/*
* nsenter(1) - command-line interface for setns(2)
*
* Copyright (C) 2012-2013 Eric Biederman <ebiederm@xmission.com>
*
* 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; version 2.
*
* 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 <dirent.h>
#include <errno.h>
#include <getopt.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <unistd.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <grp.h>
#include <sys/stat.h>
#ifdef HAVE_LIBSELINUX
# include <selinux/selinux.h>
#endif
#include "strutils.h"
#include "nls.h"
#include "c.h"
#include "closestream.h"
#include "namespace.h"
#include "exec_shell.h"
static struct namespace_file {
int nstype;
const char *name;
int fd;
} namespace_files[] = {
/* Careful the order is significant in this array.
*
* The user namespace comes either first or last: first if
* you're using it to increase your privilege and last if
* you're using it to decrease. We enter the namespaces in
* two passes starting initially from offset 1 and then offset
* 0 if that fails.
*/
{ .nstype = CLONE_NEWUSER, .name = "ns/user", .fd = -1 },
{ .nstype = CLONE_NEWCGROUP,.name = "ns/cgroup", .fd = -1 },
{ .nstype = CLONE_NEWIPC, .name = "ns/ipc", .fd = -1 },
{ .nstype = CLONE_NEWUTS, .name = "ns/uts", .fd = -1 },
{ .nstype = CLONE_NEWNET, .name = "ns/net", .fd = -1 },
{ .nstype = CLONE_NEWPID, .name = "ns/pid", .fd = -1 },
{ .nstype = CLONE_NEWNS, .name = "ns/mnt", .fd = -1 },
{ .nstype = 0, .name = NULL, .fd = -1 }
};
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 namespaces of other processes.\n"), out);
fputs(USAGE_OPTIONS, out);
fputs(_(" -a, --all enter all namespaces\n"), out);
fputs(_(" -t, --target <pid> target process to get namespaces from\n"), out);
fputs(_(" -m, --mount[=<file>] enter mount namespace\n"), out);
fputs(_(" -u, --uts[=<file>] enter UTS namespace (hostname etc)\n"), out);
fputs(_(" -i, --ipc[=<file>] enter System V IPC namespace\n"), out);
fputs(_(" -n, --net[=<file>] enter network namespace\n"), out);
fputs(_(" -p, --pid[=<file>] enter pid namespace\n"), out);
fputs(_(" -C, --cgroup[=<file>] enter cgroup namespace\n"), out);
fputs(_(" -U, --user[=<file>] enter user namespace\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(_(" --preserve-credentials do not touch uids or gids\n"), out);
fputs(_(" -r, --root[=<dir>] set the root directory\n"), out);
fputs(_(" -w, --wd[=<dir>] set the working directory\n"), out);
fputs(_(" -F, --no-fork do not fork before exec'ing <program>\n"), out);
#ifdef HAVE_LIBSELINUX
fputs(_(" -Z, --follow-context set SELinux context according to --target PID\n"), out);
#endif
fputs(USAGE_SEPARATOR, out);
printf(USAGE_HELP_OPTIONS(24));
printf(USAGE_MAN_TAIL("nsenter(1)"));
exit(EXIT_SUCCESS);
}
static pid_t namespace_target_pid = 0;
static int root_fd = -1;
static int wd_fd = -1;
static void open_target_fd(int *fd, const char *type, const char *path)
{
char pathbuf[PATH_MAX];
if (!path && namespace_target_pid) {
snprintf(pathbuf, sizeof(pathbuf), "/proc/%u/%s",
namespace_target_pid, type);
path = pathbuf;
}
if (!path)
errx(EXIT_FAILURE,
_("neither filename nor target pid supplied for %s"),
type);
if (*fd >= 0)
close(*fd);
*fd = open(path, O_RDONLY);
if (*fd < 0)
err(EXIT_FAILURE, _("cannot open %s"), path);
}
static void open_namespace_fd(int nstype, const char *path)
{
struct namespace_file *nsfile;
for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
if (nstype != nsfile->nstype)
continue;
open_target_fd(&nsfile->fd, nsfile->name, path);
return;
}
/* This should never happen */
assert(nsfile->nstype);
}
static int get_ns_ino(const char *path, ino_t *ino)
{
struct stat st;
if (stat(path, &st) != 0)
return -errno;
*ino = st.st_ino;
return 0;
}
static int is_same_namespace(pid_t a, pid_t b, const char *type)
{
char path[PATH_MAX];
ino_t a_ino = 0, b_ino = 0;
snprintf(path, sizeof(path), "/proc/%u/%s", a, type);
if (get_ns_ino(path, &a_ino) != 0)
err(EXIT_FAILURE, _("stat of %s failed"), path);
snprintf(path, sizeof(path), "/proc/%u/%s", b, type);
if (get_ns_ino(path, &b_ino) != 0)
err(EXIT_FAILURE, _("stat of %s failed"), path);
