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util-linux/sys-utils/unshare.c

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/*
* unshare(1) - command-line interface for unshare(2)
*
* Copyright (C) 2009 Mikhail Gusarov <dottedmag@dottedmag.net>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2, or (at your option) any
* later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <errno.h>
#include <getopt.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/prctl.h>
#include <grp.h>
/* we only need some defines missing in sys/mount.h, no libmount linkage */
#include <libmount.h>
#include "nls.h"
#include "c.h"
#include "caputils.h"
#include "closestream.h"
#include "namespace.h"
#include "exec_shell.h"
#include "xalloc.h"
#include "pathnames.h"
#include "all-io.h"
#include "signames.h"
#include "strutils.h"
#include "pwdutils.h"
/* synchronize parent and child by pipe */
#define PIPE_SYNC_BYTE 0x06
/* 'private' is kernel default */
#define UNSHARE_PROPAGATION_DEFAULT (MS_REC | MS_PRIVATE)
/* /proc namespace files and mountpoints for binds */
static struct namespace_file {
int type; /* CLONE_NEW* */
const char *name; /* ns/<type> */
const char *target; /* user specified target for bind mount */
} namespace_files[] = {
{ .type = CLONE_NEWUSER, .name = "ns/user" },
{ .type = CLONE_NEWCGROUP,.name = "ns/cgroup" },
{ .type = CLONE_NEWIPC, .name = "ns/ipc" },
{ .type = CLONE_NEWUTS, .name = "ns/uts" },
{ .type = CLONE_NEWNET, .name = "ns/net" },
{ .type = CLONE_NEWPID, .name = "ns/pid_for_children" },
{ .type = CLONE_NEWNS, .name = "ns/mnt" },
{ .type = CLONE_NEWTIME, .name = "ns/time_for_children" },
{ .name = NULL }
};
static int npersists; /* number of persistent namespaces */
enum {
SETGROUPS_NONE = -1,
SETGROUPS_DENY = 0,
SETGROUPS_ALLOW = 1,
};
static const char *setgroups_strings[] =
{
[SETGROUPS_DENY] = "deny",
[SETGROUPS_ALLOW] = "allow"
};
static int setgroups_str2id(const char *str)
{
size_t i;
for (i = 0; i < ARRAY_SIZE(setgroups_strings); i++)
if (strcmp(str, setgroups_strings[i]) == 0)
return i;
errx(EXIT_FAILURE, _("unsupported --setgroups argument '%s'"), str);
}
static void setgroups_control(int action)
{
const char *file = _PATH_PROC_SETGROUPS;
const char *cmd;
int fd;
if (action < 0 || (size_t) action >= ARRAY_SIZE(setgroups_strings))
return;
cmd = setgroups_strings[action];
fd = open(file, O_WRONLY);
if (fd < 0) {
if (errno == ENOENT)
return;
err(EXIT_FAILURE, _("cannot open %s"), file);
}
if (write_all(fd, cmd, strlen(cmd)))
err(EXIT_FAILURE, _("write failed %s"), file);
close(fd);
}
static void map_id(const char *file, uint32_t from, uint32_t to)
{
char *buf;
int fd;
fd = open(file, O_WRONLY);
if (fd < 0)
err(EXIT_FAILURE, _("cannot open %s"), file);
xasprintf(&buf, "%u %u 1", from, to);
if (write_all(fd, buf, strlen(buf)))
err(EXIT_FAILURE, _("write failed %s"), file);
free(buf);
close(fd);
}
static unsigned long parse_propagation(const char *str)
{
size_t i;
static const struct prop_opts {
const char *name;
unsigned long flag;
} opts[] = {
{ "slave", MS_REC | MS_SLAVE },
{ "private", MS_REC | MS_PRIVATE },
{ "shared", MS_REC | MS_SHARED },
{ "unchanged", 0 }
};
for (i = 0; i < ARRAY_SIZE(opts); i++) {
if (strcmp(opts[i].name, str) == 0)
return opts[i].flag;
}
errx(EXIT_FAILURE, _("unsupported propagation mode: %s"), str);
}
static void set_propagation(unsigned long flags)
{
if (flags == 0)
return;
if (mount("none", "/", NULL, flags, NULL) != 0)
err(EXIT_FAILURE, _("cannot change root filesystem propagation"));
}
static int set_ns_target(int type, const char *path)
{
