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exec.go
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exec.go
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package main
import (
"encoding/json"
"fmt"
"io/ioutil"
"net/http"
"os"
"os/exec"
"strconv"
"sync"
"syscall"
"github.com/gorilla/websocket"
"golang.org/x/sys/unix"
"github.com/lxc/lxd/lxd/db"
"github.com/lxc/lxd/lxd/operations"
"github.com/lxc/lxd/lxd/response"
"github.com/lxc/lxd/shared"
"github.com/lxc/lxd/shared/api"
"github.com/lxc/lxd/shared/logger"
"github.com/lxc/lxd/shared/netutils"
)
var execCmd = APIEndpoint{
Name: "exec",
Path: "exec",
Post: APIEndpointAction{Handler: execPost},
}
func execPost(d *Daemon, r *http.Request) response.Response {
post := api.ContainerExecPost{}
buf, err := ioutil.ReadAll(r.Body)
if err != nil {
return response.BadRequest(err)
}
if err := json.Unmarshal(buf, &post); err != nil {
return response.BadRequest(err)
}
env := map[string]string{}
if post.Environment != nil {
for k, v := range post.Environment {
env[k] = v
}
}
// Set default value for PATH
_, ok := env["PATH"]
if !ok {
env["PATH"] = "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
}
if shared.PathExists("/snap/bin") {
env["PATH"] = fmt.Sprintf("%s:/snap/bin", env["PATH"])
}
// If running as root, set some env variables
if post.User == 0 {
// Set default value for HOME
_, ok = env["HOME"]
if !ok {
env["HOME"] = "/root"
}
// Set default value for USER
_, ok = env["USER"]
if !ok {
env["USER"] = "root"
}
}
// Set default value for LANG
_, ok = env["LANG"]
if !ok {
env["LANG"] = "C.UTF-8"
}
// Set the default working directory
if post.Cwd == "" {
post.Cwd = env["HOME"]
if post.Cwd == "" {
post.Cwd = "/"
}
}
ws := &execWs{}
ws.fds = map[int]string{}
ws.conns = map[int]*websocket.Conn{}
ws.conns[-1] = nil
ws.conns[0] = nil
if !post.Interactive {
ws.conns[1] = nil
ws.conns[2] = nil
}
ws.allConnected = make(chan bool, 1)
ws.controlConnected = make(chan bool, 1)
ws.interactive = post.Interactive
for i := -1; i < len(ws.conns)-1; i++ {
ws.fds[i], err = shared.RandomCryptoString()
if err != nil {
return response.InternalError(err)
}
}
ws.command = post.Command
ws.env = env
ws.width = post.Width
ws.height = post.Height
ws.cwd = post.Cwd
ws.uid = post.User
ws.gid = post.Group
resources := map[string][]string{}
op, err := operations.OperationCreate(nil, "", operations.OperationClassWebsocket, db.OperationCommandExec, resources, ws.Metadata(), ws.Do, nil, ws.Connect)
if err != nil {
return response.InternalError(err)
}
// Link the operation to the agent's event server.
op.SetEventServer(d.events)
return operations.OperationResponse(op)
}
type execWs struct {
command []string
env map[string]string
conns map[int]*websocket.Conn
connsLock sync.Mutex
allConnected chan bool
controlConnected chan bool
interactive bool
fds map[int]string
width int
height int
uid uint32
gid uint32
cwd string
}
func (s *execWs) Metadata() interface{} {
fds := shared.Jmap{}
for fd, secret := range s.fds {
if fd == -1 {
fds["control"] = secret
} else {
fds[strconv.Itoa(fd)] = secret
}
}
return shared.Jmap{
"fds": fds,
"command": s.command,
"environment": s.env,
"interactive": s.interactive,
}
}
func (s *execWs) Connect(op *operations.Operation, r *http.Request, w http.ResponseWriter) error {
secret := r.FormValue("secret")
if secret == "" {
return fmt.Errorf("missing secret")
}
for fd, fdSecret := range s.fds {
if secret == fdSecret {
conn, err := shared.WebsocketUpgrader.Upgrade(w, r, nil)
if err != nil {
return err
}
s.connsLock.Lock()
s.conns[fd] = conn
s.connsLock.Unlock()
if fd == -1 {
s.controlConnected <- true
return nil
}
s.connsLock.Lock()
for i, c := range s.conns {
if i != -1 && c == nil {
s.connsLock.Unlock()
return nil
}
}
s.connsLock.Unlock()
s.allConnected <- true
return nil
}
}
/* If we didn't find the right secret, the user provided a bad one,
* which 403, not 404, since this Operation actually exists */
return os.ErrPermission
}
func (s *execWs) Do(op *operations.Operation) error {
<-s.allConnected
var err error
var ttys []*os.File
var ptys []*os.File
var stdin *os.File
var stdout *os.File
var stderr *os.File
if s.interactive {
ttys = make([]*os.File, 1)
ptys = make([]*os.File, 1)
ptys[0], ttys[0], err = shared.OpenPty(int64(s.uid), int64(s.gid))
if err != nil {
return err
}
stdin = ttys[0]
stdout = ttys[0]
stderr = ttys[0]
if s.width > 0 && s.height > 0 {
shared.SetSize(int(ptys[0].Fd()), s.width, s.height)
}
} else {
ttys = make([]*os.File, 3)
ptys = make([]*os.File, 3)
for i := 0; i < len(ttys); i++ {
ptys[i], ttys[i], err = os.Pipe()
if err != nil {
return err
}
}
stdin = ptys[0]
stdout = ttys[1]
stderr = ttys[2]
}
controlExit := make(chan bool, 1)
attachedChildIsBorn := make(chan int)
attachedChildIsDead := make(chan struct{})
var wgEOF sync.WaitGroup
if s.interactive {
wgEOF.Add(1)
go func() {
logger.Debugf("Interactive child process handler waiting")
defer logger.Debugf("Interactive child process handler finished")
attachedChildPid := <-attachedChildIsBorn
select {
case <-s.controlConnected:
break
case <-controlExit:
return
}
logger.Debugf("Interactive child process handler started for child PID %d", attachedChildPid)
for {
s.connsLock.Lock()
conn := s.conns[-1]
s.connsLock.Unlock()
mt, r, err := conn.NextReader()
if mt == websocket.CloseMessage {
break
}
if err != nil {
logger.Debugf("Got error getting next reader for child PID %d: %v", attachedChildPid, err)
er, ok := err.(*websocket.CloseError)
if !ok {
break
}
if er.Code != websocket.CloseAbnormalClosure {
break
}
// If an abnormal closure occurred, kill the attached process.
