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authorBartosz Golaszewski <bartekgola@gmail.com>2016-04-01 22:17:25 +0200
committerDenys Vlasenko <vda.linux@googlemail.com>2016-04-01 22:19:35 +0200
commit80c934a2517f7bfc7642da6555d7ca01bc6f2edd (patch)
tree29de902cabc74253cb5cffe4db4aff1bc0737d8a /util-linux
parentc4199f22d0f7793b70db51c01783f0d45afce3d4 (diff)
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nsenter: new applet
function old new delta nsenter_main - 663 +663 .rodata 155147 155612 +465 packed_usage 30536 30708 +172 nsenter_longopts - 116 +116 open_by_path_or_target - 58 +58 applet_names 2518 2526 +8 applet_main 2920 2928 +8 ------------------------------------------------------------------------------ (add/remove: 4/0 grow/shrink: 4/0 up/down: 1490/0) Total: 1490 bytes text data bss dec hex filename 827956 4078 9080 841114 cd59a busybox_old 829214 4086 9080 842380 cda8c busybox_unstripped Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'util-linux')
-rw-r--r--util-linux/nsenter.c286
1 files changed, 286 insertions, 0 deletions
diff --git a/util-linux/nsenter.c b/util-linux/nsenter.c
new file mode 100644
index 000000000..9c1dabaa8
--- /dev/null
+++ b/util-linux/nsenter.c
@@ -0,0 +1,286 @@
1/* vi: set sw=4 ts=4: */
2/*
3 * Mini nsenter implementation for busybox.
4 *
5 * Copyright (C) 2016 by Bartosz Golaszewski <bartekgola@gmail.com>
6 *
7 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
8 */
9
10//config:config NSENTER
11//config: bool "nsenter"
12//config: default y
13//config: select PLATFORM_LINUX
14//config: help
15//config: Run program with namespaces of other processes.
16//config:
17//config:config FEATURE_NSENTER_LONG_OPTS
18//config: bool "Enable long options"
19//config: default y
20//config: depends on NSENTER && LONG_OPTS
21//config: help
22//config: Support long options for the nsenter applet. This makes
23//config: the busybox implementation more compatible with upstream.
24
25//applet:IF_NSENTER(APPLET(nsenter, BB_DIR_USR_BIN, BB_SUID_DROP))
26
27//kbuild:lib-$(CONFIG_NSENTER) += nsenter.o
28
29//usage:#define nsenter_trivial_usage
30//usage: "[OPTIONS] [PROG [ARGS]]"
31//usage:#if ENABLE_FEATURE_NSENTER_LONG_OPTS
32//usage:#define nsenter_full_usage "\n"
33//usage: "\n -t, --target=PID Target process to get namespaces from"
34//usage: "\n -m, --mount[=FILE] Enter mount namespace"
35//usage: "\n -u, --uts[=FILE] Enter UTS namespace (hostname etc)"
36//usage: "\n -i, --ipc[=FILE] Enter System V IPC namespace"
37//usage: "\n -n, --net[=FILE] Enter network namespace"
38//usage: "\n -p, --pid[=FILE] Enter pid namespace"
39//usage: "\n -U, --user[=FILE] Enter user namespace"
40//usage: "\n -S, --setuid=UID Set uid in entered namespace"
41//usage: "\n -G, --setgid=GID Set gid in entered namespace"
42//usage: "\n --preserve-credentials Don't touch uids or gids"
43//usage: "\n -r, --root[=DIR] Set root directory"
44//usage: "\n -w, --wd[=DIR] Set working directory"
45//usage: "\n -F, --no-fork Don't fork before exec'ing PROG"
46//usage:#else
47//usage:#define nsenter_full_usage "\n"
48//usage: "\n -t PID Target process to get namespaces from"