struct namespace_file *ns;
for (ns = namespace_files; ns->name; ns++) {
if (ns->type != type)
continue;
ns->target = path;
npersists++;
return 0;
}
return -EINVAL;
}
static int bind_ns_files(pid_t pid)
{
struct namespace_file *ns;
char src[PATH_MAX];
for (ns = namespace_files; ns->name; ns++) {
if (!ns->target)
continue;
snprintf(src, sizeof(src), "/proc/%u/%s", (unsigned) pid, ns->name);
if (mount(src, ns->target, NULL, MS_BIND, NULL) != 0)
err(EXIT_FAILURE, _("mount %s on %s failed"), src, ns->target);
}
return 0;
}
static ino_t get_mnt_ino(pid_t pid)
{
struct stat st;
char path[PATH_MAX];
snprintf(path, sizeof(path), "/proc/%u/ns/mnt", (unsigned) pid);
if (stat(path, &st) != 0)
err(EXIT_FAILURE, _("stat of %s failed"), path);
return st.st_ino;
}
static void settime(time_t offset, clockid_t clk_id)
{
char buf[sizeof(stringify_value(ULONG_MAX)) * 3];
int fd, len;
len = snprintf(buf, sizeof(buf), "%d %ld 0", clk_id, offset);
fd = open("/proc/self/timens_offsets", O_WRONLY);
if (fd < 0)
err(EXIT_FAILURE, _("failed to open /proc/self/timens_offsets"));
if (write(fd, buf, len) != len)
err(EXIT_FAILURE, _("failed to write to /proc/self/timens_offsets"));
close(fd);
}
static void bind_ns_files_from_child(pid_t *child, int fds[2])
{
char ch;
pid_t ppid = getpid();
ino_t ino = get_mnt_ino(ppid);
if (pipe(fds) < 0)
err(EXIT_FAILURE, _("pipe failed"));
*child = fork();
switch (*child) {
case -1:
err(EXIT_FAILURE, _("fork failed"));
case 0: /* child */
close(fds[1]);
fds[1] = -1;
/* wait for parent */
if (read_all(fds[0], &ch, 1) != 1 && ch != PIPE_SYNC_BYTE)
err(EXIT_FAILURE, _("failed to read pipe"));
if (get_mnt_ino(ppid) == ino)
exit(EXIT_FAILURE);
bind_ns_files(ppid);
exit(EXIT_SUCCESS);
break;
default: /* parent */
close(fds[0]);
fds[0] = -1;
break;
}
}
static uid_t get_user(const char *s, const char *err)
{
struct passwd *pw;
char *buf = NULL;
uid_t ret;
pw = xgetpwnam(s, &buf);
if (pw) {
ret = pw->pw_uid;
free(pw);
free(buf);
} else {
ret = strtoul_or_err(s, err);
}
return ret;
}
static gid_t get_group(const char *s, const char *err)
{
struct group *gr;
char *buf = NULL;
gid_t ret;
gr = xgetgrnam(s, &buf);
if (gr) {
ret = gr->gr_gid;
free(gr);
free(buf);
} else {
ret = strtoul_or_err(s, err);
}
return ret;
}
static void __attribute__((__noreturn__)) usage(void)
{
FILE *out = stdout;
fputs(USAGE_HEADER, out);
fprintf(out, _(" %s [options] [<program> [<argument>...]]\n"),
program_invocation_short_name);
fputs(USAGE_SEPARATOR, out);
fputs(_("Run a program with some namespaces unshared from the parent.\n"), out);
fputs(USAGE_OPTIONS, out);
fputs(_(" -m, --mount[=<file>] unshare mounts namespace\n"), out);
fputs(_(" -u, --uts[=<file>] unshare UTS namespace (hostname etc)\n"), out);
fputs(_(" -i, --ipc[=<file>] unshare System V IPC namespace\n"), out);
fputs(_(" -n, --net[=<file>] unshare network namespace\n"), out);
fputs(_(" -p, --pid[=<file>] unshare pid namespace\n"), out);
fputs(_(" -U, --user[=<file>] unshare user namespace\n"), out);
fputs(_(" -C, --cgroup[=<file>] unshare cgroup namespace\n"), out);
fputs(_(" -T, --time[=<file>] unshare time namespace\n"), out);
fputs(USAGE_SEPARATOR, out);
fputs(_(" -f, --fork fork before launching <program>\n"), out);
fputs(_(" --map-user=<uid>|<name> map current user to uid (implies --user)\n"), out);
fputs(_(" --map-group=<gid>|<name> map current group to gid (implies --user)\n"), out);
fputs(_(" -r, --map-root-user map current user to root (implies --user)\n"), out);
fputs(_(" -c, --map-current-user map current user to itself (implies --user)\n"), out);
fputs(USAGE_SEPARATOR, out);
