-~~~~
-go get golang.org/x/oauth2
-~~~~
-
-Or you can manually git clone the repository to
-`$(go env GOPATH)/src/golang.org/x/oauth2`.
-
 See pkg.go.dev for further documentation and examples.
 
 * [pkg.go.dev/golang.org/x/oauth2](https://pkg.go.dev/golang.org/x/oauth2)
@@ -33,7 +24,11 @@ The main issue tracker for the oauth2 repository is located at
 https://github.com/golang/oauth2/issues.
 
 This repository uses Gerrit for code changes. To learn how to submit changes to
-this repository, see https://golang.org/doc/contribute.html. In particular:
+this repository, see https://go.dev/doc/contribute.
+
+The git repository is https://go.googlesource.com/oauth2.
+
+Note:
 
 * Excluding trivial changes, all contributions should be connected to an existing issue.
 * API changes must go through the [change proposal process](https://go.dev/s/proposal-process) before they can be accepted.

authhandler/authhandler.go

@@ -34,7 +34,7 @@ type PKCEParams struct {
 // and returns an auth code and state upon approval.
 type AuthorizationHandler func(authCodeURL string) (code string, state string, err error)
 
-// TokenSourceWithPKCE is an enhanced version of TokenSource with PKCE support.
+// TokenSourceWithPKCE is an enhanced version of [oauth2.TokenSource] with PKCE support.
 //
 // The pkce parameter supports PKCE flow, which uses code challenge and code verifier
 // to prevent CSRF attacks. A unique code challenge and code verifier should be generated
@@ -43,12 +43,12 @@ func TokenSourceWithPKCE(ctx context.Context, config *oauth2.Config, state strin
 	return oauth2.ReuseTokenSource(nil, authHandlerSource{config: config, ctx: ctx, authHandler: authHandler, state: state, pkce: pkce})
 }
 
-// TokenSource returns an oauth2.TokenSource that fetches access tokens
+// TokenSource returns an [oauth2.TokenSource] that fetches access tokens
 // using 3-legged-OAuth flow.
 //
-// The provided context.Context is used for oauth2 Exchange operation.
+// The provided [context.Context] is used for oauth2 Exchange operation.
 //
-// The provided oauth2.Config should be a full configuration containing AuthURL,
+// The provided [oauth2.Config] should be a full configuration containing AuthURL,
 // TokenURL, and Scope.
 //
 // An environment-specific AuthorizationHandler is used to obtain user consent.

clientcredentials/clientcredentials.go

@@ -37,7 +37,7 @@ type Config struct {
 	// URL. This is a constant specific to each server.
 	TokenURL string
 
-	// Scope specifies optional requested permissions.
+	// Scopes specifies optional requested permissions.
 	Scopes []string
 
 	// EndpointParams specifies additional parameters for requests to the token endpoint.
@@ -55,7 +55,7 @@ type Config struct {
 
 // Token uses client credentials to retrieve a token.
 //
-// The provided context optionally controls which HTTP client is used. See the oauth2.HTTPClient variable.
+// The provided context optionally controls which HTTP client is used. See the [oauth2.HTTPClient] variable.
 func (c *Config) Token(ctx context.Context) (*oauth2.Token, error) {
 	return c.TokenSource(ctx).Token()
 }
@@ -64,18 +64,18 @@ func (c *Config) Token(ctx context.Context) (*oauth2.Token, error) {
 // The token will auto-refresh as necessary.
 //
 // The provided context optionally controls which HTTP client
-// is returned. See the oauth2.HTTPClient variable.
+// is returned. See the [oauth2.HTTPClient] variable.
 //
-// The returned Client and its Transport should not be modified.
+// The returned [http.Client] and its Transport should not be modified.
 func (c *Config) Client(ctx context.Context) *http.Client {
 	return oauth2.NewClient(ctx, c.TokenSource(ctx))
 }
 
-// TokenSource returns a TokenSource that returns t until t expires,
+// TokenSource returns a [oauth2.TokenSource] that returns t until t expires,
 // automatically refreshing it as necessary using the provided context and the
 // client ID and client secret.
 //
-// Most users will use Config.Client instead.
+// Most users will use [Config.Client] instead.
 func (c *Config) TokenSource(ctx context.Context) oauth2.TokenSource {
 	source := &tokenSource{
 		ctx:  ctx,

clientcredentials/clientcredentials_test.go

@@ -7,7 +7,6 @@ package clientcredentials
 import (
 	"context"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -36,9 +35,9 @@ func TestTokenSourceGrantTypeOverride(t *testing.T) {
 	wantGrantType := "password"
 	var gotGrantType string
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
-			t.Errorf("ioutil.ReadAll(r.Body) == %v, %v, want _, <nil>", body, err)
+			t.Errorf("io.ReadAll(r.Body) == %v, %v, want _, <nil>", body, err)
 		}
 		if err := r.Body.Close(); err != nil {
 			t.Errorf("r.Body.Close() == %v, want <nil>", err)
@@ -81,7 +80,7 @@ func TestTokenRequest(t *testing.T) {
 		if got, want := r.Header.Get("Content-Type"), "application/x-www-form-urlencoded"; got != want {
 			t.Errorf("Content-Type header = %q; want %q", got, want)
 		}
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			r.Body.Close()
 		}
@@ -123,7 +122,7 @@ func TestTokenRefreshRequest(t *testing.T) {
 		if got, want := headerContentType, "application/x-www-form-urlencoded"; got != want {
 			t.Errorf("Content-Type = %q; want %q", got, want)
 		}
-		body, _ := ioutil.ReadAll(r.Body)
+		body, _ := io.ReadAll(r.Body)
 		const want = "audience=audience1&grant_type=client_credentials&scope=scope1+scope2"
 		if string(body) != want {
 			t.Errorf("Unexpected refresh token payload.\n got: %s\nwant: %s\n", body, want)

deviceauth_test.go

@@ -7,9 +7,6 @@ import (
 	"strings"
 	"testing"
 	"time"
-
-	"github.com/google/go-cmp/cmp"
-	"github.com/google/go-cmp/cmp/cmpopts"
 )
 
 func TestDeviceAuthResponseMarshalJson(t *testing.T) {
@@ -74,7 +71,16 @@ func TestDeviceAuthResponseUnmarshalJson(t *testing.T) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			if !cmp.Equal(got, tc.want, cmpopts.IgnoreUnexported(DeviceAuthResponse{}), cmpopts.EquateApproxTime(time.Second+time.Since(begin))) {
+			margin := time.Second + time.Since(begin)
+			timeDiff := got.Expiry.Sub(tc.want.Expiry)
+			if timeDiff < 0 {
+				timeDiff *= -1
+			}
+			if timeDiff > margin {
+				t.Errorf("expiry time difference too large, got=%v, want=%v margin=%v", got.Expiry, tc.want.Expiry, margin)
+			}
+			got.Expiry, tc.want.Expiry = time.Time{}, time.Time{}
+			if got != tc.want {
 				t.Errorf("want=%#v, got=%#v", tc.want, got)
 			}
 		})

endpoints/endpoints.go

@@ -6,7 +6,7 @@
 package endpoints
 
 import (
-	"strings"
+	"net/url"
 
 	"golang.org/x/oauth2"
 )
@@ -17,6 +17,30 @@ var Amazon = oauth2.Endpoint{
 	TokenURL: "https://api.amazon.com/auth/o2/token",
 }
 
+// Apple is the endpoint for "Sign in with Apple".
+//
+// Documentation: https://developer.apple.com/documentation/signinwithapplerestapi
+var Apple = oauth2.Endpoint{
+	AuthURL:  "https://appleid.apple.com/auth/authorize",
+	TokenURL: "https://appleid.apple.com/auth/token",
+}
+
+// Asana is the endpoint for Asana.
+//
+// Documentation: https://developers.asana.com/docs/oauth
+var Asana = oauth2.Endpoint{
+	AuthURL:  "https://app.asana.com/-/oauth_authorize",
+	TokenURL: "https://app.asana.com/-/oauth_token",
+}
+
+// Badgr is the endpoint for Canvas Badges.
+//
+// Documentation: https://community.canvaslms.com/t5/Canvas-Badges-Credentials/Developers-Build-an-app-that-integrates-with-the-Canvas-Badges/ta-p/528727
+var Badgr = oauth2.Endpoint{
+	AuthURL:  "https://badgr.com/auth/oauth2/authorize",
+	TokenURL: "https://api.badgr.io/o/token",
+}
+
 // Battlenet is the endpoint for Battlenet.
 var Battlenet = oauth2.Endpoint{
 	AuthURL:  "https://battle.net/oauth/authorize",
@@ -35,10 +59,44 @@ var Cern = oauth2.Endpoint{
 	TokenURL: "https://oauth.web.cern.ch/OAuth/Token",
 }
 
+// Coinbase is the endpoint for Coinbase.
+//
+// Documentation: https://docs.cdp.coinbase.com/coinbase-app/docs/coinbase-app-reference
+var Coinbase = oauth2.Endpoint{
+	AuthURL:  "https://login.coinbase.com/oauth2/auth",
+	TokenURL: "https://login.coinbase.com/oauth2/token",
+}
+
+// Discord is the endpoint for Discord.
+//
+// Documentation: https://discord.com/developers/docs/topics/oauth2#shared-resources-oauth2-urls
+var Discord = oauth2.Endpoint{
+	AuthURL:  "https://discord.com/oauth2/authorize",
+	TokenURL: "https://discord.com/api/oauth2/token",
+}
+
+// Dropbox is the endpoint for Dropbox.
+//
+// Documentation: https://developers.dropbox.com/oauth-guide
+var Dropbox = oauth2.Endpoint{
+	AuthURL:  "https://www.dropbox.com/oauth2/authorize",
+	TokenURL: "https://api.dropboxapi.com/oauth2/token",
+}
+
+// Endpoint is Ebay's OAuth 2.0 endpoint.
+//
+// Documentation: https://developer.ebay.com/api-docs/static/authorization_guide_landing.html
+var Endpoint = oauth2.Endpoint{
+	AuthURL:  "https://auth.ebay.com/oauth2/authorize",
+	TokenURL: "https://api.ebay.com/identity/v1/oauth2/token",
+}
+
 // Facebook is the endpoint for Facebook.
+//
+// Documentation: https://developers.facebook.com/docs/facebook-login/guides/advanced/manual-flow
 var Facebook = oauth2.Endpoint{
-	AuthURL:  "https://www.facebook.com/v3.2/dialog/oauth",
-	TokenURL: "https://graph.facebook.com/v3.2/oauth/access_token",
+	AuthURL:  "https://www.facebook.com/v22.0/dialog/oauth",
+	TokenURL: "https://graph.facebook.com/v22.0/oauth/access_token",
 }
 
 // Foursquare is the endpoint for Foursquare.
@@ -62,14 +120,15 @@ var GitHub = oauth2.Endpoint{
 
 // GitLab is the endpoint for GitLab.
 var GitLab = oauth2.Endpoint{
-	AuthURL:  "https://gitlab.com/oauth/authorize",
-	TokenURL: "https://gitlab.com/oauth/token",
+	AuthURL:       "https://gitlab.com/oauth/authorize",
+	TokenURL:      "https://gitlab.com/oauth/token",
+	DeviceAuthURL: "https://gitlab.com/oauth/authorize_device",
 }
 
 // Google is the endpoint for Google.
 var Google = oauth2.Endpoint{
-	AuthURL:  "https://accounts.google.com/o/oauth2/auth",
-	TokenURL: "https://oauth2.googleapis.com/token",
+	AuthURL:       "https://accounts.google.com/o/oauth2/auth",
+	TokenURL:      "https://oauth2.googleapis.com/token",
 	DeviceAuthURL: "https://oauth2.googleapis.com/device/code",
 }
 
@@ -97,6 +156,14 @@ var KaKao = oauth2.Endpoint{
 	TokenURL: "https://kauth.kakao.com/oauth/token",
 }
 
+// Line is the endpoint for Line.
+//
+// Documentation: https://developers.line.biz/en/docs/line-login/integrate-line-login/
+var Line = oauth2.Endpoint{
+	AuthURL:  "https://access.line.me/oauth2/v2.1/authorize",
+	TokenURL: "https://api.line.me/oauth2/v2.1/token",
+}
+
 // LinkedIn is the endpoint for LinkedIn.
 var LinkedIn = oauth2.Endpoint{
 	AuthURL:  "https://www.linkedin.com/oauth/v2/authorization",
@@ -133,7 +200,17 @@ var Microsoft = oauth2.Endpoint{
 	TokenURL: "https://login.live.com/oauth20_token.srf",
 }
 
+// Naver is the endpoint for Naver.
+//
+// Documentation: https://developers.naver.com/docs/login/devguide/devguide.md
+var Naver = oauth2.Endpoint{
+	AuthURL:  "https://nid.naver.com/oauth2/authorize",
+	TokenURL: "https://nid.naver.com/oauth2/token",
+}
+
 // NokiaHealth is the endpoint for Nokia Health.
+//
+// Deprecated: Nokia Health is now Withings.
 var NokiaHealth = oauth2.Endpoint{
 	AuthURL:  "https://account.health.nokia.com/oauth2_user/authorize2",
 	TokenURL: "https://account.health.nokia.com/oauth2/token",
@@ -145,6 +222,20 @@ var Odnoklassniki = oauth2.Endpoint{
 	TokenURL: "https://api.odnoklassniki.ru/oauth/token.do",
 }
 
+// OpenStreetMap is the endpoint for OpenStreetMap.org.
+//
+// Documentation: https://wiki.openstreetmap.org/wiki/OAuth
+var OpenStreetMap = oauth2.Endpoint{
+	AuthURL:  "https://www.openstreetmap.org/oauth2/authorize",
+	TokenURL: "https://www.openstreetmap.org/oauth2/token",
+}
+
+// Patreon is the endpoint for Patreon.
+var Patreon = oauth2.Endpoint{
+	AuthURL:  "https://www.patreon.com/oauth2/authorize",
+	TokenURL: "https://www.patreon.com/api/oauth2/token",
+}
+
 // PayPal is the endpoint for PayPal.
 var PayPal = oauth2.Endpoint{
 	AuthURL:  "https://www.paypal.com/webapps/auth/protocol/openidconnect/v1/authorize",
@@ -157,10 +248,52 @@ var PayPalSandbox = oauth2.Endpoint{
 	TokenURL: "https://api.sandbox.paypal.com/v1/identity/openidconnect/tokenservice",
 }
 
+// Pinterest is the endpoint for Pinterest.
+//
+// Documentation: https://developers.pinterest.com/docs/getting-started/set-up-authentication-and-authorization/
+var Pinterest = oauth2.Endpoint{
+	AuthURL:  "https://www.pinterest.com/oauth",
+	TokenURL: "https://api.pinterest.com/v5/oauth/token",
+}
+
+// Pipedrive is the endpoint for Pipedrive.
+//
+// Documentation: https://developers.pipedrive.com/docs/api/v1/Oauth
+var Pipedrive = oauth2.Endpoint{
+	AuthURL:  "https://oauth.pipedrive.com/oauth/authorize",
+	TokenURL: "https://oauth.pipedrive.com/oauth/token",
+}
+
+// QQ is the endpoint for QQ.
+//
+// Documentation: https://wiki.connect.qq.com/%e5%bc%80%e5%8f%91%e6%94%bb%e7%95%a5_server-side
+var QQ = oauth2.Endpoint{
+	AuthURL:  "https://graph.qq.com/oauth2.0/authorize",
+	TokenURL: "https://graph.qq.com/oauth2.0/token",
+}
+
+// Rakuten is the endpoint for Rakuten.
+//
+// Documentation: https://webservice.rakuten.co.jp/documentation
+var Rakuten = oauth2.Endpoint{
+	AuthURL:  "https://app.rakuten.co.jp/services/authorize",
+	TokenURL: "https://app.rakuten.co.jp/services/token",
+}
+
 // Slack is the endpoint for Slack.
+//
+// Documentation: https://api.slack.com/authentication/oauth-v2
 var Slack = oauth2.Endpoint{
-	AuthURL:  "https://slack.com/oauth/authorize",
-	TokenURL: "https://slack.com/api/oauth.access",
+	AuthURL:  "https://slack.com/oauth/v2/authorize",
+	TokenURL: "https://slack.com/api/oauth.v2.access",
+}
+
+// Splitwise is the endpoint for Splitwise.
+//
+// Documentation: https://dev.splitwise.com/
+var Splitwise = oauth2.Endpoint{
+	AuthURL:  "https://www.splitwise.com/oauth/authorize",
+	TokenURL: "https://www.splitwise.com/oauth/token",
 }
 
 // Spotify is the endpoint for Spotify.
@@ -199,6 +332,22 @@ var Vk = oauth2.Endpoint{
 	TokenURL: "https://oauth.vk.com/access_token",
 }
 
+// Withings is the endpoint for Withings.
+//
+// Documentation: https://account.withings.com/oauth2_user/authorize2
+var Withings = oauth2.Endpoint{
+	AuthURL:  "https://account.withings.com/oauth2_user/authorize2",
+	TokenURL: "https://account.withings.com/oauth2/token",
+}
+
+// X is the endpoint for X (Twitter).
+//
+// Documentation: https://docs.x.com/resources/fundamentals/authentication/oauth-2-0/user-access-token
+var X = oauth2.Endpoint{
+	AuthURL:  "https://x.com/i/oauth2/authorize",
+	TokenURL: "https://api.x.com/2/oauth2/token",
+}
+
 // Yahoo is the endpoint for Yahoo.
 var Yahoo = oauth2.Endpoint{
 	AuthURL:  "https://api.login.yahoo.com/oauth2/request_auth",
@@ -217,6 +366,20 @@ var Zoom = oauth2.Endpoint{
 	TokenURL: "https://zoom.us/oauth/token",
 }
 
+// Asgardeo returns a new oauth2.Endpoint for the given tenant.
+//
+// Documentation: https://wso2.com/asgardeo/docs/guides/authentication/oidc/discover-oidc-configs/
+func AsgardeoEndpoint(tenant string) oauth2.Endpoint {
+	u := url.URL{
+		Scheme: "https",
+		Host:   "api.asgardeo.io",
+	}
+	return oauth2.Endpoint{
+		AuthURL:  u.JoinPath("t", tenant, "/oauth2/authorize").String(),
+		TokenURL: u.JoinPath("t", tenant, "/oauth2/token").String(),
+	}
+}
+
 // AzureAD returns a new oauth2.Endpoint for the given tenant at Azure Active Directory.
 // If tenant is empty, it uses the tenant called `common`.
 //
@@ -226,18 +389,29 @@ func AzureAD(tenant string) oauth2.Endpoint {
 	if tenant == "" {
 		tenant = "common"
 	}
+	u := url.URL{
+		Scheme: "https",
+		Host:   "login.microsoftonline.com",
+	}
 	return oauth2.Endpoint{
-		AuthURL:  "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/authorize",
-		TokenURL: "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/token",
+		AuthURL:       u.JoinPath(tenant, "/oauth2/v2.0/authorize").String(),
+		TokenURL:      u.JoinPath(tenant, "/oauth2/v2.0/token").String(),
+		DeviceAuthURL: u.JoinPath(tenant, "/oauth2/v2.0/devicecode").String(),
 	}
 }
 
-// HipChatServer returns a new oauth2.Endpoint for a HipChat Server instance
-// running on the given domain or host.
-func HipChatServer(host string) oauth2.Endpoint {
+// AzureADB2CEndpoint returns a new oauth2.Endpoint for the given tenant and policy at Azure Active Directory B2C.
+// policy is the Azure B2C User flow name Example: `B2C_1_SignUpSignIn`.
+//
+// Documentation: https://docs.microsoft.com/en-us/azure/active-directory-b2c/tokens-overview#endpoints
+func AzureADB2CEndpoint(tenant string, policy string) oauth2.Endpoint {
+	u := url.URL{
+		Scheme: "https",
+		Host:   tenant + ".b2clogin.com",
+	}
 	return oauth2.Endpoint{
-		AuthURL:  "https://" + host + "/users/authorize",
-		TokenURL: "https://" + host + "/v2/oauth/token",
+		AuthURL:  u.JoinPath(tenant+".onmicrosoft.com", policy, "/oauth2/v2.0/authorize").String(),
+		TokenURL: u.JoinPath(tenant+".onmicrosoft.com", policy, "/oauth2/v2.0/token").String(),
 	}
 }
 
@@ -250,9 +424,42 @@ func HipChatServer(host string) oauth2.Endpoint {
 // https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-pools-assign-domain.html
 // https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-userpools-server-contract-reference.html
 func AWSCognito(domain string) oauth2.Endpoint {
-	domain = strings.TrimRight(domain, "/")
+	u, err := url.Parse(domain)
+	if err != nil || u.Scheme == "" || u.Host == "" {
+		panic("endpoints: invalid domain" + domain)
+	}
 	return oauth2.Endpoint{
-		AuthURL:  domain + "/oauth2/authorize",
-		TokenURL: domain + "/oauth2/token",
+		AuthURL:  u.JoinPath("/oauth2/authorize").String(),
+		TokenURL: u.JoinPath("/oauth2/token").String(),
+	}
+}
+
+// HipChatServer returns a new oauth2.Endpoint for a HipChat Server instance.
+// host should be a hostname, without any scheme prefix.
+//
+// Documentation: https://developer.atlassian.com/server/hipchat/hipchat-rest-api-access-tokens/
+func HipChatServer(host string) oauth2.Endpoint {
+	u := url.URL{
+		Scheme: "https",
+		Host:   host,
+	}
+	return oauth2.Endpoint{
+		AuthURL:  u.JoinPath("/users/authorize").String(),
+		TokenURL: u.JoinPath("/v2/oauth/token").String(),
+	}
+}
+
+// Shopify returns a new oauth2.Endpoint for the supplied shop domain name.
+// host should be a hostname, without any scheme prefix.
+//
+// Documentation: https://shopify.dev/docs/apps/auth/oauth
+func Shopify(host string) oauth2.Endpoint {
+	u := url.URL{
+		Scheme: "https",
+		Host:   host,
+	}
+	return oauth2.Endpoint{
+		AuthURL:  u.JoinPath("/admin/oauth/authorize").String(),
+		TokenURL: u.JoinPath("/admin/oauth/access_token").String(),
 	}
 }

gitlab/gitlab.go

@@ -6,11 +6,8 @@
 package gitlab // import "golang.org/x/oauth2/gitlab"
 
 import (
-	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/endpoints"
 )
 
 // Endpoint is GitLab's OAuth 2.0 endpoint.
-var Endpoint = oauth2.Endpoint{
-	AuthURL:  "https://gitlab.com/oauth/authorize",
-	TokenURL: "https://gitlab.com/oauth/token",
-}
+var Endpoint = endpoints.GitLab

go.mod

@@ -1,16 +1,5 @@
 module golang.org/x/oauth2
 
-go 1.18
+go 1.23.0
 
-require (
-	cloud.google.com/go/compute/metadata v0.2.3
-	github.com/google/go-cmp v0.5.9
-	google.golang.org/appengine v1.6.7
-)
-
-require (
-	cloud.google.com/go/compute v1.20.1 // indirect
-	github.com/golang/protobuf v1.5.3 // indirect
-	golang.org/x/net v0.19.0 // indirect
-	google.golang.org/protobuf v1.31.0 // indirect
-)
+require cloud.google.com/go/compute/metadata v0.3.0

go.sum

@@ -1,26 +1,2 @@
-cloud.google.com/go/compute v1.20.1 h1:6aKEtlUiwEpJzM001l0yFkpXmUVXaN8W+fbkb2AZNbg=
-cloud.google.com/go/compute v1.20.1/go.mod h1:4tCnrn48xsqlwSAiLf1HXMQk8CONslYbdiEZc9FEIbM=
-cloud.google.com/go/compute/metadata v0.2.3 h1:mg4jlk7mCAj6xXp9UJ4fjI9VUI5rubuGBW5aJ7UnBMY=
-cloud.google.com/go/compute/metadata v0.2.3/go.mod h1:VAV5nSsACxMJvgaAuX6Pk2AawlZn8kiOGuCv6gTkwuA=
-github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
-github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
-github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg=
-github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
-github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
-github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
-github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
-golang.org/x/net v0.19.0 h1:zTwKpTd2XuCqf8huc7Fo2iSy+4RHPd10s4KzeTnVr1c=
-golang.org/x/net v0.19.0/go.mod h1:CfAk/cbD4CthTvqiEl8NpboMuiuOYsAr/7NOjZJtv1U=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-google.golang.org/appengine v1.6.7 h1:FZR1q0exgwxzPzp/aF+VccGrSfxfPpkBqjIIEq3ru6c=
-google.golang.org/appengine v1.6.7/go.mod h1:8WjMMxjGQR8xUklV/ARdw2HLXBOI7O7uCIDZVag1xfc=
-google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
-google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
-google.golang.org/protobuf v1.31.0 h1:g0LDEJHgrBl9N9r17Ru3sqWhkIx2NB67okBHPwC7hs8=
-google.golang.org/protobuf v1.31.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
+cloud.google.com/go/compute/metadata v0.3.0 h1:Tz+eQXMEqDIKRsmY3cHTL6FVaynIjX2QxYC4trgAKZc=
+cloud.google.com/go/compute/metadata v0.3.0/go.mod h1:zFmK7XCadkQkj6TtorcaGlCW1hT1fIilQDwofLpJ20k=

google/appengine.go

@@ -6,16 +6,13 @@ package google
 
 import (
 	"context"
-	"time"
+	"log"
+	"sync"
 
 	"golang.org/x/oauth2"
 )
 
-// Set at init time by appengine_gen1.go. If nil, we're not on App Engine standard first generation (<= Go 1.9) or App Engine flexible.
-var appengineTokenFunc func(c context.Context, scopes ...string) (token string, expiry time.Time, err error)
-
-// Set at init time by appengine_gen1.go. If nil, we're not on App Engine standard first generation (<= Go 1.9) or App Engine flexible.
-var appengineAppIDFunc func(c context.Context) string
+var logOnce sync.Once // only spam about deprecation once
 
 // AppEngineTokenSource returns a token source that fetches tokens from either
 // the current application's service account or from the metadata server,
@@ -23,8 +20,10 @@ var appengineAppIDFunc func(c context.Context) string
 // details. If you are implementing a 3-legged OAuth 2.0 flow on App Engine that
 // involves user accounts, see oauth2.Config instead.
 //
-// First generation App Engine runtimes (<= Go 1.9):
-// AppEngineTokenSource returns a token source that fetches tokens issued to the
+// The current version of this library requires at least Go 1.17 to build,
+// so first generation App Engine runtimes (<= Go 1.9) are unsupported.
+// Previously, on first generation App Engine runtimes, AppEngineTokenSource
+// returned a token source that fetches tokens issued to the
 // current App Engine application's service account. The provided context must have
 // come from appengine.NewContext.
 //
@@ -34,5 +33,8 @@ var appengineAppIDFunc func(c context.Context) string
 // context and scopes are not used. Please use DefaultTokenSource (or ComputeTokenSource,
 // which DefaultTokenSource will use in this case) instead.
 func AppEngineTokenSource(ctx context.Context, scope ...string) oauth2.TokenSource {
-	return appEngineTokenSource(ctx, scope...)
+	logOnce.Do(func() {
+		log.Print("google: AppEngineTokenSource is deprecated on App Engine standard second generation runtimes (>= Go 1.11) and App Engine flexible. Please use DefaultTokenSource or ComputeTokenSource.")
+	})
+	return ComputeTokenSource("")
 }

google/appengine_gen1.go

@@ -1,77 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build appengine
-
-// This file applies to App Engine first generation runtimes (<= Go 1.9).
-
-package google
-
-import (
-	"context"
-	"sort"
-	"strings"
-	"sync"
-
-	"golang.org/x/oauth2"
-	"google.golang.org/appengine"
-)
-
-func init() {
-	appengineTokenFunc = appengine.AccessToken
-	appengineAppIDFunc = appengine.AppID
-}
-
-// See comment on AppEngineTokenSource in appengine.go.
-func appEngineTokenSource(ctx context.Context, scope ...string) oauth2.TokenSource {
-	scopes := append([]string{}, scope...)
-	sort.Strings(scopes)
-	return &gaeTokenSource{
-		ctx:    ctx,
-		scopes: scopes,
-		key:    strings.Join(scopes, " "),
-	}
-}
-
-// aeTokens helps the fetched tokens to be reused until their expiration.
-var (
-	aeTokensMu sync.Mutex
-	aeTokens   = make(map[string]*tokenLock) // key is space-separated scopes
-)
-
-type tokenLock struct {
-	mu sync.Mutex // guards t; held while fetching or updating t
-	t  *oauth2.Token
-}
-
-type gaeTokenSource struct {
-	ctx    context.Context
-	scopes []string
-	key    string // to aeTokens map; space-separated scopes
-}
-
-func (ts *gaeTokenSource) Token() (*oauth2.Token, error) {
-	aeTokensMu.Lock()
-	tok, ok := aeTokens[ts.key]
-	if !ok {
-		tok = &tokenLock{}
-		aeTokens[ts.key] = tok
-	}
-	aeTokensMu.Unlock()
-
-	tok.mu.Lock()
-	defer tok.mu.Unlock()
-	if tok.t.Valid() {
-		return tok.t, nil
-	}
-	access, exp, err := appengineTokenFunc(ts.ctx, ts.scopes...)
-	if err != nil {
-		return nil, err
-	}
-	tok.t = &oauth2.Token{
-		AccessToken: access,
-		Expiry:      exp,
-	}
-	return tok.t, nil
-}

google/appengine_gen2_flex.go

@@ -1,27 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !appengine
-
-// This file applies to App Engine second generation runtimes (>= Go 1.11) and App Engine flexible.
-
-package google
-
-import (
-	"context"
-	"log"
-	"sync"
-
-	"golang.org/x/oauth2"
-)
-
-var logOnce sync.Once // only spam about deprecation once
-
-// See comment on AppEngineTokenSource in appengine.go.
-func appEngineTokenSource(ctx context.Context, scope ...string) oauth2.TokenSource {
-	logOnce.Do(func() {
-		log.Print("google: AppEngineTokenSource is deprecated on App Engine standard second generation runtimes (>= Go 1.11) and App Engine flexible. Please use DefaultTokenSource or ComputeTokenSource.")
-	})
-	return ComputeTokenSource("")
-}

google/default.go

@@ -12,6 +12,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
+	"sync"
 	"time"
 
