OAuth2 auto-register (#5123)

* Refactored handleOAuth2SignIn in routers/user/auth.go

The function handleOAuth2SignIn was called twice but some code path could only
be reached by one of the invocations. Moved the unnecessary code path out of
handleOAuth2SignIn.


* Refactored user creation

There was common code to create a user and display the correct error message.
And after the creation the only user should be an admin and if enabled a
confirmation email should be sent. This common code is now abstracted into
two functions and a helper function to call both.

* Added auto-register for OAuth2 users

If enabled new OAuth2 users will be registered with their OAuth2 details.
The UserID, Name and Email fields from the gothUser are used.
Therefore the OpenID Connect provider needs additional scopes to return
the coresponding claims.

* Added error for missing fields in OAuth2 response

* Linking and auto linking on oauth2 registration

* Set default username source to nickname

* Add automatic oauth2 scopes for github and google

* Add hint to change the openid connect scopes if fields are missing

* Extend info about auto linking security risk

Co-authored-by: Viktor Kuzmin <kvaster@gmail.com>
Signed-off-by: Martin Michaelis <code@mgjm.de>

Author: mgjm

custom/conf/app.example.ini

@@ -617,6 +617,30 @@ WHITELISTED_URIS =
 ; Example value: loadaverage.org/badguy stackexchange.com/.*spammer
 BLACKLISTED_URIS =
 
+[oauth2_client]
+; Whether a new auto registered oauth2 user needs to confirm their email.
+; Do not include to use the REGISTER_EMAIL_CONFIRM setting from the `[service]` section.
+REGISTER_EMAIL_CONFIRM =
+; Scopes for the openid connect oauth2 provider (seperated by space, the openid scope is implicitly added).
+; Typical values are profile and email.
+; For more information about the possible values see https://openid.net/specs/openid-connect-core-1_0.html#ScopeClaims
+OPENID_CONNECT_SCOPES =
+; Automatically create user accounts for new oauth2 users.
+ENABLE_AUTO_REGISTRATION = false
+; The source of the username for new oauth2 accounts:
+; userid = use the userid / sub attribute
+; nickname = use the nickname attribute
+; email = use the username part of the email attribute
+USERNAME = nickname
+; Update avatar if available from oauth2 provider.
+; Update will be performed on each login.
+UPDATE_AVATAR = false
+; How to handle if an account / email already exists:
+; disabled = show an error
+; login = show an account linking login
+; auto = link directly with the account
+ACCOUNT_LINKING = disabled
+
 [service]
 ; Time limit to confirm account/email registration
 ACTIVE_CODE_LIVE_MINUTES = 180

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -429,6 +429,21 @@ relation to port exhaustion.
 - `BLACKLISTED_URIS`: **\<empty\>**: If non-empty, list of POSIX regex patterns matching
    OpenID URI's to block.
 
+## OAuth2 Client (`oauth2_client`)
+
+- `REGISTER_EMAIL_CONFIRM`: *[service]* **REGISTER\_EMAIL\_CONFIRM**: Set this to enable or disable email confirmation of OAuth2 auto-registration. (Overwrites the REGISTER\_EMAIL\_CONFIRM setting of the `[service]` section)
+- `OPENID_CONNECT_SCOPES`: **\<empty\>**: List of additional openid connect scopes. (`openid` is implicitly added)
+- `ENABLE_AUTO_REGISTRATION`: **false**: Automatically create user accounts for new oauth2 users.
+- `USERNAME`: **nickname**: The source of the username for new oauth2 accounts:
+    - userid - use the userid / sub attribute
+    - nickname - use the nickname attribute
+    - email - use the username part of the email attribute
+- `UPDATE_AVATAR`: **false**: Update avatar if available from oauth2 provider. Update will be performed on each login.
+- `ACCOUNT_LINKING`: **disabled**: How to handle if an account / email already exists:
+    - disabled - show an error
+    - login - show an account linking login
+    - auto - automatically link with the account (Please be aware that this will grant access to an existing account just because the same username or email is provided. You must make sure that this does not cause issues with your authentication providers.)
+
 ## Service (`service`)
 
