migrate gplus to google oauth2 provider (#7885)

* migrate gplus to google oauth2 provider. this still provides support for old gplus connections.

* Update models/oauth2.go

Co-Authored-By: Antoine GIRARD <sapk@users.noreply.github.com>

* make vendor

10 files changed, 1187 insertions, 0 deletions

diff --git a/vendor/golang.org/x/oauth2/google/appengine.go b/vendor/golang.org/x/oauth2/google/appengine.go
new file mode 100644
index 0000000000..feb1157b15
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/google/appengine.go
@@ -0,0 +1,38 @@
+// Copyright 2014 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 google
+
+import (
+	"context"
+	"time"
+
+	"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
+
+// AppEngineTokenSource returns a token source that fetches tokens from either
+// the current application's service account or from the metadata server,
+// depending on the App Engine environment. See below for environment-specific
+// 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
+// current App Engine application's service account. The provided context must have
+// come from appengine.NewContext.
+//
+// Second generation App Engine runtimes (>= Go 1.11) and App Engine flexible:
+// AppEngineTokenSource is DEPRECATED on second generation runtimes and on the
+// flexible environment. It delegates to ComputeTokenSource, and the provided
+// 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...)
+}
diff --git a/vendor/golang.org/x/oauth2/google/appengine_gen1.go b/vendor/golang.org/x/oauth2/google/appengine_gen1.go
new file mode 100644
index 0000000000..83dacac320
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/google/appengine_gen1.go
@@ -0,0 +1,77 @@
+// 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.
+
+// +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
+}
diff --git a/vendor/golang.org/x/oauth2/google/appengine_gen2_flex.go b/vendor/golang.org/x/oauth2/google/appengine_gen2_flex.go
new file mode 100644
index 0000000000..04c2c2216a
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/google/appengine_gen2_flex.go
@@ -0,0 +1,27 @@
+// 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.
+
+// +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("")
+}
diff --git a/vendor/golang.org/x/oauth2/google/default.go b/vendor/golang.org/x/oauth2/google/default.go
new file mode 100644
index 0000000000..ad2c09236c
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/google/default.go
@@ -0,0 +1,154 @@
+// Copyright 2015 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 google
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"path/filepath"
+	"runtime"
+
+	"cloud.google.com/go/compute/metadata"
+	"golang.org/x/oauth2"
+)
+
+// Credentials holds Google credentials, including "Application Default Credentials".
+// For more details, see:
+// https://developers.google.com/accounts/docs/application-default-credentials
+type Credentials struct {
+	ProjectID   string // may be empty
+	TokenSource oauth2.TokenSource
+
+	// JSON contains the raw bytes from a JSON credentials file.
+	// This field may be nil if authentication is provided by the
+	// environment and not with a credentials file, e.g. when code is
+	// running on Google Cloud Platform.
+	JSON []byte
+}
+
+// DefaultCredentials is the old name of Credentials.
+//
+// Deprecated: use Credentials instead.
+type DefaultCredentials = Credentials
+
+// DefaultClient returns an HTTP Client that uses the
+// DefaultTokenSource to obtain authentication credentials.
+func DefaultClient(ctx context.Context, scope ...string) (*http.Client, error) {
+	ts, err := DefaultTokenSource(ctx, scope...)
+	if err != nil {
+		return nil, err
+	}
+	return oauth2.NewClient(ctx, ts), nil
+}
+
+// DefaultTokenSource returns the token source for
+// "Application Default Credentials".
+// It is a shortcut for FindDefaultCredentials(ctx, scope).TokenSource.
+func DefaultTokenSource(ctx context.Context, scope ...string) (oauth2.TokenSource, error) {
+	creds, err := FindDefaultCredentials(ctx, scope...)
+	if err != nil {
+		return nil, err
+	}
+	return creds.TokenSource, nil
+}
+
+// FindDefaultCredentials searches for "Application Default Credentials".
+//
+// It looks for credentials in the following places,
+// preferring the first location found:
+//
+//   1. A JSON file whose path is specified by the
+//      GOOGLE_APPLICATION_CREDENTIALS environment variable.
+//   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
+//      (>= Go 1.11), and Google App Engine flexible environment, it fetches
+//      credentials from the metadata server.
+func FindDefaultCredentials(ctx context.Context, scopes ...string) (*Credentials, error) {
+	// First, try the environment variable.
+	const envVar = "GOOGLE_APPLICATION_CREDENTIALS"
+	if filename := os.Getenv(envVar); filename != "" {
+		creds, err := readCredentialsFile(ctx, filename, scopes)
+		if err != nil {
+			return nil, fmt.Errorf("google: error getting credentials using %v environment variable: %v", envVar, err)
+		}
+		return creds, nil
+	}
+
+	// Second, try a well-known file.
