1 | /* vi: set sw=4 ts=4: */
|
---|
2 | /*
|
---|
3 | * Mini unshare 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 UNSHARE
|
---|
11 | //config: bool "unshare"
|
---|
12 | //config: default y
|
---|
13 | //config: depends on LONG_OPTS && !NOMMU
|
---|
14 | //config: select PLATFORM_LINUX
|
---|
15 | //config: help
|
---|
16 | //config: Run program with some namespaces unshared from parent.
|
---|
17 |
|
---|
18 | // depends on LONG_OPTS: it is awkward to exclude code which handles --propagation
|
---|
19 | // and --setgroups based on LONG_OPTS, so instead applet requires LONG_OPTS.
|
---|
20 | // depends on !NOMMU: we need fork()
|
---|
21 |
|
---|
22 | //applet:IF_UNSHARE(APPLET(unshare, BB_DIR_USR_BIN, BB_SUID_DROP))
|
---|
23 |
|
---|
24 | //kbuild:lib-$(CONFIG_UNSHARE) += unshare.o
|
---|
25 |
|
---|
26 | //usage:#define unshare_trivial_usage
|
---|
27 | //usage: "[OPTIONS] [PROG [ARGS]]"
|
---|
28 | //usage:#define unshare_full_usage "\n"
|
---|
29 | //usage: "\n -m, --mount[=FILE] Unshare mount namespace"
|
---|
30 | //usage: "\n -u, --uts[=FILE] Unshare UTS namespace (hostname etc.)"
|
---|
31 | //usage: "\n -i, --ipc[=FILE] Unshare System V IPC namespace"
|
---|
32 | //usage: "\n -n, --net[=FILE] Unshare network namespace"
|
---|
33 | //usage: "\n -p, --pid[=FILE] Unshare PID namespace"
|
---|
34 | //usage: "\n -U, --user[=FILE} Unshare user namespace"
|
---|
35 | //usage: "\n -f, --fork Fork before execing PROG"
|
---|
36 | //usage: "\n -r, --map-root-user Map current user to root (implies -u)"
|
---|
37 | //usage: "\n --mount-proc[=DIR] Mount /proc filesystem first (implies -m)"
|
---|
38 | //usage: "\n --propagation slave|shared|private|unchanged"
|
---|
39 | //usage: "\n Modify mount propagation in mount namespace"
|
---|
40 | //usage: "\n --setgroups allow|deny Control the setgroups syscall in user namespaces"
|
---|
41 |
|
---|
42 | #include <sched.h>
|
---|
43 | #ifndef CLONE_NEWUTS
|
---|
44 | # define CLONE_NEWUTS 0x04000000
|
---|
45 | #endif
|
---|
46 | #ifndef CLONE_NEWIPC
|
---|
47 | # define CLONE_NEWIPC 0x08000000
|
---|
48 | #endif
|
---|
49 | #ifndef CLONE_NEWUSER
|
---|
50 | # define CLONE_NEWUSER 0x10000000
|
---|
51 | #endif
|
---|
52 | #ifndef CLONE_NEWPID
|
---|
53 | # define CLONE_NEWPID 0x20000000
|
---|
54 | #endif
|
---|
55 | #ifndef CLONE_NEWNET
|
---|
56 | # define CLONE_NEWNET 0x40000000
|
---|
57 | #endif
|
---|
58 |
|
---|
59 | #include <sys/mount.h>
|
---|
60 | #ifndef MS_REC
|
---|
61 | # define MS_REC (1 << 14)
|
---|
62 | #endif
|
---|
63 | #ifndef MS_PRIVATE
|
---|
64 | # define MS_PRIVATE (1 << 18)
|
---|
65 | #endif
|
---|
66 | #ifndef MS_SLAVE
|
---|
67 | # define MS_SLAVE (1 << 19)
|
---|
68 | #endif
|
---|
69 | #ifndef MS_SHARED
|
---|
70 | # define MS_SHARED (1 << 20)
|
---|
71 | #endif
|
---|
72 |
|
---|
73 | #include "libbb.h"
|
---|
74 |
|
---|
75 | static void mount_or_die(const char *source, const char *target,
|
---|
76 | const char *fstype, unsigned long mountflags)
|
---|
77 | {
|
---|
78 | if (mount(source, target, fstype, mountflags, NULL)) {
|
---|
79 | bb_perror_msg_and_die("can't mount %s on %s (flags:0x%lx)",
|
---|
80 | source, target, mountflags);
|
---|
81 | /* fstype is always either NULL or "proc".
