/usr/share/gocode/src/github.com/lxc/lxd/shared/util_linux.go is in golang-github-lxc-lxd-dev 2.0.2-0ubuntu1~16.04.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// +build cgo
package shared
import (
"errors"
"fmt"
"os"
"os/exec"
"syscall"
"unsafe"
)
// #cgo LDFLAGS: -lutil -lpthread
/*
#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <grp.h>
#include <pty.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <string.h>
#include <stdio.h>
#ifndef AT_SYMLINK_FOLLOW
#define AT_SYMLINK_FOLLOW 0x400
#endif
#ifndef AT_EMPTY_PATH
#define AT_EMPTY_PATH 0x1000
#endif
// This is an adaption from https://codereview.appspot.com/4589049, to be
// included in the stdlib with the stdlib's license.
static int mygetgrgid_r(int gid, struct group *grp,
char *buf, size_t buflen, struct group **result) {
return getgrgid_r(gid, grp, buf, buflen, result);
}
void configure_pty(int fd) {
struct termios term_settings;
struct winsize win;
if (tcgetattr(fd, &term_settings) < 0) {
fprintf(stderr, "Failed to get settings: %s\n", strerror(errno));
return;
}
term_settings.c_iflag |= IMAXBEL;
term_settings.c_iflag |= IUTF8;
term_settings.c_iflag |= BRKINT;
term_settings.c_iflag |= IXANY;
term_settings.c_cflag |= HUPCL;
if (tcsetattr(fd, TCSANOW, &term_settings) < 0) {
fprintf(stderr, "Failed to set settings: %s\n", strerror(errno));
return;
}
if (ioctl(fd, TIOCGWINSZ, &win) < 0) {
fprintf(stderr, "Failed to get the terminal size: %s\n", strerror(errno));
return;
}
win.ws_col = 80;
win.ws_row = 25;
if (ioctl(fd, TIOCSWINSZ, &win) < 0) {
fprintf(stderr, "Failed to set the terminal size: %s\n", strerror(errno));
return;
}
if (fcntl(fd, F_SETFD, FD_CLOEXEC) < 0) {
fprintf(stderr, "Failed to set FD_CLOEXEC: %s\n", strerror(errno));
return;
}
return;
}
void create_pty(int *master, int *slave, int uid, int gid) {
if (openpty(master, slave, NULL, NULL, NULL) < 0) {
fprintf(stderr, "Failed to openpty: %s\n", strerror(errno));
return;
}
configure_pty(*master);
configure_pty(*slave);
if (fchown(*slave, uid, gid) < 0) {
fprintf(stderr, "Warning: error chowning pty to container root\n");
fprintf(stderr, "Continuing...\n");
}
if (fchown(*master, uid, gid) < 0) {
fprintf(stderr, "Warning: error chowning pty to container root\n");
fprintf(stderr, "Continuing...\n");
}
}
void create_pipe(int *master, int *slave) {
int pipefd[2];
if (pipe2(pipefd, O_CLOEXEC) < 0) {
fprintf(stderr, "Failed to create a pipe: %s\n", strerror(errno));
return;
}
*master = pipefd[0];
*slave = pipefd[1];
}
int shiftowner(char *basepath, char *path, int uid, int gid) {
struct stat sb;
int fd, r;
char fdpath[PATH_MAX];
char realpath[PATH_MAX];
fd = open(path, O_PATH|O_NOFOLLOW);
if (fd < 0 ) {
perror("Failed open");
return 1;
}
r = sprintf(fdpath, "/proc/self/fd/%d", fd);
if (r < 0) {
perror("Failed sprintf");
close(fd);
return 1;
}
r = readlink(fdpath, realpath, PATH_MAX);
if (r < 0) {
perror("Failed readlink");
close(fd);
return 1;
}
if (strlen(realpath) < strlen(basepath)) {
printf("Invalid path, source (%s) is outside of basepath (%s).\n", realpath, basepath);
close(fd);
return 1;
}
if (strncmp(realpath, basepath, strlen(basepath))) {
printf("Invalid path, source (%s) is outside of basepath (%s).\n", realpath, basepath);
close(fd);
return 1;
}
r = fstat(fd, &sb);
if (r < 0) {
perror("Failed fstat");
close(fd);
return 1;
}
r = fchownat(fd, "", uid, gid, AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);
if (r < 0) {
perror("Failed chown");
close(fd);
return 1;
}
if (!S_ISLNK(sb.st_mode)) {
r = chmod(fdpath, sb.st_mode);
if (r < 0) {
perror("Failed chmod");
close(fd);
return 1;
}
}
close(fd);
return 0;
}
*/
import "C"
func ShiftOwner(basepath string, path string, uid int, gid int) error {
cbasepath := C.CString(basepath)
defer C.free(unsafe.Pointer(cbasepath))
cpath := C.CString(path)
defer C.free(unsafe.Pointer(cpath))
r := C.shiftowner(cbasepath, cpath, C.int(uid), C.int(gid))
if r != 0 {
return fmt.Errorf("Failed to change ownership of: %s", path)
}
return nil
}
func OpenPty(uid, gid int) (master *os.File, slave *os.File, err error) {
fd_master := C.int(-1)
fd_slave := C.int(-1)
rootUid := C.int(uid)
rootGid := C.int(gid)
C.create_pty(&fd_master, &fd_slave, rootUid, rootGid)
if fd_master == -1 || fd_slave == -1 {
return nil, nil, errors.New("Failed to create a new pts pair")
}
master = os.NewFile(uintptr(fd_master), "master")
slave = os.NewFile(uintptr(fd_slave), "slave")
return master, slave, nil
}
func Pipe() (master *os.File, slave *os.File, err error) {
fd_master := C.int(-1)
fd_slave := C.int(-1)
C.create_pipe(&fd_master, &fd_slave)
if fd_master == -1 || fd_slave == -1 {
return nil, nil, errors.New("Failed to create a new pipe")
}
master = os.NewFile(uintptr(fd_master), "master")
slave = os.NewFile(uintptr(fd_slave), "slave")
return master, slave, nil
}
// GroupName is an adaption from https://codereview.appspot.com/4589049.
