src/nspawn.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU General Public License as published by
  10   the Free Software Foundation; either version 2 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <signal.h>
  23 #include <sched.h>
  24 #include <unistd.h>
  25 #include <sys/types.h>
  26 #include <sys/syscall.h>
  27 #include <sys/mount.h>
  28 #include <sys/wait.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include <stdio.h>
  32 #include <errno.h>
  33 #include <sys/prctl.h>
  34 #include <sys/capability.h>
  35 #include <getopt.h>
  36 #include <sys/epoll.h>
  37 #include <termios.h>
  38 #include <sys/signalfd.h>
  39 #include <grp.h>
  40 #include <linux/fs.h>
  41
  42 #include <systemd/sd-daemon.h>
  43
  44 #include "log.h"
  45 #include "util.h"
  46 #include "mkdir.h"
  47 #include "audit.h"
  48 #include "missing.h"
  49 #include "cgroup-util.h"
  50 #include "strv.h"
  51 #include "loopback-setup.h"
  52
  53 static char *arg_directory = NULL;
  54 static char *arg_user = NULL;
  55 static bool arg_private_network = false;
  56
  57 static int help(void) {
  58
  59         printf("%s [OPTIONS...] [PATH] [ARGUMENTS...]\n\n"
  60                "Spawn a minimal namespace container for debugging, testing and building.\n\n"
  61                "  -h --help            Show this help\n"
  62                "  -D --directory=NAME  Root directory for the container\n"
  63                "  -u --user=USER       Run the command under specified user or uid\n"
  64                "     --private-network Disable network in container\n",
  65                program_invocation_short_name);
  66
  67         return 0;
  68 }
  69
  70 static int parse_argv(int argc, char *argv[]) {
  71
  72         enum {
  73                 ARG_PRIVATE_NETWORK = 0x100
  74         };
  75
  76         static const struct option options[] = {
  77                 { "help",            no_argument,       NULL, 'h'                 },
  78                 { "directory",       required_argument, NULL, 'D'                 },
  79                 { "user",            required_argument, NULL, 'u'                 },
  80                 { "private-network", no_argument,       NULL, ARG_PRIVATE_NETWORK },
  81                 { NULL,              0,                 NULL, 0                   }
  82         };
  83
  84         int c;
  85
  86         assert(argc >= 0);
  87         assert(argv);
  88
  89         while ((c = getopt_long(argc, argv, "+hD:u:", options, NULL)) >= 0) {
  90
  91                 switch (c) {
  92
  93                 case 'h':
  94                         help();
  95                         return 0;
  96
  97                 case 'D':
  98                         free(arg_directory);
  99                         if (!(arg_directory = strdup(optarg))) {
 100                                 log_error("Failed to duplicate root directory.");
 101                                 return -ENOMEM;
 102                         }
 103
 104                         break;
 105
 106                 case 'u':
 107                         free(arg_user);
 108                         if (!(arg_user = strdup(optarg))) {
 109                                 log_error("Failed to duplicate user name.");
 110                                 return -ENOMEM;
 111                         }
 112
 113                         break;
 114
 115                 case ARG_PRIVATE_NETWORK:
 116                         arg_private_network = true;
 117                         break;
 118
 119                 case '?':
 120                         return -EINVAL;
 121
 122                 default:
 123                         log_error("Unknown option code %c", c);
 124                         return -EINVAL;
 125                 }
 126         }
 127
 128         return 1;
 129 }
 130
 131 static int mount_all(const char *dest) {
 132
 133         typedef struct MountPoint {
 134                 const char *what;
 135                 const char *where;
 136                 const char *type;
 137                 const char *options;
 138                 unsigned long flags;
 139                 bool fatal;
 140         } MountPoint;
 141
 142         static const MountPoint mount_table[] = {
 143                 { "proc",      "/proc",     "proc",  NULL,       MS_NOSUID|MS_NOEXEC|MS_NODEV, true  },