+	filename := wellKnownFile()
+	if creds, err := readCredentialsFile(ctx, filename, scopes); err == nil {
+		return creds, nil
+	} else if !os.IsNotExist(err) {
+		return nil, fmt.Errorf("google: error getting credentials using well-known file (%v): %v", filename, err)
+	}
+
+	// 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 &DefaultCredentials{
+			ProjectID:   appengineAppIDFunc(ctx),
+			TokenSource: AppEngineTokenSource(ctx, scopes...),
+		}, nil
+	}
+
+	// Fourth, 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()
+		return &DefaultCredentials{
+			ProjectID:   id,
+			TokenSource: ComputeTokenSource("", scopes...),
+		}, nil
+	}
+
+	// None are found; return helpful error.
+	const url = "https://developers.google.com/accounts/docs/application-default-credentials"
+	return nil, fmt.Errorf("google: could not find default credentials. See %v for more information.", url)
+}
+
+// CredentialsFromJSON obtains Google credentials from a JSON value. The JSON can
+// represent either a Google Developers Console client_credentials.json file (as in
+// ConfigFromJSON) or a Google Developers service account key file (as in
+// JWTConfigFromJSON).
+func CredentialsFromJSON(ctx context.Context, jsonData []byte, scopes ...string) (*Credentials, error) {
+	var f credentialsFile
+	if err := json.Unmarshal(jsonData, &f); err != nil {
+		return nil, err
+	}
+	ts, err := f.tokenSource(ctx, append([]string(nil), scopes...))
+	if err != nil {
+		return nil, err
+	}
+	return &DefaultCredentials{
+		ProjectID:   f.ProjectID,
+		TokenSource: ts,
+		JSON:        jsonData,
+	}, nil
+}
+
+func wellKnownFile() string {
+	const f = "application_default_credentials.json"
+	if runtime.GOOS == "windows" {
+		return filepath.Join(os.Getenv("APPDATA"), "gcloud", f)
+	}
+	return filepath.Join(guessUnixHomeDir(), ".config", "gcloud", f)
+}
+
+func readCredentialsFile(ctx context.Context, filename string, scopes []string) (*DefaultCredentials, error) {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return CredentialsFromJSON(ctx, b, scopes...)
+}
diff --git a/vendor/golang.org/x/oauth2/google/doc.go b/vendor/golang.org/x/oauth2/google/doc.go
new file mode 100644
index 0000000000..73be629033
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/google/doc.go
@@ -0,0 +1,40 @@
+// 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.
+
+// Package google provides support for making OAuth2 authorized and authenticated
+// HTTP requests to Google APIs. It supports the Web server flow, client-side
+// credentials, service accounts, Google Compute Engine service accounts, and Google
+// App Engine service accounts.
+//
+// A brief overview of the package follows. For more information, please read
+// https://developers.google.com/accounts/docs/OAuth2
+// and
+// https://developers.google.com/accounts/docs/application-default-credentials.
+//
+// OAuth2 Configs
+//
+// Two functions in this package return golang.org/x/oauth2.Config values from Google credential
+// data. Google supports two JSON formats for OAuth2 credentials: one is handled by ConfigFromJSON,
+// the other by JWTConfigFromJSON. The returned Config can be used to obtain a TokenSource or
+// create an http.Client.
+//
+//
+// Credentials
+//
+// The Credentials type represents Google credentials, including Application Default
+// Credentials.
+//
+// Use FindDefaultCredentials to obtain Application Default Credentials.
+// FindDefaultCredentials looks in some well-known places for a credentials file, and
+// will call AppEngineTokenSource or ComputeTokenSource as needed.
+//
+// DefaultClient and DefaultTokenSource are convenience methods. They first call FindDefaultCredentials,
+// then use the credentials to construct an http.Client or an oauth2.TokenSource.
+//
+// Use CredentialsFromJSON to obtain credentials from either of the two JSON formats
+// described in OAuth2 Configs, above. The TokenSource in the returned value is the
+// same as the one obtained from the oauth2.Config returned from ConfigFromJSON or
+// JWTConfigFromJSON, but the Credentials may contain additional information
+// that is useful is some circumstances.
+package google // import "golang.org/x/oauth2/google"
diff --git a/vendor/golang.org/x/oauth2/google/google.go b/vendor/golang.org/x/oauth2/google/google.go
new file mode 100644
index 0000000000..81de32b360
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/google/google.go
@@ -0,0 +1,209 @@
+// Copyright 2014 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 google
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/url"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/compute/metadata"
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/jwt"
+)
+
+// Endpoint is Google's OAuth 2.0 endpoint.
