Restore user autoregistration with email addresses (go-gitea#19261)

Backport go-gitea#19261

Unfortunately go-gitea#18789 disabled autoregistration using email addresses as they would
be shortcut to email address does not exist.

This PR attempts to restore autoregistration by allowing an unknown email address
to percolate through to the autoregistration path of UserSignin.

Fix go-gitea#19256

Signed-off-by: Andrew Thornton <art27@cantab.net>

services/auth/signin.go

@@ -23,19 +23,23 @@ import (
 // UserSignIn validates user name and password.
 func UserSignIn(username, password string) (*user_model.User, *auth.Source, error) {
 	var user *user_model.User
+	isEmail := false
 	if strings.Contains(username, "@") {
+		isEmail = true
 		emailAddress := user_model.EmailAddress{LowerEmail: strings.ToLower(strings.TrimSpace(username))}
 		// check same email
-		has, err := db.GetEngine(db.DefaultContext).Where("is_activated=?", true).Get(&emailAddress)
+		has, err := db.GetEngine(db.DefaultContext).Get(&emailAddress)
 		if err != nil {
 			return nil, nil, err
 		}
-		if !has {
-			return nil, nil, user_model.ErrEmailAddressNotExist{
-				Email: username,
+		if has {
+			if !emailAddress.IsActivated {
+				return nil, nil, user_model.ErrEmailAddressNotExist{
+					Email: username,
+				}
 			}
+			user = &user_model.User{ID: emailAddress.UID}
 		}
-		user = &user_model.User{ID: emailAddress.UID}
 	} else {
 		trimmedUsername := strings.TrimSpace(username)
 		if len(trimmedUsername) == 0 {
@@ -45,38 +49,40 @@ func UserSignIn(username, password string) (*user_model.User, *auth.Source, erro
 		user = &user_model.User{LowerName: strings.ToLower(trimmedUsername)}
 	}
 
-	hasUser, err := user_model.GetUser(user)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	if hasUser {
-		source, err := auth.GetSourceByID(user.LoginSource)
+	if user != nil {
+		hasUser, err := user_model.GetUser(user)
 		if err != nil {
 			return nil, nil, err
 		}
 
-		if !source.IsActive {
-			return nil, nil, oauth2.ErrAuthSourceNotActived
-		}
+		if hasUser {
+			source, err := auth.GetSourceByID(user.LoginSource)
+			if err != nil {
+				return nil, nil, err
+			}
 
-		authenticator, ok := source.Cfg.(PasswordAuthenticator)
-		if !ok {
-			return nil, nil, smtp.ErrUnsupportedLoginType
-		}
+			if !source.IsActive {
+				return nil, nil, oauth2.ErrAuthSourceNotActived
+			}
 
-		user, err := authenticator.Authenticate(user, user.LoginName, password)
-		if err != nil {
-			return nil, nil, err
-		}
+			authenticator, ok := source.Cfg.(PasswordAuthenticator)
+			if !ok {
+				return nil, nil, smtp.ErrUnsupportedLoginType
+			}
 
-		// WARN: DON'T check user.IsActive, that will be checked on reqSign so that
-		// user could be hint to resend confirm email.
-		if user.ProhibitLogin {
-			return nil, nil, user_model.ErrUserProhibitLogin{UID: user.ID, Name: user.Name}
-		}
+			user, err := authenticator.Authenticate(user, user.LoginName, password)
+			if err != nil {
+				return nil, nil, err
+			}
 
-		return user, source, nil
+			// WARN: DON'T check user.IsActive, that will be checked on reqSign so that
+			// user could be hint to resend confirm email.
+			if user.ProhibitLogin {
+				return nil, nil, user_model.ErrUserProhibitLogin{UID: user.ID, Name: user.Name}
+			}
+
+			return user, source, nil
+		}
 	}
 
 	sources, err := auth.AllActiveSources()
@@ -111,5 +117,9 @@ func UserSignIn(username, password string) (*user_model.User, *auth.Source, erro
 		}
 	}
 
+	if isEmail {
+		return nil, nil, user_model.ErrEmailAddressNotExist{Email: username}
+	}
+
 	return nil, nil, user_model.ErrUserNotExist{Name: username}
 }