 144                 { "/proc/sys", "/proc/sys", "bind",  NULL,       MS_BIND, true                       },   /* Bind mount first */
 145                 { "/proc/sys", "/proc/sys", "bind",  NULL,       MS_BIND|MS_RDONLY|MS_REMOUNT, true  },   /* Then, make it r/o */
 146                 { "/sys",      "/sys",      "bind",  NULL,       MS_BIND,                      true  },   /* Bind mount first */
 147                 { "/sys",      "/sys",      "bind",  NULL,       MS_BIND|MS_RDONLY|MS_REMOUNT, true  },   /* Then, make it r/o */
 148                 { "tmpfs",     "/dev",      "tmpfs", "mode=755", MS_NOSUID,                    true  },
 149                 { "/dev/pts",  "/dev/pts",  "bind",  NULL,       MS_BIND,                      true  },
 150                 { "tmpfs",     "/run",      "tmpfs", "mode=755", MS_NOSUID|MS_NODEV,           true  },
 151 #ifdef HAVE_SELINUX
 152                 { "/sys/fs/selinux", "/sys/fs/selinux", "bind", NULL, MS_BIND,                      false },  /* Bind mount first */
 153                 { "/sys/fs/selinux", "/sys/fs/selinux", "bind", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, false },  /* Then, make it r/o */
 154 #endif
 155         };
 156
 157         unsigned k;
 158         int r = 0;
 159         char *where;
 160
 161         for (k = 0; k < ELEMENTSOF(mount_table); k++) {
 162                 int t;
 163
 164                 if (asprintf(&where, "%s/%s", dest, mount_table[k].where) < 0) {
 165                         log_error("Out of memory");
 166
 167                         if (r == 0)
 168                                 r = -ENOMEM;
 169
 170                         break;
 171                 }
 172
 173                 if ((t = path_is_mount_point(where, false)) < 0) {
 174                         log_error("Failed to detect whether %s is a mount point: %s", where, strerror(-t));
 175                         free(where);
 176
 177                         if (r == 0)
 178                                 r = t;
 179
 180                         continue;
 181                 }
 182
 183                 mkdir_p(where, 0755);
 184
 185                 if (mount(mount_table[k].what,
 186                           where,
 187                           mount_table[k].type,
 188                           mount_table[k].flags,
 189                           mount_table[k].options) < 0 &&
 190                     mount_table[k].fatal) {
 191
 192                         log_error("mount(%s) failed: %m", where);
 193
 194                         if (r == 0)
 195                                 r = -errno;
 196                 }
 197
 198                 free(where);
 199         }
 200
 201         /* Fix the timezone, if possible */
 202         if (asprintf(&where, "%s/etc/localtime", dest) >= 0) {
 203
 204                 if (mount("/etc/localtime", where, "bind", MS_BIND, NULL) >= 0)
 205                         mount("/etc/localtime", where, "bind", MS_BIND|MS_REMOUNT|MS_RDONLY, NULL);
 206
 207                 free(where);
 208         }
 209
 210         if (asprintf(&where, "%s/etc/timezone", dest) >= 0) {
 211
 212                 if (mount("/etc/timezone", where, "bind", MS_BIND, NULL) >= 0)
 213                         mount("/etc/timezone", where, "bind", MS_BIND|MS_REMOUNT|MS_RDONLY, NULL);
 214
 215                 free(where);
 216         }
 217
 218         return r;
 219 }
 220
 221 static int copy_devnodes(const char *dest, const char *console) {
 222
 223         static const char devnodes[] =
 224                 "null\0"
 225                 "zero\0"
 226                 "full\0"
 227                 "random\0"
 228                 "urandom\0"
 229                 "tty\0"
 230                 "ptmx\0"
 231                 "kmsg\0"
 232                 "rtc0\0";
 233
 234         const char *d;
 235         int r = 0, k;
 236         mode_t u;
 237         struct stat st;
 238         char *from = NULL, *to = NULL;
 239
 240         assert(dest);
 241         assert(console);
 242
 243         u = umask(0000);
 244
 245         NULSTR_FOREACH(d, devnodes) {
 246                 from = to = NULL;
 247
 248                 asprintf(&from, "/dev/%s", d);
 249                 asprintf(&to, "%s/dev/%s", dest, d);