return a_ino == b_ino;
}
static void continue_as_child(void)
{
pid_t child = fork();
int status;
pid_t ret;
if (child < 0)
err(EXIT_FAILURE, _("fork failed"));
/* Only the child returns */
if (child == 0)
return;
for (;;) {
ret = waitpid(child, &status, WUNTRACED);
if ((ret == child) && (WIFSTOPPED(status))) {
/* The child suspended so suspend us as well */
kill(getpid(), SIGSTOP);
kill(child, SIGCONT);
} else {
break;
}
}
/* Return the child's exit code if possible */
if (WIFEXITED(status)) {
exit(WEXITSTATUS(status));
} else if (WIFSIGNALED(status)) {
kill(getpid(), WTERMSIG(status));
}
exit(EXIT_FAILURE);
}
int main(int argc, char *argv[])
{
enum {
OPT_PRESERVE_CRED = CHAR_MAX + 1
};
static const struct option longopts[] = {
{ "all", no_argument, NULL, 'a' },
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, 'V'},
{ "target", required_argument, NULL, 't' },
{ "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' },
{ "setuid", required_argument, NULL, 'S' },
{ "setgid", required_argument, NULL, 'G' },
{ "root", optional_argument, NULL, 'r' },
{ "wd", optional_argument, NULL, 'w' },
{ "no-fork", no_argument, NULL, 'F' },
{ "preserve-credentials", no_argument, NULL, OPT_PRESERVE_CRED },
#ifdef HAVE_LIBSELINUX
{ "follow-context", no_argument, NULL, 'Z' },
#endif
{ NULL, 0, NULL, 0 }
};
struct namespace_file *nsfile;
int c, pass, namespaces = 0, setgroups_nerrs = 0, preserve_cred = 0;
bool do_rd = false, do_wd = false, force_uid = false, force_gid = false;
bool do_all = false;
int do_fork = -1; /* unknown yet */
uid_t uid = 0;
gid_t gid = 0;
#ifdef HAVE_LIBSELINUX
bool selinux = 0;
#endif
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
close_stdout_atexit();
while ((c =
getopt_long(argc, argv, "+ahVt:m::u::i::n::p::C::U::S:G:r::w::FZ",
longopts, NULL)) != -1) {
switch (c) {
case 'a':
do_all = true;
break;
case 't':
namespace_target_pid =
strtoul_or_err(optarg, _("failed to parse pid"));
break;
case 'm':
if (optarg)
open_namespace_fd(CLONE_NEWNS, optarg);
else
namespaces |= CLONE_NEWNS;
break;
case 'u':
if (optarg)
open_namespace_fd(CLONE_NEWUTS, optarg);
else
namespaces |= CLONE_NEWUTS;
break;
case 'i':
if (optarg)
open_namespace_fd(CLONE_NEWIPC, optarg);
else
namespaces |= CLONE_NEWIPC;
break;
case 'n':
if (optarg)
open_namespace_fd(CLONE_NEWNET, optarg);
else
namespaces |= CLONE_NEWNET;
break;
case 'p':
if (optarg)
open_namespace_fd(CLONE_NEWPID, optarg);
else
namespaces |= CLONE_NEWPID;
break;
case 'C':
if (optarg)
open_namespace_fd(CLONE_NEWCGROUP, optarg);
else
namespaces |= CLONE_NEWCGROUP;
break;
case 'U':
if (optarg)
open_namespace_fd(CLONE_NEWUSER, optarg);
else
namespaces |= CLONE_NEWUSER;
break;
case 'S':
uid = strtoul_or_err(optarg, _("failed to parse uid"));
force_uid = true;
break;
case 'G':
gid = strtoul_or_err(optarg, _("failed to parse gid"));
force_gid = true;
break;
case 'F':
do_fork = 0;
break;
case 'r':
if (optarg)
open_target_fd(&root_fd, "root", optarg);
else
do_rd = true;
break;
case 'w':
if (optarg)
open_target_fd(&wd_fd, "cwd", optarg);
else
do_wd = true;
break;
case OPT_PRESERVE_CRED:
preserve_cred = 1;
break;
#ifdef HAVE_LIBSELINUX
case 'Z':
selinux = 1;
break;
#endif
case 'h':
usage();
case 'V':
print_version(EXIT_SUCCESS);
default:
errtryhelp(EXIT_FAILURE);
}
}
#ifdef HAVE_LIBSELINUX
if (selinux && is_selinux_enabled() > 0) {
char *scon = NULL;
if (!namespace_target_pid)
errx(EXIT_FAILURE, _("no target PID specified for --follow-context"));
if (getpidcon(namespace_target_pid, &scon) < 0)
errx(EXIT_FAILURE, _("failed to get %d SELinux context"),
(int) namespace_target_pid);
if (setexeccon(scon) < 0)
errx(EXIT_FAILURE, _("failed to set exec context to '%s'"), scon);
freecon(scon);
}
#endif
if (do_all) {
if (!namespace_target_pid)
errx(EXIT_FAILURE, _("no target PID specified for --all"));
for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
if (nsfile->fd >= 0)
continue; /* namespace already specified */
/* It is not permitted to use setns(2) to reenter the caller's
* current user namespace; see setns(2) man page for more details.