+var Endpoint = oauth2.Endpoint{
+	AuthURL:   "https://accounts.google.com/o/oauth2/auth",
+	TokenURL:  "https://oauth2.googleapis.com/token",
+	AuthStyle: oauth2.AuthStyleInParams,
+}
+
+// JWTTokenURL is Google's OAuth 2.0 token URL to use with the JWT flow.
+const JWTTokenURL = "https://oauth2.googleapis.com/token"
+
+// ConfigFromJSON uses a Google Developers Console client_credentials.json
+// file to construct a config.
+// client_credentials.json can be downloaded from
+// https://console.developers.google.com, under "Credentials". Download the Web
+// application credentials in the JSON format and provide the contents of the
+// file as jsonKey.
+func ConfigFromJSON(jsonKey []byte, scope ...string) (*oauth2.Config, error) {
+	type cred struct {
+		ClientID     string   `json:"client_id"`
+		ClientSecret string   `json:"client_secret"`
+		RedirectURIs []string `json:"redirect_uris"`
+		AuthURI      string   `json:"auth_uri"`
+		TokenURI     string   `json:"token_uri"`
+	}
+	var j struct {
+		Web       *cred `json:"web"`
+		Installed *cred `json:"installed"`
+	}
+	if err := json.Unmarshal(jsonKey, &j); err != nil {
+		return nil, err
+	}
+	var c *cred
+	switch {
+	case j.Web != nil:
+		c = j.Web
+	case j.Installed != nil:
+		c = j.Installed
+	default:
+		return nil, fmt.Errorf("oauth2/google: no credentials found")
+	}
+	if len(c.RedirectURIs) < 1 {
+		return nil, errors.New("oauth2/google: missing redirect URL in the client_credentials.json")
+	}
+	return &oauth2.Config{
+		ClientID:     c.ClientID,
+		ClientSecret: c.ClientSecret,
+		RedirectURL:  c.RedirectURIs[0],
+		Scopes:       scope,
+		Endpoint: oauth2.Endpoint{
+			AuthURL:  c.AuthURI,
+			TokenURL: c.TokenURI,
+		},
+	}, nil
+}
+
+// JWTConfigFromJSON uses a Google Developers service account JSON key file to read
+// the credentials that authorize and authenticate the requests.
+// Create a service account on "Credentials" for your project at
+// https://console.developers.google.com to download a JSON key file.
+func JWTConfigFromJSON(jsonKey []byte, scope ...string) (*jwt.Config, error) {
+	var f credentialsFile
+	if err := json.Unmarshal(jsonKey, &f); err != nil {
+		return nil, err
+	}
+	if f.Type != serviceAccountKey {
+		return nil, fmt.Errorf("google: read JWT from JSON credentials: 'type' field is %q (expected %q)", f.Type, serviceAccountKey)
+	}
+	scope = append([]string(nil), scope...) // copy
+	return f.jwtConfig(scope), nil
+}
+
+// JSON key file types.
+const (
+	serviceAccountKey  = "service_account"
+	userCredentialsKey = "authorized_user"
+)
+
+// credentialsFile is the unmarshalled representation of a credentials file.
+type credentialsFile struct {
+	Type string `json:"type"` // serviceAccountKey or userCredentialsKey
+
+	// Service Account fields
+	ClientEmail  string `json:"client_email"`
+	PrivateKeyID string `json:"private_key_id"`
+	PrivateKey   string `json:"private_key"`
+	TokenURL     string `json:"token_uri"`
+	ProjectID    string `json:"project_id"`
+
+	// User Credential fields
+	// (These typically come from gcloud auth.)
+	ClientSecret string `json:"client_secret"`
+	ClientID     string `json:"client_id"`
+	RefreshToken string `json:"refresh_token"`
+}
+
+func (f *credentialsFile) jwtConfig(scopes []string) *jwt.Config {
+	cfg := &jwt.Config{
+		Email:        f.ClientEmail,
+		PrivateKey:   []byte(f.PrivateKey),
+		PrivateKeyID: f.PrivateKeyID,
+		Scopes:       scopes,
+		TokenURL:     f.TokenURL,
+	}
+	if cfg.TokenURL == "" {
+		cfg.TokenURL = JWTTokenURL
+	}
+	return cfg
+}
+
+func (f *credentialsFile) tokenSource(ctx context.Context, scopes []string) (oauth2.TokenSource, error) {
+	switch f.Type {
+	case serviceAccountKey:
+		cfg := f.jwtConfig(scopes)
+		return cfg.TokenSource(ctx), nil
+	case userCredentialsKey:
+		cfg := &oauth2.Config{
+			ClientID:     f.ClientID,
+			ClientSecret: f.ClientSecret,
+			Scopes:       scopes,
+			Endpoint:     Endpoint,
+		}
+		tok := &oauth2.Token{RefreshToken: f.RefreshToken}
+		return cfg.TokenSource(ctx, tok), nil
+	case "":
+		return nil, errors.New("missing 'type' field in credentials")
+	default:
+		return nil, fmt.Errorf("unknown credential type: %q", f.Type)
+	}
+}
+
+// ComputeTokenSource returns a token source that fetches access tokens
+// from Google Compute Engine (GCE)'s metadata server. It's only valid to use
+// this token source if your program is running on a GCE instance.
