subgraph-oz/oz-init/init.go

package ozinit

import (
	"os"
	"github.com/subgraph/oz"
	"github.com/subgraph/oz/fs"
	"github.com/subgraph/oz/ipc"
	"os/exec"
	"syscall"
	"github.com/op/go-logging"
	"github.com/kr/pty"
	"fmt"
	"github.com/subgraph/oz/xpra"
	"os/user"
	"strconv"
	"io"
	"bufio"
	"strings"
)

const profileDirectory = "/var/lib/oz/cells.d"

type initState struct {
	log *logging.Logger
	address string
	profile *oz.Profile
	uid int
	gid int
	user *user.User
	display int
	fs *fs.Filesystem
}

// By convention oz-init writes log messages to stderr with a single character
// prefix indicating the logging level.  These messages are read one line at a time
// over a pipe by oz-daemon and translated into appropriate log events.
func createLogger() *logging.Logger {
	l := logging.MustGetLogger("oz-init")
	be := logging.NewLogBackend(os.Stderr, "", 0)
	f := logging.MustStringFormatter("%{level:.1s} %{message}")
	fbe := logging.NewBackendFormatter(be,f)
	logging.SetBackend(fbe)
	return l
}

var allowRootShell = false
var logXpra = true

func Main() {
	st := parseArgs()
	st.runInit()
}

func parseArgs() *initState {
	log := createLogger()
	getvar := func(name string) string {
		val := os.Getenv(name)
		if val == "" {
			log.Error("Error: missing required '%s' argument", name)
			os.Exit(1)
		}
		return val
	}
	addr := getvar("INIT_ADDRESS")
	pname := getvar("INIT_PROFILE")
	uidval := getvar("INIT_UID")
	dispval := os.Getenv("INIT_DISPLAY")

	p,err := loadProfile(pname)
	if err != nil {
		log.Error("Could not load profile %s: %v", pname, err)
		os.Exit(1)
	}
	uid,err := strconv.Atoi(uidval)
	if err != nil {
		log.Error("Could not parse INIT_UID argument (%s) into an integer: %v", uidval, err)
		os.Exit(1)
	}
	u,err := user.LookupId(uidval)
	if err != nil {
		log.Error("Failed to look up user with uid=%s: %v", uidval, err)
		os.Exit(1)
	}
	gid,err := strconv.Atoi(u.Gid)
	if err != nil {
		log.Error("Failed to parse gid value (%s) from user struct: %v", u.Gid, err)
		os.Exit(1)
	}
	display := 0
	if dispval != "" {
		d,err := strconv.Atoi(dispval)
		if err != nil {
			log.Error("Unable to parse display (%s) into an integer: %v", dispval, err)
			os.Exit(1)
		}
		display = d
	}

	return &initState{
		log: log,
		address: addr,
		profile: p,
		uid: uid,
		gid: gid,
		user: u,
		display: display,
		fs: fs.NewFromProfile(p, u, log),
	}
}

func (st *initState) runInit() {
	st.log.Info("Starting oz-init for profile: %s", st.profile.Name)
	st.log.Info("Socket address: %s", st.address)
	if err := st.fs.OzInit(); err != nil {
		st.log.Error("Error: setting up filesystem failed: %v\n", err)
		os.Exit(1)
	}
	if st.profile.XServer.Enabled {
		if st.display == 0 {
			st.log.Error("Cannot start xpra because no display number was passed to oz-init")
			os.Exit(1)
		}
		st.startXpraServer()
	}

	oz.ReapChildProcs(st.log, st.handleChildExit)

	serv := ipc.NewMsgConn(messageFactory, st.address)
	serv.AddHandlers(
		handlePing,
		st.handleRunShell,
	)
	serv.Listen()
	serv.Run()
	st.log.Info("oz-init exiting...")
}

