/*** 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 Lesser General Public License as published by the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see . ***/ #include #include #include #include #include #include #include #include #include "alloc-util.h" #include "dev-setup.h" #include "fd-util.h" #include "fs-util.h" #include "loopback-setup.h" #include "missing.h" #include "mkdir.h" #include "mount-util.h" #include "namespace.h" #include "path-util.h" #include "selinux-util.h" #include "socket-util.h" #include "string-table.h" #include "string-util.h" #include "strv.h" #include "umask-util.h" #include "user-util.h" #include "util.h" #define DEV_MOUNT_OPTIONS (MS_NOSUID|MS_STRICTATIME|MS_NOEXEC) typedef enum MountMode { /* This is ordered by priority! */ INACCESSIBLE, READONLY, PRIVATE_TMP, PRIVATE_VAR_TMP, PRIVATE_DEV, READWRITE, } MountMode; typedef struct BindMount { const char *path; /* stack memory, doesn't need to be freed explicitly */ char *chased; /* malloc()ed memory, needs to be freed */ MountMode mode; bool ignore; } BindMount; static int append_mounts(BindMount **p, char **strv, MountMode mode) { char **i; assert(p); STRV_FOREACH(i, strv) { (*p)->ignore = false; if ((mode == INACCESSIBLE || mode == READONLY || mode == READWRITE) && (*i)[0] == '-') { (*p)->ignore = true; (*i)++; } if (!path_is_absolute(*i)) return -EINVAL; (*p)->path = *i; (*p)->mode = mode; (*p)++; } return 0; } static int mount_path_compare(const void *a, const void *b) { const BindMount *p = a, *q = b; int d; /* If the paths are not equal, then order prefixes first */ d = path_compare(p->path, q->path); if (d != 0) return d; /* If the paths are equal, check the mode */ if (p->mode < q->mode) return -1; if (p->mode > q->mode) return 1; return 0; } static void drop_duplicates(BindMount *m, unsigned *n) { BindMount *f, *t, *previous; assert(m); assert(n); /* Drops duplicate entries. Expects that the array is properly ordered already. */ for (f = m, t = m, previous = NULL; f < m+*n; f++) { /* The first one wins (which is the one with the more restrictive mode), see mount_path_compare() * above. */ if (previous && path_equal(f->path, previous->path)) { log_debug("%s is duplicate.", f->path); continue; } *t = *f; previous = t; t++; } *n = t - m; } static void drop_inaccessible(BindMount *m, unsigned *n) { BindMount *f, *t; const char *clear = NULL; assert(m); assert(n); /* Drops all entries obstructed by another entry further up the tree. Expects that the array is properly * ordered already. */ for (f = m, t = m; f < m+*n; f++) { /* If we found a path set for INACCESSIBLE earlier, and this entry has it as prefix we should drop * it, as inaccessible paths really should drop the entire subtree. */ if (clear && path_startswith(f->path, clear)) { log_debug("%s is masked by %s.", f->path, clear); continue; } clear = f->mode == INACCESSIBLE ? f->path : NULL; *t = *f; t++; } *n = t - m; } static void drop_nop(BindMount *m, unsigned *n) { BindMount *f, *t; assert(m); assert(n); /* Drops all entries which have an immediate parent that has the same type, as they are redundant. Assumes the * list is ordered by prefixes. */ for (f = m, t = m; f < m+*n; f++) { /* Only suppress such subtrees for READONLY and READWRITE entries */ if (IN_SET(f->mode, READONLY, READWRITE)) { BindMount *p; bool found = false; /* Now let's find the first parent of the entry we are looking at. */ for (p = t-1; p >= m; p--) { if (path_startswith(f->path, p->path)) { found = true; break; } } /* We found it, let's see if it's the same mode, if so, we can drop this entry */ if (found && p->mode == f->mode) { log_debug("%s is redundant by %s", f->path, p->path); continue; } } *t = *f; t++; } *n = t - m; } static void drop_outside_root(const char *root_directory, BindMount *m, unsigned *n) { BindMount *f, *t; assert(m); assert(n); if (!root_directory) return; /* Drops all mounts that are outside of the root directory. */ for (f = m, t = m; f < m+*n; f++) { if (!path_startswith(f->path, root_directory)) { log_debug("%s is outside of root directory.", f->path); continue; } *t = *f; t++; } *n = t - m; } static int mount_dev(BindMount *m) { static const char devnodes[] = "/dev/null\0" "/dev/zero\0" "/dev/full\0" "/dev/random\0" "/dev/urandom\0" "/dev/tty\0"; char temporary_mount[] = "/tmp/namespace-dev-XXXXXX"; const char *d, *dev = NULL, *devpts = NULL, *devshm = NULL, *devhugepages = NULL, *devmqueue = NULL, *devlog = NULL, *devptmx = NULL; _cleanup_umask_ mode_t u; int r; assert(m); u = umask(0000); if (!mkdtemp(temporary_mount)) return -errno; dev = strjoina(temporary_mount, "/dev"); (void) mkdir(dev, 0755); if (mount("tmpfs", dev, "tmpfs", DEV_MOUNT_OPTIONS, "mode=755") < 0) { r = -errno; goto fail; } devpts = strjoina(temporary_mount, "/dev/pts"); (void) mkdir(devpts, 0755); if (mount("/dev/pts", devpts, NULL, MS_BIND, NULL) < 0) { r = -errno; goto fail; } devptmx = strjoina(temporary_mount, "/dev/ptmx"); if (symlink("pts/ptmx", devptmx) < 0) { r = -errno; goto fail; } devshm = strjoina(temporary_mount, "/dev/shm"); (void) mkdir(devshm, 01777); r = mount("/dev/shm", devshm, NULL, MS_BIND, NULL); if (r < 0) { r = -errno; goto fail; } devmqueue = strjoina(temporary_mount, "/dev/mqueue"); (void) mkdir(devmqueue, 0755); (void) mount("/dev/mqueue", devmqueue, NULL, MS_BIND, NULL); devhugepages = strjoina(temporary_mount, "/dev/hugepages"); (void) mkdir(devhugepages, 0755); (void) mount("/dev/hugepages", devhugepages, NULL, MS_BIND, NULL); devlog = strjoina(temporary_mount, "/dev/log"); (void) symlink("/run/systemd/journal/dev-log", devlog); NULSTR_FOREACH(d, devnodes) { _cleanup_free_ char *dn = NULL; struct stat st; r = stat(d, &st); if (r < 0) { if (errno == ENOENT) continue; r = -errno; goto fail; } if (!S_ISBLK(st.st_mode) && !S_ISCHR(st.st_mode)) { r = -EINVAL; goto fail; } if (st.st_rdev == 0) continue; dn = strappend(temporary_mount, d); if (!dn) { r = -ENOMEM; goto fail; } mac_selinux_create_file_prepare(d, st.st_mode); r = mknod(dn, st.st_mode, st.st_rdev); mac_selinux_create_file_clear(); if (r < 0) { r = -errno; goto fail; } } dev_setup(temporary_mount, UID_INVALID, GID_INVALID); /* Create the /dev directory if missing. It is more likely to be * missing when the service is started with RootDirectory. This is * consistent with mount units creating the mount points when missing. */ (void) mkdir_p_label(m->path, 0755); /* Unmount everything in old /dev */ umount_recursive(m->path, 0); if (mount(dev, m->path, NULL, MS_MOVE, NULL) < 0) { r = -errno; goto fail; } rmdir(dev); rmdir(temporary_mount); return 0; fail: if (devpts) umount(devpts); if (devshm) umount(devshm); if (devhugepages) umount(devhugepages); if (devmqueue) umount(devmqueue); umount(dev); rmdir(dev); rmdir(temporary_mount); return r; } static int apply_mount( BindMount *m, const char *tmp_dir, const char *var_tmp_dir) { const char *what; int r; assert(m); log_debug("Applying namespace mount