+// If no account is specified, "default" is used.
+// If no scopes are specified, a set of default scopes are automatically granted.
+// 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 oauth2.ReuseTokenSource(nil, computeSource{account: account, scopes: scope})
+}
+
+type computeSource struct {
+	account string
+	scopes  []string
+}
+
+func (cs computeSource) Token() (*oauth2.Token, error) {
+	if !metadata.OnGCE() {
+		return nil, errors.New("oauth2/google: can't get a token from the metadata service; not running on GCE")
+	}
+	acct := cs.account
+	if acct == "" {
+		acct = "default"
+	}
+	tokenURI := "instance/service-accounts/" + acct + "/token"
+	if len(cs.scopes) > 0 {
+		v := url.Values{}
+		v.Set("scopes", strings.Join(cs.scopes, ","))
+		tokenURI = tokenURI + "?" + v.Encode()
+	}
+	tokenJSON, err := metadata.Get(tokenURI)
+	if err != nil {
+		return nil, err
+	}
+	var res struct {
+		AccessToken  string `json:"access_token"`
+		ExpiresInSec int    `json:"expires_in"`
+		TokenType    string `json:"token_type"`
+	}
+	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 == "" {
+		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),
+	}
+	// 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{}{
+		"oauth2.google.tokenSource":    "compute-metadata",
+		"oauth2.google.serviceAccount": acct,
+	}), nil
+}
diff --git a/vendor/golang.org/x/oauth2/google/jwt.go b/vendor/golang.org/x/oauth2/google/jwt.go
new file mode 100644
index 0000000000..b0fdb3a888
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/google/jwt.go
@@ -0,0 +1,74 @@
+// Copyright 2015 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 google
+
+import (
+	"crypto/rsa"
+	"fmt"
+	"time"
+
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/internal"
+	"golang.org/x/oauth2/jws"
+)
+
+// JWTAccessTokenSourceFromJSON uses a Google Developers service account JSON
+// key file to read the credentials that authorize and authenticate the
+// requests, and returns a TokenSource that does not use any OAuth2 flow but
+// instead creates a JWT and sends that as the access token.
+// The audience is typically a URL that specifies the scope of the credentials.
+//
+// Note that this is not a standard OAuth flow, but rather an
+// optimization supported by a few Google services.
+// Unless you know otherwise, you should use JWTConfigFromJSON instead.
+func JWTAccessTokenSourceFromJSON(jsonKey []byte, audience string) (oauth2.TokenSource, error) {
+	cfg, err := JWTConfigFromJSON(jsonKey)
+	if err != nil {
+		return nil, fmt.Errorf("google: could not parse JSON key: %v", err)
+	}
+	pk, err := internal.ParseKey(cfg.PrivateKey)
+	if err != nil {
+		return nil, fmt.Errorf("google: could not parse key: %v", err)
+	}
+	ts := &jwtAccessTokenSource{
+		email:    cfg.Email,
+		audience: audience,
+		pk:       pk,
+		pkID:     cfg.PrivateKeyID,
+	}
+	tok, err := ts.Token()
+	if err != nil {
+		return nil, err
+	}
+	return oauth2.ReuseTokenSource(tok, ts), nil
+}
+
+type jwtAccessTokenSource struct {
+	email, audience string
+	pk              *rsa.PrivateKey
+	pkID            string
+}
+
+func (ts *jwtAccessTokenSource) Token() (*oauth2.Token, error) {
+	iat := time.Now()
+	exp := iat.Add(time.Hour)
+	cs := &jws.ClaimSet{
+		Iss: ts.email,
+		Sub: ts.email,
+		Aud: ts.audience,
+		Iat: iat.Unix(),
+		Exp: exp.Unix(),
+	}
+	hdr := &jws.Header{
+		Algorithm: "RS256",
+		Typ:       "JWT",
+		KeyID:     string(ts.pkID),
+	}
+	msg, err := jws.Encode(hdr, cs, ts.pk)
+	if err != nil {
+		return nil, fmt.Errorf("google: could not encode JWT: %v", err)
+	}
+	return &oauth2.Token{AccessToken: msg, TokenType: "Bearer", Expiry: exp}, nil
+}
diff --git a/vendor/golang.org/x/oauth2/google/sdk.go b/vendor/golang.org/x/oauth2/google/sdk.go
new file mode 100644
index 0000000000..456224bc78
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/google/sdk.go
@@ -0,0 +1,201 @@
+// Copyright 2015 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 google
+
+import (
+	"bufio"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"os/user"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"time"
+
+	"golang.org/x/oauth2"
+)
+
+type sdkCredentials struct {
+	Data []struct {
+		Credential struct {
+			ClientID     string     `json:"client_id"`
+			ClientSecret string     `json:"client_secret"`
+			AccessToken  string     `json:"access_token"`
+			RefreshToken string     `json:"refresh_token"`
+			TokenExpiry  *time.Time `json:"token_expiry"`
+		} `json:"credential"`
+		Key struct {
+			Account string `json:"account"`
+			Scope   string `json:"scope"`
+		} `json:"key"`
+	}
+}
+
+// An SDKConfig provides access to tokens from an account already
+// authorized via the Google Cloud SDK.