 	"cloud.google.com/go/compute/metadata"
@@ -21,7 +22,7 @@ import (
 
 const (
 	adcSetupURL           = "https://cloud.google.com/docs/authentication/external/set-up-adc"
-	universeDomainDefault = "googleapis.com"
+	defaultUniverseDomain = "googleapis.com"
 )
 
 // Credentials holds Google credentials, including "Application Default Credentials".
@@ -41,19 +42,65 @@ type Credentials struct {
 	// running on Google Cloud Platform.
 	JSON []byte
 
+	// UniverseDomainProvider returns the default service domain for a given
+	// Cloud universe. Optional.
+	//
+	// On GCE, UniverseDomainProvider should return the universe domain value
+	// from Google Compute Engine (GCE)'s metadata server. See also [The attached service
+	// account](https://cloud.google.com/docs/authentication/application-default-credentials#attached-sa).
+	// If the GCE metadata server returns a 404 error, the default universe
+	// domain value should be returned. If the GCE metadata server returns an
+	// error other than 404, the error should be returned.
+	UniverseDomainProvider func() (string, error)
+
+	udMu sync.Mutex // guards universeDomain
 	// universeDomain is the default service domain for a given Cloud universe.
 	universeDomain string
 }
 
 // UniverseDomain returns the default service domain for a given Cloud universe.
+//
 // The default value is "googleapis.com".
+//
+// Deprecated: Use instead (*Credentials).GetUniverseDomain(), which supports
+// obtaining the universe domain when authenticating via the GCE metadata server.
+// Unlike GetUniverseDomain, this method, UniverseDomain, will always return the
+// default value when authenticating via the GCE metadata server.
+// See also [The attached service account](https://cloud.google.com/docs/authentication/application-default-credentials#attached-sa).
 func (c *Credentials) UniverseDomain() string {
 	if c.universeDomain == "" {
-		return universeDomainDefault
+		return defaultUniverseDomain
 	}
 	return c.universeDomain
 }
 
+// GetUniverseDomain returns the default service domain for a given Cloud
+// universe. If present, UniverseDomainProvider will be invoked and its return
+// value will be cached.
+//
+// The default value is "googleapis.com".
+func (c *Credentials) GetUniverseDomain() (string, error) {
+	c.udMu.Lock()
+	defer c.udMu.Unlock()
+	if c.universeDomain == "" && c.UniverseDomainProvider != nil {
+		// On Google Compute Engine, an App Engine standard second generation
+		// runtime, or App Engine flexible, use an externally provided function
+		// to request the universe domain from the metadata server.
+		ud, err := c.UniverseDomainProvider()
+		if err != nil {
+			return "", err
+		}
+		c.universeDomain = ud
+	}
+	// If no UniverseDomainProvider (meaning not on Google Compute Engine), or
+	// in case of any (non-error) empty return value from
+	// UniverseDomainProvider, set the default universe domain.
+	if c.universeDomain == "" {
+		c.universeDomain = defaultUniverseDomain
+	}
+	return c.universeDomain, nil
+}
+
 // DefaultCredentials is the old name of Credentials.
 //
 // Deprecated: use Credentials instead.
@@ -91,6 +138,12 @@ type CredentialsParams struct {
 	// Note: This option is currently only respected when using credentials
 	// fetched from the GCE metadata server.
 	EarlyTokenRefresh time.Duration
+
+	// UniverseDomain is the default service domain for a given Cloud universe.
+	// Only supported in authentication flows that support universe domains.
+	// This value takes precedence over a universe domain explicitly specified
+	// in a credentials config file or by the GCE metadata server. Optional.
+	UniverseDomain string
 }
 
 func (params CredentialsParams) deepCopy() CredentialsParams {
@@ -135,9 +188,7 @@ func DefaultTokenSource(ctx context.Context, scope ...string) (oauth2.TokenSourc
 //  2. A JSON file in a location known to the gcloud command-line tool.
 //     On Windows, this is %APPDATA%/gcloud/application_default_credentials.json.
 //     On other systems, $HOME/.config/gcloud/application_default_credentials.json.
-//  3. On Google App Engine standard first generation runtimes (<= Go 1.9) it uses
-//     the appengine.AccessToken function.
-//  4. On Google Compute Engine, Google App Engine standard second generation runtimes
+//  3. On Google Compute Engine, Google App Engine standard second generation runtimes
 //     (>= Go 1.11), and Google App Engine flexible environment, it fetches
 //     credentials from the metadata server.
 func FindDefaultCredentialsWithParams(ctx context.Context, params CredentialsParams) (*Credentials, error) {
@@ -160,23 +211,27 @@ func FindDefaultCredentialsWithParams(ctx context.Context, params CredentialsPar
 		return CredentialsFromJSONWithParams(ctx, b, params)
 	}
 
-	// Third, if we're on a Google App Engine standard first generation runtime (<= Go 1.9)
-	// use those credentials. App Engine standard second generation runtimes (>= Go 1.11)
-	// and App Engine flexible use ComputeTokenSource and the metadata server.
-	if appengineTokenFunc != nil {
-		return &Credentials{
-			ProjectID:   appengineAppIDFunc(ctx),
-			TokenSource: AppEngineTokenSource(ctx, params.Scopes...),
-		}, nil
-	}
-
-	// Fourth, if we're on Google Compute Engine, an App Engine standard second generation runtime,
+	// Third, if we're on Google Compute Engine, an App Engine standard second generation runtime,
 	// or App Engine flexible, use the metadata server.
 	if metadata.OnGCE() {
 		id, _ := metadata.ProjectID()
+		universeDomainProvider := func() (string, error) {
+			universeDomain, err := metadata.Get("universe/universe_domain")
+			if err != nil {
+				if _, ok := err.(metadata.NotDefinedError); ok {
+					// http.StatusNotFound (404)
+					return defaultUniverseDomain, nil
+				} else {
+					return "", err
+				}
+			}
+			return universeDomain, nil
+		}
 		return &Credentials{
-			ProjectID:   id,
-			TokenSource: computeTokenSource("", params.EarlyTokenRefresh, params.Scopes...),
+			ProjectID:              id,
+			TokenSource:            computeTokenSource("", params.EarlyTokenRefresh, params.Scopes...),
+			UniverseDomainProvider: universeDomainProvider,
+			universeDomain:         params.UniverseDomain,
 		}, nil
 	}
 
@@ -196,6 +251,12 @@ func FindDefaultCredentials(ctx context.Context, scopes ...string) (*Credentials
 // a Google Developers service account key file, a gcloud user credentials file (a.k.a. refresh
 // token JSON), or the JSON configuration file for workload identity federation in non-Google cloud
 // platforms (see https://cloud.google.com/iam/docs/how-to#using-workload-identity-federation).
+//
+// Important: If you accept a credential configuration (credential JSON/File/Stream) from an
+// external source for authentication to Google Cloud Platform, you must validate it before
+// providing it to any Google API or library. Providing an unvalidated credential configuration to
+// Google APIs can compromise the security of your systems and data. For more information, refer to
+// [Validate credential configurations from external sources](https://cloud.google.com/docs/authentication/external/externally-sourced-credentials).
 func CredentialsFromJSONWithParams(ctx context.Context, jsonData []byte, params CredentialsParams) (*Credentials, error) {
 	// Make defensive copy of the slices in params.
 	params = params.deepCopy()
@@ -217,9 +278,12 @@ func CredentialsFromJSONWithParams(ctx context.Context, jsonData []byte, params
 	}
 
 	universeDomain := f.UniverseDomain
+	if params.UniverseDomain != "" {
+		universeDomain = params.UniverseDomain
+	}
 	// Authorized user credentials are only supported in the googleapis.com universe.
 	if f.Type == userCredentialsKey {
-		universeDomain = universeDomainDefault
+		universeDomain = defaultUniverseDomain
 	}
 
 	ts, err := f.tokenSource(ctx, params)
@@ -236,6 +300,12 @@ func CredentialsFromJSONWithParams(ctx context.Context, jsonData []byte, params
 }
 
 // CredentialsFromJSON invokes CredentialsFromJSONWithParams with the specified scopes.
+//
+// Important: If you accept a credential configuration (credential JSON/File/Stream) from an
+// external source for authentication to Google Cloud Platform, you must validate it before
+// providing it to any Google API or library. Providing an unvalidated credential configuration to
+// Google APIs can compromise the security of your systems and data. For more information, refer to
+// [Validate credential configurations from external sources](https://cloud.google.com/docs/authentication/external/externally-sourced-credentials).
 func CredentialsFromJSON(ctx context.Context, jsonData []byte, scopes ...string) (*Credentials, error) {
 	var params CredentialsParams
 	params.Scopes = scopes

google/default_test.go

@@ -6,7 +6,12 @@ package google
 
 import (
 	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
 	"testing"
+
+	"cloud.google.com/go/compute/metadata"
 )
 
 var saJSONJWT = []byte(`{
@@ -53,6 +58,10 @@ var userJSONUniverseDomain = []byte(`{
   "universe_domain": "example.com"
 }`)
 
+var universeDomain = "example.com"
+
+var universeDomain2 = "apis-tpclp.goog"
+
 func TestCredentialsFromJSONWithParams_SA(t *testing.T) {
 	ctx := context.Background()
 	scope := "https://www.googleapis.com/auth/cloud-platform"
@@ -70,6 +79,32 @@ func TestCredentialsFromJSONWithParams_SA(t *testing.T) {
 	if want := "googleapis.com"; creds.UniverseDomain() != want {
 		t.Fatalf("got %q, want %q", creds.UniverseDomain(), want)
 	}
+	if want := "googleapis.com"; creds.UniverseDomain() != want {
+		t.Fatalf("got %q, want %q", creds.UniverseDomain(), want)
+	}
+}
+
+func TestCredentialsFromJSONWithParams_SA_Params_UniverseDomain(t *testing.T) {
+	ctx := context.Background()
+	scope := "https://www.googleapis.com/auth/cloud-platform"
+	params := CredentialsParams{
+		Scopes:         []string{scope},
+		UniverseDomain: universeDomain2,
+	}
+	creds, err := CredentialsFromJSONWithParams(ctx, saJSONJWT, params)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if want := "fake_project"; creds.ProjectID != want {
+		t.Fatalf("got %q, want %q", creds.ProjectID, want)
+	}
+	if creds.UniverseDomain() != universeDomain2 {
+		t.Fatalf("got %q, want %q", creds.UniverseDomain(), universeDomain2)
+	}
+	if creds.UniverseDomain() != universeDomain2 {
+		t.Fatalf("got %q, want %q", creds.UniverseDomain(), universeDomain2)
+	}
 }
 
 func TestCredentialsFromJSONWithParams_SA_UniverseDomain(t *testing.T) {
@@ -86,8 +121,42 @@ func TestCredentialsFromJSONWithParams_SA_UniverseDomain(t *testing.T) {
 	if want := "fake_project"; creds.ProjectID != want {
 		t.Fatalf("got %q, want %q", creds.ProjectID, want)
 	}
-	if want := "example.com"; creds.UniverseDomain() != want {
-		t.Fatalf("got %q, want %q", creds.UniverseDomain(), want)
+	if creds.UniverseDomain() != universeDomain {
+		t.Fatalf("got %q, want %q", creds.UniverseDomain(), universeDomain)
+	}
+	got, err := creds.GetUniverseDomain()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != universeDomain {
+		t.Fatalf("got %q, want %q", got, universeDomain)
+	}
+}
+
+func TestCredentialsFromJSONWithParams_SA_UniverseDomain_Params_UniverseDomain(t *testing.T) {
+	ctx := context.Background()
+	scope := "https://www.googleapis.com/auth/cloud-platform"
+	params := CredentialsParams{
+		Scopes:         []string{scope},
+		UniverseDomain: universeDomain2,
+	}
+	creds, err := CredentialsFromJSONWithParams(ctx, saJSONJWTUniverseDomain, params)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if want := "fake_project"; creds.ProjectID != want {
+		t.Fatalf("got %q, want %q", creds.ProjectID, want)
+	}
+	if creds.UniverseDomain() != universeDomain2 {
+		t.Fatalf("got %q, want %q", creds.UniverseDomain(), universeDomain2)
+	}
+	got, err := creds.GetUniverseDomain()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != universeDomain2 {
+		t.Fatalf("got %q, want %q", got, universeDomain2)
 	}
 }
 
@@ -105,6 +174,37 @@ func TestCredentialsFromJSONWithParams_User(t *testing.T) {
 	if want := "googleapis.com"; creds.UniverseDomain() != want {
 		t.Fatalf("got %q, want %q", creds.UniverseDomain(), want)
 	}
+	got, err := creds.GetUniverseDomain()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := "googleapis.com"; got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
+}
+
+func TestCredentialsFromJSONWithParams_User_Params_UniverseDomain(t *testing.T) {
+	ctx := context.Background()
+	scope := "https://www.googleapis.com/auth/cloud-platform"
+	params := CredentialsParams{
+		Scopes:         []string{scope},
+		UniverseDomain: universeDomain2,
+	}
+	creds, err := CredentialsFromJSONWithParams(ctx, userJSON, params)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if want := "googleapis.com"; creds.UniverseDomain() != want {
+		t.Fatalf("got %q, want %q", creds.UniverseDomain(), want)
+	}
+	got, err := creds.GetUniverseDomain()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := "googleapis.com"; got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
 }
 
 func TestCredentialsFromJSONWithParams_User_UniverseDomain(t *testing.T) {
@@ -121,4 +221,92 @@ func TestCredentialsFromJSONWithParams_User_UniverseDomain(t *testing.T) {
 	if want := "googleapis.com"; creds.UniverseDomain() != want {
 		t.Fatalf("got %q, want %q", creds.UniverseDomain(), want)
 	}
+	got, err := creds.GetUniverseDomain()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := "googleapis.com"; got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
+}
+
+func TestCredentialsFromJSONWithParams_User_UniverseDomain_Params_UniverseDomain(t *testing.T) {
+	ctx := context.Background()
+	scope := "https://www.googleapis.com/auth/cloud-platform"
+	params := CredentialsParams{
+		Scopes:         []string{scope},
+		UniverseDomain: universeDomain2,
+	}
+	creds, err := CredentialsFromJSONWithParams(ctx, userJSONUniverseDomain, params)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if want := "googleapis.com"; creds.UniverseDomain() != want {
+		t.Fatalf("got %q, want %q", creds.UniverseDomain(), want)
+	}
+	got, err := creds.GetUniverseDomain()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := "googleapis.com"; got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
+}
+
+func TestComputeUniverseDomain(t *testing.T) {
+	universeDomainPath := "/computeMetadata/v1/universe/universe_domain"
+	universeDomainResponseBody := "example.com"
+	var requests int
+	s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requests++
+		if r.URL.Path != universeDomainPath {
+			t.Errorf("bad path, got %s, want %s", r.URL.Path, universeDomainPath)
+		}
+		if requests > 1 {
+			t.Errorf("too many requests, got %d, want 1", requests)
+		}
+		w.Write([]byte(universeDomainResponseBody))
+	}))
+	defer s.Close()
+	t.Setenv("GCE_METADATA_HOST", strings.TrimPrefix(s.URL, "http://"))
+
+	scope := "https://www.googleapis.com/auth/cloud-platform"
+	params := CredentialsParams{
+		Scopes: []string{scope},
+	}
+	universeDomainProvider := func() (string, error) {
+		universeDomain, err := metadata.Get("universe/universe_domain")
+		if err != nil {
+			return "", err
+		}
+		return universeDomain, nil
+	}
+	// Copied from FindDefaultCredentialsWithParams, metadata.OnGCE() = true block
+	creds := &Credentials{
+		ProjectID:              "fake_project",
+		TokenSource:            computeTokenSource("", params.EarlyTokenRefresh, params.Scopes...),
+		UniverseDomainProvider: universeDomainProvider,
+		universeDomain:         params.UniverseDomain, // empty
+	}
+	c := make(chan bool)
+	go func() {
+		got, err := creds.GetUniverseDomain() // First conflicting access.
+		if err != nil {
+			t.Error(err)
+		}
+		if want := universeDomainResponseBody; got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+		c <- true
+	}()
+	got, err := creds.GetUniverseDomain() // Second conflicting (and potentially uncached) access.
+	<-c
+	if err != nil {
+		t.Error(err)
+	}
+	if want := universeDomainResponseBody; got != want {
+		t.Errorf("got %q, want %q", got, want)
+	}
+
 }

google/doc.go

@@ -22,91 +22,9 @@
 // the other by JWTConfigFromJSON. The returned Config can be used to obtain a TokenSource or
 // create an http.Client.
 //
-// # Workload Identity Federation
+// # Workload and Workforce Identity Federation
 //
-// Using workload identity federation, your application can access Google Cloud
-// resources from Amazon Web Services (AWS), Microsoft Azure or any identity
-// provider that supports OpenID Connect (OIDC) or SAML 2.0.
-// Traditionally, applications running outside Google Cloud have used service
-// account keys to access Google Cloud resources. Using identity federation,
-// you can allow your workload to impersonate a service account.
-// This lets you access Google Cloud resources directly, eliminating the
-// maintenance and security burden associated with service account keys.
-//
-// Follow the detailed instructions on how to configure Workload Identity Federation
-// in various platforms:
-//
-//	Amazon Web Services (AWS): https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#aws
-//	Microsoft Azure: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#azure
-//	OIDC identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#oidc
-//	SAML 2.0 identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#saml
-//
-// For OIDC and SAML providers, the library can retrieve tokens in three ways:
-// from a local file location (file-sourced credentials), from a server
-// (URL-sourced credentials), or from a local executable (executable-sourced
-// credentials).
-// For file-sourced credentials, a background process needs to be continuously
-// refreshing the file location with a new OIDC/SAML token prior to expiration.
-// For tokens with one hour lifetimes, the token needs to be updated in the file
-// every hour. The token can be stored directly as plain text or in JSON format.
-// For URL-sourced credentials, a local server needs to host a GET endpoint to
-// return the OIDC/SAML token. The response can be in plain text or JSON.
-// Additional required request headers can also be specified.
-// For executable-sourced credentials, an application needs to be available to
-// output the OIDC/SAML token and other information in a JSON format.
-// For more information on how these work (and how to implement
-// executable-sourced credentials), please check out:
-// https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#create_a_credential_configuration
-//
-// Note that this library does not perform any validation on the token_url, token_info_url,
-// or service_account_impersonation_url fields of the credential configuration.
-// It is not recommended to use a credential configuration that you did not generate with
-// the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
-//
-// # Workforce Identity Federation
-//
-// Workforce identity federation lets you use an external identity provider (IdP) to
-// authenticate and authorize a workforce—a group of users, such as employees, partners,
-// and contractors—using IAM, so that the users can access Google Cloud services.
-// Workforce identity federation extends Google Cloud's identity capabilities to support
-// syncless, attribute-based single sign on.
-//
-// With workforce identity federation, your workforce can access Google Cloud resources
-// using an external identity provider (IdP) that supports OpenID Connect (OIDC) or
-// SAML 2.0 such as Azure Active Directory (Azure AD), Active Directory Federation
-// Services (AD FS), Okta, and others.
-//
-// Follow the detailed instructions on how to configure Workload Identity Federation
-// in various platforms:
-//
-//	Azure AD: https://cloud.google.com/iam/docs/workforce-sign-in-azure-ad
-//	Okta: https://cloud.google.com/iam/docs/workforce-sign-in-okta
-//	OIDC identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#oidc
-//	SAML 2.0 identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#saml
-//
-// For workforce identity federation, the library can retrieve tokens in three ways:
-// from a local file location (file-sourced credentials), from a server
-// (URL-sourced credentials), or from a local executable (executable-sourced
-// credentials).
-// For file-sourced credentials, a background process needs to be continuously
-// refreshing the file location with a new OIDC/SAML token prior to expiration.
-// For tokens with one hour lifetimes, the token needs to be updated in the file
-// every hour. The token can be stored directly as plain text or in JSON format.
-// For URL-sourced credentials, a local server needs to host a GET endpoint to
-// return the OIDC/SAML token. The response can be in plain text or JSON.
-// Additional required request headers can also be specified.
-// For executable-sourced credentials, an application needs to be available to
-// output the OIDC/SAML token and other information in a JSON format.
-// For more information on how these work (and how to implement
-// executable-sourced credentials), please check out:
-// https://cloud.google.com/iam/docs/workforce-obtaining-short-lived-credentials#generate_a_configuration_file_for_non-interactive_sign-in
-//
-// # Security considerations
-//
-// Note that this library does not perform any validation on the token_url, token_info_url,
-// or service_account_impersonation_url fields of the credential configuration.
-// It is not recommended to use a credential configuration that you did not generate with
-// the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
+// For information on how to use Workload and Workforce Identity Federation, see [golang.org/x/oauth2/google/externalaccount].
 //
 // # Credentials
 //

google/downscope/downscoping.go

@@ -39,16 +39,19 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/url"
+	"strings"
 	"time"
 
 	"golang.org/x/oauth2"
 )
 
-var (
-	identityBindingEndpoint = "https://sts.googleapis.com/v1/token"
+const (
+	universeDomainPlaceholder       = "UNIVERSE_DOMAIN"
+	identityBindingEndpointTemplate = "https://sts.UNIVERSE_DOMAIN/v1/token"
+	defaultUniverseDomain           = "googleapis.com"
 )
 
 type accessBoundary struct {
@@ -105,6 +108,18 @@ type DownscopingConfig struct {
 	// access (or set of accesses) that the new token has to a given resource.
 	// There can be a maximum of 10 AccessBoundaryRules.
 	Rules []AccessBoundaryRule
+	// UniverseDomain is the default service domain for a given Cloud universe.
+	// The default value is "googleapis.com". Optional.
+	UniverseDomain string
+}
+
+// identityBindingEndpoint returns the identity binding endpoint with the
+// configured universe domain.
+func (dc *DownscopingConfig) identityBindingEndpoint() string {
+	if dc.UniverseDomain == "" {
+		return strings.Replace(identityBindingEndpointTemplate, universeDomainPlaceholder, defaultUniverseDomain, 1)
+	}
+	return strings.Replace(identityBindingEndpointTemplate, universeDomainPlaceholder, dc.UniverseDomain, 1)
 }
 
 // A downscopingTokenSource is used to retrieve a downscoped token with restricted
@@ -114,6 +129,9 @@ type downscopingTokenSource struct {
 	ctx context.Context
 	// config holds the information necessary to generate a downscoped Token.
 	config DownscopingConfig
+	// identityBindingEndpoint is the identity binding endpoint with the
+	// configured universe domain.
+	identityBindingEndpoint string
 }
 
 // NewTokenSource returns a configured downscopingTokenSource.
@@ -135,7 +153,11 @@ func NewTokenSource(ctx context.Context, conf DownscopingConfig) (oauth2.TokenSo
 			return nil, fmt.Errorf("downscope: all rules must provide at least one permission: %+v", val)
 		}
 	}
-	return downscopingTokenSource{ctx: ctx, config: conf}, nil
+	return downscopingTokenSource{
+		ctx:                     ctx,
+		config:                  conf,
+		identityBindingEndpoint: conf.identityBindingEndpoint(),
+	}, nil
 }
 
 // Token() uses a downscopingTokenSource to generate an oauth2 Token.
@@ -171,12 +193,12 @@ func (dts downscopingTokenSource) Token() (*oauth2.Token, error) {
 	form.Add("options", string(b))
 
 	myClient := oauth2.NewClient(dts.ctx, nil)
-	resp, err := myClient.PostForm(identityBindingEndpoint, form)
+	resp, err := myClient.PostForm(dts.identityBindingEndpoint, form)
 	if err != nil {
 		return nil, fmt.Errorf("unable to generate POST Request %v", err)
 	}
 	defer resp.Body.Close()
-	respBody, err := ioutil.ReadAll(resp.Body)
+	respBody, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return nil, fmt.Errorf("downscope: unable to read response body: %v", err)
 	}

google/downscope/downscoping_test.go

@@ -6,7 +6,7 @@ package downscope
 
 import (
 	"context"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -27,7 +27,7 @@ func Test_DownscopedTokenSource(t *testing.T) {
 		if r.URL.String() != "/" {
 			t.Errorf("Unexpected request URL, %v is found", r.URL)
 		}
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Fatalf("Failed to read request body: %v", err)
 		}
@@ -38,18 +38,43 @@ func Test_DownscopedTokenSource(t *testing.T) {
 		w.Write([]byte(standardRespBody))
 
 	}))
-	new := []AccessBoundaryRule{
+	myTok := oauth2.Token{AccessToken: "Mellon"}
+	tmpSrc := oauth2.StaticTokenSource(&myTok)
+	rules := []AccessBoundaryRule{
 		{
 			AvailableResource:    "test1",
 			AvailablePermissions: []string{"Perm1", "Perm2"},
 		},
 	}
-	myTok := oauth2.Token{AccessToken: "Mellon"}
-	tmpSrc := oauth2.StaticTokenSource(&myTok)
-	dts := downscopingTokenSource{context.Background(), DownscopingConfig{tmpSrc, new}}
-	identityBindingEndpoint = ts.URL
+	dts := downscopingTokenSource{
+		ctx: context.Background(),
+		config: DownscopingConfig{
+			RootSource: tmpSrc,
+			Rules:      rules,
+		},
+		identityBindingEndpoint: ts.URL,
+	}
 	_, err := dts.Token()
 	if err != nil {
 		t.Fatalf("NewDownscopedTokenSource failed with error: %v", err)
 	}
 }
+
+func Test_DownscopingConfig(t *testing.T) {
+	tests := []struct {
+		universeDomain string
+		want           string
+	}{
+		{"", "https://sts.googleapis.com/v1/token"},
+		{"googleapis.com", "https://sts.googleapis.com/v1/token"},
+		{"example.com", "https://sts.example.com/v1/token"},
+	}
+	for _, tt := range tests {
+		c := DownscopingConfig{
+			UniverseDomain: tt.universeDomain,
+		}
+		if got := c.identityBindingEndpoint(); got != tt.want {
+			t.Errorf("got %q, want %q", got, tt.want)
+		}
+	}
+}

google/example_test.go

@@ -7,9 +7,9 @@ package google_test
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"net/http"
+	"os"
 
 	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
@@ -60,7 +60,7 @@ func ExampleJWTConfigFromJSON() {
 	// To create a service account client, click "Create new Client ID",
 	// select "Service Account", and click "Create Client ID". A JSON
 	// key file will then be downloaded to your computer.
-	data, err := ioutil.ReadFile("/path/to/your-project-key.json")
+	data, err := os.ReadFile("/path/to/your-project-key.json")
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -136,7 +136,7 @@ func ExampleComputeTokenSource() {
 
 func ExampleCredentialsFromJSON() {
 	ctx := context.Background()
-	data, err := ioutil.ReadFile("/path/to/key-file.json")
+	data, err := os.ReadFile("/path/to/key-file.json")
 	if err != nil {
 		log.Fatal(err)
 	}

google/externalaccount/aws.go

@@ -14,7 +14,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"net/url"
 	"os"
@@ -26,22 +25,28 @@ import (
 	"golang.org/x/oauth2"
 )
 
-type awsSecurityCredentials struct {
-	AccessKeyID     string `json:"AccessKeyID"`
+// AwsSecurityCredentials models AWS security credentials.
+type AwsSecurityCredentials struct {
+	// AccessKeyID is the AWS Access Key ID - Required.
+	AccessKeyID string `json:"AccessKeyID"`
+	// SecretAccessKey is the AWS Secret Access Key - Required.
 	SecretAccessKey string `json:"SecretAccessKey"`
-	SecurityToken   string `json:"Token"`
+	// SessionToken is the AWS Session token. This should be provided for temporary AWS security credentials - Optional.
+	SessionToken string `json:"Token"`
 }
 
 // awsRequestSigner is a utility class to sign http requests using a AWS V4 signature.
 type awsRequestSigner struct {
 	RegionName             string
-	AwsSecurityCredentials awsSecurityCredentials
+	AwsSecurityCredentials *AwsSecurityCredentials
 }
 
 // getenv aliases os.Getenv for testing
 var getenv = os.Getenv
 
 const (
+	defaultRegionalCredentialVerificationUrl = "https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15"
+
 	// AWS Signature Version 4 signing algorithm identifier.
 	awsAlgorithm = "AWS4-HMAC-SHA256"
 
@@ -164,7 +169,7 @@ func requestDataHash(req *http.Request) (string, error) {
 		}
 		defer requestBody.Close()
 
-		requestData, err = ioutil.ReadAll(io.LimitReader(requestBody, 1<<20))
+		requestData, err = io.ReadAll(io.LimitReader(requestBody, 1<<20))
 		if err != nil {
 			return "", err
 		}
@@ -197,8 +202,8 @@ func (rs *awsRequestSigner) SignRequest(req *http.Request) error {
 
 	signedRequest.Header.Add("host", requestHost(req))
 
-	if rs.AwsSecurityCredentials.SecurityToken != "" {
-		signedRequest.Header.Add(awsSecurityTokenHeader, rs.AwsSecurityCredentials.SecurityToken)
+	if rs.AwsSecurityCredentials.SessionToken != "" {
+		signedRequest.Header.Add(awsSecurityTokenHeader, rs.AwsSecurityCredentials.SessionToken)
 	}
 
 	if signedRequest.Header.Get("date") == "" {
@@ -251,16 +256,18 @@ func (rs *awsRequestSigner) generateAuthentication(req *http.Request, timestamp
 }
 
 type awsCredentialSource struct {
-	EnvironmentID               string
-	RegionURL                   string
-	RegionalCredVerificationURL string
-	CredVerificationURL         string
-	IMDSv2SessionTokenURL       string
-	TargetResource              string
-	requestSigner               *awsRequestSigner
-	region                      string
-	ctx                         context.Context
-	client                      *http.Client
+	environmentID                  string
+	regionURL                      string
+	regionalCredVerificationURL    string
+	credVerificationURL            string
+	imdsv2SessionTokenURL          string
+	targetResource                 string
+	requestSigner                  *awsRequestSigner
+	region                         string
+	ctx                            context.Context
+	client                         *http.Client
+	awsSecurityCredentialsSupplier AwsSecurityCredentialsSupplier
+	supplierOptions                SupplierOptions
 }
 
 type awsRequestHeader struct {
@@ -292,18 +299,25 @@ func canRetrieveSecurityCredentialFromEnvironment() bool {
 	return getenv(awsAccessKeyId) != "" && getenv(awsSecretAccessKey) != ""
 }
 
