nspawn: add simple chroot(1) like tool to execute commands in a namespace container
This commit is contained in:
Lennart Poettering
parent
f9b9232be9
commit
8821347618
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@ -1,3 +1,4 @@
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systemd-nspawn
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systemd-stdio-bridge
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systemd-machine-id-setup
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systemd-detect-virt
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12
Makefile.am
12
Makefile.am
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@ -115,6 +115,9 @@ bin_PROGRAMS = \
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systemd-cgls \
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systemd-stdio-bridge
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sbin_PROGRAMS = \
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systemd-nspawn
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if HAVE_GTK
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bin_PROGRAMS += \
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systemadm \
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@ -983,6 +986,15 @@ systemd_cgls_CFLAGS = \
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systemd_cgls_LDADD = \
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libsystemd-basic.la
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systemd_nspawn_SOURCES = \
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src/nspawn.c
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systemd_nspawn_CFLAGS = \
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$(AM_CFLAGS)
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systemd_nspawn_LDADD = \
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libsystemd-basic.la
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systemd_stdio_bridge_SOURCES = \
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src/bridge.c
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@ -0,0 +1,444 @@
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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <signal.h>
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#include <sched.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/syscall.h>
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#include <sys/mount.h>
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#include <sys/wait.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <errno.h>
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#include <sys/prctl.h>
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#include <sys/capability.h>
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#include <getopt.h>
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#include "log.h"
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#include "util.h"
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static char *arg_directory = NULL;
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static int help(void) {
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printf("%s [OPTIONS...] [PATH] [ARGUMENTS...]\n\n"
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"Spawn a minimal namespace container for debugging, testing and building.\n\n"
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" -h --help Show this help\n"
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" -D --directory=NAME Root directory for the container\n",
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program_invocation_short_name);
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return 0;
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}
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static int parse_argv(int argc, char *argv[]) {
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static const struct option options[] = {
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{ "help", no_argument, NULL, 'h' },
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{ "directory", required_argument, NULL, 'D' },
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{ NULL, 0, NULL, 0 }
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};
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int c;
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assert(argc >= 0);
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assert(argv);
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while ((c = getopt_long(argc, argv, "+hD:", options, NULL)) >= 0) {
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switch (c) {
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case 'h':
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help();
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return 0;
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case 'D':
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free(arg_directory);
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if (!(arg_directory = strdup(optarg))) {
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log_error("Failed to duplicate root directory.");
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return -ENOMEM;
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}
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break;
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case '?':
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return -EINVAL;
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default:
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log_error("Unknown option code %c", c);
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return -EINVAL;
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}
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}
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return 1;
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}
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static int mount_all(const char *dest) {
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typedef struct MountPoint {
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const char *what;
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const char *where;
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const char *type;
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const char *options;
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unsigned long flags;
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} MountPoint;
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static const MountPoint mount_table[] = {
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{ "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV },
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{ "/proc/sys", "/proc/sys", "bind", NULL, MS_BIND }, /* Bind mount first */
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{ "/proc/sys", "/proc/sys", "bind", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT }, /* Then, make it r/o */
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{ "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY },
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{ "tmpfs", "/dev", "tmpfs", "mode=755", MS_NOSUID },
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{ "/dev/pts", "/dev/pts", "bind", NULL, MS_BIND },
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{ "tmpfs", "/dev/.run", "tmpfs", "mode=755", MS_NOSUID|MS_NOEXEC|MS_NODEV },
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};
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unsigned k;
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int r = 0;
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for (k = 0; k < ELEMENTSOF(mount_table); k++) {
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char *where;
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int t;
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if (asprintf(&where, "%s/%s", dest, mount_table[k].where) < 0) {
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log_error("Out of memory");
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if (r == 0)
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r = -ENOMEM;
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break;
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}
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if ((t = path_is_mount_point(where)) < 0) {
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log_error("Failed to detect whether %s is a mount point: %s", where, strerror(-t));
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free(where);
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if (r == 0)
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r = t;
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continue;
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}
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mkdir_p(where, 0755);
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if (mount(mount_table[k].what,
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where,
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mount_table[k].type,
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mount_table[k].flags,
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mount_table[k].options) < 0) {
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log_error("mount(%s) failed: %m", where);
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if (r == 0)
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r = -errno;
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}
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free(where);
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}
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return r;
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}
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static int copy_devnodes(const char *dest) {
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static const char devnodes[] =
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"null\0"
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"zero\0"
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"full\0"
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"random\0"
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"urandom\0"
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"tty\0"
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"ptmx\0"
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"kmsg\0"
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"rtc0\0";
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const char *d;
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int r = 0, k;
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char *tty = NULL;
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dev_t tty_devnum;
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NULSTR_FOREACH(d, devnodes) {
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char *from = NULL, *to = NULL;
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struct stat st;
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asprintf(&from, "/dev/%s", d);
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asprintf(&to, "%s/dev/%s", dest, d);
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if (!from || !to) {
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log_error("Failed to allocate devnode path");
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free(from);
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free(to);
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if (r == 0)
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r = -ENOMEM;
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break;
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}
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if (stat(from, &st) < 0) {
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if (errno != ENOENT) {
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log_error("Failed to stat %s: %m", from);
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if (r == 0)
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r = -errno;
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}
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} else {
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if (mknod(to, st.st_mode, st.st_rdev) < 0) {
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log_error("mknod(%s) failed: %m", dest);
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if (r == 0)
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r = -errno;
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}
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}
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free(from);
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free(to);
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}
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if ((k = get_ctty(&tty, &tty_devnum)) < 0) {
