Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 1 | /* Copyright (c) 2011 The Chromium OS Authors. All rights reserved. |
| 2 | * Use of this source code is governed by a BSD-style license that can be |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 3 | * found in the LICENSE file. |
| 4 | */ |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 5 | |
| 6 | #define _BSD_SOURCE |
| 7 | #define _GNU_SOURCE |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 8 | #include <ctype.h> |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 9 | #include <errno.h> |
| 10 | #include <grp.h> |
| 11 | #include <inttypes.h> |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 12 | #include <limits.h> |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 13 | #include <linux/capability.h> |
| 14 | #include <linux/securebits.h> |
| 15 | #include <pwd.h> |
| 16 | #include <sched.h> |
| 17 | #include <signal.h> |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 18 | #include <stdarg.h> |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 19 | #include <stdio.h> |
| 20 | #include <stdlib.h> |
| 21 | #include <string.h> |
| 22 | #include <syscall.h> |
| 23 | #include <sys/capability.h> |
| 24 | #include <sys/mount.h> |
| 25 | #include <sys/prctl.h> |
| 26 | #include <sys/wait.h> |
| 27 | #include <syslog.h> |
| 28 | #include <unistd.h> |
| 29 | |
| 30 | #include "libminijail.h" |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 31 | #include "libsyscalls.h" |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 32 | #include "libminijail-private.h" |
| 33 | |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 34 | /* Until these are reliably available in linux/prctl.h */ |
| 35 | #ifndef PR_SET_SECCOMP_FILTER |
| 36 | # define PR_SECCOMP_FILTER_SYSCALL 0 |
| 37 | # define PR_SECCOMP_FILTER_EVENT 1 |
| 38 | # define PR_GET_SECCOMP_FILTER 35 |
| 39 | # define PR_SET_SECCOMP_FILTER 36 |
| 40 | # define PR_CLEAR_SECCOMP_FILTER 37 |
| 41 | #endif |
| 42 | |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 43 | #define die(_msg, ...) do { \ |
| 44 | syslog(LOG_ERR, "libminijail: " _msg, ## __VA_ARGS__); \ |
| 45 | abort(); \ |
| 46 | } while (0) |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 47 | |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 48 | #define pdie(_msg, ...) \ |
| 49 | die(_msg ": %s", ## __VA_ARGS__, strerror(errno)) |
| 50 | |
| 51 | #define warn(_msg, ...) \ |
| 52 | syslog(LOG_WARNING, "libminijail: " _msg, ## __VA_ARGS__) |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 53 | |
| 54 | struct minijail *minijail_new(void) { |
| 55 | struct minijail *j = malloc(sizeof(*j)); |
| 56 | if (j) |
| 57 | memset(j, 0, sizeof(*j)); |
| 58 | return j; |
| 59 | } |
| 60 | |
| 61 | void minijail_change_uid(struct minijail *j, uid_t uid) { |
| 62 | if (uid == 0) |
| 63 | die("useless change to uid 0"); |
| 64 | j->uid = uid; |
| 65 | j->flags.uid = 1; |
| 66 | } |
| 67 | |
| 68 | void minijail_change_gid(struct minijail *j, gid_t gid) { |
| 69 | if (gid == 0) |
| 70 | die("useless change to gid 0"); |
| 71 | j->gid = gid; |
| 72 | j->flags.gid = 1; |
| 73 | } |
| 74 | |
| 75 | int minijail_change_user(struct minijail *j, const char *user) { |
| 76 | /* In principle this should use getpwnam(), but: |