-func shouldUseMetadataServer() bool {
-	return !canRetrieveRegionFromEnvironment() || !canRetrieveSecurityCredentialFromEnvironment()
+func (cs awsCredentialSource) shouldUseMetadataServer() bool {
+	return cs.awsSecurityCredentialsSupplier == nil && (!canRetrieveRegionFromEnvironment() || !canRetrieveSecurityCredentialFromEnvironment())
 }
 
 func (cs awsCredentialSource) credentialSourceType() string {
+	if cs.awsSecurityCredentialsSupplier != nil {
+		return "programmatic"
+	}
 	return "aws"
 }
 
 func (cs awsCredentialSource) subjectToken() (string, error) {
+	// Set Defaults
+	if cs.regionalCredVerificationURL == "" {
+		cs.regionalCredVerificationURL = defaultRegionalCredentialVerificationUrl
+	}
 	if cs.requestSigner == nil {
 		headers := make(map[string]string)
-		if shouldUseMetadataServer() {
+		if cs.shouldUseMetadataServer() {
 			awsSessionToken, err := cs.getAWSSessionToken()
 			if err != nil {
 				return "", err
@@ -318,8 +332,8 @@ func (cs awsCredentialSource) subjectToken() (string, error) {
 		if err != nil {
 			return "", err
 		}
-
-		if cs.region, err = cs.getRegion(headers); err != nil {
+		cs.region, err = cs.getRegion(headers)
+		if err != nil {
 			return "", err
 		}
 
@@ -331,7 +345,7 @@ func (cs awsCredentialSource) subjectToken() (string, error) {
 
 	// Generate the signed request to AWS STS GetCallerIdentity API.
 	// Use the required regional endpoint. Otherwise, the request will fail.
-	req, err := http.NewRequest("POST", strings.Replace(cs.RegionalCredVerificationURL, "{region}", cs.region, 1), nil)
+	req, err := http.NewRequest("POST", strings.Replace(cs.regionalCredVerificationURL, "{region}", cs.region, 1), nil)
 	if err != nil {
 		return "", err
 	}
@@ -339,8 +353,8 @@ func (cs awsCredentialSource) subjectToken() (string, error) {
 	// provider, with or without the HTTPS prefix.
 	// Including this header as part of the signature is recommended to
 	// ensure data integrity.
-	if cs.TargetResource != "" {
-		req.Header.Add("x-goog-cloud-target-resource", cs.TargetResource)
+	if cs.targetResource != "" {
+		req.Header.Add("x-goog-cloud-target-resource", cs.targetResource)
 	}
 	cs.requestSigner.SignRequest(req)
 
@@ -387,11 +401,11 @@ func (cs awsCredentialSource) subjectToken() (string, error) {
 }
 
 func (cs *awsCredentialSource) getAWSSessionToken() (string, error) {
-	if cs.IMDSv2SessionTokenURL == "" {
+	if cs.imdsv2SessionTokenURL == "" {
 		return "", nil
 	}
 
-	req, err := http.NewRequest("PUT", cs.IMDSv2SessionTokenURL, nil)
+	req, err := http.NewRequest("PUT", cs.imdsv2SessionTokenURL, nil)
 	if err != nil {
 		return "", err
 	}
@@ -404,31 +418,35 @@ func (cs *awsCredentialSource) getAWSSessionToken() (string, error) {
 	}
 	defer resp.Body.Close()
 
-	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
 		return "", err
 	}
 
 	if resp.StatusCode != 200 {
-		return "", fmt.Errorf("oauth2/google: unable to retrieve AWS session token - %s", string(respBody))
+		return "", fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS session token - %s", string(respBody))
 	}
 
 	return string(respBody), nil
 }
 
 func (cs *awsCredentialSource) getRegion(headers map[string]string) (string, error) {
+	if cs.awsSecurityCredentialsSupplier != nil {
+		return cs.awsSecurityCredentialsSupplier.AwsRegion(cs.ctx, cs.supplierOptions)
+	}
 	if canRetrieveRegionFromEnvironment() {
 		if envAwsRegion := getenv(awsRegion); envAwsRegion != "" {
+			cs.region = envAwsRegion
 			return envAwsRegion, nil
 		}
 		return getenv("AWS_DEFAULT_REGION"), nil
 	}
 
-	if cs.RegionURL == "" {
-		return "", errors.New("oauth2/google: unable to determine AWS region")
+	if cs.regionURL == "" {
+		return "", errors.New("oauth2/google/externalaccount: unable to determine AWS region")
 	}
 
-	req, err := http.NewRequest("GET", cs.RegionURL, nil)
+	req, err := http.NewRequest("GET", cs.regionURL, nil)
 	if err != nil {
 		return "", err
 	}
@@ -443,13 +461,13 @@ func (cs *awsCredentialSource) getRegion(headers map[string]string) (string, err
 	}
 	defer resp.Body.Close()
 
-	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
 		return "", err
 	}
 
 	if resp.StatusCode != 200 {
-		return "", fmt.Errorf("oauth2/google: unable to retrieve AWS region - %s", string(respBody))
+		return "", fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS region - %s", string(respBody))
 	}
 
 	// This endpoint will return the region in format: us-east-2b.
@@ -461,12 +479,15 @@ func (cs *awsCredentialSource) getRegion(headers map[string]string) (string, err
 	return string(respBody[:respBodyEnd]), nil
 }
 
-func (cs *awsCredentialSource) getSecurityCredentials(headers map[string]string) (result awsSecurityCredentials, err error) {
+func (cs *awsCredentialSource) getSecurityCredentials(headers map[string]string) (result *AwsSecurityCredentials, err error) {
+	if cs.awsSecurityCredentialsSupplier != nil {
+		return cs.awsSecurityCredentialsSupplier.AwsSecurityCredentials(cs.ctx, cs.supplierOptions)
+	}
 	if canRetrieveSecurityCredentialFromEnvironment() {
-		return awsSecurityCredentials{
+		return &AwsSecurityCredentials{
 			AccessKeyID:     getenv(awsAccessKeyId),
 			SecretAccessKey: getenv(awsSecretAccessKey),
-			SecurityToken:   getenv(awsSessionToken),
+			SessionToken:    getenv(awsSessionToken),
 		}, nil
 	}
 
@@ -481,24 +502,23 @@ func (cs *awsCredentialSource) getSecurityCredentials(headers map[string]string)
 	}
 
 	if credentials.AccessKeyID == "" {
-		return result, errors.New("oauth2/google: missing AccessKeyId credential")
+		return result, errors.New("oauth2/google/externalaccount: missing AccessKeyId credential")
 	}
 
 	if credentials.SecretAccessKey == "" {
-		return result, errors.New("oauth2/google: missing SecretAccessKey credential")
+		return result, errors.New("oauth2/google/externalaccount: missing SecretAccessKey credential")
 	}
 
-	return credentials, nil
+	return &credentials, nil
 }
 
-func (cs *awsCredentialSource) getMetadataSecurityCredentials(roleName string, headers map[string]string) (awsSecurityCredentials, error) {
-	var result awsSecurityCredentials
+func (cs *awsCredentialSource) getMetadataSecurityCredentials(roleName string, headers map[string]string) (AwsSecurityCredentials, error) {
+	var result AwsSecurityCredentials
 
-	req, err := http.NewRequest("GET", fmt.Sprintf("%s/%s", cs.CredVerificationURL, roleName), nil)
+	req, err := http.NewRequest("GET", fmt.Sprintf("%s/%s", cs.credVerificationURL, roleName), nil)
 	if err != nil {
 		return result, err
 	}
-	req.Header.Add("Content-Type", "application/json")
 
 	for name, value := range headers {
 		req.Header.Add(name, value)
@@ -510,13 +530,13 @@ func (cs *awsCredentialSource) getMetadataSecurityCredentials(roleName string, h
 	}
 	defer resp.Body.Close()
 
-	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
 		return result, err
 	}
 
 	if resp.StatusCode != 200 {
-		return result, fmt.Errorf("oauth2/google: unable to retrieve AWS security credentials - %s", string(respBody))
+		return result, fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS security credentials - %s", string(respBody))
 	}
 
 	err = json.Unmarshal(respBody, &result)
@@ -524,11 +544,11 @@ func (cs *awsCredentialSource) getMetadataSecurityCredentials(roleName string, h
 }
 
 func (cs *awsCredentialSource) getMetadataRoleName(headers map[string]string) (string, error) {
-	if cs.CredVerificationURL == "" {
-		return "", errors.New("oauth2/google: unable to determine the AWS metadata server security credentials endpoint")
+	if cs.credVerificationURL == "" {
+		return "", errors.New("oauth2/google/externalaccount: unable to determine the AWS metadata server security credentials endpoint")
 	}
 
-	req, err := http.NewRequest("GET", cs.CredVerificationURL, nil)
+	req, err := http.NewRequest("GET", cs.credVerificationURL, nil)
 	if err != nil {
 		return "", err
 	}
@@ -543,13 +563,13 @@ func (cs *awsCredentialSource) getMetadataRoleName(headers map[string]string) (s
 	}
 	defer resp.Body.Close()
 
-	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
 		return "", err
 	}
 
 	if resp.StatusCode != 200 {
-		return "", fmt.Errorf("oauth2/google: unable to retrieve AWS role name - %s", string(respBody))
+		return "", fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS role name - %s", string(respBody))
 	}
 
 	return string(respBody), nil

google/externalaccount/aws_test.go

@@ -7,6 +7,7 @@ package externalaccount
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
@@ -36,7 +37,7 @@ func setEnvironment(env map[string]string) func(string) string {
 
 var defaultRequestSigner = &awsRequestSigner{
 	RegionName: "us-east-1",
-	AwsSecurityCredentials: awsSecurityCredentials{
+	AwsSecurityCredentials: &AwsSecurityCredentials{
 		AccessKeyID:     "AKIDEXAMPLE",
 		SecretAccessKey: "wJalrXUtnFEMI/K7MDENG+bPxRfiCYEXAMPLEKEY",
 	},
@@ -50,10 +51,10 @@ const (
 
 var requestSignerWithToken = &awsRequestSigner{
 	RegionName: "us-east-2",
-	AwsSecurityCredentials: awsSecurityCredentials{
+	AwsSecurityCredentials: &AwsSecurityCredentials{
 		AccessKeyID:     accessKeyID,
 		SecretAccessKey: secretAccessKey,
-		SecurityToken:   securityToken,
+		SessionToken:    securityToken,
 	},
 }
 
@@ -388,7 +389,7 @@ func TestAWSv4Signature_PostRequestWithSecurityTokenAndAdditionalHeaders(t *test
 func TestAWSv4Signature_PostRequestWithAmzDateButNoSecurityToken(t *testing.T) {
 	var requestSigner = &awsRequestSigner{
 		RegionName: "us-east-2",
-		AwsSecurityCredentials: awsSecurityCredentials{
+		AwsSecurityCredentials: &AwsSecurityCredentials{
 			AccessKeyID:     accessKeyID,
 			SecretAccessKey: secretAccessKey,
 		},
@@ -526,8 +527,8 @@ func notFound(w http.ResponseWriter, r *http.Request) {
 
 func noHeaderValidation(r *http.Request) {}
 
-func (server *testAwsServer) getCredentialSource(url string) CredentialSource {
-	return CredentialSource{
+func (server *testAwsServer) getCredentialSource(url string) *CredentialSource {
+	return &CredentialSource{
 		EnvironmentID:               "aws1",
 		URL:                         url + server.url,
 		RegionURL:                   url + server.regionURL,
@@ -541,10 +542,10 @@ func getExpectedSubjectToken(url, region, accessKeyID, secretAccessKey, security
 	req.Header.Add("x-goog-cloud-target-resource", testFileConfig.Audience)
 	signer := &awsRequestSigner{
 		RegionName: region,
-		AwsSecurityCredentials: awsSecurityCredentials{
+		AwsSecurityCredentials: &AwsSecurityCredentials{
 			AccessKeyID:     accessKeyID,
 			SecretAccessKey: secretAccessKey,
-			SecurityToken:   securityToken,
+			SessionToken:    securityToken,
 		},
 	}
 	signer.SignRequest(req)
@@ -588,7 +589,6 @@ func TestAWSCredential_BasicRequest(t *testing.T) {
 
 	tfc := testFileConfig
 	tfc.CredentialSource = server.getCredentialSource(ts.URL)
-
 	oldGetenv := getenv
 	oldNow := now
 	defer func() {
@@ -846,7 +846,7 @@ func TestAWSCredential_RequestWithBadVersion(t *testing.T) {
 	if err == nil {
 		t.Fatalf("parse() should have failed")
 	}
-	if got, want := err.Error(), "oauth2/google: aws version '3' is not supported in the current build"; !reflect.DeepEqual(got, want) {
+	if got, want := err.Error(), "oauth2/google/externalaccount: aws version '3' is not supported in the current build"; !reflect.DeepEqual(got, want) {
 		t.Errorf("subjectToken = %q, want %q", got, want)
 	}
 }
@@ -875,7 +875,7 @@ func TestAWSCredential_RequestWithNoRegionURL(t *testing.T) {
 		t.Fatalf("retrieveSubjectToken() should have failed")
 	}
 
-	if got, want := err.Error(), "oauth2/google: unable to determine AWS region"; !reflect.DeepEqual(got, want) {
+	if got, want := err.Error(), "oauth2/google/externalaccount: unable to determine AWS region"; !reflect.DeepEqual(got, want) {
 		t.Errorf("subjectToken = %q, want %q", got, want)
 	}
 }
@@ -905,7 +905,7 @@ func TestAWSCredential_RequestWithBadRegionURL(t *testing.T) {
 		t.Fatalf("retrieveSubjectToken() should have failed")
 	}
 
-	if got, want := err.Error(), "oauth2/google: unable to retrieve AWS region - Not Found"; !reflect.DeepEqual(got, want) {
+	if got, want := err.Error(), "oauth2/google/externalaccount: unable to retrieve AWS region - Not Found"; !reflect.DeepEqual(got, want) {
 		t.Errorf("subjectToken = %q, want %q", got, want)
 	}
 }
@@ -937,7 +937,7 @@ func TestAWSCredential_RequestWithMissingCredential(t *testing.T) {
 		t.Fatalf("retrieveSubjectToken() should have failed")
 	}
 
-	if got, want := err.Error(), "oauth2/google: missing AccessKeyId credential"; !reflect.DeepEqual(got, want) {
+	if got, want := err.Error(), "oauth2/google/externalaccount: missing AccessKeyId credential"; !reflect.DeepEqual(got, want) {
 		t.Errorf("subjectToken = %q, want %q", got, want)
 	}
 }
@@ -969,7 +969,7 @@ func TestAWSCredential_RequestWithIncompleteCredential(t *testing.T) {
 		t.Fatalf("retrieveSubjectToken() should have failed")
 	}
 
-	if got, want := err.Error(), "oauth2/google: missing SecretAccessKey credential"; !reflect.DeepEqual(got, want) {
+	if got, want := err.Error(), "oauth2/google/externalaccount: missing SecretAccessKey credential"; !reflect.DeepEqual(got, want) {
 		t.Errorf("subjectToken = %q, want %q", got, want)
 	}
 }
@@ -998,7 +998,7 @@ func TestAWSCredential_RequestWithNoCredentialURL(t *testing.T) {
 		t.Fatalf("retrieveSubjectToken() should have failed")
 	}
 
-	if got, want := err.Error(), "oauth2/google: unable to determine the AWS metadata server security credentials endpoint"; !reflect.DeepEqual(got, want) {
+	if got, want := err.Error(), "oauth2/google/externalaccount: unable to determine the AWS metadata server security credentials endpoint"; !reflect.DeepEqual(got, want) {
 		t.Errorf("subjectToken = %q, want %q", got, want)
 	}
 }
@@ -1027,7 +1027,7 @@ func TestAWSCredential_RequestWithBadCredentialURL(t *testing.T) {
 		t.Fatalf("retrieveSubjectToken() should have failed")
 	}
 
-	if got, want := err.Error(), "oauth2/google: unable to retrieve AWS role name - Not Found"; !reflect.DeepEqual(got, want) {
+	if got, want := err.Error(), "oauth2/google/externalaccount: unable to retrieve AWS role name - Not Found"; !reflect.DeepEqual(got, want) {
 		t.Errorf("subjectToken = %q, want %q", got, want)
 	}
 }
@@ -1056,7 +1056,7 @@ func TestAWSCredential_RequestWithBadFinalCredentialURL(t *testing.T) {
 		t.Fatalf("retrieveSubjectToken() should have failed")
 	}
 
-	if got, want := err.Error(), "oauth2/google: unable to retrieve AWS security credentials - Not Found"; !reflect.DeepEqual(got, want) {
+	if got, want := err.Error(), "oauth2/google/externalaccount: unable to retrieve AWS security credentials - Not Found"; !reflect.DeepEqual(got, want) {
 		t.Errorf("subjectToken = %q, want %q", got, want)
 	}
 }
@@ -1235,6 +1235,192 @@ func TestAWSCredential_ShouldCallMetadataEndpointWhenNoSecretAccessKey(t *testin
 	}
 }
 
+func TestAWSCredential_ProgrammaticAuth(t *testing.T) {
+	tfc := testFileConfig
+	securityCredentials := AwsSecurityCredentials{
+		AccessKeyID:     accessKeyID,
+		SecretAccessKey: secretAccessKey,
+		SessionToken:    securityToken,
+	}
+
+	tfc.AwsSecurityCredentialsSupplier = testAwsSupplier{
+		awsRegion:   "us-east-2",
+		err:         nil,
+		credentials: &securityCredentials,
+	}
+
+	oldNow := now
+	defer func() {
+		now = oldNow
+	}()
+	now = setTime(defaultTime)
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	out, err := base.subjectToken()
+	if err != nil {
+		t.Fatalf("retrieveSubjectToken() failed: %v", err)
+	}
+
+	expected := getExpectedSubjectToken(
+		"https://sts.us-east-2.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15",
+		"us-east-2",
+		accessKeyID,
+		secretAccessKey,
+		securityToken,
+	)
+
+	if got, want := out, expected; !reflect.DeepEqual(got, want) {
+		t.Errorf("subjectToken = \n%q\n want \n%q", got, want)
+	}
+}
+
+func TestAWSCredential_ProgrammaticAuthNoSessionToken(t *testing.T) {
+	tfc := testFileConfig
+	securityCredentials := AwsSecurityCredentials{
+		AccessKeyID:     accessKeyID,
+		SecretAccessKey: secretAccessKey,
+	}
+
+	tfc.AwsSecurityCredentialsSupplier = testAwsSupplier{
+		awsRegion:   "us-east-2",
+		err:         nil,
+		credentials: &securityCredentials,
+	}
+
+	oldNow := now
+	defer func() {
+		now = oldNow
+	}()
+	now = setTime(defaultTime)
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	out, err := base.subjectToken()
+	if err != nil {
+		t.Fatalf("retrieveSubjectToken() failed: %v", err)
+	}
+
+	expected := getExpectedSubjectToken(
+		"https://sts.us-east-2.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15",
+		"us-east-2",
+		accessKeyID,
+		secretAccessKey,
+		"",
+	)
+
+	if got, want := out, expected; !reflect.DeepEqual(got, want) {
+		t.Errorf("subjectToken = \n%q\n want \n%q", got, want)
+	}
+}
+
+func TestAWSCredential_ProgrammaticAuthError(t *testing.T) {
+	tfc := testFileConfig
+	testErr := errors.New("test error")
+	tfc.AwsSecurityCredentialsSupplier = testAwsSupplier{
+		awsRegion:   "us-east-2",
+		err:         testErr,
+		credentials: nil,
+	}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	_, err = base.subjectToken()
+	if err == nil {
+		t.Fatalf("subjectToken() should have failed")
+	}
+	if err != testErr {
+		t.Errorf("error = %e, want %e", err, testErr)
+	}
+}
+
+func TestAWSCredential_ProgrammaticAuthRegionError(t *testing.T) {
+	tfc := testFileConfig
+	securityCredentials := AwsSecurityCredentials{
+		AccessKeyID:     accessKeyID,
+		SecretAccessKey: secretAccessKey,
+	}
+
+	testErr := errors.New("test")
+	tfc.AwsSecurityCredentialsSupplier = testAwsSupplier{
+		awsRegion:   "",
+		regionErr:   testErr,
+		credentials: &securityCredentials,
+	}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	_, err = base.subjectToken()
+	if err == nil {
+		t.Fatalf("subjectToken() should have failed")
+	}
+	if err != testErr {
+		t.Errorf("error = %e, want %e", err, testErr)
+	}
+}
+
+func TestAWSCredential_ProgrammaticAuthOptions(t *testing.T) {
+	tfc := testFileConfig
+	securityCredentials := AwsSecurityCredentials{
+		AccessKeyID:     accessKeyID,
+		SecretAccessKey: secretAccessKey,
+	}
+	expectedOptions := SupplierOptions{Audience: tfc.Audience, SubjectTokenType: tfc.SubjectTokenType}
+
+	tfc.AwsSecurityCredentialsSupplier = testAwsSupplier{
+		awsRegion:       "us-east-2",
+		credentials:     &securityCredentials,
+		expectedOptions: &expectedOptions,
+	}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	_, err = base.subjectToken()
+	if err != nil {
+		t.Fatalf("subjectToken() failed %v", err)
+	}
+}
+
+func TestAWSCredential_ProgrammaticAuthContext(t *testing.T) {
+	tfc := testFileConfig
+	securityCredentials := AwsSecurityCredentials{
+		AccessKeyID:     accessKeyID,
+		SecretAccessKey: secretAccessKey,
+	}
+	ctx := context.Background()
+
+	tfc.AwsSecurityCredentialsSupplier = testAwsSupplier{
+		awsRegion:       "us-east-2",
+		credentials:     &securityCredentials,
+		expectedContext: ctx,
+	}
+
+	base, err := tfc.parse(ctx)
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	_, err = base.subjectToken()
+	if err != nil {
+		t.Fatalf("subjectToken() failed %v", err)
+	}
+}
+
 func TestAwsCredential_CredentialSourceType(t *testing.T) {
 	server := createDefaultAwsTestServer()
 	ts := httptest.NewServer(server)
@@ -1251,3 +1437,52 @@ func TestAwsCredential_CredentialSourceType(t *testing.T) {
 		t.Errorf("got %v but want %v", got, want)
 	}
 }
+
+type testAwsSupplier struct {
+	err             error
+	regionErr       error
+	awsRegion       string
+	credentials     *AwsSecurityCredentials
+	expectedOptions *SupplierOptions
+	expectedContext context.Context
+}
+
+func (supp testAwsSupplier) AwsRegion(ctx context.Context, options SupplierOptions) (string, error) {
+	if supp.regionErr != nil {
+		return "", supp.regionErr
+	}
+	if supp.expectedOptions != nil {
+		if supp.expectedOptions.Audience != options.Audience {
+			return "", errors.New("Audience does not match")
+		}
+		if supp.expectedOptions.SubjectTokenType != options.SubjectTokenType {
+			return "", errors.New("Audience does not match")
+		}
+	}
+	if supp.expectedContext != nil {
+		if supp.expectedContext != ctx {
+			return "", errors.New("Context does not match")
+		}
+	}
+	return supp.awsRegion, nil
+}
+
+func (supp testAwsSupplier) AwsSecurityCredentials(ctx context.Context, options SupplierOptions) (*AwsSecurityCredentials, error) {
+	if supp.err != nil {
+		return nil, supp.err
+	}
+	if supp.expectedOptions != nil {
+		if supp.expectedOptions.Audience != options.Audience {
+			return nil, errors.New("Audience does not match")
+		}
+		if supp.expectedOptions.SubjectTokenType != options.SubjectTokenType {
+			return nil, errors.New("Audience does not match")
+		}
+	}
+	if supp.expectedContext != nil {
+		if supp.expectedContext != ctx {
+			return nil, errors.New("Context does not match")
+		}
+	}
+	return supp.credentials, nil
+}

