[thirdparty/util-linux.git] / sys-utils / nsenter.c

/*
 * 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 <sys/types.h>
#include <sys/wait.h>
#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 "strutils.h"
#include "nls.h"
#include "c.h"
#include "closestream.h"
#include "namespace.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 first, so that it is entered
	 * first.  This gives an unprivileged user the potential to
	 * enter the other namespaces.
	 */
	{ .nstype = CLONE_NEWUSER, .name = "ns/user", .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 usage(int status)
{
	FILE *out = status == EXIT_SUCCESS ? stdout : stderr;

	fputs(USAGE_HEADER, out);
	fprintf(out, _(" %s [options] <program> [args...]\n"),
		program_invocation_short_name);

	fputs(USAGE_OPTIONS, out);
	fputs(_(" -t, --target <pid>     target process to get namespaces from\n"
		" -m, --mount [=<file>]  enter mount namespace\n"
		" -u, --uts   [=<file>]  enter UTS namespace (hostname etc)\n"
		" -i, --ipc   [=<file>]  enter System V IPC namespace\n"
		" -n, --net   [=<file>]  enter network namespace\n"
		" -p, --pid   [=<file>]  enter pid namespace\n"
		" -U, --user  [=<file>]  enter user namespace\n"
		" -r, --root  [=<dir>]   set the root directory\n"
		" -w, --wd    [=<dir>]   set the working directory\n"
		" -F, --no-fork          don't fork before exec'ing <program>\n"), out);
	fputs(USAGE_SEPARATOR, out);
	fputs(USAGE_HELP, out);
	fputs(USAGE_VERSION, out);
	fprintf(out, USAGE_MAN_TAIL("nsenter(1)"));

	exit(status);
}

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 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[])
{
	static const struct option longopts[] = {
		{ "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' },
		{ "root", optional_argument, NULL, 'r' },
		{ "wd", optional_argument, NULL, 'w' },
		{ "no-fork", no_argument, NULL, 'F' },
		{ NULL, 0, NULL, 0 }
	};

	struct namespace_file *nsfile;
	int c, namespaces = 0;
	bool do_rd = false, do_wd = false, do_fork = false;

	setlocale(LC_MESSAGES, "");
	bindtextdomain(PACKAGE, LOCALEDIR);
	textdomain(PACKAGE);
	atexit(close_stdout);

	while ((c =
		getopt_long(argc, argv, "hVt:m::u::i::n::p::U::r::w::F",
			    longopts, NULL)) != -1) {
		switch (c) {
		case 'h':
			usage(EXIT_SUCCESS);
		case 'V':
			printf(UTIL_LINUX_VERSION);
			return EXIT_SUCCESS;
		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':
			do_fork = true;
			if (optarg)
				open_namespace_fd(CLONE_NEWPID, optarg);
			else
				namespaces |= CLONE_NEWPID;
			break;
		case 'U':
			if (optarg)
				open_namespace_fd(CLONE_NEWUSER, optarg);
			else
				namespaces |= CLONE_NEWUSER;
			break;
		case 'F':
			do_fork = false;
			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;
		default:
			usage(EXIT_FAILURE);
		}
	}

	if (optind >= argc)
		usage(EXIT_FAILURE);

	/*
	 * 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);

	/*
	 * Now that we know which namespaces we want to enter, enter them.
	 */
	for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
		if (nsfile->fd < 0)
			continue;
		if (setns(nsfile->fd, nsfile->nstype))
			err(EXIT_FAILURE,
			    _("reassociate to namespace '%s' failed"),
			    nsfile->name);
		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)
		continue_as_child();

	execvp(argv[optind], argv + optind);

