go-sandbox/daemon/container_init.go

286 lines
6.9 KiB
Go

package daemon
import (
"bytes"
"encoding/gob"
"fmt"
"io"
"os"
"syscall"
"github.com/criyle/go-sandbox/pkg/forkexec"
"github.com/criyle/go-sandbox/pkg/unixsocket"
"github.com/criyle/go-sandbox/types"
)
// Init is called for container init process
// it will check if pid == 1, otherwise it is noop
// Init will do infinite loop on socket commands,
// and exits when at socket close, use it in init function
func Init() (err error) {
// noop if self is not container init process
// Notice: docker init is also 1, additional check for args[1] == init
if os.Getpid() != 1 || len(os.Args) != 2 || os.Args[1] != initArg {
return nil
}
// exit process (with whole container) upon exit this function
defer func() {
if err2 := recover(); err2 != nil {
fmt.Fprintf(os.Stderr, "container_panic: %v", err)
os.Exit(1)
}
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 cmdCopyIn:
return handleCopyIn(s, cmd, msg)
case cmdOpen:
return handleOpen(s, cmd)
case cmdDelete:
return handleDelete(s, cmd)
case cmdReset:
return handleReset(s)
case cmdExecve:
return handleExecve(s, cmd, msg)
}
return fmt.Errorf("Unknown command: %v", cmd.Cmd)
}
func handlePing(s *unixsocket.Socket) error {
return sendReply(s, &Reply{}, nil)
}
func handleCopyIn(s *unixsocket.Socket, cmd *Cmd, msg *unixsocket.Msg) error {
if len(msg.Fds) != 1 {
closeFds(msg.Fds)
return sendErrorReply(s, "copyin: unexpected number of fds(%d)", len(msg.Fds))
}
inf := os.NewFile(uintptr(msg.Fds[0]), cmd.Path)
if inf == nil {
return sendErrorReply(s, "copyin: newfile failed %v", msg.Fds[0])
}
defer inf.Close()
// have 0777 permission to be able copy in executables
outf, err := os.OpenFile(cmd.Path, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0777)
if err != nil {
return sendErrorReply(s, "copyin: open write file %v", err)
}
defer outf.Close()
_, err = io.Copy(outf, inf)
if err != nil {
return sendErrorReply(s, "copyin: io.copy %v", err)
}
return sendReply(s, &Reply{}, nil)
}
func handleOpen(s *unixsocket.Socket, cmd *Cmd) error {
outf, err := os.Open(cmd.Path)
if err != nil {
return sendErrorReply(s, "open: %v", err)
}
defer outf.Close()
return sendReply(s, &Reply{}, &unixsocket.Msg{
Fds: []int{int(outf.Fd())},
})
}
func handleDelete(s *unixsocket.Socket, cmd *Cmd) error {
if err := os.Remove(cmd.Path); err != nil {
return sendErrorReply(s, "delete: %v", err)
}
return sendReply(s, &Reply{}, nil)
}
func handleReset(s *unixsocket.Socket) error {
if err := removeContents("/tmp"); err != nil {
return sendErrorReply(s, "reset: /tmp %v", err)
}
if err := removeContents("/w"); err != nil {
return sendErrorReply(s, "reset: /w %v", err)
}
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)
// don't leak fds to child
closeOnExecFds(msg.Fds)
// release files after execve
defer closeFds(msg.Fds)
}
// if fexecve, then the first fd must be executable
if cmd.FdExec {
if len(files) == 0 {
return fmt.Errorf("execve: expected fexecve fd")
}
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)
}
if cmd2.Cmd == 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,
}
// starts the runner, error is handled same as wait4 to make communication equal
pid, err := r.Start()
// done is to signal kill goroutine exits
killDone := make(chan struct{})
// waitDone is to signal kill goroutine to collect zombies
waitDone := make(chan struct{})
// recv kill
go func() {
// signal done
defer close(killDone)
// msg must be kill
recvCmd(s)
// kill all
syscall.Kill(-1, syscall.SIGKILL)
// make sure collect zombie does not consume the exit status
<-waitDone
// collect zombies
for {
if pid, err := syscall.Wait4(-1, nil, syscall.WNOHANG, nil); err != nil || pid <= 0 {
break
}
}
}()
// wait pid if no error encoutered for execve
var wstatus syscall.WaitStatus
if err == nil {
_, err = syscall.Wait4(pid, &wstatus, 0, nil)
}
// sync with kill goroutine
close(waitDone)
if err != nil {
sendErrorReply(s, "execve: wait4 %v", err)
} else {
switch {
case wstatus.Exited():
sendReply(s, &Reply{ExitStatus: wstatus.ExitStatus()}, nil)
case wstatus.Signaled():
var status types.Status
switch wstatus.Signal() {
// kill signal treats as TLE
case syscall.SIGXCPU, syscall.SIGKILL:
status = types.StatusTLE
case syscall.SIGXFSZ:
status = types.StatusOLE
case syscall.SIGSYS:
status = types.StatusBan
default:
status = types.StatusRE
}
sendReply(s, &Reply{Status: status}, nil)
default:
sendErrorReply(s, "execve: unknown status %v", wstatus)
}
}
// wait for kill msg and reply done for finish
<-killDone
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)
}
if err := gob.NewDecoder(bytes.NewReader(buffer[:n])).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
if err := gob.NewEncoder(&buffer).Encode(reply); err != nil {
return err
}
if err := s.SendMsg(buffer.Bytes(), msg); err != nil {
return err
}
return nil
}
// sendErrorReply sends error reply
func sendErrorReply(s *unixsocket.Socket, ft string, v ...interface{}) error {
reply := Reply{Error: fmt.Sprintf(ft, v...)}
return sendReply(s, &reply, nil)
}