 - `ACTIVE_CODE_LIVE_MINUTES`: **180**: Time limit (min) to confirm account/email registration.

models/migrations/migrations.go

@@ -307,6 +307,8 @@ var migrations = []Migration{
 
 	// v178 -> v179
 	NewMigration("Add LFS columns to Mirror", addLFSMirrorColumns),
+	// v179 -> v180
+	NewMigration("Convert avatar url to text", convertAvatarURLToText),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v179.go

@@ -0,0 +1,26 @@
+// Copyright 2021 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 migrations
+
+import (
+	"xorm.io/xorm"
+	"xorm.io/xorm/schemas"
+)
+
+func convertAvatarURLToText(x *xorm.Engine) error {
+	dbType := x.Dialect().URI().DBType
+	if dbType == schemas.SQLITE { // For SQLITE, varchar or char will always be represented as TEXT
+		return nil
+	}
+
+	// Some oauth2 providers may give very long avatar urls (i.e. Google)
+	return modifyColumn(x, "external_login_user", &schemas.Column{
+		Name: "avatar_url",
+		SQLType: schemas.SQLType{
+			Name: schemas.Text,
+		},
+		Nullable: true,
+	})
+}

modules/auth/oauth2/oauth2.go

@@ -157,7 +157,11 @@ func createProvider(providerName, providerType, clientID, clientSecret, openIDCo
 				emailURL = customURLMapping.EmailURL
 			}
 		}
-		provider = github.NewCustomisedURL(clientID, clientSecret, callbackURL, authURL, tokenURL, profileURL, emailURL)
+		scopes := []string{}
+		if setting.OAuth2Client.EnableAutoRegistration {
+			scopes = append(scopes, "user:email")
+		}
+		provider = github.NewCustomisedURL(clientID, clientSecret, callbackURL, authURL, tokenURL, profileURL, emailURL, scopes...)
 	case "gitlab":
 		authURL := gitlab.AuthURL
 		tokenURL := gitlab.TokenURL
@@ -175,9 +179,13 @@ func createProvider(providerName, providerType, clientID, clientSecret, openIDCo
 		}
 		provider = gitlab.NewCustomisedURL(clientID, clientSecret, callbackURL, authURL, tokenURL, profileURL, "read_user")
 	case "gplus": // named gplus due to legacy gplus -> google migration (Google killed Google+). This ensures old connections still work
-		provider = google.New(clientID, clientSecret, callbackURL)
+		scopes := []string{"email"}
+		if setting.OAuth2Client.UpdateAvatar || setting.OAuth2Client.EnableAutoRegistration {
+			scopes = append(scopes, "profile")
+		}
+		provider = google.New(clientID, clientSecret, callbackURL, scopes...)
 	case "openidConnect":
-		if provider, err = openidConnect.New(clientID, clientSecret, callbackURL, openIDConnectAutoDiscoveryURL); err != nil {
+		if provider, err = openidConnect.New(clientID, clientSecret, callbackURL, openIDConnectAutoDiscoveryURL, setting.OAuth2Client.OpenIDConnectScopes...); err != nil {
 			log.Warn("Failed to create OpenID Connect Provider with name '%s' with url '%s': %v", providerName, openIDConnectAutoDiscoveryURL, err)
 		}
 	case "twitter":