 250
 251                 if (!from || !to) {
 252                         log_error("Failed to allocate devnode path");
 253
 254                         free(from);
 255                         free(to);
 256
 257                         from = to = NULL;
 258
 259                         if (r == 0)
 260                                 r = -ENOMEM;
 261
 262                         break;
 263                 }
 264
 265                 if (stat(from, &st) < 0) {
 266
 267                         if (errno != ENOENT) {
 268                                 log_error("Failed to stat %s: %m", from);
 269                                 if (r == 0)
 270                                         r = -errno;
 271                         }
 272
 273                 } else if (!S_ISCHR(st.st_mode) && !S_ISBLK(st.st_mode)) {
 274
 275                         log_error("%s is not a char or block device, cannot copy.", from);
 276                         if (r == 0)
 277                                 r = -EIO;
 278
 279                 } else if (mknod(to, st.st_mode, st.st_rdev) < 0) {
 280
 281                         log_error("mknod(%s) failed: %m", dest);
 282                         if (r == 0)
 283                                 r = -errno;
 284                 }
 285
 286                 free(from);
 287                 free(to);
 288         }
 289
 290         if (stat(console, &st) < 0) {
 291
 292                 log_error("Failed to stat %s: %m", console);
 293                 if (r == 0)
 294                         r = -errno;
 295
 296                 goto finish;
 297
 298         } else if (!S_ISCHR(st.st_mode)) {
 299
 300                 log_error("/dev/console is not a char device.");
 301                 if (r == 0)
 302                         r = -EIO;
 303
 304                 goto finish;
 305         }
 306
 307         if (asprintf(&to, "%s/dev/console", dest) < 0) {
 308
 309                 log_error("Out of memory");
 310                 if (r == 0)
 311                         r = -ENOMEM;
 312
 313                  goto finish;
 314         }
 315
 316         /* We need to bind mount the right tty to /dev/console since
 317          * ptys can only exist on pts file systems. To have something
 318          * to bind mount things on we create a device node first, that
 319          * has the right major/minor (note that the major minor
 320          * doesn't actually matter here, since we mount it over
 321          * anyway). */
 322
 323         if (mknod(to, (st.st_mode & ~07777) | 0600, st.st_rdev) < 0)
 324                 log_error("mknod for /dev/console failed: %m");
 325
 326         if (mount(console, to, "bind", MS_BIND, NULL) < 0) {
 327                 log_error("bind mount for /dev/console failed: %m");
 328
 329                 if (r == 0)
 330                         r = -errno;
 331         }
 332
 333         free(to);
 334
 335         if ((k = chmod_and_chown(console, 0600, 0, 0)) < 0) {
 336                 log_error("Failed to correct access mode for TTY: %s", strerror(-k));
 337
 338                 if (r == 0)
 339                         r = k;
 340         }
 341
 342 finish:
 343         umask(u);
 344
 345         return r;
 346 }
 347
 348 static int drop_capabilities(void) {
 349         static const unsigned long retain[] = {
 350                 CAP_CHOWN,
 351                 CAP_DAC_OVERRIDE,
 352                 CAP_DAC_READ_SEARCH,
 353                 CAP_FOWNER,
 354                 CAP_FSETID,
 355                 CAP_IPC_OWNER,
 356                 CAP_KILL,
 357                 CAP_LEASE,
 358                 CAP_LINUX_IMMUTABLE,
 359                 CAP_NET_BIND_SERVICE,
 360                 CAP_NET_BROADCAST,
 361                 CAP_NET_RAW,
 362                 CAP_SETGID,
 363                 CAP_SETFCAP,
 364                 CAP_SETPCAP,
 365                 CAP_SETUID,
 366                 CAP_SYS_ADMIN,
 367                 CAP_SYS_CHROOT,
 368                 CAP_SYS_NICE,
 369                 CAP_SYS_PTRACE,
 370                 CAP_SYS_TTY_CONFIG
 371         };
 372
 373         unsigned long l;
 374
 375         for (l = 0; l <= cap_last_cap(); l++) {
 376                 unsigned i;
 377
 378                 for (i = 0; i < ELEMENTSOF(retain); i++)