func (st *initState) startXpraServer() {
	workdir := st.fs.Xpra()
	if workdir == "" {
		st.log.Warning("Xpra work directory not set")
		return
	}
	xpra := xpra.NewServer(&st.profile.XServer, uint64(st.display), workdir)
	p,err := xpra.Process.StderrPipe()
	if err != nil {
		st.log.Warning("Error creating stderr pipe for xpra output: %v", err)
		os.Exit(1)
	}
	go st.readXpraOutput(p)
	xpra.Process.Env = []string{
		"HOME="+ st.user.HomeDir,
	}
	xpra.Process.SysProcAttr = &syscall.SysProcAttr{}
	xpra.Process.SysProcAttr.Credential = &syscall.Credential{
		Uid: uint32(st.uid),
		Gid: uint32(st.gid),
	}
	st.log.Info("Starting xpra server")
	if err := xpra.Process.Start(); err != nil {
		st.log.Warning("Failed to start xpra server: %v", err)
	}
}

func (st *initState) readXpraOutput(r io.ReadCloser) {
	sc := bufio.NewScanner(r)
	for sc.Scan() {
		line := sc.Text()
		if len(line) > 0 {
			if strings.Contains(line, "xpra is ready.") {
				os.Stderr.WriteString("XPRA READY\n")
				if !logXpra {
					r.Close()
					return
				}
			}
			if logXpra {
				st.log.Debug("(xpra) %s", line)
			}
		}
	}
}

func loadProfile(name string) (*oz.Profile, error) {
	ps,err := oz.LoadProfiles(profileDirectory)
	if err != nil {
		return nil, err
	}
	for _,p := range ps {
		if name == p.Name {
			return p, nil
		}
	}
	return nil, fmt.Errorf("no profile named '%s'", name)
}

func handlePing(ping *PingMsg, msg *ipc.Message) error {
	return msg.Respond(&PingMsg{Data: ping.Data})
}

func (st *initState) handleRunShell(rs *RunShellMsg, msg *ipc.Message) error {
	if msg.Ucred == nil {
		return msg.Respond(&ErrorMsg{"No credentials received for RunShell command"})
	}
	if msg.Ucred.Uid == 0 || msg.Ucred.Gid == 0 && !allowRootShell {
		return msg.Respond(&ErrorMsg{"Cannot open shell because allowRootShell is disabled"})
	}
	st.log.Info("Starting shell with uid = %d, gid = %d", msg.Ucred.Uid, msg.Ucred.Gid)
	cmd := exec.Command("/bin/sh", "-i")
	cmd.SysProcAttr = &syscall.SysProcAttr{}
	cmd.SysProcAttr.Credential = &syscall.Credential{
		Uid: msg.Ucred.Uid,
		Gid: msg.Ucred.Gid,
	}
	if rs.Term != "" {
		cmd.Env = append(cmd.Env, "TERM="+rs.Term)
	}
	cmd.Env = append(cmd.Env, "PATH=/usr/bin:/bin")
	cmd.Env = append(cmd.Env, fmt.Sprintf("PS1=[%s] $ ", st.profile.Name))
	st.log.Info("Executing shell...")
	f,err := ptyStart(cmd)
	defer f.Close()
	if err != nil {
		return msg.Respond(&ErrorMsg{err.Error()})
	}
	err = msg.Respond(&OkMsg{}, int(f.Fd()))
	return err
}

func ptyStart(c *exec.Cmd) (ptty *os.File, err error) {
	ptty,tty, err := pty.Open()
	if err != nil {
		return nil, err
	}
	defer tty.Close()
	c.Stdin = tty
	c.Stdout = tty
	c.Stderr = tty
	if c.SysProcAttr == nil {
		c.SysProcAttr = &syscall.SysProcAttr{}
	}
	c.SysProcAttr.Setctty = true
	c.SysProcAttr.Setsid = true
	if err := c.Start(); err != nil {
		ptty.Close()
		return nil, err
	}
	return ptty, nil
}

func (is *initState) handleChildExit(pid int, wstatus syscall.WaitStatus) {
	is.log.Debug("Child process pid=%d exited with status %d", pid, wstatus.ExitStatus())
}