google/externalaccount/basecredentials.go

@@ -0,0 +1,517 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package externalaccount provides support for creating workload identity
+federation and workforce identity federation token sources that can be
+used to access Google Cloud resources from external identity providers.
+
+# Workload Identity Federation
+
+Using workload identity federation, your application can access Google Cloud
+resources from Amazon Web Services (AWS), Microsoft Azure or any identity
+provider that supports OpenID Connect (OIDC) or SAML 2.0.
+Traditionally, applications running outside Google Cloud have used service
+account keys to access Google Cloud resources. Using identity federation,
+you can allow your workload to impersonate a service account.
+This lets you access Google Cloud resources directly, eliminating the
+maintenance and security burden associated with service account keys.
+
+Follow the detailed instructions on how to configure Workload Identity Federation
+in various platforms:
+
+Amazon Web Services (AWS): https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#aws
+Microsoft Azure: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#azure
+OIDC identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#oidc
+SAML 2.0 identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#saml
+
+For OIDC and SAML providers, the library can retrieve tokens in fours ways:
+from a local file location (file-sourced credentials), from a server
+(URL-sourced credentials), from a local executable (executable-sourced
+credentials), or from a user defined function that returns an OIDC or SAML token.
+For file-sourced credentials, a background process needs to be continuously
+refreshing the file location with a new OIDC/SAML token prior to expiration.
+For tokens with one hour lifetimes, the token needs to be updated in the file
+every hour. The token can be stored directly as plain text or in JSON format.
+For URL-sourced credentials, a local server needs to host a GET endpoint to
+return the OIDC/SAML token. The response can be in plain text or JSON.
+Additional required request headers can also be specified.
+For executable-sourced credentials, an application needs to be available to
+output the OIDC/SAML token and other information in a JSON format.
+For more information on how these work (and how to implement
+executable-sourced credentials), please check out:
+https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#create_a_credential_configuration
+
+To use a custom function to supply the token, define a struct that implements the [SubjectTokenSupplier] interface for OIDC/SAML providers,
+or one that implements [AwsSecurityCredentialsSupplier] for AWS providers. This can then be used when building a [Config].
+The [golang.org/x/oauth2.TokenSource] created from the config using [NewTokenSource] can then be used to access Google
+Cloud resources. For instance, you can create a new client from the
+[cloud.google.com/go/storage] package and pass in option.WithTokenSource(yourTokenSource))
+
+Note that this library does not perform any validation on the token_url, token_info_url,
+or service_account_impersonation_url fields of the credential configuration.
+It is not recommended to use a credential configuration that you did not generate with
+the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
+
+# Workforce Identity Federation
+
+Workforce identity federation lets you use an external identity provider (IdP) to
+authenticate and authorize a workforce—a group of users, such as employees, partners,
+and contractors—using IAM, so that the users can access Google Cloud services.
+Workforce identity federation extends Google Cloud's identity capabilities to support
+syncless, attribute-based single sign on.
+
+With workforce identity federation, your workforce can access Google Cloud resources
+using an external identity provider (IdP) that supports OpenID Connect (OIDC) or
+SAML 2.0 such as Azure Active Directory (Azure AD), Active Directory Federation
+Services (AD FS), Okta, and others.
+
+Follow the detailed instructions on how to configure Workload Identity Federation
+in various platforms:
+
+Azure AD: https://cloud.google.com/iam/docs/workforce-sign-in-azure-ad
+Okta: https://cloud.google.com/iam/docs/workforce-sign-in-okta
+OIDC identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#oidc
+SAML 2.0 identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#saml
+
+For workforce identity federation, the library can retrieve tokens in four ways:
+from a local file location (file-sourced credentials), from a server
+(URL-sourced credentials), from a local executable (executable-sourced
+credentials), or from a user supplied function that returns an OIDC or SAML token.
+For file-sourced credentials, a background process needs to be continuously
+refreshing the file location with a new OIDC/SAML token prior to expiration.
+For tokens with one hour lifetimes, the token needs to be updated in the file
+every hour. The token can be stored directly as plain text or in JSON format.
+For URL-sourced credentials, a local server needs to host a GET endpoint to
+return the OIDC/SAML token. The response can be in plain text or JSON.
+Additional required request headers can also be specified.
+For executable-sourced credentials, an application needs to be available to
+output the OIDC/SAML token and other information in a JSON format.
+For more information on how these work (and how to implement
+executable-sourced credentials), please check out:
+https://cloud.google.com/iam/docs/workforce-obtaining-short-lived-credentials#generate_a_configuration_file_for_non-interactive_sign-in
+
+To use a custom function to supply the token, define a struct that implements the [SubjectTokenSupplier] interface for OIDC/SAML providers.
+This can then be used when building a [Config].
+The [golang.org/x/oauth2.TokenSource] created from the config using [NewTokenSource] can then be used access Google
+Cloud resources. For instance, you can create a new client from the
+[cloud.google.com/go/storage] package and pass in option.WithTokenSource(yourTokenSource))
+
+# Security considerations
+
+Note that this library does not perform any validation on the token_url, token_info_url,
+or service_account_impersonation_url fields of the credential configuration.
+It is not recommended to use a credential configuration that you did not generate with
+the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
+*/
+package externalaccount
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/google/internal/impersonate"
+	"golang.org/x/oauth2/google/internal/stsexchange"
+)
+
+const (
+	universeDomainPlaceholder = "UNIVERSE_DOMAIN"
+	defaultTokenURL           = "https://sts.UNIVERSE_DOMAIN/v1/token"
+	defaultUniverseDomain     = "googleapis.com"
+)
+
+// now aliases time.Now for testing
+var now = func() time.Time {
+	return time.Now().UTC()
+}
+
+// Config stores the configuration for fetching tokens with external credentials.
+type Config struct {
+	// Audience is the Secure Token Service (STS) audience which contains the resource name for the workload
+	// identity pool or the workforce pool and the provider identifier in that pool. Required.
+	Audience string
+	// SubjectTokenType is the STS token type based on the Oauth2.0 token exchange spec.
+	// Expected values include:
+	// “urn:ietf:params:oauth:token-type:jwt”
+	// “urn:ietf:params:oauth:token-type:id-token”
+	// “urn:ietf:params:oauth:token-type:saml2”
+	// “urn:ietf:params:aws:token-type:aws4_request”
+	// Required.
+	SubjectTokenType string
+	// TokenURL is the STS token exchange endpoint. If not provided, will default to
+	// https://sts.UNIVERSE_DOMAIN/v1/token, with UNIVERSE_DOMAIN set to the
+	// default service domain googleapis.com unless UniverseDomain is set.
+	// Optional.
+	TokenURL string
+	// TokenInfoURL is the token_info endpoint used to retrieve the account related information (
+	// user attributes like account identifier, eg. email, username, uid, etc). This is
+	// needed for gCloud session account identification. Optional.
+	TokenInfoURL string
+	// ServiceAccountImpersonationURL is the URL for the service account impersonation request. This is only
+	// required for workload identity pools when APIs to be accessed have not integrated with UberMint. Optional.
+	ServiceAccountImpersonationURL string
+	// ServiceAccountImpersonationLifetimeSeconds is the number of seconds the service account impersonation
+	// token will be valid for. If not provided, it will default to 3600. Optional.
+	ServiceAccountImpersonationLifetimeSeconds int
+	// ClientSecret is currently only required if token_info endpoint also
+	// needs to be called with the generated GCP access token. When provided, STS will be
+	// called with additional basic authentication using ClientId as username and ClientSecret as password. Optional.
+	ClientSecret string
+	// ClientID is only required in conjunction with ClientSecret, as described above. Optional.
+	ClientID string
+	// CredentialSource contains the necessary information to retrieve the token itself, as well
+	// as some environmental information. One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or
+	// CredentialSource must be provided. Optional.
+	CredentialSource *CredentialSource
+	// QuotaProjectID is injected by gCloud. If the value is non-empty, the Auth libraries
+	// will set the x-goog-user-project header which overrides the project associated with the credentials. Optional.
+	QuotaProjectID string
+	// Scopes contains the desired scopes for the returned access token. Optional.
+	Scopes []string
+	// WorkforcePoolUserProject is the workforce pool user project number when the credential
+	// corresponds to a workforce pool and not a workload identity pool.
+	// The underlying principal must still have serviceusage.services.use IAM
+	// permission to use the project for billing/quota. Optional.
+	WorkforcePoolUserProject string
+	// SubjectTokenSupplier is an optional token supplier for OIDC/SAML credentials.
+	// One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or CredentialSource must be provided. Optional.
+	SubjectTokenSupplier SubjectTokenSupplier
+	// AwsSecurityCredentialsSupplier is an AWS Security Credential supplier for AWS credentials.
+	// One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or CredentialSource must be provided. Optional.
+	AwsSecurityCredentialsSupplier AwsSecurityCredentialsSupplier
+	// UniverseDomain is the default service domain for a given Cloud universe.
+	// This value will be used in the default STS token URL. The default value
+	// is "googleapis.com". It will not be used if TokenURL is set. Optional.
+	UniverseDomain string
+}
+
+var (
+	validWorkforceAudiencePattern *regexp.Regexp = regexp.MustCompile(`//iam\.googleapis\.com/locations/[^/]+/workforcePools/`)
+)
+
+func validateWorkforceAudience(input string) bool {
+	return validWorkforceAudiencePattern.MatchString(input)
+}
+
+// NewTokenSource Returns an external account TokenSource using the provided external account config.
+func NewTokenSource(ctx context.Context, conf Config) (oauth2.TokenSource, error) {
+	if conf.Audience == "" {
+		return nil, fmt.Errorf("oauth2/google/externalaccount: Audience must be set")
+	}
+	if conf.SubjectTokenType == "" {
+		return nil, fmt.Errorf("oauth2/google/externalaccount: Subject token type must be set")
+	}
+	if conf.WorkforcePoolUserProject != "" {
+		valid := validateWorkforceAudience(conf.Audience)
+		if !valid {
+			return nil, fmt.Errorf("oauth2/google/externalaccount: Workforce pool user project should not be set for non-workforce pool credentials")
+		}
+	}
+	count := 0
+	if conf.CredentialSource != nil {
+		count++
+	}
+	if conf.SubjectTokenSupplier != nil {
+		count++
+	}
+	if conf.AwsSecurityCredentialsSupplier != nil {
+		count++
+	}
+	if count == 0 {
+		return nil, fmt.Errorf("oauth2/google/externalaccount: One of CredentialSource, SubjectTokenSupplier, or AwsSecurityCredentialsSupplier must be set")
+	}
+	if count > 1 {
+		return nil, fmt.Errorf("oauth2/google/externalaccount: Only one of CredentialSource, SubjectTokenSupplier, or AwsSecurityCredentialsSupplier must be set")
+	}
+	return conf.tokenSource(ctx, "https")
+}
+
+// tokenSource is a private function that's directly called by some of the tests,
+// because the unit test URLs are mocked, and would otherwise fail the
+// validity check.
+func (c *Config) tokenSource(ctx context.Context, scheme string) (oauth2.TokenSource, error) {
+
+	ts := tokenSource{
+		ctx:  ctx,
+		conf: c,
+	}
+	if c.ServiceAccountImpersonationURL == "" {
+		return oauth2.ReuseTokenSource(nil, ts), nil
+	}
+	scopes := c.Scopes
+	ts.conf.Scopes = []string{"https://www.googleapis.com/auth/cloud-platform"}
+	imp := impersonate.ImpersonateTokenSource{
+		Ctx:                  ctx,
+		URL:                  c.ServiceAccountImpersonationURL,
+		Scopes:               scopes,
+		Ts:                   oauth2.ReuseTokenSource(nil, ts),
+		TokenLifetimeSeconds: c.ServiceAccountImpersonationLifetimeSeconds,
+	}
+	return oauth2.ReuseTokenSource(nil, imp), nil
+}
+
+// Subject token file types.
+const (
+	fileTypeText = "text"
+	fileTypeJSON = "json"
+)
+
+// Format contains information needed to retrieve a subject token for URL or File sourced credentials.
+type Format struct {
+	// Type should be either "text" or "json". This determines whether the file or URL sourced credentials
+	// expect a simple text subject token or if the subject token will be contained in a JSON object.
+	// When not provided "text" type is assumed.
+	Type string `json:"type"`
+	// SubjectTokenFieldName is only required for JSON format. This is the field name that the credentials will check
+	// for the subject token in the file or URL response. This would be "access_token" for azure.
+	SubjectTokenFieldName string `json:"subject_token_field_name"`
+}
+
+// CredentialSource stores the information necessary to retrieve the credentials for the STS exchange.
+type CredentialSource struct {
+	// File is the location for file sourced credentials.
+	// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
+	//
+	// Important: If you accept a credential configuration (credential
+	// JSON/File/Stream) from an external source for authentication to Google
+	// Cloud Platform, you must validate it before providing it to any Google
+	// API or library. Providing an unvalidated credential configuration to
+	// Google APIs can compromise the security of your systems and data. For
+	// more information, refer to [Validate credential configurations from
+	// external sources](https://cloud.google.com/docs/authentication/external/externally-sourced-credentials).
+	File string `json:"file"`
+
+	// Url is the URL to call for URL sourced credentials.
+	// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
+	//
+	// Important: If you accept a credential configuration (credential
+	// JSON/File/Stream) from an external source for authentication to Google
+	// Cloud Platform, you must validate it before providing it to any Google
+	// API or library. Providing an unvalidated credential configuration to
+	// Google APIs can compromise the security of your systems and data. For
+	// more information, refer to [Validate credential configurations from
+	// external sources](https://cloud.google.com/docs/authentication/external/externally-sourced-credentials).
+	URL string `json:"url"`
+	// Headers are the headers to attach to the request for URL sourced credentials.
+	Headers map[string]string `json:"headers"`
+
+	// Executable is the configuration object for executable sourced credentials.
+	// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
+	//
+	// Important: If you accept a credential configuration (credential
+	// JSON/File/Stream) from an external source for authentication to Google
+	// Cloud Platform, you must validate it before providing it to any Google
+	// API or library. Providing an unvalidated credential configuration to
+	// Google APIs can compromise the security of your systems and data. For
+	// more information, refer to [Validate credential configurations from
+	// external sources](https://cloud.google.com/docs/authentication/external/externally-sourced-credentials).
+	Executable *ExecutableConfig `json:"executable"`
+
+	// EnvironmentID is the EnvironmentID used for AWS sourced credentials. This should start with "AWS".
+	// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
+	//
+	// Important: If you accept a credential configuration (credential
+	// JSON/File/Stream) from an external source for authentication to Google
+	// Cloud Platform, you must validate it before providing it to any Google
+	// API or library. Providing an unvalidated credential configuration to
+	// Google APIs can compromise the security of your systems and data. For
+	// more information, refer to [Validate credential configurations from
+	// external sources](https://cloud.google.com/docs/authentication/external/externally-sourced-credentials).
+	EnvironmentID string `json:"environment_id"`
+	// RegionURL is the metadata URL to retrieve the region from for EC2 AWS credentials.
+	RegionURL string `json:"region_url"`
+	// RegionalCredVerificationURL is the AWS regional credential verification URL, will default to
+	//  "https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15" if not provided."
+	RegionalCredVerificationURL string `json:"regional_cred_verification_url"`
+	// IMDSv2SessionTokenURL is the URL to retrieve the session token when using IMDSv2 in AWS.
+	IMDSv2SessionTokenURL string `json:"imdsv2_session_token_url"`
+	// Format is the format type for the subject token. Used for File and URL sourced credentials. Expected values are "text" or "json".
+	Format Format `json:"format"`
+}
+
+// ExecutableConfig contains information needed for executable sourced credentials.
+type ExecutableConfig struct {
+	// Command is the the full command to run to retrieve the subject token.
+	// This can include arguments. Must be an absolute path for the program. Required.
+	Command string `json:"command"`
+	// TimeoutMillis is the timeout duration, in milliseconds. Defaults to 30000 milliseconds when not provided. Optional.
+	TimeoutMillis *int `json:"timeout_millis"`
+	// OutputFile is the absolute path to the output file where the executable will cache the response.
+	// If specified the auth libraries will first check this location before running the executable. Optional.
+	OutputFile string `json:"output_file"`
+}
+
+// SubjectTokenSupplier can be used to supply a subject token to exchange for a GCP access token.
+type SubjectTokenSupplier interface {
+	// SubjectToken should return a valid subject token or an error.
+	// The external account token source does not cache the returned subject token, so caching
+	// logic should be implemented in the supplier to prevent multiple requests for the same subject token.
+	SubjectToken(ctx context.Context, options SupplierOptions) (string, error)
+}
+
+// AWSSecurityCredentialsSupplier can be used to supply AwsSecurityCredentials and an AWS Region to
+// exchange for a GCP access token.
+type AwsSecurityCredentialsSupplier interface {
+	// AwsRegion should return the AWS region or an error.
+	AwsRegion(ctx context.Context, options SupplierOptions) (string, error)
+	// AwsSecurityCredentials should return a valid set of AwsSecurityCredentials or an error.
+	// The external account token source does not cache the returned security credentials, so caching
+	// logic should be implemented in the supplier to prevent multiple requests for the same security credentials.
+	AwsSecurityCredentials(ctx context.Context, options SupplierOptions) (*AwsSecurityCredentials, error)
+}
+
+// SupplierOptions contains information about the requested subject token or AWS security credentials from the
+// Google external account credential.
+type SupplierOptions struct {
+	// Audience is the requested audience for the external account credential.
+	Audience string
+	// Subject token type is the requested subject token type for the external account credential. Expected values include:
+	// “urn:ietf:params:oauth:token-type:jwt”
+	// “urn:ietf:params:oauth:token-type:id-token”
+	// “urn:ietf:params:oauth:token-type:saml2”
+	// “urn:ietf:params:aws:token-type:aws4_request”
+	SubjectTokenType string
+}
+
+// tokenURL returns the default STS token endpoint with the configured universe
+// domain.
+func (c *Config) tokenURL() string {
+	if c.UniverseDomain == "" {
+		return strings.Replace(defaultTokenURL, universeDomainPlaceholder, defaultUniverseDomain, 1)
+	}
+	return strings.Replace(defaultTokenURL, universeDomainPlaceholder, c.UniverseDomain, 1)
+}
+
+// parse determines the type of CredentialSource needed.
+func (c *Config) parse(ctx context.Context) (baseCredentialSource, error) {
+	//set Defaults
+	if c.TokenURL == "" {
+		c.TokenURL = c.tokenURL()
+	}
+	supplierOptions := SupplierOptions{Audience: c.Audience, SubjectTokenType: c.SubjectTokenType}
+
+	if c.AwsSecurityCredentialsSupplier != nil {
+		awsCredSource := awsCredentialSource{
+			awsSecurityCredentialsSupplier: c.AwsSecurityCredentialsSupplier,
+			targetResource:                 c.Audience,
+			supplierOptions:                supplierOptions,
+			ctx:                            ctx,
+		}
+		return awsCredSource, nil
+	} else if c.SubjectTokenSupplier != nil {
+		return programmaticRefreshCredentialSource{subjectTokenSupplier: c.SubjectTokenSupplier, supplierOptions: supplierOptions, ctx: ctx}, nil
+	} else if len(c.CredentialSource.EnvironmentID) > 3 && c.CredentialSource.EnvironmentID[:3] == "aws" {
+		if awsVersion, err := strconv.Atoi(c.CredentialSource.EnvironmentID[3:]); err == nil {
+			if awsVersion != 1 {
+				return nil, fmt.Errorf("oauth2/google/externalaccount: aws version '%d' is not supported in the current build", awsVersion)
+			}
+
+			awsCredSource := awsCredentialSource{
+				environmentID:               c.CredentialSource.EnvironmentID,
+				regionURL:                   c.CredentialSource.RegionURL,
+				regionalCredVerificationURL: c.CredentialSource.RegionalCredVerificationURL,
+				credVerificationURL:         c.CredentialSource.URL,
+				targetResource:              c.Audience,
+				ctx:                         ctx,
+			}
+			if c.CredentialSource.IMDSv2SessionTokenURL != "" {
+				awsCredSource.imdsv2SessionTokenURL = c.CredentialSource.IMDSv2SessionTokenURL
+			}
+
+			return awsCredSource, nil
+		}
+	} else if c.CredentialSource.File != "" {
+		return fileCredentialSource{File: c.CredentialSource.File, Format: c.CredentialSource.Format}, nil
+	} else if c.CredentialSource.URL != "" {
+		return urlCredentialSource{URL: c.CredentialSource.URL, Headers: c.CredentialSource.Headers, Format: c.CredentialSource.Format, ctx: ctx}, nil
+	} else if c.CredentialSource.Executable != nil {
+		return createExecutableCredential(ctx, c.CredentialSource.Executable, c)
+	}
+	return nil, fmt.Errorf("oauth2/google/externalaccount: unable to parse credential source")
+}
+
+type baseCredentialSource interface {
+	credentialSourceType() string
+	subjectToken() (string, error)
+}
+
+// tokenSource is the source that handles external credentials. It is used to retrieve Tokens.
+type tokenSource struct {
+	ctx  context.Context
+	conf *Config
+}
+
+func getMetricsHeaderValue(conf *Config, credSource baseCredentialSource) string {
+	return fmt.Sprintf("gl-go/%s auth/%s google-byoid-sdk source/%s sa-impersonation/%t config-lifetime/%t",
+		goVersion(),
+		"unknown",
+		credSource.credentialSourceType(),
+		conf.ServiceAccountImpersonationURL != "",
+		conf.ServiceAccountImpersonationLifetimeSeconds != 0)
+}
+
+// Token allows tokenSource to conform to the oauth2.TokenSource interface.
+func (ts tokenSource) Token() (*oauth2.Token, error) {
+	conf := ts.conf
+
+	credSource, err := conf.parse(ts.ctx)
+	if err != nil {
+		return nil, err
+	}
+	subjectToken, err := credSource.subjectToken()
+
+	if err != nil {
+		return nil, err
+	}
+	stsRequest := stsexchange.TokenExchangeRequest{
+		GrantType:          "urn:ietf:params:oauth:grant-type:token-exchange",
+		Audience:           conf.Audience,
+		Scope:              conf.Scopes,
+		RequestedTokenType: "urn:ietf:params:oauth:token-type:access_token",
+		SubjectToken:       subjectToken,
+		SubjectTokenType:   conf.SubjectTokenType,
+	}
+	header := make(http.Header)
+	header.Add("Content-Type", "application/x-www-form-urlencoded")
+	header.Add("x-goog-api-client", getMetricsHeaderValue(conf, credSource))
+	clientAuth := stsexchange.ClientAuthentication{
+		AuthStyle:    oauth2.AuthStyleInHeader,
+		ClientID:     conf.ClientID,
+		ClientSecret: conf.ClientSecret,
+	}
+	var options map[string]any
+	// Do not pass workforce_pool_user_project when client authentication is used.
+	// The client ID is sufficient for determining the user project.
+	if conf.WorkforcePoolUserProject != "" && conf.ClientID == "" {
+		options = map[string]any{
+			"userProject": conf.WorkforcePoolUserProject,
+		}
+	}
+	stsResp, err := stsexchange.ExchangeToken(ts.ctx, conf.TokenURL, &stsRequest, clientAuth, header, options)
+	if err != nil {
+		return nil, err
+	}
+
+	accessToken := &oauth2.Token{
+		AccessToken: stsResp.AccessToken,
+		TokenType:   stsResp.TokenType,
+	}
+
+	// The RFC8693 doesn't define the explicit 0 of "expires_in" field behavior.
+	if stsResp.ExpiresIn <= 0 {
+		return nil, fmt.Errorf("oauth2/google/externalaccount: got invalid expiry from security token service")
+	}
+	accessToken.Expiry = now().Add(time.Duration(stsResp.ExpiresIn) * time.Second)
+
+	if stsResp.RefreshToken != "" {
+		accessToken.RefreshToken = stsResp.RefreshToken
+	}
+	return accessToken, nil
+}

google/externalaccount/basecredentials_test.go

@@ -0,0 +1,574 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package externalaccount
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"golang.org/x/oauth2"
+)
+
+const (
+	textBaseCredPath             = "testdata/3pi_cred.txt"
+	jsonBaseCredPath             = "testdata/3pi_cred.json"
+	baseImpersonateCredsReqBody  = "audience=32555940559.apps.googleusercontent.com&grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange&requested_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fcloud-platform&subject_token=street123&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Ajwt"
+	baseImpersonateCredsRespBody = `{"accessToken":"Second.Access.Token","expireTime":"2020-12-28T15:01:23Z"}`
+)
+
+var testBaseCredSource = CredentialSource{
+	File:   textBaseCredPath,
+	Format: Format{Type: fileTypeText},
+}
+
+var testConfig = Config{
+	Audience:         "32555940559.apps.googleusercontent.com",
+	SubjectTokenType: "urn:ietf:params:oauth:token-type:jwt",
+	TokenInfoURL:     "http://localhost:8080/v1/tokeninfo",
+	ClientSecret:     "notsosecret",
+	ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
+	CredentialSource: &testBaseCredSource,
+	Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+}
+
+var (
+	baseCredsRequestBody                          = "audience=32555940559.apps.googleusercontent.com&grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange&requested_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fdevstorage.full_control&subject_token=street123&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aid_token"
+	baseCredsResponseBody                         = `{"access_token":"Sample.Access.Token","issued_token_type":"urn:ietf:params:oauth:token-type:access_token","token_type":"Bearer","expires_in":3600,"scope":"https://www.googleapis.com/auth/cloud-platform"}`
+	workforcePoolRequestBodyWithClientId          = "audience=%2F%2Fiam.googleapis.com%2Flocations%2Feu%2FworkforcePools%2Fpool-id%2Fproviders%2Fprovider-id&grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange&requested_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fdevstorage.full_control&subject_token=street123&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aid_token"
+	workforcePoolRequestBodyWithoutClientId       = "audience=%2F%2Fiam.googleapis.com%2Flocations%2Feu%2FworkforcePools%2Fpool-id%2Fproviders%2Fprovider-id&grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange&options=%7B%22userProject%22%3A%22myProject%22%7D&requested_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fdevstorage.full_control&subject_token=street123&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aid_token"
+	correctAT                                     = "Sample.Access.Token"
+	expiry                                  int64 = 234852
+)
+var (
+	testNow = func() time.Time { return time.Unix(expiry, 0) }
+)
+
+type testExchangeTokenServer struct {
+	url           string
+	authorization string
+	contentType   string
+	metricsHeader string
+	body          string
+	response      string
+}
+
+func run(t *testing.T, config *Config, tets *testExchangeTokenServer) (*oauth2.Token, error) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if got, want := r.URL.String(), tets.url; got != want {
+			t.Errorf("URL.String(): got %v but want %v", got, want)
+		}
+		headerAuth := r.Header.Get("Authorization")
+		if got, want := headerAuth, tets.authorization; got != want {
+			t.Errorf("got %v but want %v", got, want)
+		}
+		headerContentType := r.Header.Get("Content-Type")
+		if got, want := headerContentType, tets.contentType; got != want {
+			t.Errorf("got %v but want %v", got, want)
+		}
+		headerMetrics := r.Header.Get("x-goog-api-client")
+		if got, want := headerMetrics, tets.metricsHeader; got != want {
+			t.Errorf("got %v but want %v", got, want)
+		}
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("Failed reading request body: %s.", err)
+		}
+		if got, want := string(body), tets.body; got != want {
+			t.Errorf("Unexpected exchange payload: got %v but want %v", got, want)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.Write([]byte(tets.response))
+	}))
+	defer server.Close()
+	config.TokenURL = server.URL
+
+	oldNow := now
+	defer func() { now = oldNow }()
+	now = testNow
+
+	ts := tokenSource{
+		ctx:  context.Background(),
+		conf: config,
+	}
+
+	return ts.Token()
+}
+
+func validateToken(t *testing.T, tok *oauth2.Token, expectToken *oauth2.Token) {
+	if expectToken == nil {
+		return
+	}
+	if got, want := tok.AccessToken, expectToken.AccessToken; got != want {
+		t.Errorf("Unexpected access token: got %v, but wanted %v", got, want)
+	}
+	if got, want := tok.TokenType, expectToken.TokenType; got != want {
+		t.Errorf("Unexpected TokenType: got %v, but wanted %v", got, want)
+	}
+
+	if got, want := tok.Expiry, expectToken.Expiry; got != want {
+		t.Errorf("Unexpected Expiry: got %v, but wanted %v", got, want)
+	}
+}
+
+func createImpersonationServer(urlWanted, authWanted, bodyWanted, response string, t *testing.T) *httptest.Server {
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if got, want := r.URL.String(), urlWanted; got != want {
+			t.Errorf("URL.String(): got %v but want %v", got, want)
+		}
+		headerAuth := r.Header.Get("Authorization")
+		if got, want := headerAuth, authWanted; got != want {
+			t.Errorf("got %v but want %v", got, want)
+		}
+		headerContentType := r.Header.Get("Content-Type")
+		if got, want := headerContentType, "application/json"; got != want {
+			t.Errorf("got %v but want %v", got, want)
+		}
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("Failed reading request body: %v.", err)
+		}
+		if got, want := string(body), bodyWanted; got != want {
+			t.Errorf("Unexpected impersonation payload: got %v but want %v", got, want)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.Write([]byte(response))
+	}))
+}
+
+func createTargetServer(metricsHeaderWanted string, t *testing.T) *httptest.Server {
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if got, want := r.URL.String(), "/"; got != want {
+			t.Errorf("URL.String(): got %v but want %v", got, want)
+		}
+		headerAuth := r.Header.Get("Authorization")
+		if got, want := headerAuth, "Basic cmJyZ25vZ25yaG9uZ28zYmk0Z2I5Z2hnOWc6bm90c29zZWNyZXQ="; got != want {
+			t.Errorf("got %v but want %v", got, want)
+		}
+		headerContentType := r.Header.Get("Content-Type")
+		if got, want := headerContentType, "application/x-www-form-urlencoded"; got != want {
+			t.Errorf("got %v but want %v", got, want)
+		}
+		headerMetrics := r.Header.Get("x-goog-api-client")
+		if got, want := headerMetrics, metricsHeaderWanted; got != want {
+			t.Errorf("got %v but want %v", got, want)
+		}
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("Failed reading request body: %v.", err)
+		}
+		if got, want := string(body), baseImpersonateCredsReqBody; got != want {
+			t.Errorf("Unexpected exchange payload: got %v but want %v", got, want)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.Write([]byte(baseCredsResponseBody))
+	}))
+}
+
+func getExpectedMetricsHeader(source string, saImpersonation bool, configLifetime bool) string {
+	return fmt.Sprintf("gl-go/%s auth/unknown google-byoid-sdk source/%s sa-impersonation/%t config-lifetime/%t", goVersion(), source, saImpersonation, configLifetime)
+}
+
+func TestToken(t *testing.T) {
+	type MockSTSResponse struct {
+		AccessToken     string `json:"access_token"`
+		IssuedTokenType string `json:"issued_token_type"`
+		TokenType       string `json:"token_type"`
+		ExpiresIn       int32  `json:"expires_in,omitempty"`
+		Scope           string `json:"scopre,omitenpty"`
+	}
+
+	testCases := []struct {
+		name           string
+		responseBody   MockSTSResponse
+		expectToken    *oauth2.Token
+		expectErrorMsg string
+	}{
+		{
+			name: "happy case",
+			responseBody: MockSTSResponse{
+				AccessToken:     correctAT,
+				IssuedTokenType: "urn:ietf:params:oauth:token-type:access_token",
+				TokenType:       "Bearer",
+				ExpiresIn:       3600,
+				Scope:           "https://www.googleapis.com/auth/cloud-platform",
+			},
+			expectToken: &oauth2.Token{
+				AccessToken: correctAT,
+				TokenType:   "Bearer",
+				Expiry:      testNow().Add(time.Duration(3600) * time.Second),
+			},
+		},
+		{
+			name: "no expiry time on token",
+			responseBody: MockSTSResponse{
+				AccessToken:     correctAT,
+				IssuedTokenType: "urn:ietf:params:oauth:token-type:access_token",
+				TokenType:       "Bearer",
+				Scope:           "https://www.googleapis.com/auth/cloud-platform",
+			},
+			expectToken:    nil,
+			expectErrorMsg: "oauth2/google/externalaccount: got invalid expiry from security token service",
+		},
+		{
+			name: "negative expiry time",
+			responseBody: MockSTSResponse{
+				AccessToken:     correctAT,
+				IssuedTokenType: "urn:ietf:params:oauth:token-type:access_token",
+				TokenType:       "Bearer",
+				ExpiresIn:       -1,
+				Scope:           "https://www.googleapis.com/auth/cloud-platform",
+			},
+			expectToken:    nil,
+			expectErrorMsg: "oauth2/google/externalaccount: got invalid expiry from security token service",
+		},
+	}
+
+	for _, testCase := range testCases {
+		config := Config{
+			Audience:         "32555940559.apps.googleusercontent.com",
+			SubjectTokenType: "urn:ietf:params:oauth:token-type:id_token",
+			ClientSecret:     "notsosecret",
+			ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
+			CredentialSource: &testBaseCredSource,
+			Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+		}
+
+		responseBody, err := json.Marshal(testCase.responseBody)
+		if err != nil {
+			t.Errorf("Invalid response received.")
+		}
+
+		server := testExchangeTokenServer{
+			url:           "/",
+			authorization: "Basic cmJyZ25vZ25yaG9uZ28zYmk0Z2I5Z2hnOWc6bm90c29zZWNyZXQ=",
+			contentType:   "application/x-www-form-urlencoded",
+			metricsHeader: getExpectedMetricsHeader("file", false, false),
+			body:          baseCredsRequestBody,
+			response:      string(responseBody),
+		}
+
+		tok, err := run(t, &config, &server)
+
+		if err != nil && err.Error() != testCase.expectErrorMsg {
+			t.Errorf("Error not as expected: got = %v, and want = %v", err, testCase.expectErrorMsg)
+		}
+		validateToken(t, tok, testCase.expectToken)
+	}
+}
+
+func TestWorkforcePoolTokenWithClientID(t *testing.T) {
+	config := Config{
+		Audience:                 "//iam.googleapis.com/locations/eu/workforcePools/pool-id/providers/provider-id",
+		SubjectTokenType:         "urn:ietf:params:oauth:token-type:id_token",
+		ClientSecret:             "notsosecret",
+		ClientID:                 "rbrgnognrhongo3bi4gb9ghg9g",
+		CredentialSource:         &testBaseCredSource,
+		Scopes:                   []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+		WorkforcePoolUserProject: "myProject",
+	}
+
+	server := testExchangeTokenServer{
+		url:           "/",
+		authorization: "Basic cmJyZ25vZ25yaG9uZ28zYmk0Z2I5Z2hnOWc6bm90c29zZWNyZXQ=",
+		contentType:   "application/x-www-form-urlencoded",
+		metricsHeader: getExpectedMetricsHeader("file", false, false),
+		body:          workforcePoolRequestBodyWithClientId,
+		response:      baseCredsResponseBody,
+	}
+
+	tok, err := run(t, &config, &server)
+
+	if err != nil {
+		t.Fatalf("Unexpected error: %e", err)
+	}
+	expectToken := oauth2.Token{
+		AccessToken: correctAT,
+		TokenType:   "Bearer",
+		Expiry:      testNow().Add(time.Duration(3600) * time.Second),
+	}
+	validateToken(t, tok, &expectToken)
+}
+
+func TestWorkforcePoolTokenWithoutClientID(t *testing.T) {
+	config := Config{
+		Audience:                 "//iam.googleapis.com/locations/eu/workforcePools/pool-id/providers/provider-id",
+		SubjectTokenType:         "urn:ietf:params:oauth:token-type:id_token",
+		ClientSecret:             "notsosecret",
+		CredentialSource:         &testBaseCredSource,
+		Scopes:                   []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+		WorkforcePoolUserProject: "myProject",
+	}
+
+	server := testExchangeTokenServer{
+		url:           "/",
+		authorization: "",
+		contentType:   "application/x-www-form-urlencoded",
+		metricsHeader: getExpectedMetricsHeader("file", false, false),
+		body:          workforcePoolRequestBodyWithoutClientId,
+		response:      baseCredsResponseBody,
+	}
+
+	tok, err := run(t, &config, &server)
+
+	if err != nil {
+		t.Fatalf("Unexpected error: %e", err)
+	}
+	expectToken := oauth2.Token{
+		AccessToken: correctAT,
+		TokenType:   "Bearer",
+		Expiry:      testNow().Add(time.Duration(3600) * time.Second),
+	}
+	validateToken(t, tok, &expectToken)
+}
+
+func TestNonworkforceWithWorkforcePoolUserProject(t *testing.T) {
+	config := Config{
+		Audience:                 "32555940559.apps.googleusercontent.com",
+		SubjectTokenType:         "urn:ietf:params:oauth:token-type:id_token",
+		TokenURL:                 "https://sts.googleapis.com",
+		ClientSecret:             "notsosecret",
+		ClientID:                 "rbrgnognrhongo3bi4gb9ghg9g",
+		CredentialSource:         &testBaseCredSource,
+		Scopes:                   []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+		WorkforcePoolUserProject: "myProject",
+	}
+
+	_, err := NewTokenSource(context.Background(), config)
+
+	if err == nil {
+		t.Fatalf("Expected error but found none")
+	}
+	if got, want := err.Error(), "oauth2/google/externalaccount: Workforce pool user project should not be set for non-workforce pool credentials"; got != want {
+		t.Errorf("Incorrect error received.\nExpected: %s\nReceived: %s", want, got)
+	}
+}
+
+func TestWorkforcePoolCreation(t *testing.T) {
+	var audienceValidityTests = []struct {
+		audience      string
+		expectSuccess bool
+	}{
+		{"//iam.googleapis.com/locations/global/workforcePools/pool-id/providers/provider-id", true},
+		{"//iam.googleapis.com/locations/eu/workforcePools/pool-id/providers/provider-id", true},
+		{"//iam.googleapis.com/locations/eu/workforcePools/workloadIdentityPools/providers/provider-id", true},
+		{"identitynamespace:1f12345:my_provider", false},
+		{"//iam.googleapis.com/projects/123456/locations/global/workloadIdentityPools/pool-id/providers/provider-id", false},
+		{"//iam.googleapis.com/projects/123456/locations/eu/workloadIdentityPools/pool-id/providers/provider-id", false},
+		{"//iam.googleapis.com/projects/123456/locations/global/workloadIdentityPools/workforcePools/providers/provider-id", false},
+		{"//iamgoogleapis.com/locations/eu/workforcePools/pool-id/providers/provider-id", false},
+		{"//iam.googleapiscom/locations/eu/workforcePools/pool-id/providers/provider-id", false},
+		{"//iam.googleapis.com/locations/workforcePools/pool-id/providers/provider-id", false},
+		{"//iam.googleapis.com/locations/eu/workforcePool/pool-id/providers/provider-id", false},
+		{"//iam.googleapis.com/locations//workforcePool/pool-id/providers/provider-id", false},
+	}
+
+	ctx := context.Background()
+	for _, tt := range audienceValidityTests {
+		t.Run(" "+tt.audience, func(t *testing.T) { // We prepend a space ahead of the test input when outputting for sake of readability.
+			config := testConfig
+			config.TokenURL = "https://sts.googleapis.com" // Setting the most basic acceptable tokenURL
+			config.ServiceAccountImpersonationURL = "https://iamcredentials.googleapis.com"
+			config.Audience = tt.audience
+			config.WorkforcePoolUserProject = "myProject"
+			_, err := NewTokenSource(ctx, config)
+
+			if tt.expectSuccess && err != nil {
+				t.Errorf("got %v but want nil", err)
+			} else if !tt.expectSuccess && err == nil {
+				t.Errorf("got nil but expected an error")
+			}
+		})
+	}
+}
+
+var impersonationTests = []struct {
+	name                      string
+	config                    Config
+	expectedImpersonationBody string
+	expectedMetricsHeader     string
+}{
+	{
+		name: "Base Impersonation",
+		config: Config{
+			Audience:         "32555940559.apps.googleusercontent.com",
+			SubjectTokenType: "urn:ietf:params:oauth:token-type:jwt",
+			TokenInfoURL:     "http://localhost:8080/v1/tokeninfo",
+			ClientSecret:     "notsosecret",
+			ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
+			CredentialSource: &testBaseCredSource,
+			Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+		},
+		expectedImpersonationBody: "{\"lifetime\":\"3600s\",\"scope\":[\"https://www.googleapis.com/auth/devstorage.full_control\"]}",
+		expectedMetricsHeader:     getExpectedMetricsHeader("file", true, false),
+	},
+	{
+		name: "With TokenLifetime Set",
+		config: Config{
+			Audience:         "32555940559.apps.googleusercontent.com",
+			SubjectTokenType: "urn:ietf:params:oauth:token-type:jwt",
+			TokenInfoURL:     "http://localhost:8080/v1/tokeninfo",
+			ClientSecret:     "notsosecret",
+			ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
+			CredentialSource: &testBaseCredSource,
+			Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+			ServiceAccountImpersonationLifetimeSeconds: 10000,
+		},
+		expectedImpersonationBody: "{\"lifetime\":\"10000s\",\"scope\":[\"https://www.googleapis.com/auth/devstorage.full_control\"]}",
+		expectedMetricsHeader:     getExpectedMetricsHeader("file", true, true),
+	},
+}
+
+func TestImpersonation(t *testing.T) {
+	for _, tt := range impersonationTests {
+		t.Run(tt.name, func(t *testing.T) {
+			testImpersonateConfig := tt.config
+			impersonateServer := createImpersonationServer("/", "Bearer Sample.Access.Token", tt.expectedImpersonationBody, baseImpersonateCredsRespBody, t)
+			defer impersonateServer.Close()
+			testImpersonateConfig.ServiceAccountImpersonationURL = impersonateServer.URL
+
+			targetServer := createTargetServer(tt.expectedMetricsHeader, t)
+			defer targetServer.Close()
+			testImpersonateConfig.TokenURL = targetServer.URL
+
+			ourTS, err := testImpersonateConfig.tokenSource(context.Background(), "http")
+			if err != nil {
+				t.Fatalf("Failed to create TokenSource: %v", err)
+			}
+
+			oldNow := now
+			defer func() { now = oldNow }()
+			now = testNow
+
+			tok, err := ourTS.Token()
+			if err != nil {
+				t.Fatalf("Unexpected error: %e", err)
+			}
+			if got, want := tok.AccessToken, "Second.Access.Token"; got != want {
+				t.Errorf("Unexpected access token: got %v, but wanted %v", got, want)
+			}
+			if got, want := tok.TokenType, "Bearer"; got != want {
+				t.Errorf("Unexpected TokenType: got %v, but wanted %v", got, want)
+			}
+		})
+	}
+}
+
+var newTokenTests = []struct {
+	name   string
+	config Config
+}{
+	{
+		name: "Missing Audience",
+		config: Config{
+			SubjectTokenType: "urn:ietf:params:oauth:token-type:jwt",
+			TokenInfoURL:     "http://localhost:8080/v1/tokeninfo",
+			ClientSecret:     "notsosecret",
+			ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
+			CredentialSource: &testBaseCredSource,
+			Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+			ServiceAccountImpersonationLifetimeSeconds: 10000,
+		},
+	},
+	{
+		name: "Missing Subject Token Type",
+		config: Config{
+			Audience:         "32555940559.apps.googleusercontent.com",
+			TokenInfoURL:     "http://localhost:8080/v1/tokeninfo",
+			ClientSecret:     "notsosecret",
+			ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
+			CredentialSource: &testBaseCredSource,
+			Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+			ServiceAccountImpersonationLifetimeSeconds: 10000,
+		},
+	},
+	{
+		name: "No Cred Source",
+		config: Config{
+			Audience:         "32555940559.apps.googleusercontent.com",
+			SubjectTokenType: "urn:ietf:params:oauth:token-type:jwt",
+			TokenInfoURL:     "http://localhost:8080/v1/tokeninfo",
+			ClientSecret:     "notsosecret",
+			ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
+			Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+			ServiceAccountImpersonationLifetimeSeconds: 10000,
+		},
+	},
+	{
+		name: "Cred Source and Supplier",
+		config: Config{
+			Audience:                       "32555940559.apps.googleusercontent.com",
+			SubjectTokenType:               "urn:ietf:params:oauth:token-type:jwt",
+			TokenInfoURL:                   "http://localhost:8080/v1/tokeninfo",
+			CredentialSource:               &testBaseCredSource,
+			AwsSecurityCredentialsSupplier: testAwsSupplier{},
+			ClientSecret:                   "notsosecret",
+			ClientID:                       "rbrgnognrhongo3bi4gb9ghg9g",
+			Scopes:                         []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+			ServiceAccountImpersonationLifetimeSeconds: 10000,
+		},
+	},
+}
+
+func TestNewToken(t *testing.T) {
+	for _, tt := range newTokenTests {
+		t.Run(tt.name, func(t *testing.T) {
+			testConfig := tt.config
+
+			_, err := NewTokenSource(context.Background(), testConfig)
+			if err == nil {
+				t.Fatalf("expected error when calling NewToken()")
+			}
+		})
+	}
+}
+
+func TestConfig_TokenURL(t *testing.T) {
+	tests := []struct {
+		tokenURL       string
+		universeDomain string
+		want           string
+	}{
+		{
+			tokenURL:       "https://sts.googleapis.com/v1/token",
+			universeDomain: "",
+			want:           "https://sts.googleapis.com/v1/token",
+		},
+		{
+			tokenURL:       "",
+			universeDomain: "",
+			want:           "https://sts.googleapis.com/v1/token",
+		},
+		{
+			tokenURL:       "",
+			universeDomain: "googleapis.com",
+			want:           "https://sts.googleapis.com/v1/token",
+		},
+		{
+			tokenURL:       "",
+			universeDomain: "example.com",
+			want:           "https://sts.example.com/v1/token",
+		},
+	}
+	for _, tt := range tests {
+		config := &Config{
+			Audience:         "//iam.googleapis.com/locations/eu/workforcePools/pool-id/providers/provider-id",
+			SubjectTokenType: "urn:ietf:params:oauth:token-type:id_token",
+			CredentialSource: &testBaseCredSource,
+			Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
+		}
+		config.TokenURL = tt.tokenURL
+		config.UniverseDomain = tt.universeDomain
+		config.parse(context.Background())
+		if got := config.TokenURL; got != tt.want {
+			t.Errorf("got %q, want %q", got, tt.want)
+		}
+	}
+}

