1 files changed, 190 insertions, 0 deletions
diff --git a/services/auth/source/oauth2/providers.go b/services/auth/source/oauth2/providers.go
new file mode 100644
index 0000000..f2c1bb4
--- /dev/null
+++ b/services/auth/source/oauth2/providers.go
@@ -0,0 +1,190 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package oauth2
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"html"
+	"html/template"
+	"net/url"
+	"sort"
+
+	"code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/markbates/goth"
+)
+
+// Provider is an interface for describing a single OAuth2 provider
+type Provider interface {
+	Name() string
+	DisplayName() string
+	IconHTML(size int) template.HTML
+	CustomURLSettings() *CustomURLSettings
+}
+
+// GothProviderCreator provides a function to create a goth.Provider
+type GothProviderCreator interface {
+	CreateGothProvider(providerName, callbackURL string, source *Source) (goth.Provider, error)
+}
+
+// GothProvider is an interface for describing a single OAuth2 provider
+type GothProvider interface {
+	Provider
+	GothProviderCreator
+}
+
+// AuthSourceProvider provides a provider for an AuthSource. Multiple auth sources could use the same registered GothProvider
+// So each auth source should have its own DisplayName and IconHTML for display.
+// The Name is the GothProvider's name, to help to find the GothProvider to sign in.
+// The DisplayName is the auth source config's name, site admin set it on the admin page, the IconURL can also be set there.
+type AuthSourceProvider struct {
+	GothProvider
+	sourceName, iconURL string
+}
+
+func (p *AuthSourceProvider) Name() string {
+	return p.GothProvider.Name()
+}
+
+func (p *AuthSourceProvider) DisplayName() string {
+	return p.sourceName
+}
+
+func (p *AuthSourceProvider) IconHTML(size int) template.HTML {
+	if p.iconURL != "" {
+		img := fmt.Sprintf(`<img class="tw-object-contain tw-mr-2" width="%d" height="%d" src="%s" alt="%s">`,
+			size,
+			size,
+			html.EscapeString(p.iconURL), html.EscapeString(p.DisplayName()),
+		)
+		return template.HTML(img)
+	}
+	return p.GothProvider.IconHTML(size)
+}
+
+// Providers 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 AuthSource.OAuth2Config.Provider)
+// value is used to store display data
+var gothProviders = map[string]GothProvider{}
+
+// RegisterGothProvider registers a GothProvider
+func RegisterGothProvider(provider GothProvider) {
+	if _, has := gothProviders[provider.Name()]; has {
+		log.Fatal("Duplicate oauth2provider type provided: %s", provider.Name())
+	}
+	gothProviders[provider.Name()] = provider
+}
+
+// GetSupportedOAuth2Providers returns the map of unconfigured OAuth2 providers
+// key is used as technical name (like in the callbackURL)
+// values to display
+func GetSupportedOAuth2Providers() []Provider {
+	providers := make([]Provider, 0, len(gothProviders))
+
+	for _, provider := range gothProviders {
+		providers = append(providers, provider)
+	}
+	sort.Slice(providers, func(i, j int) bool {
+		return providers[i].Name() < providers[j].Name()
+	})
+	return providers
+}
+
+func CreateProviderFromSource(source *auth.Source) (Provider, error) {
+	oauth2Cfg, ok := source.Cfg.(*Source)
+	if !ok {
+		return nil, fmt.Errorf("invalid OAuth2 source config: %v", oauth2Cfg)
+	}
+	gothProv := gothProviders[oauth2Cfg.Provider]
+	return &AuthSourceProvider{GothProvider: gothProv, sourceName: source.Name, iconURL: oauth2Cfg.IconURL}, nil
+}
+
+// GetOAuth2Providers returns the list of configured OAuth2 providers
+func GetOAuth2Providers(ctx context.Context, isActive optional.Option[bool]) ([]Provider, error) {
+	authSources, err := db.Find[auth.Source](ctx, auth.FindSourcesOptions{
+		IsActive:  isActive,
+		LoginType: auth.OAuth2,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	providers := make([]Provider, 0, len(authSources))
+	for _, source := range authSources {
+		provider, err := CreateProviderFromSource(source)
+		if err != nil {
+			return nil, err
+		}
+		providers = append(providers, provider)
+	}
+
+	sort.Slice(providers, func(i, j int) bool {
+		return providers[i].Name() < providers[j].Name()
+	})
+
+	return providers, nil
+}
+
+// RegisterProviderWithGothic register a OAuth2 provider in goth lib
+func RegisterProviderWithGothic(providerName string, source *Source) error {
+	provider, err := createProvider(providerName, source)
+
+	if err == nil && provider != nil {
+		gothRWMutex.Lock()
+		defer gothRWMutex.Unlock()
+
+		goth.UseProviders(provider)
+	}
+
+	return err
+}
+
+// RemoveProviderFromGothic removes the given OAuth2 provider from the goth lib
+func RemoveProviderFromGothic(providerName string) {
+	gothRWMutex.Lock()
+	defer gothRWMutex.Unlock()
+
+	delete(goth.GetProviders(), providerName)
+}
+
+// ClearProviders clears all OAuth2 providers from the goth lib
+func ClearProviders() {
+	gothRWMutex.Lock()
+	defer gothRWMutex.Unlock()
+
+	goth.ClearProviders()
+}
+
+var ErrAuthSourceNotActivated = errors.New("auth source is not activated")
+
+// used to create different types of goth providers
+func createProvider(providerName string, source *Source) (goth.Provider, error) {
+	callbackURL := setting.AppURL + "user/oauth2/" + url.PathEscape(providerName) + "/callback"
+
+	var provider goth.Provider
+	var err error
+
+	p, ok := gothProviders[source.Provider]
+	if !ok {
+		return nil, ErrAuthSourceNotActivated
+	}
+
+	provider, err = p.CreateGothProvider(providerName, callbackURL, source)
+	if err != nil {
+		return provider, err
+	}
+
+	// always set the name if provider is created so we can support multiple setups of 1 provider
+	if provider != nil {
+		provider.SetName(providerName)
+	}
+
+	return provider, err
+}