*/
if (nsfile->nstype & CLONE_NEWUSER
&& is_same_namespace(getpid(), namespace_target_pid, nsfile->name))
continue;
namespaces |= nsfile->nstype;
}
}
/*
* Open remaining namespace and directory descriptors.
*/
for (nsfile = namespace_files; nsfile->nstype; nsfile++)
if (nsfile->nstype & namespaces)
open_namespace_fd(nsfile->nstype, NULL);
if (do_rd)
open_target_fd(&root_fd, "root", NULL);
if (do_wd)
open_target_fd(&wd_fd, "cwd", NULL);
/*
* Update namespaces variable to contain all requested namespaces
*/
for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
if (nsfile->fd < 0)
continue;
namespaces |= nsfile->nstype;
}
/* for user namespaces we always set UID and GID (default is 0)
* and clear root's groups if --preserve-credentials is no specified */
if ((namespaces & CLONE_NEWUSER) && !preserve_cred) {
force_uid = true, force_gid = true;
/* We call setgroups() before and after we enter user namespace,
* let's complain only if both fail */
if (setgroups(0, NULL) != 0)
setgroups_nerrs++;
}
/*
* Now that we know which namespaces we want to enter, enter
* them. Do this in two passes, not entering the user
* namespace on the first pass. So if we're deprivileging the
* container we'll enter the user namespace last and if we're
* privileging it then we enter the user namespace first
* (because the initial setns will fail).
*/
for (pass = 0; pass < 2; pass ++) {
for (nsfile = namespace_files + 1 - pass; nsfile->nstype; nsfile++) {
if (nsfile->fd < 0)
continue;
if (nsfile->nstype == CLONE_NEWPID && do_fork == -1)
do_fork = 1;
if (setns(nsfile->fd, nsfile->nstype)) {
if (pass != 0)
err(EXIT_FAILURE,
_("reassociate to namespace '%s' failed"),
nsfile->name);
else
continue;
}
close(nsfile->fd);
nsfile->fd = -1;
}
}
/* Remember the current working directory if I'm not changing it */
if (root_fd >= 0 && wd_fd < 0) {
wd_fd = open(".", O_RDONLY);
if (wd_fd < 0)
err(EXIT_FAILURE,
_("cannot open current working directory"));
}
/* Change the root directory */
if (root_fd >= 0) {
if (fchdir(root_fd) < 0)
err(EXIT_FAILURE,
_("change directory by root file descriptor failed"));
if (chroot(".") < 0)
err(EXIT_FAILURE, _("chroot failed"));
close(root_fd);
root_fd = -1;
}
/* Change the working directory */
if (wd_fd >= 0) {
if (fchdir(wd_fd) < 0)
err(EXIT_FAILURE,
_("change directory by working directory file descriptor failed"));
close(wd_fd);
wd_fd = -1;
}
if (do_fork == 1)
continue_as_child();
if (force_uid || force_gid) {
if (force_gid && setgroups(0, NULL) != 0 && setgroups_nerrs) /* drop supplementary groups */
err(EXIT_FAILURE, _("setgroups failed"));
if (force_gid && setgid(gid) < 0) /* change GID */
err(EXIT_FAILURE, _("setgid failed"));
if (force_uid && setuid(uid) < 0) /* change UID */
err(EXIT_FAILURE, _("setuid failed"));
}
if (optind < argc) {
execvp(argv[optind], argv + optind);
errexec(argv[optind]);
}
exec_shell();
}
