1//go:build unix

2

3package mox

4

5import (

6 "log/slog"

7 "os"

8 "os/signal"

9 "strings"

10 "syscall"

11)

12

13// Fork and exec as unprivileged user.

14//

15// We don't use just setuid because it is hard to guarantee that no other

16// privileged go worker processes have been started before we get here. E.g. init

17// functions in packages can start goroutines.

18func ForkExecUnprivileged() {

19 prog, err := os.Executable()

20 if err != nil {

21 pkglog.Fatalx("finding executable for exec", err)

22 }

23

24 files := []*os.File{os.Stdin, os.Stdout, os.Stderr}

25 var addrs []string

26 for addr, f := range passedListeners {

27 files = append(files, f)

28 addrs = append(addrs, addr)

29 }

30 var paths []string

31 for path, fl := range passedFiles {

32 for _, f := range fl {

33 files = append(files, f)

34 paths = append(paths, path)

35 }

36 }

37 env := os.Environ()

38 env = append(env, "MOX_SOCKETS="+strings.Join(addrs, ","), "MOX_FILES="+strings.Join(paths, ","))

39

40 p, err := os.StartProcess(prog, os.Args, &os.ProcAttr{

41 Env: env,

42 Files: files,

43 Sys: &syscall.SysProcAttr{

44 Credential: &syscall.Credential{

45 Uid: Conf.Static.UID,

46 Gid: Conf.Static.GID,

47 },

48 },

49 })

50 if err != nil {

51 pkglog.Fatalx("fork and exec", err)

52 }

53 CleanupPassedFiles()

54

55 // If we get a interrupt/terminate signal, pass it on to the child. For interrupt,

56 // the child probably already got it.

57 // todo: see if we tie up child and root process so a kill -9 of the root process

58 // kills the child process too.

59 sigc := make(chan os.Signal, 1)

60 signal.Notify(sigc, os.Interrupt, syscall.SIGTERM)

61 go func() {

62 sig := <-sigc

63 p.Signal(sig)

64 }()

65

66 st, err := p.Wait()

67 if err != nil {

68 pkglog.Fatalx("wait", err)

69 }

70 code := st.ExitCode()

71 pkglog.Print("stopping after child exit", slog.Int("exitcode", code))

72 os.Exit(code)

73}

74