|
---|
82 | * "proc" is only used to mount /proc.
|
---|
83 | * No need to clutter up error message with fstype,
|
---|
84 | * it is easily deductible.
|
---|
85 | */
|
---|
86 | }
|
---|
87 | }
|
---|
88 |
|
---|
89 | #define PATH_PROC_SETGROUPS "/proc/self/setgroups"
|
---|
90 | #define PATH_PROC_UIDMAP "/proc/self/uid_map"
|
---|
91 | #define PATH_PROC_GIDMAP "/proc/self/gid_map"
|
---|
92 |
|
---|
93 | struct namespace_descr {
|
---|
94 | int flag;
|
---|
95 | const char nsfile4[4];
|
---|
96 | };
|
---|
97 |
|
---|
98 | struct namespace_ctx {
|
---|
99 | char *path;
|
---|
100 | };
|
---|
101 |
|
---|
102 | enum {
|
---|
103 | OPT_mount = 1 << 0,
|
---|
104 | OPT_uts = 1 << 1,
|
---|
105 | OPT_ipc = 1 << 2,
|
---|
106 | OPT_network = 1 << 3,
|
---|
107 | OPT_pid = 1 << 4,
|
---|
108 | OPT_user = 1 << 5, /* OPT_user, NS_USR_POS, and ns_list[] index must match! */
|
---|
109 | OPT_fork = 1 << 6,
|
---|
110 | OPT_map_root = 1 << 7,
|
---|
111 | OPT_mount_proc = 1 << 8,
|
---|
112 | OPT_propagation = 1 << 9,
|
---|
113 | OPT_setgroups = 1 << 10,
|
---|
114 | };
|
---|
115 | enum {
|
---|
116 | NS_MNT_POS = 0,
|
---|
117 | NS_UTS_POS,
|
---|
118 | NS_IPC_POS,
|
---|
119 | NS_NET_POS,
|
---|
120 | NS_PID_POS,
|
---|
121 | NS_USR_POS, /* OPT_user, NS_USR_POS, and ns_list[] index must match! */
|
---|
122 | NS_COUNT,
|
---|
123 | };
|
---|
124 | static const struct namespace_descr ns_list[] = {
|
---|
125 | { CLONE_NEWNS, "mnt" },
|
---|
126 | { CLONE_NEWUTS, "uts" },
|
---|
127 | { CLONE_NEWIPC, "ipc" },
|
---|
128 | { CLONE_NEWNET, "net" },
|
---|
129 | { CLONE_NEWPID, "pid" },
|
---|
130 | { CLONE_NEWUSER, "user" }, /* OPT_user, NS_USR_POS, and ns_list[] index must match! */
|
---|
131 | };
|
---|
132 |
|
---|
133 | /*
|
---|
134 | * Upstream unshare doesn't support short options for --mount-proc,
|
---|
135 | * --propagation, --setgroups.
|
---|
136 | * Optional arguments (namespace mountpoints) exist only for long opts,
|
---|
137 | * we are forced to use "fake" letters for them.
|
---|
138 | * '+': stop at first non-option.
