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Aug 15, 2016
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157 changes: 10 additions & 147 deletions util/util.go
Original file line number Diff line number Diff line change
Expand Up @@ -18,96 +18,23 @@
// than linking against them.
package util

// #include <stdlib.h>
// #include <sys/types.h>
// #include <unistd.h>
//
// int
// my_sd_pid_get_owner_uid(void *f, pid_t pid, uid_t *uid)
// {
// int (*sd_pid_get_owner_uid)(pid_t, uid_t *);
//
// sd_pid_get_owner_uid = (int (*)(pid_t, uid_t *))f;
// return sd_pid_get_owner_uid(pid, uid);
// }
//
// int
// my_sd_pid_get_unit(void *f, pid_t pid, char **unit)
// {
// int (*sd_pid_get_unit)(pid_t, char **);
//
// sd_pid_get_unit = (int (*)(pid_t, char **))f;
// return sd_pid_get_unit(pid, unit);
// }
//
// int
// my_sd_pid_get_slice(void *f, pid_t pid, char **slice)
// {
// int (*sd_pid_get_slice)(pid_t, char **);
//
// sd_pid_get_slice = (int (*)(pid_t, char **))f;
// return sd_pid_get_slice(pid, slice);
// }
//
// int
// am_session_leader()
// {
// return (getsid(0) == getpid());
// }
import "C"
import (
"fmt"
"io/ioutil"
"os"
"strings"
"syscall"
"unsafe"

"github.com/coreos/pkg/dlopen"
)

var libsystemdNames = []string{
// systemd < 209
"libsystemd-login.so.0",
"libsystemd-login.so",

// systemd >= 209 merged libsystemd-login into libsystemd proper
"libsystemd.so.0",
"libsystemd.so",
}
var (
ErrNoCGO = fmt.Errorf("go-systemd built with CGO disabled")
)

// GetRunningSlice attempts to retrieve the name of the systemd slice in which
// the current process is running.
// This function is a wrapper around the libsystemd C library; if it cannot be
// opened, an error is returned.
func GetRunningSlice() (slice string, err error) {
var h *dlopen.LibHandle
h, err = dlopen.GetHandle(libsystemdNames)
if err != nil {
return
}
defer func() {
if err1 := h.Close(); err1 != nil {
err = err1
}
}()

sd_pid_get_slice, err := h.GetSymbolPointer("sd_pid_get_slice")
if err != nil {
return
}

var s string
sl := C.CString(s)
defer C.free(unsafe.Pointer(sl))

ret := C.my_sd_pid_get_slice(sd_pid_get_slice, 0, &sl)
if ret < 0 {
err = fmt.Errorf("error calling sd_pid_get_slice: %v", syscall.Errno(-ret))
return
}

return C.GoString(sl), nil
func GetRunningSlice() (string, error) {
return getRunningSlice()
}

// RunningFromSystemService tries to detect whether the current process has
Expand All @@ -125,81 +52,17 @@ func GetRunningSlice() (slice string, err error) {
//
// This function is a wrapper around the libsystemd C library; if this is
// unable to successfully open a handle to the library for any reason (e.g. it
// cannot be found), an errr will be returned
func RunningFromSystemService() (ret bool, err error) {
var h *dlopen.LibHandle
h, err = dlopen.GetHandle(libsystemdNames)
if err != nil {
return
}
defer func() {
if err1 := h.Close(); err1 != nil {
err = err1
}
}()

sd_pid_get_owner_uid, err := h.GetSymbolPointer("sd_pid_get_owner_uid")
if err != nil {
return
}

var uid C.uid_t
errno := C.my_sd_pid_get_owner_uid(sd_pid_get_owner_uid, 0, &uid)
serrno := syscall.Errno(-errno)
// when we're running from a unit file, sd_pid_get_owner_uid returns
// ENOENT (systemd <220) or ENXIO (systemd >=220)
switch {
case errno >= 0:
ret = false
case serrno == syscall.ENOENT, serrno == syscall.ENXIO:
// Since the implementation of sessions in systemd relies on
// the `pam_systemd` module, using the sd_pid_get_owner_uid
// heuristic alone can result in false positives if that module
// (or PAM itself) is not present or properly configured on the
// system. As such, we also check if we're the session leader,
// which should be the case if we're invoked from a unit file,
// but not if e.g. we're invoked from the command line from a
// user's login session
ret = C.am_session_leader() == 1
default:
err = fmt.Errorf("error calling sd_pid_get_owner_uid: %v", syscall.Errno(-errno))
}
return
// cannot be found), an error will be returned.
func RunningFromSystemService() (bool, error) {
return runningFromSystemService()
}

// CurrentUnitName attempts to retrieve the name of the systemd system unit
// from which the calling process has been invoked. It wraps the systemd
// `sd_pid_get_unit` call, with the same caveat: for processes not part of a
// systemd system unit, this function will return an error.
func CurrentUnitName() (unit string, err error) {
var h *dlopen.LibHandle
h, err = dlopen.GetHandle(libsystemdNames)
if err != nil {
return
}
defer func() {
if err1 := h.Close(); err1 != nil {
err = err1
}
}()

sd_pid_get_unit, err := h.GetSymbolPointer("sd_pid_get_unit")
if err != nil {
return
}

var s string
u := C.CString(s)
defer C.free(unsafe.Pointer(u))

ret := C.my_sd_pid_get_unit(sd_pid_get_unit, 0, &u)
if ret < 0 {
err = fmt.Errorf("error calling sd_pid_get_unit: %v", syscall.Errno(-ret))
return
}

unit = C.GoString(u)
return
func CurrentUnitName() (string, error) {
return currentUnitName()
}

