#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 <sys/epoll.h>

#include <termios.h>

#include <sys/signalfd.h>

#include <grp.h>

#include <linux/fs.h>

#include <systemd/sd-daemon.h>

#include "log.h"

#include "util.h"

#include "mkdir.h"

#include "audit.h"

#include "missing.h"

#include "cgroup-util.h"

#include "strv.h"

#include "loopback-setup.h"

static char *arg_directory = NULL;

static char *arg_user = NULL;

static bool arg_private_network = false;

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"

" -u --user=USER Run the command under specified user or uid\n"

" --private-network Disable network in container\n",

program_invocation_short_name);

return 0;

}

static int parse_argv(int argc, char *argv[]) {

enum {

ARG_PRIVATE_NETWORK = 0x100

};

static const struct option options[] = {

{ "help", no_argument, NULL, 'h' },

{ "directory", required_argument, NULL, 'D' },

{ "user", required_argument, NULL, 'u' },

{ "private-network", no_argument, NULL, ARG_PRIVATE_NETWORK },

{ NULL, 0, NULL, 0 }

};

int c;

assert(argc >= 0);

assert(argv);

while ((c = getopt_long(argc, argv, "+hD:u:", 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 'u':

free(arg_user);

if (!(arg_user = strdup(optarg))) {

log_error("Failed to duplicate user name.");

return -ENOMEM;

}

break;

case ARG_PRIVATE_NETWORK:

arg_private_network = true;

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;

bool fatal;

} MountPoint;

static const MountPoint mount_table[] = {

{ "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV, true },

{ "/proc/sys", "/proc/sys", "bind", NULL, MS_BIND, true }, /* Bind mount first */

{ "/proc/sys", "/proc/sys", "bind", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, true }, /* Then, make it r/o */

{ "/sys", "/sys", "bind", NULL, MS_BIND, true }, /* Bind mount first */

{ "/sys", "/sys", "bind", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, true }, /* Then, make it r/o */

{ "tmpfs", "/dev", "tmpfs", "mode=755", MS_NOSUID, true },

{ "/dev/pts", "/dev/pts", "bind", NULL, MS_BIND, true },

{ "tmpfs", "/run", "tmpfs", "mode=755", MS_NOSUID|MS_NODEV, true },

#ifdef HAVE_SELINUX

{ "/sys/fs/selinux", "/sys/fs/selinux", "bind", NULL, MS_BIND, false }, /* Bind mount first */

{ "/sys/fs/selinux", "/sys/fs/selinux", "bind", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, false }, /* Then, make it r/o */

#endif

};

unsigned k;

int r = 0;

char *where;

for (k = 0; k < ELEMENTSOF(mount_table); k++) {

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, false)) < 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 &&

mount_table[k].fatal) {

log_error("mount(%s) failed: %m", where);

if (r == 0)

r = -errno;

}

free(where);

}

/* Fix the timezone, if possible */

if (asprintf(&where, "%s/etc/localtime", dest) >= 0) {

if (mount("/etc/localtime", where, "bind", MS_BIND, NULL) >= 0)

mount("/etc/localtime", where, "bind", MS_BIND|MS_REMOUNT|MS_RDONLY, NULL);

free(where);

}

if (asprintf(&where, "%s/etc/timezone", dest) >= 0) {

if (mount("/etc/timezone", where, "bind", MS_BIND, NULL) >= 0)

mount("/etc/timezone", where, "bind", MS_BIND|MS_REMOUNT|MS_RDONLY, NULL);

free(where);

}

return r;

}

static int copy_devnodes(const char *dest, const char *console) {

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;

mode_t u;

struct stat st;

char *from = NULL, *to = NULL;

assert(dest);

assert(console);

u = umask(0000);

NULSTR_FOREACH(d, devnodes) {

from = to = NULL;

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);

from = to = NULL;

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 (!S_ISCHR(st.st_mode) && !S_ISBLK(st.st_mode)) {

log_error("%s is not a char or block device, cannot copy.", from);

if (r == 0)

r = -EIO;

} 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 (stat(console, &st) < 0) {

log_error("Failed to stat %s: %m", console);

if (r == 0)

r = -errno;

goto finish;

} else if (!S_ISCHR(st.st_mode)) {

log_error("/dev/console is not a char device.");

if (r == 0)

r = -EIO;

goto finish;

