TUN-8052: Update go to 1.21.5

Also update golang.org/x/net and google.golang.org/grpc to fix vulnerabilities,
although cloudflared is using them in a way that is not exposed to those risks

vendor/golang.org/x/oauth2/README.md

@@ -19,7 +19,7 @@ See pkg.go.dev for further documentation and examples.
 * [pkg.go.dev/golang.org/x/oauth2](https://pkg.go.dev/golang.org/x/oauth2)
 * [pkg.go.dev/golang.org/x/oauth2/google](https://pkg.go.dev/golang.org/x/oauth2/google)
 
-## Policy for new packages
+## Policy for new endpoints
 
 We no longer accept new provider-specific packages in this repo if all
 they do is add a single endpoint variable. If you just want to add a
@@ -29,8 +29,12 @@ package.
 
 ## Report Issues / Send Patches
 
-This repository uses Gerrit for code changes. To learn how to submit changes to
-this repository, see https://golang.org/doc/contribute.html.
-
 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:
+
+* 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.
+* The code owners are listed at [dev.golang.org/owners](https://dev.golang.org/owners#:~:text=x/oauth2).

vendor/golang.org/x/oauth2/deviceauth.go

@@ -0,0 +1,198 @@
+package oauth2
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"golang.org/x/oauth2/internal"
+)
+
+// https://datatracker.ietf.org/doc/html/rfc8628#section-3.5
+const (
+	errAuthorizationPending = "authorization_pending"
+	errSlowDown             = "slow_down"
+	errAccessDenied         = "access_denied"
+	errExpiredToken         = "expired_token"
+)
+
+// DeviceAuthResponse describes a successful RFC 8628 Device Authorization Response
+// https://datatracker.ietf.org/doc/html/rfc8628#section-3.2
+type DeviceAuthResponse struct {
+	// DeviceCode
+	DeviceCode string `json:"device_code"`
+	// UserCode is the code the user should enter at the verification uri
+	UserCode string `json:"user_code"`
+	// VerificationURI is where user should enter the user code
+	VerificationURI string `json:"verification_uri"`
+	// VerificationURIComplete (if populated) includes the user code in the verification URI. This is typically shown to the user in non-textual form, such as a QR code.
+	VerificationURIComplete string `json:"verification_uri_complete,omitempty"`
+	// Expiry is when the device code and user code expire
+	Expiry time.Time `json:"expires_in,omitempty"`
+	// Interval is the duration in seconds that Poll should wait between requests
+	Interval int64 `json:"interval,omitempty"`
+}
+
+func (d DeviceAuthResponse) MarshalJSON() ([]byte, error) {
+	type Alias DeviceAuthResponse
+	var expiresIn int64
+	if !d.Expiry.IsZero() {
+		expiresIn = int64(time.Until(d.Expiry).Seconds())
+	}
+	return json.Marshal(&struct {
+		ExpiresIn int64 `json:"expires_in,omitempty"`
+		*Alias
+	}{
+		ExpiresIn: expiresIn,
+		Alias:     (*Alias)(&d),
+	})
+
+}
+
+func (c *DeviceAuthResponse) UnmarshalJSON(data []byte) error {
+	type Alias DeviceAuthResponse
+	aux := &struct {
+		ExpiresIn int64 `json:"expires_in"`
+		// workaround misspelling of verification_uri
+		VerificationURL string `json:"verification_url"`
+		*Alias
+	}{
+		Alias: (*Alias)(c),
+	}
+	if err := json.Unmarshal(data, &aux); err != nil {
+		return err
+	}
+	if aux.ExpiresIn != 0 {
+		c.Expiry = time.Now().UTC().Add(time.Second * time.Duration(aux.ExpiresIn))
+	}