err := unix.Kill(attachedChildPid, unix.SIGKILL)
if err != nil {
logger.Errorf("Failed to send SIGKILL to pid %d", attachedChildPid)
} else {
logger.Infof("Sent SIGKILL to pid %d", attachedChildPid)
}
return
}
buf, err := ioutil.ReadAll(r)
if err != nil {
logger.Errorf("Failed to read message %s", err)
break
}
command := api.ContainerExecControl{}
if err := json.Unmarshal(buf, &command); err != nil {
logger.Errorf("Failed to unmarshal control socket command: %s", err)
continue
}
if command.Command == "window-resize" {
winchWidth, err := strconv.Atoi(command.Args["width"])
if err != nil {
logger.Errorf("Unable to extract window width: %s", err)
continue
}
winchHeight, err := strconv.Atoi(command.Args["height"])
if err != nil {
logger.Errorf("Unable to extract window height: %s", err)
continue
}
err = shared.SetSize(int(ptys[0].Fd()), winchWidth, winchHeight)
if err != nil {
logger.Errorf("Failed to set window size to: %dx%d", winchWidth, winchHeight)
continue
}
} else if command.Command == "signal" {
if err := unix.Kill(attachedChildPid, unix.Signal(command.Signal)); err != nil {
logger.Errorf("Failed forwarding signal '%d' to PID %d", command.Signal, attachedChildPid)
continue
}
logger.Infof("Forwarded signal '%d' to PID %d", command.Signal, attachedChildPid)
}
}
}()
go func() {
s.connsLock.Lock()
conn := s.conns[0]
s.connsLock.Unlock()
logger.Info("Started mirroring websocket")
readDone, writeDone := netutils.WebsocketExecMirror(conn, ptys[0], ptys[0], attachedChildIsDead, int(ptys[0].Fd()))
<-readDone
<-writeDone
logger.Info("Finished mirroring websocket")
conn.Close()
wgEOF.Done()
}()
} else {
wgEOF.Add(len(ttys) - 1)
for i := 0; i < len(ttys); i++ {
go func(i int) {
if i == 0 {
s.connsLock.Lock()
conn := s.conns[i]
s.connsLock.Unlock()
<-shared.WebsocketRecvStream(ttys[i], conn)
ttys[i].Close()
} else {
s.connsLock.Lock()
conn := s.conns[i]
s.connsLock.Unlock()
<-shared.WebsocketSendStream(conn, ptys[i], -1)
ptys[i].Close()
wgEOF.Done()
}
}(i)
}
}
finisher := func(cmdResult int, cmdErr error) error {
for _, tty := range ttys {
tty.Close()
}
s.connsLock.Lock()
conn := s.conns[-1]
s.connsLock.Unlock()
if conn == nil {
if s.interactive {
controlExit <- true
}
} else {
conn.Close()
}
close(attachedChildIsDead)
wgEOF.Wait()
for _, pty := range ptys {
pty.Close()
}
metadata := shared.Jmap{"return": cmdResult}
err = op.UpdateMetadata(metadata)
if err != nil {
return err
}
return cmdErr
}
var cmd *exec.Cmd
if len(s.command) > 1 {
cmd = exec.Command(s.command[0], s.command[1:]...)
} else {
cmd = exec.Command(s.command[0])
}
// Prepare the environment
for k, v := range s.env {
cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%s", k, v))
}
cmd.Stdin = stdin
cmd.Stdout = stdout
cmd.Stderr = stderr
cmd.SysProcAttr = &syscall.SysProcAttr{
Credential: &syscall.Credential{
Uid: s.uid,
Gid: s.gid,
},
// Creates a new session if the calling process is not a process group leader.
// The calling process is the leader of the new session, the process group leader of
// the new process group, and has no controlling terminal.
// This is important to allow remote shells to handle ctrl+c.
Setsid: true,
}
// Make the given terminal the controlling terminal of the calling process.
// The calling process must be a session leader and not have a controlling terminal already.
// This is important as allows ctrl+c to work as expected for non-shell programs.
if s.interactive {
cmd.SysProcAttr.Setctty = true
}
cmd.Dir = s.cwd
err = cmd.Start()
if err != nil {
return finisher(-1, err)
}
if s.interactive {
attachedChildIsBorn <- cmd.Process.Pid
}
err = cmd.Wait()
if err == nil {
return finisher(0, nil)
}
exitErr, ok := err.(*exec.ExitError)
if ok {
status, ok := exitErr.Sys().(syscall.WaitStatus)
if ok {
return finisher(status.ExitStatus(), nil)
}
if status.Signaled() {
// 128 + n == Fatal error signal "n"
return finisher(128+int(status.Signal()), nil)
}
}
return finisher(-1, nil)
}