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oauth2.go
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oauth2.go
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// Copyright 2014 The oauth2 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 provides support for making
// OAuth2 authorized and authenticated HTTP requests.
// It can additionally grant authorization with Bearer JWT.
package oauth2 // import "golang.org/x/oauth2"
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"io"
"io/ioutil"
"mime"
"net/http"
"net/url"
"strconv"
"strings"
"sync"
"time"
"golang.org/x/net/context"
)
// Context can be an golang.org/x/net.Context, or an App Engine Context.
// If you don't care and aren't running on App Engine, you may use NoContext.
type Context interface{}
// NoContext is the default context. If you're not running this code
// on App Engine or not using golang.org/x/net.Context to provide a custom
// HTTP client, you should use NoContext.
var NoContext Context = nil
// Config describes a typical 3-legged OAuth2 flow, with both the
// client application information and the server's endpoint URLs.
type Config struct {
// ClientID is the application's ID.
ClientID string
// ClientSecret is the application's secret.
ClientSecret string
// Endpoint contains the resource 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.
Endpoint Endpoint
// RedirectURL is the URL to redirect users going through
// the OAuth flow, after the resource owner's URLs.
RedirectURL string
// Scope specifies optional requested permissions.
Scopes []string
}
// A TokenSource is anything that can return a token.
type TokenSource interface {
// Token returns a token or an error.
// Token must be safe for concurrent use by multiple goroutines.
// The returned Token must not be modified.
Token() (*Token, error)
}
// Endpoint contains the OAuth 2.0 provider's authorization and token
// endpoint URLs.
type Endpoint struct {
AuthURL string
TokenURL string
}
var (
// AccessTypeOnline and AccessTypeOffline are options passed
// to the Options.AuthCodeURL method. They modify the
// "access_type" field that gets sent in the URL returned by
// AuthCodeURL.
//
// Online (the default if neither is specified) is the default.
// If your application needs to refresh access tokens when the
// user is not present at the browser, then use offline. This
// will result in your application obtaining a refresh token
// the first time your application exchanges an authorization
// code for a user.
AccessTypeOnline AuthCodeOption = setParam{"access_type", "online"}
AccessTypeOffline AuthCodeOption = setParam{"access_type", "offline"}
// ApprovalForce forces the users to view the consent dialog
// and confirm the permissions request at the URL returned
// from AuthCodeURL, even if they've already done so.
ApprovalForce AuthCodeOption = setParam{"approval_prompt", "force"}
)
type setParam struct{ k, v string }
func (p setParam) setValue(m url.Values) { m.Set(p.k, p.v) }
// An AuthCodeOption is passed to Config.AuthCodeURL.
type AuthCodeOption interface {
setValue(url.Values)
}
// 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-zero 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.
//
// Opts may include AccessTypeOnline or AccessTypeOffline, as well
// as ApprovalForce.
func (c *Config) AuthCodeURL(state string, opts ...AuthCodeOption) string {
var buf bytes.Buffer
buf.WriteString(c.Endpoint.AuthURL)
v := url.Values{
"response_type": {"code"},
"client_id": {c.ClientID},
"redirect_uri": condVal(c.RedirectURL),
"scope": condVal(strings.Join(c.Scopes, " ")),
"state": condVal(state),
}
for _, opt := range opts {
opt.setValue(v)
}
if strings.Contains(c.Endpoint.AuthURL, "?") {
buf.WriteByte('&')
} else {
buf.WriteByte('?')
}
buf.WriteString(v.Encode())
return buf.String()
}
// Exchange converts an authorization code into a token.
//
// It is used after a resource provider redirects the user back
// to the Redirect URI (the URL obtained from AuthCodeURL).
//
// The HTTP client to use is derived from the context. If nil,
// http.DefaultClient is used. See the Context type's documentation.