	err(EXIT_FAILURE, _("exec %s failed"), argv[optind]);
}
Commit	Line	Data
f8aa8e94 EB	1	/*
	2	* nsenter(1) - command-line interface for setns(2)
	3	*
	4	* Copyright (C) 2012-2013 Eric Biederman <ebiederm@xmission.com>
	5	*
	6	* This program is free software; you can redistribute it and/or modify it
	7	* under the terms of the GNU General Public License as published by the
	8	* Free Software Foundation; version 2.
	9	*
	10	* This program is distributed in the hope that it will be useful, but
	11	* WITHOUT ANY WARRANTY; without even the implied warranty of
	12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	* General Public License for more details.
	14	*
	15	* You should have received a copy of the GNU General Public License along
	16	* with this program; if not, write to the Free Software Foundation, Inc.,
	17	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
	18	*/
	19
	20	#include <sys/types.h>
	21	#include <sys/wait.h>
	22	#include <dirent.h>
	23	#include <errno.h>
	24	#include <getopt.h>
	25	#include <sched.h>
	26	#include <stdio.h>
	27	#include <stdlib.h>
984e1b7c	28	#include <stdbool.h>
f8aa8e94	29	#include <unistd.h>
dfd8b117	30	#include <assert.h>
f8aa8e94	31
0d3ec860	32	#include "strutils.h"
f8aa8e94 EB	33	#include "nls.h"
	34	#include "c.h"
	35	#include "closestream.h"
c91280a4	36	#include "namespace.h"
f8aa8e94	37
a167328a	38	static struct namespace_file {
f8aa8e94	39	int nstype;
f9bbdea6	40	const char *name;
f8aa8e94 EB	41	int fd;
f8aa8e94 EB	42	} namespace_files[] = {
ebbc87cd	43	/* Careful the order is significant in this array.
f8aa8e94 EB	44	*
	45	* The user namespace comes first, so that it is entered
	46	* first. This gives an unprivileged user the potential to
	47	* enter the other namespaces.
	48	*/
	49	{ .nstype = CLONE_NEWUSER, .name = "ns/user", .fd = -1 },
	50	{ .nstype = CLONE_NEWIPC, .name = "ns/ipc", .fd = -1 },
	51	{ .nstype = CLONE_NEWUTS, .name = "ns/uts", .fd = -1 },
	52	{ .nstype = CLONE_NEWNET, .name = "ns/net", .fd = -1 },
	53	{ .nstype = CLONE_NEWPID, .name = "ns/pid", .fd = -1 },
	54	{ .nstype = CLONE_NEWNS, .name = "ns/mnt", .fd = -1 },
9905912f	55	{ .nstype = 0, .name = NULL, .fd = -1 }
f8aa8e94 EB	56	};
	57
	58	static void usage(int status)
	59	{
	60	FILE *out = status == EXIT_SUCCESS ? stdout : stderr;
	61
	62	fputs(USAGE_HEADER, out);
	63	fprintf(out, _(" %s [options] <program> [args...]\n"),
	64	program_invocation_short_name);
	65
	66	fputs(USAGE_OPTIONS, out);
620d3f2d KZ	67	fputs(_(" -t, --target <pid> target process to get namespaces from\n"
	68	" -m, --mount [=<file>] enter mount namespace\n"
	69	" -u, --uts [=<file>] enter UTS namespace (hostname etc)\n"
	70	" -i, --ipc [=<file>] enter System V IPC namespace\n"
	71	" -n, --net [=<file>] enter network namespace\n"
	72	" -p, --pid [=<file>] enter pid namespace\n"
	73	" -U, --user [=<file>] enter user namespace\n"
620d3f2d	74	" -r, --root [=<dir>] set the root directory\n"
28384adc ZJS	75	" -w, --wd [=<dir>] set the working directory\n"
28384adc ZJS	76	" -F, --no-fork don't fork before exec'ing <program>\n"), out);
f8aa8e94 EB	77	fputs(USAGE_SEPARATOR, out);
	78	fputs(USAGE_HELP, out);
	79	fputs(USAGE_VERSION, out);
	80	fprintf(out, USAGE_MAN_TAIL("nsenter(1)"));
	81
	82	exit(status);
	83	}
	84
	85	static pid_t namespace_target_pid = 0;
	86	static int root_fd = -1;
	87	static int wd_fd = -1;