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log_error("Failed to determine controlling tty: %s", strerror(-k));
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if (r == 0)
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r = k;
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} else {
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char *from = NULL, *to = NULL;
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asprintf(&from, "/dev/%s", tty);
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asprintf(&to, "%s/dev/console", dest);
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if (!from || !to) {
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log_error("Out of memory");
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if (r == 0)
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r = k;
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} else {
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/* We need to bind mount our own tty on
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* /dev/console, since ptys cannot be used
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* unless on a devpts file system. But to bind
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* mount it we first have to create a device
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* node where we can bind mount it on. This is
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* kinda ugly since the TTY will very likely
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* be owned by a user/group that does not
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* exist in the container. */
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if (mknod(to, S_IFCHR|0600, tty_devnum) < 0) {
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log_error("mknod for /dev/console failed: %m");
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if (r == 0)
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r = -errno;
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}
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if (mount(from, to, "bind", MS_BIND, NULL) < 0) {
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log_error("bind mount for /dev/console failed: %m");
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if (r == 0)
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r = -errno;
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}
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}
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free(from);
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free(to);
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}
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free(tty);
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return r;
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}
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static int drop_capabilities(void) {
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static const unsigned long retain[] = {
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CAP_CHOWN,
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CAP_DAC_OVERRIDE,
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CAP_DAC_READ_SEARCH,
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CAP_FOWNER,
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CAP_FSETID,
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CAP_IPC_OWNER,
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CAP_KILL,
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CAP_LEASE,
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CAP_LINUX_IMMUTABLE,
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CAP_NET_BIND_SERVICE,
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CAP_NET_BROADCAST,
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CAP_NET_RAW,
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CAP_SETGID,
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CAP_SETFCAP,
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CAP_SETPCAP,
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CAP_SETUID,
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CAP_SYS_ADMIN,
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CAP_SYS_CHROOT,
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CAP_SYS_NICE,
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CAP_SYS_PTRACE,
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CAP_SYS_TTY_CONFIG
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};
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unsigned long l;
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for (l = 0; l <= MAX(63LU, (unsigned long) CAP_LAST_CAP); l ++) {
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unsigned i;
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for (i = 0; i < ELEMENTSOF(retain); i++)
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if (retain[i] == l)
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break;
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if (i < ELEMENTSOF(retain))
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continue;
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if (prctl(PR_CAPBSET_DROP, l) < 0) {
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/* If this capability is not known, EINVAL
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* will be returned, let's ignore this. */
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if (errno == EINVAL)
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continue;
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log_error("PR_CAPBSET_DROP failed: %m");
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return -errno;
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}
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}
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return 0;
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}
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static int is_os_tree(const char *path) {
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int r;
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char *p;
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/* We use /bin/sh as flag file if something is an OS */
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if (asprintf(&p, "%s/bin/sh", path) < 0)
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return -ENOMEM;
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r = access(p, F_OK);
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free(p);
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return r < 0 ? 0 : 1;
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}
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int main(int argc, char *argv[]) {
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pid_t pid = 0;
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int r = EXIT_FAILURE;
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log_parse_environment();
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log_open();
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if ((r = parse_argv(argc, argv)) <= 0)
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goto finish;
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if (arg_directory) {
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char *p;
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p = path_make_absolute_cwd(arg_directory);
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free(arg_directory);
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arg_directory = p;
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} else
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arg_directory = get_current_dir_name();
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if (!arg_directory) {
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log_error("Failed to determine path");
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goto finish;
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}
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path_kill_slashes(arg_directory);
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if (geteuid() != 0) {
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log_error("Need to be root.");
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goto finish;
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}
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if (path_equal(arg_directory, "/")) {
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log_error("Spawning constainer on root directory not supported.");
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goto finish;
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}
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if (is_os_tree(arg_directory) <= 0) {
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log_error("Directory %s doesn't look like an OS root directory. Refusing.", arg_directory);
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goto finish;
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}
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log_info("Spawning namespace container on %s.", arg_directory);
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if ((pid = syscall(__NR_clone, SIGCHLD|CLONE_NEWIPC|CLONE_NEWNS|CLONE_NEWPID|CLONE_NEWUTS|CLONE_NEWNET, NULL)) < 0) {
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log_error("clone() failed: %m");
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goto finish;
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}
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if (pid == 0) {
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const char *hn;
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/* child */
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if (mount_all(arg_directory) < 0)
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goto child_fail;
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if (copy_devnodes(arg_directory) < 0)
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goto child_fail;
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if (chdir(arg_directory) < 0) {
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log_error("chdir(%s) failed: %m", arg_directory);
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goto child_fail;
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}
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if (mount(arg_directory, "/", "bind", MS_BIND|MS_MOVE, NULL) < 0) {
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log_error("mount(MS_MOVE) failed: %m");
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goto child_fail;
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}
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if (chroot(".") < 0) {
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log_error("chroot() failed: %m");
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goto child_fail;
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}
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if (chdir("/") < 0) {
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log_error("chdir() failed: %m");
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goto child_fail;
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}
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if (drop_capabilities() < 0)
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goto child_fail;
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if ((hn = file_name_from_path(arg_directory)))
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sethostname(hn, strlen(hn));
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if (argc > optind)
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execvp(argv[optind], argv + optind);
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else
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execl("/bin/bash", "/bin/bash", NULL);
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log_error("execv() failed: %m");
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child_fail:
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_exit(EXIT_FAILURE);
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}
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r = wait_for_terminate_and_warn("container", pid);
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if (r < 0)
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r = EXIT_FAILURE;
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finish:
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free(arg_directory);
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if (pid > 0)
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kill(pid, SIGTERM);
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return r;
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}
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