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

models/oauth2.go

@@ -0,0 +1,122 @@
+// Copyright 2017 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package models
+
+import (
+	"sort"
+	"code.gitea.io/gitea/modules/auth/oauth2"
+)
+
+// OAuth2Provider describes the display values of a single OAuth2 provider
+type OAuth2Provider struct {
+	Name              string
+	DisplayName       string
+	Image             string
+	CustomURLMapping  *oauth2.CustomURLMapping
+}
+
+// OAuth2Providers contains the map of registered OAuth2 providers in Gitea (based on goth)
+// key is used to map the OAuth2Provider with the goth provider type (also in LoginSource.OAuth2Config.Provider)
+// value is used to store display data
+var OAuth2Providers = map[string]OAuth2Provider{
+	"bitbucket": {Name: "bitbucket", DisplayName: "Bitbucket", Image: "/img/auth/bitbucket.png"},
+	"dropbox":   {Name: "dropbox", DisplayName: "Dropbox", Image: "/img/auth/dropbox.png"},
+	"facebook":  {Name: "facebook", DisplayName: "Facebook", Image: "/img/auth/facebook.png"},
+	"github": {Name: "github", DisplayName: "GitHub", Image: "/img/auth/github.png",
+		CustomURLMapping: &oauth2.CustomURLMapping{
+			TokenURL:   oauth2.GetDefaultTokenURL("github"),
+			AuthURL:    oauth2.GetDefaultAuthURL("github"),
+			ProfileURL: oauth2.GetDefaultProfileURL("github"),
+			EmailURL:   oauth2.GetDefaultEmailURL("github"),
+		},
+	},
+	"gitlab": {Name: "gitlab", DisplayName: "GitLab", Image: "/img/auth/gitlab.png",
+		CustomURLMapping: &oauth2.CustomURLMapping{
+			TokenURL:   oauth2.GetDefaultTokenURL("gitlab"),
+			AuthURL:    oauth2.GetDefaultAuthURL("gitlab"),
+			ProfileURL: oauth2.GetDefaultProfileURL("gitlab"),
+		},
+	},
+	"gplus":         {Name: "gplus", DisplayName: "Google+", Image: "/img/auth/google_plus.png"},
+	"openidConnect": {Name: "openidConnect", DisplayName: "OpenID Connect", Image: "/img/auth/openid_connect.png"},
+	"twitter":       {Name: "twitter", DisplayName: "Twitter", Image: "/img/auth/twitter.png"},
+}
+
+// OAuth2DefaultCustomURLMappings contains the map of default URL's for OAuth2 providers that are allowed to have custom urls
+// key is used to map the OAuth2Provider
+// value is the mapping as defined for the OAuth2Provider
+var OAuth2DefaultCustomURLMappings = map[string]*oauth2.CustomURLMapping {
+	"github": OAuth2Providers["github"].CustomURLMapping,
+	"gitlab": OAuth2Providers["gitlab"].CustomURLMapping,
+}
+
+// GetActiveOAuth2ProviderLoginSources returns all actived LoginOAuth2 sources
+func GetActiveOAuth2ProviderLoginSources() ([]*LoginSource, error) {
+	sources := make([]*LoginSource, 0, 1)
+	if err := x.UseBool().Find(&sources, &LoginSource{IsActived: true, Type: LoginOAuth2}); err != nil {
+		return nil, err
+	}
+	return sources, nil
+}
+
+// GetActiveOAuth2LoginSourceByName returns a OAuth2 LoginSource based on the given name
+func GetActiveOAuth2LoginSourceByName(name string) (*LoginSource, error) {
+	loginSource := &LoginSource{
+		Name:      name,
+		Type:      LoginOAuth2,
+		IsActived: true,
+	}
+
+	has, err := x.UseBool().Get(loginSource)
+	if !has || err != nil {
+		return nil, err
+	}
+
+	return loginSource, nil
+}
+
+// GetActiveOAuth2Providers returns the map of configured active OAuth2 providers
+// key is used as technical name (like in the callbackURL)
+// values to display
+func GetActiveOAuth2Providers() ([]string, map[string]OAuth2Provider, error) {
+	// Maybe also separate used and unused providers so we can force the registration of only 1 active provider for each type
+
+	loginSources, err := GetActiveOAuth2ProviderLoginSources()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var orderedKeys []string
+	providers := make(map[string]OAuth2Provider)
+	for _, source := range loginSources {
+		providers[source.Name] = OAuth2Providers[source.OAuth2().Provider]
+		orderedKeys = append(orderedKeys, source.Name)
+	}
+
+	sort.Strings(orderedKeys)
+
+	return orderedKeys, providers, nil
+}
+
+// InitOAuth2 initialize the OAuth2 lib and register all active OAuth2 providers in the library
+func InitOAuth2() {
+	oauth2.Init()
+	loginSources, _ := GetActiveOAuth2ProviderLoginSources()
+
+	for _, source := range loginSources {
+		oAuth2Config := source.OAuth2()
+		oauth2.RegisterProvider(source.Name, oAuth2Config.Provider, oAuth2Config.ClientID, oAuth2Config.ClientSecret, oAuth2Config.OpenIDConnectAutoDiscoveryURL, oAuth2Config.CustomURLMapping)
+	}
+}
+
+// wrapOpenIDConnectInitializeError is used to wrap the error but this cannot be done in modules/auth/oauth2
+// inside oauth2: import cycle not allowed models -> modules/auth/oauth2 -> models
+func wrapOpenIDConnectInitializeError(err error, providerName string, oAuth2Config *OAuth2Config) error {
+	if err != nil && "openidConnect" == oAuth2Config.Provider {
+		err = ErrOpenIDConnectInitialize{ProviderName: providerName, OpenIDConnectAutoDiscoveryURL: oAuth2Config.OpenIDConnectAutoDiscoveryURL, Cause: err}
+	}
+	return err
+}
+