/usr/share/gocode/src/github.com/opencontainers/runc/libcontainer/init_linux.go is in golang-github-opencontainers-runc-dev 1.0.0~rc4+dfsg1-6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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package libcontainer
import (
"encoding/json"
"fmt"
"io"
"net"
"os"
"strings"
"syscall" // only for Errno
"unsafe"
"github.com/opencontainers/runc/libcontainer/cgroups"
"github.com/opencontainers/runc/libcontainer/configs"
"github.com/opencontainers/runc/libcontainer/system"
"github.com/opencontainers/runc/libcontainer/user"
"github.com/opencontainers/runc/libcontainer/utils"
"github.com/sirupsen/logrus"
"github.com/vishvananda/netlink"
"golang.org/x/sys/unix"
)
type initType string
const (
initSetns initType = "setns"
initStandard initType = "standard"
)
type pid struct {
Pid int `json:"pid"`
}
// network is an internal struct used to setup container networks.
type network struct {
configs.Network
// TempVethPeerName is a unique temporary veth peer name that was placed into
// the container's namespace.
TempVethPeerName string `json:"temp_veth_peer_name"`
}
// initConfig is used for transferring parameters from Exec() to Init()
type initConfig struct {
Args []string `json:"args"`
Env []string `json:"env"`
Cwd string `json:"cwd"`
Capabilities *configs.Capabilities `json:"capabilities"`
ProcessLabel string `json:"process_label"`
AppArmorProfile string `json:"apparmor_profile"`
NoNewPrivileges bool `json:"no_new_privileges"`
User string `json:"user"`
AdditionalGroups []string `json:"additional_groups"`
Config *configs.Config `json:"config"`
Networks []*network `json:"network"`
PassedFilesCount int `json:"passed_files_count"`
ContainerId string `json:"containerid"`
Rlimits []configs.Rlimit `json:"rlimits"`
CreateConsole bool `json:"create_console"`
Rootless bool `json:"rootless"`
}
type initer interface {
Init() error
}
func newContainerInit(t initType, pipe *os.File, consoleSocket *os.File, stateDirFD int) (initer, error) {
var config *initConfig
if err := json.NewDecoder(pipe).Decode(&config); err != nil {
return nil, err
}
if err := populateProcessEnvironment(config.Env); err != nil {
return nil, err
}
switch t {
case initSetns:
return &linuxSetnsInit{
pipe: pipe,
consoleSocket: consoleSocket,
config: config,
}, nil
case initStandard:
return &linuxStandardInit{
pipe: pipe,
consoleSocket: consoleSocket,
parentPid: unix.Getppid(),
config: config,
stateDirFD: stateDirFD,
}, nil
}
return nil, fmt.Errorf("unknown init type %q", t)
}
// populateProcessEnvironment loads the provided environment variables into the
// current processes's environment.
func populateProcessEnvironment(env []string) error {
for _, pair := range env {
p := strings.SplitN(pair, "=", 2)
if len(p) < 2 {
return fmt.Errorf("invalid environment '%v'", pair)
}
if err := os.Setenv(p[0], p[1]); err != nil {
return err
}
}
return nil
}
// finalizeNamespace drops the caps, sets the correct user
// and working dir, and closes any leaked file descriptors
// before executing the command inside the namespace
func finalizeNamespace(config *initConfig) error {
// Ensure that all unwanted fds we may have accidentally
// inherited are marked close-on-exec so they stay out of the
// container
if err := utils.CloseExecFrom(config.PassedFilesCount + 3); err != nil {
return err
}
capabilities := &configs.Capabilities{}
if config.Capabilities != nil {
capabilities = config.Capabilities
} else if config.Config.Capabilities != nil {
capabilities = config.Config.Capabilities
}
w, err := newContainerCapList(capabilities)
if err != nil {
return err
}
// drop capabilities in bounding set before changing user
if err := w.ApplyBoundingSet(); err != nil {
return err
}
// preserve existing capabilities while we change users
if err := system.SetKeepCaps(); err != nil {
return err
}
if err := setupUser(config); err != nil {
return err
}
if err := system.ClearKeepCaps(); err != nil {
return err
}
if err := w.ApplyCaps(); err != nil {
return err
}
if config.Cwd != "" {
if err := unix.Chdir(config.Cwd); err != nil {
return fmt.Errorf("chdir to cwd (%q) set in config.json failed: %v", config.Cwd, err)
}
}
return nil
}
// setupConsole sets up the console from inside the container, and sends the
// master pty fd to the config.Pipe (using cmsg). This is done to ensure that
// consoles are scoped to a container properly (see runc#814 and the many
// issues related to that). This has to be run *after* we've pivoted to the new
// rootfs (and the users' configuration is entirely set up).
