sys-utils/unshare.c

   1 /*
   2  * unshare(1) - command-line interface for unshare(2)
   3  *
   4  * Copyright (C) 2009 Mikhail Gusarov <dottedmag@dottedmag.net>
   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; either version 2, or (at your option) any
   9  * later version.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20
  21 #include <errno.h>
  22 #include <getopt.h>
  23 #include <sched.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <unistd.h>
  27 #include <sys/wait.h>
  28 #include <sys/mount.h>
  29 #include <sys/types.h>
  30 #include <sys/stat.h>
  31 #include <sys/prctl.h>
  32 #include <grp.h>
  33
  34 /* we only need some defines missing in sys/mount.h, no libmount linkage */
  35 #include <libmount.h>
  36
  37 #include "nls.h"
  38 #include "c.h"
  39 #include "caputils.h"
  40 #include "closestream.h"
  41 #include "namespace.h"
  42 #include "exec_shell.h"
  43 #include "xalloc.h"
  44 #include "pathnames.h"
  45 #include "all-io.h"
  46 #include "signames.h"
  47 #include "strutils.h"
  48
  49 /* synchronize parent and child by pipe */
  50 #define PIPE_SYNC_BYTE  0x06
  51
  52 /* 'private' is kernel default */
  53 #define UNSHARE_PROPAGATION_DEFAULT     (MS_REC | MS_PRIVATE)
  54
  55 /* /proc namespace files and mountpoints for binds */
  56 static struct namespace_file {
  57         int             type;           /* CLONE_NEW* */
  58         const char      *name;          /* ns/<type> */
  59         const char      *target;        /* user specified target for bind mount */
  60 } namespace_files[] = {
  61         { .type = CLONE_NEWUSER,  .name = "ns/user" },
  62         { .type = CLONE_NEWCGROUP,.name = "ns/cgroup" },
  63         { .type = CLONE_NEWIPC,   .name = "ns/ipc"  },
  64         { .type = CLONE_NEWUTS,   .name = "ns/uts"  },
  65         { .type = CLONE_NEWNET,   .name = "ns/net"  },
  66         { .type = CLONE_NEWPID,   .name = "ns/pid"  },
  67         { .type = CLONE_NEWNS,    .name = "ns/mnt"  },
  68         { .type = CLONE_NEWTIME,  .name = "ns/time"  },
  69         { .name = NULL }
  70 };
  71
  72 static int npersists;   /* number of persistent namespaces */
  73
  74 enum {
  75         SETGROUPS_NONE = -1,
  76         SETGROUPS_DENY = 0,
  77         SETGROUPS_ALLOW = 1,
  78 };
  79
  80 static const char *setgroups_strings[] =
  81 {
  82         [SETGROUPS_DENY] = "deny",
  83         [SETGROUPS_ALLOW] = "allow"
  84 };
  85
  86 static int setgroups_str2id(const char *str)
  87 {
  88         size_t i;
  89
  90         for (i = 0; i < ARRAY_SIZE(setgroups_strings); i++)
  91                 if (strcmp(str, setgroups_strings[i]) == 0)
  92                         return i;
  93
  94         errx(EXIT_FAILURE, _("unsupported --setgroups argument '%s'"), str);
  95 }
  96
  97 static void setgroups_control(int action)
  98 {
  99         const char *file = _PATH_PROC_SETGROUPS;
 100         const char *cmd;
 101         int fd;
 102
 103         if (action < 0 || (size_t) action >= ARRAY_SIZE(setgroups_strings))
 104                 return;
 105         cmd = setgroups_strings[action];
 106
 107         fd = open(file, O_WRONLY);
 108         if (fd < 0) {
 109                 if (errno == ENOENT)
 110                         return;
 111                 err(EXIT_FAILURE, _("cannot open %s"), file);
 112         }
 113
 114         if (write_all(fd, cmd, strlen(cmd)))
 115                 err(EXIT_FAILURE, _("write failed %s"), file);
 116         close(fd);
 117 }
 118
 119 static void map_id(const char *file, uint32_t from, uint32_t to)
 120 {
 121         char *buf;
 122         int fd;
 123
 124         fd = open(file, O_WRONLY);
 125         if (fd < 0)
 126                  err(EXIT_FAILURE, _("cannot open %s"), file);
 127
 128         xasprintf(&buf, "%u %u 1", from, to);
 129         if (write_all(fd, buf, strlen(buf)))
 130                 err(EXIT_FAILURE, _("write failed %s"), file);
 131         free(buf);
 132         close(fd);
 133 }
 134
