--- /dev/null
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ This file is part of systemd.
+
+ Copyright 2010 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <signal.h>
+#include <sched.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/syscall.h>
+#include <sys/mount.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <errno.h>
+#include <sys/prctl.h>
+#include <sys/capability.h>
+#include <getopt.h>
+
+#include "log.h"
+#include "util.h"
+
+static char *arg_directory = NULL;
+
+static int help(void) {
+
+ printf("%s [OPTIONS...] [PATH] [ARGUMENTS...]\n\n"
+ "Spawn a minimal namespace container for debugging, testing and building.\n\n"
+ " -h --help Show this help\n"
+ " -D --directory=NAME Root directory for the container\n",
+ program_invocation_short_name);
+
+ return 0;
+}
+
+static int parse_argv(int argc, char *argv[]) {
+
+ static const struct option options[] = {
+ { "help", no_argument, NULL, 'h' },
+ { "directory", required_argument, NULL, 'D' },
+ { NULL, 0, NULL, 0 }
+ };
+
+ int c;
+
+ assert(argc >= 0);
+ assert(argv);
+
+ while ((c = getopt_long(argc, argv, "+hD:", options, NULL)) >= 0) {
+
+ switch (c) {
+
+ case 'h':
+ help();
+ return 0;
+
+ case 'D':
+ free(arg_directory);
+ if (!(arg_directory = strdup(optarg))) {
+ log_error("Failed to duplicate root directory.");
+ return -ENOMEM;
+ }
+
+ break;
+
+ case '?':
+ return -EINVAL;
+
+ default:
+ log_error("Unknown option code %c", c);
+ return -EINVAL;
+ }
+ }
+
+ return 1;
+}
+
+static int mount_all(const char *dest) {
+
+ typedef struct MountPoint {
+ const char *what;
+ const char *where;
+ const char *type;
+ const char *options;
+ unsigned long flags;
+ } MountPoint;
+
+ static const MountPoint mount_table[] = {
+ { "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV },
+ { "/proc/sys", "/proc/sys", "bind", NULL, MS_BIND }, /* Bind mount first */
+ { "/proc/sys", "/proc/sys", "bind", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT }, /* Then, make it r/o */
+ { "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY },
+ { "tmpfs", "/dev", "tmpfs", "mode=755", MS_NOSUID },
+ { "/dev/pts", "/dev/pts", "bind", NULL, MS_BIND },
+ { "tmpfs", "/dev/.run", "tmpfs", "mode=755", MS_NOSUID|MS_NOEXEC|MS_NODEV },
+ };
+
+ unsigned k;
+ int r = 0;
+
+ for (k = 0; k < ELEMENTSOF(mount_table); k++) {
+ char *where;
+ int t;
+
+ if (asprintf(&where, "%s/%s", dest, mount_table[k].where) < 0) {
+ log_error("Out of memory");
+
+ if (r == 0)
+ r = -ENOMEM;
+
+ break;
+ }
+
+ if ((t = path_is_mount_point(where)) < 0) {
+ log_error("Failed to detect whether %s is a mount point: %s", where, strerror(-t));
+ free(where);
+
+ if (r == 0)
+ r = t;
+
+ continue;
+ }
+
+ mkdir_p(where, 0755);
+
+ if (mount(mount_table[k].what,
+ where,
+ mount_table[k].type,
+ mount_table[k].flags,
+ mount_table[k].options) < 0) {
+
+ log_error("mount(%s) failed: %m", where);
+
+ if (r == 0)
+ r = -errno;
+ }
+
+ free(where);
+ }
+
+ return r;
+}
+
+static int copy_devnodes(const char *dest) {
+
+ static const char devnodes[] =
+ "null\0"
+ "zero\0"
+ "full\0"
+ "random\0"
+ "urandom\0"
+ "tty\0"
+ "ptmx\0"
+ "kmsg\0"
+ "rtc0\0";
+
+ const char *d;
+ int r = 0, k;
+ char *tty = NULL;
+ dev_t tty_devnum;
+
+ NULSTR_FOREACH(d, devnodes) {
+ char *from = NULL, *to = NULL;
+ struct stat st;
+
+ asprintf(&from, "/dev/%s", d);
+ asprintf(&to, "%s/dev/%s", dest, d);
+
+ if (!from || !to) {
+ log_error("Failed to allocate devnode path");
+
+ free(from);
+ free(to);
+
+ if (r == 0)
+ r = -ENOMEM;
+
+ break;
+ }
+
+ if (stat(from, &st) < 0) {
+
+ if (errno != ENOENT) {
+ log_error("Failed to stat %s: %m", from);
+
+ if (r == 0)
+ r = -errno;
+ }
+
+ } else {
+ if (mknod(to, st.st_mode, st.st_rdev) < 0) {
+ log_error("mknod(%s) failed: %m", dest);
+
+ if (r == 0)
+ r = -errno;
+ }
+ }
+
+ free(from);
+ free(to);
+ }
+
+ if ((k = get_ctty(&tty, &tty_devnum)) < 0) {
+ log_error("Failed to determine controlling tty: %s", strerror(-k));
+
+ if (r == 0)
+ r = k;
+ } else {
+ char *from = NULL, *to = NULL;
+
+ asprintf(&from, "/dev/%s", tty);
+ asprintf(&to, "%s/dev/console", dest);
+
+ if (!from || !to) {
+ log_error("Out of memory");