google/externalaccount/executablecredsource.go

@@ -11,7 +11,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"regexp"
@@ -19,7 +18,7 @@ import (
 	"time"
 )
 
-var serviceAccountImpersonationRE = regexp.MustCompile("https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/(.*@.*):generateAccessToken")
+var serviceAccountImpersonationRE = regexp.MustCompile("https://iamcredentials\\..+/v1/projects/-/serviceAccounts/(.*@.*):generateAccessToken")
 
 const (
 	executableSupportedMaxVersion = 1
@@ -39,51 +38,51 @@ func (nce nonCacheableError) Error() string {
 }
 
 func missingFieldError(source, field string) error {
-	return fmt.Errorf("oauth2/google: %v missing `%q` field", source, field)
+	return fmt.Errorf("oauth2/google/externalaccount: %v missing `%q` field", source, field)
 }
 
 func jsonParsingError(source, data string) error {
-	return fmt.Errorf("oauth2/google: unable to parse %v\nResponse: %v", source, data)
+	return fmt.Errorf("oauth2/google/externalaccount: unable to parse %v\nResponse: %v", source, data)
 }
 
 func malformedFailureError() error {
-	return nonCacheableError{"oauth2/google: response must include `error` and `message` fields when unsuccessful"}
+	return nonCacheableError{"oauth2/google/externalaccount: response must include `error` and `message` fields when unsuccessful"}
 }
 
 func userDefinedError(code, message string) error {
-	return nonCacheableError{fmt.Sprintf("oauth2/google: response contains unsuccessful response: (%v) %v", code, message)}
+	return nonCacheableError{fmt.Sprintf("oauth2/google/externalaccount: response contains unsuccessful response: (%v) %v", code, message)}
 }
 
 func unsupportedVersionError(source string, version int) error {
-	return fmt.Errorf("oauth2/google: %v contains unsupported version: %v", source, version)
+	return fmt.Errorf("oauth2/google/externalaccount: %v contains unsupported version: %v", source, version)
 }
 
 func tokenExpiredError() error {
-	return nonCacheableError{"oauth2/google: the token returned by the executable is expired"}
+	return nonCacheableError{"oauth2/google/externalaccount: the token returned by the executable is expired"}
 }
 
 func tokenTypeError(source string) error {
-	return fmt.Errorf("oauth2/google: %v contains unsupported token type", source)
+	return fmt.Errorf("oauth2/google/externalaccount: %v contains unsupported token type", source)
 }
 
 func exitCodeError(exitCode int) error {
-	return fmt.Errorf("oauth2/google: executable command failed with exit code %v", exitCode)
+	return fmt.Errorf("oauth2/google/externalaccount: executable command failed with exit code %v", exitCode)
 }
 
 func executableError(err error) error {
-	return fmt.Errorf("oauth2/google: executable command failed: %v", err)
+	return fmt.Errorf("oauth2/google/externalaccount: executable command failed: %v", err)
 }
 
 func executablesDisallowedError() error {
-	return errors.New("oauth2/google: executables need to be explicitly allowed (set GOOGLE_EXTERNAL_ACCOUNT_ALLOW_EXECUTABLES to '1') to run")
+	return errors.New("oauth2/google/externalaccount: executables need to be explicitly allowed (set GOOGLE_EXTERNAL_ACCOUNT_ALLOW_EXECUTABLES to '1') to run")
 }
 
 func timeoutRangeError() error {
-	return errors.New("oauth2/google: invalid `timeout_millis` field — executable timeout must be between 5 and 120 seconds")
+	return errors.New("oauth2/google/externalaccount: invalid `timeout_millis` field — executable timeout must be between 5 and 120 seconds")
 }
 
 func commandMissingError() error {
-	return errors.New("oauth2/google: missing `command` field — executable command must be provided")
+	return errors.New("oauth2/google/externalaccount: missing `command` field — executable command must be provided")
 }
 
 type environment interface {
@@ -146,7 +145,7 @@ type executableCredentialSource struct {
 
 // CreateExecutableCredential creates an executableCredentialSource given an ExecutableConfig.
 // It also performs defaulting and type conversions.
-func CreateExecutableCredential(ctx context.Context, ec *ExecutableConfig, config *Config) (executableCredentialSource, error) {
+func createExecutableCredential(ctx context.Context, ec *ExecutableConfig, config *Config) (executableCredentialSource, error) {
 	if ec.Command == "" {
 		return executableCredentialSource{}, commandMissingError()
 	}
@@ -258,7 +257,7 @@ func (cs executableCredentialSource) getTokenFromOutputFile() (token string, err
 	}
 	defer file.Close()
 
-	data, err := ioutil.ReadAll(io.LimitReader(file, 1<<20))
+	data, err := io.ReadAll(io.LimitReader(file, 1<<20))
 	if err != nil || len(data) == 0 {
 		// Cachefile exists, but no data found. Get new credential.
 		return "", nil

google/externalaccount/executablecredsource_test.go

@@ -8,13 +8,10 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"os"
-	"sort"
+	"slices"
 	"testing"
 	"time"
-
-	"github.com/google/go-cmp/cmp"
 )
 
 type testEnvironment struct {
@@ -128,7 +125,7 @@ var creationTests = []struct {
 func TestCreateExecutableCredential(t *testing.T) {
 	for _, tt := range creationTests {
 		t.Run(tt.name, func(t *testing.T) {
-			ecs, err := CreateExecutableCredential(context.Background(), &tt.executableConfig, nil)
+			ecs, err := createExecutableCredential(context.Background(), &tt.executableConfig, nil)
 			if tt.expectedErr != nil {
 				if err == nil {
 					t.Fatalf("Expected error but found none")
@@ -169,7 +166,7 @@ var getEnvironmentTests = []struct {
 		config: Config{
 			Audience:         "//iam.googleapis.com/projects/123/locations/global/workloadIdentityPools/pool/providers/oidc",
 			SubjectTokenType: "urn:ietf:params:oauth:token-type:jwt",
-			CredentialSource: CredentialSource{
+			CredentialSource: &CredentialSource{
 				Executable: &ExecutableConfig{
 					Command: "blarg",
 				},
@@ -193,7 +190,7 @@ var getEnvironmentTests = []struct {
 			Audience:                       "//iam.googleapis.com/projects/123/locations/global/workloadIdentityPools/pool/providers/oidc",
 			ServiceAccountImpersonationURL: "https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/test@project.iam.gserviceaccount.com:generateAccessToken",
 			SubjectTokenType:               "urn:ietf:params:oauth:token-type:jwt",
-			CredentialSource: CredentialSource{
+			CredentialSource: &CredentialSource{
 				Executable: &ExecutableConfig{
 					Command:    "blarg",
 					OutputFile: "/path/to/generated/cached/credentials",
@@ -220,7 +217,7 @@ var getEnvironmentTests = []struct {
 			Audience:                       "//iam.googleapis.com/projects/123/locations/global/workloadIdentityPools/pool/providers/oidc",
 			ServiceAccountImpersonationURL: "test@project.iam.gserviceaccount.com",
 			SubjectTokenType:               "urn:ietf:params:oauth:token-type:jwt",
-			CredentialSource: CredentialSource{
+			CredentialSource: &CredentialSource{
 				Executable: &ExecutableConfig{
 					Command:    "blarg",
 					OutputFile: "/path/to/generated/cached/credentials",
@@ -247,21 +244,19 @@ func TestExecutableCredentialGetEnvironment(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			config := tt.config
 
-			ecs, err := CreateExecutableCredential(context.Background(), config.CredentialSource.Executable, &config)
+			ecs, err := createExecutableCredential(context.Background(), config.CredentialSource.Executable, &config)
 			if err != nil {
 				t.Fatalf("creation failed %v", err)
 			}
 
 			ecs.env = &tt.environment
 
-			// This Transformer sorts a []string.
-			sorter := cmp.Transformer("Sort", func(in []string) []string {
-				out := append([]string(nil), in...) // Copy input to avoid mutating it
-				sort.Strings(out)
-				return out
-			})
+			got := ecs.executableEnvironment()
+			slices.Sort(got)
+			want := tt.expectedEnvironment
+			slices.Sort(want)
 
-			if got, want := ecs.executableEnvironment(), tt.expectedEnvironment; !cmp.Equal(got, want, sorter) {
+			if !slices.Equal(got, want) {
 				t.Errorf("Incorrect environment received.\nReceived: %s\nExpected: %s", got, want)
 			}
 		})
@@ -471,7 +466,7 @@ func TestRetrieveExecutableSubjectTokenExecutableErrors(t *testing.T) {
 	}
 
 	tfc := testFileConfig
-	tfc.CredentialSource = cs
+	tfc.CredentialSource = &cs
 
 	base, err := tfc.parse(context.Background())
 	if err != nil {
@@ -578,7 +573,7 @@ func TestRetrieveExecutableSubjectTokenSuccesses(t *testing.T) {
 	}
 
 	tfc := testFileConfig
-	tfc.CredentialSource = cs
+	tfc.CredentialSource = &cs
 
 	base, err := tfc.parse(context.Background())
 	if err != nil {
@@ -614,7 +609,7 @@ func TestRetrieveExecutableSubjectTokenSuccesses(t *testing.T) {
 }
 
 func TestRetrieveOutputFileSubjectTokenNotJSON(t *testing.T) {
-	outputFile, err := ioutil.TempFile("testdata", "result.*.json")
+	outputFile, err := os.CreateTemp("testdata", "result.*.json")
 	if err != nil {
 		t.Fatalf("Tempfile failed: %v", err)
 	}
@@ -629,7 +624,7 @@ func TestRetrieveOutputFileSubjectTokenNotJSON(t *testing.T) {
 	}
 
 	tfc := testFileConfig
-	tfc.CredentialSource = cs
+	tfc.CredentialSource = &cs
 
 	base, err := tfc.parse(context.Background())
 	if err != nil {
@@ -654,7 +649,7 @@ func TestRetrieveOutputFileSubjectTokenNotJSON(t *testing.T) {
 	if _, err = base.subjectToken(); err == nil {
 		t.Fatalf("Expected error but found none")
 	} else if got, want := err.Error(), jsonParsingError(outputFileSource, "tokentokentoken").Error(); got != want {
-		t.Errorf("Incorrect error received.\nExpected: %s\nRecieved: %s", want, got)
+		t.Errorf("Incorrect error received.\nExpected: %s\nReceived: %s", want, got)
 	}
 
 	_, deadlineSet := te.getDeadline()
@@ -763,7 +758,7 @@ var cacheFailureTests = []struct {
 func TestRetrieveOutputFileSubjectTokenFailureTests(t *testing.T) {
 	for _, tt := range cacheFailureTests {
 		t.Run(tt.name, func(t *testing.T) {
-			outputFile, err := ioutil.TempFile("testdata", "result.*.json")
+			outputFile, err := os.CreateTemp("testdata", "result.*.json")
 			if err != nil {
 				t.Fatalf("Tempfile failed: %v", err)
 			}
@@ -778,7 +773,7 @@ func TestRetrieveOutputFileSubjectTokenFailureTests(t *testing.T) {
 			}
 
 			tfc := testFileConfig
-			tfc.CredentialSource = cs
+			tfc.CredentialSource = &cs
 
 			base, err := tfc.parse(context.Background())
 			if err != nil {
@@ -801,7 +796,7 @@ func TestRetrieveOutputFileSubjectTokenFailureTests(t *testing.T) {
 			if _, err = ecs.subjectToken(); err == nil {
 				t.Errorf("Expected error but found none")
 			} else if got, want := err.Error(), tt.expectedErr.Error(); got != want {
-				t.Errorf("Incorrect error received.\nExpected: %s\nRecieved: %s", want, got)
+				t.Errorf("Incorrect error received.\nExpected: %s\nReceived: %s", want, got)
 			}
 
 			if _, deadlineSet := te.getDeadline(); deadlineSet {
@@ -866,7 +861,7 @@ var invalidCacheTests = []struct {
 func TestRetrieveOutputFileSubjectTokenInvalidCache(t *testing.T) {
 	for _, tt := range invalidCacheTests {
 		t.Run(tt.name, func(t *testing.T) {
-			outputFile, err := ioutil.TempFile("testdata", "result.*.json")
+			outputFile, err := os.CreateTemp("testdata", "result.*.json")
 			if err != nil {
 				t.Fatalf("Tempfile failed: %v", err)
 			}
@@ -881,7 +876,7 @@ func TestRetrieveOutputFileSubjectTokenInvalidCache(t *testing.T) {
 			}
 
 			tfc := testFileConfig
-			tfc.CredentialSource = cs
+			tfc.CredentialSource = &cs
 
 			base, err := tfc.parse(context.Background())
 			if err != nil {
@@ -923,7 +918,7 @@ func TestRetrieveOutputFileSubjectTokenInvalidCache(t *testing.T) {
 			}
 
 			if got, want := out, "tokentokentoken"; got != want {
-				t.Errorf("Incorrect token received.\nExpected: %s\nRecieved: %s", want, got)
+				t.Errorf("Incorrect token received.\nExpected: %s\nReceived: %s", want, got)
 			}
 		})
 	}
@@ -970,8 +965,7 @@ var cacheSuccessTests = []struct {
 func TestRetrieveOutputFileSubjectTokenJwt(t *testing.T) {
 	for _, tt := range cacheSuccessTests {
 		t.Run(tt.name, func(t *testing.T) {
-
-			outputFile, err := ioutil.TempFile("testdata", "result.*.json")
+			outputFile, err := os.CreateTemp("testdata", "result.*.json")
 			if err != nil {
 				t.Fatalf("Tempfile failed: %v", err)
 			}
@@ -986,7 +980,7 @@ func TestRetrieveOutputFileSubjectTokenJwt(t *testing.T) {
 			}
 
 			tfc := testFileConfig
-			tfc.CredentialSource = cs
+			tfc.CredentialSource = &cs
 
 			base, err := tfc.parse(context.Background())
 			if err != nil {
@@ -1012,7 +1006,7 @@ func TestRetrieveOutputFileSubjectTokenJwt(t *testing.T) {
 			if out, err := ecs.subjectToken(); err != nil {
 				t.Errorf("retrieveSubjectToken() failed: %v", err)
 			} else if got, want := out, "tokentokentoken"; got != want {
-				t.Errorf("Incorrect token received.\nExpected: %s\nRecieved: %s", want, got)
+				t.Errorf("Incorrect token received.\nExpected: %s\nReceived: %s", want, got)
 			}
 
 			if _, deadlineSet := te.getDeadline(); deadlineSet {
@@ -1021,3 +1015,37 @@ func TestRetrieveOutputFileSubjectTokenJwt(t *testing.T) {
 		})
 	}
 }
+
+func TestServiceAccountImpersonationRE(t *testing.T) {
+	tests := []struct {
+		name                           string
+		serviceAccountImpersonationURL string
+		want                           string
+	}{
+		{
+			name:                           "universe domain Google Default Universe (GDU) googleapis.com",
+			serviceAccountImpersonationURL: "https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/test@project.iam.gserviceaccount.com:generateAccessToken",
+			want:                           "test@project.iam.gserviceaccount.com",
+		},
+		{
+			name:                           "email does not match",
+			serviceAccountImpersonationURL: "test@project.iam.gserviceaccount.com",
+			want:                           "",
+		},
+		{
+			name:                           "universe domain non-GDU",
+			serviceAccountImpersonationURL: "https://iamcredentials.apis-tpclp.goog/v1/projects/-/serviceAccounts/test@project.iam.gserviceaccount.com:generateAccessToken",
+			want:                           "test@project.iam.gserviceaccount.com",
+		},
+	}
+	for _, tt := range tests {
+		matches := serviceAccountImpersonationRE.FindStringSubmatch(tt.serviceAccountImpersonationURL)
+		if matches == nil {
+			if tt.want != "" {
+				t.Errorf("%q: got nil, want %q", tt.name, tt.want)
+			}
+		} else if matches[1] != tt.want {
+			t.Errorf("%q: got %q, want %q", tt.name, matches[1], tt.want)
+		}
+	}
+}

google/externalaccount/filecredsource.go

@@ -10,13 +10,12 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 )
 
 type fileCredentialSource struct {
 	File   string
-	Format format
+	Format Format
 }
 
 func (cs fileCredentialSource) credentialSourceType() string {
@@ -26,28 +25,28 @@ func (cs fileCredentialSource) credentialSourceType() string {
 func (cs fileCredentialSource) subjectToken() (string, error) {
 	tokenFile, err := os.Open(cs.File)
 	if err != nil {
-		return "", fmt.Errorf("oauth2/google: failed to open credential file %q", cs.File)
+		return "", fmt.Errorf("oauth2/google/externalaccount: failed to open credential file %q", cs.File)
 	}
 	defer tokenFile.Close()
-	tokenBytes, err := ioutil.ReadAll(io.LimitReader(tokenFile, 1<<20))
+	tokenBytes, err := io.ReadAll(io.LimitReader(tokenFile, 1<<20))
 	if err != nil {
-		return "", fmt.Errorf("oauth2/google: failed to read credential file: %v", err)
+		return "", fmt.Errorf("oauth2/google/externalaccount: failed to read credential file: %v", err)
 	}
 	tokenBytes = bytes.TrimSpace(tokenBytes)
 	switch cs.Format.Type {
 	case "json":
-		jsonData := make(map[string]interface{})
+		jsonData := make(map[string]any)
 		err = json.Unmarshal(tokenBytes, &jsonData)
 		if err != nil {
-			return "", fmt.Errorf("oauth2/google: failed to unmarshal subject token file: %v", err)
+			return "", fmt.Errorf("oauth2/google/externalaccount: failed to unmarshal subject token file: %v", err)
 		}
 		val, ok := jsonData[cs.Format.SubjectTokenFieldName]
 		if !ok {
-			return "", errors.New("oauth2/google: provided subject_token_field_name not found in credentials")
+			return "", errors.New("oauth2/google/externalaccount: provided subject_token_field_name not found in credentials")
 		}
 		token, ok := val.(string)
 		if !ok {
-			return "", errors.New("oauth2/google: improperly formatted subject token")
+			return "", errors.New("oauth2/google/externalaccount: improperly formatted subject token")
 		}
 		return token, nil
 	case "text":
@@ -55,7 +54,7 @@ func (cs fileCredentialSource) subjectToken() (string, error) {
 	case "":
 		return string(tokenBytes), nil
 	default:
-		return "", errors.New("oauth2/google: invalid credential_source file format type")
+		return "", errors.New("oauth2/google/externalaccount: invalid credential_source file format type")
 	}
 