 135 static unsigned long parse_propagation(const char *str)
 136 {
 137         size_t i;
 138         static const struct prop_opts {
 139                 const char *name;
 140                 unsigned long flag;
 141         } opts[] = {
 142                 { "slave",      MS_REC | MS_SLAVE },
 143                 { "private",    MS_REC | MS_PRIVATE },
 144                 { "shared",     MS_REC | MS_SHARED },
 145                 { "unchanged",        0 }
 146         };
 147
 148         for (i = 0; i < ARRAY_SIZE(opts); i++) {
 149                 if (strcmp(opts[i].name, str) == 0)
 150                         return opts[i].flag;
 151         }
 152
 153         errx(EXIT_FAILURE, _("unsupported propagation mode: %s"), str);
 154 }
 155
 156 static void set_propagation(unsigned long flags)
 157 {
 158         if (flags == 0)
 159                 return;
 160
 161         if (mount("none", "/", NULL, flags, NULL) != 0)
 162                 err(EXIT_FAILURE, _("cannot change root filesystem propagation"));
 163 }
 164
 165
 166 static int set_ns_target(int type, const char *path)
 167 {
 168         struct namespace_file *ns;
 169
 170         for (ns = namespace_files; ns->name; ns++) {
 171                 if (ns->type != type)
 172                         continue;
 173                 ns->target = path;
 174                 npersists++;
 175                 return 0;
 176         }
 177
 178         return -EINVAL;
 179 }
 180
 181 static int bind_ns_files(pid_t pid)
 182 {
 183         struct namespace_file *ns;
 184         char src[PATH_MAX];
 185
 186         for (ns = namespace_files; ns->name; ns++) {
 187                 if (!ns->target)
 188                         continue;
 189
 190                 snprintf(src, sizeof(src), "/proc/%u/%s", (unsigned) pid, ns->name);
 191
 192                 if (mount(src, ns->target, NULL, MS_BIND, NULL) != 0)
 193                         err(EXIT_FAILURE, _("mount %s on %s failed"), src, ns->target);
 194         }
 195
 196         return 0;
 197 }
 198
 199 static ino_t get_mnt_ino(pid_t pid)
 200 {
 201         struct stat st;
 202         char path[PATH_MAX];
 203
 204         snprintf(path, sizeof(path), "/proc/%u/ns/mnt", (unsigned) pid);
 205
 206         if (stat(path, &st) != 0)
 207                 err(EXIT_FAILURE, _("cannot stat %s"), path);
 208         return st.st_ino;
 209 }
 210
 211 static void settime(time_t offset, clockid_t clk_id)
 212 {
 213         char buf[sizeof(stringify_value(ULONG_MAX)) * 3];
 214         int fd, len;
 215
 216         len = snprintf(buf, sizeof(buf), "%d %ld 0", clk_id, offset);
 217
 218         fd = open("/proc/self/timens_offsets", O_WRONLY);
 219         if (fd < 0)
 220                 err(EXIT_FAILURE, _("failed to open /proc/self/timens_offsets"));
 221
 222         if (write(fd, buf, len) != len)
 223                 err(EXIT_FAILURE, _("failed to write to /proc/self/timens_offsets"));
 224
 225         close(fd);
 226 }
 227
 228 static void bind_ns_files_from_child(pid_t *child, int fds[2])
 229 {
 230         char ch;
 231         pid_t ppid = getpid();
 232         ino_t ino = get_mnt_ino(ppid);
 233
 234         if (pipe(fds) < 0)
 235                 err(EXIT_FAILURE, _("pipe failed"));
 236
 237         *child = fork();
 238
 239         switch (*child) {
 240         case -1:
 241                 err(EXIT_FAILURE, _("fork failed"));
 242
 243         case 0: /* child */
 244                 close(fds[1]);
 245                 fds[1] = -1;
 246
 247                 /* wait for parent */
 248                 if (read_all(fds[0], &ch, 1) != 1 && ch != PIPE_SYNC_BYTE)
 249                         err(EXIT_FAILURE, _("failed to read pipe"));
 250                 if (get_mnt_ino(ppid) == ino)
 251                         exit(EXIT_FAILURE);
 252                 bind_ns_files(ppid);
 253                 exit(EXIT_SUCCESS);
 254                 break;
 255
 256         default: /* parent */
 257                 close(fds[0]);
 258                 fds[0] = -1;
