src/lxc/attach.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #ifndef _GNU_SOURCE
   4 #define _GNU_SOURCE 1
   5 #endif
   6 #include <errno.h>
   7 #include <fcntl.h>
   8 #include <grp.h>
   9 #include <linux/unistd.h>
  10 #include <pwd.h>
  11 #include <pthread.h>
  12 #include <signal.h>
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <string.h>
  16 #include <sys/mount.h>
  17 #include <sys/param.h>
  18 #include <sys/prctl.h>
  19 #include <sys/socket.h>
  20 #include <sys/syscall.h>
  21 #include <sys/wait.h>
  22 #include <termios.h>
  23 #include <unistd.h>
  24
  25 #include <lxc/lxccontainer.h>
  26
  27 #include "af_unix.h"
  28 #include "attach.h"
  29 #include "caps.h"
  30 #include "cgroup.h"
  31 #include "commands.h"
  32 #include "conf.h"
  33 #include "config.h"
  34 #include "confile.h"
  35 #include "log.h"
  36 #include "lsm/lsm.h"
  37 #include "lxclock.h"
  38 #include "lxcseccomp.h"
  39 #include "macro.h"
  40 #include "mainloop.h"
  41 #include "memory_utils.h"
  42 #include "namespace.h"
  43 #include "raw_syscalls.h"
  44 #include "syscall_wrappers.h"
  45 #include "terminal.h"
  46 #include "utils.h"
  47
  48 #if HAVE_SYS_PERSONALITY_H
  49 #include <sys/personality.h>
  50 #endif
  51
  52 lxc_log_define(attach, lxc);
  53
  54 /* Define default options if no options are supplied by the user. */
  55 static lxc_attach_options_t attach_static_default_options = LXC_ATTACH_OPTIONS_DEFAULT;
  56
  57 static struct lxc_proc_context_info *lxc_proc_get_context_info(pid_t pid)
  58 {
  59         __do_free char *line = NULL;
  60         __do_fclose FILE *proc_file = NULL;
  61         __do_free struct lxc_proc_context_info *info = NULL;
  62         int ret;
  63         bool found;
  64         char proc_fn[LXC_PROC_STATUS_LEN];
  65         size_t line_bufsz = 0;
  66
  67         /* Read capabilities. */
  68         ret = snprintf(proc_fn, LXC_PROC_STATUS_LEN, "/proc/%d/status", pid);
  69         if (ret < 0 || ret >= LXC_PROC_STATUS_LEN)
  70                 return NULL;
  71
  72         proc_file = fopen(proc_fn, "re");
  73         if (!proc_file)
  74                 return log_error_errno(NULL, errno, "Failed to open %s", proc_fn);
  75
  76         info = calloc(1, sizeof(*info));
  77         if (!info)
  78                 return NULL;
  79
  80         found = false;
  81
  82         while (getline(&line, &line_bufsz, proc_file) != -1) {
  83                 ret = sscanf(line, "CapBnd: %llx", &info->capability_mask);
  84                 if (ret != EOF && ret == 1) {
  85                         found = true;
  86                         break;
  87                 }
  88         }
  89
  90         if (!found)
  91                 return log_error_errno(NULL, ENOENT, "Failed to read capability bounding set from %s", proc_fn);
  92
  93         info->lsm_label = lsm_process_label_get(pid);
  94         info->ns_inherited = 0;
  95         for (int i = 0; i < LXC_NS_MAX; i++)
  96                 info->ns_fd[i] = -EBADF;
  97
  98         return move_ptr(info);
  99 }
 100
 101 static inline void lxc_proc_close_ns_fd(struct lxc_proc_context_info *ctx)
 102 {
 103         for (int i = 0; i < LXC_NS_MAX; i++)
 104                 close_prot_errno_disarm(ctx->ns_fd[i]);
 105 }
 106
 107 static void lxc_proc_put_context_info(struct lxc_proc_context_info *ctx)
 108 {
 109         free(ctx->lsm_label);
 110         ctx->lsm_label = NULL;
 111
 112         if (ctx->container) {
 113                 lxc_container_put(ctx->container);
 114                 ctx->container = NULL;
 115         }
 116
 117         lxc_proc_close_ns_fd(ctx);
 118         free(ctx);
 119 }
 120
 121 /**
 122  * in_same_namespace - Check whether two processes are in the same namespace.
 123  * @pid1 - PID of the first process.
 124  * @pid2 - PID of the second process.
 125  * @ns   - Name of the namespace to check. Must correspond to one of the names
 126  *         for the namespaces as shown in /proc/<pid/ns/
 127  *
 128  * If the two processes are not in the same namespace returns an fd to the
 129  * namespace of the second process identified by @pid2. If the two processes are
 130  * in the same namespace returns -EINVAL, -1 if an error occurred.
 131  */
 132 static int in_same_namespace(pid_t pid1, pid_t pid2, const char *ns)
 133 {
 134         __do_close int ns_fd1 = -EBADF, ns_fd2 = -EBADF;
 135         int ret = -1;
 136         struct stat ns_st1, ns_st2;
 137
 138         ns_fd1 = lxc_preserve_ns(pid1, ns);
 139         if (ns_fd1 < 0) {
 140                 /* The kernel does not support this namespace. This is not an
 141                  * error.
 142                  */
 143                 if (errno == ENOENT)
 144                         return -EINVAL;
 145
 146                 return -1;
 147         }
 148
 149         ns_fd2 = lxc_preserve_ns(pid2, ns);
 150         if (ns_fd2 < 0)
 151                 return -1;
 152
 153         ret = fstat(ns_fd1, &ns_st1);
 154         if (ret < 0)
 155                 return -1;
 156
 157         ret = fstat(ns_fd2, &ns_st2);
 158         if (ret < 0)
 159                 return -1;
 160
 161         /* processes are in the same namespace */
 162         if ((ns_st1.st_dev == ns_st2.st_dev) && (ns_st1.st_ino == ns_st2.st_ino))
 163                 return -EINVAL;
 164
 165         /* processes are in different namespaces */
 166         return move_fd(ns_fd2);
 167 }
 168
 169 static int lxc_attach_to_ns(pid_t pid, struct lxc_proc_context_info *ctx)
 170 {
 171         for (int i = 0; i < LXC_NS_MAX; i++) {
 172                 int ret;
 173
 174                 if (ctx->ns_fd[i] < 0)
 175                         continue;
 176
 177                 ret = setns(ctx->ns_fd[i], ns_info[i].clone_flag);
 178                 if (ret < 0)
 179                         return log_error_errno(-1,
 180                                                errno, "Failed to attach to %s namespace of %d",
 181                                                ns_info[i].proc_name, pid);
 182
 183                 DEBUG("Attached to %s namespace of %d", ns_info[i].proc_name, pid);
 184         }
 185
 186         return 0;
 187 }
 188
 189 int lxc_attach_remount_sys_proc(void)
 190 {
 191         int ret;
 192
 193         ret = unshare(CLONE_NEWNS);
 194         if (ret < 0)
 195                 return log_error_errno(-1, errno, "Failed to unshare mount namespace");
 196
 197         if (detect_shared_rootfs()) {
 198                 if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL)) {
 199                         SYSERROR("Failed to make / rslave");
 200                         ERROR("Continuing...");
 201                 }
 202         }
 203
 204         /* Assume /proc is always mounted, so remount it. */
 205         ret = umount2("/proc", MNT_DETACH);
 206         if (ret < 0)
 207                 return log_error_errno(-1, errno, "Failed to unmount /proc");
 208
 209         ret = mount("none", "/proc", "proc", 0, NULL);
 210         if (ret < 0)
 211                 return log_error_errno(-1, errno, "Failed to remount /proc");
 212
 213         /*
 214          * Try to umount /sys. If it's not a mount point, we'll get EINVAL, then
 215          * we ignore it because it may not have been mounted in the first place.