//
// The code will be in the *http.Request.FormValue("code"). Before
// calling Exchange, be sure to validate FormValue("state").
func (c *Config) Exchange(ctx Context, code string) (*Token, error) {
return retrieveToken(ctx, c, url.Values{
"grant_type": {"authorization_code"},
"code": {code},
"redirect_uri": condVal(c.RedirectURL),
"scope": condVal(strings.Join(c.Scopes, " ")),
})
}
// contextClientFunc is a func which tries to return an *http.Client
// given a Context value. If it returns an error, the search stops
// with that error. If it returns (nil, nil), the search continues
// down the list of registered funcs.
type contextClientFunc func(Context) (*http.Client, error)
var contextClientFuncs []contextClientFunc
func registerContextClientFunc(fn contextClientFunc) {
contextClientFuncs = append(contextClientFuncs, fn)
}
func contextClient(ctx Context) (*http.Client, error) {
for _, fn := range contextClientFuncs {
c, err := fn(ctx)
if err != nil {
return nil, err
}
if c != nil {
return c, nil
}
}
if xc, ok := ctx.(context.Context); ok {
if hc, ok := xc.Value(HTTPClient).(*http.Client); ok {
return hc, nil
}
}
return http.DefaultClient, nil
}
func contextTransport(ctx Context) http.RoundTripper {
hc, err := contextClient(ctx)
if err != nil {
// This is a rare error case (somebody using nil on App Engine),
// so I'd rather not everybody do an error check on this Client
// method. They can get the error that they're doing it wrong
// later, at client.Get/PostForm time.
return errorTransport{err}
}
return hc.Transport
}
// Client returns an HTTP client using the provided token.
// The token will auto-refresh as necessary. The underlying
// HTTP transport will be obtained using the provided context.
// The returned client and its Transport should not be modified.
func (c *Config) Client(ctx Context, t *Token) *http.Client {
return NewClient(ctx, c.TokenSource(ctx, t))
}
// TokenSource returns a TokenSource that returns t until t expires,
// automatically refreshing it as necessary using the provided context.
// See the the Context documentation.
//
// Most users will use Config.Client instead.
func (c *Config) TokenSource(ctx Context, t *Token) TokenSource {
nwn := &reuseTokenSource{t: t}
nwn.new = tokenRefresher{
ctx: ctx,
conf: c,
oldToken: &nwn.t,
}
return nwn
}
// tokenRefresher is a TokenSource that makes "grant_type"=="refresh_token"
// HTTP requests to renew a token using a RefreshToken.
type tokenRefresher struct {
ctx Context // used to get HTTP requests
conf *Config
oldToken **Token // pointer to old *Token w/ RefreshToken
}
func (tf tokenRefresher) Token() (*Token, error) {
t := *tf.oldToken
if t == nil {
return nil, errors.New("oauth2: attempted use of nil Token")
}
if t.RefreshToken == "" {
return nil, errors.New("oauth2: token expired and refresh token is not set")
}
return retrieveToken(tf.ctx, tf.conf, url.Values{
"grant_type": {"refresh_token"},
"refresh_token": {t.RefreshToken},
})
}
// reuseTokenSource is a TokenSource that holds a single token in memory
// and validates its expiry before each call to retrieve it with
// Token. If it's expired, it will be auto-refreshed using the
// new TokenSource.
//
// The first call to TokenRefresher must be SetToken.
type reuseTokenSource struct {
new TokenSource // called when t is expired.
mu sync.Mutex // guards t
t *Token
}
// 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.
func (s *reuseTokenSource) Token() (*Token, error) {
s.mu.Lock()
defer s.mu.Unlock()
if s.t.Valid() {
return s.t, nil
}
t, err := s.new.Token()
if err != nil {
return nil, err
}
s.t = t
return t, nil
}
func retrieveToken(ctx Context, c *Config, v url.Values) (*Token, error) {
hc, err := contextClient(ctx)
if err != nil {
return nil, err
}
v.Set("client_id", c.ClientID)
bustedAuth := !providerAuthHeaderWorks(c.Endpoint.TokenURL)
if bustedAuth && c.ClientSecret != "" {
v.Set("client_secret", c.ClientSecret)
}
req, err := http.NewRequest("POST", c.Endpoint.TokenURL, strings.NewReader(v.Encode()))
if err != nil {
return nil, err
}
req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
if !bustedAuth && c.ClientSecret != "" {
req.SetBasicAuth(c.ClientID, c.ClientSecret)
}
r, err := hc.Do(req)
if err != nil {
return nil, err
}
defer r.Body.Close()
body, err := ioutil.ReadAll(io.LimitReader(r.Body, 1<<20))
if err != nil {
return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
}
if code := r.StatusCode; code < 200 || code > 299 {
return nil, fmt.Errorf("oauth2: cannot fetch token: %v\nResponse: %s", r.Status, body)
}
var token *Token
content, _, _ := mime.ParseMediaType(r.Header.Get("Content-Type"))
switch content {
case "application/x-www-form-urlencoded", "text/plain":
vals, err := url.ParseQuery(string(body))
if err != nil {
return nil, err
}
token = &Token{
AccessToken: vals.Get("access_token"),
TokenType: vals.Get("token_type"),
RefreshToken: vals.Get("refresh_token"),
raw: vals,
}
e := vals.Get("expires_in")
if e == "" {
// TODO(jbd): Facebook's OAuth2 implementation is broken and
// returns expires_in field in expires. Remove the fallback to expires,
// when Facebook fixes their implementation.