 259                 break;
 260         }
 261 }
 262
 263 static void __attribute__((__noreturn__)) usage(void)
 264 {
 265         FILE *out = stdout;
 266
 267         fputs(USAGE_HEADER, out);
 268         fprintf(out, _(" %s [options] [<program> [<argument>...]]\n"),
 269                 program_invocation_short_name);
 270
 271         fputs(USAGE_SEPARATOR, out);
 272         fputs(_("Run a program with some namespaces unshared from the parent.\n"), out);
 273
 274         fputs(USAGE_OPTIONS, out);
 275         fputs(_(" -m, --mount[=<file>]      unshare mounts namespace\n"), out);
 276         fputs(_(" -u, --uts[=<file>]        unshare UTS namespace (hostname etc)\n"), out);
 277         fputs(_(" -i, --ipc[=<file>]        unshare System V IPC namespace\n"), out);
 278         fputs(_(" -n, --net[=<file>]        unshare network namespace\n"), out);
 279         fputs(_(" -p, --pid[=<file>]        unshare pid namespace\n"), out);
 280         fputs(_(" -U, --user[=<file>]       unshare user namespace\n"), out);
 281         fputs(_(" -C, --cgroup[=<file>]     unshare cgroup namespace\n"), out);
 282         fputs(_(" -T, --time[=<file>]       unshare time namespace\n"), out);
 283         fputs(USAGE_SEPARATOR, out);
 284         fputs(_(" -f, --fork                fork before launching <program>\n"), out);
 285         fputs(_(" --map-user=<uid>          map current user to uid (implies --user)\n"), out);
 286         fputs(_(" --map-group=<gid>         map current group to gid (implies --user)\n"), out);
 287         fputs(_(" -r, --map-root-user       map current user to root (implies --user)\n"), out);
 288         fputs(_(" -c, --map-current-user    map current user to itself (implies --user)\n"), out);
 289         fputs(USAGE_SEPARATOR, out);
 290         fputs(_(" --kill-child[=<signame>]  when dying, kill the forked child (implies --fork)\n"
 291                 "                             defaults to SIGKILL\n"), out);
 292         fputs(_(" --mount-proc[=<dir>]      mount proc filesystem first (implies --mount)\n"), out);
 293         fputs(_(" --propagation slave|shared|private|unchanged\n"
 294                 "                           modify mount propagation in mount namespace\n"), out);
 295         fputs(_(" --setgroups allow|deny    control the setgroups syscall in user namespaces\n"), out);
 296         fputs(_(" --keep-caps               retain capabilities granted in user namespaces\n"), out);
 297         fputs(USAGE_SEPARATOR, out);
 298         fputs(_(" -R, --root=<dir>          run the command with root directory set to <dir>\n"), out);
 299         fputs(_(" -w, --wd=<dir>            change working directory to <dir>\n"), out);
 300         fputs(_(" -S, --setuid <uid>        set uid in entered namespace\n"), out);
 301         fputs(_(" -G, --setgid <gid>        set gid in entered namespace\n"), out);
 302         fputs(_(" --monotonic <offset>      set clock monotonic offset (seconds) in time namespaces\n"), out);
 303         fputs(_(" --boottime <offset>       set clock boottime offset (seconds) in time namespaces\n"), out);
 304
 305         fputs(USAGE_SEPARATOR, out);
 306         printf(USAGE_HELP_OPTIONS(27));
 307         printf(USAGE_MAN_TAIL("unshare(1)"));
 308
 309         exit(EXIT_SUCCESS);
 310 }
 311
 312 int main(int argc, char *argv[])
 313 {
 314         enum {
 315                 OPT_MOUNTPROC = CHAR_MAX + 1,
 316                 OPT_PROPAGATION,
 317                 OPT_SETGROUPS,
 318                 OPT_KILLCHILD,
 319                 OPT_KEEPCAPS,
 320                 OPT_MONOTONIC,
 321                 OPT_BOOTTIME,
 322                 OPT_MAPUSER,
 323                 OPT_MAPGROUP,
 324         };
 325         static const struct option longopts[] = {
 326                 { "help",          no_argument,       NULL, 'h'             },
 327                 { "version",       no_argument,       NULL, 'V'             },
 328
 329                 { "mount",         optional_argument, NULL, 'm'             },