 }

google/externalaccount/filecredsource_test.go

@@ -36,7 +36,7 @@ func TestRetrieveFileSubjectToken(t *testing.T) {
 			name: "TextFileSource",
 			cs: CredentialSource{
 				File:   textBaseCredPath,
-				Format: format{Type: fileTypeText},
+				Format: Format{Type: fileTypeText},
 			},
 			want: "street123",
 		},
@@ -44,7 +44,7 @@ func TestRetrieveFileSubjectToken(t *testing.T) {
 			name: "JSONFileSource",
 			cs: CredentialSource{
 				File:   jsonBaseCredPath,
-				Format: format{Type: fileTypeJSON, SubjectTokenFieldName: "SubjToken"},
+				Format: Format{Type: fileTypeJSON, SubjectTokenFieldName: "SubjToken"},
 			},
 			want: "321road",
 		},
@@ -53,7 +53,7 @@ func TestRetrieveFileSubjectToken(t *testing.T) {
 	for _, test := range fileSourceTests {
 		test := test
 		tfc := testFileConfig
-		tfc.CredentialSource = test.cs
+		tfc.CredentialSource = &test.cs
 
 		t.Run(test.name, func(t *testing.T) {
 			base, err := tfc.parse(context.Background())

google/externalaccount/header_test.go

@@ -7,8 +7,6 @@ package externalaccount
 import (
 	"runtime"
 	"testing"
-
-	"github.com/google/go-cmp/cmp"
 )
 
 func TestGoVersion(t *testing.T) {
@@ -40,8 +38,8 @@ func TestGoVersion(t *testing.T) {
 	} {
 		version = tst.v
 		got := goVersion()
-		if diff := cmp.Diff(got, tst.want); diff != "" {
-			t.Errorf("got(-),want(+):\n%s", diff)
+		if got != tst.want {
+			t.Errorf("go version = %q, want = %q", got, tst.want)
 		}
 	}
 	version = runtime.Version

google/externalaccount/programmaticrefreshcredsource.go

@@ -0,0 +1,21 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package externalaccount
+
+import "context"
+
+type programmaticRefreshCredentialSource struct {
+	supplierOptions      SupplierOptions
+	subjectTokenSupplier SubjectTokenSupplier
+	ctx                  context.Context
+}
+
+func (cs programmaticRefreshCredentialSource) credentialSourceType() string {
+	return "programmatic"
+}
+
+func (cs programmaticRefreshCredentialSource) subjectToken() (string, error) {
+	return cs.subjectTokenSupplier.SubjectToken(cs.ctx, cs.supplierOptions)
+}

google/externalaccount/programmaticrefreshcredsource_test.go

@@ -0,0 +1,122 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package externalaccount
+
+import (
+	"context"
+	"errors"
+	"testing"
+)
+
+func TestRetrieveSubjectToken_ProgrammaticAuth(t *testing.T) {
+	tfc := testConfig
+
+	tfc.SubjectTokenSupplier = testSubjectTokenSupplier{
+		subjectToken: "subjectToken",
+	}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	out, err := base.subjectToken()
+	if err != nil {
+		t.Fatalf("retrieveSubjectToken() failed: %v", err)
+	}
+
+	if out != "subjectToken" {
+		t.Errorf("subjectToken = \n%q\n want \nSubjectToken", out)
+	}
+}
+
+func TestRetrieveSubjectToken_ProgrammaticAuthFails(t *testing.T) {
+	tfc := testConfig
+	testError := errors.New("test error")
+
+	tfc.SubjectTokenSupplier = testSubjectTokenSupplier{
+		err: testError,
+	}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	_, err = base.subjectToken()
+	if err == nil {
+		t.Fatalf("subjectToken() should have failed")
+	}
+	if testError != err {
+		t.Errorf("subjectToken = %e, want %e", err, testError)
+	}
+}
+
+func TestRetrieveSubjectToken_ProgrammaticAuthOptions(t *testing.T) {
+	tfc := testConfig
+	expectedOptions := SupplierOptions{Audience: tfc.Audience, SubjectTokenType: tfc.SubjectTokenType}
+
+	tfc.SubjectTokenSupplier = testSubjectTokenSupplier{
+		subjectToken:    "subjectToken",
+		expectedOptions: &expectedOptions,
+	}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	_, err = base.subjectToken()
+	if err != nil {
+		t.Fatalf("retrieveSubjectToken() failed: %v", err)
+	}
+}
+
+func TestRetrieveSubjectToken_ProgrammaticAuthContext(t *testing.T) {
+	tfc := testConfig
+	ctx := context.Background()
+
+	tfc.SubjectTokenSupplier = testSubjectTokenSupplier{
+		subjectToken:    "subjectToken",
+		expectedContext: ctx,
+	}
+
+	base, err := tfc.parse(ctx)
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	_, err = base.subjectToken()
+	if err != nil {
+		t.Fatalf("retrieveSubjectToken() failed: %v", err)
+	}
+}
+
+type testSubjectTokenSupplier struct {
+	err             error
+	subjectToken    string
+	expectedOptions *SupplierOptions
+	expectedContext context.Context
+}
+
+func (supp testSubjectTokenSupplier) SubjectToken(ctx context.Context, options SupplierOptions) (string, error) {
+	if supp.err != nil {
+		return "", supp.err
+	}
+	if supp.expectedOptions != nil {
+		if supp.expectedOptions.Audience != options.Audience {
+			return "", errors.New("Audience does not match")
+		}
+		if supp.expectedOptions.SubjectTokenType != options.SubjectTokenType {
+			return "", errors.New("Audience does not match")
+		}
+	}
+	if supp.expectedContext != nil {
+		if supp.expectedContext != ctx {
+			return "", errors.New("Context does not match")
+		}
+	}
+	return supp.subjectToken, nil
+}

google/externalaccount/urlcredsource.go

@@ -10,7 +10,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 
 	"golang.org/x/oauth2"
@@ -19,7 +18,7 @@ import (
 type urlCredentialSource struct {
 	URL     string
 	Headers map[string]string
-	Format  format
+	Format  Format
 	ctx     context.Context
 }
 
@@ -31,7 +30,7 @@ func (cs urlCredentialSource) subjectToken() (string, error) {
 	client := oauth2.NewClient(cs.ctx, nil)
 	req, err := http.NewRequest("GET", cs.URL, nil)
 	if err != nil {
-		return "", fmt.Errorf("oauth2/google: HTTP request for URL-sourced credential failed: %v", err)
+		return "", fmt.Errorf("oauth2/google/externalaccount: HTTP request for URL-sourced credential failed: %v", err)
 	}
 	req = req.WithContext(cs.ctx)
 
@@ -40,32 +39,32 @@ func (cs urlCredentialSource) subjectToken() (string, error) {
 	}
 	resp, err := client.Do(req)
 	if err != nil {
-		return "", fmt.Errorf("oauth2/google: invalid response when retrieving subject token: %v", err)
+		return "", fmt.Errorf("oauth2/google/externalaccount: invalid response when retrieving subject token: %v", err)
 	}
 	defer resp.Body.Close()
 
-	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
-		return "", fmt.Errorf("oauth2/google: invalid body in subject token URL query: %v", err)
+		return "", fmt.Errorf("oauth2/google/externalaccount: invalid body in subject token URL query: %v", err)
 	}
 	if c := resp.StatusCode; c < 200 || c > 299 {
-		return "", fmt.Errorf("oauth2/google: status code %d: %s", c, respBody)
+		return "", fmt.Errorf("oauth2/google/externalaccount: status code %d: %s", c, respBody)
 	}
 
 	switch cs.Format.Type {
 	case "json":
-		jsonData := make(map[string]interface{})
+		jsonData := make(map[string]any)
 		err = json.Unmarshal(respBody, &jsonData)
 		if err != nil {
-			return "", fmt.Errorf("oauth2/google: failed to unmarshal subject token file: %v", err)
+			return "", fmt.Errorf("oauth2/google/externalaccount: failed to unmarshal subject token file: %v", err)
 		}
 		val, ok := jsonData[cs.Format.SubjectTokenFieldName]
 		if !ok {
-			return "", errors.New("oauth2/google: provided subject_token_field_name not found in credentials")
+			return "", errors.New("oauth2/google/externalaccount: provided subject_token_field_name not found in credentials")
 		}
 		token, ok := val.(string)
 		if !ok {
-			return "", errors.New("oauth2/google: improperly formatted subject token")
+			return "", errors.New("oauth2/google/externalaccount: improperly formatted subject token")
 		}
 		return token, nil
 	case "text":
@@ -73,7 +72,7 @@ func (cs urlCredentialSource) subjectToken() (string, error) {
 	case "":
 		return string(respBody), nil
 	default:
-		return "", errors.New("oauth2/google: invalid credential_source file format type")
+		return "", errors.New("oauth2/google/externalaccount: invalid credential_source file format type")
 	}
 
 }

google/externalaccount/urlcredsource_test.go

@@ -28,11 +28,11 @@ func TestRetrieveURLSubjectToken_Text(t *testing.T) {
 	heads["Metadata"] = "True"
 	cs := CredentialSource{
 		URL:     ts.URL,
-		Format:  format{Type: fileTypeText},
+		Format:  Format{Type: fileTypeText},
 		Headers: heads,
 	}
 	tfc := testFileConfig
-	tfc.CredentialSource = cs
+	tfc.CredentialSource = &cs
 
 	base, err := tfc.parse(context.Background())
 	if err != nil {
@@ -60,7 +60,7 @@ func TestRetrieveURLSubjectToken_Untyped(t *testing.T) {
 		URL: ts.URL,
 	}
 	tfc := testFileConfig
-	tfc.CredentialSource = cs
+	tfc.CredentialSource = &cs
 
 	base, err := tfc.parse(context.Background())
 	if err != nil {
@@ -93,10 +93,10 @@ func TestRetrieveURLSubjectToken_JSON(t *testing.T) {
 	}))
 	cs := CredentialSource{
 		URL:    ts.URL,
-		Format: format{Type: fileTypeJSON, SubjectTokenFieldName: "SubjToken"},
+		Format: Format{Type: fileTypeJSON, SubjectTokenFieldName: "SubjToken"},
 	}
 	tfc := testFileConfig
-	tfc.CredentialSource = cs
+	tfc.CredentialSource = &cs
 
 	base, err := tfc.parse(context.Background())
 	if err != nil {
@@ -115,10 +115,10 @@ func TestRetrieveURLSubjectToken_JSON(t *testing.T) {
 func TestURLCredential_CredentialSourceType(t *testing.T) {
 	cs := CredentialSource{
 		URL:    "http://example.com",
-		Format: format{Type: fileTypeText},
+		Format: Format{Type: fileTypeText},
 	}
 	tfc := testFileConfig
-	tfc.CredentialSource = cs
+	tfc.CredentialSource = &cs
 
 	base, err := tfc.parse(context.Background())
 	if err != nil {

google/google.go

@@ -15,8 +15,9 @@ import (
 
 	"cloud.google.com/go/compute/metadata"
 	"golang.org/x/oauth2"
-	"golang.org/x/oauth2/google/internal/externalaccount"
+	"golang.org/x/oauth2/google/externalaccount"
 	"golang.org/x/oauth2/google/internal/externalaccountauthorizeduser"
+	"golang.org/x/oauth2/google/internal/impersonate"
 	"golang.org/x/oauth2/jwt"
 )
 
@@ -200,12 +201,12 @@ func (f *credentialsFile) tokenSource(ctx context.Context, params CredentialsPar
 			ServiceAccountImpersonationLifetimeSeconds: f.ServiceAccountImpersonation.TokenLifetimeSeconds,
 			ClientSecret:             f.ClientSecret,
 			ClientID:                 f.ClientID,
-			CredentialSource:         f.CredentialSource,
+			CredentialSource:         &f.CredentialSource,
 			QuotaProjectID:           f.QuotaProjectID,
 			Scopes:                   params.Scopes,
 			WorkforcePoolUserProject: f.WorkforcePoolUserProject,
 		}
-		return cfg.TokenSource(ctx)
+		return externalaccount.NewTokenSource(ctx, *cfg)
 	case externalAccountAuthorizedUserKey:
 		cfg := &externalaccountauthorizeduser.Config{
 			Audience:       f.Audience,
@@ -228,7 +229,7 @@ func (f *credentialsFile) tokenSource(ctx context.Context, params CredentialsPar
 		if err != nil {
 			return nil, err
 		}
-		imp := externalaccount.ImpersonateTokenSource{
+		imp := impersonate.ImpersonateTokenSource{
 			Ctx:       ctx,
 			URL:       f.ServiceAccountImpersonationURL,
 			Scopes:    params.Scopes,
@@ -251,7 +252,10 @@ func (f *credentialsFile) tokenSource(ctx context.Context, params CredentialsPar
 // Further information about retrieving access tokens from the GCE metadata
 // server can be found at https://cloud.google.com/compute/docs/authentication.
 func ComputeTokenSource(account string, scope ...string) oauth2.TokenSource {
-	return computeTokenSource(account, 0, scope...)
+	// refresh 3 minutes and 45 seconds early. The shortest MDS cache is currently 4 minutes, so any
+	// refreshes earlier are a waste of compute.
+	earlyExpirySecs := 225 * time.Second
+	return computeTokenSource(account, earlyExpirySecs, scope...)
 }
 
 func computeTokenSource(account string, earlyExpiry time.Duration, scope ...string) oauth2.TokenSource {
@@ -281,27 +285,23 @@ func (cs computeSource) Token() (*oauth2.Token, error) {
 	if err != nil {
 		return nil, err
 	}
-	var res struct {
-		AccessToken  string `json:"access_token"`
-		ExpiresInSec int    `json:"expires_in"`
-		TokenType    string `json:"token_type"`
-	}
+	var res oauth2.Token
 	err = json.NewDecoder(strings.NewReader(tokenJSON)).Decode(&res)
 	if err != nil {
 		return nil, fmt.Errorf("oauth2/google: invalid token JSON from metadata: %v", err)
 	}
-	if res.ExpiresInSec == 0 || res.AccessToken == "" {
+	if res.ExpiresIn == 0 || res.AccessToken == "" {
 		return nil, fmt.Errorf("oauth2/google: incomplete token received from metadata")
 	}
 	tok := &oauth2.Token{
 		AccessToken: res.AccessToken,
 		TokenType:   res.TokenType,
-		Expiry:      time.Now().Add(time.Duration(res.ExpiresInSec) * time.Second),
+		Expiry:      time.Now().Add(time.Duration(res.ExpiresIn) * time.Second),
 	}
 	// NOTE(cbro): add hidden metadata about where the token is from.
 	// This is needed for detection by client libraries to know that credentials come from the metadata server.
 	// This may be removed in a future version of this library.
-	return tok.WithExtra(map[string]interface{}{
+	return tok.WithExtra(map[string]any{
 		"oauth2.google.tokenSource":    "compute-metadata",
 		"oauth2.google.serviceAccount": acct,
 	}), nil

google/google_test.go

@@ -5,6 +5,8 @@
 package google
 
 import (
+	"net/http"
+	"net/http/httptest"
 	"strings"
 	"testing"
 )
@@ -70,7 +72,7 @@ func TestConfigFromJSON(t *testing.T) {
 		t.Errorf("ClientSecret = %q; want %q", got, want)
 	}
 	if got, want := conf.RedirectURL, "https://www.example.com/oauth2callback"; got != want {
-		t.Errorf("RedictURL = %q; want %q", got, want)
+		t.Errorf("RedirectURL = %q; want %q", got, want)
 	}
 	if got, want := strings.Join(conf.Scopes, ","), "scope1,scope2"; got != want {
 		t.Errorf("Scopes = %q; want %q", got, want)
@@ -137,3 +139,21 @@ func TestJWTConfigFromJSONNoAudience(t *testing.T) {
 		t.Errorf("Audience = %q; want %q", got, want)
 	}
 }
+
+func TestComputeTokenSource(t *testing.T) {
+	tokenPath := "/computeMetadata/v1/instance/service-accounts/default/token"
+	tokenResponseBody := `{"access_token":"Sample.Access.Token","token_type":"Bearer","expires_in":3600}`
+	s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != tokenPath {
+			t.Errorf("got %s, want %s", r.URL.Path, tokenPath)
+		}
+		w.Write([]byte(tokenResponseBody))
+	}))
+	defer s.Close()
+	t.Setenv("GCE_METADATA_HOST", strings.TrimPrefix(s.URL, "http://"))
+	ts := ComputeTokenSource("")
+	_, err := ts.Token()
+	if err != nil {
+		t.Errorf("ts.Token() = %v", err)
+	}
+}

google/internal/externalaccount/basecredentials.go

@@ -1,254 +0,0 @@
-// Copyright 2020 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package externalaccount
-
-import (
-	"context"
-	"fmt"
-	"net/http"
-	"regexp"
-	"strconv"
-	"time"
-
-	"golang.org/x/oauth2"
-	"golang.org/x/oauth2/google/internal/stsexchange"
-)
-
-// now aliases time.Now for testing
-var now = func() time.Time {
-	return time.Now().UTC()
-}
-
-// Config stores the configuration for fetching tokens with external credentials.
-type Config struct {
-	// Audience is the Secure Token Service (STS) audience which contains the resource name for the workload
-	// identity pool or the workforce pool and the provider identifier in that pool.
-	Audience string
-	// SubjectTokenType is the STS token type based on the Oauth2.0 token exchange spec
-	// e.g. `urn:ietf:params:oauth:token-type:jwt`.
-	SubjectTokenType string
-	// TokenURL is the STS token exchange endpoint.
-	TokenURL string
-	// TokenInfoURL is the token_info endpoint used to retrieve the account related information (
-	// user attributes like account identifier, eg. email, username, uid, etc). This is
-	// needed for gCloud session account identification.
-	TokenInfoURL string
-	// ServiceAccountImpersonationURL is the URL for the service account impersonation request. This is only
-	// required for workload identity pools when APIs to be accessed have not integrated with UberMint.
-	ServiceAccountImpersonationURL string
-	// ServiceAccountImpersonationLifetimeSeconds is the number of seconds the service account impersonation
-	// token will be valid for.
-	ServiceAccountImpersonationLifetimeSeconds int
-	// ClientSecret is currently only required if token_info endpoint also
-	// needs to be called with the generated GCP access token. When provided, STS will be
-	// called with additional basic authentication using client_id as username and client_secret as password.
-	ClientSecret string
-	// ClientID is only required in conjunction with ClientSecret, as described above.
-	ClientID string
-	// CredentialSource contains the necessary information to retrieve the token itself, as well
-	// as some environmental information.
-	CredentialSource CredentialSource
-	// QuotaProjectID is injected by gCloud. If the value is non-empty, the Auth libraries
-	// will set the x-goog-user-project which overrides the project associated with the credentials.
-	QuotaProjectID string
-	// Scopes contains the desired scopes for the returned access token.
-	Scopes []string
-	// The optional workforce pool user project number when the credential
-	// corresponds to a workforce pool and not a workload identity pool.
-	// The underlying principal must still have serviceusage.services.use IAM
-	// permission to use the project for billing/quota.
-	WorkforcePoolUserProject string
-}
-
-var (
-	validWorkforceAudiencePattern *regexp.Regexp = regexp.MustCompile(`//iam\.googleapis\.com/locations/[^/]+/workforcePools/`)
-)
-
-func validateWorkforceAudience(input string) bool {
-	return validWorkforceAudiencePattern.MatchString(input)
-}
-
-// TokenSource Returns an external account TokenSource struct. This is to be called by package google to construct a google.Credentials.
-func (c *Config) TokenSource(ctx context.Context) (oauth2.TokenSource, error) {
-	return c.tokenSource(ctx, "https")
-}
-
-// tokenSource is a private function that's directly called by some of the tests,
-// because the unit test URLs are mocked, and would otherwise fail the
-// validity check.
-func (c *Config) tokenSource(ctx context.Context, scheme string) (oauth2.TokenSource, error) {
-	if c.WorkforcePoolUserProject != "" {
-		valid := validateWorkforceAudience(c.Audience)
-		if !valid {
-			return nil, fmt.Errorf("oauth2/google: workforce_pool_user_project should not be set for non-workforce pool credentials")
-		}
-	}
-
-	ts := tokenSource{
-		ctx:  ctx,
-		conf: c,
-	}
-	if c.ServiceAccountImpersonationURL == "" {
-		return oauth2.ReuseTokenSource(nil, ts), nil
-	}
-	scopes := c.Scopes
-	ts.conf.Scopes = []string{"https://www.googleapis.com/auth/cloud-platform"}
-	imp := ImpersonateTokenSource{
-		Ctx:                  ctx,
-		URL:                  c.ServiceAccountImpersonationURL,
-		Scopes:               scopes,
-		Ts:                   oauth2.ReuseTokenSource(nil, ts),
-		TokenLifetimeSeconds: c.ServiceAccountImpersonationLifetimeSeconds,
-	}
-	return oauth2.ReuseTokenSource(nil, imp), nil
-}
-
-// Subject token file types.
-const (
-	fileTypeText = "text"
-	fileTypeJSON = "json"
-)
-
-type format struct {
-	// Type is either "text" or "json". When not provided "text" type is assumed.
-	Type string `json:"type"`
-	// SubjectTokenFieldName is only required for JSON format. This would be "access_token" for azure.
-	SubjectTokenFieldName string `json:"subject_token_field_name"`
-}
-
-// CredentialSource stores the information necessary to retrieve the credentials for the STS exchange.
-// One field amongst File, URL, and Executable should be filled, depending on the kind of credential in question.
-// The EnvironmentID should start with AWS if being used for an AWS credential.
-type CredentialSource struct {
-	File string `json:"file"`
-
-	URL     string            `json:"url"`
-	Headers map[string]string `json:"headers"`
-
-	Executable *ExecutableConfig `json:"executable"`
-
-	EnvironmentID               string `json:"environment_id"`
-	RegionURL                   string `json:"region_url"`
-	RegionalCredVerificationURL string `json:"regional_cred_verification_url"`
-	CredVerificationURL         string `json:"cred_verification_url"`
-	IMDSv2SessionTokenURL       string `json:"imdsv2_session_token_url"`
-	Format                      format `json:"format"`
-}
-
-type ExecutableConfig struct {
-	Command       string `json:"command"`
-	TimeoutMillis *int   `json:"timeout_millis"`
-	OutputFile    string `json:"output_file"`
-}
-
-// parse determines the type of CredentialSource needed.
-func (c *Config) parse(ctx context.Context) (baseCredentialSource, error) {
-	if len(c.CredentialSource.EnvironmentID) > 3 && c.CredentialSource.EnvironmentID[:3] == "aws" {
-		if awsVersion, err := strconv.Atoi(c.CredentialSource.EnvironmentID[3:]); err == nil {
-			if awsVersion != 1 {
-				return nil, fmt.Errorf("oauth2/google: aws version '%d' is not supported in the current build", awsVersion)
-			}
-
-			awsCredSource := awsCredentialSource{
-				EnvironmentID:               c.CredentialSource.EnvironmentID,
-				RegionURL:                   c.CredentialSource.RegionURL,
-				RegionalCredVerificationURL: c.CredentialSource.RegionalCredVerificationURL,
-				CredVerificationURL:         c.CredentialSource.URL,
-				TargetResource:              c.Audience,
-				ctx:                         ctx,
-			}
-			if c.CredentialSource.IMDSv2SessionTokenURL != "" {
-				awsCredSource.IMDSv2SessionTokenURL = c.CredentialSource.IMDSv2SessionTokenURL
-			}
-
-			return awsCredSource, nil
-		}
-	} else if c.CredentialSource.File != "" {
-		return fileCredentialSource{File: c.CredentialSource.File, Format: c.CredentialSource.Format}, nil
-	} else if c.CredentialSource.URL != "" {
-		return urlCredentialSource{URL: c.CredentialSource.URL, Headers: c.CredentialSource.Headers, Format: c.CredentialSource.Format, ctx: ctx}, nil
-	} else if c.CredentialSource.Executable != nil {
-		return CreateExecutableCredential(ctx, c.CredentialSource.Executable, c)
-	}
-	return nil, fmt.Errorf("oauth2/google: unable to parse credential source")
-}
-
-type baseCredentialSource interface {
-	credentialSourceType() string
-	subjectToken() (string, error)
-}
-
-// tokenSource is the source that handles external credentials. It is used to retrieve Tokens.
-type tokenSource struct {
-	ctx  context.Context
-	conf *Config
-}
-
-func getMetricsHeaderValue(conf *Config, credSource baseCredentialSource) string {
-	return fmt.Sprintf("gl-go/%s auth/%s google-byoid-sdk source/%s sa-impersonation/%t config-lifetime/%t",
-		goVersion(),
-		"unknown",
-		credSource.credentialSourceType(),
-		conf.ServiceAccountImpersonationURL != "",
-		conf.ServiceAccountImpersonationLifetimeSeconds != 0)
-}
-
-// Token allows tokenSource to conform to the oauth2.TokenSource interface.
-func (ts tokenSource) Token() (*oauth2.Token, error) {
-	conf := ts.conf
-
-	credSource, err := conf.parse(ts.ctx)
-	if err != nil {
-		return nil, err
-	}
-	subjectToken, err := credSource.subjectToken()
-
-	if err != nil {
-		return nil, err
-	}
-	stsRequest := stsexchange.TokenExchangeRequest{
-		GrantType:          "urn:ietf:params:oauth:grant-type:token-exchange",
-		Audience:           conf.Audience,
-		Scope:              conf.Scopes,
-		RequestedTokenType: "urn:ietf:params:oauth:token-type:access_token",
-		SubjectToken:       subjectToken,
-		SubjectTokenType:   conf.SubjectTokenType,
-	}
-	header := make(http.Header)
-	header.Add("Content-Type", "application/x-www-form-urlencoded")
-	header.Add("x-goog-api-client", getMetricsHeaderValue(conf, credSource))
-	clientAuth := stsexchange.ClientAuthentication{
-		AuthStyle:    oauth2.AuthStyleInHeader,
-		ClientID:     conf.ClientID,
-		ClientSecret: conf.ClientSecret,
-	}
-	var options map[string]interface{}
-	// Do not pass workforce_pool_user_project when client authentication is used.
-	// The client ID is sufficient for determining the user project.
-	if conf.WorkforcePoolUserProject != "" && conf.ClientID == "" {
-		options = map[string]interface{}{
-			"userProject": conf.WorkforcePoolUserProject,
-		}
-	}
-	stsResp, err := stsexchange.ExchangeToken(ts.ctx, conf.TokenURL, &stsRequest, clientAuth, header, options)
-	if err != nil {
-		return nil, err
-	}
-
-	accessToken := &oauth2.Token{
-		AccessToken: stsResp.AccessToken,
-		TokenType:   stsResp.TokenType,
-	}
-	if stsResp.ExpiresIn < 0 {
-		return nil, fmt.Errorf("oauth2/google: got invalid expiry from security token service")
-	} else if stsResp.ExpiresIn >= 0 {
-		accessToken.Expiry = now().Add(time.Duration(stsResp.ExpiresIn) * time.Second)
-	}
-
-	if stsResp.RefreshToken != "" {
-		accessToken.RefreshToken = stsResp.RefreshToken
-	}
-	return accessToken, nil
-}