 379                         if (retain[i] == l)
 380                                 break;
 381
 382                 if (i < ELEMENTSOF(retain))
 383                         continue;
 384
 385                 if (prctl(PR_CAPBSET_DROP, l) < 0) {
 386                         log_error("PR_CAPBSET_DROP failed: %m");
 387                         return -errno;
 388                 }
 389         }
 390
 391         return 0;
 392 }
 393
 394 static int is_os_tree(const char *path) {
 395         int r;
 396         char *p;
 397         /* We use /bin/sh as flag file if something is an OS */
 398
 399         if (asprintf(&p, "%s/bin/sh", path) < 0)
 400                 return -ENOMEM;
 401
 402         r = access(p, F_OK);
 403         free(p);
 404
 405         return r < 0 ? 0 : 1;
 406 }
 407
 408 static int process_pty(int master, sigset_t *mask) {
 409
 410         char in_buffer[LINE_MAX], out_buffer[LINE_MAX];
 411         size_t in_buffer_full = 0, out_buffer_full = 0;
 412         struct epoll_event stdin_ev, stdout_ev, master_ev, signal_ev;
 413         bool stdin_readable = false, stdout_writable = false, master_readable = false, master_writable = false;
 414         int ep = -1, signal_fd = -1, r;
 415
 416         fd_nonblock(STDIN_FILENO, 1);
 417         fd_nonblock(STDOUT_FILENO, 1);
 418         fd_nonblock(master, 1);
 419
 420         if ((signal_fd = signalfd(-1, mask, SFD_NONBLOCK|SFD_CLOEXEC)) < 0) {
 421                 log_error("signalfd(): %m");
 422                 r = -errno;
 423                 goto finish;
 424         }
 425
 426         if ((ep = epoll_create1(EPOLL_CLOEXEC)) < 0) {
 427                 log_error("Failed to create epoll: %m");
 428                 r = -errno;
 429                 goto finish;
 430         }
 431
 432         zero(stdin_ev);
 433         stdin_ev.events = EPOLLIN|EPOLLET;
 434         stdin_ev.data.fd = STDIN_FILENO;
 435
 436         zero(stdout_ev);
 437         stdout_ev.events = EPOLLOUT|EPOLLET;
 438         stdout_ev.data.fd = STDOUT_FILENO;
 439
 440         zero(master_ev);
 441         master_ev.events = EPOLLIN|EPOLLOUT|EPOLLET;
 442         master_ev.data.fd = master;
 443
 444         zero(signal_ev);
 445         signal_ev.events = EPOLLIN;
 446         signal_ev.data.fd = signal_fd;
 447
 448         if (epoll_ctl(ep, EPOLL_CTL_ADD, STDIN_FILENO, &stdin_ev) < 0 ||
 449             epoll_ctl(ep, EPOLL_CTL_ADD, STDOUT_FILENO, &stdout_ev) < 0 ||
 450             epoll_ctl(ep, EPOLL_CTL_ADD, master, &master_ev) < 0 ||
 451             epoll_ctl(ep, EPOLL_CTL_ADD, signal_fd, &signal_ev) < 0) {
 452                 log_error("Failed to regiser fds in epoll: %m");
 453                 r = -errno;
 454                 goto finish;
 455         }
 456
 457         for (;;) {
 458                 struct epoll_event ev[16];
 459                 ssize_t k;
 460                 int i, nfds;
 461
 462                 if ((nfds = epoll_wait(ep, ev, ELEMENTSOF(ev), -1)) < 0) {
 463
 464                         if (errno == EINTR || errno == EAGAIN)
 465                                 continue;
 466
 467                         log_error("epoll_wait(): %m");
 468                         r = -errno;
 469                         goto finish;
 470                 }
 471
 472                 assert(nfds >= 1);
 473
 474                 for (i = 0; i < nfds; i++) {
 475                         if (ev[i].data.fd == STDIN_FILENO) {
 476
 477                                 if (ev[i].events & (EPOLLIN|EPOLLHUP))
 478                                         stdin_readable = true;
 479
 480                         } else if (ev[i].data.fd == STDOUT_FILENO) {
 481
 482                                 if (ev[i].events & (EPOLLOUT|EPOLLHUP))
 483                                         stdout_writable = true;
 484
 485                         } else if (ev[i].data.fd == master) {
 486
 487                                 if (ev[i].events & (EPOLLIN|EPOLLHUP))
 488                                         master_readable = true;
 489
 490                                 if (ev[i].events & (EPOLLOUT|EPOLLHUP))
 491                                         master_writable = true;
 492
 493                         } else if (ev[i].data.fd == signal_fd) {
 494                                 struct signalfd_siginfo sfsi;