|
---|
139 | */
|
---|
140 | static const char opt_str[] ALIGN1 = "+muinpU""fr""\xfd::""\xfe:""\xff:";
|
---|
141 | static const char unshare_longopts[] ALIGN1 =
|
---|
142 | "mount\0" Optional_argument "\xf0"
|
---|
143 | "uts\0" Optional_argument "\xf1"
|
---|
144 | "ipc\0" Optional_argument "\xf2"
|
---|
145 | "network\0" Optional_argument "\xf3"
|
---|
146 | "pid\0" Optional_argument "\xf4"
|
---|
147 | "user\0" Optional_argument "\xf5"
|
---|
148 | "fork\0" No_argument "f"
|
---|
149 | "map-root-user\0" No_argument "r"
|
---|
150 | "mount-proc\0" Optional_argument "\xfd"
|
---|
151 | "propagation\0" Required_argument "\xfe"
|
---|
152 | "setgroups\0" Required_argument "\xff"
|
---|
153 | ;
|
---|
154 |
|
---|
155 | /* Ugly-looking string reuse trick */
|
---|
156 | #define PRIVATE_STR "private\0""unchanged\0""shared\0""slave\0"
|
---|
157 | #define PRIVATE_UNCHANGED_SHARED_SLAVE PRIVATE_STR
|
---|
158 |
|
---|
159 | static unsigned long parse_propagation(const char *prop_str)
|
---|
160 | {
|
---|
161 | int i = index_in_strings(PRIVATE_UNCHANGED_SHARED_SLAVE, prop_str);
|
---|
162 | if (i < 0)
|
---|
163 | bb_error_msg_and_die("unrecognized: --%s=%s", "propagation", prop_str);
|
---|
164 | if (i == 0)
|
---|
165 | return MS_REC | MS_PRIVATE;
|
---|
166 | if (i == 1)
|
---|
167 | return 0;
|
---|
168 | if (i == 2)
|
---|
169 | return MS_REC | MS_SHARED;
|
---|
170 | return MS_REC | MS_SLAVE;
|
---|
171 | }
|
---|
172 |
|
---|
173 | static void mount_namespaces(pid_t pid, struct namespace_ctx *ns_ctx_list)
|
---|
174 | {
|
---|
175 | const struct namespace_descr *ns;
|
---|
176 | struct namespace_ctx *ns_ctx;
|
---|
177 | int i;
|
---|
178 |
|
---|
179 | for (i = 0; i < NS_COUNT; i++) {
|
---|
180 | char nsf[sizeof("/proc/%u/ns/AAAA") + sizeof(int)*3];
|
---|
181 |
|
---|
182 | ns = &ns_list[i];
|
---|
183 | ns_ctx = &ns_ctx_list[i];
|
---|
184 | if (!ns_ctx->path)
|
---|
185 | continue;
|
---|
186 | sprintf(nsf, "/proc/%u/ns/%.4s", (unsigned)pid, ns->nsfile4);
|
---|
187 | mount_or_die(nsf, ns_ctx->path, NULL, MS_BIND);
|
---|
188 | }
|
---|
189 | }
|
---|
190 |
|
---|
191 | int unshare_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
|
---|
192 | int unshare_main(int argc UNUSED_PARAM, char **argv)
|
---|
193 | {
|
---|
194 | int i;
|
---|
195 | unsigned int opts;
|
---|
196 | int unsflags;
|
---|
197 | uintptr_t need_mount;
|
---|
198 | const char *proc_mnt_target;
|
---|
199 | const char *prop_str;
|
---|
200 | const char *setgrp_str;
|
---|
201 | unsigned long prop_flags;
|
---|
202 | uid_t reuid = geteuid();
|
---|
203 | gid_t regid = getegid();
|
---|
204 | struct fd_pair fdp;
|
---|
205 | pid_t child = child; /* for compiler */
|
---|
206 | struct namespace_ctx ns_ctx_list[NS_COUNT];
|
---|
207 |
|
---|
208 | memset(ns_ctx_list, 0, sizeof(ns_ctx_list));
|
---|
209 | proc_mnt_target = "/proc";
|
---|
210 | prop_str = PRIVATE_STR;
|
---|
211 | setgrp_str = NULL;
|
---|
212 |
|
---|