 216          */
 217         ret = umount2("/sys", MNT_DETACH);
 218         if (ret < 0 && errno != EINVAL)
 219                 return log_error_errno(-1, errno, "Failed to unmount /sys");
 220
 221         /* Remount it. */
 222         if (ret == 0 && mount("none", "/sys", "sysfs", 0, NULL))
 223                 return log_error_errno(-1, errno, "Failed to remount /sys");
 224
 225         return 0;
 226 }
 227
 228 static int lxc_attach_drop_privs(struct lxc_proc_context_info *ctx)
 229 {
 230         int last_cap;
 231
 232         last_cap = lxc_caps_last_cap();
 233         for (int cap = 0; cap <= last_cap; cap++) {
 234                 if (ctx->capability_mask & (1LL << cap))
 235                         continue;
 236
 237                 if (prctl(PR_CAPBSET_DROP, prctl_arg(cap), prctl_arg(0),
 238                           prctl_arg(0), prctl_arg(0)))
 239                         return log_error_errno(-1, errno, "Failed to drop capability %d", cap);
 240
 241                 TRACE("Dropped capability %d", cap);
 242         }
 243
 244         return 0;
 245 }
 246
 247 static int lxc_attach_set_environment(struct lxc_proc_context_info *init_ctx,
 248                                       enum lxc_attach_env_policy_t policy,
 249                                       char **extra_env, char **extra_keep)
 250 {
 251         int ret;
 252         struct lxc_list *iterator;
 253
 254         if (policy == LXC_ATTACH_CLEAR_ENV) {
 255                 int path_kept = 0;
 256                 char **extra_keep_store = NULL;
 257
 258                 if (extra_keep) {
 259                         size_t count, i;
 260
 261                         for (count = 0; extra_keep[count]; count++)
 262                                 ;
 263
 264                         extra_keep_store = calloc(count, sizeof(char *));
 265                         if (!extra_keep_store)
 266                                 return -1;
 267
 268                         for (i = 0; i < count; i++) {
 269                                 char *v = getenv(extra_keep[i]);
 270                                 if (v) {
 271                                         extra_keep_store[i] = strdup(v);
 272                                         if (!extra_keep_store[i]) {
 273                                                 while (i > 0)
 274                                                         free(extra_keep_store[--i]);
 275
 276                                                 free(extra_keep_store);
 277                                                 return -1;
 278                                         }
 279
 280                                         if (strcmp(extra_keep[i], "PATH") == 0)
 281                                                 path_kept = 1;
 282                                 }
 283                         }
 284                 }
 285
 286                 if (clearenv()) {
 287                         if (extra_keep_store) {
 288                                 char **p;
 289
 290                                 for (p = extra_keep_store; *p; p++)
 291                                         free(*p);
 292
 293                                 free(extra_keep_store);
 294                         }
 295
 296                         return log_error(-1, "Failed to clear environment");
 297                 }
 298
 299                 if (extra_keep_store) {
 300                         size_t i;
 301
 302                         for (i = 0; extra_keep[i]; i++) {
 303                                 if (extra_keep_store[i]) {
 304                                         ret = setenv(extra_keep[i], extra_keep_store[i], 1);
 305                                         if (ret < 0)
 306                                                 SYSWARN("Failed to set environment variable");
 307                                 }
 308
 309                                 free(extra_keep_store[i]);
 310                         }
 311
 312                         free(extra_keep_store);
 313                 }
 314
 315                 /* Always set a default path; shells and execlp tend to be fine
 316                  * without it, but there is a disturbing number of C programs
 317                  * out there that just assume that getenv("PATH") is never NULL
 318                  * and then die a painful segfault death.
 319                  */
 320                 if (!path_kept) {
 321                         ret = setenv("PATH", "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin", 1);
 322                         if (ret < 0)
 323                                 SYSWARN("Failed to set environment variable");
 324                 }
 325         }
 326
 327         ret = putenv("container=lxc");
 328         if (ret < 0)
 329                 return log_warn(-1, "Failed to set environment variable");
 330
 331         /* Set container environment variables.*/
 332         if (init_ctx && init_ctx->container && init_ctx->container->lxc_conf) {
 333                 lxc_list_for_each(iterator, &init_ctx->container->lxc_conf->environment) {
 334                         char *env_tmp;
 335
 336                         env_tmp = strdup((char *)iterator->elem);
 337                         if (!env_tmp)
 338                                 return -1;
 339
 340                         ret = putenv(env_tmp);
 341                         if (ret < 0)
 342                                 return log_error_errno(-1, errno, "Failed to set environment variable: %s", (char *)iterator->elem);
 343                 }
 344         }
 345
 346         /* Set extra environment variables. */
 347         if (extra_env) {
 348                 for (; *extra_env; extra_env++) {
 349                         char *p;
 350
 351                         /* We just assume the user knows what they are doing, so
 352                          * we don't do any checks.
 353                          */
 354                         p = strdup(*extra_env);
 355                         if (!p)
 356                                 return -1;
 357
 358                         ret = putenv(p);
 359                         if (ret < 0)
 360                                 SYSWARN("Failed to set environment variable");
 361                 }
 362         }
 363
 364         return 0;
 365 }
 366
 367 static char *lxc_attach_getpwshell(uid_t uid)
 368 {
 369         __do_free char *line = NULL, *result = NULL;
 370         __do_fclose FILE *pipe_f = NULL;
 371         int fd, ret;
 372         pid_t pid;
 373         int pipes[2];
 374         bool found = false;
 375         size_t line_bufsz = 0;
 376
 377         /* We need to fork off a process that runs the getent program, and we
 378          * need to capture its output, so we use a pipe for that purpose.
 379          */
 380         ret = pipe2(pipes, O_CLOEXEC);
 381         if (ret < 0)
 382                 return NULL;
 383
 384         pid = fork();
 385         if (pid < 0) {
 386                 close(pipes[0]);
 387                 close(pipes[1]);
 388                 return NULL;
 389         }
 390
 391         if (!pid) {
 392                 char uid_buf[32];
 393                 char *arguments[] = {
 394                         "getent",
 395                         "passwd",
 396                         uid_buf,
 397                         NULL
 398                 };
 399
 400                 close(pipes[0]);
 401
 402                 /* We want to capture stdout. */
 403                 ret = dup2(pipes[1], STDOUT_FILENO);
 404                 close(pipes[1]);
 405                 if (ret < 0)
 406                         _exit(EXIT_FAILURE);
 407
 408                 /* Get rid of stdin/stderr, so we try to associate it with
 409                  * /dev/null.