	88
f9bbdea6	89	static void open_target_fd(int fd, const char type, const char *path)
f8aa8e94 EB	90	{
	91	char pathbuf[PATH_MAX];
	92
	93	if (!path && namespace_target_pid) {
	94	snprintf(pathbuf, sizeof(pathbuf), "/proc/%u/%s",
a167328a	95	namespace_target_pid, type);
f8aa8e94 EB	96	path = pathbuf;
	97	}
	98	if (!path)
a167328a SK	99	errx(EXIT_FAILURE,
	100	_("neither filename nor target pid supplied for %s"),
	101	type);
f8aa8e94 EB	102
	103	if (*fd >= 0)
	104	close(*fd);
	105
	106	*fd = open(path, O_RDONLY);
	107	if (*fd < 0)
8b7a7750	108	err(EXIT_FAILURE, _("cannot open %s"), path);
f8aa8e94 EB	109	}
f8aa8e94 EB	110
f9bbdea6	111	static void open_namespace_fd(int nstype, const char *path)
f8aa8e94 EB	112	{
	113	struct namespace_file *nsfile;
	114
	115	for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
	116	if (nstype != nsfile->nstype)
	117	continue;
	118
	119	open_target_fd(&nsfile->fd, nsfile->name, path);
	120	return;
	121	}
	122	/* This should never happen */
dfd8b117	123	assert(nsfile->nstype);
f8aa8e94 EB	124	}
f8aa8e94 EB	125
c9515f86 EB	126	static void continue_as_child(void)
	127	{
	128	pid_t child = fork();
	129	int status;
	130	pid_t ret;
	131
	132	if (child < 0)
	133	err(EXIT_FAILURE, _("fork failed"));
	134
	135	/* Only the child returns */
	136	if (child == 0)
	137	return;
	138
	139	for (;;) {
	140	ret = waitpid(child, &status, WUNTRACED);
	141	if ((ret == child) && (WIFSTOPPED(status))) {
	142	/* The child suspended so suspend us as well */
	143	kill(getpid(), SIGSTOP);
	144	kill(child, SIGCONT);
	145	} else {
	146	break;
	147	}
	148	}
	149	/* Return the child's exit code if possible */
	150	if (WIFEXITED(status)) {
	151	exit(WEXITSTATUS(status));
a167328a	152	} else if (WIFSIGNALED(status)) {
c9515f86 EB	153	kill(getpid(), WTERMSIG(status));
	154	}
	155	exit(EXIT_FAILURE);
	156	}
	157
f8aa8e94 EB	158	int main(int argc, char *argv[])
	159	{
	160	static const struct option longopts[] = {
	161	{ "help", no_argument, NULL, 'h' },
	162	{ "version", no_argument, NULL, 'V'},
	163	{ "target", required_argument, NULL, 't' },
	164	{ "mount", optional_argument, NULL, 'm' },
	165	{ "uts", optional_argument, NULL, 'u' },
	166	{ "ipc", optional_argument, NULL, 'i' },
	167	{ "net", optional_argument, NULL, 'n' },
	168	{ "pid", optional_argument, NULL, 'p' },
	169	{ "user", optional_argument, NULL, 'U' },
f8aa8e94 EB	170	{ "root", optional_argument, NULL, 'r' },
f8aa8e94 EB	171	{ "wd", optional_argument, NULL, 'w' },
28384adc	172	{ "no-fork", no_argument, NULL, 'F' },
f8aa8e94 EB	173	{ NULL, 0, NULL, 0 }
	174	};
	175
	176	struct namespace_file *nsfile;
984e1b7c	177	int c, namespaces = 0;
28384adc	178	bool do_rd = false, do_wd = false, do_fork = false;
f8aa8e94 EB	179
	180	setlocale(LC_MESSAGES, "");
	181	bindtextdomain(PACKAGE, LOCALEDIR);
	182	textdomain(PACKAGE);
	183	atexit(close_stdout);
	184
28384adc ZJS	185	while ((c =
	186	getopt_long(argc, argv, "hVt:m::u::i::n::p::U::r::w::F",
	187	longopts, NULL)) != -1) {
	188	switch (c) {
f8aa8e94 EB	189	case 'h':
	190	usage(EXIT_SUCCESS);
	191	case 'V':
	192	printf(UTIL_LINUX_VERSION);
	193	return EXIT_SUCCESS;
	194	case 't':
a167328a SK	195	namespace_target_pid =
a167328a SK	196	strtoul_or_err(optarg, _("failed to parse pid"));
f8aa8e94 EB	197	break;
f8aa8e94 EB	198	case 'm':
984e1b7c ZJS	199	if (optarg)
	200	open_namespace_fd(CLONE_NEWNS, optarg);
