better argument forwarding to child

tlsserver.go

@@ -17,12 +17,13 @@ import (
 var (
 	cfile = flag.String("cert", "cert.pem", "Certificate file in PEM format")
 	kfile = flag.String("key", "key.pem", "Key file in PEM format")
-	port  = flag.Int("port", 1234, "Port to bind to")
+	port  = flag.String("port", ":1234", "Port to bind to")
 	uid   = flag.Int("uid", -1, "UID to run under")
-	child = flag.Bool("child", false, "running as child")
 	args  []string
 )
 
+const FORKED = "[forked]"
+
 func main() {
 	flag.Parse()
 
@@ -33,7 +34,7 @@ func main() {
 		os.Exit(1)
 	}
 
-	if *child {
+	if os.Args[0] == FORKED {
 		log.Fatal(serve())
 	} else {
 		log.Fatal(fork())
@@ -52,13 +53,14 @@ func fork() error {
 		return err
 	}
 
-	// Get the groups
+	// Get the primary and secondary groups
+	gids := []uint32{}
+
 	gid, err := strconv.Atoi(user.Gid)
 	if err != nil {
 		return fmt.Errorf("couldn't parse user.Gid, strconv.Atoi(%s): %v", user.Gid, err)
 	}
-
-	gids := []uint32{uint32(gid)}
+	gids = append(gids, uint32(gid))
 
 	if sgids, err := user.GroupIds(); err != nil {
 		log.Println("weird, couldn't get supplimentary groups: %v", err)
@@ -74,20 +76,24 @@ func fork() error {
 		}
 	}
 
-	args := []string{
-		"-child",
-		"-cert", *cfile,
-		"-key", *kfile,
-		"-port", strconv.Itoa(*port)}
-	args = append(args, flag.Args()...)
-
-	cmd := exec.Command(os.Args[0], args...)
-
+	cmd := exec.Command(os.Args[0])
 	cmd.Stdin = os.Stdin
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 
-	// set the uid/gid
+	// Setup the arguments that are needed
+	cmd.Args = []string{FORKED} // name of the command
+
+	for _, arg := range []string{"cert", "key", "port"} {
+		fl := flag.Lookup(arg)
+		// Only set the flag if it's value are different from the default
+		if fl != nil && fl.Value.String() != fl.DefValue {
+			cmd.Args = append(cmd.Args, "-"+arg, fl.Value.String())
+		}
+	}
+	cmd.Args = append(cmd.Args, flag.Args()...)
+
+	// Set the uid/gid
 	cmd.SysProcAttr = &syscall.SysProcAttr{
 		Pdeathsig: syscall.SIGTERM,
 		Credential: &syscall.Credential{
@@ -97,7 +103,7 @@ func fork() error {
 		},
 	}
 
-	// pass on signals that we receive
+	// Pass on signals that we receive
 	ch := make(chan os.Signal, 1)
 	signal.Notify(ch,
 		os.Interrupt,
@@ -113,7 +119,7 @@ func fork() error {
 		}
 	}()
 
-	// energy!
+	// Energy!
 	return cmd.Run()
 }
 
@@ -132,8 +138,7 @@ func serve() error {
 	tconf.BuildNameToCertificate()
 
 	// start listening
-	sport := fmt.Sprintf(":%d", *port)
-	sock, err := tls.Listen("tcp", sport, tconf)
+	sock, err := tls.Listen("tcp", *port, tconf)
 	if err != nil {
 		fmt.Println("error with tcp-socket:", err)
 		os.Exit(3)