google/internal/externalaccount/basecredentials_test.go

@@ -1,259 +0,0 @@
-// Copyright 2020 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package externalaccount
-
-import (
-	"context"
-	"fmt"
-	"io/ioutil"
-	"net/http"
-	"net/http/httptest"
-	"testing"
-	"time"
-
-	"golang.org/x/oauth2"
-)
-
-const (
-	textBaseCredPath = "testdata/3pi_cred.txt"
-	jsonBaseCredPath = "testdata/3pi_cred.json"
-)
-
-var testBaseCredSource = CredentialSource{
-	File:   textBaseCredPath,
-	Format: format{Type: fileTypeText},
-}
-
-var testConfig = Config{
-	Audience:         "32555940559.apps.googleusercontent.com",
-	SubjectTokenType: "urn:ietf:params:oauth:token-type:jwt",
-	TokenInfoURL:     "http://localhost:8080/v1/tokeninfo",
-	ClientSecret:     "notsosecret",
-	ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
-	CredentialSource: testBaseCredSource,
-	Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
-}
-
-var (
-	baseCredsRequestBody                          = "audience=32555940559.apps.googleusercontent.com&grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange&requested_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fdevstorage.full_control&subject_token=street123&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aid_token"
-	baseCredsResponseBody                         = `{"access_token":"Sample.Access.Token","issued_token_type":"urn:ietf:params:oauth:token-type:access_token","token_type":"Bearer","expires_in":3600,"scope":"https://www.googleapis.com/auth/cloud-platform"}`
-	workforcePoolRequestBodyWithClientId          = "audience=%2F%2Fiam.googleapis.com%2Flocations%2Feu%2FworkforcePools%2Fpool-id%2Fproviders%2Fprovider-id&grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange&requested_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fdevstorage.full_control&subject_token=street123&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aid_token"
-	workforcePoolRequestBodyWithoutClientId       = "audience=%2F%2Fiam.googleapis.com%2Flocations%2Feu%2FworkforcePools%2Fpool-id%2Fproviders%2Fprovider-id&grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange&options=%7B%22userProject%22%3A%22myProject%22%7D&requested_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fdevstorage.full_control&subject_token=street123&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aid_token"
-	correctAT                                     = "Sample.Access.Token"
-	expiry                                  int64 = 234852
-)
-var (
-	testNow = func() time.Time { return time.Unix(expiry, 0) }
-)
-
-type testExchangeTokenServer struct {
-	url           string
-	authorization string
-	contentType   string
-	metricsHeader string
-	body          string
-	response      string
-}
-
-func run(t *testing.T, config *Config, tets *testExchangeTokenServer) (*oauth2.Token, error) {
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if got, want := r.URL.String(), tets.url; got != want {
-			t.Errorf("URL.String(): got %v but want %v", got, want)
-		}
-		headerAuth := r.Header.Get("Authorization")
-		if got, want := headerAuth, tets.authorization; got != want {
-			t.Errorf("got %v but want %v", got, want)
-		}
-		headerContentType := r.Header.Get("Content-Type")
-		if got, want := headerContentType, tets.contentType; got != want {
-			t.Errorf("got %v but want %v", got, want)
-		}
-		headerMetrics := r.Header.Get("x-goog-api-client")
-		if got, want := headerMetrics, tets.metricsHeader; got != want {
-			t.Errorf("got %v but want %v", got, want)
-		}
-		body, err := ioutil.ReadAll(r.Body)
-		if err != nil {
-			t.Fatalf("Failed reading request body: %s.", err)
-		}
-		if got, want := string(body), tets.body; got != want {
-			t.Errorf("Unexpected exchange payload: got %v but want %v", got, want)
-		}
-		w.Header().Set("Content-Type", "application/json")
-		w.Write([]byte(tets.response))
-	}))
-	defer server.Close()
-	config.TokenURL = server.URL
-
-	oldNow := now
-	defer func() { now = oldNow }()
-	now = testNow
-
-	ts := tokenSource{
-		ctx:  context.Background(),
-		conf: config,
-	}
-
-	return ts.Token()
-}
-
-func validateToken(t *testing.T, tok *oauth2.Token) {
-	if got, want := tok.AccessToken, correctAT; got != want {
-		t.Errorf("Unexpected access token: got %v, but wanted %v", got, want)
-	}
-	if got, want := tok.TokenType, "Bearer"; got != want {
-		t.Errorf("Unexpected TokenType: got %v, but wanted %v", got, want)
-	}
-
-	if got, want := tok.Expiry, testNow().Add(time.Duration(3600)*time.Second); got != want {
-		t.Errorf("Unexpected Expiry: got %v, but wanted %v", got, want)
-	}
-}
-
-func getExpectedMetricsHeader(source string, saImpersonation bool, configLifetime bool) string {
-	return fmt.Sprintf("gl-go/%s auth/unknown google-byoid-sdk source/%s sa-impersonation/%t config-lifetime/%t", goVersion(), source, saImpersonation, configLifetime)
-}
-
-func TestToken(t *testing.T) {
-	config := Config{
-		Audience:         "32555940559.apps.googleusercontent.com",
-		SubjectTokenType: "urn:ietf:params:oauth:token-type:id_token",
-		ClientSecret:     "notsosecret",
-		ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
-		CredentialSource: testBaseCredSource,
-		Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
-	}
-
-	server := testExchangeTokenServer{
-		url:           "/",
-		authorization: "Basic cmJyZ25vZ25yaG9uZ28zYmk0Z2I5Z2hnOWc6bm90c29zZWNyZXQ=",
-		contentType:   "application/x-www-form-urlencoded",
-		metricsHeader: getExpectedMetricsHeader("file", false, false),
-		body:          baseCredsRequestBody,
-		response:      baseCredsResponseBody,
-	}
-
-	tok, err := run(t, &config, &server)
-
-	if err != nil {
-		t.Fatalf("Unexpected error: %e", err)
-	}
-	validateToken(t, tok)
-}
-
-func TestWorkforcePoolTokenWithClientID(t *testing.T) {
-	config := Config{
-		Audience:                 "//iam.googleapis.com/locations/eu/workforcePools/pool-id/providers/provider-id",
-		SubjectTokenType:         "urn:ietf:params:oauth:token-type:id_token",
-		ClientSecret:             "notsosecret",
-		ClientID:                 "rbrgnognrhongo3bi4gb9ghg9g",
-		CredentialSource:         testBaseCredSource,
-		Scopes:                   []string{"https://www.googleapis.com/auth/devstorage.full_control"},
-		WorkforcePoolUserProject: "myProject",
-	}
-
-	server := testExchangeTokenServer{
-		url:           "/",
-		authorization: "Basic cmJyZ25vZ25yaG9uZ28zYmk0Z2I5Z2hnOWc6bm90c29zZWNyZXQ=",
-		contentType:   "application/x-www-form-urlencoded",
-		metricsHeader: getExpectedMetricsHeader("file", false, false),
-		body:          workforcePoolRequestBodyWithClientId,
-		response:      baseCredsResponseBody,
-	}
-
-	tok, err := run(t, &config, &server)
-
-	if err != nil {
-		t.Fatalf("Unexpected error: %e", err)
-	}
-	validateToken(t, tok)
-}
-
-func TestWorkforcePoolTokenWithoutClientID(t *testing.T) {
-	config := Config{
-		Audience:                 "//iam.googleapis.com/locations/eu/workforcePools/pool-id/providers/provider-id",
-		SubjectTokenType:         "urn:ietf:params:oauth:token-type:id_token",
-		ClientSecret:             "notsosecret",
-		CredentialSource:         testBaseCredSource,
-		Scopes:                   []string{"https://www.googleapis.com/auth/devstorage.full_control"},
-		WorkforcePoolUserProject: "myProject",
-	}
-
-	server := testExchangeTokenServer{
-		url:           "/",
-		authorization: "",
-		contentType:   "application/x-www-form-urlencoded",
-		metricsHeader: getExpectedMetricsHeader("file", false, false),
-		body:          workforcePoolRequestBodyWithoutClientId,
-		response:      baseCredsResponseBody,
-	}
-
-	tok, err := run(t, &config, &server)
-
-	if err != nil {
-		t.Fatalf("Unexpected error: %e", err)
-	}
-	validateToken(t, tok)
-}
-
-func TestNonworkforceWithWorkforcePoolUserProject(t *testing.T) {
-	config := Config{
-		Audience:                 "32555940559.apps.googleusercontent.com",
-		SubjectTokenType:         "urn:ietf:params:oauth:token-type:id_token",
-		TokenURL:                 "https://sts.googleapis.com",
-		ClientSecret:             "notsosecret",
-		ClientID:                 "rbrgnognrhongo3bi4gb9ghg9g",
-		CredentialSource:         testBaseCredSource,
-		Scopes:                   []string{"https://www.googleapis.com/auth/devstorage.full_control"},
-		WorkforcePoolUserProject: "myProject",
-	}
-
-	_, err := config.TokenSource(context.Background())
-
-	if err == nil {
-		t.Fatalf("Expected error but found none")
-	}
-	if got, want := err.Error(), "oauth2/google: workforce_pool_user_project should not be set for non-workforce pool credentials"; got != want {
-		t.Errorf("Incorrect error received.\nExpected: %s\nRecieved: %s", want, got)
-	}
-}
-
-func TestWorkforcePoolCreation(t *testing.T) {
-	var audienceValidatyTests = []struct {
-		audience      string
-		expectSuccess bool
-	}{
-		{"//iam.googleapis.com/locations/global/workforcePools/pool-id/providers/provider-id", true},
-		{"//iam.googleapis.com/locations/eu/workforcePools/pool-id/providers/provider-id", true},
-		{"//iam.googleapis.com/locations/eu/workforcePools/workloadIdentityPools/providers/provider-id", true},
-		{"identitynamespace:1f12345:my_provider", false},
-		{"//iam.googleapis.com/projects/123456/locations/global/workloadIdentityPools/pool-id/providers/provider-id", false},
-		{"//iam.googleapis.com/projects/123456/locations/eu/workloadIdentityPools/pool-id/providers/provider-id", false},
-		{"//iam.googleapis.com/projects/123456/locations/global/workloadIdentityPools/workforcePools/providers/provider-id", false},
-		{"//iamgoogleapis.com/locations/eu/workforcePools/pool-id/providers/provider-id", false},
-		{"//iam.googleapiscom/locations/eu/workforcePools/pool-id/providers/provider-id", false},
-		{"//iam.googleapis.com/locations/workforcePools/pool-id/providers/provider-id", false},
-		{"//iam.googleapis.com/locations/eu/workforcePool/pool-id/providers/provider-id", false},
-		{"//iam.googleapis.com/locations//workforcePool/pool-id/providers/provider-id", false},
-	}
-
-	ctx := context.Background()
-	for _, tt := range audienceValidatyTests {
-		t.Run(" "+tt.audience, func(t *testing.T) { // We prepend a space ahead of the test input when outputting for sake of readability.
-			config := testConfig
-			config.TokenURL = "https://sts.googleapis.com" // Setting the most basic acceptable tokenURL
-			config.ServiceAccountImpersonationURL = "https://iamcredentials.googleapis.com"
-			config.Audience = tt.audience
-			config.WorkforcePoolUserProject = "myProject"
-			_, err := config.TokenSource(ctx)
-
-			if tt.expectSuccess && err != nil {
-				t.Errorf("got %v but want nil", err)
-			} else if !tt.expectSuccess && err == nil {
-				t.Errorf("got nil but expected an error")
-			}
-		})
-	}
-}

google/internal/externalaccount/err.go

@@ -1,18 +0,0 @@
-// Copyright 2020 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package externalaccount
-
-import "fmt"
-
-// Error for handling OAuth related error responses as stated in rfc6749#5.2.
-type Error struct {
-	Code        string
-	URI         string
-	Description string
-}
-
-func (err *Error) Error() string {
-	return fmt.Sprintf("got error code %s from %s: %s", err.Code, err.URI, err.Description)
-}

google/internal/externalaccount/err_test.go

@@ -1,19 +0,0 @@
-// Copyright 2020 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package externalaccount
-
-import "testing"
-
-func TestError(t *testing.T) {
-	e := Error{
-		"42",
-		"http:thisIsAPlaceholder",
-		"The Answer!",
-	}
-	want := "got error code 42 from http:thisIsAPlaceholder: The Answer!"
-	if got := e.Error(); got != want {
-		t.Errorf("Got error message %q; want %q", got, want)
-	}
-}

google/internal/externalaccount/impersonate_test.go

@@ -1,144 +0,0 @@
-// Copyright 2021 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package externalaccount
-
-import (
-	"context"
-	"io/ioutil"
-	"net/http"
-	"net/http/httptest"
-	"testing"
-)
-
-var (
-	baseImpersonateCredsReqBody  = "audience=32555940559.apps.googleusercontent.com&grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange&requested_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fcloud-platform&subject_token=street123&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Ajwt"
-	baseImpersonateCredsRespBody = `{"accessToken":"Second.Access.Token","expireTime":"2020-12-28T15:01:23Z"}`
-)
-
-func createImpersonationServer(urlWanted, authWanted, bodyWanted, response string, t *testing.T) *httptest.Server {
-	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if got, want := r.URL.String(), urlWanted; got != want {
-			t.Errorf("URL.String(): got %v but want %v", got, want)
-		}
-		headerAuth := r.Header.Get("Authorization")
-		if got, want := headerAuth, authWanted; got != want {
-			t.Errorf("got %v but want %v", got, want)
-		}
-		headerContentType := r.Header.Get("Content-Type")
-		if got, want := headerContentType, "application/json"; got != want {
-			t.Errorf("got %v but want %v", got, want)
-		}
-		body, err := ioutil.ReadAll(r.Body)
-		if err != nil {
-			t.Fatalf("Failed reading request body: %v.", err)
-		}
-		if got, want := string(body), bodyWanted; got != want {
-			t.Errorf("Unexpected impersonation payload: got %v but want %v", got, want)
-		}
-		w.Header().Set("Content-Type", "application/json")
-		w.Write([]byte(response))
-	}))
-}
-
-func createTargetServer(metricsHeaderWanted string, t *testing.T) *httptest.Server {
-	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if got, want := r.URL.String(), "/"; got != want {
-			t.Errorf("URL.String(): got %v but want %v", got, want)
-		}
-		headerAuth := r.Header.Get("Authorization")
-		if got, want := headerAuth, "Basic cmJyZ25vZ25yaG9uZ28zYmk0Z2I5Z2hnOWc6bm90c29zZWNyZXQ="; got != want {
-			t.Errorf("got %v but want %v", got, want)
-		}
-		headerContentType := r.Header.Get("Content-Type")
-		if got, want := headerContentType, "application/x-www-form-urlencoded"; got != want {
-			t.Errorf("got %v but want %v", got, want)
-		}
-		headerMetrics := r.Header.Get("x-goog-api-client")
-		if got, want := headerMetrics, metricsHeaderWanted; got != want {
-			t.Errorf("got %v but want %v", got, want)
-		}
-		body, err := ioutil.ReadAll(r.Body)
-		if err != nil {
-			t.Fatalf("Failed reading request body: %v.", err)
-		}
-		if got, want := string(body), baseImpersonateCredsReqBody; got != want {
-			t.Errorf("Unexpected exchange payload: got %v but want %v", got, want)
-		}
-		w.Header().Set("Content-Type", "application/json")
-		w.Write([]byte(baseCredsResponseBody))
-	}))
-}
-
-var impersonationTests = []struct {
-	name                      string
-	config                    Config
-	expectedImpersonationBody string
-	expectedMetricsHeader     string
-}{
-	{
-		name: "Base Impersonation",
-		config: Config{
-			Audience:         "32555940559.apps.googleusercontent.com",
-			SubjectTokenType: "urn:ietf:params:oauth:token-type:jwt",
-			TokenInfoURL:     "http://localhost:8080/v1/tokeninfo",
-			ClientSecret:     "notsosecret",
-			ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
-			CredentialSource: testBaseCredSource,
-			Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
-		},
-		expectedImpersonationBody: "{\"lifetime\":\"3600s\",\"scope\":[\"https://www.googleapis.com/auth/devstorage.full_control\"]}",
-		expectedMetricsHeader:     getExpectedMetricsHeader("file", true, false),
-	},
-	{
-		name: "With TokenLifetime Set",
-		config: Config{
-			Audience:         "32555940559.apps.googleusercontent.com",
-			SubjectTokenType: "urn:ietf:params:oauth:token-type:jwt",
-			TokenInfoURL:     "http://localhost:8080/v1/tokeninfo",
-			ClientSecret:     "notsosecret",
-			ClientID:         "rbrgnognrhongo3bi4gb9ghg9g",
-			CredentialSource: testBaseCredSource,
-			Scopes:           []string{"https://www.googleapis.com/auth/devstorage.full_control"},
-			ServiceAccountImpersonationLifetimeSeconds: 10000,
-		},
-		expectedImpersonationBody: "{\"lifetime\":\"10000s\",\"scope\":[\"https://www.googleapis.com/auth/devstorage.full_control\"]}",
-		expectedMetricsHeader:     getExpectedMetricsHeader("file", true, true),
-	},
-}
-
-func TestImpersonation(t *testing.T) {
-	for _, tt := range impersonationTests {
-		t.Run(tt.name, func(t *testing.T) {
-			testImpersonateConfig := tt.config
-			impersonateServer := createImpersonationServer("/", "Bearer Sample.Access.Token", tt.expectedImpersonationBody, baseImpersonateCredsRespBody, t)
-			defer impersonateServer.Close()
-			testImpersonateConfig.ServiceAccountImpersonationURL = impersonateServer.URL
-
-			targetServer := createTargetServer(tt.expectedMetricsHeader, t)
-			defer targetServer.Close()
-			testImpersonateConfig.TokenURL = targetServer.URL
-
-			ourTS, err := testImpersonateConfig.tokenSource(context.Background(), "http")
-			if err != nil {
-				t.Fatalf("Failed to create TokenSource: %v", err)
-			}
-
-			oldNow := now
-			defer func() { now = oldNow }()
-			now = testNow
-
-			tok, err := ourTS.Token()
-			if err != nil {
-				t.Fatalf("Unexpected error: %e", err)
-			}
-			if got, want := tok.AccessToken, "Second.Access.Token"; got != want {
-				t.Errorf("Unexpected access token: got %v, but wanted %v", got, want)
-			}
-			if got, want := tok.TokenType, "Bearer"; got != want {
-				t.Errorf("Unexpected TokenType: got %v, but wanted %v", got, want)
-			}
-		})
-	}
-}

google/internal/externalaccountauthorizeduser/externalaccountauthorizeduser_test.go

@@ -8,7 +8,7 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -38,7 +38,7 @@ type testRefreshTokenServer struct {
 	server          *httptest.Server
 }
 
-func TestExernalAccountAuthorizedUser_JustToken(t *testing.T) {
+func TestExternalAccountAuthorizedUser_JustToken(t *testing.T) {
 	config := &Config{
 		Token:  "AAAAAAA",
 		Expiry: now().Add(time.Hour),
@@ -57,7 +57,7 @@ func TestExernalAccountAuthorizedUser_JustToken(t *testing.T) {
 	}
 }
 
-func TestExernalAccountAuthorizedUser_TokenRefreshWithRefreshTokenInRespondse(t *testing.T) {
+func TestExternalAccountAuthorizedUser_TokenRefreshWithRefreshTokenInResponse(t *testing.T) {
 	server := &testRefreshTokenServer{
 		URL:           "/",
 		Authorization: "Basic Q0xJRU5UX0lEOkNMSUVOVF9TRUNSRVQ=",
@@ -99,7 +99,7 @@ func TestExernalAccountAuthorizedUser_TokenRefreshWithRefreshTokenInRespondse(t
 	}
 }
 
-func TestExernalAccountAuthorizedUser_MinimumFieldsRequiredForRefresh(t *testing.T) {
+func TestExternalAccountAuthorizedUser_MinimumFieldsRequiredForRefresh(t *testing.T) {
 	server := &testRefreshTokenServer{
 		URL:           "/",
 		Authorization: "Basic Q0xJRU5UX0lEOkNMSUVOVF9TRUNSRVQ=",
@@ -187,7 +187,7 @@ func TestExternalAccountAuthorizedUser_MissingRefreshFields(t *testing.T) {
 			},
 		},
 		{
-			name: "missing client secrect",
+			name: "missing client secret",
 			config: Config{
 				RefreshToken: "BBBBBBBBB",
 				TokenURL:     url,
@@ -227,7 +227,7 @@ func (trts *testRefreshTokenServer) run(t *testing.T) (string, error) {
 		if got, want := headerContentType, trts.ContentType; got != want {
 			t.Errorf("got %v but want %v", got, want)
 		}
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Fatalf("Failed reading request body: %s.", err)
 		}

google/internal/impersonate/impersonate.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package externalaccount
+package impersonate
 
 import (
 	"bytes"
@@ -10,7 +10,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"time"
 
@@ -81,7 +80,7 @@ func (its ImpersonateTokenSource) Token() (*oauth2.Token, error) {
 		return nil, fmt.Errorf("oauth2/google: unable to generate access token: %v", err)
 	}
 	defer resp.Body.Close()
-	body, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
 		return nil, fmt.Errorf("oauth2/google: unable to read body: %v", err)
 	}

google/internal/stsexchange/sts_exchange.go

@@ -9,7 +9,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"net/url"
 	"strconv"
@@ -28,7 +27,7 @@ func defaultHeader() http.Header {
 // The first 4 fields are all mandatory.  headers can be used to pass additional
 // headers beyond the bare minimum required by the token exchange.  options can
 // be used to pass additional JSON-structured options to the remote server.
-func ExchangeToken(ctx context.Context, endpoint string, request *TokenExchangeRequest, authentication ClientAuthentication, headers http.Header, options map[string]interface{}) (*Response, error) {
+func ExchangeToken(ctx context.Context, endpoint string, request *TokenExchangeRequest, authentication ClientAuthentication, headers http.Header, options map[string]any) (*Response, error) {
 	data := url.Values{}
 	data.Set("audience", request.Audience)
 	data.Set("grant_type", "urn:ietf:params:oauth:grant-type:token-exchange")
@@ -82,7 +81,7 @@ func makeRequest(ctx context.Context, endpoint string, data url.Values, authenti
 	}
 	defer resp.Body.Close()
 
-	body, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
 		return nil, err
 	}

google/internal/stsexchange/sts_exchange_test.go

@@ -7,7 +7,7 @@ package stsexchange
 import (
 	"context"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -73,7 +73,7 @@ func TestExchangeToken(t *testing.T) {
 		if got, want := r.Header.Get("Content-Type"), "application/x-www-form-urlencoded"; got != want {
 			t.Errorf("Unexpected Content-Type header, got %v, want %v", got, want)
 		}
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Errorf("Failed reading request body: %v.", err)
 		}
@@ -132,7 +132,7 @@ var optsValues = [][]string{{"foo", "bar"}, {"cat", "pan"}}
 
 func TestExchangeToken_Opts(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Fatalf("Failed reading request body: %v.", err)
 		}
@@ -142,11 +142,11 @@ func TestExchangeToken_Opts(t *testing.T) {
 		}
 		strOpts, ok := data["options"]
 		if !ok {
-			t.Errorf("Server didn't recieve an \"options\" field.")
+			t.Errorf("Server didn't receive an \"options\" field.")
 		} else if len(strOpts) < 1 {
 			t.Errorf("\"options\" field has length 0.")
 		}
-		var opts map[string]interface{}
+		var opts map[string]any
 		err = json.Unmarshal([]byte(strOpts[0]), &opts)
 		if err != nil {
 			t.Fatalf("Couldn't parse received \"options\" field.")
@@ -159,7 +159,7 @@ func TestExchangeToken_Opts(t *testing.T) {
 		if !ok {
 			t.Errorf("Couldn't find first option parameter.")
 		} else {
-			tOpts1, ok := val.(map[string]interface{})
+			tOpts1, ok := val.(map[string]any)
 			if !ok {
 				t.Errorf("Failed to assert the first option parameter as type testOpts.")
 			} else {
@@ -176,7 +176,7 @@ func TestExchangeToken_Opts(t *testing.T) {
 		if !ok {
 			t.Errorf("Couldn't find second option parameter.")
 		} else {
-			tOpts2, ok := val2.(map[string]interface{})
+			tOpts2, ok := val2.(map[string]any)
 			if !ok {
 				t.Errorf("Failed to assert the second option parameter as type testOpts.")
 			} else {
@@ -200,7 +200,7 @@ func TestExchangeToken_Opts(t *testing.T) {
 
 	firstOption := testOpts{optsValues[0][0], optsValues[0][1]}
 	secondOption := testOpts{optsValues[1][0], optsValues[1][1]}
-	inputOpts := make(map[string]interface{})
+	inputOpts := make(map[string]any)
 	inputOpts["one"] = firstOption
 	inputOpts["two"] = secondOption
 	ExchangeToken(context.Background(), ts.URL, &exchangeTokenRequest, auth, headers, inputOpts)
@@ -220,7 +220,7 @@ func TestRefreshToken(t *testing.T) {
 		if got, want := r.Header.Get("Content-Type"), "application/x-www-form-urlencoded"; got != want {
 			t.Errorf("Unexpected Content-Type header, got %v, want %v", got, want)
 		}
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Errorf("Failed reading request body: %v.", err)
 		}

internal/client_appengine.go

@@ -1,13 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build appengine
-
-package internal
-
-import "google.golang.org/appengine/urlfetch"
-
-func init() {
-	appengineClientHook = urlfetch.Client
-}

internal/doc.go

@@ -2,5 +2,5 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package internal contains support packages for oauth2 package.
+// Package internal contains support packages for [golang.org/x/oauth2].
 package internal

internal/oauth2.go

@@ -13,7 +13,7 @@ import (
 )
 
 // ParseKey converts the binary contents of a private key file
-// to an *rsa.PrivateKey. It detects whether the private key is in a
+// to an [*rsa.PrivateKey]. It detects whether the private key is in a
 // PEM container or not. If so, it extracts the private key
 // from PEM container before conversion. It only supports PEM
 // containers with no passphrase.

internal/token.go

@@ -10,7 +10,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"math"
 	"mime"
 	"net/http"
@@ -26,9 +25,9 @@ import (
 // the requests to access protected resources on the OAuth 2.0
 // provider's backend.
 //
-// This type is a mirror of oauth2.Token and exists to break
+// This type is a mirror of [golang.org/x/oauth2.Token] and exists to break
 // an otherwise-circular dependency. Other internal packages
-// should convert this Token into an oauth2.Token before use.
+// should convert this Token into an [golang.org/x/oauth2.Token] before use.
 type Token struct {
 	// AccessToken is the token that authorizes and authenticates
 	// the requests.
@@ -50,9 +49,16 @@ type Token struct {
 	// mechanisms for that TokenSource will not be used.
 	Expiry time.Time
 
+	// ExpiresIn is the OAuth2 wire format "expires_in" field,
+	// which specifies how many seconds later the token expires,
+	// relative to an unknown time base approximately around "now".
+	// It is the application's responsibility to populate
+	// `Expiry` from `ExpiresIn` when required.
+	ExpiresIn int64 `json:"expires_in,omitempty"`
+
 	// Raw optionally contains extra metadata from the server
 	// when updating a token.
-	Raw interface{}
+	Raw any
 }
 
 // tokenJSON is the struct representing the HTTP response from OAuth2
@@ -99,14 +105,6 @@ func (e *expirationTime) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
-// RegisterBrokenAuthHeaderProvider previously did something. It is now a no-op.
-//
-// Deprecated: this function no longer does anything. Caller code that
-// wants to avoid potential extra HTTP requests made during
-// auto-probing of the provider's auth style should set
-// Endpoint.AuthStyle.
-func RegisterBrokenAuthHeaderProvider(tokenURL string) {}
-
 // AuthStyle is a copy of the golang.org/x/oauth2 package's AuthStyle type.
 type AuthStyle int
 
@@ -143,6 +141,11 @@ func (lc *LazyAuthStyleCache) Get() *AuthStyleCache {
 	return c
 }
 
+type authStyleCacheKey struct {
+	url      string
+	clientID string
+}
+
 // AuthStyleCache is the set of tokenURLs we've successfully used via
 // RetrieveToken and which style auth we ended up using.
 // It's called a cache, but it doesn't (yet?) shrink. It's expected that
@@ -150,26 +153,26 @@ func (lc *LazyAuthStyleCache) Get() *AuthStyleCache {
 // small.
 type AuthStyleCache struct {
 	mu sync.Mutex
-	m  map[string]AuthStyle // keyed by tokenURL
+	m  map[authStyleCacheKey]AuthStyle
 }
 
 // lookupAuthStyle reports which auth style we last used with tokenURL
 // when calling RetrieveToken and whether we have ever done so.
-func (c *AuthStyleCache) lookupAuthStyle(tokenURL string) (style AuthStyle, ok bool) {
+func (c *AuthStyleCache) lookupAuthStyle(tokenURL, clientID string) (style AuthStyle, ok bool) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
-	style, ok = c.m[tokenURL]
+	style, ok = c.m[authStyleCacheKey{tokenURL, clientID}]
 	return
 }
 
 // setAuthStyle adds an entry to authStyleCache, documented above.
-func (c *AuthStyleCache) setAuthStyle(tokenURL string, v AuthStyle) {
+func (c *AuthStyleCache) setAuthStyle(tokenURL, clientID string, v AuthStyle) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	if c.m == nil {
-		c.m = make(map[string]AuthStyle)
+		c.m = make(map[authStyleCacheKey]AuthStyle)
 	}
-	c.m[tokenURL] = v
+	c.m[authStyleCacheKey{tokenURL, clientID}] = v
 }
 
 // newTokenRequest returns a new *http.Request to retrieve a new token
@@ -210,9 +213,9 @@ func cloneURLValues(v url.Values) url.Values {
 }
 
 func RetrieveToken(ctx context.Context, clientID, clientSecret, tokenURL string, v url.Values, authStyle AuthStyle, styleCache *AuthStyleCache) (*Token, error) {
-	needsAuthStyleProbe := authStyle == 0
+	needsAuthStyleProbe := authStyle == AuthStyleUnknown
 	if needsAuthStyleProbe {
-		if style, ok := styleCache.lookupAuthStyle(tokenURL); ok {
+		if style, ok := styleCache.lookupAuthStyle(tokenURL, clientID); ok {
 			authStyle = style
 			needsAuthStyleProbe = false
 		} else {
@@ -242,7 +245,7 @@ func RetrieveToken(ctx context.Context, clientID, clientSecret, tokenURL string,
 		token, err = doTokenRoundTrip(ctx, req)
 	}
 	if needsAuthStyleProbe && err == nil {
-		styleCache.setAuthStyle(tokenURL, authStyle)
+		styleCache.setAuthStyle(tokenURL, clientID, authStyle)
 	}
 	// Don't overwrite `RefreshToken` with an empty value
 	// if this was a token refreshing request.
@@ -257,7 +260,7 @@ func doTokenRoundTrip(ctx context.Context, req *http.Request) (*Token, error) {
 	if err != nil {
 		return nil, err
 	}
-	body, err := ioutil.ReadAll(io.LimitReader(r.Body, 1<<20))
+	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20))
 	r.Body.Close()
 	if err != nil {
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
@@ -312,7 +315,8 @@ func doTokenRoundTrip(ctx context.Context, req *http.Request) (*Token, error) {
 			TokenType:    tj.TokenType,
 			RefreshToken: tj.RefreshToken,
 			Expiry:       tj.expiry(),
-			Raw:          make(map[string]interface{}),
+			ExpiresIn:    int64(tj.ExpiresIn),
+			Raw:          make(map[string]any),
 		}
 		json.Unmarshal(body, &token.Raw) // no error checks for optional fields
 	}

internal/token_test.go

@@ -75,3 +75,48 @@ func TestExpiresInUpperBound(t *testing.T) {
 		t.Errorf("expiration time = %v; want %v", e, want)
 	}
 }
+
+func TestAuthStyleCache(t *testing.T) {
+	var c LazyAuthStyleCache
+
+	cases := []struct {
+		url      string
+		clientID string
+		style    AuthStyle
+	}{
+		{
+			"https://host1.example.com/token",
+			"client_1",
+			AuthStyleInHeader,
+		}, {
+			"https://host2.example.com/token",
+			"client_2",
+			AuthStyleInParams,
+		}, {
+			"https://host1.example.com/token",
+			"client_3",
+			AuthStyleInParams,
+		},
+	}
+
+	for _, tt := range cases {
+		t.Run(tt.clientID, func(t *testing.T) {
+			cc := c.Get()
+			got, ok := cc.lookupAuthStyle(tt.url, tt.clientID)
+			if ok {
+				t.Fatalf("unexpected auth style found on first request: %v", got)
+			}
+
+			cc.setAuthStyle(tt.url, tt.clientID, tt.style)
+
+			got, ok = cc.lookupAuthStyle(tt.url, tt.clientID)
+			if !ok {
+				t.Fatalf("auth style not found in cache")
+			}
+
+			if got != tt.style {
+				t.Fatalf("auth style mismatch, got=%v, want=%v", got, tt.style)
+			}
+		})
+	}
+}

internal/transport.go

@@ -9,8 +9,8 @@ import (
 	"net/http"
 )
 
-// HTTPClient is the context key to use with golang.org/x/net/context's
-// WithValue function to associate an *http.Client value with a context.
+// HTTPClient is the context key to use with [context.WithValue]
+// to associate an [*http.Client] value with a context.
 var HTTPClient ContextKey
 
 // ContextKey is just an empty struct. It exists so HTTPClient can be
@@ -18,16 +18,11 @@ var HTTPClient ContextKey
 // because nobody else can create a ContextKey, being unexported.
 type ContextKey struct{}
 
-var appengineClientHook func(context.Context) *http.Client
-
 func ContextClient(ctx context.Context) *http.Client {
 	if ctx != nil {
 		if hc, ok := ctx.Value(HTTPClient).(*http.Client); ok {
 			return hc
 		}
 	}
-	if appengineClientHook != nil {
-		return appengineClientHook(ctx)
-	}
 	return http.DefaultClient
 }

jira/jira.go

@@ -13,7 +13,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"net/url"
 	"strings"
@@ -114,7 +113,7 @@ func (js jwtSource) Token() (*oauth2.Token, error) {
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
 	}
 	defer resp.Body.Close()
-	body, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
 	}
@@ -123,11 +122,7 @@ func (js jwtSource) Token() (*oauth2.Token, error) {
 	}
 
 	// tokenRes is the JSON response body.
-	var tokenRes struct {
-		AccessToken string `json:"access_token"`
-		TokenType   string `json:"token_type"`
-		ExpiresIn   int64  `json:"expires_in"` // relative seconds from now
-	}
+	var tokenRes oauth2.Token
 	if err := json.Unmarshal(body, &tokenRes); err != nil {
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
 	}

jws/jws.go

@@ -4,7 +4,7 @@
 
 // Package jws provides a partial implementation
 // of JSON Web Signature encoding and decoding.
-// It exists to support the golang.org/x/oauth2 package.
+// It exists to support the [golang.org/x/oauth2] package.
 //
 // See RFC 7515.
 //
@@ -48,7 +48,7 @@ type ClaimSet struct {
 