| 77 | * 1) getpwnam_r() isn't actually reentrant anyway, since it uses a |
| 78 | * statically-allocated file descriptor internally |
| 79 | * 2) fgetpwnam() (by analogy with fgetpwent) would solve (1) except that it |
| 80 | * doesn't exist |
| 81 | * 3) sysconf() (see getpwnam_r(3)) is allowed to return a size that is not |
| 82 | * large enough, which means having to loop on growing the buffer we pass |
| 83 | * in |
| 84 | */ |
| 85 | struct passwd *pw = getpwnam(user); |
| 86 | if (!pw) |
| 87 | return errno; |
| 88 | minijail_change_uid(j, pw->pw_uid); |
Will Drewry | 2ddaad0 | 2011-09-16 11:36:08 -0500 | [diff] [blame] | 89 | j->user = strdup(user); |
| 90 | if (!j->user) |
| 91 | return -ENOMEM; |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 92 | j->usergid = pw->pw_gid; |
| 93 | return 0; |
| 94 | } |
| 95 | |
| 96 | int minijail_change_group(struct minijail *j, const char *group) { |
| 97 | /* In principle this should use getgrnam(), but: |
| 98 | * 1) getgrnam_r() isn't actually reentrant anyway, since it uses a |
| 99 | * statically-allocated file descriptor internally |
| 100 | * 2) fgetgrnam() (by analogy with fgetgrent) would solve (1) except that it |
| 101 | * doesn't exist |
| 102 | * 3) sysconf() (see getgrnam_r(3)) is allowed to return a size that is not |
| 103 | * large enough, which means having to loop on growing the buffer we pass |
| 104 | * in |
| 105 | */ |
| 106 | struct group *gr = getgrnam(group); |
| 107 | if (!gr) |
| 108 | return errno; |
| 109 | minijail_change_gid(j, gr->gr_gid); |
| 110 | return 0; |
| 111 | } |
| 112 | |
| 113 | void minijail_use_seccomp(struct minijail *j) { |
| 114 | j->flags.seccomp = 1; |
| 115 | } |
| 116 | |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 117 | void minijail_use_seccomp_filter(struct minijail *j) { |
| 118 | j->flags.seccomp_filter = 1; |
| 119 | } |
| 120 | |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 121 | void minijail_use_caps(struct minijail *j, uint64_t capmask) { |
| 122 | j->caps = capmask; |
| 123 | j->flags.caps = 1; |
| 124 | } |
| 125 | |
| 126 | void minijail_namespace_vfs(struct minijail *j) { |
| 127 | j->flags.vfs = 1; |
| 128 | } |
| 129 | |
| 130 | void minijail_namespace_pids(struct minijail *j) { |
| 131 | j->flags.pids = 1; |
| 132 | } |
| 133 | |
| 134 | void minijail_remount_readonly(struct minijail *j) { |
| 135 | j->flags.vfs = 1; |
| 136 | j->flags.readonly = 1; |
| 137 | } |
| 138 | |
| 139 | void minijail_inherit_usergroups(struct minijail *j) { |
| 140 | j->flags.usergroups = 1; |
| 141 | } |
| 142 | |
| 143 | void minijail_disable_ptrace(struct minijail *j) { |
| 144 | j->flags.ptrace = 1; |
| 145 | } |
| 146 | |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 147 | int minijail_add_seccomp_filter(struct minijail *j, int nr, |
| 148 | const char *filter) { |
| 149 | struct seccomp_filter *sf; |
| 150 | if (!filter || nr < 0) |
| 151 | return -EINVAL; |
| 152 | |
| 153 | sf = malloc(sizeof(*sf)); |
| 154 | if (!sf) |
| 155 | return -ENOMEM; |
| 156 | sf->nr = nr; |
| 157 | sf->filter = strndup(filter, MINIJAIL_MAX_SECCOMP_FILTER_LINE); |
| 158 | if (!sf->filter) { |
| 159 | free(sf); |
| 160 | return -ENOMEM; |
| 161 | } |
| 162 | |
| 163 | if (!j->filters) { |
| 164 | j->filters = sf; |
| 165 | sf->next = sf; |
| 166 | sf->prev = sf; |