213 | opt_complementary =
|
---|
214 | "\xf0""m" /* long opts (via their "fake chars") imply short opts */
|
---|
215 | ":\xf1""u"
|
---|
216 | ":\xf2""i"
|
---|
217 | ":\xf3""n"
|
---|
218 | ":\xf4""p"
|
---|
219 | ":\xf5""U"
|
---|
220 | ":ru" /* --map-root-user or -r implies -u */
|
---|
221 | ":\xfd""m" /* --mount-proc implies -m */
|
---|
222 | ;
|
---|
223 | applet_long_options = unshare_longopts;
|
---|
224 | opts = getopt32(argv, opt_str,
|
---|
225 | &proc_mnt_target, &prop_str, &setgrp_str,
|
---|
226 | &ns_ctx_list[NS_MNT_POS].path,
|
---|
227 | &ns_ctx_list[NS_UTS_POS].path,
|
---|
228 | &ns_ctx_list[NS_IPC_POS].path,
|
---|
229 | &ns_ctx_list[NS_NET_POS].path,
|
---|
230 | &ns_ctx_list[NS_PID_POS].path,
|
---|
231 | &ns_ctx_list[NS_USR_POS].path
|
---|
232 | );
|
---|
233 | argv += optind;
|
---|
234 | //bb_error_msg("opts:0x%x", opts);
|
---|
235 | //bb_error_msg("mount:%s", ns_ctx_list[NS_MNT_POS].path);
|
---|
236 | //bb_error_msg("proc_mnt_target:%s", proc_mnt_target);
|
---|
237 | //bb_error_msg("prop_str:%s", prop_str);
|
---|
238 | //bb_error_msg("setgrp_str:%s", setgrp_str);
|
---|
239 | //exit(1);
|
---|
240 |
|
---|
241 | if (setgrp_str) {
|
---|
242 | if (strcmp(setgrp_str, "allow") == 0) {
|
---|
243 | if (opts & OPT_map_root) {
|
---|
244 | bb_error_msg_and_die(
|
---|
245 | "--setgroups=allow and --map-root-user "
|
---|
246 | "are mutually exclusive"
|
---|
247 | );
|
---|
248 | }
|
---|
249 | } else {
|
---|
250 | /* It's not "allow", must be "deny" */
|
---|
251 | if (strcmp(setgrp_str, "deny") != 0)
|
---|
252 | bb_error_msg_and_die("unrecognized: --%s=%s",
|
---|
253 | "setgroups", setgrp_str);
|
---|
254 | }
|
---|
255 | }
|
---|
256 |
|
---|
257 | unsflags = 0;
|
---|
258 | need_mount = 0;
|
---|
259 | for (i = 0; i < NS_COUNT; i++) {
|
---|
260 | const struct namespace_descr *ns = &ns_list[i];
|
---|
261 | struct namespace_ctx *ns_ctx = &ns_ctx_list[i];
|
---|
262 |
|
---|
263 | if (opts & (1 << i))
|
---|
264 | unsflags |= ns->flag;
|
---|
265 |
|
---|
266 | need_mount |= (uintptr_t)(ns_ctx->path);
|
---|
267 | }
|
---|
268 | /* need_mount != 0 if at least one FILE was given */
|
---|
269 |
|
---|
270 | prop_flags = MS_REC | MS_PRIVATE;
|
---|
271 | /* Silently ignore --propagation if --mount is not requested. */
|
---|
272 | if (opts & OPT_mount)
|
---|
273 | prop_flags = parse_propagation(prop_str);
|
---|
274 |
|
---|
275 | /*
|
---|
276 | * Special case: if we were requested to unshare the mount namespace
|
---|
277 | * AND to make any namespace persistent (by bind mounting it) we need
|
---|
278 | * to spawn a child process which will wait for the parent to call
|
---|
279 | * unshare(), then mount parent's namespaces while still in the
|
---|
280 | * previous namespace.
|
---|
281 | */
|
---|
282 | fdp.wr = -1;
|
---|
283 | if (need_mount && (opts & OPT_mount)) {
|
---|
284 | /*
|
---|
285 | * Can't use getppid() in child, as we can be unsharing the
|
---|
286 | * pid namespace.