}

if (asprintf(&to, "%s/dev/console", dest) < 0) {

log_error("Out of memory");

if (r == 0)

r = -ENOMEM;

goto finish;

}

/* We need to bind mount the right tty to /dev/console since

if (mknod(to, (st.st_mode & ~07777) | 0600, st.st_rdev) < 0)

log_error("mknod for /dev/console failed: %m");

if (mount(console, to, "bind", MS_BIND, NULL) < 0) {

log_error("bind mount for /dev/console failed: %m");

if (r == 0)

r = -errno;

}

free(to);

if ((k = chmod_and_chown(console, 0600, 0, 0)) < 0) {

log_error("Failed to correct access mode for TTY: %s", strerror(-k));

if (r == 0)

r = k;

}

finish:

umask(u);

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 <= 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) {

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;

}

static int process_pty(int master, sigset_t *mask) {

char in_buffer[LINE_MAX], out_buffer[LINE_MAX];

size_t in_buffer_full = 0, out_buffer_full = 0;

struct epoll_event stdin_ev, stdout_ev, master_ev, signal_ev;

bool stdin_readable = false, stdout_writable = false, master_readable = false, master_writable = false;

int ep = -1, signal_fd = -1, r;

fd_nonblock(STDIN_FILENO, 1);

fd_nonblock(STDOUT_FILENO, 1);

fd_nonblock(master, 1);

if ((signal_fd = signalfd(-1, mask, SFD_NONBLOCK|SFD_CLOEXEC)) < 0) {

log_error("signalfd(): %m");

r = -errno;

goto finish;

}

if ((ep = epoll_create1(EPOLL_CLOEXEC)) < 0) {

log_error("Failed to create epoll: %m");

r = -errno;

goto finish;

}

zero(stdin_ev);

stdin_ev.events = EPOLLIN|EPOLLET;

stdin_ev.data.fd = STDIN_FILENO;

zero(stdout_ev);

stdout_ev.events = EPOLLOUT|EPOLLET;

stdout_ev.data.fd = STDOUT_FILENO;

zero(master_ev);

master_ev.events = EPOLLIN|EPOLLOUT|EPOLLET;

master_ev.data.fd = master;

zero(signal_ev);

signal_ev.events = EPOLLIN;

signal_ev.data.fd = signal_fd;

if (epoll_ctl(ep, EPOLL_CTL_ADD, STDIN_FILENO, &stdin_ev) < 0 ||

epoll_ctl(ep, EPOLL_CTL_ADD, STDOUT_FILENO, &stdout_ev) < 0 ||

epoll_ctl(ep, EPOLL_CTL_ADD, master, &master_ev) < 0 ||

epoll_ctl(ep, EPOLL_CTL_ADD, signal_fd, &signal_ev) < 0) {

log_error("Failed to regiser fds in epoll: %m");

r = -errno;

goto finish;

}

for (;;) {

struct epoll_event ev[16];

ssize_t k;

int i, nfds;

if ((nfds = epoll_wait(ep, ev, ELEMENTSOF(ev), -1)) < 0) {

if (errno == EINTR || errno == EAGAIN)

continue;

log_error("epoll_wait(): %m");

r = -errno;

goto finish;

}

assert(nfds >= 1);

for (i = 0; i < nfds; i++) {

if (ev[i].data.fd == STDIN_FILENO) {

if (ev[i].events & (EPOLLIN|EPOLLHUP))

stdin_readable = true;

} else if (ev[i].data.fd == STDOUT_FILENO) {

if (ev[i].events & (EPOLLOUT|EPOLLHUP))

stdout_writable = true;

} else if (ev[i].data.fd == master) {

if (ev[i].events & (EPOLLIN|EPOLLHUP))

master_readable = true;

if (ev[i].events & (EPOLLOUT|EPOLLHUP))

master_writable = true;

} else if (ev[i].data.fd == signal_fd) {

struct signalfd_siginfo sfsi;

ssize_t n;

if ((n = read(signal_fd, &sfsi, sizeof(sfsi))) != sizeof(sfsi)) {

if (n >= 0) {

log_error("Failed to read from signalfd: invalid block size");

r = -EIO;

goto finish;

}

if (errno != EINTR && errno != EAGAIN) {

log_error("Failed to read from signalfd: %m");

r = -errno;

goto finish;

}

} else {

if (sfsi.ssi_signo == SIGWINCH) {

struct winsize ws;

/* The window size changed, let's forward that. */

if (ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) >= 0)

ioctl(master, TIOCSWINSZ, &ws);