 410                  */
 411                 fd = open_devnull();
 412                 if (fd < 0) {
 413                         close(STDIN_FILENO);
 414                         close(STDERR_FILENO);
 415                 } else {
 416                         (void)dup3(fd, STDIN_FILENO, O_CLOEXEC);
 417                         (void)dup3(fd, STDERR_FILENO, O_CLOEXEC);
 418                         close(fd);
 419                 }
 420
 421                 /* Finish argument list. */
 422                 ret = snprintf(uid_buf, sizeof(uid_buf), "%ld", (long)uid);
 423                 if (ret <= 0 || ret >= sizeof(uid_buf))
 424                         _exit(EXIT_FAILURE);
 425
 426                 /* Try to run getent program. */
 427                 (void)execvp("getent", arguments);
 428                 _exit(EXIT_FAILURE);
 429         }
 430
 431         close(pipes[1]);
 432
 433         pipe_f = fdopen(pipes[0], "re");
 434         if (!pipe_f) {
 435                 close(pipes[0]);
 436                 goto reap_child;
 437         }
 438         /* Transfer ownership of pipes[0] to pipe_f. */
 439         move_fd(pipes[0]);
 440
 441         while (getline(&line, &line_bufsz, pipe_f) != -1) {
 442                 int i;
 443                 long value;
 444                 char *token;
 445                 char *endptr = NULL, *saveptr = NULL;
 446
 447                 /* If we already found something, just continue to read
 448                 * until the pipe doesn't deliver any more data, but
 449                 * don't modify the existing data structure.
 450                  */
 451                 if (found)
 452                         continue;
 453
 454                 if (!line)
 455                         continue;
 456
 457                 /* Trim line on the right hand side. */
 458                 for (i = strlen(line); i > 0 && (line[i - 1] == '\n' || line[i - 1] == '\r'); --i)
 459                         line[i - 1] = '\0';
 460
 461                 /* Split into tokens: first: user name. */
 462                 token = strtok_r(line, ":", &saveptr);
 463                 if (!token)
 464                         continue;
 465
 466                 /* next: dummy password field */
 467                 token = strtok_r(NULL, ":", &saveptr);
 468                 if (!token)
 469                         continue;
 470
 471                 /* next: user id */
 472                 token = strtok_r(NULL, ":", &saveptr);
 473                 value = token ? strtol(token, &endptr, 10) : 0;
 474                 if (!token || !endptr || *endptr || value == LONG_MIN ||
 475                     value == LONG_MAX)
 476                         continue;
 477
 478                 /* dummy sanity check: user id matches */
 479                 if ((uid_t)value != uid)
 480                         continue;
 481
 482                 /* skip fields: gid, gecos, dir, go to next field 'shell' */
 483                 for (i = 0; i < 4; i++) {
 484                         token = strtok_r(NULL, ":", &saveptr);
 485                         if (!token)
 486                                 continue;
 487                 }
 488
 489                 if (!token)
 490                         continue;
 491
 492                 free_disarm(result);
 493                 result = strdup(token);
 494
 495                 /* Sanity check that there are no fields after that. */
 496                 token = strtok_r(NULL, ":", &saveptr);
 497                 if (token)
 498                         continue;
 499
 500                 found = true;
 501         }
 502
 503 reap_child:
 504         ret = wait_for_pid(pid);
 505         if (ret < 0)
 506                 return NULL;
 507
 508         if (!found)
 509                 return NULL;
 510
 511         return move_ptr(result);
 512 }
 513
 514 static void lxc_attach_get_init_uidgid(uid_t *init_uid, gid_t *init_gid)
 515 {
 516         __do_free char *line = NULL;
 517         __do_fclose FILE *proc_file = NULL;
 518         char proc_fn[LXC_PROC_STATUS_LEN];
 519         int ret;
 520         size_t line_bufsz = 0;
 521         long value = -1;
 522         uid_t uid = LXC_INVALID_UID;
 523         gid_t gid = LXC_INVALID_GID;
 524
 525         ret = snprintf(proc_fn, LXC_PROC_STATUS_LEN, "/proc/%d/status", 1);
 526         if (ret < 0 || ret >= LXC_PROC_STATUS_LEN)
 527                 return;
 528
 529         proc_file = fopen(proc_fn, "re");
 530         if (!proc_file)
 531                 return;
 532
 533         while (getline(&line, &line_bufsz, proc_file) != -1) {
 534                 /* Format is: real, effective, saved set user, fs we only care
 535                  * about real uid.
 536                  */
 537                 ret = sscanf(line, "Uid: %ld", &value);
 538                 if (ret != EOF && ret == 1) {
 539                         uid = (uid_t)value;
 540                 } else {
 541                         ret = sscanf(line, "Gid: %ld", &value);
 542                         if (ret != EOF && ret == 1)
 543                                 gid = (gid_t)value;
 544                 }
 545
 546                 if (uid != LXC_INVALID_UID && gid != LXC_INVALID_GID)
 547                         break;
 548         }
 549
 550         /* Only override arguments if we found something. */
 551         if (uid != LXC_INVALID_UID)
 552                 *init_uid = uid;
 553
 554         if (gid != LXC_INVALID_GID)
 555                 *init_gid = gid;
 556
 557         /* TODO: we should also parse supplementary groups and use
 558          * setgroups() to set them.