+	if c.VerificationURI == "" {
+		c.VerificationURI = aux.VerificationURL
+	}
+	return nil
+}
+
+// DeviceAuth returns a device auth struct which contains a device code
+// and authorization information provided for users to enter on another device.
+func (c *Config) DeviceAuth(ctx context.Context, opts ...AuthCodeOption) (*DeviceAuthResponse, error) {
+	// https://datatracker.ietf.org/doc/html/rfc8628#section-3.1
+	v := url.Values{
+		"client_id": {c.ClientID},
+	}
+	if len(c.Scopes) > 0 {
+		v.Set("scope", strings.Join(c.Scopes, " "))
+	}
+	for _, opt := range opts {
+		opt.setValue(v)
+	}
+	return retrieveDeviceAuth(ctx, c, v)
+}
+
+func retrieveDeviceAuth(ctx context.Context, c *Config, v url.Values) (*DeviceAuthResponse, error) {
+	if c.Endpoint.DeviceAuthURL == "" {
+		return nil, errors.New("endpoint missing DeviceAuthURL")
+	}
+
+	req, err := http.NewRequest("POST", c.Endpoint.DeviceAuthURL, strings.NewReader(v.Encode()))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("Accept", "application/json")
+
+	t := time.Now()
+	r, err := internal.ContextClient(ctx).Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20))
+	if err != nil {
+		return nil, fmt.Errorf("oauth2: cannot auth device: %v", err)
+	}
+	if code := r.StatusCode; code < 200 || code > 299 {
+		return nil, &RetrieveError{
+			Response: r,
+			Body:     body,
+		}
+	}
+
+	da := &DeviceAuthResponse{}
+	err = json.Unmarshal(body, &da)
+	if err != nil {
+		return nil, fmt.Errorf("unmarshal %s", err)
+	}
+
+	if !da.Expiry.IsZero() {
+		// Make a small adjustment to account for time taken by the request
+		da.Expiry = da.Expiry.Add(-time.Since(t))
+	}
+
+	return da, nil
+}
+
+// DeviceAccessToken polls the server to exchange a device code for a token.
+func (c *Config) DeviceAccessToken(ctx context.Context, da *DeviceAuthResponse, opts ...AuthCodeOption) (*Token, error) {
+	if !da.Expiry.IsZero() {
+		var cancel context.CancelFunc
+		ctx, cancel = context.WithDeadline(ctx, da.Expiry)
+		defer cancel()
+	}
+
+	// https://datatracker.ietf.org/doc/html/rfc8628#section-3.4
+	v := url.Values{
+		"client_id":   {c.ClientID},
+		"grant_type":  {"urn:ietf:params:oauth:grant-type:device_code"},
+		"device_code": {da.DeviceCode},
+	}
+	if len(c.Scopes) > 0 {
+		v.Set("scope", strings.Join(c.Scopes, " "))
+	}
+	for _, opt := range opts {
+		opt.setValue(v)
+	}
+
+	// "If no value is provided, clients MUST use 5 as the default."
+	// https://datatracker.ietf.org/doc/html/rfc8628#section-3.2
+	interval := da.Interval
+	if interval == 0 {
+		interval = 5
+	}
+
+	ticker := time.NewTicker(time.Duration(interval) * time.Second)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case <-ticker.C:
+			tok, err := retrieveToken(ctx, c, v)
+			if err == nil {
+				return tok, nil
+			}
+
+			e, ok := err.(*RetrieveError)
+			if !ok {
+				return nil, err
+			}
+			switch e.ErrorCode {
+			case errSlowDown:
+				// https://datatracker.ietf.org/doc/html/rfc8628#section-3.5
+				// "the interval MUST be increased by 5 seconds for this and all subsequent requests"
+				interval += 5
+				ticker.Reset(time.Duration(interval) * time.Second)
+			case errAuthorizationPending:
+				// Do nothing.
+			case errAccessDenied, errExpiredToken:
+				fallthrough
+			default:
+				return tok, err
+			}
+		}
+	}
+}