49//usage: "\n -m[FILE] Enter mount namespace"
50//usage: "\n -u[FILE] Enter UTS namespace (hostname etc)"
51//usage: "\n -i[FILE] Enter System V IPC namespace"
52//usage: "\n -n[FILE] Enter network namespace"
53//usage: "\n -p[FILE] Enter pid namespace"
54//usage: "\n -U[FILE] Enter user namespace"
55//usage: "\n -S UID Set uid in entered namespace"
56//usage: "\n -G GID Set gid in entered namespace"
57//usage: "\n -r[DIR] Set root directory"
58//usage: "\n -w[DIR] Set working directory"
59//usage: "\n -F Don't fork before exec'ing PROG"
60//usage:#endif
61
62#include <sched.h>
63#include "libbb.h"
64
65struct namespace_descr {
66 int flag; /* value passed to setns() */
67 char ns_nsfile8[8]; /* "ns/" + namespace file in process' procfs entry */
68};
69
70struct namespace_ctx {
71 char *path; /* optional path to a custom ns file */
72 int fd; /* opened namespace file descriptor */
73};
74
75enum {
76 OPT_user = 1 << 0,
77 OPT_ipc = 1 << 1,
78 OPT_uts = 1 << 2,
79 OPT_network = 1 << 3,
80 OPT_pid = 1 << 4,
81 OPT_mount = 1 << 5,
82 OPT_target = 1 << 6,
83 OPT_setuid = 1 << 7,
84 OPT_setgid = 1 << 8,
85 OPT_root = 1 << 9,
86 OPT_wd = 1 << 10,
87 OPT_nofork = 1 << 11,
88 OPT_prescred = (1 << 12) * ENABLE_FEATURE_NSENTER_LONG_OPTS,
89};
90enum {
91 NS_USR_POS = 0,
92 NS_IPC_POS,
93 NS_UTS_POS,
94 NS_NET_POS,
95 NS_PID_POS,
96 NS_MNT_POS,
97 NS_COUNT,
98};
99/*
100 * The order is significant in nsenter.
101 * The user namespace comes first, so that it is entered first.
102 * This gives an unprivileged user the potential to enter other namespaces.
103 */
104static const struct namespace_descr ns_list[] = {
105 { CLONE_NEWUSER, "ns/user", },
106 { CLONE_NEWIPC, "ns/ipc", },
107 { CLONE_NEWUTS, "ns/uts", },
108 { CLONE_NEWNET, "ns/net", },
109 { CLONE_NEWPID, "ns/pid", },
110 { CLONE_NEWNS, "ns/mnt", },
111};
112/*
113 * Upstream nsenter doesn't support the short option for --preserve-credentials
114 */
115static const char opt_str[] = "U::i::u::n::p::m::""t+S+G+r::w::F";
116
117#if ENABLE_FEATURE_NSENTER_LONG_OPTS
118static const char nsenter_longopts[] ALIGN1 =
119 "user\0" Optional_argument "U"
120 "ipc\0" Optional_argument "i"
121 "uts\0" Optional_argument "u"
122 "network\0" Optional_argument "n"
123 "pid\0" Optional_argument "p"
124 "mount\0" Optional_argument "m"
125 "target\0" Required_argument "t"
126 "setuid\0" Required_argument "S"
127 "setgid\0" Required_argument "G"
128 "root\0" Optional_argument "r"
129 "wd\0" Optional_argument "w"
130 "no-fork\0" No_argument "F"
131 "preserve-credentials\0" No_argument "\xff"
132 ;
133#endif
134
135/*
136 * Open a file and return the new descriptor. If a full path is provided in
137 * fs_path, then the file to which it points is opened. Otherwise (fd_path is
138 * NULL) the routine builds a path to a procfs file using the following
139 * template: '/proc/<target_pid>/<target_file>'.
140 */
141static int open_by_path_or_target(const char *path,
142 pid_t target_pid, const char *target_file)
143{
144 char proc_path_buf[sizeof("/proc/%u/1234567890") + sizeof(int)*3];
145
146 if (!path) {
147 if (target_pid == 0) {
148 /* Example:
149 * "nsenter -p PROG" - neither -pFILE nor -tPID given.