| 167 | return 0; |
| 168 | } |
| 169 | sf->next = j->filters; |
| 170 | sf->prev = j->filters->prev; |
| 171 | sf->prev->next = sf; |
| 172 | j->filters->prev = sf; |
| 173 | return 0; |
| 174 | } |
| 175 | |
| 176 | int minijail_lookup_syscall(const char *name) { |
| 177 | const struct syscall_entry *entry = syscall_table; |
| 178 | for (; entry->name && entry->nr >= 0; ++entry) |
| 179 | if (!strcmp(entry->name, name)) |
| 180 | return entry->nr; |
| 181 | return -1; |
| 182 | } |
| 183 | |
| 184 | static char *strip(char *s) { |
| 185 | char *end; |
| 186 | while (*s && isblank(*s)) |
| 187 | s++; |
| 188 | end = s + strlen(s) - 1; |
| 189 | while (*end && (isblank(*end) || *end == '\n')) |
| 190 | end--; |
| 191 | *(end+1) = '\0'; |
| 192 | return s; |
| 193 | } |
| 194 | |
| 195 | void minijail_parse_seccomp_filters(struct minijail *j, const char *path) { |
| 196 | FILE *file = fopen(path, "r"); |
| 197 | char line[MINIJAIL_MAX_SECCOMP_FILTER_LINE]; |
| 198 | int count = 1; |
| 199 | if (!file) |
| 200 | pdie("failed to open seccomp filters file"); |
| 201 | |
| 202 | /* Format is simple: |
| 203 | * syscall_name<COLON><FILTER STRING>[\n|EOF] |
| 204 | * #...comment... |
| 205 | * <empty line? |
| 206 | */ |
| 207 | while (fgets(line, sizeof(line), file)) { |
| 208 | char *filter = line; |
| 209 | char *name = strsep(&filter, ":"); |
| 210 | char *name_end = NULL; |
| 211 | int nr = -1; |
| 212 | |
| 213 | if (!name) |
| 214 | die("invalid filter on line %d", count); |
| 215 | |
| 216 | name = strip(name); |
| 217 | |
| 218 | if (!filter) { |
| 219 | if (strlen(name)) |
| 220 | die("invalid filter on line %d", count); |
| 221 | /* Allow empty lines */ |
| 222 | continue; |
| 223 | } |
| 224 | |
| 225 | /* Allow comment lines */ |
| 226 | if (*name == '#') |
| 227 | continue; |
| 228 | |
| 229 | filter = strip(filter); |
| 230 | |
| 231 | /* Take direct syscall numbers */ |
| 232 | nr = strtol(name, &name_end, 0); |
| 233 | /* Or fail-over to using names */ |
| 234 | if (*name_end != '\0') |
| 235 | nr = minijail_lookup_syscall(name); |
| 236 | if (nr < 0) |
| 237 | die("syscall '%s' unknown", name); |
| 238 | |
| 239 | if (minijail_add_seccomp_filter(j, nr, filter)) |
| 240 | pdie("failed to add filter for syscall '%s'", name); |
| 241 | } |
| 242 | fclose(file); |
| 243 | } |
| 244 | |
Will Drewry | 2ddaad0 | 2011-09-16 11:36:08 -0500 | [diff] [blame] | 245 | size_t minijail_size(const struct minijail *j) { |
| 246 | size_t bytes = sizeof(*j); |
| 247 | if (j->user) |
| 248 | bytes += strlen(j->user) + 1; |
| 249 | /* TODO(wad) if (seccomp_filter) */ |
| 250 | return bytes; |
| 251 | } |
| 252 | |
Will Drewry | 2ddaad0 | 2011-09-16 11:36:08 -0500 | [diff] [blame] | 253 | int minijail_marshal(const struct minijail *j, char *buf, size_t available) { |
| 254 | size_t total = sizeof(*j); |
| 255 | if (available < total) |
| 256 | return -ENOSPC; |
| 257 | available -= total; |
| 258 | memcpy(buf, (void *) j, sizeof(*j)); |
| 259 | if (j->user) { |
| 260 | size_t len = strlen(j->user) + 1; |
| 261 | if (available < len) |
| 262 | return -ENOSPC; |
| 263 | memcpy(buf + total, j->user, len); |
| 264 | available -= len; |
| 265 | total += len; |
| 266 | } |
| 267 | return 0; |
| 268 | } |
| 269 | |
| 270 | int minijail_unmarshal(struct minijail *j, char *serialized, size_t length) { |