func setupConsole(socket *os.File, config *initConfig, mount bool) error {
defer socket.Close()
// At this point, /dev/ptmx points to something that we would expect. We
// used to change the owner of the slave path, but since the /dev/pts mount
// can have gid=X set (at the users' option). So touching the owner of the
// slave PTY is not necessary, as the kernel will handle that for us. Note
// however, that setupUser (specifically fixStdioPermissions) *will* change
// the UID owner of the console to be the user the process will run as (so
// they can actually control their console).
console, err := newConsole()
if err != nil {
return err
}
// After we return from here, we don't need the console anymore.
defer console.Close()
linuxConsole, ok := console.(*linuxConsole)
if !ok {
return fmt.Errorf("failed to cast console to *linuxConsole")
}
// Mount the console inside our rootfs.
if mount {
if err := linuxConsole.mount(); err != nil {
return err
}
}
// While we can access console.master, using the API is a good idea.
if err := utils.SendFd(socket, linuxConsole.File()); err != nil {
return err
}
// Now, dup over all the things.
return linuxConsole.dupStdio()
}
// syncParentReady sends to the given pipe a JSON payload which indicates that
// the init is ready to Exec the child process. It then waits for the parent to
// indicate that it is cleared to Exec.
func syncParentReady(pipe io.ReadWriter) error {
// Tell parent.
if err := writeSync(pipe, procReady); err != nil {
return err
}
// Wait for parent to give the all-clear.
if err := readSync(pipe, procRun); err != nil {
return err
}
return nil
}
// syncParentHooks sends to the given pipe a JSON payload which indicates that
// the parent should execute pre-start hooks. It then waits for the parent to
// indicate that it is cleared to resume.
func syncParentHooks(pipe io.ReadWriter) error {
// Tell parent.
if err := writeSync(pipe, procHooks); err != nil {
return err
}
// Wait for parent to give the all-clear.
if err := readSync(pipe, procResume); err != nil {
return err
}
return nil
}
// setupUser changes the groups, gid, and uid for the user inside the container
func setupUser(config *initConfig) error {
// Set up defaults.
defaultExecUser := user.ExecUser{
Uid: 0,
Gid: 0,
Home: "/",
}
passwdPath, err := user.GetPasswdPath()
if err != nil {
return err
}
groupPath, err := user.GetGroupPath()
if err != nil {
return err
}
execUser, err := user.GetExecUserPath(config.User, &defaultExecUser, passwdPath, groupPath)
if err != nil {
return err
}
var addGroups []int
if len(config.AdditionalGroups) > 0 {
addGroups, err = user.GetAdditionalGroupsPath(config.AdditionalGroups, groupPath)
if err != nil {
return err
}
}
if config.Rootless {
if execUser.Uid != 0 {
return fmt.Errorf("cannot run as a non-root user in a rootless container")
}
if execUser.Gid != 0 {
return fmt.Errorf("cannot run as a non-root group in a rootless container")
}
// We cannot set any additional groups in a rootless container and thus we
// bail if the user asked us to do so. TODO: We currently can't do this
// earlier, but if libcontainer.Process.User was typesafe this might work.
if len(addGroups) > 0 {
return fmt.Errorf("cannot set any additional groups in a rootless container")
}
}
// before we change to the container's user make sure that the processes STDIO
// is correctly owned by the user that we are switching to.
if err := fixStdioPermissions(config, execUser); err != nil {
return err
}
// This isn't allowed in an unprivileged user namespace since Linux 3.19.
// There's nothing we can do about /etc/group entries, so we silently
// ignore setting groups here (since the user didn't explicitly ask us to
// set the group).
if !config.Rootless {
suppGroups := append(execUser.Sgids, addGroups...)
if err := unix.Setgroups(suppGroups); err != nil {
return err
}
}
if err := system.Setgid(execUser.Gid); err != nil {
return err
}
if err := system.Setuid(execUser.Uid); err != nil {
return err
}
// if we didn't get HOME already, set it based on the user's HOME
if envHome := os.Getenv("HOME"); envHome == "" {
if err := os.Setenv("HOME", execUser.Home); err != nil {
return err
}
}
return nil
}
// fixStdioPermissions fixes the permissions of PID 1's STDIO within the container to the specified user.
// The ownership needs to match because it is created outside of the container and needs to be
// localized.
func fixStdioPermissions(config *initConfig, u *user.ExecUser) error {
var null unix.Stat_t
if err := unix.Stat("/dev/null", &null); err != nil {
return err
}
for _, fd := range []uintptr{
os.Stdin.Fd(),
os.Stderr.Fd(),
os.Stdout.Fd(),
} {
var s unix.Stat_t
if err := unix.Fstat(int(fd), &s); err != nil {
return err
}
// Skip chown of /dev/null if it was used as one of the STDIO fds.
if s.Rdev == null.Rdev {
continue
}
// Skip chown if s.Gid is actually an unmapped gid in the host. While
// this is a bit dodgy if it just so happens that the console _is_
// owned by overflow_gid, there's no way for us to disambiguate this as
// a userspace program.
if _, err := config.Config.HostGID(int(s.Gid)); err != nil {
continue
}
// We only change the uid owner (as it is possible for the mount to
// prefer a different gid, and there's no reason for us to change it).