+type SDKConfig struct {
+	conf         oauth2.Config
+	initialToken *oauth2.Token
+}
+
+// NewSDKConfig creates an SDKConfig for the given Google Cloud SDK
+// account. If account is empty, the account currently active in
+// Google Cloud SDK properties is used.
+// Google Cloud SDK credentials must be created by running `gcloud auth`
+// before using this function.
+// The Google Cloud SDK is available at https://cloud.google.com/sdk/.
+func NewSDKConfig(account string) (*SDKConfig, error) {
+	configPath, err := sdkConfigPath()
+	if err != nil {
+		return nil, fmt.Errorf("oauth2/google: error getting SDK config path: %v", err)
+	}
+	credentialsPath := filepath.Join(configPath, "credentials")
+	f, err := os.Open(credentialsPath)
+	if err != nil {
+		return nil, fmt.Errorf("oauth2/google: failed to load SDK credentials: %v", err)
+	}
+	defer f.Close()
+
+	var c sdkCredentials
+	if err := json.NewDecoder(f).Decode(&c); err != nil {
+		return nil, fmt.Errorf("oauth2/google: failed to decode SDK credentials from %q: %v", credentialsPath, err)
+	}
+	if len(c.Data) == 0 {
+		return nil, fmt.Errorf("oauth2/google: no credentials found in %q, run `gcloud auth login` to create one", credentialsPath)
+	}
+	if account == "" {
+		propertiesPath := filepath.Join(configPath, "properties")
+		f, err := os.Open(propertiesPath)
+		if err != nil {
+			return nil, fmt.Errorf("oauth2/google: failed to load SDK properties: %v", err)
+		}
+		defer f.Close()
+		ini, err := parseINI(f)
+		if err != nil {
+			return nil, fmt.Errorf("oauth2/google: failed to parse SDK properties %q: %v", propertiesPath, err)
+		}
+		core, ok := ini["core"]
+		if !ok {
+			return nil, fmt.Errorf("oauth2/google: failed to find [core] section in %v", ini)
+		}
+		active, ok := core["account"]
+		if !ok {
+			return nil, fmt.Errorf("oauth2/google: failed to find %q attribute in %v", "account", core)
+		}
+		account = active
+	}
+
+	for _, d := range c.Data {
+		if account == "" || d.Key.Account == account {
+			if d.Credential.AccessToken == "" && d.Credential.RefreshToken == "" {
+				return nil, fmt.Errorf("oauth2/google: no token available for account %q", account)
+			}
+			var expiry time.Time
+			if d.Credential.TokenExpiry != nil {
+				expiry = *d.Credential.TokenExpiry
+			}
+			return &SDKConfig{
+				conf: oauth2.Config{
+					ClientID:     d.Credential.ClientID,
+					ClientSecret: d.Credential.ClientSecret,
+					Scopes:       strings.Split(d.Key.Scope, " "),
+					Endpoint:     Endpoint,
+					RedirectURL:  "oob",
+				},
+				initialToken: &oauth2.Token{
+					AccessToken:  d.Credential.AccessToken,
+					RefreshToken: d.Credential.RefreshToken,
+					Expiry:       expiry,
+				},
+			}, nil
+		}
+	}
+	return nil, fmt.Errorf("oauth2/google: no such credentials for account %q", account)
+}
+
+// Client returns an HTTP client using Google Cloud SDK credentials to
+// authorize requests. The token will auto-refresh as necessary. The
+// underlying http.RoundTripper will be obtained using the provided
+// context. The returned client and its Transport should not be
+// modified.
+func (c *SDKConfig) Client(ctx context.Context) *http.Client {
+	return &http.Client{
+		Transport: &oauth2.Transport{
+			Source: c.TokenSource(ctx),
+		},
+	}
+}
+
+// TokenSource returns an oauth2.TokenSource that retrieve tokens from
+// Google Cloud SDK credentials using the provided context.