| 271 | if (length < sizeof(*j)) |
| 272 | return -EINVAL; |
| 273 | memcpy((void *) j, serialized, sizeof(*j)); |
| 274 | serialized += sizeof(*j); |
| 275 | length -= sizeof(*j); |
| 276 | if (j->user) { /* stale pointer */ |
| 277 | if (!length) |
| 278 | return -EINVAL; |
| 279 | j->user = strndup(serialized, length); |
| 280 | length -= strlen(j->user) + 1; |
| 281 | } |
| 282 | return 0; |
| 283 | } |
| 284 | |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 285 | void minijail_preenter(struct minijail *j) { |
| 286 | /* Strip out options which are minijail_run() only. */ |
| 287 | j->flags.vfs = 0; |
| 288 | j->flags.readonly = 0; |
| 289 | j->flags.pids = 0; |
| 290 | } |
| 291 | |
| 292 | void minijail_preexec(struct minijail *j) { |
| 293 | int vfs = j->flags.vfs; |
| 294 | int readonly = j->flags.readonly; |
Will Drewry | 2ddaad0 | 2011-09-16 11:36:08 -0500 | [diff] [blame] | 295 | if (j->user) |
| 296 | free(j->user); |
| 297 | j->user = NULL; |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 298 | |
| 299 | memset(&j->flags, 0, sizeof(j->flags)); |
| 300 | /* Now restore anything we meant to keep. */ |
| 301 | j->flags.vfs = vfs; |
| 302 | j->flags.readonly = readonly; |
| 303 | /* Note, pidns will already have been used before this call. */ |
Will Drewry | 2ddaad0 | 2011-09-16 11:36:08 -0500 | [diff] [blame] | 304 | } |
| 305 | |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 306 | static int remount_readonly(void) { |
| 307 | const char *kProcPath = "/proc"; |
| 308 | const unsigned int kSafeFlags = MS_NODEV | MS_NOEXEC | MS_NOSUID; |
| 309 | /* Right now, we're holding a reference to our parent's old mount of /proc in |
| 310 | * our namespace, which means using MS_REMOUNT here would mutate our parent's |
| 311 | * mount as well, even though we're in a VFS namespace (!). Instead, remove |
| 312 | * their mount from our namespace and make our own. */ |
| 313 | if (umount(kProcPath)) |
| 314 | return errno; |
| 315 | if (mount("", kProcPath, "proc", kSafeFlags | MS_RDONLY, "")) |
| 316 | return errno; |
| 317 | return 0; |
| 318 | } |
| 319 | |
| 320 | static void drop_caps(const struct minijail *j) { |
| 321 | cap_t caps = cap_get_proc(); |
| 322 | cap_value_t raise_flag[1]; |
| 323 | unsigned int i; |
| 324 | if (!caps) |
| 325 | die("can't get process caps"); |
| 326 | if (cap_clear_flag(caps, CAP_INHERITABLE)) |
| 327 | die("can't clear inheritable caps"); |
| 328 | if (cap_clear_flag(caps, CAP_EFFECTIVE)) |
| 329 | die("can't clear effective caps"); |
| 330 | if (cap_clear_flag(caps, CAP_PERMITTED)) |
| 331 | die("can't clear permitted caps"); |
| 332 | for (i = 0; i < sizeof(j->caps) * 8 && cap_valid((int)i); ++i) { |
| 333 | if (i != CAP_SETPCAP && !(j->caps & (1 << i))) |
| 334 | continue; |
| 335 | raise_flag[0] = i; |
| 336 | if (cap_set_flag(caps, CAP_EFFECTIVE, 1, raise_flag, CAP_SET)) |
| 337 | die("can't add effective cap"); |
| 338 | if (cap_set_flag(caps, CAP_PERMITTED, 1, raise_flag, CAP_SET)) |
| 339 | die("can't add permitted cap"); |
| 340 | if (cap_set_flag(caps, CAP_INHERITABLE, 1, raise_flag, CAP_SET)) |
| 341 | die("can't add inheritable cap"); |
| 342 | } |
| 343 | if (cap_set_proc(caps)) |
| 344 | die("can't apply cleaned capset"); |
| 345 | cap_free(caps); |
