Block ability to use '*'. replace origins string to a list to config. enable cors for specific endpoints

Author: Jisse-Meruma

config-example.yaml

@@ -40,12 +40,15 @@ grpc_listen_addr: 127.0.0.1:50443
 # are doing.
 grpc_allow_insecure: false
 
-# The Access-Control-Allow-Origin header specifies which origins are allowed to access resources.
+# The allow_origins list will allow you to set the Access-Control-Allow-Origin header to the origin in the list.
+# This will allow you to enable cors and set headscale without a reverse proxy.
+# Multiple origins can be set in the allow_origins list.
 # Options:
-# - "*" to allow access from any origin (not recommended for sensitive data).
-# - "http://example.com" to only allow access from a specific origin.
-# - "" to disable Cross-Origin Resource Sharing (CORS).
-access_control_allow_origin: ""
+# - "*" is disabled (due to security risks).
+# - "https://example.com" to only allow access from a specific origin.
+# - "https://example.com:1234" to allow access from a specific origin with a port.
+cors:
+  allow_origins: []
 
 # The Noise section includes specific configuration for the
 # TS2021 Noise protocol

hscontrol/app.go

@@ -455,18 +455,64 @@ func (h *Headscale) ensureUnixSocketIsAbsent() error {
 	return os.Remove(h.cfg.UnixSocket)
 }
 
+// corsHeaderMiddleware will add an "Access-Control-Allow-Origin" to enable CORS
 func (h *Headscale) corsHeadersMiddleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		w.Header().Set("Access-Control-Allow-Origin", h.cfg.AccessControlAllowOrigins)
+
+		// skip disabled CORS endpoints
+		if !h.enabledCorsRoutes(r.URL.Path) {
+			next.ServeHTTP(w, r)
+			return
+		}
+
+		origin := r.Header.Get("Origin")
+		// we compare origin from the allowed Origins list. Then add the header with origin
+		for _, allowedOrigin := range h.cfg.AllowedOrigins.Origins {
+			if allowedOrigin == origin {
+				w.Header().Set("Vary", "Origin")
+				w.Header().Set("Access-Control-Allow-Origin", allowedOrigin)
+				break
+			}
+		}
 		next.ServeHTTP(w, r)
 	})
 }
 
+func (h *Headscale) enabledCorsRoutes(routerPath string) bool {
+
+	// enable all api endpoints
+	if strings.HasPrefix(routerPath, "/api/") {
+		return true
+	} 
+
+	// A list of enabled CORS endpoints
+	var enabledRoutes = []string{
+		"/health",
+		"/key",
+		"/register/{registration_id}",
+		"/oidc/callback",
+		"/verify",
+		"/derp",
+		"/derp/probe",
+		"/derp/latency-check",
+		"/bootstrap-dns",
+		"/machine/register",
+		"/machine/map",
+	}
+
+	for _, routes := range enabledRoutes {
+		if routes == routerPath {
+			return true
+		}
+	}
+	return false
+}
+
 func (h *Headscale) createRouter(grpcMux *grpcRuntime.ServeMux) *mux.Router {
 	router := mux.NewRouter()
 	router.Use(prometheusMiddleware)
 
-	if h.cfg.AccessControlAllowOrigins != "" {
+	if len(h.cfg.AllowedOrigins.Origins) != 0 {
 		router.Use(h.corsHeadersMiddleware)
 	}
 

hscontrol/types/config.go

@@ -66,7 +66,7 @@ type Config struct {
 	Log                            LogConfig
 	DisableUpdateCheck             bool
 
-	AccessControlAllowOrigins string
+	AllowedOrigins CorsConfig
 
 	Database DatabaseConfig
 
@@ -210,6 +210,10 @@ type LogTailConfig struct {
 	Enabled bool
 }
 
+type CorsConfig struct {
+	Origins []string;
+}
+
 type CLIConfig struct {
 	Address  string
 	APIKey   string
@@ -534,6 +538,14 @@ func logtailConfig() LogTailConfig {
 	}
 }
 
+func corsConfig() CorsConfig {
+	allowedOrigins := viper.GetStringSlice("cors.allowed_origins")
+
+	return CorsConfig{
+		Origins: allowedOrigins,
+	}
+}
+
 func policyConfig() PolicyConfig {
 	policyPath := viper.GetString("policy.path")
 	policyMode := viper.GetString("policy.mode")
@@ -907,7 +919,7 @@ func LoadServerConfig() (*Config, error) {
 		GRPCAllowInsecure:  viper.GetBool("grpc_allow_insecure"),
 		DisableUpdateCheck: false,
 
-		AccessControlAllowOrigins: viper.GetString("access_control_allow_origin"),
+		AllowedOrigins: corsConfig(),
 
 		PrefixV4:     prefix4,
 		PrefixV6:     prefix6,