+// It will returns the current access token stored in the credentials,
+// and refresh it when it expires, but it won't update the credentials
+// with the new access token.
+func (c *SDKConfig) TokenSource(ctx context.Context) oauth2.TokenSource {
+	return c.conf.TokenSource(ctx, c.initialToken)
+}
+
+// Scopes are the OAuth 2.0 scopes the current account is authorized for.
+func (c *SDKConfig) Scopes() []string {
+	return c.conf.Scopes
+}
+
+func parseINI(ini io.Reader) (map[string]map[string]string, error) {
+	result := map[string]map[string]string{
+		"": {}, // root section
+	}
+	scanner := bufio.NewScanner(ini)
+	currentSection := ""
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if strings.HasPrefix(line, ";") {
+			// comment.
+			continue
+		}
+		if strings.HasPrefix(line, "[") && strings.HasSuffix(line, "]") {
+			currentSection = strings.TrimSpace(line[1 : len(line)-1])
+			result[currentSection] = map[string]string{}
+			continue
+		}
+		parts := strings.SplitN(line, "=", 2)
+		if len(parts) == 2 && parts[0] != "" {
+			result[currentSection][strings.TrimSpace(parts[0])] = strings.TrimSpace(parts[1])
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("error scanning ini: %v", err)
+	}
+	return result, nil
+}
+
+// sdkConfigPath tries to guess where the gcloud config is located.
+// It can be overridden during tests.
+var sdkConfigPath = func() (string, error) {
+	if runtime.GOOS == "windows" {
+		return filepath.Join(os.Getenv("APPDATA"), "gcloud"), nil
+	}
+	homeDir := guessUnixHomeDir()
+	if homeDir == "" {
+		return "", errors.New("unable to get current user home directory: os/user lookup failed; $HOME is empty")
+	}
+	return filepath.Join(homeDir, ".config", "gcloud"), nil
+}
+
+func guessUnixHomeDir() string {
+	// Prefer $HOME over user.Current due to glibc bug: golang.org/issue/13470
+	if v := os.Getenv("HOME"); v != "" {
+		return v
+	}
+	// Else, fall back to user.Current:
+	if u, err := user.Current(); err == nil {
+		return u.HomeDir
+	}
+	return ""
+}
diff --git a/vendor/golang.org/x/oauth2/jws/jws.go b/vendor/golang.org/x/oauth2/jws/jws.go
new file mode 100644
index 0000000000..683d2d271a
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/jws/jws.go
@@ -0,0 +1,182 @@
+// Copyright 2014 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 jws provides a partial implementation
+// of JSON Web Signature encoding and decoding.
+// It exists to support the golang.org/x/oauth2 package.
+//
+// See RFC 7515.
+//
+// Deprecated: this package is not intended for public use and might be
+// removed in the future. It exists for internal use only.
+// Please switch to another JWS package or copy this package into your own
+// source tree.
+package jws // import "golang.org/x/oauth2/jws"
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+)
+
+// ClaimSet contains information about the JWT signature including the
+// permissions being requested (scopes), the target of the token, the issuer,
+// the time the token was issued, and the lifetime of the token.
+type ClaimSet struct {
+	Iss   string `json:"iss"`             // email address of the client_id of the application making the access token request
+	Scope string `json:"scope,omitempty"` // space-delimited list of the permissions the application requests
+	Aud   string `json:"aud"`             // descriptor of the intended target of the assertion (Optional).
+	Exp   int64  `json:"exp"`             // the expiration time of the assertion (seconds since Unix epoch)
+	Iat   int64  `json:"iat"`             // the time the assertion was issued (seconds since Unix epoch)
+	Typ   string `json:"typ,omitempty"`   // token type (Optional).
+
+	// Email for which the application is requesting delegated access (Optional).
+	Sub string `json:"sub,omitempty"`
+
+	// The old name of Sub. Client keeps setting Prn to be
+	// complaint with legacy OAuth 2.0 providers. (Optional)
+	Prn string `json:"prn,omitempty"`
+
+	// 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:"-"`
+}
+
+func (c *ClaimSet) encode() (string, error) {
+	// Reverting time back for machines whose time is not perfectly in sync.
+	// If client machine's time is in the future according
+	// to Google servers, an access token will not be issued.