| 346 | for (i = 0; i < sizeof(j->caps) * 8 && cap_valid((int)i); ++i) { |
| 347 | if (j->caps & (1 << i)) |
| 348 | continue; |
| 349 | if (prctl(PR_CAPBSET_DROP, i)) |
| 350 | pdie("prctl(PR_CAPBSET_DROP)"); |
| 351 | } |
| 352 | } |
| 353 | |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 354 | static int setup_seccomp_filters(const struct minijail *j) { |
| 355 | const struct seccomp_filter *sf = j->filters; |
| 356 | int ret = 0; |
| 357 | int broaden = 0; |
| 358 | |
| 359 | /* No filters installed isn't necessarily an error. */ |
| 360 | if (!sf) |
| 361 | return ret; |
| 362 | |
| 363 | do { |
| 364 | errno = 0; |
| 365 | ret = prctl(PR_SET_SECCOMP_FILTER, PR_SECCOMP_FILTER_SYSCALL, |
| 366 | sf->nr, broaden ? "1" : sf->filter); |
| 367 | if (ret) { |
| 368 | switch (errno) { |
| 369 | case ENOSYS: |
| 370 | /* TODO(wad) make this a config option */ |
| 371 | if (broaden) |
| 372 | die("CONFIG_SECCOMP_FILTER is not supported by your kernel"); |
| 373 | warn("missing CONFIG_FTRACE_SYSCALLS; relaxing the filter for %d", |
| 374 | sf->nr); |
| 375 | broaden = 1; |
| 376 | continue; |
| 377 | case E2BIG: |
| 378 | warn("seccomp filter too long: %d", sf->nr); |
| 379 | pdie("filter too long"); |
| 380 | case ENOSPC: |
| 381 | pdie("too many seccomp filters"); |
| 382 | case EPERM: |
| 383 | warn("syscall filter disallowed for %d", sf->nr); |
| 384 | pdie("failed to install seccomp filter"); |
| 385 | case EINVAL: |
| 386 | warn("seccomp filter or call method is invalid. %d:'%s'", |
| 387 | sf->nr, sf->filter); |
| 388 | default: |
| 389 | pdie("failed to install seccomp filter"); |
| 390 | } |
| 391 | } |
| 392 | sf = sf->next; |
| 393 | broaden = 0; |
| 394 | } while (sf != j->filters); |
| 395 | return ret; |
| 396 | } |
| 397 | |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 398 | void minijail_enter(const struct minijail *j) { |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 399 | int ret; |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 400 | if (j->flags.pids) |
| 401 | die("tried to enter a pid-namespaced jail; try minijail_run()?"); |
| 402 | |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 403 | ret = setup_seccomp_filters(j); |
| 404 | if (j->flags.seccomp_filter && ret) |
| 405 | die("failed to configure seccomp filters"); |
| 406 | |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 407 | if (j->flags.usergroups && !j->user) |
| 408 | die("usergroup inheritance without username"); |
| 409 | |
| 410 | /* We can't recover from failures if we've dropped privileges partially, |
| 411 | * so we don't even try. If any of our operations fail, we abort() the |
| 412 | * entire process. */ |
| 413 | if (j->flags.vfs && unshare(CLONE_NEWNS)) |
| 414 | pdie("unshare"); |
| 415 | |
| 416 | if (j->flags.readonly && remount_readonly()) |
| 417 | pdie("remount"); |
| 418 | |
| 419 | if (j->flags.caps) { |
| 420 | /* POSIX capabilities are a bit tricky. If we drop our capability to change |
| 421 | * uids, our attempt to use setuid() below will fail. Hang on to root caps |
| 422 | * across setuid(), then lock securebits. */ |
| 423 | if (prctl(PR_SET_KEEPCAPS, 1)) |
| 424 | pdie("prctl(PR_SET_KEEPCAPS)"); |
| 425 | if (prctl(PR_SET_SECUREBITS, SECURE_ALL_BITS | SECURE_ALL_LOCKS)) |
| 426 | pdie("prctl(PR_SET_SECUREBITS)"); |