} else {

r = 0;

goto finish;

}

}

}

}

while ((stdin_readable && in_buffer_full <= 0) ||

(master_writable && in_buffer_full > 0) ||

(master_readable && out_buffer_full <= 0) ||

(stdout_writable && out_buffer_full > 0)) {

if (stdin_readable && in_buffer_full < LINE_MAX) {

if ((k = read(STDIN_FILENO, in_buffer + in_buffer_full, LINE_MAX - in_buffer_full)) < 0) {

if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)

stdin_readable = false;

else {

log_error("read(): %m");

r = -errno;

goto finish;

}

} else

in_buffer_full += (size_t) k;

}

if (master_writable && in_buffer_full > 0) {

if ((k = write(master, in_buffer, in_buffer_full)) < 0) {

if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)

master_writable = false;

else {

log_error("write(): %m");

r = -errno;

goto finish;

}

} else {

assert(in_buffer_full >= (size_t) k);

memmove(in_buffer, in_buffer + k, in_buffer_full - k);

in_buffer_full -= k;

}

}

if (master_readable && out_buffer_full < LINE_MAX) {

if ((k = read(master, out_buffer + out_buffer_full, LINE_MAX - out_buffer_full)) < 0) {

if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)

master_readable = false;

else {

log_error("read(): %m");

r = -errno;

goto finish;

}

} else

out_buffer_full += (size_t) k;

}

if (stdout_writable && out_buffer_full > 0) {

if ((k = write(STDOUT_FILENO, out_buffer, out_buffer_full)) < 0) {

if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)

stdout_writable = false;

else {

log_error("write(): %m");

r = -errno;

goto finish;

}

} else {

assert(out_buffer_full >= (size_t) k);

memmove(out_buffer, out_buffer + k, out_buffer_full - k);

out_buffer_full -= k;

}

}

}

}

finish:

if (ep >= 0)

close_nointr_nofail(ep);

if (signal_fd >= 0)

close_nointr_nofail(signal_fd);

return r;

}

int main(int argc, char *argv[]) {

pid_t pid = 0;

int r = EXIT_FAILURE, k;

char *oldcg = NULL, *newcg = NULL;

int master = -1;

const char *console = NULL;

struct termios saved_attr, raw_attr;

sigset_t mask;

bool saved_attr_valid = false;

struct winsize ws;

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 (sd_booted() <= 0) {

log_error("Not running on a systemd system.");

goto finish;

}

if (path_equal(arg_directory, "/")) {

log_error("Spawning container 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;

}

if ((k = cg_get_by_pid(SYSTEMD_CGROUP_CONTROLLER, 0, &oldcg)) < 0) {

log_error("Failed to determine current cgroup: %s", strerror(-k));

goto finish;

}

if (asprintf(&newcg, "%s/nspawn-%lu", oldcg, (unsigned long) getpid()) < 0) {

log_error("Failed to allocate cgroup path.");

goto finish;

}

if ((k = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, newcg, 0)) < 0) {

log_error("Failed to create cgroup: %s", strerror(-k));

goto finish;

}

if ((master = posix_openpt(O_RDWR|O_NOCTTY|O_CLOEXEC|O_NDELAY)) < 0) {

log_error("Failed to acquire pseudo tty: %m");

goto finish;

}

if (!(console = ptsname(master))) {

log_error("Failed to determine tty name: %m");

goto finish;

}

log_info("Spawning namespace container on %s (console is %s).", arg_directory, console);

if (ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) >= 0)

ioctl(master, TIOCSWINSZ, &ws);

if (unlockpt(master) < 0) {

log_error("Failed to unlock tty: %m");

goto finish;

}

if (tcgetattr(STDIN_FILENO, &saved_attr) < 0) {

log_error("Failed to get terminal attributes: %m");

goto finish;

}

saved_attr_valid = true;

raw_attr = saved_attr;

cfmakeraw(&raw_attr);

raw_attr.c_lflag &= ~ECHO;

if (tcsetattr(STDIN_FILENO, TCSANOW, &raw_attr) < 0) {

log_error("Failed to set terminal attributes: %m");

goto finish;