+	now := time.Now().Add(-10 * time.Second)
+	if c.Iat == 0 {
+		c.Iat = now.Unix()
+	}
+	if c.Exp == 0 {
+		c.Exp = now.Add(time.Hour).Unix()
+	}
+	if c.Exp < c.Iat {
+		return "", fmt.Errorf("jws: invalid Exp = %v; must be later than Iat = %v", c.Exp, c.Iat)
+	}
+
+	b, err := json.Marshal(c)
+	if err != nil {
+		return "", err
+	}
+
+	if len(c.PrivateClaims) == 0 {
+		return base64.RawURLEncoding.EncodeToString(b), nil
+	}
+
+	// Marshal private claim set and then append it to b.
+	prv, err := json.Marshal(c.PrivateClaims)
+	if err != nil {
+		return "", fmt.Errorf("jws: invalid map of private claims %v", c.PrivateClaims)
+	}
+
+	// Concatenate public and private claim JSON objects.
+	if !bytes.HasSuffix(b, []byte{'}'}) {
+		return "", fmt.Errorf("jws: invalid JSON %s", b)
+	}
+	if !bytes.HasPrefix(prv, []byte{'{'}) {
+		return "", fmt.Errorf("jws: invalid JSON %s", prv)
+	}
+	b[len(b)-1] = ','         // Replace closing curly brace with a comma.
+	b = append(b, prv[1:]...) // Append private claims.
+	return base64.RawURLEncoding.EncodeToString(b), nil
+}
+
+// Header represents the header for the signed JWS payloads.
+type Header struct {
+	// The algorithm used for signature.
+	Algorithm string `json:"alg"`
+
+	// Represents the token type.
+	Typ string `json:"typ"`
+
+	// The optional hint of which key is being used.
+	KeyID string `json:"kid,omitempty"`
+}
+
+func (h *Header) encode() (string, error) {
+	b, err := json.Marshal(h)
+	if err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(b), nil
+}
+
+// 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 {
+		// TODO(jbd): Provide more context about the error.
+		return nil, errors.New("jws: invalid token received")
+	}
+	decoded, err := base64.RawURLEncoding.DecodeString(s[1])
+	if err != nil {
+		return nil, err
+	}
+	c := &ClaimSet{}
+	err = json.NewDecoder(bytes.NewBuffer(decoded)).Decode(c)
+	return c, err
+}
+
+// Signer returns a signature for the given data.
+type Signer func(data []byte) (sig []byte, err error)
+
+// EncodeWithSigner encodes a header and claim set with the provided signer.
+func EncodeWithSigner(header *Header, c *ClaimSet, sg Signer) (string, error) {
+	head, err := header.encode()
+	if err != nil {
+		return "", err
+	}
+	cs, err := c.encode()
+	if err != nil {
+		return "", err
+	}
+	ss := fmt.Sprintf("%s.%s", head, cs)
+	sig, err := sg([]byte(ss))
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s.%s", ss, base64.RawURLEncoding.EncodeToString(sig)), nil
+}
+
+// Encode encodes a signed JWS with provided header and claim set.
+// 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()
+		h.Write(data)
+		return rsa.SignPKCS1v15(rand.Reader, key, crypto.SHA256, h.Sum(nil))
+	}
+	return EncodeWithSigner(header, c, sg)
+}
+
+// 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 {
+		return errors.New("jws: invalid token received, token must have 3 parts")
+	}
+
+	signedContent := parts[0] + "." + parts[1]
+	signatureString, err := base64.RawURLEncoding.DecodeString(parts[2])
+	if err != nil {
+		return err
+	}
+
+	h := sha256.New()
+	h.Write([]byte(signedContent))
+	return rsa.VerifyPKCS1v15(key, crypto.SHA256, h.Sum(nil), []byte(signatureString))
+}
diff --git a/vendor/golang.org/x/oauth2/jwt/jwt.go b/vendor/golang.org/x/oauth2/jwt/jwt.go
new file mode 100644
index 0000000000..b2bf18298b
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/jwt/jwt.go
@@ -0,0 +1,185 @@
+// Copyright 2014 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 jwt implements the OAuth 2.0 JSON Web Token flow, commonly
+// known as "two-legged OAuth 2.0".
+//
+// See: https://tools.ietf.org/html/draft-ietf-oauth-jwt-bearer-12
+package jwt
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/internal"
+	"golang.org/x/oauth2/jws"
+)
+
+var (
+	defaultGrantType = "urn:ietf:params:oauth:grant-type:jwt-bearer"
+	defaultHeader    = &jws.Header{Algorithm: "RS256", Typ: "JWT"}
+)
+
+// Config is the configuration for using JWT to fetch tokens,
+// commonly known as "two-legged OAuth 2.0".
+type Config struct {
+	// Email is the OAuth client identifier used when communicating with
+	// the configured OAuth provider.
+	Email string
+
+	// PrivateKey contains the contents of an RSA private key or the
+	// contents of a PEM file that contains a private key. The provided
+	// private key is used to sign JWT payloads.