vendor/golang.org/x/oauth2/internal/client_appengine.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build appengine
-// +build appengine
 
 package internal
 

vendor/golang.org/x/oauth2/internal/oauth2.go

@@ -14,7 +14,7 @@ import (
 
 // ParseKey converts the binary contents of a private key file
 // to an *rsa.PrivateKey. It detects whether the private key is in a
-// PEM container or not. If so, it extracts the the private key
+// PEM container or not. If so, it extracts the private key
 // from PEM container before conversion. It only supports PEM
 // containers with no passphrase.
 func ParseKey(key []byte) (*rsa.PrivateKey, error) {

vendor/golang.org/x/oauth2/internal/token.go

@@ -18,6 +18,7 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 )
 
@@ -55,12 +56,18 @@ type Token struct {
 }
 
 // tokenJSON is the struct representing the HTTP response from OAuth2
-// providers returning a token in JSON form.
+// providers returning a token or error in JSON form.
+// https://datatracker.ietf.org/doc/html/rfc6749#section-5.1
 type tokenJSON struct {
 	AccessToken  string         `json:"access_token"`
 	TokenType    string         `json:"token_type"`
 	RefreshToken string         `json:"refresh_token"`
 	ExpiresIn    expirationTime `json:"expires_in"` // at least PayPal returns string, while most return number
+	// error fields
+	// https://datatracker.ietf.org/doc/html/rfc6749#section-5.2
+	ErrorCode        string `json:"error"`
+	ErrorDescription string `json:"error_description"`
+	ErrorURI         string `json:"error_uri"`
 }
 
 func (e *tokenJSON) expiry() (t time.Time) {
@@ -109,41 +116,60 @@ const (
 	AuthStyleInHeader AuthStyle = 2
 )
 
-// authStyleCache is the set of tokenURLs we've successfully used via
+// LazyAuthStyleCache is a backwards compatibility compromise to let Configs
+// have a lazily-initialized AuthStyleCache.
+//
+// The two users of this, oauth2.Config and oauth2/clientcredentials.Config,
+// both would ideally just embed an unexported AuthStyleCache but because both
+// were historically allowed to be copied by value we can't retroactively add an
+// uncopyable Mutex to them.
+//
+// We could use an atomic.Pointer, but that was added recently enough (in Go
+// 1.18) that we'd break Go 1.17 users where the tests as of 2023-08-03
+// still pass. By using an atomic.Value, it supports both Go 1.17 and
+// copying by value, even if that's not ideal.
+type LazyAuthStyleCache struct {
+	v atomic.Value // of *AuthStyleCache
+}
+
+func (lc *LazyAuthStyleCache) Get() *AuthStyleCache {
+	if c, ok := lc.v.Load().(*AuthStyleCache); ok {
+		return c
+	}
+	c := new(AuthStyleCache)
+	if !lc.v.CompareAndSwap(nil, c) {
+		c = lc.v.Load().(*AuthStyleCache)
+	}
+	return c
+}
+
+// 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
 // the set of OAuth2 servers a program contacts over time is fixed and
 // small.
-var authStyleCache struct {
-	sync.Mutex
-	m map[string]AuthStyle // keyed by tokenURL
-}
-
-// ResetAuthCache resets the global authentication style cache used
-// for AuthStyleUnknown token requests.
-func ResetAuthCache() {
-	authStyleCache.Lock()
-	defer authStyleCache.Unlock()
-	authStyleCache.m = nil
+type AuthStyleCache struct {
+	mu sync.Mutex
+	m  map[string]AuthStyle // keyed by tokenURL
 }
 
 // lookupAuthStyle reports which auth style we last used with tokenURL
 // when calling RetrieveToken and whether we have ever done so.
-func lookupAuthStyle(tokenURL string) (style AuthStyle, ok bool) {
-	authStyleCache.Lock()
-	defer authStyleCache.Unlock()
-	style, ok = authStyleCache.m[tokenURL]
+func (c *AuthStyleCache) lookupAuthStyle(tokenURL string) (style AuthStyle, ok bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	style, ok = c.m[tokenURL]
 	return
 }
 
