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|
package init0
import (
"encoding/gob"
"errors"
"flag"
"os"
"os/exec"
"os/signal"
"path"
"strconv"
"syscall"
"time"
"git.ophivana.moe/security/fortify/internal/fmsg"
)
const (
// time to wait for linger processes after death initial process
residualProcessTimeout = 5 * time.Second
)
// everything beyond this point runs within pid namespace
// proceed with caution!
func doInit(fd uintptr) {
fmsg.SetPrefix("init")
// re-exec
if len(os.Args) > 0 && os.Args[0] != "fortify" && path.IsAbs(os.Args[0]) {
if err := syscall.Exec(os.Args[0], []string{"fortify", "init"}, os.Environ()); err != nil {
fmsg.Println("cannot re-exec self:", err)
// continue anyway
}
}
var payload Payload
p := os.NewFile(fd, "config-stream")
if p == nil {
fmsg.Fatal("invalid config descriptor")
}
if err := gob.NewDecoder(p).Decode(&payload); err != nil {
fmsg.Fatal("cannot decode init payload:", err)
} else {
// sharing stdout with parent
// USE WITH CAUTION
fmsg.SetVerbose(payload.Verbose)
// child does not need to see this
if err = os.Unsetenv(EnvInit); err != nil {
fmsg.Println("cannot unset", EnvInit+":", err)
// not fatal
} else {
fmsg.VPrintln("received configuration")
}
}
// close config fd
if err := p.Close(); err != nil {
fmsg.Println("cannot close config fd:", err)
// not fatal
}
// die with parent
if _, _, errno := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_PDEATHSIG, uintptr(syscall.SIGKILL), 0); errno != 0 {
fmsg.Fatal("prctl(PR_SET_PDEATHSIG, SIGKILL):", errno.Error())
}
cmd := exec.Command(payload.Argv0)
cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
cmd.Args = payload.Argv
cmd.Env = os.Environ()
// pass wayland fd
if payload.WL != -1 {
if f := os.NewFile(uintptr(payload.WL), "wayland"); f != nil {
cmd.Env = append(cmd.Env, "WAYLAND_SOCKET="+strconv.Itoa(3+len(cmd.ExtraFiles)))
cmd.ExtraFiles = append(cmd.ExtraFiles, f)
}
}
if err := cmd.Start(); err != nil {
fmsg.Fatalf("cannot start %q: %v", payload.Argv0, err)
}
sig := make(chan os.Signal, 2)
signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
type winfo struct {
wpid int
wstatus syscall.WaitStatus
}
info := make(chan winfo, 1)
done := make(chan struct{})
go func() {
var (
err error
wpid = -2
wstatus syscall.WaitStatus
)
// keep going until no child process is left
for wpid != -1 {
if err != nil {
break
}
if wpid != -2 {
info <- winfo{wpid, wstatus}
}
err = syscall.EINTR
for errors.Is(err, syscall.EINTR) {
wpid, err = syscall.Wait4(-1, &wstatus, 0, nil)
}
}
if !errors.Is(err, syscall.ECHILD) {
fmsg.Println("unexpected wait4 response:", err)
}
close(done)
}()
timeout := make(chan struct{})
r := 2
for {
select {
case s := <-sig:
fmsg.VPrintln("received", s.String())
fmsg.Exit(0)
case w := <-info:
if w.wpid == cmd.Process.Pid {
switch {
case w.wstatus.Exited():
r = w.wstatus.ExitStatus()
case w.wstatus.Signaled():
r = 128 + int(w.wstatus.Signal())
default:
r = 255
}
go func() {
time.Sleep(residualProcessTimeout)
close(timeout)
}()
}
case <-done:
fmsg.Exit(r)
case <-timeout:
fmsg.Println("timeout exceeded waiting for lingering processes")
fmsg.Exit(r)
}
}
}
// Try runs init and stops execution if FORTIFY_INIT is set.
func Try() {
if os.Getpid() != 1 {
return
}
if args := flag.Args(); len(args) == 1 && args[0] == "init" {
if s, ok := os.LookupEnv(EnvInit); ok {
if fd, err := strconv.Atoi(s); err != nil {
fmsg.Fatalf("cannot parse %q: %v", s, err)
} else {
doInit(uintptr(fd))
}
panic("unreachable")
}
}
}
|