 559          */
 560 }
 561
 562 static bool fetch_seccomp(struct lxc_container *c, lxc_attach_options_t *options)
 563 {
 564         __do_free char *path = NULL;
 565         int ret;
 566         bool bret;
 567
 568         if (!(options->namespaces & CLONE_NEWNS) ||
 569             !(options->attach_flags & LXC_ATTACH_LSM)) {
 570                 free_disarm(c->lxc_conf->seccomp.seccomp);
 571                 return true;
 572         }
 573
 574         /* Remove current setting. */
 575         if (!c->set_config_item(c, "lxc.seccomp.profile", "") &&
 576             !c->set_config_item(c, "lxc.seccomp", ""))
 577                 return false;
 578
 579         /* Fetch the current profile path over the cmd interface. */
 580         path = c->get_running_config_item(c, "lxc.seccomp.profile");
 581         if (!path) {
 582                 INFO("Failed to retrieve lxc.seccomp.profile");
 583
 584                 path = c->get_running_config_item(c, "lxc.seccomp");
 585                 if (!path)
 586                         return log_info(true, "Failed to retrieve lxc.seccomp");
 587         }
 588
 589         /* Copy the value into the new lxc_conf. */
 590         bret = c->set_config_item(c, "lxc.seccomp.profile", path);
 591         if (!bret)
 592                 return false;
 593
 594         /* Attempt to parse the resulting config. */
 595         ret = lxc_read_seccomp_config(c->lxc_conf);
 596         if (ret < 0)
 597                 return log_error(false, "Failed to retrieve seccomp policy");
 598
 599         return log_info(true, "Retrieved seccomp policy");
 600 }
 601
 602 static bool no_new_privs(struct lxc_container *c, lxc_attach_options_t *options)
 603 {
 604         __do_free char *val = NULL;
 605
 606         /* Remove current setting. */
 607         if (!c->set_config_item(c, "lxc.no_new_privs", ""))
 608                 return log_info(false, "Failed to unset lxc.no_new_privs");
 609
 610         /* Retrieve currently active setting. */
 611         val = c->get_running_config_item(c, "lxc.no_new_privs");
 612         if (!val)
 613                 return log_info(false, "Failed to retrieve lxc.no_new_privs");
 614
 615         /* Set currently active setting. */
 616         return c->set_config_item(c, "lxc.no_new_privs", val);
 617 }
 618
 619 static signed long get_personality(const char *name, const char *lxcpath)
 620 {
 621         __do_free char *p = NULL;
 622
 623         p = lxc_cmd_get_config_item(name, "lxc.arch", lxcpath);
 624         if (!p)
 625                 return -1;
 626
 627         return lxc_config_parse_arch(p);
 628 }
 629
 630 struct attach_clone_payload {
 631         int ipc_socket;
 632         int terminal_slave_fd;
 633         lxc_attach_options_t *options;
 634         struct lxc_proc_context_info *init_ctx;
 635         lxc_attach_exec_t exec_function;
 636         void *exec_payload;
 637 };
 638
 639 static void lxc_put_attach_clone_payload(struct attach_clone_payload *p)
 640 {
 641         close_prot_errno_disarm(p->ipc_socket);
 642         close_prot_errno_disarm(p->terminal_slave_fd);
 643         if (p->init_ctx) {
 644                 lxc_proc_put_context_info(p->init_ctx);
 645                 p->init_ctx = NULL;
 646         }
 647 }
 648
 649 static int attach_child_main(struct attach_clone_payload *payload)
 650 {
 651         int lsm_fd, ret;
 652         uid_t new_uid;
 653         gid_t new_gid;
 654         uid_t ns_root_uid = 0;
 655         gid_t ns_root_gid = 0;
 656         lxc_attach_options_t* options = payload->options;
 657         struct lxc_proc_context_info* init_ctx = payload->init_ctx;
 658         bool needs_lsm = (options->namespaces & CLONE_NEWNS) &&
 659                          (options->attach_flags & LXC_ATTACH_LSM) &&
 660                          init_ctx->lsm_label;
 661
 662         /* A description of the purpose of this functionality is provided in the
 663          * lxc-attach(1) manual page. We have to remount here and not in the
 664          * parent process, otherwise /proc may not properly reflect the new pid
 665          * namespace.
 666          */
 667         if (!(options->namespaces & CLONE_NEWNS) &&
 668             (options->attach_flags & LXC_ATTACH_REMOUNT_PROC_SYS)) {
 669                 ret = lxc_attach_remount_sys_proc();
 670                 if (ret < 0)
 671                         goto on_error;
 672
 673                 TRACE("Remounted \"/proc\" and \"/sys\"");
 674         }
 675
 676 /* Now perform additional attachments. */
 677 #if HAVE_SYS_PERSONALITY_H
 678         if (options->attach_flags & LXC_ATTACH_SET_PERSONALITY) {
 679                 long new_personality;
 680
 681                 if (options->personality < 0)
 682                         new_personality = init_ctx->personality;
 683                 else
 684                         new_personality = options->personality;
 685
 686                 ret = personality(new_personality);
 687                 if (ret < 0)
 688                         goto on_error;
 689
 690                 TRACE("Set new personality");
 691         }
 692 #endif
 693
 694         if (options->attach_flags & LXC_ATTACH_DROP_CAPABILITIES) {
 695                 ret = lxc_attach_drop_privs(init_ctx);
 696                 if (ret < 0)
 697                         goto on_error;
 698
 699                 TRACE("Dropped capabilities");
 700         }
 701
 702         /* Always set the environment (specify (LXC_ATTACH_KEEP_ENV, NULL, NULL)
 703          * if you want this to be a no-op).
 704          */
 705         ret = lxc_attach_set_environment(init_ctx,
 706                                          options->env_policy,
 707                                          options->extra_env_vars,
 708                                          options->extra_keep_env);
 709         if (ret < 0)
 710                 goto on_error;
 711
 712         TRACE("Set up environment");
 713
 714         /* This remark only affects fully unprivileged containers:
 715          * Receive fd for LSM security module before we set{g,u}id(). The reason
 716          * is that on set{g,u}id() the kernel will a) make us undumpable and b)
 717          * we will change our effective uid. This means our effective uid will
 718          * be different from the effective uid of the process that created us
 719          * which means that this processs no longer has capabilities in our
 720          * namespace including CAP_SYS_PTRACE. This means we will not be able to
 721          * read and /proc/<pid> files for the process anymore when /proc is
 722          * mounted with hidepid={1,2}. So let's get the lsm label fd before the
 723          * set{g,u}id().
 724          */
 725         if (needs_lsm) {
 726                 ret = lxc_abstract_unix_recv_fds(payload->ipc_socket, &lsm_fd, 1, NULL, 0);
 727                 if (ret <= 0) {
 728                         if (ret < 0)
 729                                 SYSERROR("Failed to receive lsm label fd");
 730
 731                         goto on_error;
 732                 }
 733
 734                 TRACE("Received LSM label file descriptor %d from parent", lsm_fd);
 735         }
 736
 737         if (options->stdin_fd > 0 && isatty(options->stdin_fd)) {
 738                 ret = lxc_make_controlling_terminal(options->stdin_fd);
 739                 if (ret < 0)
 740                         goto on_error;
 741         }
 742
 743         if (!lxc_setgroups(0, NULL) && errno != EPERM)
 744                 goto on_error;
 745
 746         if (options->namespaces & CLONE_NEWUSER) {
 747                 /* Check whether nsuid 0 has a mapping. */
 748                 ns_root_uid = get_ns_uid(0);
 749
 750                 /* Check whether nsgid 0 has a mapping. */
 751                 ns_root_gid = get_ns_gid(0);
 752
 753                 /* If there's no mapping for nsuid 0 try to retrieve the nsuid
 754                  * init was started with.