 	// See http://tools.ietf.org/html/draft-jones-json-web-token-10#section-4.3
 	// This array is marshalled using custom code (see (c *ClaimSet) encode()).
-	PrivateClaims map[string]interface{} `json:"-"`
+	PrivateClaims map[string]any `json:"-"`
 }
 
 func (c *ClaimSet) encode() (string, error) {
@@ -116,12 +116,12 @@ func (h *Header) encode() (string, error) {
 // Decode decodes a claim set from a JWS payload.
 func Decode(payload string) (*ClaimSet, error) {
 	// decode returned id token to get expiry
-	s := strings.Split(payload, ".")
-	if len(s) < 2 {
+	_, claims, _, ok := parseToken(payload)
+	if !ok {
 		// TODO(jbd): Provide more context about the error.
 		return nil, errors.New("jws: invalid token received")
 	}
-	decoded, err := base64.RawURLEncoding.DecodeString(s[1])
+	decoded, err := base64.RawURLEncoding.DecodeString(claims)
 	if err != nil {
 		return nil, err
 	}
@@ -152,7 +152,7 @@ func EncodeWithSigner(header *Header, c *ClaimSet, sg Signer) (string, error) {
 }
 
 // Encode encodes a signed JWS with provided header and claim set.
-// This invokes EncodeWithSigner using crypto/rsa.SignPKCS1v15 with the given RSA private key.
+// This invokes [EncodeWithSigner] using [crypto/rsa.SignPKCS1v15] with the given RSA private key.
 func Encode(header *Header, c *ClaimSet, key *rsa.PrivateKey) (string, error) {
 	sg := func(data []byte) (sig []byte, err error) {
 		h := sha256.New()
@@ -165,18 +165,34 @@ func Encode(header *Header, c *ClaimSet, key *rsa.PrivateKey) (string, error) {
 // Verify tests whether the provided JWT token's signature was produced by the private key
 // associated with the supplied public key.
 func Verify(token string, key *rsa.PublicKey) error {
-	parts := strings.Split(token, ".")
-	if len(parts) != 3 {
+	header, claims, sig, ok := parseToken(token)
+	if !ok {
 		return errors.New("jws: invalid token received, token must have 3 parts")
 	}
-
-	signedContent := parts[0] + "." + parts[1]
-	signatureString, err := base64.RawURLEncoding.DecodeString(parts[2])
+	signatureString, err := base64.RawURLEncoding.DecodeString(sig)
 	if err != nil {
 		return err
 	}
 
 	h := sha256.New()
-	h.Write([]byte(signedContent))
+	h.Write([]byte(header + tokenDelim + claims))
 	return rsa.VerifyPKCS1v15(key, crypto.SHA256, h.Sum(nil), signatureString)
 }
+
+func parseToken(s string) (header, claims, sig string, ok bool) {
+	header, s, ok = strings.Cut(s, tokenDelim)
+	if !ok { // no period found
+		return "", "", "", false
+	}
+	claims, s, ok = strings.Cut(s, tokenDelim)
+	if !ok { // only one period found
+		return "", "", "", false
+	}
+	sig, _, ok = strings.Cut(s, tokenDelim)
+	if ok { // three periods found
+		return "", "", "", false
+	}
+	return header, claims, sig, true
+}
+
+const tokenDelim = "."

jws/jws_test.go

@@ -7,6 +7,8 @@ package jws
 import (
 	"crypto/rand"
 	"crypto/rsa"
+	"net/http"
+	"strings"
 	"testing"
 )
 
@@ -39,8 +41,57 @@ func TestSignAndVerify(t *testing.T) {
 }
 
 func TestVerifyFailsOnMalformedClaim(t *testing.T) {
-	err := Verify("abc.def", nil)
-	if err == nil {
-		t.Error("got no errors; want improperly formed JWT not to be verified")
+	cases := []struct {
+		desc  string
+		token string
+	}{
+		{
+			desc:  "no periods",
+			token: "aa",
+		}, {
+			desc:  "only one period",
+			token: "a.a",
+		}, {
+			desc:  "more than two periods",
+			token: "a.a.a.a",
+		},
+	}
+	for _, tc := range cases {
+		f := func(t *testing.T) {
+			err := Verify(tc.token, nil)
+			if err == nil {
+				t.Error("got no errors; want improperly formed JWT not to be verified")
+			}
+		}
+		t.Run(tc.desc, f)
+	}
+}
+
+func BenchmarkVerify(b *testing.B) {
+	cases := []struct {
+		desc  string
+		token string
+	}{
+		{
+			desc:  "full of periods",
+			token: strings.Repeat(".", http.DefaultMaxHeaderBytes),
+		}, {
+			desc:  "two trailing periods",
+			token: strings.Repeat("a", http.DefaultMaxHeaderBytes-2) + "..",
+		},
+	}
+	privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		b.Fatal(err)
+	}
+	for _, bc := range cases {
+		f := func(b *testing.B) {
+			b.ReportAllocs()
+			b.ResetTimer()
+			for range b.N {
+				Verify(bc.token, &privateKey.PublicKey)
+			}
+		}
+		b.Run(bc.desc, f)
 	}
 }

jwt/example_test.go

@@ -10,7 +10,7 @@ import (
 	"golang.org/x/oauth2/jwt"
 )
 
-func ExampleJWTConfig() {
+func ExampleConfig() {
 	ctx := context.Background()
 	conf := &jwt.Config{
 		Email: "xxx@developer.com",

jwt/jwt.go

@@ -13,7 +13,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"net/url"
 	"strings"
@@ -69,7 +68,7 @@ type Config struct {
 
 	// PrivateClaims optionally specifies custom private claims in the JWT.
 	// See http://tools.ietf.org/html/draft-jones-json-web-token-10#section-4.3
-	PrivateClaims map[string]interface{}
+	PrivateClaims map[string]any
 
 	// UseIDToken optionally specifies whether ID token should be used instead
 	// of access token when the server returns both.
@@ -136,7 +135,7 @@ func (js jwtSource) Token() (*oauth2.Token, error) {
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
 	}
 	defer resp.Body.Close()
-	body, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
 	}
@@ -148,10 +147,8 @@ func (js jwtSource) Token() (*oauth2.Token, error) {
 	}
 	// tokenRes is the JSON response body.
 	var tokenRes struct {
-		AccessToken string `json:"access_token"`
-		TokenType   string `json:"token_type"`
-		IDToken     string `json:"id_token"`
-		ExpiresIn   int64  `json:"expires_in"` // relative seconds from now
+		oauth2.Token
+		IDToken string `json:"id_token"`
 	}
 	if err := json.Unmarshal(body, &tokenRes); err != nil {
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
@@ -160,7 +157,7 @@ func (js jwtSource) Token() (*oauth2.Token, error) {
 		AccessToken: tokenRes.AccessToken,
 		TokenType:   tokenRes.TokenType,
 	}
-	raw := make(map[string]interface{})
+	raw := make(map[string]any)
 	json.Unmarshal(body, &raw) // no error checks for optional fields
 	token = token.WithExtra(raw)
 

jwt/jwt_test.go

@@ -227,7 +227,7 @@ func TestJWTFetch_AssertionPayload(t *testing.T) {
 			PrivateKey:   dummyPrivateKey,
 			PrivateKeyID: "ABCDEFGHIJKLMNOPQRSTUVWXYZ",
 			TokenURL:     ts.URL,
-			PrivateClaims: map[string]interface{}{
+			PrivateClaims: map[string]any{
 				"private0": "claim0",
 				"private1": "claim1",
 			},
@@ -273,11 +273,11 @@ func TestJWTFetch_AssertionPayload(t *testing.T) {
 				t.Errorf("payload prn = %q; want %q", got, want)
 			}
 			if len(conf.PrivateClaims) > 0 {
-				var got interface{}
+				var got any
 				if err := json.Unmarshal(gotjson, &got); err != nil {
 					t.Errorf("failed to parse payload; err = %q", err)
 				}
-				m := got.(map[string]interface{})
+				m := got.(map[string]any)
 				for v, k := range conf.PrivateClaims {
 					if !reflect.DeepEqual(m[v], k) {
 						t.Errorf("payload private claims key = %q: got %#v; want %#v", v, m[v], k)

microsoft/microsoft.go

@@ -25,7 +25,8 @@ func AzureADEndpoint(tenant string) oauth2.Endpoint {
 		tenant = "common"
 	}
 	return oauth2.Endpoint{
-		AuthURL:  "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/authorize",
-		TokenURL: "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/token",
+		AuthURL:       "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/authorize",
+		TokenURL:      "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/token",
+		DeviceAuthURL: "https://login.microsoftonline.com/" + tenant + "/oauth2/v2.0/devicecode",
 	}
 }

oauth2.go

@@ -22,9 +22,9 @@ import (
 )
 
 // NoContext is the default context you should supply if not using
-// your own context.Context (see https://golang.org/x/net/context).
+// your own [context.Context].
 //
-// Deprecated: Use context.Background() or context.TODO() instead.
+// Deprecated: Use [context.Background] or [context.TODO] instead.
 var NoContext = context.TODO()
 
 // RegisterBrokenAuthHeaderProvider previously did something. It is now a no-op.
@@ -37,8 +37,8 @@ func RegisterBrokenAuthHeaderProvider(tokenURL string) {}
 
 // Config describes a typical 3-legged OAuth2 flow, with both the
 // client application information and the server's endpoint URLs.
-// For the client credentials 2-legged OAuth2 flow, see the clientcredentials
-// package (https://golang.org/x/oauth2/clientcredentials).
+// For the client credentials 2-legged OAuth2 flow, see the
+// [golang.org/x/oauth2/clientcredentials] package.
 type Config struct {
 	// ClientID is the application's ID.
 	ClientID string
@@ -46,7 +46,7 @@ type Config struct {
 	// ClientSecret is the application's secret.
 	ClientSecret string
 
-	// Endpoint contains the resource server's token endpoint
+	// Endpoint contains the authorization server's token endpoint
 	// URLs. These are constants specific to each server and are
 	// often available via site-specific packages, such as
 	// google.Endpoint or github.Endpoint.
@@ -56,7 +56,7 @@ type Config struct {
 	// the OAuth flow, after the resource owner's URLs.
 	RedirectURL string
 
-	// Scope specifies optional requested permissions.
+	// Scopes specifies optional requested permissions.
 	Scopes []string
 
 	// authStyleCache caches which auth style to use when Endpoint.AuthStyle is
@@ -135,7 +135,7 @@ type setParam struct{ k, v string }
 
 func (p setParam) setValue(m url.Values) { m.Set(p.k, p.v) }
 
-// SetAuthURLParam builds an AuthCodeOption which passes key/value parameters
+// SetAuthURLParam builds an [AuthCodeOption] which passes key/value parameters
 // to a provider's authorization endpoint.
 func SetAuthURLParam(key, value string) AuthCodeOption {
 	return setParam{key, value}
@@ -148,8 +148,8 @@ func SetAuthURLParam(key, value string) AuthCodeOption {
 // request and callback. The authorization server includes this value when
 // redirecting the user agent back to the client.
 //
-// Opts may include AccessTypeOnline or AccessTypeOffline, as well
-// as ApprovalForce.
+// Opts may include [AccessTypeOnline] or [AccessTypeOffline], as well
+// as [ApprovalForce].
 //
 // To protect against CSRF attacks, opts should include a PKCE challenge
 // (S256ChallengeOption). Not all servers support PKCE. An alternative is to
@@ -194,7 +194,7 @@ func (c *Config) AuthCodeURL(state string, opts ...AuthCodeOption) string {
 // and when other authorization grant types are not available."
 // See https://tools.ietf.org/html/rfc6749#section-4.3 for more info.
 //
-// The provided context optionally controls which HTTP client is used. See the HTTPClient variable.
+// The provided context optionally controls which HTTP client is used. See the [HTTPClient] variable.
 func (c *Config) PasswordCredentialsToken(ctx context.Context, username, password string) (*Token, error) {
 	v := url.Values{
 		"grant_type": {"password"},
@@ -212,10 +212,10 @@ func (c *Config) PasswordCredentialsToken(ctx context.Context, username, passwor
 // It is used after a resource provider redirects the user back
 // to the Redirect URI (the URL obtained from AuthCodeURL).
 //
-// The provided context optionally controls which HTTP client is used. See the HTTPClient variable.
+// The provided context optionally controls which HTTP client is used. See the [HTTPClient] variable.
 //
-// The code will be in the *http.Request.FormValue("code"). Before
-// calling Exchange, be sure to validate FormValue("state") if you are
+// The code will be in the [http.Request.FormValue]("code"). Before
+// calling Exchange, be sure to validate [http.Request.FormValue]("state") if you are
 // using it to protect against CSRF attacks.
 //
 // If using PKCE to protect against CSRF attacks, opts should include a
@@ -242,10 +242,10 @@ func (c *Config) Client(ctx context.Context, t *Token) *http.Client {
 	return NewClient(ctx, c.TokenSource(ctx, t))
 }
 
-// TokenSource returns a TokenSource that returns t until t expires,
+// TokenSource returns a [TokenSource] that returns t until t expires,
 // automatically refreshing it as necessary using the provided context.
 //
-// Most users will use Config.Client instead.
+// Most users will use [Config.Client] instead.
 func (c *Config) TokenSource(ctx context.Context, t *Token) TokenSource {
 	tkr := &tokenRefresher{
 		ctx:  ctx,
@@ -260,7 +260,7 @@ func (c *Config) TokenSource(ctx context.Context, t *Token) TokenSource {
 	}
 }
 
-// tokenRefresher is a TokenSource that makes "grant_type"=="refresh_token"
+// tokenRefresher is a TokenSource that makes "grant_type=refresh_token"
 // HTTP requests to renew a token using a RefreshToken.
 type tokenRefresher struct {
 	ctx          context.Context // used to get HTTP requests
@@ -288,7 +288,7 @@ func (tf *tokenRefresher) Token() (*Token, error) {
 	if tf.refreshToken != tk.RefreshToken {
 		tf.refreshToken = tk.RefreshToken
 	}
-	return tk, err
+	return tk, nil
 }
 
 // reuseTokenSource is a TokenSource that holds a single token in memory
@@ -305,8 +305,7 @@ type reuseTokenSource struct {
 }
 
 // Token returns the current token if it's still valid, else will
-// refresh the current token (using r.Context for HTTP client
-// information) and return the new one.
+// refresh the current token and return the new one.
 func (s *reuseTokenSource) Token() (*Token, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -322,7 +321,7 @@ func (s *reuseTokenSource) Token() (*Token, error) {
 	return t, nil
 }
 
-// StaticTokenSource returns a TokenSource that always returns the same token.
+// StaticTokenSource returns a [TokenSource] that always returns the same token.
 // Because the provided token t is never refreshed, StaticTokenSource is only
 // useful for tokens that never expire.
 func StaticTokenSource(t *Token) TokenSource {
@@ -338,16 +337,16 @@ func (s staticTokenSource) Token() (*Token, error) {
 	return s.t, nil
 }
 
-// HTTPClient is the context key to use with golang.org/x/net/context's
-// WithValue function to associate an *http.Client value with a context.
+// HTTPClient is the context key to use with [context.WithValue]
+// to associate a [*http.Client] value with a context.
 var HTTPClient internal.ContextKey
 
-// NewClient creates an *http.Client from a Context and TokenSource.
+// NewClient creates an [*http.Client] from a [context.Context] and [TokenSource].
 // The returned client is not valid beyond the lifetime of the context.
 //
-// Note that if a custom *http.Client is provided via the Context it
+// Note that if a custom [*http.Client] is provided via the [context.Context] it
 // is used only for token acquisition and is not used to configure the
-// *http.Client returned from NewClient.
+// [*http.Client] returned from NewClient.
 //
 // As a special case, if src is nil, a non-OAuth2 client is returned
 // using the provided context. This exists to support related OAuth2
@@ -356,15 +355,19 @@ func NewClient(ctx context.Context, src TokenSource) *http.Client {
 	if src == nil {
 		return internal.ContextClient(ctx)
 	}
+	cc := internal.ContextClient(ctx)
 	return &http.Client{
 		Transport: &Transport{
-			Base:   internal.ContextClient(ctx).Transport,
+			Base:   cc.Transport,
 			Source: ReuseTokenSource(nil, src),
 		},
+		CheckRedirect: cc.CheckRedirect,
+		Jar:           cc.Jar,
+		Timeout:       cc.Timeout,
 	}
 }
 
-// ReuseTokenSource returns a TokenSource which repeatedly returns the
+// ReuseTokenSource returns a [TokenSource] which repeatedly returns the
 // same token as long as it's valid, starting with t.
 // When its cached token is invalid, a new token is obtained from src.
 //
@@ -372,10 +375,10 @@ func NewClient(ctx context.Context, src TokenSource) *http.Client {
 // (such as a file on disk) between runs of a program, rather than
 // obtaining new tokens unnecessarily.
 //
-// The initial token t may be nil, in which case the TokenSource is
+// The initial token t may be nil, in which case the [TokenSource] is
 // wrapped in a caching version if it isn't one already. This also
 // means it's always safe to wrap ReuseTokenSource around any other
-// TokenSource without adverse effects.
+// [TokenSource] without adverse effects.
 func ReuseTokenSource(t *Token, src TokenSource) TokenSource {
 	// Don't wrap a reuseTokenSource in itself. That would work,
 	// but cause an unnecessary number of mutex operations.
@@ -393,8 +396,8 @@ func ReuseTokenSource(t *Token, src TokenSource) TokenSource {
 	}
 }
 
-// ReuseTokenSource returns a TokenSource that acts in the same manner as the
-// TokenSource returned by ReuseTokenSource, except the expiry buffer is
+// ReuseTokenSourceWithExpiry returns a [TokenSource] that acts in the same manner as the
+// [TokenSource] returned by [ReuseTokenSource], except the expiry buffer is
 // configurable. The expiration time of a token is calculated as
 // t.Expiry.Add(-earlyExpiry).
 func ReuseTokenSourceWithExpiry(t *Token, src TokenSource, earlyExpiry time.Duration) TokenSource {

oauth2_test.go

@@ -9,7 +9,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -104,7 +103,7 @@ func TestExchangeRequest(t *testing.T) {
 		if headerContentType != "application/x-www-form-urlencoded" {
 			t.Errorf("Unexpected Content-Type header %q", headerContentType)
 		}
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Errorf("Failed reading request body: %s.", err)
 		}
@@ -148,7 +147,7 @@ func TestExchangeRequest_CustomParam(t *testing.T) {
 		if headerContentType != "application/x-www-form-urlencoded" {
 			t.Errorf("Unexpected Content-Type header, %v is found.", headerContentType)
 		}
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Errorf("Failed reading request body: %s.", err)
 		}
@@ -194,7 +193,7 @@ func TestExchangeRequest_JSONResponse(t *testing.T) {
 		if headerContentType != "application/x-www-form-urlencoded" {
 			t.Errorf("Unexpected Content-Type header, %v is found.", headerContentType)
 		}
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Errorf("Failed reading request body: %s.", err)
 		}
@@ -301,7 +300,7 @@ func testExchangeRequest_JSONResponse_expiry(t *testing.T, exp string, want, nul
 	conf := newConf(ts.URL)
 	t1 := time.Now().Add(day)
 	tok, err := conf.Exchange(context.Background(), "exchange-code")
-	t2 := t1.Add(day)
+	t2 := time.Now().Add(day)
 
 	if got := (err == nil); got != want {
 		if want {
@@ -393,7 +392,7 @@ func TestPasswordCredentialsTokenRequest(t *testing.T) {
 		if headerContentType != expected {
 			t.Errorf("Content-Type header = %q; want %q", headerContentType, expected)
 		}
-		body, err := ioutil.ReadAll(r.Body)
+		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			t.Errorf("Failed reading request body: %s.", err)
 		}
@@ -435,7 +434,7 @@ func TestTokenRefreshRequest(t *testing.T) {
 		if headerContentType != "application/x-www-form-urlencoded" {
 			t.Errorf("Unexpected Content-Type header %q", headerContentType)
 		}
-		body, _ := ioutil.ReadAll(r.Body)
+		body, _ := io.ReadAll(r.Body)
 		if string(body) != "grant_type=refresh_token&refresh_token=REFRESH_TOKEN" {
 			t.Errorf("Unexpected refresh token payload %q", body)
 		}
@@ -460,7 +459,7 @@ func TestFetchWithNoRefreshToken(t *testing.T) {
 		if headerContentType != "application/x-www-form-urlencoded" {
 			t.Errorf("Unexpected Content-Type header, %v is found.", headerContentType)
 		}
-		body, _ := ioutil.ReadAll(r.Body)
+		body, _ := io.ReadAll(r.Body)
 		if string(body) != "client_id=CLIENT_ID&grant_type=refresh_token&refresh_token=REFRESH_TOKEN" {
 			t.Errorf("Unexpected refresh token payload, %v is found.", string(body))
 		}

pkce.go

@@ -1,6 +1,7 @@
 // Copyright 2023 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
+
 package oauth2
 
 import (
@@ -20,9 +21,9 @@ const (
 // This follows recommendations in RFC 7636.
 //
 // A fresh verifier should be generated for each authorization.
-// S256ChallengeOption(verifier) should then be passed to Config.AuthCodeURL
-// (or Config.DeviceAccess) and VerifierOption(verifier) to Config.Exchange
-// (or Config.DeviceAccessToken).
+// The resulting verifier should be passed to [Config.AuthCodeURL] or [Config.DeviceAuth]
+// with [S256ChallengeOption], and to [Config.Exchange] or [Config.DeviceAccessToken]
+// with [VerifierOption].
 func GenerateVerifier() string {
 	// "RECOMMENDED that the output of a suitable random number generator be
 	// used to create a 32-octet sequence.  The octet sequence is then
@@ -36,22 +37,22 @@ func GenerateVerifier() string {
 	return base64.RawURLEncoding.EncodeToString(data)
 }
 
-// VerifierOption returns a PKCE code verifier AuthCodeOption. It should be
-// passed to Config.Exchange or Config.DeviceAccessToken only.
+// VerifierOption returns a PKCE code verifier [AuthCodeOption]. It should only be
+// passed to [Config.Exchange] or [Config.DeviceAccessToken].
 func VerifierOption(verifier string) AuthCodeOption {
 	return setParam{k: codeVerifierKey, v: verifier}
 }
 
 // S256ChallengeFromVerifier returns a PKCE code challenge derived from verifier with method S256.
 //
-// Prefer to use S256ChallengeOption where possible.
+// Prefer to use [S256ChallengeOption] where possible.
 func S256ChallengeFromVerifier(verifier string) string {
 	sha := sha256.Sum256([]byte(verifier))
 	return base64.RawURLEncoding.EncodeToString(sha[:])
 }
 
 // S256ChallengeOption derives a PKCE code challenge derived from verifier with
-// method S256. It should be passed to Config.AuthCodeURL or Config.DeviceAccess
+// method S256. It should be passed to [Config.AuthCodeURL] or [Config.DeviceAuth]
 // only.
 func S256ChallengeOption(verifier string) AuthCodeOption {
 	return challengeOption{

token.go

@@ -44,14 +44,21 @@ type Token struct {
 
 	// Expiry is the optional expiration time of the access token.
 	//
-	// If zero, TokenSource implementations will reuse the same
+	// If zero, [TokenSource] implementations will reuse the same
 	// token forever and RefreshToken or equivalent
 	// mechanisms for that TokenSource will not be used.
 	Expiry time.Time `json:"expiry,omitempty"`
 
+	// ExpiresIn is the OAuth2 wire format "expires_in" field,
+	// which specifies how many seconds later the token expires,
+	// relative to an unknown time base approximately around "now".
+	// It is the application's responsibility to populate
+	// `Expiry` from `ExpiresIn` when required.
+	ExpiresIn int64 `json:"expires_in,omitempty"`
+
 	// raw optionally contains extra metadata from the server
 	// when updating a token.
-	raw interface{}
+	raw any
 
 	// expiryDelta is used to calculate when a token is considered
 	// expired, by subtracting from Expiry. If zero, defaultExpiryDelta
@@ -79,16 +86,16 @@ func (t *Token) Type() string {
 // SetAuthHeader sets the Authorization header to r using the access
 // token in t.
 //
-// This method is unnecessary when using Transport or an HTTP Client
+// This method is unnecessary when using [Transport] or an HTTP Client
 // returned by this package.
 func (t *Token) SetAuthHeader(r *http.Request) {
 	r.Header.Set("Authorization", t.Type()+" "+t.AccessToken)
 }
 
-// WithExtra returns a new Token that's a clone of t, but using the
+// WithExtra returns a new [Token] that's a clone of t, but using the
 // provided raw extra map. This is only intended for use by packages
 // implementing derivative OAuth2 flows.
-func (t *Token) WithExtra(extra interface{}) *Token {
+func (t *Token) WithExtra(extra any) *Token {
 	t2 := new(Token)
 	*t2 = *t
 	t2.raw = extra
@@ -98,8 +105,8 @@ func (t *Token) WithExtra(extra interface{}) *Token {
 // Extra returns an extra field.
 // Extra fields are key-value pairs returned by the server as a
 // part of the token retrieval response.
-func (t *Token) Extra(key string) interface{} {
-	if raw, ok := t.raw.(map[string]interface{}); ok {
+func (t *Token) Extra(key string) any {
+	if raw, ok := t.raw.(map[string]any); ok {
 		return raw[key]
 	}
 
@@ -156,13 +163,14 @@ func tokenFromInternal(t *internal.Token) *Token {
 		TokenType:    t.TokenType,
 		RefreshToken: t.RefreshToken,
 		Expiry:       t.Expiry,
+		ExpiresIn:    t.ExpiresIn,
 		raw:          t.Raw,
 	}
 }
 
 // retrieveToken takes a *Config and uses that to retrieve an *internal.Token.
 // This token is then mapped from *internal.Token into an *oauth2.Token which is returned along
-// with an error..
+// with an error.
 func retrieveToken(ctx context.Context, c *Config, v url.Values) (*Token, error) {
 	tk, err := internal.RetrieveToken(ctx, c.ClientID, c.ClientSecret, c.Endpoint.TokenURL, v, internal.AuthStyle(c.Endpoint.AuthStyle), c.authStyleCache.Get())
 	if err != nil {

token_test.go

@@ -12,8 +12,8 @@ import (
 func TestTokenExtra(t *testing.T) {
 	type testCase struct {
 		key  string
-		val  interface{}
-		want interface{}
+		val  any
+		want any
 	}
 	const key = "extra-key"
 	cases := []testCase{
@@ -23,7 +23,7 @@ func TestTokenExtra(t *testing.T) {
 		{key: "other-key", val: "def", want: nil},
 	}
 	for _, tc := range cases {
-		extra := make(map[string]interface{})
+		extra := make(map[string]any)
 		extra[tc.key] = tc.val
 		tok := &Token{raw: extra}
 		if got, want := tok.Extra(key), tc.want; got != want {

transport.go

@@ -11,12 +11,12 @@ import (
 	"sync"
 )
 
-// Transport is an http.RoundTripper that makes OAuth 2.0 HTTP requests,
-// wrapping a base RoundTripper and adding an Authorization header
-// with a token from the supplied Sources.
+// Transport is an [http.RoundTripper] that makes OAuth 2.0 HTTP requests,
+// wrapping a base [http.RoundTripper] and adding an Authorization header
+// with a token from the supplied [TokenSource].
 //
 // Transport is a low-level mechanism. Most code will use the
-// higher-level Config.Client method instead.
+// higher-level [Config.Client] method instead.
 type Transport struct {
 	// Source supplies the token to add to outgoing requests'
 	// Authorization headers.
@@ -47,7 +47,7 @@ func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
 		return nil, err
 	}
 
-	req2 := cloneRequest(req) // per RoundTripper contract
+	req2 := req.Clone(req.Context())
 	token.SetAuthHeader(req2)
 
 	// req.Body is assumed to be closed by the base RoundTripper.
@@ -73,17 +73,3 @@ func (t *Transport) base() http.RoundTripper {
 	}
 	return http.DefaultTransport
 }
-
-// cloneRequest returns a clone of the provided *http.Request.
-// The clone is a shallow copy of the struct and its Header map.
-func cloneRequest(r *http.Request) *http.Request {
-	// shallow copy of the struct
-	r2 := new(http.Request)
-	*r2 = *r
-	// deep copy of the Header
-	r2.Header = make(http.Header, len(r.Header))
-	for k, s := range r.Header {
-		r2.Header[k] = append([]string(nil), s...)
-	}
-	return r2
-}

transport_test.go

@@ -9,12 +9,6 @@ import (
 	"time"
 )
 
-type tokenSource struct{ token *Token }
-
-func (t *tokenSource) Token() (*Token, error) {
-	return t.token, nil
-}
-
 func TestTransportNilTokenSource(t *testing.T) {
 	tr := &Transport{}
 	server := newMockServer(func(w http.ResponseWriter, r *http.Request) {})
@@ -88,13 +82,10 @@ func TestTransportCloseRequestBodySuccess(t *testing.T) {
 }
 
 func TestTransportTokenSource(t *testing.T) {
-	ts := &tokenSource{
-		token: &Token{
-			AccessToken: "abc",
-		},
-	}
 	tr := &Transport{
-		Source: ts,
+		Source: StaticTokenSource(&Token{
+			AccessToken: "abc",
+		}),
 	}
 	server := newMockServer(func(w http.ResponseWriter, r *http.Request) {
 		if got, want := r.Header.Get("Authorization"), "Bearer abc"; got != want {
@@ -123,14 +114,11 @@ func TestTransportTokenSourceTypes(t *testing.T) {
 		{key: "basic", val: val, want: "Basic abc"},
 	}
 	for _, tc := range tests {
-		ts := &tokenSource{
-			token: &Token{
+		tr := &Transport{
+			Source: StaticTokenSource(&Token{
 				AccessToken: tc.val,
 				TokenType:   tc.key,
-			},
-		}
-		tr := &Transport{
-			Source: ts,
+			}),
 		}
 		server := newMockServer(func(w http.ResponseWriter, r *http.Request) {
 			if got, want := r.Header.Get("Authorization"), tc.want; got != want {