| 427 | } |
| 428 | |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 429 | if (j->flags.usergroups && initgroups(j->user, j->usergid)) { |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 430 | pdie("initgroups"); |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 431 | } else if (!j->flags.usergroups && setgroups(0, NULL)) { |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 432 | pdie("setgroups"); |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 433 | } |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 434 | |
| 435 | if (j->flags.gid && setresgid(j->gid, j->gid, j->gid)) |
| 436 | pdie("setresgid"); |
| 437 | |
| 438 | if (j->flags.uid && setresuid(j->uid, j->uid, j->uid)) |
| 439 | pdie("setresuid"); |
| 440 | |
| 441 | if (j->flags.caps) |
| 442 | drop_caps(j); |
| 443 | |
| 444 | /* seccomp has to come last since it cuts off all the other |
| 445 | * privilege-dropping syscalls :) */ |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 446 | if (j->flags.seccomp_filter && prctl(PR_SET_SECCOMP, 13)) |
| 447 | pdie("prctl(PR_SET_SECCOMP, 13)"); |
| 448 | |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 449 | if (j->flags.seccomp && prctl(PR_SET_SECCOMP, 1)) |
| 450 | pdie("prctl(PR_SET_SECCOMP)"); |
| 451 | } |
| 452 | |
| 453 | static int init_exitstatus = 0; |
| 454 | |
| 455 | static void init_term(int __attribute__((unused)) sig) { |
| 456 | _exit(init_exitstatus); |
| 457 | } |
| 458 | |
| 459 | static int init(pid_t rootpid) { |
| 460 | pid_t pid; |
| 461 | int status; |
| 462 | signal(SIGTERM, init_term); /* so that we exit with the right status */ |
| 463 | while ((pid = wait(&status)) > 0) { |
| 464 | /* This loop will only end when either there are no processes left inside |
| 465 | * our pid namespace or we get a signal. */ |
| 466 | if (pid == rootpid) |
| 467 | init_exitstatus = status; |
| 468 | } |
| 469 | if (!WIFEXITED(init_exitstatus)) |
| 470 | _exit(MINIJAIL_ERR_INIT); |
| 471 | _exit(WEXITSTATUS(init_exitstatus)); |
| 472 | } |
| 473 | |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 474 | int minijail_from_fd(int fd, struct minijail *j) { |
| 475 | size_t sz = 0; |
| 476 | size_t bytes = read(fd, &sz, sizeof(sz)); |
| 477 | char *buf; |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 478 | int r; |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 479 | if (sizeof(sz) != bytes) |
| 480 | return -EINVAL; |
| 481 | if (sz > USHRT_MAX) /* Arbitrary sanity check */ |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 482 | return -E2BIG; |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 483 | buf = malloc(sz); |
| 484 | if (!buf) |
| 485 | return -ENOMEM; |
| 486 | bytes = read(fd, buf, sz); |
| 487 | if (bytes != sz) { |
| 488 | free(buf); |
| 489 | return -EINVAL; |
| 490 | } |
| 491 | r = minijail_unmarshal(j, buf, sz); |
| 492 | free(buf); |
| 493 | return r; |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 494 | } |
| 495 | |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 496 | int minijail_to_fd(struct minijail *j, int fd) { |
| 497 | char *buf; |
| 498 | size_t sz = minijail_size(j); |
| 499 | ssize_t written; |
| 500 | int r; |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 501 | |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 502 | if (j->flags.seccomp_filter) |