func GroupName(gid int) (string, error) {
var grp C.struct_group
var result *C.struct_group
bufSize := C.size_t(C.sysconf(C._SC_GETGR_R_SIZE_MAX))
buf := C.malloc(bufSize)
if buf == nil {
return "", fmt.Errorf("allocation failed")
}
defer C.free(buf)
// mygetgrgid_r is a wrapper around getgrgid_r to
// to avoid using gid_t because C.gid_t(gid) for
// unknown reasons doesn't work on linux.
rv := C.mygetgrgid_r(C.int(gid),
&grp,
(*C.char)(buf),
bufSize,
&result)
if rv != 0 {
return "", fmt.Errorf("failed group lookup: %s", syscall.Errno(rv))
}
if result == nil {
return "", fmt.Errorf("unknown group %d", gid)
}
return C.GoString(result.gr_name), nil
}
// GroupId is an adaption from https://codereview.appspot.com/4589049.
func GroupId(name string) (int, error) {
var grp C.struct_group
var result *C.struct_group
bufSize := C.size_t(C.sysconf(C._SC_GETGR_R_SIZE_MAX))
buf := C.malloc(bufSize)
if buf == nil {
return -1, fmt.Errorf("allocation failed")
}
defer C.free(buf)
// mygetgrgid_r is a wrapper around getgrgid_r to
// to avoid using gid_t because C.gid_t(gid) for
// unknown reasons doesn't work on linux.
cname := C.CString(name)
defer C.free(unsafe.Pointer(cname))
rv := C.getgrnam_r(cname,
&grp,
(*C.char)(buf),
bufSize,
&result)
if rv != 0 {
return -1, fmt.Errorf("failed group lookup: %s", syscall.Errno(rv))
}
if result == nil {
return -1, fmt.Errorf("unknown group %s", name)
}
return int(C.int(result.gr_gid)), nil
}
// --- pure Go functions ---
func GetFileStat(p string) (uid int, gid int, major int, minor int,
inode uint64, nlink int, err error) {
var stat syscall.Stat_t
err = syscall.Lstat(p, &stat)
if err != nil {
return
}
uid = int(stat.Uid)
gid = int(stat.Gid)
inode = uint64(stat.Ino)
nlink = int(stat.Nlink)
major = -1
minor = -1
if stat.Mode&syscall.S_IFBLK != 0 || stat.Mode&syscall.S_IFCHR != 0 {
major = int(stat.Rdev / 256)
minor = int(stat.Rdev % 256)
}
return
}
func IsMountPoint(name string) bool {
_, err := exec.LookPath("mountpoint")
if err == nil {
err = exec.Command("mountpoint", "-q", name).Run()
if err != nil {
return false
}
return true
}
stat, err := os.Stat(name)
if err != nil {
return false
}
rootStat, err := os.Lstat(name + "/..")
if err != nil {
return false
}
// If the directory has the same device as parent, then it's not a mountpoint.
return stat.Sys().(*syscall.Stat_t).Dev != rootStat.Sys().(*syscall.Stat_t).Dev
}
func ReadLastNLines(f *os.File, lines int) (string, error) {
if lines <= 0 {
return "", fmt.Errorf("invalid line count")
}
stat, err := f.Stat()
if err != nil {
return "", err
}
data, err := syscall.Mmap(int(f.Fd()), 0, int(stat.Size()), syscall.PROT_READ, syscall.MAP_SHARED)
if err != nil {
return "", err
}
defer syscall.Munmap(data)
for i := len(data) - 1; i >= 0; i-- {
if data[i] == '\n' {
lines--
}
if lines < 0 {
return string(data[i+1 : len(data)]), nil
}
}
return string(data), nil
}
func SetSize(fd int, width int, height int) (err error) {
var dimensions [4]uint16
dimensions[0] = uint16(height)
dimensions[1] = uint16(width)
if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall.TIOCSWINSZ), uintptr(unsafe.Pointer(&dimensions)), 0, 0, 0); err != 0 {
return err
}
return nil
}
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