 755                  */
 756                 if (ns_root_uid == LXC_INVALID_UID)
 757                         lxc_attach_get_init_uidgid(&ns_root_uid, &ns_root_gid);
 758
 759                 if (ns_root_uid == LXC_INVALID_UID)
 760                         goto on_error;
 761
 762                 if (!lxc_switch_uid_gid(ns_root_uid, ns_root_gid))
 763                         goto on_error;
 764         }
 765
 766         /* Set {u,g}id. */
 767         if (options->uid != LXC_INVALID_UID)
 768                 new_uid = options->uid;
 769         else
 770                 new_uid = ns_root_uid;
 771
 772         if (options->gid != LXC_INVALID_GID)
 773                 new_gid = options->gid;
 774         else
 775                 new_gid = ns_root_gid;
 776
 777         if ((init_ctx->container && init_ctx->container->lxc_conf &&
 778              init_ctx->container->lxc_conf->no_new_privs) ||
 779             (options->attach_flags & LXC_ATTACH_NO_NEW_PRIVS)) {
 780                 ret = prctl(PR_SET_NO_NEW_PRIVS, prctl_arg(1), prctl_arg(0),
 781                             prctl_arg(0), prctl_arg(0));
 782                 if (ret < 0)
 783                         goto on_error;
 784
 785                 TRACE("Set PR_SET_NO_NEW_PRIVS");
 786         }
 787
 788         if (needs_lsm) {
 789                 bool on_exec;
 790
 791                 /* Change into our new LSM profile. */
 792                 on_exec = options->attach_flags & LXC_ATTACH_LSM_EXEC ? true : false;
 793
 794                 ret = lsm_process_label_set_at(lsm_fd, init_ctx->lsm_label, on_exec);
 795                 close(lsm_fd);
 796                 if (ret < 0)
 797                         goto on_error;
 798
 799                 TRACE("Set %s LSM label to \"%s\"", lsm_name(), init_ctx->lsm_label);
 800         }
 801
 802         if (init_ctx->container && init_ctx->container->lxc_conf &&
 803             init_ctx->container->lxc_conf->seccomp.seccomp) {
 804                 struct lxc_conf *conf = init_ctx->container->lxc_conf;
 805
 806                 ret = lxc_seccomp_load(conf);
 807                 if (ret < 0)
 808                         goto on_error;
 809
 810                 TRACE("Loaded seccomp profile");
 811
 812                 ret = lxc_seccomp_send_notifier_fd(&conf->seccomp, payload->ipc_socket);
 813                 if (ret < 0)
 814                         goto on_error;
 815         }
 816
 817         close(payload->ipc_socket);
 818         payload->ipc_socket = -EBADF;
 819         lxc_proc_put_context_info(init_ctx);
 820         payload->init_ctx = NULL;
 821
 822         /* The following is done after the communication socket is shut down.
 823          * That way, all errors that might (though unlikely) occur up until this
 824          * point will have their messages printed to the original stderr (if
 825          * logging is so configured) and not the fd the user supplied, if any.
 826          */
 827
 828         /* Fd handling for stdin, stdout and stderr; ignore errors here, user
 829          * may want to make sure the fds are closed, for example.
 830          */
 831         if (options->stdin_fd >= 0 && options->stdin_fd != STDIN_FILENO)
 832                 (void)dup2(options->stdin_fd, STDIN_FILENO);
 833
 834         if (options->stdout_fd >= 0 && options->stdout_fd != STDOUT_FILENO)
 835                 (void)dup2(options->stdout_fd, STDOUT_FILENO);
 836
 837         if (options->stderr_fd >= 0 && options->stderr_fd != STDERR_FILENO)
 838                 (void)dup2(options->stderr_fd, STDERR_FILENO);
 839
 840         /* close the old fds */
 841         if (options->stdin_fd > STDERR_FILENO)
 842                 close(options->stdin_fd);
 843
 844         if (options->stdout_fd > STDERR_FILENO)
 845                 close(options->stdout_fd);
 846
 847         if (options->stderr_fd > STDERR_FILENO)
 848                 close(options->stderr_fd);
 849
 850         /*
 851          * Try to remove FD_CLOEXEC flag from stdin/stdout/stderr, but also
 852          * here, ignore errors.
 853          */
 854         for (int fd = STDIN_FILENO; fd <= STDERR_FILENO; fd++) {
 855                 ret = fd_cloexec(fd, false);
 856                 if (ret < 0) {
 857                         SYSERROR("Failed to clear FD_CLOEXEC from file descriptor %d", fd);
 858                         goto on_error;
 859                 }
 860         }
 861
 862         if (options->attach_flags & LXC_ATTACH_TERMINAL) {
 863                 ret = lxc_terminal_prepare_login(payload->terminal_slave_fd);
 864                 if (ret < 0) {
 865                         SYSERROR("Failed to prepare terminal file descriptor %d", payload->terminal_slave_fd);
 866                         goto on_error;
 867                 }
 868
 869                 TRACE("Prepared terminal file descriptor %d", payload->terminal_slave_fd);
 870         }
 871
 872         /* Avoid unnecessary syscalls. */
 873         if (new_uid == ns_root_uid)
 874                 new_uid = LXC_INVALID_UID;
 875
 876         if (new_gid == ns_root_gid)
 877                 new_gid = LXC_INVALID_GID;
 878
 879         /* Make sure that the processes STDIO is correctly owned by the user that we are switching to */
 880         fix_stdio_permissions(new_uid);
 881
 882         if (!lxc_switch_uid_gid(new_uid, new_gid))
 883                 goto on_error;
 884
 885         /* We're done, so we can now do whatever the user intended us to do. */
 886         _exit(payload->exec_function(payload->exec_payload));
 887
 888 on_error:
 889         lxc_put_attach_clone_payload(payload);
 890         _exit(EXIT_FAILURE);
 891 }
 892
 893 static int lxc_attach_terminal(struct lxc_conf *conf,
 894                                struct lxc_terminal *terminal)
 895 {
 896         int ret;
 897
 898         lxc_terminal_init(terminal);
 899
 900         ret = lxc_terminal_create(terminal);
 901         if (ret < 0)
 902                 return log_error(-1, "Failed to create terminal");
 903
 904         /* Shift ttys to container. */
 905         ret = lxc_terminal_map_ids(conf, terminal);
 906         if (ret < 0) {
 907                 ERROR("Failed to chown terminal");
 908                 goto on_error;
 909         }
 910
 911         return 0;
 912
 913 on_error:
 914         lxc_terminal_delete(terminal);
 915         lxc_terminal_conf_free(terminal);
 916         return -1;
 917 }
 918
 919 static int lxc_attach_terminal_mainloop_init(struct lxc_terminal *terminal,
 920                                              struct lxc_epoll_descr *descr)
 921 {
 922         int ret;
 923
 924         ret = lxc_mainloop_open(descr);
 925         if (ret < 0)
 926                 return log_error(-1, "Failed to create mainloop");
 927
 928         ret = lxc_terminal_mainloop_add(descr, terminal);
 929         if (ret < 0) {
 930                 lxc_mainloop_close(descr);
 931                 return log_error(-1, "Failed to add handlers to mainloop");
 932         }
 933
 934         return 0;
 935 }
 936
 937 static inline void lxc_attach_terminal_close_master(struct lxc_terminal *terminal)
 938 {
 939         close_prot_errno_disarm(terminal->master);
 940 }
 941
 942 static inline void lxc_attach_terminal_close_slave(struct lxc_terminal *terminal)
 943 {
 944         close_prot_errno_disarm(terminal->slave);
 945 }
 946
 947 static inline void lxc_attach_terminal_close_peer(struct lxc_terminal *terminal)
 948 {
 949         close_prot_errno_disarm(terminal->peer);
 950 }
 951
 952 static inline void lxc_attach_terminal_close_log(struct lxc_terminal *terminal)
 953 {
 954         close_prot_errno_disarm(terminal->log_fd);
 955 }
 956
 957 int lxc_attach(struct lxc_container *container, lxc_attach_exec_t exec_function,
 958                void *exec_payload, lxc_attach_options_t *options,
 959                pid_t *attached_process)
 960 {
 961         int i, ret, status;
 962         int ipc_sockets[2];
 963         char *cwd, *new_cwd;
 964         signed long personality;
 965         pid_t attached_pid, init_pid, pid;
 966         struct lxc_proc_context_info *init_ctx;
 967         struct lxc_terminal terminal;
 968         struct lxc_conf *conf;
