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|
package init0
import (
"errors"
"log"
"os"
"os/exec"
"os/signal"
"syscall"
"time"
"git.gensokyo.uk/security/fortify/helper/proc"
"git.gensokyo.uk/security/fortify/internal"
"git.gensokyo.uk/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.Prepare("init0")
// setting this prevents ptrace
if err := internal.SetDumpable(internal.SUID_DUMP_DISABLE); err != nil {
log.Fatalf("cannot set SUID_DUMP_DISABLE: %s", err)
}
if os.Getpid() != 1 {
log.Fatal("this process must run as pid 1")
}
// receive setup payload
var (
payload Payload
closeSetup func() error
)
if f, err := proc.Receive(Env, &payload, nil); err != nil {
if errors.Is(err, proc.ErrInvalid) {
log.Fatal("invalid config descriptor")
}
if errors.Is(err, proc.ErrNotSet) {
log.Fatal("FORTIFY_INIT not set")
}
log.Fatalf("cannot decode init setup payload: %v", err)
} else {
fmsg.Store(payload.Verbose)
closeSetup = f
// child does not need to see this
if err = os.Unsetenv(Env); err != nil {
log.Printf("cannot unset %s: %v", Env, err)
// not fatal
} else {
fmsg.Verbose("received configuration")
}
}
// die with parent
if err := internal.SetPdeathsig(syscall.SIGKILL); err != nil {
log.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 {
log.Fatalf("cannot start %q: %v", payload.Argv0, err)
}
fmsg.Suspend()
// close setup pipe as setup is now complete
if err := closeSetup(); err != nil {
log.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) {
log.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:
if fmsg.Resume() {
fmsg.Verbosef("terminating on %s after process start", s.String())
} else {
fmsg.Verbosef("terminating on %s", s.String())
}
internal.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:
internal.Exit(r)
case <-timeout:
log.Println("timeout exceeded waiting for lingering processes")
internal.Exit(r)
}
}
}
|