// IsRunningSystemd checks whether the host was booted with systemd as its init
Expand Down
174 changes: 174 additions & 0 deletions util/util_cgo.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,174 @@
// Copyright 2016 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// +build cgo

package util

// #include <stdlib.h>
// #include <sys/types.h>
// #include <unistd.h>
//
// int
// my_sd_pid_get_owner_uid(void *f, pid_t pid, uid_t *uid)
// {
// int (*sd_pid_get_owner_uid)(pid_t, uid_t *);
//
// sd_pid_get_owner_uid = (int (*)(pid_t, uid_t *))f;
// return sd_pid_get_owner_uid(pid, uid);
// }
//
// int
// my_sd_pid_get_unit(void *f, pid_t pid, char **unit)
// {
// int (*sd_pid_get_unit)(pid_t, char **);
//
// sd_pid_get_unit = (int (*)(pid_t, char **))f;
// return sd_pid_get_unit(pid, unit);
// }
//
// int
// my_sd_pid_get_slice(void *f, pid_t pid, char **slice)
// {
// int (*sd_pid_get_slice)(pid_t, char **);
//
// sd_pid_get_slice = (int (*)(pid_t, char **))f;
// return sd_pid_get_slice(pid, slice);
// }
//
// int
// am_session_leader()
// {
// return (getsid(0) == getpid());
// }
import "C"
import (
"fmt"
"syscall"
"unsafe"

"github.com/coreos/pkg/dlopen"
)

var libsystemdNames = []string{
// systemd < 209
"libsystemd-login.so.0",
"libsystemd-login.so",

// systemd >= 209 merged libsystemd-login into libsystemd proper
"libsystemd.so.0",
"libsystemd.so",
}

func getRunningSlice() (slice string, err error) {
var h *dlopen.LibHandle
h, err = dlopen.GetHandle(libsystemdNames)
if err != nil {
return
}
defer func() {
if err1 := h.Close(); err1 != nil {
err = err1
}
}()

sd_pid_get_slice, err := h.GetSymbolPointer("sd_pid_get_slice")
if err != nil {
return
}

var s string
sl := C.CString(s)
defer C.free(unsafe.Pointer(sl))

ret := C.my_sd_pid_get_slice(sd_pid_get_slice, 0, &sl)
if ret < 0 {
err = fmt.Errorf("error calling sd_pid_get_slice: %v", syscall.Errno(-ret))
return
}

return C.GoString(sl), nil
}

func runningFromSystemService() (ret bool, err error) {
var h *dlopen.LibHandle
h, err = dlopen.GetHandle(libsystemdNames)
if err != nil {
return
}
defer func() {
if err1 := h.Close(); err1 != nil {
err = err1
}
}()

sd_pid_get_owner_uid, err := h.GetSymbolPointer("sd_pid_get_owner_uid")
if err != nil {
return
}

var uid C.uid_t
errno := C.my_sd_pid_get_owner_uid(sd_pid_get_owner_uid, 0, &uid)
serrno := syscall.Errno(-errno)
// when we're running from a unit file, sd_pid_get_owner_uid returns
// ENOENT (systemd <220) or ENXIO (systemd >=220)
switch {
case errno >= 0:
ret = false
case serrno == syscall.ENOENT, serrno == syscall.ENXIO:
// Since the implementation of sessions in systemd relies on
// the `pam_systemd` module, using the sd_pid_get_owner_uid
// heuristic alone can result in false positives if that module
// (or PAM itself) is not present or properly configured on the
// system. As such, we also check if we're the session leader,
// which should be the case if we're invoked from a unit file,
// but not if e.g. we're invoked from the command line from a
// user's login session
ret = C.am_session_leader() == 1
default:
err = fmt.Errorf("error calling sd_pid_get_owner_uid: %v", syscall.Errno(-errno))
}
return
}

func currentUnitName() (unit string, err error) {
var h *dlopen.LibHandle
h, err = dlopen.GetHandle(libsystemdNames)
if err != nil {
return
}
defer func() {
if err1 := h.Close(); err1 != nil {
err = err1
}
}()

sd_pid_get_unit, err := h.GetSymbolPointer("sd_pid_get_unit")
if err != nil {
return
}

var s string
u := C.CString(s)
defer C.free(unsafe.Pointer(u))

ret := C.my_sd_pid_get_unit(sd_pid_get_unit, 0, &u)
if ret < 0 {
err = fmt.Errorf("error calling sd_pid_get_unit: %v", syscall.Errno(-ret))
return
}

unit = C.GoString(u)
return
}
27 changes: 27 additions & 0 deletions util/util_stub.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
// Copyright 2016 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// +build !cgo

package util

import (
"fmt"
)

func getRunningSlice() (string, error) { return "", ErrNoCGO }

func runningFromSystemService() (bool, error) { return false, ErrNoCGO }

func currentUnitName() (string, error) { return "", ErrNoCGO }