|
---|
287 | */
|
---|
288 | pid_t ppid = getpid();
|
---|
289 |
|
---|
290 | xpiped_pair(fdp);
|
---|
291 |
|
---|
292 | child = xfork();
|
---|
293 | if (child == 0) {
|
---|
294 | /* Child */
|
---|
295 | close(fdp.wr);
|
---|
296 |
|
---|
297 | /* Wait until parent calls unshare() */
|
---|
298 | read(fdp.rd, ns_ctx_list, 1); /* ...using bogus buffer */
|
---|
299 | /*close(fdp.rd);*/
|
---|
300 |
|
---|
301 | /* Mount parent's unshared namespaces. */
|
---|
302 | mount_namespaces(ppid, ns_ctx_list);
|
---|
303 | return EXIT_SUCCESS;
|
---|
304 | }
|
---|
305 | /* Parent continues */
|
---|
306 | }
|
---|
307 |
|
---|
308 | if (unshare(unsflags) != 0)
|
---|
309 | bb_perror_msg_and_die("unshare(0x%x)", unsflags);
|
---|
310 |
|
---|
311 | if (fdp.wr >= 0) {
|
---|
312 | close(fdp.wr); /* Release child */
|
---|
313 | close(fdp.rd); /* should close fd, to not confuse exec'ed PROG */
|
---|
314 | }
|
---|
315 |
|
---|
316 | if (need_mount) {
|
---|
317 | /* Wait for the child to finish mounting the namespaces. */
|
---|
318 | if (opts & OPT_mount) {
|
---|
319 | int exit_status = wait_for_exitstatus(child);
|
---|
320 | if (WIFEXITED(exit_status) &&
|
---|
321 | WEXITSTATUS(exit_status) != EXIT_SUCCESS)
|
---|
322 | return WEXITSTATUS(exit_status);
|
---|
323 | } else {
|
---|
324 | /*
|
---|
325 | * Regular way - we were requested to mount some other
|
---|
326 | * namespaces: mount them after the call to unshare().
|
---|
327 | */
|
---|
328 | mount_namespaces(getpid(), ns_ctx_list);
|
---|
329 | }
|
---|
330 | }
|
---|
331 |
|
---|
332 | /*
|
---|
333 | * When we're unsharing the pid namespace, it's not the process that
|
---|
334 | * calls unshare() that is put into the new namespace, but its first
|
---|
335 | * child. The user may want to use this option to spawn a new process
|
---|
336 | * that'll become PID 1 in this new namespace.
|
---|
337 | */
|
---|
338 | if (opts & OPT_fork) {
|
---|
339 | xvfork_parent_waits_and_exits();
|
---|
340 | /* Child continues */
|
---|
341 | }
|
---|
342 |
|
---|
343 | if (opts & OPT_map_root) {
|
---|
344 | char uidmap_buf[sizeof("%u 0 1") + sizeof(int)*3];
|
---|
345 |
|
---|
346 | /*
|
---|
347 | * Since Linux 3.19 unprivileged writing of /proc/self/gid_map
|
---|
348 | * has been disabled unless /proc/self/setgroups is written
|
---|
349 | * first to permanently disable the ability to call setgroups
|
---|
350 | * in that user namespace.
|
---|
351 | */
|
---|
352 | xopen_xwrite_close(PATH_PROC_SETGROUPS, "deny");
|
---|
353 | sprintf(uidmap_buf, "%u 0 1", (unsigned)reuid);
|
---|
354 | xopen_xwrite_close(PATH_PROC_UIDMAP, uidmap_buf);
|
---|
355 | sprintf(uidmap_buf, "%u 0 1", (unsigned)regid);
|
---|
356 | xopen_xwrite_close(PATH_PROC_GIDMAP, uidmap_buf);
|
---|
357 | } else
|
---|
358 | if (setgrp_str) {
|
---|
359 | /* Write "allow" or "deny" */
|
---|
360 | xopen_xwrite_close(PATH_PROC_SETGROUPS, setgrp_str);
|
---|
361 | }
|
---|
362 |
|
---|
363 | if (opts & OPT_mount) {
|
---|
364 | mount_or_die("none", "/", NULL, prop_flags);
|
---|
365 | }
|
---|
366 |
|
---|
367 | if (opts & OPT_mount_proc) {
|
---|
368 | /*
|
---|
369 | * When creating a new pid namespace, we might want the pid
|
---|
370 | * subdirectories in /proc to remain consistent with the new
|
---|
371 | * process IDs. Without --mount-proc the pids in /proc would
|
---|
372 | * still reflect the old pid namespace. This is why we make
|
---|
373 | * /proc private here and then do a fresh mount.
|
---|
374 | */
|
---|
375 | mount_or_die("none", proc_mnt_target, NULL, MS_PRIVATE | MS_REC);
|
---|
376 | mount_or_die("proc", proc_mnt_target, "proc", MS_NOSUID | MS_NOEXEC | MS_NODEV);
|
---|
377 | }
|
---|
378 |
|
---|
379 | exec_prog_or_SHELL(argv);
|
---|
380 | }
|
---|