 // setAuthStyle adds an entry to authStyleCache, documented above.
-func setAuthStyle(tokenURL string, v AuthStyle) {
-	authStyleCache.Lock()
-	defer authStyleCache.Unlock()
-	if authStyleCache.m == nil {
-		authStyleCache.m = make(map[string]AuthStyle)
+func (c *AuthStyleCache) setAuthStyle(tokenURL string, v AuthStyle) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.m == nil {
+		c.m = make(map[string]AuthStyle)
 	}
-	authStyleCache.m[tokenURL] = v
+	c.m[tokenURL] = v
 }
 
 // newTokenRequest returns a new *http.Request to retrieve a new token
@@ -183,10 +209,10 @@ func cloneURLValues(v url.Values) url.Values {
 	return v2
 }
 
-func RetrieveToken(ctx context.Context, clientID, clientSecret, tokenURL string, v url.Values, authStyle AuthStyle) (*Token, error) {
+func RetrieveToken(ctx context.Context, clientID, clientSecret, tokenURL string, v url.Values, authStyle AuthStyle, styleCache *AuthStyleCache) (*Token, error) {
 	needsAuthStyleProbe := authStyle == 0
 	if needsAuthStyleProbe {
-		if style, ok := lookupAuthStyle(tokenURL); ok {
+		if style, ok := styleCache.lookupAuthStyle(tokenURL); ok {
 			authStyle = style
 			needsAuthStyleProbe = false
 		} else {
@@ -216,7 +242,7 @@ func RetrieveToken(ctx context.Context, clientID, clientSecret, tokenURL string,
 		token, err = doTokenRoundTrip(ctx, req)
 	}
 	if needsAuthStyleProbe && err == nil {
-		setAuthStyle(tokenURL, authStyle)
+		styleCache.setAuthStyle(tokenURL, authStyle)
 	}
 	// Don't overwrite `RefreshToken` with an empty value
 	// if this was a token refreshing request.
@@ -236,21 +262,29 @@ func doTokenRoundTrip(ctx context.Context, req *http.Request) (*Token, error) {
 	if err != nil {
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
 	}
-	if code := r.StatusCode; code < 200 || code > 299 {
-		return nil, &RetrieveError{
-			Response: r,
-			Body:     body,
-		}
+
+	failureStatus := r.StatusCode < 200 || r.StatusCode > 299
+	retrieveError := &RetrieveError{
+		Response: r,
+		Body:     body,
+		// attempt to populate error detail below
 	}
 
 	var token *Token
 	content, _, _ := mime.ParseMediaType(r.Header.Get("Content-Type"))
 	switch content {
 	case "application/x-www-form-urlencoded", "text/plain":
+		// some endpoints return a query string
 		vals, err := url.ParseQuery(string(body))
 		if err != nil {
-			return nil, err
+			if failureStatus {
+				return nil, retrieveError
+			}
+			return nil, fmt.Errorf("oauth2: cannot parse response: %v", err)
 		}
+		retrieveError.ErrorCode = vals.Get("error")
+		retrieveError.ErrorDescription = vals.Get("error_description")
+		retrieveError.ErrorURI = vals.Get("error_uri")
 		token = &Token{
 			AccessToken:  vals.Get("access_token"),
 			TokenType:    vals.Get("token_type"),
@@ -265,8 +299,14 @@ func doTokenRoundTrip(ctx context.Context, req *http.Request) (*Token, error) {
 	default:
 		var tj tokenJSON
 		if err = json.Unmarshal(body, &tj); err != nil {
-			return nil, err
+			if failureStatus {
+				return nil, retrieveError
+			}
+			return nil, fmt.Errorf("oauth2: cannot parse json: %v", err)
 		}
+		retrieveError.ErrorCode = tj.ErrorCode
+		retrieveError.ErrorDescription = tj.ErrorDescription
+		retrieveError.ErrorURI = tj.ErrorURI
 		token = &Token{
 			AccessToken:  tj.AccessToken,
 			TokenType:    tj.TokenType,
@@ -276,17 +316,37 @@ func doTokenRoundTrip(ctx context.Context, req *http.Request) (*Token, error) {
 		}
 		json.Unmarshal(body, &token.Raw) // no error checks for optional fields
 	}
+	// according to spec, servers should respond status 400 in error case
+	// https://www.rfc-editor.org/rfc/rfc6749#section-5.2
+	// but some unorthodox servers respond 200 in error case
+	if failureStatus || retrieveError.ErrorCode != "" {
+		return nil, retrieveError
+	}
 	if token.AccessToken == "" {
 		return nil, errors.New("oauth2: server response missing access_token")
 	}
 	return token, nil
 }
 