e = vals.Get("expires")
}
expires, _ := strconv.Atoi(e)
if expires != 0 {
token.Expiry = time.Now().Add(time.Duration(expires) * time.Second)
}
default:
var tj tokenJSON
if err = json.Unmarshal(body, &tj); err != nil {
return nil, err
}
token = &Token{
AccessToken: tj.AccessToken,
TokenType: tj.TokenType,
RefreshToken: tj.RefreshToken,
Expiry: tj.expiry(),
raw: make(map[string]interface{}),
}
json.Unmarshal(body, &token.raw) // no error checks for optional fields
}
// Don't overwrite `RefreshToken` with an empty value
// if this was a token refreshing request.
if token.RefreshToken == "" {
token.RefreshToken = v.Get("refresh_token")
}
return token, nil
}
// tokenJSON is the struct representing the HTTP response from OAuth2
// providers returning a token in JSON form.
type tokenJSON struct {
AccessToken string `json:"access_token"`
TokenType string `json:"token_type"`
RefreshToken string `json:"refresh_token"`
ExpiresIn int32 `json:"expires_in"`
Expires int32 `json:"expires"` // broken Facebook spelling of expires_in
}
func (e *tokenJSON) expiry() (t time.Time) {
if v := e.ExpiresIn; v != 0 {
return time.Now().Add(time.Duration(v) * time.Second)
}
if v := e.Expires; v != 0 {
return time.Now().Add(time.Duration(v) * time.Second)
}
return
}
func condVal(v string) []string {
if v == "" {
return nil
}
return []string{v}
}
// providerAuthHeaderWorks reports whether the OAuth2 server identified by the tokenURL
// implements the OAuth2 spec correctly
// See https://code.google.com/p/goauth2/issues/detail?id=31 for background.
// In summary:
// - Reddit only accepts client secret in the Authorization header
// - Dropbox accepts either it in URL param or Auth header, but not both.
// - Google only accepts URL param (not spec compliant?), not Auth header
func providerAuthHeaderWorks(tokenURL string) bool {
if strings.HasPrefix(tokenURL, "https://accounts.google.com/") ||
strings.HasPrefix(tokenURL, "https://github.com/") ||
strings.HasPrefix(tokenURL, "https://api.instagram.com/") ||
strings.HasPrefix(tokenURL, "https://www.douban.com/") ||
strings.HasPrefix(tokenURL, "https://api.dropbox.com/") ||
strings.HasPrefix(tokenURL, "https://api.soundcloud.com/") ||
strings.HasPrefix(tokenURL, "https://www.linkedin.com/") {
// Some sites fail to implement the OAuth2 spec fully.
return false
}
// Assume the provider implements the spec properly
// otherwise. We can add more exceptions as they're
// discovered. We will _not_ be adding configurable hooks
// to this package to let users select server bugs.
return true
}
// 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.
var HTTPClient contextKey
// contextKey is just an empty struct. It exists so HTTPClient can be
// an immutable public variable with a unique type. It's immutable
// because nobody else can create a contextKey, being unexported.
type contextKey struct{}
// NewClient creates an *http.Client from a Context and TokenSource.
// The returned client is not valid beyond the lifetime of the context.
//
// As a special case, if src is nil, a non-OAuth2 client is returned
// using the provided context. This exists to support related OAuth2
// packages.
func NewClient(ctx Context, src TokenSource) *http.Client {
if src == nil {
c, err := contextClient(ctx)
if err != nil {
return &http.Client{Transport: errorTransport{err}}
}
return c
}
return &http.Client{
Transport: &Transport{
Base: contextTransport(ctx),
Source: ReuseTokenSource(nil, src),
},
}
}
// 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.
//
// ReuseTokenSource is typically used to reuse tokens from a cache
// (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
// 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.
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.
// Just build the equivalent one.
if rt, ok := src.(*reuseTokenSource); ok {
if t == nil {
// Just use it directly.
return rt
}
src = rt.new
}
return &reuseTokenSource{
t: t,
new: src,
}
}