File: unshare.c

package info (click to toggle)
util-linux 2.25.2-6
  • links: PTS, VCS
  • area: main
  • in suites: jessie, jessie-kfreebsd
  • size: 60,764 kB
  • ctags: 11,189
  • sloc: ansic: 103,273; sh: 18,345; makefile: 322; python: 316; xml: 232; csh: 37; sed: 16
file content (214 lines) | stat: -rw-r--r-- 5,667 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
/*
 * 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>

/* we only need some defines missing in sys/mount.h, no libmount linkage */
#include <libmount.h>

#include "nls.h"
#include "c.h"
#include "closestream.h"
#include "namespace.h"
#include "exec_shell.h"
#include "xalloc.h"
#include "pathnames.h"
#include "all-io.h"

static void disable_setgroups(void)
{
	const char *file = _PATH_PROC_SETGROUPS;
	const char *deny = "deny";
	int fd;

	fd = open(file, O_WRONLY);
	if (fd < 0) {
		if (errno == ENOENT)
			return;
		 err(EXIT_FAILURE, _("cannot open %s"), file);
	}

	if (write_all(fd, deny, strlen(deny)))
		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 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(_(" -m, --mount               unshare mounts namespace\n"), out);
	fputs(_(" -u, --uts                 unshare UTS namespace (hostname etc)\n"), out);
	fputs(_(" -i, --ipc                 unshare System V IPC namespace\n"), out);
	fputs(_(" -n, --net                 unshare network namespace\n"), out);
	fputs(_(" -p, --pid                 unshare pid namespace\n"), out);
	fputs(_(" -U, --user                unshare user namespace\n"), out);
	fputs(_(" -f, --fork                fork before launching <program>\n"), out);
	fputs(_("     --mount-proc[=<dir>]  mount proc filesystem first (implies --mount)\n"), out);
	fputs(_(" -r, --map-root-user       map current user to root (implies --user)\n"), out);

	fputs(USAGE_SEPARATOR, out);
	fputs(USAGE_HELP, out);
	fputs(USAGE_VERSION, out);
	fprintf(out, USAGE_MAN_TAIL("unshare(1)"));

	exit(status);
}

int main(int argc, char *argv[])
{
	enum {
		OPT_MOUNTPROC = CHAR_MAX + 1
	};
	static const struct option longopts[] = {
		{ "help", no_argument, 0, 'h' },
		{ "version", no_argument, 0, 'V'},
		{ "mount", no_argument, 0, 'm' },
		{ "uts", no_argument, 0, 'u' },
		{ "ipc", no_argument, 0, 'i' },
		{ "net", no_argument, 0, 'n' },
		{ "pid", no_argument, 0, 'p' },
		{ "user", no_argument, 0, 'U' },
		{ "fork", no_argument, 0, 'f' },
		{ "mount-proc", optional_argument, 0, OPT_MOUNTPROC },
		{ "map-root-user", no_argument, 0, 'r' },
		{ NULL, 0, 0, 0 }
	};

	int unshare_flags = 0;
	int c, forkit = 0, maproot = 0;
	const char *procmnt = NULL;
	uid_t real_euid = geteuid();
	gid_t real_egid = getegid();;

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

	while ((c = getopt_long(argc, argv, "+fhVmuinpUr", longopts, NULL)) != -1) {
		switch (c) {
		case 'f':
			forkit = 1;
			break;
		case 'h':
			usage(EXIT_SUCCESS);
		case 'V':
			printf(UTIL_LINUX_VERSION);
			return EXIT_SUCCESS;
		case 'm':
			unshare_flags |= CLONE_NEWNS;
			break;
		case 'u':
			unshare_flags |= CLONE_NEWUTS;
			break;
		case 'i':
			unshare_flags |= CLONE_NEWIPC;
			break;
		case 'n':
			unshare_flags |= CLONE_NEWNET;
			break;
		case 'p':
			unshare_flags |= CLONE_NEWPID;
			break;
		case 'U':
			unshare_flags |= CLONE_NEWUSER;
			break;
		case OPT_MOUNTPROC:
			unshare_flags |= CLONE_NEWNS;
			procmnt = optarg ? optarg : "/proc";
			break;
		case 'r':
			unshare_flags |= CLONE_NEWUSER;
			maproot = 1;
			break;
		default:
			usage(EXIT_FAILURE);
		}
	}

	if (-1 == unshare(unshare_flags))
		err(EXIT_FAILURE, _("unshare failed"));

	if (forkit) {
		int status;
		pid_t pid = fork();

		switch(pid) {
		case -1:
			err(EXIT_FAILURE, _("fork failed"));
		case 0:	/* child */
			break;
		default: /* parent */
			if (waitpid(pid, &status, 0) == -1)
				err(EXIT_FAILURE, _("waitpid failed"));
			if (WIFEXITED(status))
				return WEXITSTATUS(status);
			else if (WIFSIGNALED(status))
				kill(getpid(), WTERMSIG(status));
			err(EXIT_FAILURE, _("child exit failed"));
		}
	}

	if (maproot) {
		disable_setgroups();
		map_id(_PATH_PROC_UIDMAP, 0, real_euid);
		map_id(_PATH_PROC_GIDMAP, 0, real_egid);
	}

	if (procmnt &&
	    (mount("none", procmnt, NULL, MS_PRIVATE|MS_REC, NULL) != 0 ||
	     mount("proc", procmnt, "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) != 0))
			err(EXIT_FAILURE, _("mount %s failed"), procmnt);

	if (optind < argc) {
		execvp(argv[optind], argv + optind);
		err(EXIT_FAILURE, _("failed to execute %s"), argv[optind]);
	}
	exec_shell();
}