fputs(_(" --kill-child[=<signame>] when dying, kill the forked child (implies --fork)\n"
" defaults to SIGKILL\n"), out);
fputs(_(" --mount-proc[=<dir>] mount proc filesystem first (implies --mount)\n"), out);
fputs(_(" --propagation slave|shared|private|unchanged\n"
" modify mount propagation in mount namespace\n"), out);
fputs(_(" --setgroups allow|deny control the setgroups syscall in user namespaces\n"), out);
fputs(_(" --keep-caps retain capabilities granted in user namespaces\n"), out);
fputs(USAGE_SEPARATOR, out);
fputs(_(" -R, --root=<dir> run the command with root directory set to <dir>\n"), out);
fputs(_(" -w, --wd=<dir> change working directory to <dir>\n"), out);
fputs(_(" -S, --setuid <uid> set uid in entered namespace\n"), out);
fputs(_(" -G, --setgid <gid> set gid in entered namespace\n"), out);
fputs(_(" --monotonic <offset> set clock monotonic offset (seconds) in time namespaces\n"), out);
fputs(_(" --boottime <offset> set clock boottime offset (seconds) in time namespaces\n"), out);
fputs(USAGE_SEPARATOR, out);
printf(USAGE_HELP_OPTIONS(27));
printf(USAGE_MAN_TAIL("unshare(1)"));
exit(EXIT_SUCCESS);
}
int main(int argc, char *argv[])
{
enum {
OPT_MOUNTPROC = CHAR_MAX + 1,
OPT_PROPAGATION,
OPT_SETGROUPS,
OPT_KILLCHILD,
OPT_KEEPCAPS,
OPT_MONOTONIC,
OPT_BOOTTIME,
OPT_MAPUSER,
OPT_MAPGROUP,
};
static const struct option longopts[] = {
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, 'V' },
{ "mount", optional_argument, NULL, 'm' },
{ "uts", optional_argument, NULL, 'u' },
{ "ipc", optional_argument, NULL, 'i' },
{ "net", optional_argument, NULL, 'n' },
{ "pid", optional_argument, NULL, 'p' },
{ "user", optional_argument, NULL, 'U' },
{ "cgroup", optional_argument, NULL, 'C' },
{ "time", optional_argument, NULL, 'T' },
{ "fork", no_argument, NULL, 'f' },
{ "kill-child", optional_argument, NULL, OPT_KILLCHILD },
{ "mount-proc", optional_argument, NULL, OPT_MOUNTPROC },
{ "map-user", required_argument, NULL, OPT_MAPUSER },
{ "map-group", required_argument, NULL, OPT_MAPGROUP },
{ "map-root-user", no_argument, NULL, 'r' },
{ "map-current-user", no_argument, NULL, 'c' },
{ "propagation", required_argument, NULL, OPT_PROPAGATION },
{ "setgroups", required_argument, NULL, OPT_SETGROUPS },
{ "keep-caps", no_argument, NULL, OPT_KEEPCAPS },
{ "setuid", required_argument, NULL, 'S' },
{ "setgid", required_argument, NULL, 'G' },
{ "root", required_argument, NULL, 'R' },
{ "wd", required_argument, NULL, 'w' },
{ "monotonic", required_argument, NULL, OPT_MONOTONIC },
{ "boottime", required_argument, NULL, OPT_BOOTTIME },
{ NULL, 0, NULL, 0 }
};
int setgrpcmd = SETGROUPS_NONE;
int unshare_flags = 0;
int c, forkit = 0;
uid_t mapuser = -1;
gid_t mapgroup = -1;
int kill_child_signo = 0; /* 0 means --kill-child was not used */
const char *procmnt = NULL;
const char *newroot = NULL;
const char *newdir = NULL;
pid_t pid_bind = 0;
pid_t pid = 0;
int fds[2];
int status;
unsigned long propagation = UNSHARE_PROPAGATION_DEFAULT;
int force_uid = 0, force_gid = 0;
uid_t uid = 0, real_euid = geteuid();
gid_t gid = 0, real_egid = getegid();
int keepcaps = 0;
time_t monotonic = 0;
time_t boottime = 0;
int force_monotonic = 0;
int force_boottime = 0;
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
close_stdout_atexit();
while ((c = getopt_long(argc, argv, "+fhVmuinpCTUrR:w:S:G:c", longopts, NULL)) != -1) {
switch (c) {
case 'f':
forkit = 1;
break;
case 'm':
unshare_flags |= CLONE_NEWNS;
if (optarg)
set_ns_target(CLONE_NEWNS, optarg);
break;
case 'u':
unshare_flags |= CLONE_NEWUTS;
if (optarg)