+// mirrors oauth2.RetrieveError
 type RetrieveError struct {
-	Response *http.Response
-	Body     []byte
+	Response         *http.Response
+	Body             []byte
+	ErrorCode        string
+	ErrorDescription string
+	ErrorURI         string
 }
 
 func (r *RetrieveError) Error() string {
+	if r.ErrorCode != "" {
+		s := fmt.Sprintf("oauth2: %q", r.ErrorCode)
+		if r.ErrorDescription != "" {
+			s += fmt.Sprintf(" %q", r.ErrorDescription)
+		}
+		if r.ErrorURI != "" {
+			s += fmt.Sprintf(" %q", r.ErrorURI)
+		}
+		return s
+	}
 	return fmt.Sprintf("oauth2: cannot fetch token: %v\nResponse: %s", r.Response.Status, r.Body)
 }

vendor/golang.org/x/oauth2/oauth2.go

@@ -16,6 +16,7 @@ import (
 	"net/url"
 	"strings"
 	"sync"
+	"time"
 
 	"golang.org/x/oauth2/internal"
 )
@@ -57,6 +58,10 @@ type Config struct {
 
 	// Scope specifies optional requested permissions.
 	Scopes []string
+
+	// authStyleCache caches which auth style to use when Endpoint.AuthStyle is
+	// the zero value (AuthStyleAutoDetect).
+	authStyleCache internal.LazyAuthStyleCache
 }
 
 // A TokenSource is anything that can return a token.
@@ -70,8 +75,9 @@ type TokenSource interface {
 // Endpoint represents an OAuth 2.0 provider's authorization and token
 // endpoint URLs.
 type Endpoint struct {
-	AuthURL  string
-	TokenURL string
+	AuthURL       string
+	DeviceAuthURL string
+	TokenURL      string
 