 969         char *name, *lxcpath;
 970         struct attach_clone_payload payload = {0};
 971
 972         ret = access("/proc/self/ns", X_OK);
 973         if (ret)
 974                 return log_error_errno(-1, errno, "Does this kernel version support namespaces?");
 975
 976         if (!container)
 977                 return ret_set_errno(-1, EINVAL);
 978
 979         if (!lxc_container_get(container))
 980                 return ret_set_errno(-1, EINVAL);
 981
 982         name = container->name;
 983         lxcpath = container->config_path;
 984
 985         if (!options)
 986                 options = &attach_static_default_options;
 987
 988         init_pid = lxc_cmd_get_init_pid(name, lxcpath);
 989         if (init_pid < 0) {
 990                 lxc_container_put(container);
 991                 return log_error(-1, "Failed to get init pid");
 992         }
 993
 994         init_ctx = lxc_proc_get_context_info(init_pid);
 995         if (!init_ctx) {
 996                 ERROR("Failed to get context of init process: %ld", (long)init_pid);
 997                 lxc_container_put(container);
 998                 return -1;
 999         }
1000
1001         init_ctx->container = container;
1002
1003         personality = get_personality(name, lxcpath);
1004         if (init_ctx->personality < 0) {
1005                 ERROR("Failed to get personality of the container");
1006                 lxc_proc_put_context_info(init_ctx);
1007                 return -1;
1008         }
1009         init_ctx->personality = personality;
1010
1011         if (!init_ctx->container->lxc_conf) {
1012                 init_ctx->container->lxc_conf = lxc_conf_init();
1013                 if (!init_ctx->container->lxc_conf) {
1014                         lxc_proc_put_context_info(init_ctx);
1015                         return -1;
1016                 }
1017         }
1018         conf = init_ctx->container->lxc_conf;
1019
1020         if (!fetch_seccomp(init_ctx->container, options))
1021                 WARN("Failed to get seccomp policy");
1022
1023         if (!no_new_privs(init_ctx->container, options))
1024                 WARN("Could not determine whether PR_SET_NO_NEW_PRIVS is set");
1025
1026         cwd = getcwd(NULL, 0);
1027
1028         /* Determine which namespaces the container was created with
1029          * by asking lxc-start, if necessary.
1030          */
1031         if (options->namespaces == -1) {
1032                 options->namespaces = lxc_cmd_get_clone_flags(name, lxcpath);
1033                 /* call failed */
1034                 if (options->namespaces == -1) {
1035                         ERROR("Failed to automatically determine the "
1036                               "namespaces which the container uses");
1037                         free(cwd);
1038                         lxc_proc_put_context_info(init_ctx);
1039                         return -1;
1040                 }
1041
1042                 for (i = 0; i < LXC_NS_MAX; i++) {
1043                         if (ns_info[i].clone_flag & CLONE_NEWCGROUP)
1044                                 if (!(options->attach_flags & LXC_ATTACH_MOVE_TO_CGROUP) ||
1045                                     !cgns_supported())
1046                                         continue;
1047
1048                         if (ns_info[i].clone_flag & options->namespaces)
1049                                 continue;
1050
1051                         init_ctx->ns_inherited |= ns_info[i].clone_flag;
1052                 }
1053         }
1054
1055         pid = lxc_raw_getpid();
1056
1057         for (i = 0; i < LXC_NS_MAX; i++) {
1058                 int j;
1059
1060                 if (options->namespaces & ns_info[i].clone_flag)
1061                         init_ctx->ns_fd[i] = lxc_preserve_ns(init_pid, ns_info[i].proc_name);
1062                 else if (init_ctx->ns_inherited & ns_info[i].clone_flag)
1063                         init_ctx->ns_fd[i] = in_same_namespace(pid, init_pid, ns_info[i].proc_name);
1064                 else
1065                         continue;
1066
1067                 if (init_ctx->ns_fd[i] >= 0)
1068                         continue;
1069
1070                 if (init_ctx->ns_fd[i] == -EINVAL) {
1071                         DEBUG("Inheriting %s namespace from %d",
1072                               ns_info[i].proc_name, pid);
1073                         init_ctx->ns_inherited &= ~ns_info[i].clone_flag;
1074                         continue;
1075                 }
1076
1077                 /* We failed to preserve the namespace. */
1078                 SYSERROR("Failed to attach to %s namespace of %d",
1079                          ns_info[i].proc_name, pid);
1080
1081                 /* Close all already opened file descriptors before we return an
1082                  * error, so we don't leak them.
1083                  */
1084                 for (j = 0; j < i; j++)
1085                         close(init_ctx->ns_fd[j]);
1086
1087                 free(cwd);
1088                 lxc_proc_put_context_info(init_ctx);
1089                 return -1;
1090         }
1091
1092         if (options->attach_flags & LXC_ATTACH_TERMINAL) {
1093                 ret = lxc_attach_terminal(conf, &terminal);
1094                 if (ret < 0) {
1095                         ERROR("Failed to setup new terminal");
1096                         free(cwd);
1097                         lxc_proc_put_context_info(init_ctx);
1098                         return -1;
1099                 }
1100
1101                 terminal.log_fd = options->log_fd;
1102         } else {
1103                 lxc_terminal_init(&terminal);
1104         }
1105
1106         /* Create a socket pair for IPC communication; set SOCK_CLOEXEC in order
1107          * to make sure we don't irritate other threads that want to fork+exec
1108          * away
1109          *
1110          * IMPORTANT: if the initial process is multithreaded and another call
1111          * just fork()s away without exec'ing directly after, the socket fd will
1112          * exist in the forked process from the other thread and any close() in
1113          * our own child process will not really cause the socket to close
1114          * properly, potentially causing the parent to hang.
1115          *
1116          * For this reason, while IPC is still active, we have to use shutdown()
1117          * if the child exits prematurely in order to signal that the socket is
1118          * closed and cannot assume that the child exiting will automatically do
1119          * that.
1120          *
1121          * IPC mechanism: (X is receiver)
1122          *   initial process        intermediate          attached
1123          *        X           <---  send pid of
1124          *                          attached proc,
1125          *                          then exit
1126          *    send 0 ------------------------------------>    X
1127          *                                              [do initialization]
1128          *        X  <------------------------------------  send 1
1129          *   [add to cgroup, ...]
1130          *    send 2 ------------------------------------>    X
1131          *                                              [set LXC_ATTACH_NO_NEW_PRIVS]
1132          *        X  <------------------------------------  send 3
1133          *   [open LSM label fd]
1134          *    send 4 ------------------------------------>    X
1135          *                                              [set LSM label]
1136          *   close socket                                 close socket
1137          *                                                run program
1138          */
1139         ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
1140         if (ret < 0) {
1141                 SYSERROR("Could not set up required IPC mechanism for attaching");
1142                 free(cwd);
1143                 lxc_proc_put_context_info(init_ctx);
1144                 return -1;
1145         }
1146
1147         /* Create intermediate subprocess, two reasons:
1148          *       1. We can't setns() in the child itself, since we want to make
1149          *          sure we are properly attached to the pidns.
