From 88213476187cafc86bea2276199891873000588d Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Mon, 14 Mar 2011 02:40:36 +0100 Subject: [PATCH] nspawn: add simple chroot(1) like tool to execute commands in a namespace container --- .gitignore | 1 + Makefile.am | 12 ++ src/nspawn.c | 444 +++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 457 insertions(+) create mode 100644 src/nspawn.c diff --git a/.gitignore b/.gitignore index ffc602a95..d679f791e 100644 --- a/.gitignore +++ b/.gitignore @@ -1,3 +1,4 @@ +systemd-nspawn systemd-stdio-bridge systemd-machine-id-setup systemd-detect-virt diff --git a/Makefile.am b/Makefile.am index 872bcc255..7d6cfd12d 100644 --- a/Makefile.am +++ b/Makefile.am @@ -115,6 +115,9 @@ bin_PROGRAMS = \ systemd-cgls \ systemd-stdio-bridge +sbin_PROGRAMS = \ + systemd-nspawn + if HAVE_GTK bin_PROGRAMS += \ systemadm \ @@ -983,6 +986,15 @@ systemd_cgls_CFLAGS = \ systemd_cgls_LDADD = \ libsystemd-basic.la +systemd_nspawn_SOURCES = \ + src/nspawn.c + +systemd_nspawn_CFLAGS = \ + $(AM_CFLAGS) + +systemd_nspawn_LDADD = \ + libsystemd-basic.la + systemd_stdio_bridge_SOURCES = \ src/bridge.c diff --git a/src/nspawn.c b/src/nspawn.c new file mode 100644 index 000000000..4e4d40ea6 --- /dev/null +++ b/src/nspawn.c @@ -0,0 +1,444 @@ +/*-*- 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 . +***/ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#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; +} -- 2.30.2