 	// AuthStyle optionally specifies how the endpoint wants the
 	// client ID & client secret sent. The zero value means to
@@ -138,15 +144,19 @@ func SetAuthURLParam(key, value string) AuthCodeOption {
 // AuthCodeURL returns a URL to OAuth 2.0 provider's consent page
 // that asks for permissions for the required scopes explicitly.
 //
-// State is a token to protect the user from CSRF attacks. You must
-// always provide a non-empty string and validate that it matches the
-// the state query parameter on your redirect callback.
-// See http://tools.ietf.org/html/rfc6749#section-10.12 for more info.
+// State is an opaque value used by the client to maintain state between the
+// 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.
-// It can also be used to pass the PKCE challenge.
-// See https://www.oauth.com/oauth2-servers/pkce/ for more info.
+//
+// To protect against CSRF attacks, opts should include a PKCE challenge
+// (S256ChallengeOption). Not all servers support PKCE. An alternative is to
+// generate a random state parameter and verify it after exchange.
+// See https://datatracker.ietf.org/doc/html/rfc6749#section-10.12 (predating
+// PKCE), https://www.oauth.com/oauth2-servers/pkce/ and
+// https://www.ietf.org/archive/id/draft-ietf-oauth-v2-1-09.html#name-cross-site-request-forgery (describing both approaches)
 func (c *Config) AuthCodeURL(state string, opts ...AuthCodeOption) string {
 	var buf bytes.Buffer
 	buf.WriteString(c.Endpoint.AuthURL)
@@ -161,7 +171,6 @@ func (c *Config) AuthCodeURL(state string, opts ...AuthCodeOption) string {
 		v.Set("scope", strings.Join(c.Scopes, " "))
 	}
 	if state != "" {
-		// TODO(light): Docs say never to omit state; don't allow empty.
 		v.Set("state", state)
 	}
 	for _, opt := range opts {
@@ -206,10 +215,11 @@ func (c *Config) PasswordCredentialsToken(ctx context.Context, username, passwor
 // 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").
+// calling Exchange, be sure to validate FormValue("state") if you are
+// using it to protect against CSRF attacks.
 //
-// Opts may include the PKCE verifier code if previously used in AuthCodeURL.
-// See https://www.oauth.com/oauth2-servers/pkce/ for more info.
+// If using PKCE to protect against CSRF attacks, opts should include a
+// VerifierOption.
 func (c *Config) Exchange(ctx context.Context, code string, opts ...AuthCodeOption) (*Token, error) {
 	v := url.Values{
 		"grant_type": {"authorization_code"},
@@ -290,6 +300,8 @@ type reuseTokenSource struct {
 
 	mu sync.Mutex // guards t
 	t  *Token
+
+	expiryDelta time.Duration
 }
 
 // Token returns the current token if it's still valid, else will
@@ -305,6 +317,7 @@ func (s *reuseTokenSource) Token() (*Token, error) {
 	if err != nil {
 		return nil, err
 	}
+	t.expiryDelta = s.expiryDelta
 	s.t = t
 	return t, nil
 }
@@ -379,3 +392,30 @@ func ReuseTokenSource(t *Token, src TokenSource) TokenSource {
 		new: src,
 	}
 }
+
+// ReuseTokenSource 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 {
+	// Don't wrap a reuseTokenSource in itself. That would work,
+	// but cause an unnecessary number of mutex operations.
+	// Just build the equivalent one.
+	if rt, ok := src.(*reuseTokenSource); ok {
+		if t == nil {
+			// Just use it directly, but set the expiryDelta to earlyExpiry,
+			// so the behavior matches what the user expects.
+			rt.expiryDelta = earlyExpiry
+			return rt
+		}
+		src = rt.new
+	}
+	if t != nil {
+		t.expiryDelta = earlyExpiry
+	}
+	return &reuseTokenSource{
+		t:           t,
+		new:         src,
+		expiryDelta: earlyExpiry,
+	}
+}

vendor/golang.org/x/oauth2/pkce.go

@@ -0,0 +1,68 @@
+// 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 (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"net/url"
+)
+
+const (
+	codeChallengeKey       = "code_challenge"
+	codeChallengeMethodKey = "code_challenge_method"
+	codeVerifierKey        = "code_verifier"
+)
+
+// GenerateVerifier generates a PKCE code verifier with 32 octets of randomness.
+// 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).
+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
+	// base64url-encoded to produce a 43-octet URL-safe string to use as the
+	// code verifier."
+	// https://datatracker.ietf.org/doc/html/rfc7636#section-4.1
+	data := make([]byte, 32)
+	if _, err := rand.Read(data); err != nil {
+		panic(err)
+	}
+	return base64.RawURLEncoding.EncodeToString(data)
+}
+
+// VerifierOption returns a PKCE code verifier AuthCodeOption. It should be
+// passed to Config.Exchange or Config.DeviceAccessToken only.
+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.
+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
+// only.
+func S256ChallengeOption(verifier string) AuthCodeOption {
+	return challengeOption{
+		challenge_method: "S256",
+		challenge:        S256ChallengeFromVerifier(verifier),
+	}
+}
+
+type challengeOption struct{ challenge_method, challenge string }
+
+func (p challengeOption) setValue(m url.Values) {
+	m.Set(codeChallengeMethodKey, p.challenge_method)
+	m.Set(codeChallengeKey, p.challenge)
+}