}

assert_se(sigemptyset(&mask) == 0);

sigset_add_many(&mask, SIGCHLD, SIGWINCH, SIGTERM, SIGINT, -1);

assert_se(sigprocmask(SIG_BLOCK, &mask, NULL) == 0);

pid = syscall(__NR_clone, SIGCHLD|CLONE_NEWIPC|CLONE_NEWNS|CLONE_NEWPID|CLONE_NEWUTS|(arg_private_network ? CLONE_NEWNET : 0), NULL);

if (pid < 0) {

if (errno == EINVAL)

log_error("clone() failed, do you have namespace support enabled in your kernel? (You need UTS, IPC, PID and NET namespacing built in): %m");

else

log_error("clone() failed: %m");

goto finish;

}

if (pid == 0) {

/* child */

const char *hn;

const char *home = NULL;

uid_t uid = (uid_t) -1;

gid_t gid = (gid_t) -1;

const char *envp[] = {

"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",

"container=systemd-nspawn", /* LXC sets container=lxc, so follow the scheme here */

NULL, /* TERM */

NULL, /* HOME */

NULL, /* USER */

NULL, /* LOGNAME */

NULL

};

envp[2] = strv_find_prefix(environ, "TERM=");

close_nointr_nofail(master);

close_nointr(STDIN_FILENO);

close_nointr(STDOUT_FILENO);

close_nointr(STDERR_FILENO);

close_all_fds(NULL, 0);

reset_all_signal_handlers();

assert_se(sigemptyset(&mask) == 0);

assert_se(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);

if (setsid() < 0)

goto child_fail;

if (prctl(PR_SET_PDEATHSIG, SIGKILL) < 0)

goto child_fail;

/* Mark / as private, in case somebody marked it shared */

if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) < 0)

goto child_fail;

if (mount_all(arg_directory) < 0)

goto child_fail;

if (copy_devnodes(arg_directory, console) < 0)

goto child_fail;

if (chdir(arg_directory) < 0) {

log_error("chdir(%s) failed: %m", arg_directory);

goto child_fail;

}

if (open_terminal("dev/console", O_RDWR) != STDIN_FILENO ||

dup2(STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO ||

dup2(STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO)

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;

}

umask(0022);

loopback_setup();

if (drop_capabilities() < 0)

goto child_fail;

if (arg_user) {

if (get_user_creds((const char**)&arg_user, &uid, &gid, &home) < 0) {

log_error("get_user_creds() failed: %m");

goto child_fail;

}

if (mkdir_parents(home, 0775) < 0) {

log_error("mkdir_parents() failed: %m");

goto child_fail;

}

if (safe_mkdir(home, 0775, uid, gid) < 0) {

log_error("safe_mkdir() failed: %m");

goto child_fail;

}

if (initgroups((const char*)arg_user, gid) < 0) {

log_error("initgroups() failed: %m");

goto child_fail;

}

if (setresgid(gid, gid, gid) < 0) {

log_error("setregid() failed: %m");

goto child_fail;

}

if (setresuid(uid, uid, uid) < 0) {

log_error("setreuid() failed: %m");

goto child_fail;

}

}

if ((asprintf((char**)(envp + 3), "HOME=%s", home? home: "/root") < 0) ||

(asprintf((char**)(envp + 4), "USER=%s", arg_user? arg_user : "root") < 0) ||

(asprintf((char**)(envp + 5), "LOGNAME=%s", arg_user? arg_user : "root") < 0)) {

log_error("Out of memory");

goto child_fail;

}

if ((hn = file_name_from_path(arg_directory)))

sethostname(hn, strlen(hn));

if (argc > optind)

execvpe(argv[optind], argv + optind, (char**) envp);

else {

chdir(home ? home : "/root");

execle("/bin/bash", "-bash", NULL, (char**) envp);

}

log_error("execv() failed: %m");

child_fail:

_exit(EXIT_FAILURE);

}

if (process_pty(master, &mask) < 0)

goto finish;

if (saved_attr_valid) {

tcsetattr(STDIN_FILENO, TCSANOW, &saved_attr);

saved_attr_valid = false;

}

r = wait_for_terminate_and_warn(argc > optind ? argv[optind] : "bash", pid);

if (r < 0)

r = EXIT_FAILURE;

finish:

if (saved_attr_valid)

tcsetattr(STDIN_FILENO, TCSANOW, &saved_attr);

if (master >= 0)

close_nointr_nofail(master);

if (oldcg)

cg_attach(SYSTEMD_CGROUP_CONTROLLER, oldcg, 0);

if (newcg)

cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, newcg, true);

free(arg_directory);

free(oldcg);

free(newcg);

return r;

}