	201	else
	202	namespaces \|= CLONE_NEWNS;
f8aa8e94 EB	203	break;
f8aa8e94 EB	204	case 'u':
984e1b7c ZJS	205	if (optarg)
	206	open_namespace_fd(CLONE_NEWUTS, optarg);
	207	else
	208	namespaces \|= CLONE_NEWUTS;
f8aa8e94 EB	209	break;
f8aa8e94 EB	210	case 'i':
984e1b7c ZJS	211	if (optarg)
	212	open_namespace_fd(CLONE_NEWIPC, optarg);
	213	else
	214	namespaces \|= CLONE_NEWIPC;
f8aa8e94 EB	215	break;
f8aa8e94 EB	216	case 'n':
984e1b7c ZJS	217	if (optarg)
	218	open_namespace_fd(CLONE_NEWNET, optarg);
	219	else
	220	namespaces \|= CLONE_NEWNET;
f8aa8e94 EB	221	break;
f8aa8e94 EB	222	case 'p':
28384adc	223	do_fork = true;
984e1b7c ZJS	224	if (optarg)
	225	open_namespace_fd(CLONE_NEWPID, optarg);
	226	else
	227	namespaces \|= CLONE_NEWPID;
f8aa8e94 EB	228	break;
f8aa8e94 EB	229	case 'U':
984e1b7c ZJS	230	if (optarg)
	231	open_namespace_fd(CLONE_NEWUSER, optarg);
	232	else
	233	namespaces \|= CLONE_NEWUSER;
f8aa8e94	234	break;
28384adc ZJS	235	case 'F':
28384adc ZJS	236	do_fork = false;
f8aa8e94 EB	237	break;
f8aa8e94 EB	238	case 'r':
984e1b7c ZJS	239	if (optarg)
	240	open_target_fd(&root_fd, "root", optarg);
	241	else
	242	do_rd = true;
f8aa8e94 EB	243	break;
f8aa8e94 EB	244	case 'w':
984e1b7c ZJS	245	if (optarg)
	246	open_target_fd(&wd_fd, "cwd", optarg);
	247	else
	248	do_wd = true;
f8aa8e94 EB	249	break;
	250	default:
	251	usage(EXIT_FAILURE);
	252	}
	253	}
	254
a167328a	255	if (optind >= argc)
f8aa8e94 EB	256	usage(EXIT_FAILURE);
f8aa8e94 EB	257
984e1b7c ZJS	258	/*
	259	* Open remaining namespace and directory descriptors.
	260	*/
	261	for (nsfile = namespace_files; nsfile->nstype; nsfile++)
	262	if (nsfile->nstype & namespaces)
	263	open_namespace_fd(nsfile->nstype, NULL);
	264	if (do_rd)
	265	open_target_fd(&root_fd, "root", NULL);
	266	if (do_wd)
	267	open_target_fd(&wd_fd, "cwd", NULL);
	268
f8aa8e94 EB	269	/*
	270	* Now that we know which namespaces we want to enter, enter them.
	271	*/
	272	for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
	273	if (nsfile->fd < 0)
	274	continue;
	275	if (setns(nsfile->fd, nsfile->nstype))
a167328a SK	276	err(EXIT_FAILURE,
a167328a SK	277	_("reassociate to namespace '%s' failed"),
f8aa8e94 EB	278	nsfile->name);
	279	close(nsfile->fd);
	280	nsfile->fd = -1;
	281	}
	282
	283	/* Remember the current working directory if I'm not changing it */
	284	if (root_fd >= 0 && wd_fd < 0) {
	285	wd_fd = open(".", O_RDONLY);
	286	if (wd_fd < 0)
a167328a SK	287	err(EXIT_FAILURE,
a167328a SK	288	_("cannot open current working directory"));
f8aa8e94 EB	289	}
	290
	291	/* Change the root directory */
	292	if (root_fd >= 0) {
	293	if (fchdir(root_fd) < 0)
a167328a SK	294	err(EXIT_FAILURE,
a167328a SK	295	_("change directory by root file descriptor failed"));
f8aa8e94 EB	296
	297	if (chroot(".") < 0)
	298	err(EXIT_FAILURE, _("chroot failed"));
	299
	300	close(root_fd);
	301	root_fd = -1;
	302	}
	303
	304	/* Change the working directory */
	305	if (wd_fd >= 0) {
	306	if (fchdir(wd_fd) < 0)
a167328a SK	307	err(EXIT_FAILURE,
a167328a SK	308	_("change directory by working directory file descriptor failed"));
f8aa8e94 EB	309
	310	close(wd_fd);
	311	wd_fd = -1;
	312	}
	313
c9515f86 EB	314	if (do_fork)
c9515f86 EB	315	continue_as_child();
f8aa8e94 EB	316
	317	execvp(argv[optind], argv + optind);
	318
	319	err(EXIT_FAILURE, _("exec %s failed"), argv[optind]);
	320	}