restore strip_email_domain for migration

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

hscontrol/oidc.go

@@ -445,26 +445,30 @@ func (a *AuthProviderOIDC) createOrUpdateUserFromClaim(
 	// look it up by username. This should only be needed once.
 	// This branch will presist for a number of versions after the OIDC migration and
 	// then be removed following a deprecation.
+	// TODO(kradalby): Remove when strip_email_domain and migration is removed
+	// after #2170 is cleaned up.
 	if a.cfg.MapLegacyUsers && user == nil {
-		user, err = a.db.GetUserByName(claims.Username)
+		if oldUsername, err := getUserName(claims, a.cfg.StripEmaildomain); err == nil {
+			user, err = a.db.GetUserByName(oldUsername)
 			if err != nil && !errors.Is(err, db.ErrUserNotFound) {
 				return nil, fmt.Errorf("creating or updating user: %w", err)
 			}
 
-		// if the user is still not found, create a new empty user.
-		if user == nil {
-			user = &types.User{}
-		}
-
 			// If the user exists, but it already has a provider identifier (OIDC sub), create a new user.
 			// This is to prevent users that have already been migrated to the new OIDC format
 			// to be updated with the new OIDC identifier inexplicitly which might be the cause of an
 			// account takeover.
-		if user.ProviderIdentifier != "" {
+			if user != nil && user.ProviderIdentifier != "" {
 				log.Info().Str("username", claims.Username).Str("sub", claims.Sub).Msg("user found by username, but has provider identifier, creating new user.")
 				user = &types.User{}
 			}
 		}
+	}
+
+	// if the user is still not found, create a new empty user.
+	if user == nil {
+		user = &types.User{}
+	}
 
 	user.FromClaim(claims)
 	err = a.db.DB.Save(user).Error
@@ -513,3 +517,21 @@ func renderOIDCCallbackTemplate(
 
 	return &content, nil
 }
+
+// TODO(kradalby): Reintroduce when strip_email_domain is removed
+// after #2170 is cleaned up
+// DEPRECATED: DO NOT USE
+func getUserName(
+	claims *types.OIDCClaims,
+	stripEmaildomain bool,
+) (string, error) {
+	userName, err := util.NormalizeToFQDNRules(
+		claims.Email,
+		stripEmaildomain,
+	)
+	if err != nil {
+		return "", err
+	}
+
+	return userName, nil
+}

hscontrol/types/config.go

@@ -162,6 +162,7 @@ type OIDCConfig struct {
 	AllowedDomains             []string
 	AllowedUsers               []string
 	AllowedGroups              []string
+	StripEmaildomain           bool
 	Expiry                     time.Duration
 	UseExpiryFromToken         bool
 	MapLegacyUsers             bool
@@ -273,6 +274,7 @@ func LoadConfig(path string, isFile bool) error {
 	viper.SetDefault("database.sqlite.write_ahead_log", true)
 
 	viper.SetDefault("oidc.scope", []string{oidc.ScopeOpenID, "profile", "email"})
+	viper.SetDefault("oidc.strip_email_domain", true)
 	viper.SetDefault("oidc.only_start_if_oidc_is_available", true)
 	viper.SetDefault("oidc.expiry", "180d")
 	viper.SetDefault("oidc.use_expiry_from_token", false)
@@ -320,14 +322,18 @@ func validateServerConfig() error {
 	depr.warn("dns_config.use_username_in_magic_dns")
 	depr.warn("dns.use_username_in_magic_dns")
 
-	depr.fatal("oidc.strip_email_domain")
+	// TODO(kradalby): Reintroduce when strip_email_domain is removed
+	// after #2170 is cleaned up
+	// depr.fatal("oidc.strip_email_domain")
 	depr.fatal("dns.use_username_in_musername_in_magic_dns")
 	depr.fatal("dns_config.use_username_in_musername_in_magic_dns")
 
 	depr.Log()
 
 	for _, removed := range []string{
-		"oidc.strip_email_domain",
+		// TODO(kradalby): Reintroduce when strip_email_domain is removed
+		// after #2170 is cleaned up
+		// "oidc.strip_email_domain",
 		"dns_config.use_username_in_musername_in_magic_dns",
 	} {
 		if viper.IsSet(removed) {

hscontrol/util/dns.go

@@ -182,3 +182,33 @@ func GenerateIPv6DNSRootDomain(ipPrefix netip.Prefix) []dnsname.FQDN {
 
 	return fqdns
 }
+
+// TODO(kradalby): Reintroduce when strip_email_domain is removed
+// after #2170 is cleaned up
+// DEPRECATED: DO NOT USE
+// NormalizeToFQDNRules will replace forbidden chars in user
+// it can also return an error if the user doesn't respect RFC 952 and 1123.
+func NormalizeToFQDNRules(name string, stripEmailDomain bool) (string, error) {
+
+	name = strings.ToLower(name)
+	name = strings.ReplaceAll(name, "'", "")
+	atIdx := strings.Index(name, "@")
+	if stripEmailDomain && atIdx > 0 {
+		name = name[:atIdx]
+	} else {
+		name = strings.ReplaceAll(name, "@", ".")
+	}
+	name = invalidCharsInUserRegex.ReplaceAllString(name, "-")
+
+	for _, elt := range strings.Split(name, ".") {
+		if len(elt) > LabelHostnameLength {
+			return "", fmt.Errorf(
+				"label %v is more than 63 chars: %w",
+				elt,
+				ErrInvalidUserName,
+			)
+		}
+	}
+
+	return name, nil
+}