modules/setting/oauth2_client.go

@@ -0,0 +1,90 @@
+// Copyright 2021 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 setting
+
+import (
+	"code.gitea.io/gitea/modules/log"
+
+	"gopkg.in/ini.v1"
+)
+
+// OAuth2UsernameType is enum describing the way gitea 'name' should be generated from oauth2 data
+type OAuth2UsernameType string
+
+const (
+	// OAuth2UsernameUserid oauth2 userid field will be used as gitea name
+	OAuth2UsernameUserid OAuth2UsernameType = "userid"
+	// OAuth2UsernameNickname oauth2 nickname field will be used as gitea name
+	OAuth2UsernameNickname OAuth2UsernameType = "nickname"
+	// OAuth2UsernameEmail username of oauth2 email filed will be used as gitea name
+	OAuth2UsernameEmail OAuth2UsernameType = "email"
+)
+
+func (username OAuth2UsernameType) isValid() bool {
+	switch username {
+	case OAuth2UsernameUserid, OAuth2UsernameNickname, OAuth2UsernameEmail:
+		return true
+	}
+	return false
+}
+
+// OAuth2AccountLinkingType is enum describing behaviour of linking with existing account
+type OAuth2AccountLinkingType string
+
+const (
+	// OAuth2AccountLinkingDisabled error will be displayed if account exist
+	OAuth2AccountLinkingDisabled OAuth2AccountLinkingType = "disabled"
+	// OAuth2AccountLinkingLogin account linking login will be displayed if account exist
+	OAuth2AccountLinkingLogin OAuth2AccountLinkingType = "login"
+	// OAuth2AccountLinkingAuto account will be automatically linked if account exist
+	OAuth2AccountLinkingAuto OAuth2AccountLinkingType = "auto"
+)
+
+func (accountLinking OAuth2AccountLinkingType) isValid() bool {
+	switch accountLinking {
+	case OAuth2AccountLinkingDisabled, OAuth2AccountLinkingLogin, OAuth2AccountLinkingAuto:
+		return true
+	}
+	return false
+}
+
+// OAuth2Client settings
+var OAuth2Client struct {
+	RegisterEmailConfirm   bool
+	OpenIDConnectScopes    []string
+	EnableAutoRegistration bool
+	Username               OAuth2UsernameType
+	UpdateAvatar           bool
+	AccountLinking         OAuth2AccountLinkingType
+}
+
+func newOAuth2Client() {
+	sec := Cfg.Section("oauth2_client")
+	OAuth2Client.RegisterEmailConfirm = sec.Key("REGISTER_EMAIL_CONFIRM").MustBool(Service.RegisterEmailConfirm)
+	OAuth2Client.OpenIDConnectScopes = parseScopes(sec, "OPENID_CONNECT_SCOPES")
+	OAuth2Client.EnableAutoRegistration = sec.Key("ENABLE_AUTO_REGISTRATION").MustBool()
+	OAuth2Client.Username = OAuth2UsernameType(sec.Key("USERNAME").MustString(string(OAuth2UsernameNickname)))
+	if !OAuth2Client.Username.isValid() {
+		log.Warn("Username setting is not valid: '%s', will fallback to '%s'", OAuth2Client.Username, OAuth2UsernameNickname)
+		OAuth2Client.Username = OAuth2UsernameNickname
+	}
+	OAuth2Client.UpdateAvatar = sec.Key("UPDATE_AVATAR").MustBool()
+	OAuth2Client.AccountLinking = OAuth2AccountLinkingType(sec.Key("ACCOUNT_LINKING").MustString(string(OAuth2AccountLinkingDisabled)))
+	if !OAuth2Client.AccountLinking.isValid() {
+		log.Warn("Account linking setting is not valid: '%s', will fallback to '%s'", OAuth2Client.AccountLinking, OAuth2AccountLinkingDisabled)
+		OAuth2Client.AccountLinking = OAuth2AccountLinkingDisabled
+	}
+}
+
+func parseScopes(sec *ini.Section, name string) []string {
+	parts := sec.Key(name).Strings(" ")
+	scopes := make([]string, 0, len(parts))
+	for _, scope := range parts {
+		if scope != "" {
+			scopes = append(scopes, scope)
+		}
+	}
+	return scopes
+}

modules/setting/setting.go

@@ -1163,6 +1163,7 @@ func MakeManifestData(appName string, appURL string, absoluteAssetURL string) []
 func NewServices() {
 	InitDBConfig()
 	newService()
+	newOAuth2Client()
 	NewLogServices(false)
 	newCacheService()
 	newSessionService()