| 503 | warn("TODO(wad) seccomp_filter is installed in the parent which " |
| 504 | "requires overly permissive rules for execve(2)ing."); |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 505 | if (!sz) |
| 506 | return -EINVAL; |
| 507 | buf = malloc(sz); |
| 508 | if ((r = minijail_marshal(j, buf, sz))) { |
| 509 | free(buf); |
| 510 | return r; |
| 511 | } |
| 512 | /* Sends [size][minijail]. */ |
| 513 | written = write(fd, &sz, sizeof(sz)); |
| 514 | if (written != sizeof(sz)) { |
| 515 | free(buf); |
| 516 | return -EFAULT; |
| 517 | } |
| 518 | written = write(fd, buf, sz); |
| 519 | if (written < 0 || (size_t) written != sz) { |
| 520 | free(buf); |
| 521 | return -EFAULT; |
| 522 | } |
| 523 | free(buf); |
| 524 | return 0; |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 525 | } |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 526 | |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 527 | static int setup_preload(void) { |
| 528 | char *oldenv = getenv(kLdPreloadEnvVar) ? : ""; |
| 529 | char *newenv = malloc(strlen(oldenv) + 2 + strlen(PRELOADPATH)); |
| 530 | if (!newenv) |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 531 | return -ENOMEM; |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 532 | |
| 533 | /* Only insert a separating space if we have something to separate... */ |
| 534 | sprintf(newenv, "%s%s%s", oldenv, strlen(oldenv) ? " " : "", PRELOADPATH); |
| 535 | |
| 536 | /* setenv() makes a copy of the string we give it */ |
Ben Chan | 541c7e5 | 2011-08-26 14:55:53 -0700 | [diff] [blame] | 537 | setenv(kLdPreloadEnvVar, newenv, 1); |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 538 | free(newenv); |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 539 | return 0; |
| 540 | } |
| 541 | |
| 542 | int minijail_run(struct minijail *j, const char *filename, char *const argv[]) { |
| 543 | unsigned int pidns = j->flags.pids ? CLONE_NEWPID : 0; |
Ben Chan | 541c7e5 | 2011-08-26 14:55:53 -0700 | [diff] [blame] | 544 | char *oldenv, *oldenv_copy = NULL; |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 545 | pid_t r; |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 546 | int pipe_fds[2]; |
| 547 | char fd_buf[11]; |
Ben Chan | 541c7e5 | 2011-08-26 14:55:53 -0700 | [diff] [blame] | 548 | |
| 549 | oldenv = getenv(kLdPreloadEnvVar); |
| 550 | if (oldenv) { |
| 551 | oldenv_copy = strdup(oldenv); |
| 552 | if (!oldenv_copy) |
| 553 | return -ENOMEM; |
| 554 | } |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 555 | r = setup_preload(); |
| 556 | if (r) |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 557 | return r; |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 558 | |
| 559 | /* Before we fork(2) and execve(2) the child process, we need to open |
| 560 | * a pipe(2) to send the minijail configuration over. |
| 561 | */ |
| 562 | r = pipe(pipe_fds); |
| 563 | if (r) |
| 564 | return r; |
| 565 | r = snprintf(fd_buf, sizeof(fd_buf), "%d", pipe_fds[0]); |
| 566 | if (r <= 0) |
| 567 | return -EINVAL; |
| 568 | setenv(kFdEnvVar, fd_buf, 1); |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 569 | |
| 570 | r = syscall(SYS_clone, pidns | SIGCHLD, NULL); |
| 571 | if (r > 0) { |
Ben Chan | 541c7e5 | 2011-08-26 14:55:53 -0700 | [diff] [blame] | 572 | if (oldenv_copy) { |