 495                                 ssize_t n;
 496
 497                                 if ((n = read(signal_fd, &sfsi, sizeof(sfsi))) != sizeof(sfsi)) {
 498
 499                                         if (n >= 0) {
 500                                                 log_error("Failed to read from signalfd: invalid block size");
 501                                                 r = -EIO;
 502                                                 goto finish;
 503                                         }
 504
 505                                         if (errno != EINTR && errno != EAGAIN) {
 506                                                 log_error("Failed to read from signalfd: %m");
 507                                                 r = -errno;
 508                                                 goto finish;
 509                                         }
 510                                 } else {
 511
 512                                         if (sfsi.ssi_signo == SIGWINCH) {
 513                                                 struct winsize ws;
 514
 515                                                 /* The window size changed, let's forward that. */
 516                                                 if (ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) >= 0)
 517                                                         ioctl(master, TIOCSWINSZ, &ws);
 518                                         } else {
 519                                                 r = 0;
 520                                                 goto finish;
 521                                         }
 522                                 }
 523                         }
 524                 }
 525
 526                 while ((stdin_readable && in_buffer_full <= 0) ||
 527                        (master_writable && in_buffer_full > 0) ||
 528                        (master_readable && out_buffer_full <= 0) ||
 529                        (stdout_writable && out_buffer_full > 0)) {
 530
 531                         if (stdin_readable && in_buffer_full < LINE_MAX) {
 532
 533                                 if ((k = read(STDIN_FILENO, in_buffer + in_buffer_full, LINE_MAX - in_buffer_full)) < 0) {
 534
 535                                         if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)
 536                                                 stdin_readable = false;
 537                                         else {
 538                                                 log_error("read(): %m");
 539                                                 r = -errno;
 540                                                 goto finish;
 541                                         }
 542                                 } else
 543                                         in_buffer_full += (size_t) k;
 544                         }
 545
 546                         if (master_writable && in_buffer_full > 0) {
 547
 548                                 if ((k = write(master, in_buffer, in_buffer_full)) < 0) {
 549
 550                                         if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)
 551                                                 master_writable = false;
 552                                         else {
 553                                                 log_error("write(): %m");
 554                                                 r = -errno;
 555                                                 goto finish;
 556                                         }
 557
 558                                 } else {
 559                                         assert(in_buffer_full >= (size_t) k);
 560                                         memmove(in_buffer, in_buffer + k, in_buffer_full - k);
 561                                         in_buffer_full -= k;
 562                                 }
 563                         }
 564
 565                         if (master_readable && out_buffer_full < LINE_MAX) {
 566
 567                                 if ((k = read(master, out_buffer + out_buffer_full, LINE_MAX - out_buffer_full)) < 0) {
 568
 569                                         if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)
 570                                                 master_readable = false;