 330                 { "uts",           optional_argument, NULL, 'u'             },
 331                 { "ipc",           optional_argument, NULL, 'i'             },
 332                 { "net",           optional_argument, NULL, 'n'             },
 333                 { "pid",           optional_argument, NULL, 'p'             },
 334                 { "user",          optional_argument, NULL, 'U'             },
 335                 { "cgroup",        optional_argument, NULL, 'C'             },
 336                 { "time",          optional_argument, NULL, 'T'             },
 337
 338                 { "fork",          no_argument,       NULL, 'f'             },
 339                 { "kill-child",    optional_argument, NULL, OPT_KILLCHILD   },
 340                 { "mount-proc",    optional_argument, NULL, OPT_MOUNTPROC   },
 341                 { "map-user",      required_argument, NULL, OPT_MAPUSER     },
 342                 { "map-group",     required_argument, NULL, OPT_MAPGROUP    },
 343                 { "map-root-user", no_argument,       NULL, 'r'             },
 344                 { "map-current-user", no_argument,    NULL, 'c'             },
 345                 { "propagation",   required_argument, NULL, OPT_PROPAGATION },
 346                 { "setgroups",     required_argument, NULL, OPT_SETGROUPS   },
 347                 { "keep-caps",     no_argument,       NULL, OPT_KEEPCAPS    },
 348                 { "setuid",        required_argument, NULL, 'S'             },
 349                 { "setgid",        required_argument, NULL, 'G'             },
 350                 { "root",          required_argument, NULL, 'R'             },
 351                 { "wd",            required_argument, NULL, 'w'             },
 352                 { "monotonic",     required_argument, NULL, OPT_MONOTONIC   },
 353                 { "boottime",      required_argument, NULL, OPT_BOOTTIME    },
 354                 { NULL, 0, NULL, 0 }
 355         };
 356
 357         int setgrpcmd = SETGROUPS_NONE;
 358         int unshare_flags = 0;
 359         int c, forkit = 0;
 360         uid_t mapuser = -1;
 361         gid_t mapgroup = -1;
 362         int kill_child_signo = 0; /* 0 means --kill-child was not used */
 363         const char *procmnt = NULL;
 364         const char *newroot = NULL;
 365         const char *newdir = NULL;
 366         pid_t pid = 0;
 367         int fds[2];
 368         int status;
 369         unsigned long propagation = UNSHARE_PROPAGATION_DEFAULT;
 370         int force_uid = 0, force_gid = 0;
 371         uid_t uid = 0, real_euid = geteuid();
 372         gid_t gid = 0, real_egid = getegid();
 373         int keepcaps = 0;
 374         time_t monotonic = 0;
 375         time_t boottime = 0;
 376         int force_monotonic = 0;
 377         int force_boottime = 0;
 378
 379         setlocale(LC_ALL, "");
 380         bindtextdomain(PACKAGE, LOCALEDIR);
 381         textdomain(PACKAGE);
 382         close_stdout_atexit();
 383
 384         while ((c = getopt_long(argc, argv, "+fhVmuinpCTUrR:w:S:G:c", longopts, NULL)) != -1) {
 385                 switch (c) {
 386                 case 'f':
 387                         forkit = 1;
 388                         break;
 389                 case 'm':
 390                         unshare_flags |= CLONE_NEWNS;
 391                         if (optarg)
 392                                 set_ns_target(CLONE_NEWNS, optarg);
 393                         break;
 394                 case 'u':
 395                         unshare_flags |= CLONE_NEWUTS;
 396                         if (optarg)
 397                                 set_ns_target(CLONE_NEWUTS, optarg);
 398                         break;
 399                 case 'i':
 400                         unshare_flags |= CLONE_NEWIPC;
 401                         if (optarg)
 402                                 set_ns_target(CLONE_NEWIPC, optarg);
 403                         break;
