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// +build linux
package libcontainer
import (
"fmt"
"os"
"os/exec"
"syscall" //only for Exec
"github.com/opencontainers/runc/libcontainer/apparmor"
"github.com/opencontainers/runc/libcontainer/configs"
"github.com/opencontainers/runc/libcontainer/keys"
"github.com/opencontainers/runc/libcontainer/seccomp"
"github.com/opencontainers/runc/libcontainer/system"
"github.com/opencontainers/selinux/go-selinux/label"
"golang.org/x/sys/unix"
)
type linuxStandardInit struct {
pipe *os.File
consoleSocket *os.File
parentPid int
stateDirFD int
config *initConfig
}
func (l *linuxStandardInit) getSessionRingParams() (string, uint32, uint32) {
var newperms uint32
if l.config.Config.Namespaces.Contains(configs.NEWUSER) {
// with user ns we need 'other' search permissions
newperms = 0x8
} else {
// without user ns we need 'UID' search permissions
newperms = 0x80000
}
// create a unique per session container name that we can
// join in setns; however, other containers can also join it
return fmt.Sprintf("_ses.%s", l.config.ContainerId), 0xffffffff, newperms
}
func (l *linuxStandardInit) Init() error {
if !l.config.Config.NoNewKeyring {
ringname, keepperms, newperms := l.getSessionRingParams()
// do not inherit the parent's session keyring
sessKeyId, err := keys.JoinSessionKeyring(ringname)
if err != nil {
return err
}
// make session keyring searcheable
if err := keys.ModKeyringPerm(sessKeyId, keepperms, newperms); err != nil {
return err
}
}
if err := setupNetwork(l.config); err != nil {
return err
}
if err := setupRoute(l.config.Config); err != nil {
return err
}
label.Init()
// prepareRootfs() can be executed only for a new mount namespace.
if l.config.Config.Namespaces.Contains(configs.NEWNS) {
if err := prepareRootfs(l.pipe, l.config.Config); err != nil {
return err
}
}
// Set up the console. This has to be done *before* we finalize the rootfs,
// but *after* we've given the user the chance to set up all of the mounts
// they wanted.
if l.config.CreateConsole {
if err := setupConsole(l.consoleSocket, l.config, true); err != nil {
return err
}
if err := system.Setctty(); err != nil {
return err
}
}
// Finish the rootfs setup.
if l.config.Config.Namespaces.Contains(configs.NEWNS) {
if err := finalizeRootfs(l.config.Config); err != nil {
return err
}
}
if hostname := l.config.Config.Hostname; hostname != "" {
if err := unix.Sethostname([]byte(hostname)); err != nil {
return err
}
}
if err := apparmor.ApplyProfile(l.config.AppArmorProfile); err != nil {
return err
}
if err := label.SetProcessLabel(l.config.ProcessLabel); err != nil {
return err
}
for key, value := range l.config.Config.Sysctl {
if err := writeSystemProperty(key, value); err != nil {
return err
}
}
for _, path := range l.config.Config.ReadonlyPaths {
if err := readonlyPath(path); err != nil {
return err
}
}
for _, path := range l.config.Config.MaskPaths {
if err := maskPath(path); err != nil {
return err
}
}
pdeath, err := system.GetParentDeathSignal()
if err != nil {
return err
}
if l.config.NoNewPrivileges {
if err := unix.Prctl(unix.PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); err != nil {
return err
}
}
// Tell our parent that we're ready to Execv. This must be done before the
// Seccomp rules have been applied, because we need to be able to read and
// write to a socket.
if err := syncParentReady(l.pipe); err != nil {
return err
}
// Without NoNewPrivileges seccomp is a privileged operation, so we need to
// do this before dropping capabilities; otherwise do it as late as possible
// just before execve so as few syscalls take place after it as possible.
if l.config.Config.Seccomp != nil && !l.config.NoNewPrivileges {
if err := seccomp.InitSeccomp(l.config.Config.Seccomp); err != nil {
return err
}
}
if err := finalizeNamespace(l.config); err != nil {
return err
}
// finalizeNamespace can change user/group which clears the parent death
// signal, so we restore it here.
if err := pdeath.Restore(); err != nil {
return err
}
// compare the parent from the initial start of the init process and make sure that it did not change.
// if the parent changes that means it died and we were reparented to something else so we should
// just kill ourself and not cause problems for someone else.
if unix.Getppid() != l.parentPid {
return unix.Kill(unix.Getpid(), unix.SIGKILL)
}
// check for the arg before waiting to make sure it exists and it is returned
// as a create time error.
name, err := exec.LookPath(l.config.Args[0])
if err != nil {
return err
}
// close the pipe to signal that we have completed our init.
l.pipe.Close()
// wait for the fifo to be opened on the other side before
// exec'ing the users process.
fd, err := unix.Openat(l.stateDirFD, execFifoFilename, os.O_WRONLY|unix.O_CLOEXEC, 0)
if err != nil {
return newSystemErrorWithCause(err, "openat exec fifo")
}
if _, err := unix.Write(fd, []byte("0")); err != nil {
return newSystemErrorWithCause(err, "write 0 exec fifo")
}
if l.config.Config.Seccomp != nil && l.config.NoNewPrivileges {
if err := seccomp.InitSeccomp(l.config.Config.Seccomp); err != nil {
return newSystemErrorWithCause(err, "init seccomp")
}
}
// close the statedir fd before exec because the kernel resets dumpable in the wrong order
// https://github.com/torvalds/linux/blob/v4.9/fs/exec.c#L1290-L1318
unix.Close(l.stateDirFD)
if err := syscall.Exec(name, l.config.Args[0:], os.Environ()); err != nil {
return newSystemErrorWithCause(err, "exec user process")
}
return nil
}
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