 571                                         else {
 572                                                 log_error("read(): %m");
 573                                                 r = -errno;
 574                                                 goto finish;
 575                                         }
 576                                 }  else
 577                                         out_buffer_full += (size_t) k;
 578                         }
 579
 580                         if (stdout_writable && out_buffer_full > 0) {
 581
 582                                 if ((k = write(STDOUT_FILENO, out_buffer, out_buffer_full)) < 0) {
 583
 584                                         if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)
 585                                                 stdout_writable = false;
 586                                         else {
 587                                                 log_error("write(): %m");
 588                                                 r = -errno;
 589                                                 goto finish;
 590                                         }
 591
 592                                 } else {
 593                                         assert(out_buffer_full >= (size_t) k);
 594                                         memmove(out_buffer, out_buffer + k, out_buffer_full - k);
 595                                         out_buffer_full -= k;
 596                                 }
 597                         }
 598                 }
 599         }
 600
 601 finish:
 602         if (ep >= 0)
 603                 close_nointr_nofail(ep);
 604
 605         if (signal_fd >= 0)
 606                 close_nointr_nofail(signal_fd);
 607
 608         return r;
 609 }
 610
 611 int main(int argc, char *argv[]) {
 612         pid_t pid = 0;
 613         int r = EXIT_FAILURE, k;
 614         char *oldcg = NULL, *newcg = NULL;
 615         int master = -1;
 616         const char *console = NULL;
 617         struct termios saved_attr, raw_attr;
 618         sigset_t mask;
 619         bool saved_attr_valid = false;
 620         struct winsize ws;
 621
 622         log_parse_environment();
 623         log_open();
 624
 625         if ((r = parse_argv(argc, argv)) <= 0)
 626                 goto finish;
 627
 628         if (arg_directory) {
 629                 char *p;
 630
 631                 p = path_make_absolute_cwd(arg_directory);
 632                 free(arg_directory);
 633                 arg_directory = p;
 634         } else
 635                 arg_directory = get_current_dir_name();
 636
 637         if (!arg_directory) {
 638                 log_error("Failed to determine path");
 639                 goto finish;
 640         }
 641
 642         path_kill_slashes(arg_directory);
 643
 644         if (geteuid() != 0) {
 645                 log_error("Need to be root.");
 646                 goto finish;
 647         }
 648
 649         if (sd_booted() <= 0) {
 650                 log_error("Not running on a systemd system.");
 651                 goto finish;
 652         }
 653
 654         if (path_equal(arg_directory, "/")) {
 655                 log_error("Spawning container on root directory not supported.");
 656                 goto finish;
 657         }
 658
 659         if (is_os_tree(arg_directory) <= 0) {
 660                 log_error("Directory %s doesn't look like an OS root directory. Refusing.", arg_directory);
 661                 goto finish;
 662         }
 663
 664         if ((k = cg_get_by_pid(SYSTEMD_CGROUP_CONTROLLER, 0, &oldcg)) < 0) {
 665                 log_error("Failed to determine current cgroup: %s", strerror(-k));
 666                 goto finish;
 667         }
 668
 669         if (asprintf(&newcg, "%s/nspawn-%lu", oldcg, (unsigned long) getpid()) < 0) {
 670                 log_error("Failed to allocate cgroup path.");
 671                 goto finish;
 672         }
 673
 674         if ((k = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, newcg, 0)) < 0)  {
 675                 log_error("Failed to create cgroup: %s", strerror(-k));
 676                 goto finish;
 677         }
 678
 679         if ((master = posix_openpt(O_RDWR|O_NOCTTY|O_CLOEXEC|O_NDELAY)) < 0) {