 404                 case 'n':
 405                         unshare_flags |= CLONE_NEWNET;
 406                         if (optarg)
 407                                 set_ns_target(CLONE_NEWNET, optarg);
 408                         break;
 409                 case 'p':
 410                         unshare_flags |= CLONE_NEWPID;
 411                         if (optarg)
 412                                 set_ns_target(CLONE_NEWPID, optarg);
 413                         break;
 414                 case 'U':
 415                         unshare_flags |= CLONE_NEWUSER;
 416                         if (optarg)
 417                                 set_ns_target(CLONE_NEWUSER, optarg);
 418                         break;
 419                 case 'C':
 420                         unshare_flags |= CLONE_NEWCGROUP;
 421                         if (optarg)
 422                                 set_ns_target(CLONE_NEWCGROUP, optarg);
 423                         break;
 424                 case 'T':
 425                         unshare_flags |= CLONE_NEWTIME;
 426                         if (optarg)
 427                                 set_ns_target(CLONE_NEWTIME, optarg);
 428                         break;
 429                 case OPT_MOUNTPROC:
 430                         unshare_flags |= CLONE_NEWNS;
 431                         procmnt = optarg ? optarg : "/proc";
 432                         break;
 433                 case OPT_MAPUSER:
 434                         unshare_flags |= CLONE_NEWUSER;
 435                         mapuser = strtoul_or_err(optarg, _("failed to parse uid"));
 436                         break;
 437                 case OPT_MAPGROUP:
 438                         unshare_flags |= CLONE_NEWUSER;
 439                         mapgroup = strtoul_or_err(optarg, _("failed to parse gid"));
 440                         break;
 441                 case 'r':
 442                         unshare_flags |= CLONE_NEWUSER;
 443                         mapuser = 0;
 444                         mapgroup = 0;
 445                         break;
 446                 case 'c':
 447                         unshare_flags |= CLONE_NEWUSER;
 448                         mapuser = real_euid;
 449                         mapgroup = real_egid;
 450                         break;
 451                 case OPT_SETGROUPS:
 452                         setgrpcmd = setgroups_str2id(optarg);
 453                         break;
 454                 case OPT_PROPAGATION:
 455                         propagation = parse_propagation(optarg);
 456                         break;
 457                 case OPT_KILLCHILD:
 458                         forkit = 1;
 459                         if (optarg) {
 460                                 if ((kill_child_signo = signame_to_signum(optarg)) < 0)
 461                                         errx(EXIT_FAILURE, _("unknown signal: %s"),
 462                                              optarg);
 463                         } else {
 464                                 kill_child_signo = SIGKILL;
 465                         }
 466                         break;
 467                 case OPT_KEEPCAPS:
 468                         keepcaps = 1;
 469                         cap_last_cap(); /* Force last cap to be cached before we fork. */
 470                         break;
 471                 case 'S':
 472                         uid = strtoul_or_err(optarg, _("failed to parse uid"));
 473                         force_uid = 1;
 474                         break;
 475                 case 'G':
 476                         gid = strtoul_or_err(optarg, _("failed to parse gid"));
 477                         force_gid = 1;
 478                         break;
 479                 case 'R':
 480                         newroot = optarg;
 481                         break;
 482                 case 'w':
 483                         newdir = optarg;
 484                         break;
 485                 case OPT_MONOTONIC:
