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|
package main
import (
"encoding/gob"
"errors"
"os"
"os/exec"
"os/signal"
"path"
"strconv"
"syscall"
"time"
init0 "git.ophivana.moe/security/fortify/cmd/finit/ipc"
"git.ophivana.moe/security/fortify/internal"
"git.ophivana.moe/security/fortify/internal/fmsg"
)
const (
// time to wait for linger processes after death of initial process
residualProcessTimeout = 5 * time.Second
)
// everything beyond this point runs within pid namespace
// proceed with caution!
func main() {
// sharing stdout with shim
// USE WITH CAUTION
fmsg.SetPrefix("init")
// setting this prevents ptrace
if err := internal.PR_SET_DUMPABLE__SUID_DUMP_DISABLE(); err != nil {
fmsg.Fatalf("cannot set SUID_DUMP_DISABLE: %s", err)
panic("unreachable")
}
if os.Getpid() != 1 {
fmsg.Fatal("this process must run as pid 1")
panic("unreachable")
}
// re-exec
if len(os.Args) > 0 && (os.Args[0] != "finit" || len(os.Args) != 1) && path.IsAbs(os.Args[0]) {
if err := syscall.Exec(os.Args[0], []string{"finit"}, os.Environ()); err != nil {
fmsg.Println("cannot re-exec self:", err)
// continue anyway
}
}
// setup pipe fd from environment
var setup *os.File
if s, ok := os.LookupEnv(init0.Env); !ok {
fmsg.Fatal("FORTIFY_INIT not set")
panic("unreachable")
} else {
if fd, err := strconv.Atoi(s); err != nil {
fmsg.Fatalf("cannot parse %q: %v", s, err)
panic("unreachable")
} else {
setup = os.NewFile(uintptr(fd), "setup")
if setup == nil {
fmsg.Fatal("invalid config descriptor")
panic("unreachable")
}
}
}
var payload init0.Payload
if err := gob.NewDecoder(setup).Decode(&payload); err != nil {
fmsg.Fatal("cannot decode init setup payload:", err)
panic("unreachable")
} else {
fmsg.SetVerbose(payload.Verbose)
// child does not need to see this
if err = os.Unsetenv(init0.Env); err != nil {
fmsg.Printf("cannot unset %s: %v", init0.Env, err)
// not fatal
} else {
fmsg.VPrintln("received configuration")
}
}
// die with parent
if err := internal.PR_SET_PDEATHSIG__SIGKILL(); err != nil {
fmsg.Fatalf("prctl(PR_SET_PDEATHSIG, SIGKILL): %v", err)
}
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()
if err := cmd.Start(); err != nil {
fmsg.Fatalf("cannot start %q: %v", payload.Argv0, err)
}
fmsg.Suspend()
// close setup pipe as setup is now complete
if err := setup.Close(); err != nil {
fmsg.Println("cannot close setup pipe:", err)
// not fatal
}
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)
}()
// closed after residualProcessTimeout has elapsed after initial process death
timeout := make(chan struct{})
r := 2
for {
select {
case s := <-sig:
fmsg.VPrintln("received", s.String())
fmsg.Resume() // output could still be withheld at this point, so resume is called
fmsg.Exit(0)
case w := <-info:
if w.wpid == cmd.Process.Pid {
// initial process exited, output is most likely available again
fmsg.Resume()
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)
}
}
}
|