150 */
151 bb_show_usage();
152 }
153 snprintf(proc_path_buf, sizeof(proc_path_buf),
154 "/proc/%u/%s", (unsigned)target_pid, target_file);
155 path = proc_path_buf;
156 }
157
158 return xopen(path, O_RDONLY);
159}
160
161int nsenter_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
162int nsenter_main(int argc UNUSED_PARAM, char **argv)
163{
164 int i;
165 unsigned int opts;
166 const char *root_dir_str = NULL;
167 const char *wd_str = NULL;
168 struct namespace_ctx ns_ctx_list[NS_COUNT];
169 int setgroups_failed;
170 int root_fd, wd_fd;
171 int target_pid = 0;
172 int uid = 0;
173 int gid = 0;
174
175 memset(ns_ctx_list, 0, sizeof(ns_ctx_list));
176
177 IF_FEATURE_NSENTER_LONG_OPTS(applet_long_options = nsenter_longopts);
178 opts = getopt32(argv, opt_str,
179 &ns_ctx_list[NS_USR_POS].path,
180 &ns_ctx_list[NS_IPC_POS].path,
181 &ns_ctx_list[NS_UTS_POS].path,
182 &ns_ctx_list[NS_NET_POS].path,
183 &ns_ctx_list[NS_PID_POS].path,
184 &ns_ctx_list[NS_MNT_POS].path,
185 &target_pid, &uid, &gid,
186 &root_dir_str, &wd_str
187 );
188 argv += optind;
189
190 root_fd = wd_fd = -1;
191 if (opts & OPT_root)
192 root_fd = open_by_path_or_target(root_dir_str,
193 target_pid, "root");
194 if (opts & OPT_wd)
195 wd_fd = open_by_path_or_target(wd_str, target_pid, "cwd");
196
197 for (i = 0; i < NS_COUNT; i++) {
198 const struct namespace_descr *ns = &ns_list[i];
199 struct namespace_ctx *ns_ctx = &ns_ctx_list[i];
200
201 ns_ctx->fd = -1;
202 if (opts & (1 << i))
203 ns_ctx->fd = open_by_path_or_target(ns_ctx->path,
204 target_pid, ns->ns_nsfile8);
205 }
206
207 /*
208 * Entering the user namespace without --preserve-credentials implies
209 * --setuid & --setgid and clearing root's groups.
210 */
211 setgroups_failed = 0;
212 if ((opts & OPT_user) && !(opts & OPT_prescred)) {
213 opts |= (OPT_setuid | OPT_setgid);
214 /*
215 * We call setgroups() before and after setns() and only
216 * bail-out if it fails twice.
217 */
218 setgroups_failed = (setgroups(0, NULL) < 0);
219 }
220
221 for (i = 0; i < NS_COUNT; i++) {
222 const struct namespace_descr *ns = &ns_list[i];
223 struct namespace_ctx *ns_ctx = &ns_ctx_list[i];
224
225 if (ns_ctx->fd < 0)
226 continue;
227 if (setns(ns_ctx->fd, ns->flag)) {
228 bb_perror_msg_and_die(
229 "setns(): can't reassociate to namespace '%s'",
230 ns->ns_nsfile8 + 3 /* skip over "ns/" */
231 );
232 }
233 /*close(ns_ctx->fd);*/
234 /*ns_ctx->fd = -1;*/
235 }
236
237 if (root_fd >= 0) {
238 if (wd_fd < 0) {
239 /*
240 * Save the current working directory if we're not
241 * changing it.
242 */
243 wd_fd = xopen(".", O_RDONLY);
244 }
245 xfchdir(root_fd);
246 xchroot(".");
247 /*close(root_fd);*/
248 /*root_fd = -1;*/
249 }
250
251 if (wd_fd >= 0) {
252 xfchdir(wd_fd);
253 /*close(wd_fd);*/
254 /*wd_fd = -1;*/
255 }
256
257 /*
258 * Entering the pid namespace implies forking unless it's been
259 * explicitly requested by the user not to.
260 */
261 if (!(opts & OPT_nofork) && (opts & OPT_pid)) {
262 pid_t pid = xvfork();
263 if (pid > 0) {
264 /* Parent */
265 int exit_status = wait_for_exitstatus(pid);
266 if (WIFSIGNALED(exit_status))
267 kill_myself_with_sig(WTERMSIG(exit_status));
268 return WEXITSTATUS(exit_status);
269 }
270 /* Child continues */
271 }
272
273 if (opts & OPT_setgid) {
274 if (setgroups(0, NULL) < 0 && setgroups_failed)
275 bb_perror_msg_and_die("setgroups");
276 xsetgid(gid);
277 }
278 if (opts & OPT_setuid)
279 xsetuid(uid);
280
281 if (*argv) {
282 BB_EXECVP_or_die(argv);
283 }
284
285 run_shell(getenv("SHELL"), /*login:*/ 1, NULL, NULL);
286}
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