Additional OAuth2 providers (#1010)

* add google+

* sort signin oauth2 providers based on the name so order is always the same

* update auth tip for google+

* add gitlab provider

* add bitbucket provider (and some go fmt)

* add twitter provider

* add facebook provider

* add dropbox provider

* add openid connect provider incl. new format of tips section in "Add New Source"

* lower the amount of disk storage for each session to prevent issues while building cross platform (and disk overflow)

* imports according to goimport and code style

* make it possible to set custom urls to gitlab and github provider (only these could have a different host)

* split up oauth2 into multiple files

* small typo in comment

* fix indention

* fix indentation

* fix new line before external import

* fix layout of signin part

* update "broken" dependency

vendor/github.com/markbates/goth/providers/dropbox/dropbox.go

@@ -0,0 +1,191 @@
+// Package dropbox implements the OAuth2 protocol for authenticating users through Dropbox.
+package dropbox
+
+import (
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"strings"
+
+	"github.com/markbates/goth"
+	"golang.org/x/oauth2"
+	"fmt"
+)
+
+const (
+	authURL    = "https://www.dropbox.com/1/oauth2/authorize"
+	tokenURL   = "https://api.dropbox.com/1/oauth2/token"
+	accountURL = "https://api.dropbox.com/1/account/info"
+)
+
+// Provider is the implementation of `goth.Provider` for accessing Dropbox.
+type Provider struct {
+	ClientKey    string
+	Secret       string
+	CallbackURL  string
+	HTTPClient   *http.Client
+	config       *oauth2.Config
+	providerName string
+}
+
+// Session stores data during the auth process with Dropbox.
+type Session struct {
+	AuthURL string
+	Token   string
+}
+
+// New creates a new Dropbox provider and sets up important connection details.
+// You should always call `dropbox.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:        "dropbox",
+	}
+	p.config = newConfig(p, scopes)
+	return p
+}
+
+// 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
+}
+
+func (p *Provider) Client() *http.Client {
+	return goth.HTTPClientWithFallBack(p.HTTPClient)
+}
+
+// Debug is a no-op for the dropbox package.
+func (p *Provider) Debug(debug bool) {}
+
+// BeginAuth asks Dropbox for an authentication end-point.
+func (p *Provider) BeginAuth(state string) (goth.Session, error) {
+	return &Session{
+		AuthURL: p.config.AuthCodeURL(state),
+	}, nil
+}
+
+// FetchUser will go to Dropbox and access basic information about the user.
+func (p *Provider) FetchUser(session goth.Session) (goth.User, error) {
+	s := session.(*Session)
+	user := goth.User{
+		AccessToken: s.Token,
+		Provider:    p.Name(),
+	}
+
+	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)
+	}
+
+	req, err := http.NewRequest("GET", accountURL, nil)
+	if err != nil {
+		return user, err
+	}
+	req.Header.Set("Authorization", "Bearer "+s.Token)
+	resp, err := p.Client().Do(req)
+	if err != nil {
+		return user, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return user, fmt.Errorf("%s responded with a %d trying to fetch user information", p.providerName, resp.StatusCode)
+	}
+
+	err = userFromReader(resp.Body, &user)
+	return user, err
+}
+
+// UnmarshalSession wil unmarshal a JSON string into a session.
+func (p *Provider) UnmarshalSession(data string) (goth.Session, error) {
+	s := &Session{}
+	err := json.NewDecoder(strings.NewReader(data)).Decode(s)
+	return s, err
+}
+
+// GetAuthURL gets the URL set by calling the `BeginAuth` function on the Dropbox provider.
+func (s *Session) GetAuthURL() (string, error) {
+	if s.AuthURL == "" {
+		return "", errors.New("dropbox: missing AuthURL")
+	}
+	return s.AuthURL, nil
+}
+
+// Authorize the session with Dropbox and return the access token to be stored for future use.
+func (s *Session) Authorize(provider goth.Provider, params goth.Params) (string, error) {
+	p := provider.(*Provider)
+	token, err := p.config.Exchange(goth.ContextForClient(p.Client()), params.Get("code"))
+	if err != nil {
+		return "", err
+	}
+
+	if !token.Valid() {
+		return "", errors.New("Invalid token received from provider")
+	}
+
+	s.Token = token.AccessToken
+	return token.AccessToken, nil
+}
+
+// Marshal the session into a string
+func (s *Session) Marshal() string {
+	b, _ := json.Marshal(s)
+	return string(b)
+}
+
+func (s Session) String() string {
+	return s.Marshal()
+}
+
+func newConfig(p *Provider, scopes []string) *oauth2.Config {
+	c := &oauth2.Config{
+		ClientID:     p.ClientKey,
+		ClientSecret: p.Secret,
+		RedirectURL:  p.CallbackURL,
+		Endpoint: oauth2.Endpoint{
+			AuthURL:  authURL,
+			TokenURL: tokenURL,
+		},
+	}
+	return c
+}
+
+func userFromReader(r io.Reader, user *goth.User) error {
+	u := struct {
+		Name string `json:"display_name"`
+		NameDetails struct {
+			NickName string `json:"familiar_name"`
+		} `json:"name_details"`
+		Location string `json:"country"`
+		Email    string `json:"email"`
+	}{}
+	err := json.NewDecoder(r).Decode(&u)
+	if err != nil {
+		return err
+	}
+	user.Email = u.Email
+	user.Name = u.Name
+	user.NickName = u.NameDetails.NickName
+	user.UserID = u.Email // Dropbox doesn't provide a separate user ID
+	user.Location = u.Location
+	return nil
+}
+
+//RefreshToken refresh token is not provided by dropbox
+func (p *Provider) RefreshToken(refreshToken string) (*oauth2.Token, error) {
+	return nil, errors.New("Refresh token is not provided by dropbox")
+}
+
+//RefreshTokenAvailable refresh token is not provided by dropbox
+func (p *Provider) RefreshTokenAvailable() bool {
+	return false
+}