1150          *       2. Also, the initial thread has to put the attached process
1151          *          into the cgroup, which we can only do if we didn't already
1152          *          setns() (otherwise, user namespaces will hate us).
1153          */
1154         pid = fork();
1155         if (pid < 0) {
1156                 SYSERROR("Failed to create first subprocess");
1157                 free(cwd);
1158                 lxc_proc_put_context_info(init_ctx);
1159                 return -1;
1160         }
1161
1162         if (pid) {
1163                 int ret_parent = -1;
1164                 pid_t to_cleanup_pid = pid;
1165                 struct lxc_epoll_descr descr = {0};
1166
1167                 /* close unneeded file descriptors */
1168                 close(ipc_sockets[1]);
1169                 free(cwd);
1170                 lxc_proc_close_ns_fd(init_ctx);
1171                 if (options->attach_flags & LXC_ATTACH_TERMINAL)
1172                         lxc_attach_terminal_close_slave(&terminal);
1173
1174                 /* Attach to cgroup, if requested. */
1175                 if (options->attach_flags & LXC_ATTACH_MOVE_TO_CGROUP) {
1176                         /*
1177                          * If this is the unified hierarchy cgroup_attach() is
1178                          * enough.
1179                          */
1180                         ret = cgroup_attach(conf, name, lxcpath, pid);
1181                         if (ret) {
1182                                 call_cleaner(cgroup_exit) struct cgroup_ops *cgroup_ops = NULL;
1183
1184                                 cgroup_ops = cgroup_init(conf);
1185                                 if (!cgroup_ops)
1186                                         goto on_error;
1187
1188                                 if (!cgroup_ops->attach(cgroup_ops, conf, name, lxcpath, pid))
1189                                         goto on_error;
1190                         }
1191                         TRACE("Moved intermediate process %d into container's cgroups", pid);
1192                 }
1193
1194                 /* Setup /proc limits */
1195                 if (!lxc_list_empty(&conf->procs)) {
1196                         ret = setup_proc_filesystem(&conf->procs, pid);
1197                         if (ret < 0)
1198                                 goto on_error;
1199                 }
1200
1201                 /* Setup resource limits */
1202                 if (!lxc_list_empty(&conf->limits)) {
1203                         ret = setup_resource_limits(&conf->limits, pid);
1204                         if (ret < 0)
1205                                 goto on_error;
1206                 }
1207
1208                 if (options->attach_flags & LXC_ATTACH_TERMINAL) {
1209                         ret = lxc_attach_terminal_mainloop_init(&terminal, &descr);
1210                         if (ret < 0)
1211                                 goto on_error;
1212
1213                         TRACE("Initialized terminal mainloop");
1214                 }
1215
1216                 /* Let the child process know to go ahead. */
1217                 status = 0;
1218                 ret = lxc_write_nointr(ipc_sockets[0], &status, sizeof(status));
1219                 if (ret != sizeof(status))
1220                         goto close_mainloop;
1221
1222                 TRACE("Told intermediate process to start initializing");
1223
1224                 /* Get pid of attached process from intermediate process. */
1225                 ret = lxc_read_nointr(ipc_sockets[0], &attached_pid, sizeof(attached_pid));
1226                 if (ret != sizeof(attached_pid))
1227                         goto close_mainloop;
1228
1229                 TRACE("Received pid %d of attached process in parent pid namespace", attached_pid);
1230
1231                 /* Ignore SIGKILL (CTRL-C) and SIGQUIT (CTRL-\) - issue #313. */
1232                 if (options->stdin_fd == 0) {
1233                         signal(SIGINT, SIG_IGN);
1234                         signal(SIGQUIT, SIG_IGN);
1235                 }
1236
1237                 /* Reap intermediate process. */
1238                 ret = wait_for_pid(pid);
1239                 if (ret < 0)
1240                         goto close_mainloop;
1241
1242                 TRACE("Intermediate process %d exited", pid);
1243
1244                 /* We will always have to reap the attached process now. */
1245                 to_cleanup_pid = attached_pid;
1246
1247                 /* Open LSM fd and send it to child. */
1248                 if ((options->namespaces & CLONE_NEWNS) &&
1249                     (options->attach_flags & LXC_ATTACH_LSM) &&
1250                     init_ctx->lsm_label) {
1251                         int labelfd;
1252                         bool on_exec;
1253
1254                         ret = -1;
1255                         on_exec = options->attach_flags & LXC_ATTACH_LSM_EXEC ? true : false;
1256                         labelfd = lsm_process_label_fd_get(attached_pid, on_exec);
1257                         if (labelfd < 0)
1258                                 goto close_mainloop;
1259
1260                         TRACE("Opened LSM label file descriptor %d", labelfd);
1261
1262                         /* Send child fd of the LSM security module to write to. */
1263                         ret = lxc_abstract_unix_send_fds(ipc_sockets[0], &labelfd, 1, NULL, 0);
1264                         if (ret <= 0) {
1265                                 if (ret < 0)
1266                                         SYSERROR("Failed to send lsm label fd");
1267
1268                                 close(labelfd);
1269                                 goto close_mainloop;
1270                         }
1271
1272                         close(labelfd);
1273                         TRACE("Sent LSM label file descriptor %d to child", labelfd);
1274                 }
1275
1276                 if (conf && conf->seccomp.seccomp) {
1277                         ret = lxc_seccomp_recv_notifier_fd(&conf->seccomp, ipc_sockets[0]);
1278                         if (ret < 0)
1279                                 goto close_mainloop;
1280
1281                         ret = lxc_seccomp_add_notifier(name, lxcpath, &conf->seccomp);
1282                         if (ret < 0)
1283                                 goto close_mainloop;
1284                 }
1285
1286                 /* We're done, the child process should now execute whatever it
1287                  * is that the user requested. The parent can now track it with
1288                  * waitpid() or similar.
