implement basic ACL for debug http

README

@@ -43,6 +43,7 @@ The following flags are automatically registered:
 
  - `-listen_address` (default: `127.0.0.1:4200`): where to listen for gRPC requests
  - `-debug_address` (default: `127.0.0.1:4201`): where to listen for debug HTTP requests
+ - `-debug_allow_all` (default: false): whether to allow all IP address (vs. localhost) to connect to debug endpoint
 
 Since this library also includes [hspki](https://code.hackerspace.pl/q3k/hspki), you also get all the typical `-hspki_{...}` flags included.
 

mirko.go

@@ -19,11 +19,13 @@ import (
 var (
 	flagListenAddress string
 	flagDebugAddress  string
+	flagDebugAllowAll bool
 )
 
 func init() {
 	flag.StringVar(&flagListenAddress, "listen_address", "127.0.0.1:4200", "gRPC listen address")
 	flag.StringVar(&flagDebugAddress, "debug_address", "127.0.0.1:4201", "HTTP debug/status listen address")
+	flag.StringVar(&flagDebugAllowAll, "debug_allow_all", false, "HTTP debug/status available to everyone")
 	flag.Set("logtostderr", "true")
 }
 
@@ -39,8 +41,28 @@ func New() *Mirko {
 	return &Mirko{}
 }
 
+func authRequest(req *http.Request) (any, sensitive bool) {
+	host, _, err := net.SplitHostPort(req.RemoteAddr)
+	if err != nil {
+		host = req.RemoteAddr
+	}
+
+	if flagDebugAllowAll {
+		return true, true
+	}
+
+	switch host {
+	case "localhost", "127.0.0.1", "::1":
+		return true, true
+	default:
+		return false, false
+	}
+}
+
 func (m *Mirko) Listen() error {
 	grpc.EnableTracing = true
+	trace.AuthRequest = authRequest
+
 	grpcLis, err := net.Listen("tcp", flagListenAddress)
 	if err != nil {
 		return fmt.Errorf("net.Listen: %v", err)
@@ -56,7 +78,14 @@ func (m *Mirko) Listen() error {
 
 	m.httpMux = http.NewServeMux()
 	// Canonical URLs
-	m.httpMux.HandleFunc("/debug/status", statusz.StatusHandler)
+	m.httpMux.HandleFunc("/debug/status", func(w http.ResponseWriter, r *http.Request) {
+		any, sensitive := authRequest(r)
+		if !any {
+			http.Error(w, "not allowed", http.StatusUnauthorized)
+			return
+		}
+		statusz.StatusHandler(w, r)
+	})
 	m.httpMux.HandleFunc("/debug/requests", trace.Traces)
 
 	// -z legacy URLs