set_ns_target(CLONE_NEWUTS, optarg);
break;
case 'i':
unshare_flags |= CLONE_NEWIPC;
if (optarg)
set_ns_target(CLONE_NEWIPC, optarg);
break;
case 'n':
unshare_flags |= CLONE_NEWNET;
if (optarg)
set_ns_target(CLONE_NEWNET, optarg);
break;
case 'p':
unshare_flags |= CLONE_NEWPID;
if (optarg)
set_ns_target(CLONE_NEWPID, optarg);
break;
case 'U':
unshare_flags |= CLONE_NEWUSER;
if (optarg)
set_ns_target(CLONE_NEWUSER, optarg);
break;
case 'C':
unshare_flags |= CLONE_NEWCGROUP;
if (optarg)
set_ns_target(CLONE_NEWCGROUP, optarg);
break;
case 'T':
unshare_flags |= CLONE_NEWTIME;
if (optarg)
set_ns_target(CLONE_NEWTIME, optarg);
break;
case OPT_MOUNTPROC:
unshare_flags |= CLONE_NEWNS;
procmnt = optarg ? optarg : "/proc";
break;
case OPT_MAPUSER:
unshare_flags |= CLONE_NEWUSER;
mapuser = get_user(optarg, _("failed to parse uid"));
break;
case OPT_MAPGROUP:
unshare_flags |= CLONE_NEWUSER;
mapgroup = get_group(optarg, _("failed to parse gid"));
break;
case 'r':
unshare_flags |= CLONE_NEWUSER;
mapuser = 0;
mapgroup = 0;
break;
case 'c':
unshare_flags |= CLONE_NEWUSER;
mapuser = real_euid;
mapgroup = real_egid;
break;
case OPT_SETGROUPS:
setgrpcmd = setgroups_str2id(optarg);
break;
case OPT_PROPAGATION:
propagation = parse_propagation(optarg);
break;
case OPT_KILLCHILD:
forkit = 1;
if (optarg) {
if ((kill_child_signo = signame_to_signum(optarg)) < 0)
errx(EXIT_FAILURE, _("unknown signal: %s"),
optarg);
} else {
kill_child_signo = SIGKILL;
}
break;
case OPT_KEEPCAPS:
keepcaps = 1;
cap_last_cap(); /* Force last cap to be cached before we fork. */
break;
case 'S':
uid = strtoul_or_err(optarg, _("failed to parse uid"));
force_uid = 1;
break;
case 'G':
gid = strtoul_or_err(optarg, _("failed to parse gid"));
force_gid = 1;
break;
case 'R':
newroot = optarg;
break;
case 'w':
newdir = optarg;
break;
case OPT_MONOTONIC:
monotonic = strtoul_or_err(optarg, _("failed to parse monotonic offset"));
force_monotonic = 1;
break;
case OPT_BOOTTIME:
boottime = strtoul_or_err(optarg, _("failed to parse boottime offset"));
force_boottime = 1;
break;
case 'h':
usage();
case 'V':
print_version(EXIT_SUCCESS);
default:
errtryhelp(EXIT_FAILURE);
}
}
if ((force_monotonic || force_boottime) && !(unshare_flags & CLONE_NEWTIME))
errx(EXIT_FAILURE, _("options --monotonic and --boottime require "
"unsharing of a time namespace (-t)"));
if (npersists && (unshare_flags & CLONE_NEWNS))
bind_ns_files_from_child(&pid_bind, fds);
if (-1 == unshare(unshare_flags))
err(EXIT_FAILURE, _("unshare failed"));
if (force_boottime)
settime(boottime, CLOCK_BOOTTIME);
if (force_monotonic)
settime(monotonic, CLOCK_MONOTONIC);
if (forkit) {
signal(SIGINT, SIG_IGN);
signal(SIGTERM, SIG_IGN);
/* force child forking before mountspace binding
* so pid_for_children is populated */
pid = fork();
switch(pid) {
case -1:
err(EXIT_FAILURE, _("fork failed"));
case 0: /* child */
if (pid_bind && (unshare_flags & CLONE_NEWNS))
close(fds[1]);
break;
default: /* parent */
break;
}
}
if (npersists && (pid || !forkit)) {
/* run in parent */
if (pid_bind && (unshare_flags & CLONE_NEWNS)) {
int rc;
char ch = PIPE_SYNC_BYTE;
/* signal child we are ready */
write_all(fds[1], &ch, 1);
close(fds[1]);
fds[1] = -1;
/* wait for bind_ns_files_from_child() */
do {
rc = waitpid(pid_bind, &status, 0);
if (rc < 0) {
if (errno == EINTR)
continue;
err(EXIT_FAILURE, _("waitpid failed"));
}
if (WIFEXITED(status) &&
WEXITSTATUS(status) != EXIT_SUCCESS)
return WEXITSTATUS(status);
} while (rc < 0);
} else
/* simple way, just bind */
bind_ns_files(getpid());
}
if (pid) {
if (waitpid(pid, &status, 0) == -1)
