Pre-register OAuth2 applications for git credential helpers (#26291)

This PR is an extended implementation of #25189 and builds upon the
proposal by @hickford in #25653, utilizing some ideas proposed
internally by @wxiaoguang.

Mainly, this PR consists of a mechanism to pre-register OAuth2
applications on startup, which can be enabled or disabled by modifying
the `[oauth2].DEFAULT_APPLICATIONS` parameter in app.ini. The OAuth2
applications registered this way are being marked as "locked" and
neither be deleted nor edited over UI to prevent confusing/unexpected
behavior. Instead, they're being removed if no longer enabled in config.


![grafik](https://github.com/go-gitea/gitea/assets/47871822/81a78b1c-4b68-40a7-9e99-c272ebb8f62e)

The implemented mechanism can also be used to pre-register other OAuth2
applications in the future, if wanted.

Co-authored-by: hickford <mirth.hickford@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

---------

Co-authored-by: M Hickford <mirth.hickford@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

custom/conf/app.example.ini

@@ -544,6 +544,11 @@ ENABLE = true
 ;;
 ;; Maximum length of oauth2 token/cookie stored on server
 ;MAX_TOKEN_LENGTH = 32767
+;;
+;; Pre-register OAuth2 applications for some universally useful services
+;; * https://github.com/hickford/git-credential-oauth
+;; * https://github.com/git-ecosystem/git-credential-manager
+;DEFAULT_APPLICATIONS = git-credential-oauth, git-credential-manager
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

docs/content/administration/config-cheat-sheet.en-us.md

@@ -1100,6 +1100,7 @@ This section only does "set" config, a removed config key from this section won'
 - `JWT_SECRET_URI`: **_empty_**: Instead of defining JWT_SECRET in the configuration, this configuration option can be used to give Gitea a path to a file that contains the secret (example value: `file:/etc/gitea/oauth2_jwt_secret`)
 - `JWT_SIGNING_PRIVATE_KEY_FILE`: **jwt/private.pem**: Private key file path used to sign OAuth2 tokens. The path is relative to `APP_DATA_PATH`. This setting is only needed if `JWT_SIGNING_ALGORITHM` is set to `RS256`, `RS384`, `RS512`, `ES256`, `ES384` or `ES512`. The file must contain a RSA or ECDSA private key in the PKCS8 format. If no key exists a 4096 bit key will be created for you.
 - `MAX_TOKEN_LENGTH`: **32767**: Maximum length of token/cookie to accept from OAuth2 provider
+- `DEFAULT_APPLICATIONS`: **git-credential-oauth, git-credential-manager**: Pre-register OAuth applications for some services on startup. See the [OAuth2 documentation](/development/oauth2-provider.md) for the list of available options.
 
 ## i18n (`i18n`)
 

docs/content/development/oauth2-provider.en-us.md

@@ -78,6 +78,17 @@ Gitea token scopes are as follows:
 |     **read:user** | Grants read access to user operations, such as getting user repo subscriptions and user settings.                                                    |
 |     **write:user** | Grants read/write/delete access to user operations, such as updating user repo subscriptions, followed users, and user settings.                     |
 
+## Pre-configured Applications
+
+Gitea creates OAuth applications for the following services by default on startup, as we assume that these are universally useful.
+
+|Application|Description|Client ID|
+|-----------|-----------|---------|
+|[git-credential-oauth](https://github.com/hickford/git-credential-oauth)|Git credential helper|`a4792ccc-144e-407e-86c9-5e7d8d9c3269`|
+|[Git Credential Manager](https://github.com/git-ecosystem/git-credential-manager)|Git credential helper|`e90ee53c-94e2-48ac-9358-a874fb9e0662`|
+
+To prevent unexpected behavior, they are being displayed as locked in the UI and their creation can instead be controlled by the `DEFAULT_APPLICATIONS` parameter in `app.ini`.
+
 ## Client types
 
 Gitea supports both confidential and public client types, [as defined by RFC 6749](https://datatracker.ietf.org/doc/html/rfc6749#section-2.1).

models/auth/oauth2.go

@@ -13,6 +13,8 @@ import (
 	"strings"
 
 	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/container"
+	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"
 