 486                         monotonic = strtoul_or_err(optarg, _("failed to parse monotonic offset"));
 487                         force_monotonic = 1;
 488                         break;
 489                 case OPT_BOOTTIME:
 490                         boottime = strtoul_or_err(optarg, _("failed to parse boottime offset"));
 491                         force_boottime = 1;
 492                         break;
 493
 494                 case 'h':
 495                         usage();
 496                 case 'V':
 497                         print_version(EXIT_SUCCESS);
 498                 default:
 499                         errtryhelp(EXIT_FAILURE);
 500                 }
 501         }
 502
 503         if ((force_monotonic || force_boottime) && !(unshare_flags & CLONE_NEWTIME))
 504                 errx(EXIT_FAILURE, _("options --monotonic and --boottime require "
 505                         "unsharing of a time namespace (-t)"));
 506
 507         if (npersists && (unshare_flags & CLONE_NEWNS))
 508                 bind_ns_files_from_child(&pid, fds);
 509
 510         if (-1 == unshare(unshare_flags))
 511                 err(EXIT_FAILURE, _("unshare failed"));
 512
 513         if (npersists) {
 514                 if (pid && (unshare_flags & CLONE_NEWNS)) {
 515                         int rc;
 516                         char ch = PIPE_SYNC_BYTE;
 517
 518                         /* signal child we are ready */
 519                         write_all(fds[1], &ch, 1);
 520                         close(fds[1]);
 521                         fds[1] = -1;
 522
 523                         /* wait for bind_ns_files_from_child() */
 524                         do {
 525                                 rc = waitpid(pid, &status, 0);
 526                                 if (rc < 0) {
 527                                         if (errno == EINTR)
 528                                                 continue;
 529                                         err(EXIT_FAILURE, _("waitpid failed"));
 530                                 }
 531                                 if (WIFEXITED(status) &&
 532                                     WEXITSTATUS(status) != EXIT_SUCCESS)
 533                                         return WEXITSTATUS(status);
 534                         } while (rc < 0);
 535                 } else
 536                         /* simple way, just bind */
 537                         bind_ns_files(getpid());
 538         }
 539
 540         if (force_boottime)
 541                 settime(boottime, CLOCK_BOOTTIME);
 542
 543         if (force_monotonic)
 544                 settime(monotonic, CLOCK_MONOTONIC);
 545
 546         if (forkit) {
 547                 pid = fork();
 548
 549                 switch(pid) {
 550                 case -1:
 551                         err(EXIT_FAILURE, _("fork failed"));
 552                 case 0: /* child */
 553                         break;
 554                 default: /* parent */
 555                         if (waitpid(pid, &status, 0) == -1)
 556                                 err(EXIT_FAILURE, _("waitpid failed"));
 557                         if (WIFEXITED(status))
 558                                 return WEXITSTATUS(status);
 559                         else if (WIFSIGNALED(status))
 560                                 kill(getpid(), WTERMSIG(status));
 561                         err(EXIT_FAILURE, _("child exit failed"));
 562                 }
 563         }
 564
 565         if (kill_child_signo != 0 && prctl(PR_SET_PDEATHSIG, kill_child_signo) < 0)
 566                 err(EXIT_FAILURE, "prctl failed");
 567
 568         if (mapuser != (uid_t) -1)
 569                 map_id(_PATH_PROC_UIDMAP, mapuser, real_euid);
 570
 571         /* Since Linux 3.19 unprivileged writing of /proc/self/gid_map
 572          * has been disabled unless /proc/self/setgroups is written
 573          * first to permanently disable the ability to call setgroups
 574          * in that user namespace. */