vendor/golang.org/x/oauth2/token.go

@@ -16,10 +16,10 @@ import (
 	"golang.org/x/oauth2/internal"
 )
 
-// expiryDelta determines how earlier a token should be considered
+// defaultExpiryDelta determines how earlier a token should be considered
 // expired than its actual expiration time. It is used to avoid late
 // expirations due to client-server time mismatches.
-const expiryDelta = 10 * time.Second
+const defaultExpiryDelta = 10 * time.Second
 
 // Token represents the credentials used to authorize
 // the requests to access protected resources on the OAuth 2.0
@@ -52,6 +52,11 @@ type Token struct {
 	// raw optionally contains extra metadata from the server
 	// when updating a token.
 	raw interface{}
+
+	// expiryDelta is used to calculate when a token is considered
+	// expired, by subtracting from Expiry. If zero, defaultExpiryDelta
+	// is used.
+	expiryDelta time.Duration
 }
 
 // Type returns t.TokenType if non-empty, else "Bearer".
@@ -127,6 +132,11 @@ func (t *Token) expired() bool {
 	if t.Expiry.IsZero() {
 		return false
 	}
+
+	expiryDelta := defaultExpiryDelta
+	if t.expiryDelta != 0 {
+		expiryDelta = t.expiryDelta
+	}
 	return t.Expiry.Round(0).Add(-expiryDelta).Before(timeNow())
 }
 
@@ -154,7 +164,7 @@ func tokenFromInternal(t *internal.Token) *Token {
 // This token is then mapped from *internal.Token into an *oauth2.Token which is returned along
 // 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))
+	tk, err := internal.RetrieveToken(ctx, c.ClientID, c.ClientSecret, c.Endpoint.TokenURL, v, internal.AuthStyle(c.Endpoint.AuthStyle), c.authStyleCache.Get())
 	if err != nil {
 		if rErr, ok := err.(*internal.RetrieveError); ok {
 			return nil, (*RetrieveError)(rErr)
@@ -165,14 +175,31 @@ func retrieveToken(ctx context.Context, c *Config, v url.Values) (*Token, error)
 }
 
 // RetrieveError is the error returned when the token endpoint returns a
-// non-2XX HTTP status code.
+// non-2XX HTTP status code or populates RFC 6749's 'error' parameter.
+// https://datatracker.ietf.org/doc/html/rfc6749#section-5.2
 type RetrieveError struct {
 	Response *http.Response
 	// Body is the body that was consumed by reading Response.Body.
 	// It may be truncated.
 	Body []byte
+	// ErrorCode is RFC 6749's 'error' parameter.
+	ErrorCode string
+	// ErrorDescription is RFC 6749's 'error_description' parameter.
+	ErrorDescription string
+	// ErrorURI is RFC 6749's 'error_uri' parameter.
+	ErrorURI string
 }
 
 func (r *RetrieveError) Error() string {
+	if r.ErrorCode != "" {
+		s := fmt.Sprintf("oauth2: %q", r.ErrorCode)
+		if r.ErrorDescription != "" {
+			s += fmt.Sprintf(" %q", r.ErrorDescription)
+		}
+		if r.ErrorURI != "" {
+			s += fmt.Sprintf(" %q", r.ErrorURI)
+		}
+		return s
+	}
 	return fmt.Sprintf("oauth2: cannot fetch token: %v\nResponse: %s", r.Response.Status, r.Body)
 }