+	// PEM containers with a passphrase are not supported.
+	// Use the following command to convert a PKCS 12 file into a PEM.
+	//
+	//    $ openssl pkcs12 -in key.p12 -out key.pem -nodes
+	//
+	PrivateKey []byte
+
+	// PrivateKeyID contains an optional hint indicating which key is being
+	// used.
+	PrivateKeyID string
+
+	// Subject is the optional user to impersonate.
+	Subject string
+
+	// Scopes optionally specifies a list of requested permission scopes.
+	Scopes []string
+
+	// TokenURL is the endpoint required to complete the 2-legged JWT flow.
+	TokenURL string
+
+	// Expires optionally specifies how long the token is valid for.
+	Expires time.Duration
+
+	// Audience optionally specifies the intended audience of the
+	// request.  If empty, the value of TokenURL is used as the
+	// intended audience.
+	Audience string
+
+	// 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{}
+
+	// UseIDToken optionally specifies whether ID token should be used instead
+	// of access token when the server returns both.
+	UseIDToken bool
+}
+
+// TokenSource returns a JWT TokenSource using the configuration
+// in c and the HTTP client from the provided context.
+func (c *Config) TokenSource(ctx context.Context) oauth2.TokenSource {
+	return oauth2.ReuseTokenSource(nil, jwtSource{ctx, c})
+}
+
+// Client returns an HTTP client wrapping the context's
+// HTTP transport and adding Authorization headers with tokens
+// obtained from c.
+//
+// The returned client and its Transport should not be modified.
+func (c *Config) Client(ctx context.Context) *http.Client {
+	return oauth2.NewClient(ctx, c.TokenSource(ctx))
+}
+
+// jwtSource is a source that always does a signed JWT request for a token.
+// It should typically be wrapped with a reuseTokenSource.
+type jwtSource struct {
+	ctx  context.Context
+	conf *Config
+}
+
+func (js jwtSource) Token() (*oauth2.Token, error) {
+	pk, err := internal.ParseKey(js.conf.PrivateKey)
+	if err != nil {
+		return nil, err
+	}
+	hc := oauth2.NewClient(js.ctx, nil)
+	claimSet := &jws.ClaimSet{
+		Iss:           js.conf.Email,
+		Scope:         strings.Join(js.conf.Scopes, " "),
+		Aud:           js.conf.TokenURL,
+		PrivateClaims: js.conf.PrivateClaims,
+	}
+	if subject := js.conf.Subject; subject != "" {
+		claimSet.Sub = subject
+		// prn is the old name of sub. Keep setting it
+		// to be compatible with legacy OAuth 2.0 providers.
+		claimSet.Prn = subject
+	}
+	if t := js.conf.Expires; t > 0 {
+		claimSet.Exp = time.Now().Add(t).Unix()
+	}
+	if aud := js.conf.Audience; aud != "" {
+		claimSet.Aud = aud
+	}
+	h := *defaultHeader
+	h.KeyID = js.conf.PrivateKeyID
+	payload, err := jws.Encode(&h, claimSet, pk)
+	if err != nil {
+		return nil, err
+	}
+	v := url.Values{}
+	v.Set("grant_type", defaultGrantType)
+	v.Set("assertion", payload)
+	resp, err := hc.PostForm(js.conf.TokenURL, v)
+	if err != nil {
+		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
+	}
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
+	}
+	if c := resp.StatusCode; c < 200 || c > 299 {
+		return nil, &oauth2.RetrieveError{
+			Response: resp,
+			Body:     body,
+		}
+	}
+	// 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
+	}
+	if err := json.Unmarshal(body, &tokenRes); err != nil {
+		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
+	}
+	token := &oauth2.Token{
+		AccessToken: tokenRes.AccessToken,
+		TokenType:   tokenRes.TokenType,
+	}
+	raw := make(map[string]interface{})
+	json.Unmarshal(body, &raw) // no error checks for optional fields
+	token = token.WithExtra(raw)
+
+	if secs := tokenRes.ExpiresIn; secs > 0 {
+		token.Expiry = time.Now().Add(time.Duration(secs) * time.Second)
+	}
+	if v := tokenRes.IDToken; v != "" {
+		// decode returned id token to get expiry
+		claimSet, err := jws.Decode(v)
+		if err != nil {
+			return nil, fmt.Errorf("oauth2: error decoding JWT token: %v", err)
+		}
+		token.Expiry = time.Unix(claimSet.Exp, 0)
+	}
+	if js.conf.UseIDToken {
+		if tokenRes.IDToken == "" {
+			return nil, fmt.Errorf("oauth2: response doesn't have JWT token")
+		}
+		token.AccessToken = tokenRes.IDToken
+	}
+	return token, nil
+}