err(EXIT_FAILURE, _("waitpid failed"));
signal(SIGINT, SIG_DFL);
signal(SIGTERM, SIG_DFL);
if (WIFEXITED(status))
return WEXITSTATUS(status);
if (WIFSIGNALED(status))
kill(getpid(), WTERMSIG(status));
err(EXIT_FAILURE, _("child exit failed"));
}
if (kill_child_signo != 0 && prctl(PR_SET_PDEATHSIG, kill_child_signo) < 0)
err(EXIT_FAILURE, "prctl failed");
if (mapuser != (uid_t) -1)
map_id(_PATH_PROC_UIDMAP, mapuser, real_euid);
/* Since Linux 3.19 unprivileged writing of /proc/self/gid_map
* has been disabled unless /proc/self/setgroups is written
* first to permanently disable the ability to call setgroups
* in that user namespace. */
if (mapgroup != (gid_t) -1) {
if (setgrpcmd == SETGROUPS_ALLOW)
errx(EXIT_FAILURE, _("options --setgroups=allow and "
"--map-group are mutually exclusive"));
setgroups_control(SETGROUPS_DENY);
map_id(_PATH_PROC_GIDMAP, mapgroup, real_egid);
}
if (setgrpcmd != SETGROUPS_NONE)
setgroups_control(setgrpcmd);
if ((unshare_flags & CLONE_NEWNS) && propagation)
set_propagation(propagation);
if (newroot) {
if (chroot(newroot) != 0)
err(EXIT_FAILURE,
_("cannot change root directory to '%s'"), newroot);
newdir = newdir ?: "/";
}
if (newdir && chdir(newdir))
err(EXIT_FAILURE, _("cannot chdir to '%s'"), newdir);
if (procmnt) {
/* When not changing root and using the default propagation flags
then the recursive propagation change of root will
automatically change that of an existing proc mount. */
if (!newroot && propagation != (MS_PRIVATE|MS_REC)) {
int rc = mount("none", procmnt, NULL, MS_PRIVATE|MS_REC, NULL);
/* Custom procmnt means that proc is very likely not mounted, causing EINVAL.
Ignoring the error in this specific instance is considered safe. */
if(rc != 0 && errno != EINVAL)
err(EXIT_FAILURE, _("cannot change %s filesystem propagation"), procmnt);
}
if (mount("proc", procmnt, "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) != 0)
err(EXIT_FAILURE, _("mount %s failed"), procmnt);
}
if (force_gid) {
if (setgroups(0, NULL) != 0) /* drop supplementary groups */
err(EXIT_FAILURE, _("setgroups failed"));
if (setgid(gid) < 0) /* change GID */
err(EXIT_FAILURE, _("setgid failed"));
}
if (force_uid && setuid(uid) < 0) /* change UID */
err(EXIT_FAILURE, _("setuid failed"));
/* We use capabilities system calls to propagate the permitted
* capabilities into the ambient set because we have already
* forked so are in async-signal-safe context. */
if (keepcaps && (unshare_flags & CLONE_NEWUSER)) {
struct __user_cap_header_struct header = {
.version = _LINUX_CAPABILITY_VERSION_3,
.pid = 0,
};
struct __user_cap_data_struct payload[_LINUX_CAPABILITY_U32S_3] = {{ 0 }};
uint64_t effective, cap;
if (capget(&header, payload) < 0)
err(EXIT_FAILURE, _("capget failed"));
/* In order the make capabilities ambient, we first need to ensure
* that they are all inheritable. */
payload[0].inheritable = payload[0].permitted;
payload[1].inheritable = payload[1].permitted;
if (capset(&header, payload) < 0)
err(EXIT_FAILURE, _("capset failed"));
effective = ((uint64_t)payload[1].effective << 32) | (uint64_t)payload[0].effective;
for (cap = 0; cap < (sizeof(effective) * 8); cap++) {
/* This is the same check as cap_valid(), but using
* the runtime value for the last valid cap. */
if (cap > (uint64_t) cap_last_cap())
continue;
if ((effective & (1 << cap))
&& prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0) < 0)
err(EXIT_FAILURE, _("prctl(PR_CAP_AMBIENT) failed"));
}
}
if (optind < argc) {
execvp(argv[optind], argv + optind);
errexec(argv[optind]);
}
exec_shell();
}
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