go-sandbox/deamon/container_init.go
2019-08-07 22:08:59 -07:00

205 lines
4.5 KiB
Go

package deamon
import (
"bytes"
"encoding/gob"
"fmt"
"os"
"syscall"
"github.com/criyle/go-judger/forkexec"
"github.com/criyle/go-judger/types/specs"
"github.com/criyle/go-judger/unixsocket"
)
// ContainerInit is called for container init process
// it will check if pid == 1, otherwise it is noop
// ContainerInit will do infinite loop on socket commands,
// and exits when at socket close
func ContainerInit() (err error) {
// noop if self is not container init process
if os.Getpid() != 1 {
return nil
}
// exit process (with whole container) upon exit this function
defer func() {
if err != nil {
fmt.Fprintf(os.Stderr, "container_exit: %v", err)
os.Exit(1)
} else {
fmt.Fprintf(os.Stderr, "container_exit")
os.Exit(0)
}
}()
// new_master shared the socket at fd 3 (marked close_exec)
soc, err := unixsocket.NewSocket(3)
if err != nil {
return fmt.Errorf("container_init: faile to new socket(%v)", err)
}
for {
cmd, msg, err := recvCmd(soc)
if err != nil {
return fmt.Errorf("loop: %v", err)
}
if err := handleCmd(soc, cmd, msg); err != nil {
return fmt.Errorf("loop: failed to execute cmd(%v)", err)
}
}
}
func handleCmd(s *unixsocket.Socket, cmd *Cmd, msg *unixsocket.Msg) error {
switch cmd.Cmd {
case cmdPing:
return handlePing(s)
case cmdExecve:
return handleExecve(s, cmd, msg)
}
return nil
}
func handlePing(s *unixsocket.Socket) error {
return sendReply(s, &Reply{}, nil)
}
func handleExecve(s *unixsocket.Socket, cmd *Cmd, msg *unixsocket.Msg) error {
var (
files []uintptr
execFile uintptr
)
if msg != nil {
files = intSliceToUintptr(msg.Fds)
}
// release files after execve
defer closeFds(msg.Fds)
if cmd.FdExec && len(files) > 0 {
execFile = files[0]
files = files[1:]
}
syncFunc := func(pid int) error {
msg2 := unixsocket.Msg{
Cred: &syscall.Ucred{
Pid: int32(pid),
Uid: uint32(syscall.Getuid()),
Gid: uint32(syscall.Getgid()),
},
}
if err2 := sendReply(s, &Reply{}, &msg2); err2 != nil {
return fmt.Errorf("syncFunc: sendReply(%v)", err2)
}
cmd2, _, err2 := recvCmd(s)
if err2 != nil {
return fmt.Errorf("syncFunc: recvCmd(%v)", err2)
}
switch cmd2.Cmd {
case cmdKill:
return fmt.Errorf("syncFunc: recved kill")
}
return nil
}
r := forkexec.Runner{
Args: cmd.Argv,
Env: cmd.Envv,
ExecFile: execFile,
RLimits: cmd.RLmits,
Files: files,
WorkDir: "/w",
NoNewPrivs: true,
DropCaps: true,
SyncFunc: syncFunc,
}
pid, err := r.Start()
if err != nil {
reply := Reply{Error: fmt.Sprintf("execve: %v", err)}
sendReply(s, &reply, nil)
return nil
}
done := make(chan int)
// recv kill
go func() {
// msg must be kill
recvCmd(s)
// kill all
syscall.Kill(-1, syscall.SIGKILL)
// collect zombies
for {
_, err = syscall.Wait4(-1, nil, 0, nil)
if err != nil {
break
}
}
// signal done
close(done)
}()
// wait pid
var wstatus syscall.WaitStatus
loop:
for {
_, err = syscall.Wait4(pid, &wstatus, 0, nil)
if err != nil {
reply := Reply{Error: fmt.Sprintf("execve: wait4 %v", err)}
sendReply(s, &reply, nil)
break loop
}
switch {
case wstatus.Exited():
reply := Reply{ExitStatus: wstatus.ExitStatus()}
sendReply(s, &reply, nil)
break loop
case wstatus.Signaled():
var status specs.TraceCode
switch wstatus.Signal() {
// kill signal treats as TLE
case syscall.SIGKILL:
status = specs.TraceCodeTLE
case syscall.SIGXCPU:
status = specs.TraceCodeTLE
case syscall.SIGXFSZ:
status = specs.TraceCodeOLE
case syscall.SIGSYS:
status = specs.TraceCodeBan
default:
status = specs.TraceCodeRE
}
reply := Reply{TraceStatus: status}
sendReply(s, &reply, nil)
break loop
}
}
// wait for kill msg and reply done for finish
<-done
return sendReply(s, &Reply{}, nil)
}
func recvCmd(s *unixsocket.Socket) (*Cmd, *unixsocket.Msg, error) {
var cmd Cmd
buffer := GetBuffer()
defer PutBuffer(buffer)
n, msg, err := s.RecvMsg(buffer)
if err != nil {
return nil, nil, fmt.Errorf("failed RecvMsg(%v)", err)
}
dec := gob.NewDecoder(bytes.NewReader(buffer[:n]))
if err := dec.Decode(&cmd); err != nil {
return nil, nil, fmt.Errorf("failed to decode(%v)", err)
}
return &cmd, msg, nil
}
func sendReply(s *unixsocket.Socket, reply *Reply, msg *unixsocket.Msg) error {
var buffer bytes.Buffer
enc := gob.NewEncoder(&buffer)
if err := enc.Encode(reply); err != nil {
return err
}
if err := s.SendMsg(buffer.Bytes(), msg); err != nil {
return err
}
return nil
}