 575         if (mapgroup != (gid_t) -1) {
 576                 if (setgrpcmd == SETGROUPS_ALLOW)
 577                         errx(EXIT_FAILURE, _("options --setgroups=allow and "
 578                                         "--map-group are mutually exclusive"));
 579                 setgroups_control(SETGROUPS_DENY);
 580                 map_id(_PATH_PROC_GIDMAP, mapgroup, real_egid);
 581         }
 582
 583         if (setgrpcmd != SETGROUPS_NONE)
 584                 setgroups_control(setgrpcmd);
 585
 586         if ((unshare_flags & CLONE_NEWNS) && propagation)
 587                 set_propagation(propagation);
 588
 589         if (newroot) {
 590                 if (chroot(newroot) != 0)
 591                         err(EXIT_FAILURE,
 592                             _("cannot change root directory to '%s'"), newroot);
 593                 newdir = newdir ?: "/";
 594         }
 595         if (newdir && chdir(newdir))
 596                 err(EXIT_FAILURE, _("cannot chdir to '%s'"), newdir);
 597
 598         if (procmnt) {
 599                 if (!newroot && mount("none", procmnt, NULL, MS_PRIVATE|MS_REC, NULL) != 0)
 600                         err(EXIT_FAILURE, _("umount %s failed"), procmnt);
 601                 if (mount("proc", procmnt, "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) != 0)
 602                         err(EXIT_FAILURE, _("mount %s failed"), procmnt);
 603         }
 604
 605         if (force_gid) {
 606                 if (setgroups(0, NULL) != 0)    /* drop supplementary groups */
 607                         err(EXIT_FAILURE, _("setgroups failed"));
 608                 if (setgid(gid) < 0)            /* change GID */
 609                         err(EXIT_FAILURE, _("setgid failed"));
 610         }
 611         if (force_uid && setuid(uid) < 0)       /* change UID */
 612                 err(EXIT_FAILURE, _("setuid failed"));
 613
 614         /* We use capabilities system calls to propagate the permitted
 615          * capabilities into the ambient set because we have already
 616          * forked so are in async-signal-safe context. */
 617         if (keepcaps && (unshare_flags & CLONE_NEWUSER)) {
 618                 struct __user_cap_header_struct header = {
 619                         .version = _LINUX_CAPABILITY_VERSION_3,
 620                         .pid = 0,
 621                 };
 622
 623                 struct __user_cap_data_struct payload[_LINUX_CAPABILITY_U32S_3] = { 0 };
 624                 int cap;
 625                 uint64_t effective;
 626
 627                 if (capget(&header, payload) < 0)
 628                         err(EXIT_FAILURE, _("capget failed"));
 629
 630                 /* In order the make capabilities ambient, we first need to ensure
 631                  * that they are all inheritable. */
 632                 payload[0].inheritable = payload[0].permitted;
 633                 payload[1].inheritable = payload[1].permitted;
 634
 635                 if (capset(&header, payload) < 0)
 636                         err(EXIT_FAILURE, _("capset failed"));
 637
 638                 effective = ((uint64_t)payload[1].effective << 32) |  (uint64_t)payload[0].effective;
 639
 640                 for (cap = 0; cap < 64; cap++) {
 641                         /* This is the same check as cap_valid(), but using
 642                          * the runtime value for the last valid cap. */
 643                         if (cap > cap_last_cap())
 644                                 continue;
 645
 646                         if ((effective & (1 << cap))
 647                             && prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0) < 0)
 648                                         err(EXIT_FAILURE, _("prctl(PR_CAP_AMBIENT) failed"));
 649                 }
 650         }
 651
 652         if (optind < argc) {
 653                 execvp(argv[optind], argv + optind);
 654                 errexec(argv[optind]);
 655         }
 656         exec_shell();
 657 }