// The reason why we don't just leave the default uid=X mount setup is
// that users expect to be able to actually use their console. Without
// this code, you couldn't effectively run as a non-root user inside a
// container and also have a console set up.
if err := unix.Fchown(int(fd), u.Uid, int(s.Gid)); err != nil {
return err
}
}
return nil
}
// setupNetwork sets up and initializes any network interface inside the container.
func setupNetwork(config *initConfig) error {
for _, config := range config.Networks {
strategy, err := getStrategy(config.Type)
if err != nil {
return err
}
if err := strategy.initialize(config); err != nil {
return err
}
}
return nil
}
func setupRoute(config *configs.Config) error {
for _, config := range config.Routes {
_, dst, err := net.ParseCIDR(config.Destination)
if err != nil {
return err
}
src := net.ParseIP(config.Source)
if src == nil {
return fmt.Errorf("Invalid source for route: %s", config.Source)
}
gw := net.ParseIP(config.Gateway)
if gw == nil {
return fmt.Errorf("Invalid gateway for route: %s", config.Gateway)
}
l, err := netlink.LinkByName(config.InterfaceName)
if err != nil {
return err
}
route := &netlink.Route{
Scope: netlink.SCOPE_UNIVERSE,
Dst: dst,
Src: src,
Gw: gw,
LinkIndex: l.Attrs().Index,
}
if err := netlink.RouteAdd(route); err != nil {
return err
}
}
return nil
}
func setupRlimits(limits []configs.Rlimit, pid int) error {
for _, rlimit := range limits {
if err := system.Prlimit(pid, rlimit.Type, unix.Rlimit{Max: rlimit.Hard, Cur: rlimit.Soft}); err != nil {
return fmt.Errorf("error setting rlimit type %v: %v", rlimit.Type, err)
}
}
return nil
}
const _P_PID = 1
type siginfo struct {
si_signo int32
si_errno int32
si_code int32
// below here is a union; si_pid is the only field we use
si_pid int32
// Pad to 128 bytes as detailed in blockUntilWaitable
pad [96]byte
}
// isWaitable returns true if the process has exited false otherwise.
// Its based off blockUntilWaitable in src/os/wait_waitid.go
func isWaitable(pid int) (bool, error) {
si := &siginfo{}
_, _, e := unix.Syscall6(unix.SYS_WAITID, _P_PID, uintptr(pid), uintptr(unsafe.Pointer(si)), unix.WEXITED|unix.WNOWAIT|unix.WNOHANG, 0, 0)
if e != 0 {
return false, os.NewSyscallError("waitid", e)
}
return si.si_pid != 0, nil
}
// isNoChildren returns true if err represents a unix.ECHILD (formerly syscall.ECHILD) false otherwise
func isNoChildren(err error) bool {
switch err := err.(type) {
case syscall.Errno:
if err == unix.ECHILD {
return true
}
case *os.SyscallError:
if err.Err == unix.ECHILD {
return true
}
}
return false
}
// signalAllProcesses freezes then iterates over all the processes inside the
// manager's cgroups sending the signal s to them.
// If s is SIGKILL then it will wait for each process to exit.
// For all other signals it will check if the process is ready to report its
// exit status and only if it is will a wait be performed.
func signalAllProcesses(m cgroups.Manager, s os.Signal) error {
var procs []*os.Process
if err := m.Freeze(configs.Frozen); err != nil {
logrus.Warn(err)
}
pids, err := m.GetAllPids()
if err != nil {
m.Freeze(configs.Thawed)
return err
}
for _, pid := range pids {
p, err := os.FindProcess(pid)
if err != nil {
logrus.Warn(err)
continue
}
procs = append(procs, p)
if err := p.Signal(s); err != nil {
logrus.Warn(err)
}
}
if err := m.Freeze(configs.Thawed); err != nil {
logrus.Warn(err)
}
for _, p := range procs {
if s != unix.SIGKILL {
if ok, err := isWaitable(p.Pid); err != nil {
if !isNoChildren(err) {
logrus.Warn("signalAllProcesses: ", p.Pid, err)
}
continue
} else if !ok {
// Not ready to report so don't wait
continue
}
}
if _, err := p.Wait(); err != nil {
if !isNoChildren(err) {
logrus.Warn("wait: ", err)
}
}
}
return nil
}
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