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facebook.go
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facebook.go
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// Package facebook implements the OAuth2 protocol for authenticating users through Facebook.
// This package can be used as a reference implementation of an OAuth2 provider for Goth.
package facebook
import (
"bytes"
"crypto/hmac"
"crypto/sha256"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"strings"
"github.com/markbates/goth"
"golang.org/x/oauth2"
)
const (
authURL string = "https://www.facebook.com/dialog/oauth"
tokenURL string = "https://graph.facebook.com/oauth/access_token"
endpointProfile string = "https://graph.facebook.com/me?fields="
)
// New creates a new Facebook provider, and sets up important connection details.
// You should always call `facebook.New` to get a new Provider. Never try to create
// one manually.
func New(clientKey, secret, callbackURL string, scopes ...string) *Provider {
p := &Provider{
ClientKey: clientKey,
Secret: secret,
CallbackURL: callbackURL,
providerName: "facebook",
}
p.config = newConfig(p, scopes)
p.Fields = "email,first_name,last_name,link,about,id,name,picture,location"
return p
}
// Provider is the implementation of `goth.Provider` for accessing Facebook.
type Provider struct {
ClientKey string
Secret string
CallbackURL string
HTTPClient *http.Client
Fields string
config *oauth2.Config
providerName string
}
// Name is the name used to retrieve this provider later.
func (p *Provider) Name() string {
return p.providerName
}
// SetName is to update the name of the provider (needed in case of multiple providers of 1 type)
func (p *Provider) SetName(name string) {
p.providerName = name
}
// SetCustomFields sets the fields used to return information
// for a user.
//
// A list of available field values can be found at
// https://developers.facebook.com/docs/graph-api/reference/user
func (p *Provider) SetCustomFields(fields []string) *Provider {
p.Fields = strings.Join(fields, ",")
return p
}
func (p *Provider) Client() *http.Client {
return goth.HTTPClientWithFallBack(p.HTTPClient)
}
// Debug is a no-op for the facebook package.
func (p *Provider) Debug(debug bool) {}
// BeginAuth asks Facebook for an authentication end-point.
func (p *Provider) BeginAuth(state string) (goth.Session, error) {
authUrl := p.config.AuthCodeURL(state)
session := &Session{
AuthURL: authUrl,
}
return session, nil
}
// FetchUser will go to Facebook and access basic information about the user.
func (p *Provider) FetchUser(session goth.Session) (goth.User, error) {
sess := session.(*Session)
user := goth.User{
AccessToken: sess.AccessToken,
Provider: p.Name(),
ExpiresAt: sess.ExpiresAt,
}
if user.AccessToken == "" {
// data is not yet retrieved since accessToken is still empty
return user, fmt.Errorf("%s cannot get user information without accessToken", p.providerName)
}
// always add appsecretProof to make calls more protected
// https://github.com/markbates/goth/issues/96
// https://developers.facebook.com/docs/graph-api/securing-requests
hash := hmac.New(sha256.New, []byte(p.Secret))
hash.Write([]byte(sess.AccessToken))
appsecretProof := hex.EncodeToString(hash.Sum(nil))
reqUrl := fmt.Sprint(
endpointProfile,
p.Fields,
"&access_token=",
url.QueryEscape(sess.AccessToken),
"&appsecret_proof=",
appsecretProof,
)
response, err := p.Client().Get(reqUrl)
if err != nil {
return user, err
}
defer response.Body.Close()
if response.StatusCode != http.StatusOK {
return user, fmt.Errorf("%s responded with a %d trying to fetch user information", p.providerName, response.StatusCode)
}
bits, err := ioutil.ReadAll(response.Body)
if err != nil {
return user, err
}
err = json.NewDecoder(bytes.NewReader(bits)).Decode(&user.RawData)
if err != nil {
return user, err
}
err = userFromReader(bytes.NewReader(bits), &user)
return user, err
}
func userFromReader(reader io.Reader, user *goth.User) error {
u := struct {
ID string `json:"id"`
Email string `json:"email"`
About string `json:"about"`
Name string `json:"name"`
FirstName string `json:"first_name"`
LastName string `json:"last_name"`
Link string `json:"link"`
Picture struct {
Data struct {
URL string `json:"url"`
} `json:"data"`
} `json:"picture"`
Location struct {
Name string `json:"name"`
} `json:"location"`
}{}
err := json.NewDecoder(reader).Decode(&u)
if err != nil {
return err
}
user.Name = u.Name
user.FirstName = u.FirstName
user.LastName = u.LastName
user.NickName = u.Name
user.Email = u.Email
user.Description = u.About
user.AvatarURL = u.Picture.Data.URL
user.UserID = u.ID
user.Location = u.Location.Name
return err
}
func newConfig(provider *Provider, scopes []string) *oauth2.Config {
c := &oauth2.Config{
ClientID: provider.ClientKey,
ClientSecret: provider.Secret,
RedirectURL: provider.CallbackURL,
Endpoint: oauth2.Endpoint{
AuthURL: authURL,
TokenURL: tokenURL,
},
Scopes: []string{
"email",
},
}
defaultScopes := map[string]struct{}{
"email": {},
}
for _, scope := range scopes {
if _, exists := defaultScopes[scope]; !exists {
c.Scopes = append(c.Scopes, scope)
}
}
return c
}
//RefreshToken refresh token is not provided by facebook
func (p *Provider) RefreshToken(refreshToken string) (*oauth2.Token, error) {
return nil, errors.New("Refresh token is not provided by facebook")
}
//RefreshTokenAvailable refresh token is not provided by facebook
func (p *Provider) RefreshTokenAvailable() bool {
return false
}