+
+ if (r == 0)
+ r = k;
+ } else {
+ /* We need to bind mount our own tty on
+ * /dev/console, since ptys cannot be used
+ * unless on a devpts file system. But to bind
+ * mount it we first have to create a device
+ * node where we can bind mount it on. This is
+ * kinda ugly since the TTY will very likely
+ * be owned by a user/group that does not
+ * exist in the container. */
+
+ if (mknod(to, S_IFCHR|0600, tty_devnum) < 0) {
+ log_error("mknod for /dev/console failed: %m");
+
+ if (r == 0)
+ r = -errno;
+ }
+
+ if (mount(from, to, "bind", MS_BIND, NULL) < 0) {
+ log_error("bind mount for /dev/console failed: %m");
+
+ if (r == 0)
+ r = -errno;
+ }
+ }
+
+ free(from);
+ free(to);
+ }
+
+ free(tty);
+
+ return r;
+}
+
+static int drop_capabilities(void) {
+ static const unsigned long retain[] = {
+ CAP_CHOWN,
+ CAP_DAC_OVERRIDE,
+ CAP_DAC_READ_SEARCH,
+ CAP_FOWNER,
+ CAP_FSETID,
+ CAP_IPC_OWNER,
+ CAP_KILL,
+ CAP_LEASE,
+ CAP_LINUX_IMMUTABLE,
+ CAP_NET_BIND_SERVICE,
+ CAP_NET_BROADCAST,
+ CAP_NET_RAW,
+ CAP_SETGID,
+ CAP_SETFCAP,
+ CAP_SETPCAP,
+ CAP_SETUID,
+ CAP_SYS_ADMIN,
+ CAP_SYS_CHROOT,
+ CAP_SYS_NICE,
+ CAP_SYS_PTRACE,
+ CAP_SYS_TTY_CONFIG
+ };
+
+ unsigned long l;
+
+ for (l = 0; l <= MAX(63LU, (unsigned long) CAP_LAST_CAP); l ++) {
+ unsigned i;
+
+ for (i = 0; i < ELEMENTSOF(retain); i++)
+ if (retain[i] == l)
+ break;
+
+ if (i < ELEMENTSOF(retain))
+ continue;
+
+ if (prctl(PR_CAPBSET_DROP, l) < 0) {
+
+ /* If this capability is not known, EINVAL
+ * will be returned, let's ignore this. */
+ if (errno == EINVAL)
+ continue;
+
+ log_error("PR_CAPBSET_DROP failed: %m");
+ return -errno;
+ }
+ }
+
+ return 0;
+}
+
+static int is_os_tree(const char *path) {
+ int r;
+ char *p;
+ /* We use /bin/sh as flag file if something is an OS */
+
+ if (asprintf(&p, "%s/bin/sh", path) < 0)
+ return -ENOMEM;
+
+ r = access(p, F_OK);
+ free(p);
+
+ return r < 0 ? 0 : 1;
+}
+
+
+int main(int argc, char *argv[]) {
+ pid_t pid = 0;
+ int r = EXIT_FAILURE;
+
+ log_parse_environment();
+ log_open();
+
+ if ((r = parse_argv(argc, argv)) <= 0)
+ goto finish;
+
+ if (arg_directory) {
+ char *p;
+
+ p = path_make_absolute_cwd(arg_directory);
+ free(arg_directory);
+ arg_directory = p;
+ } else
+ arg_directory = get_current_dir_name();
+
+ if (!arg_directory) {
+ log_error("Failed to determine path");
+ goto finish;
+ }
+
+ path_kill_slashes(arg_directory);
+
+ if (geteuid() != 0) {
+ log_error("Need to be root.");
+ goto finish;
+ }
+
+ if (path_equal(arg_directory, "/")) {
+ log_error("Spawning constainer on root directory not supported.");
+ goto finish;
+ }
+
+ if (is_os_tree(arg_directory) <= 0) {
+ log_error("Directory %s doesn't look like an OS root directory. Refusing.", arg_directory);
+ goto finish;
+ }
+
+ log_info("Spawning namespace container on %s.", arg_directory);
+
+ if ((pid = syscall(__NR_clone, SIGCHLD|CLONE_NEWIPC|CLONE_NEWNS|CLONE_NEWPID|CLONE_NEWUTS|CLONE_NEWNET, NULL)) < 0) {
+ log_error("clone() failed: %m");
+ goto finish;
+ }
+
+ if (pid == 0) {
+ const char *hn;
+
+ /* child */
+
+ if (mount_all(arg_directory) < 0)
+ goto child_fail;
+
+ if (copy_devnodes(arg_directory) < 0)
+ goto child_fail;
+
+ if (chdir(arg_directory) < 0) {
+ log_error("chdir(%s) failed: %m", arg_directory);
+ goto child_fail;
+ }
+ if (mount(arg_directory, "/", "bind", MS_BIND|MS_MOVE, NULL) < 0) {
+ log_error("mount(MS_MOVE) failed: %m");
+ goto child_fail;
+ }
+
+ if (chroot(".") < 0) {
+ log_error("chroot() failed: %m");
+ goto child_fail;
+ }
+
+ if (chdir("/") < 0) {
+ log_error("chdir() failed: %m");
+ goto child_fail;
+ }
+
+ if (drop_capabilities() < 0)
+ goto child_fail;
+
+ if ((hn = file_name_from_path(arg_directory)))
+ sethostname(hn, strlen(hn));
+
+ if (argc > optind)
+ execvp(argv[optind], argv + optind);
+ else
+ execl("/bin/bash", "/bin/bash", NULL);
+
+ log_error("execv() failed: %m");
+
+ child_fail:
+ _exit(EXIT_FAILURE);
+ }
+
+ r = wait_for_terminate_and_warn("container", pid);
+
+ if (r < 0)
+ r = EXIT_FAILURE;
+
+finish:
+ free(arg_directory);
+
+ if (pid > 0)
+ kill(pid, SIGTERM);
+
+ return r;
+}
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