 680                 log_error("Failed to acquire pseudo tty: %m");
 681                 goto finish;
 682         }
 683
 684         if (!(console = ptsname(master))) {
 685                 log_error("Failed to determine tty name: %m");
 686                 goto finish;
 687         }
 688
 689         log_info("Spawning namespace container on %s (console is %s).", arg_directory, console);
 690
 691         if (ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) >= 0)
 692                 ioctl(master, TIOCSWINSZ, &ws);
 693
 694         if (unlockpt(master) < 0) {
 695                 log_error("Failed to unlock tty: %m");
 696                 goto finish;
 697         }
 698
 699         if (tcgetattr(STDIN_FILENO, &saved_attr) < 0) {
 700                 log_error("Failed to get terminal attributes: %m");
 701                 goto finish;
 702         }
 703
 704         saved_attr_valid = true;
 705
 706         raw_attr = saved_attr;
 707         cfmakeraw(&raw_attr);
 708         raw_attr.c_lflag &= ~ECHO;
 709
 710         if (tcsetattr(STDIN_FILENO, TCSANOW, &raw_attr) < 0) {
 711                 log_error("Failed to set terminal attributes: %m");
 712                 goto finish;
 713         }
 714
 715         assert_se(sigemptyset(&mask) == 0);
 716         sigset_add_many(&mask, SIGCHLD, SIGWINCH, SIGTERM, SIGINT, -1);
 717         assert_se(sigprocmask(SIG_BLOCK, &mask, NULL) == 0);
 718
 719         pid = syscall(__NR_clone, SIGCHLD|CLONE_NEWIPC|CLONE_NEWNS|CLONE_NEWPID|CLONE_NEWUTS|(arg_private_network ? CLONE_NEWNET : 0), NULL);
 720         if (pid < 0) {
 721                 if (errno == EINVAL)
 722                         log_error("clone() failed, do you have namespace support enabled in your kernel? (You need UTS, IPC, PID and NET namespacing built in): %m");
 723                 else
 724                         log_error("clone() failed: %m");
 725
 726                 goto finish;
 727         }
 728
 729         if (pid == 0) {
 730                 /* child */
 731
 732                 const char *hn;
 733                 const char *home = NULL;
 734                 uid_t uid = (uid_t) -1;
 735                 gid_t gid = (gid_t) -1;
 736                 const char *envp[] = {
 737                         "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
 738                         "container=systemd-nspawn", /* LXC sets container=lxc, so follow the scheme here */
 739                         NULL, /* TERM */
 740                         NULL, /* HOME */
 741                         NULL, /* USER */
 742                         NULL, /* LOGNAME */
 743                         NULL
 744                 };
 745
 746                 envp[2] = strv_find_prefix(environ, "TERM=");
 747
 748                 close_nointr_nofail(master);
 749
 750                 close_nointr(STDIN_FILENO);
 751                 close_nointr(STDOUT_FILENO);
 752                 close_nointr(STDERR_FILENO);
 753
 754                 close_all_fds(NULL, 0);
 755
 756                 reset_all_signal_handlers();
 757
 758                 assert_se(sigemptyset(&mask) == 0);
 759                 assert_se(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);
 760
 761                 if (setsid() < 0)
 762                         goto child_fail;
 763
 764                 if (prctl(PR_SET_PDEATHSIG, SIGKILL) < 0)
 765                         goto child_fail;
 766
 767                 /* Mark / as private, in case somebody marked it shared */
 768                 if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) < 0)
 769                         goto child_fail;
 770
 771                 if (mount_all(arg_directory) < 0)
 772                         goto child_fail;
 773
 774                 if (copy_devnodes(arg_directory, console) < 0)
 775                         goto child_fail;
 776
 777                 if (chdir(arg_directory) < 0) {
 778                         log_error("chdir(%s) failed: %m", arg_directory);
 779                         goto child_fail;
 780                 }
 781
 782                 if (open_terminal("dev/console", O_RDWR) != STDIN_FILENO ||
 783                     dup2(STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO ||
 784                     dup2(STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO)