@@ -46,6 +48,83 @@ func init() {
 	db.RegisterModel(new(OAuth2Grant))
 }
 
+type BuiltinOAuth2Application struct {
+	ConfigName   string
+	DisplayName  string
+	RedirectURIs []string
+}
+
+func BuiltinApplications() map[string]*BuiltinOAuth2Application {
+	m := make(map[string]*BuiltinOAuth2Application)
+	m["a4792ccc-144e-407e-86c9-5e7d8d9c3269"] = &BuiltinOAuth2Application{
+		ConfigName:   "git-credential-oauth",
+		DisplayName:  "git-credential-oauth",
+		RedirectURIs: []string{"http://127.0.0.1", "https://127.0.0.1"},
+	}
+	m["e90ee53c-94e2-48ac-9358-a874fb9e0662"] = &BuiltinOAuth2Application{
+		ConfigName:   "git-credential-manager",
+		DisplayName:  "Git Credential Manager",
+		RedirectURIs: []string{"http://127.0.0.1", "https://127.0.0.1"},
+	}
+	return m
+}
+
+func Init(ctx context.Context) error {
+	builtinApps := BuiltinApplications()
+	var builtinAllClientIDs []string
+	for clientID := range builtinApps {
+		builtinAllClientIDs = append(builtinAllClientIDs, clientID)
+	}
+
+	var registeredApps []*OAuth2Application
+	if err := db.GetEngine(ctx).In("client_id", builtinAllClientIDs).Find(&registeredApps); err != nil {
+		return err
+	}
+
+	clientIDsToAdd := container.Set[string]{}
+	for _, configName := range setting.OAuth2.DefaultApplications {
+		found := false
+		for clientID, builtinApp := range builtinApps {
+			if builtinApp.ConfigName == configName {
+				clientIDsToAdd.Add(clientID) // add all user-configured apps to the "add" list
+				found = true
+			}
+		}
+		if !found {
+			return fmt.Errorf("unknown oauth2 application: %q", configName)
+		}
+	}
+	clientIDsToDelete := container.Set[string]{}
+	for _, app := range registeredApps {
+		if !clientIDsToAdd.Contains(app.ClientID) {
+			clientIDsToDelete.Add(app.ClientID) // if a registered app is not in the "add" list, it should be deleted
+		}
+	}
+	for _, app := range registeredApps {
+		clientIDsToAdd.Remove(app.ClientID) // no need to re-add existing (registered) apps, so remove them from the set
+	}
+
+	for _, app := range registeredApps {
+		if clientIDsToDelete.Contains(app.ClientID) {
+			if err := deleteOAuth2Application(ctx, app.ID, 0); err != nil {
+				return err
+			}
+		}
+	}
+	for clientID := range clientIDsToAdd {
+		builtinApp := builtinApps[clientID]
+		if err := db.Insert(ctx, &OAuth2Application{
+			Name:         builtinApp.DisplayName,
+			ClientID:     clientID,
+			RedirectURIs: builtinApp.RedirectURIs,
+		}); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // TableName sets the table name to `oauth2_application`
 func (app *OAuth2Application) TableName() string {
 	return "oauth2_application"
@@ -205,6 +284,10 @@ func UpdateOAuth2Application(opts UpdateOAuth2ApplicationOptions) (*OAuth2Applic
 	if app.UID != opts.UserID {
 		return nil, fmt.Errorf("UID mismatch")
 	}
+	builtinApps := BuiltinApplications()
+	if _, builtin := builtinApps[app.ClientID]; builtin {
+		return nil, fmt.Errorf("failed to edit OAuth2 application: application is locked: %s", app.ClientID)
+	}
 
 	app.Name = opts.Name
 	app.RedirectURIs = opts.RedirectURIs
@@ -261,6 +344,14 @@ func DeleteOAuth2Application(id, userid int64) error {
 		return err
 	}
 	defer committer.Close()
+	app, err := GetOAuth2ApplicationByID(ctx, id)
+	if err != nil {
+		return err
+	}
+	builtinApps := BuiltinApplications()
+	if _, builtin := builtinApps[app.ClientID]; builtin {
+		return fmt.Errorf("failed to delete OAuth2 application: application is locked: %s", app.ClientID)
+	}
 	if err := deleteOAuth2Application(ctx, id, userid); err != nil {
 		return err
 	}

modules/setting/oauth2.go

@@ -100,6 +100,7 @@ var OAuth2 = struct {
 	JWTSecretBase64            string `ini:"JWT_SECRET"`
 	JWTSigningPrivateKeyFile   string `ini:"JWT_SIGNING_PRIVATE_KEY_FILE"`
 	MaxTokenLength             int
+	DefaultApplications        []string
 }{
 	Enable:                     true,
 	AccessTokenExpirationTime:  3600,
@@ -108,6 +109,7 @@ var OAuth2 = struct {
 	JWTSigningAlgorithm:        "RS256",
 	JWTSigningPrivateKeyFile:   "jwt/private.pem",
 	MaxTokenLength:             math.MaxInt16,
+	DefaultApplications:        []string{"git-credential-oauth", "git-credential-manager"},
 }
 