1289                  */
1290
1291                 *attached_process = attached_pid;
1292
1293                 /* Now shut down communication with child, we're done. */
1294                 shutdown(ipc_sockets[0], SHUT_RDWR);
1295                 close(ipc_sockets[0]);
1296                 ipc_sockets[0] = -1;
1297
1298                 ret_parent = 0;
1299                 to_cleanup_pid = -1;
1300
1301                 if (options->attach_flags & LXC_ATTACH_TERMINAL) {
1302                         ret = lxc_mainloop(&descr, -1);
1303                         if (ret < 0) {
1304                                 ret_parent = -1;
1305                                 to_cleanup_pid = attached_pid;
1306                         }
1307                 }
1308
1309         close_mainloop:
1310                 if (options->attach_flags & LXC_ATTACH_TERMINAL)
1311                         lxc_mainloop_close(&descr);
1312
1313         on_error:
1314                 if (ipc_sockets[0] >= 0) {
1315                         shutdown(ipc_sockets[0], SHUT_RDWR);
1316                         close(ipc_sockets[0]);
1317                 }
1318
1319                 if (to_cleanup_pid > 0)
1320                         (void)wait_for_pid(to_cleanup_pid);
1321
1322                 if (options->attach_flags & LXC_ATTACH_TERMINAL) {
1323                         lxc_terminal_delete(&terminal);
1324                         lxc_terminal_conf_free(&terminal);
1325                 }
1326
1327                 lxc_proc_put_context_info(init_ctx);
1328                 return ret_parent;
1329         }
1330
1331         /* close unneeded file descriptors */
1332         close_prot_errno_disarm(ipc_sockets[0]);
1333
1334         if (options->attach_flags & LXC_ATTACH_TERMINAL) {
1335                 lxc_attach_terminal_close_master(&terminal);
1336                 lxc_attach_terminal_close_peer(&terminal);
1337                 lxc_attach_terminal_close_log(&terminal);
1338         }
1339
1340         /* Wait for the parent to have setup cgroups. */
1341         ret = lxc_read_nointr(ipc_sockets[1], &status, sizeof(status));
1342         if (ret != sizeof(status)) {
1343                 shutdown(ipc_sockets[1], SHUT_RDWR);
1344                 lxc_proc_put_context_info(init_ctx);
1345                 _exit(EXIT_FAILURE);
1346         }
1347
1348         TRACE("Intermediate process starting to initialize");
1349
1350         /* Attach now, create another subprocess later, since pid namespaces
1351          * only really affect the children of the current process.
1352          */
1353         ret = lxc_attach_to_ns(init_pid, init_ctx);
1354         if (ret < 0) {
1355                 ERROR("Failed to enter namespaces");
1356                 shutdown(ipc_sockets[1], SHUT_RDWR);
1357                 lxc_proc_put_context_info(init_ctx);
1358                 _exit(EXIT_FAILURE);
1359         }
1360
1361         /* close namespace file descriptors */
1362         lxc_proc_close_ns_fd(init_ctx);
1363
1364         /* Attach succeeded, try to cwd. */
1365         if (options->initial_cwd)
1366                 new_cwd = options->initial_cwd;
1367         else
1368                 new_cwd = cwd;
1369         if (new_cwd) {
1370                 ret = chdir(new_cwd);
1371                 if (ret < 0)
1372                         WARN("Could not change directory to \"%s\"", new_cwd);
1373         }
1374         free(cwd);
1375
1376         /* Create attached process. */
1377         payload.ipc_socket = ipc_sockets[1];
1378         payload.options = options;
1379         payload.init_ctx = init_ctx;
1380         payload.terminal_slave_fd = terminal.slave;
1381         payload.exec_function = exec_function;
1382         payload.exec_payload = exec_payload;
1383
1384         pid = lxc_raw_clone(CLONE_PARENT, NULL);
1385         if (pid < 0) {
1386                 SYSERROR("Failed to clone attached process");
1387                 shutdown(ipc_sockets[1], SHUT_RDWR);
1388                 lxc_proc_put_context_info(init_ctx);
1389                 _exit(EXIT_FAILURE);
1390         }
1391
1392         if (pid == 0) {
1393                 if (options->attach_flags & LXC_ATTACH_TERMINAL) {
1394                         ret = pthread_sigmask(SIG_SETMASK,
1395                                               &terminal.tty_state->oldmask, NULL);
1396                         if (ret < 0) {
1397                                 SYSERROR("Failed to reset signal mask");
1398                                 _exit(EXIT_FAILURE);
1399                         }
1400                 }
1401
1402                 ret = attach_child_main(&payload);
1403                 if (ret < 0)
1404                         ERROR("Failed to exec");
1405
1406                 _exit(EXIT_FAILURE);
1407         }
1408
1409         if (options->attach_flags & LXC_ATTACH_TERMINAL)
1410                 lxc_attach_terminal_close_slave(&terminal);
1411
1412         /* Tell grandparent the pid of the pid of the newly created child. */
1413         ret = lxc_write_nointr(ipc_sockets[1], &pid, sizeof(pid));
1414         if (ret != sizeof(pid)) {
1415                 /* If this really happens here, this is very unfortunate, since
1416                  * the parent will not know the pid of the attached process and
1417                  * will not be able to wait for it (and we won't either due to
1418                  * CLONE_PARENT) so the parent won't be able to reap it and the
1419                  * attached process will remain a zombie.
1420                  */
1421                 shutdown(ipc_sockets[1], SHUT_RDWR);
1422                 lxc_proc_put_context_info(init_ctx);
1423                 _exit(EXIT_FAILURE);
1424         }
1425
1426         TRACE("Sending pid %d of attached process", pid);
1427
1428         /* The rest is in the hands of the initial and the attached process. */
1429         lxc_proc_put_context_info(init_ctx);
1430         _exit(EXIT_SUCCESS);
1431 }
1432
1433 int lxc_attach_run_command(void *payload)
1434 {
1435         int ret = -1;
1436         lxc_attach_command_t *cmd = payload;
1437
1438         ret = execvp(cmd->program, cmd->argv);
1439         if (ret < 0) {
1440                 switch (errno) {
1441                 case ENOEXEC:
1442                         ret = 126;
1443                         break;
1444                 case ENOENT:
1445                         ret = 127;
1446                         break;
1447                 }
1448         }
1449
1450         return log_error_errno(ret, errno, "Failed to exec \"%s\"", cmd->program);
1451 }
1452
1453 int lxc_attach_run_shell(void* payload)
1454 {
1455         __do_free char *buf = NULL;
1456         uid_t uid;
1457         struct passwd pwent;
1458         struct passwd *pwentp = NULL;
1459         char *user_shell;
1460         size_t bufsize;
1461         int ret;
1462
1463         /* Ignore payload parameter. */
1464         (void)payload;
1465
1466         uid = getuid();
1467
1468         bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
1469         if (bufsize == -1)
1470                 bufsize = 1024;
1471
1472         buf = malloc(bufsize);
1473         if (buf) {
1474                 ret = getpwuid_r(uid, &pwent, buf, bufsize, &pwentp);
1475                 if (!pwentp) {
1476                         if (ret == 0)
1477                                 WARN("Could not find matched password record");
1478
1479                         WARN("Failed to get password record - %u", uid);
1480                 }
1481         }
1482
1483         /* This probably happens because of incompatible nss implementations in
1484          * host and container (remember, this code is still using the host's
1485          * glibc but our mount namespace is in the container) we may try to get
1486          * the information by spawning a [getent passwd uid] process and parsing
1487          * the result.
1488          */
1489         if (!pwentp)
1490                 user_shell = lxc_attach_getpwshell(uid);
1491         else
1492                 user_shell = pwent.pw_shell;
1493
1494         if (user_shell)
1495                 execlp(user_shell, user_shell, (char *)NULL);
1496
1497         /* Executed if either no passwd entry or execvp fails, we will fall back
1498          * on /bin/sh as a default shell.
1499          */
1500         execlp("/bin/sh", "/bin/sh", (char *)NULL);
1501
1502         SYSERROR("Failed to execute shell");
1503         if (!pwentp)
1504                 free(user_shell);
1505
1506         return -1;
1507 }