| 573 | setenv(kLdPreloadEnvVar, oldenv_copy, 1); |
| 574 | free(oldenv_copy); |
| 575 | } else { |
| 576 | unsetenv(kLdPreloadEnvVar); |
| 577 | } |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 578 | unsetenv(kFdEnvVar); |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 579 | j->initpid = r; |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 580 | close(pipe_fds[0]); |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 581 | r = minijail_to_fd(j, pipe_fds[1]); |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 582 | close(pipe_fds[1]); |
| 583 | if (r) { |
| 584 | kill(j->initpid, SIGKILL); |
| 585 | die("failed to send marshalled minijail"); |
| 586 | } |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 587 | return 0; |
| 588 | } |
Ben Chan | 541c7e5 | 2011-08-26 14:55:53 -0700 | [diff] [blame] | 589 | |
| 590 | free(oldenv_copy); |
| 591 | |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 592 | if (r < 0) |
| 593 | return r; |
| 594 | |
Will Drewry | fe4a372 | 2011-09-16 14:50:50 -0500 | [diff] [blame^] | 595 | /* Drop everything that cannot be inherited across execve. */ |
| 596 | minijail_preexec(j); |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 597 | |
| 598 | /* Jail this process and its descendants... */ |
| 599 | minijail_enter(j); |
| 600 | |
| 601 | if (pidns) { |
| 602 | /* pid namespace: this process will become init inside the new namespace, so |
| 603 | * fork off a child to actually run the program (we don't want all programs |
| 604 | * we might exec to have to know how to be init). */ |
| 605 | r = fork(); |
| 606 | if (r < 0) |
| 607 | _exit(r); |
| 608 | else if (r > 0) |
| 609 | init(r); /* never returns */ |
| 610 | } |
| 611 | |
Will Drewry | 2f54b6a | 2011-09-16 13:45:31 -0500 | [diff] [blame] | 612 | |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 613 | /* If we aren't pid-namespaced: |
| 614 | * calling process |
| 615 | * -> execve()-ing process |
| 616 | * If we are: |
| 617 | * calling process |
| 618 | * -> init()-ing process |
| 619 | * -> execve()-ing process |
| 620 | */ |
| 621 | _exit(execve(filename, argv, environ)); |
| 622 | } |
| 623 | |
| 624 | int minijail_kill(struct minijail *j) { |
| 625 | int st; |
| 626 | if (kill(j->initpid, SIGTERM)) |
| 627 | return errno; |
| 628 | if (waitpid(j->initpid, &st, 0) < 0) |
| 629 | return errno; |
| 630 | return st; |
| 631 | } |
| 632 | |
| 633 | int minijail_wait(struct minijail *j) { |
| 634 | int st; |
| 635 | if (waitpid(j->initpid, &st, 0) < 0) |
| 636 | return errno; |
| 637 | if (!WIFEXITED(st)) |
| 638 | return MINIJAIL_ERR_JAIL; |
| 639 | return WEXITSTATUS(st); |
| 640 | } |
| 641 | |
| 642 | void minijail_destroy(struct minijail *j) { |
Will Drewry | 32ac9f5 | 2011-08-18 21:36:27 -0500 | [diff] [blame] | 643 | struct seccomp_filter *f = j->filters; |
| 644 | /* Unlink the tail and head */ |
| 645 | if (f) |
| 646 | f->prev->next = NULL; |
| 647 | while (f) { |
| 648 | struct seccomp_filter *next = f->next; |
| 649 | free(f->filter); |
| 650 | free(f); |
| 651 | f = next; |
| 652 | } |
Will Drewry | 2ddaad0 | 2011-09-16 11:36:08 -0500 | [diff] [blame] | 653 | if (j->user) |
| 654 | free(j->user); |
Elly Jones | cd7a904 | 2011-07-22 13:56:51 -0400 | [diff] [blame] | 655 | free(j); |
| 656 | } |