 func loadOAuth2From(rootCfg ConfigProvider) {

options/locale/locale_en-US.ini

@@ -93,6 +93,7 @@ edit = Edit
 
 enabled = Enabled
 disabled = Disabled
+locked = Locked
 
 copy = Copy
 copy_url = Copy URL
@@ -850,6 +851,7 @@ oauth2_client_secret_hint = The secret will not be shown again after you leave o
 oauth2_application_edit = Edit
 oauth2_application_create_description = OAuth2 applications gives your third-party application access to user accounts on this instance.
 oauth2_application_remove_description = Removing an OAuth2 application will prevent it from accessing authorized user accounts on this instance. Continue?
+oauth2_application_locked = Gitea pre-registers some OAuth2 applications on startup if enabled in config. To prevent unexpected bahavior, these can neither be edited nor removed. Please refer to the OAuth2 documentation for more information.
 
 authorized_oauth2_applications = Authorized OAuth2 Applications
 authorized_oauth2_applications_description = You have granted access to your personal Gitea account to these third party applications. Please revoke access for applications you no longer need.

routers/init.go

@@ -10,6 +10,7 @@ import (
 
 	"code.gitea.io/gitea/models"
 	asymkey_model "code.gitea.io/gitea/models/asymkey"
+	authmodel "code.gitea.io/gitea/models/auth"
 	"code.gitea.io/gitea/modules/cache"
 	"code.gitea.io/gitea/modules/eventsource"
 	"code.gitea.io/gitea/modules/git"
@@ -138,6 +139,7 @@ func InitWebInstalled(ctx context.Context) {
 	mustInit(oauth2.Init)
 
 	mustInitCtx(ctx, models.Init)
+	mustInitCtx(ctx, authmodel.Init)
 	mustInit(repo_service.Init)
 
 	// Booting long running goroutines.

routers/web/admin/applications.go

@@ -39,7 +39,7 @@ func Applications(ctx *context.Context) {
 		return
 	}
 	ctx.Data["Applications"] = apps
-
+	ctx.Data["BuiltinApplications"] = auth.BuiltinApplications()
 	ctx.HTML(http.StatusOK, tplSettingsApplications)
 }
 

routers/web/repo/http.go

@@ -147,7 +147,7 @@ func httpBase(ctx *context.Context) *serviceHandler {
 		// rely on the results of Contexter
 		if !ctx.IsSigned {
 			// TODO: support digit auth - which would be Authorization header with digit
-			ctx.Resp.Header().Set("WWW-Authenticate", "Basic realm=\".\"")
+			ctx.Resp.Header().Set("WWW-Authenticate", `Basic realm="Gitea"`)
 			ctx.Error(http.StatusUnauthorized)
 			return nil
 		}

templates/user/settings/applications_oauth2_list.tmpl

@@ -4,7 +4,7 @@
 			{{.locale.Tr "settings.oauth2_application_create_description"}}
 		</div>
 		{{range .Applications}}
-			<div class="flex-item">
+			<div class="flex-item flex-item-center">
 				<div class="flex-item-leading">
 					{{svg "octicon-apps" 32}}
 				</div>
@@ -15,16 +15,21 @@
 						<span class="ui label">{{.ClientID}}</span>
 					</div>
 				</div>
+				{{$isBuiltin := and $.BuiltinApplications (index $.BuiltinApplications .ClientID)}}
 				<div class="flex-item-trailing">
-					<a href="{{$.Link}}/oauth2/{{.ID}}" class="ui primary tiny button">
-						{{svg "octicon-pencil" 16 "gt-mr-2"}}
-						{{$.locale.Tr "settings.oauth2_application_edit"}}
-					</a>
-					<button class="ui red tiny button delete-button" data-modal-id="remove-gitea-oauth2-application"
-							data-url="{{$.Link}}/oauth2/{{.ID}}/delete">
-						{{svg "octicon-trash" 16 "gt-mr-2"}}
-						{{$.locale.Tr "settings.delete_key"}}
-					</button>
+					{{if $isBuiltin}}
+						<span class="ui basic label" data-tooltip-content="{{$.locale.Tr "settings.oauth2_application_locked"}}">{{ctx.Locale.Tr "locked"}}</span>
+					{{else}}
+						<a href="{{$.Link}}/oauth2/{{.ID}}" class="ui primary tiny button">
+							{{svg "octicon-pencil" 16 "gt-mr-2"}}
+							{{$.locale.Tr "settings.oauth2_application_edit"}}
+						</a>
+						<button class="ui red tiny button delete-button" data-modal-id="remove-gitea-oauth2-application"
+								data-url="{{$.Link}}/oauth2/{{.ID}}/delete">
+							{{svg "octicon-trash" 16 "gt-mr-2"}}
+							{{$.locale.Tr "settings.delete_key"}}
+						</button>
+					{{end}}
 				</div>
 			</div>
 		{{end}}