 785                         goto child_fail;
 786
 787                 if (mount(arg_directory, "/", "bind", MS_BIND|MS_MOVE, NULL) < 0) {
 788                         log_error("mount(MS_MOVE) failed: %m");
 789                         goto child_fail;
 790                 }
 791
 792                 if (chroot(".") < 0) {
 793                         log_error("chroot() failed: %m");
 794                         goto child_fail;
 795                 }
 796
 797                 if (chdir("/") < 0) {
 798                         log_error("chdir() failed: %m");
 799                         goto child_fail;
 800                 }
 801
 802                 umask(0022);
 803
 804                 loopback_setup();
 805
 806                 if (drop_capabilities() < 0)
 807                         goto child_fail;
 808
 809                 if (arg_user) {
 810
 811                         if (get_user_creds((const char**)&arg_user, &uid, &gid, &home) < 0) {
 812                                 log_error("get_user_creds() failed: %m");
 813                                 goto child_fail;
 814                         }
 815
 816                         if (mkdir_parents(home, 0775) < 0) {
 817                                 log_error("mkdir_parents() failed: %m");
 818                                 goto child_fail;
 819                         }
 820
 821                         if (safe_mkdir(home, 0775, uid, gid) < 0) {
 822                                 log_error("safe_mkdir() failed: %m");
 823                                 goto child_fail;
 824                         }
 825
 826                         if (initgroups((const char*)arg_user, gid) < 0) {
 827                                 log_error("initgroups() failed: %m");
 828                                 goto child_fail;
 829                         }
 830
 831                         if (setresgid(gid, gid, gid) < 0) {
 832                                 log_error("setregid() failed: %m");
 833                                 goto child_fail;
 834                         }
 835
 836                         if (setresuid(uid, uid, uid) < 0) {
 837                                 log_error("setreuid() failed: %m");
 838                                 goto child_fail;
 839                         }
 840                 }
 841
 842                 if ((asprintf((char**)(envp + 3), "HOME=%s", home? home: "/root") < 0) ||
 843                     (asprintf((char**)(envp + 4), "USER=%s", arg_user? arg_user : "root") < 0) ||
 844                     (asprintf((char**)(envp + 5), "LOGNAME=%s", arg_user? arg_user : "root") < 0)) {
 845                     log_error("Out of memory");
 846                     goto child_fail;
 847                 }
 848
 849                 if ((hn = file_name_from_path(arg_directory)))
 850                         sethostname(hn, strlen(hn));
 851
 852                 if (argc > optind)
 853                         execvpe(argv[optind], argv + optind, (char**) envp);
 854                 else {
 855                         chdir(home ? home : "/root");
 856                         execle("/bin/bash", "-bash", NULL, (char**) envp);
 857                 }
 858
 859                 log_error("execv() failed: %m");
 860
 861         child_fail:
 862                 _exit(EXIT_FAILURE);
 863         }
 864
 865         if (process_pty(master, &mask) < 0)
 866                 goto finish;
 867
 868         if (saved_attr_valid) {
 869                 tcsetattr(STDIN_FILENO, TCSANOW, &saved_attr);
 870                 saved_attr_valid = false;
 871         }
 872
 873         r = wait_for_terminate_and_warn(argc > optind ? argv[optind] : "bash", pid);
 874
 875         if (r < 0)
 876                 r = EXIT_FAILURE;
 877
 878 finish:
 879         if (saved_attr_valid)
 880                 tcsetattr(STDIN_FILENO, TCSANOW, &saved_attr);
 881
 882         if (master >= 0)
 883                 close_nointr_nofail(master);
 884
 885         if (oldcg)
 886                 cg_attach(SYSTEMD_CGROUP_CONTROLLER, oldcg, 0);
 887
 888         if (newcg)
 889                 cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, newcg, true);
 890
 891         free(arg_directory);
 892         free(oldcg);
 893         free(newcg);
 894
 895         return r;
 896 }