on %s", m->path); switch (m->mode) { case INACCESSIBLE: { struct stat target; /* First, get rid of everything that is below if there * is anything... Then, overmount it with an * inaccessible path. */ (void) umount_recursive(m->path, 0); if (lstat(m->path, &target) < 0) return log_debug_errno(errno, "Failed to lstat() %s to determine what to mount over it: %m", m->path); what = mode_to_inaccessible_node(target.st_mode); if (!what) { log_debug("File type not supported for inaccessible mounts. Note that symlinks are not allowed"); return -ELOOP; } break; } case READONLY: case READWRITE: r = path_is_mount_point(m->path, 0); if (r < 0) return log_debug_errno(r, "Failed to determine whether %s is already a mount point: %m", m->path); if (r > 0) /* Nothing to do here, it is already a mount. We just later toggle the MS_RDONLY bit for the mount point if needed. */ return 0; /* This isn't a mount point yet, let's make it one. */ what = m->path; break; case PRIVATE_TMP: what = tmp_dir; break; case PRIVATE_VAR_TMP: what = var_tmp_dir; break; case PRIVATE_DEV: return mount_dev(m); default: assert_not_reached("Unknown mode"); } assert(what); if (mount(what, m->path, NULL, MS_BIND|MS_REC, NULL) < 0) return log_debug_errno(errno, "Failed to mount %s to %s: %m", what, m->path); log_debug("Successfully mounted %s to %s", what, m->path); return 0; } static int make_read_only(BindMount *m, char **blacklist) { int r = 0; assert(m); if (IN_SET(m->mode, INACCESSIBLE, READONLY)) r = bind_remount_recursive(m->path, true, blacklist); else if (m->mode == PRIVATE_DEV) { /* Can be readonly but the submounts can't*/ if (mount(NULL, m->path, NULL, MS_REMOUNT|DEV_MOUNT_OPTIONS|MS_RDONLY, NULL) < 0) r = -errno; } else return 0; /* Not that we only turn on the MS_RDONLY flag here, we never turn it off. Something that was marked read-only * already stays this way. This improves compatibility with container managers, where we won't attempt to undo * read-only mounts already applied. */ return r; } static int chase_all_symlinks(const char *root_directory, BindMount *m, unsigned *n) { BindMount *f, *t; int r; assert(m); assert(n); /* Since mount() will always follow symlinks and we need to take the different root directory into account we * chase the symlinks on our own first. This call wil do so for all entries and remove all entries where we * can't resolve the path, and which have been marked for such removal. */ for (f = m, t = m; f < m+*n; f++) { r = chase_symlinks(f->path, root_directory, &f->chased); if (r == -ENOENT && f->ignore) /* Doesn't exist? Then remove it! */ continue; if (r < 0) return log_debug_errno(r, "Failed to chase symlinks for %s: %m", f->path); if (path_equal(f->path, f->chased)) f->chased = mfree(f->chased); else { log_debug("Chased %s → %s", f->path, f->chased); f->path = f->chased; } *t = *f; t++; } *n = t - m; return 0; } int setup_namespace( const char* root_directory, char** read_write_paths, char** read_only_paths, char** inaccessible_paths, const char* tmp_dir, const char* var_tmp_dir, bool private_dev, bool protect_sysctl, bool protect_cgroups, ProtectHome protect_home, ProtectSystem protect_system, unsigned long mount_flags) { BindMount *m, *mounts = NULL; bool make_slave = false; unsigned n; int r = 0; if (mount_flags == 0) mount_flags = MS_SHARED; n = !!tmp_dir + !!var_tmp_dir + strv_length(read_write_paths) + strv_length(read_only_paths) + strv_length(inaccessible_paths) + private_dev + (protect_sysctl ? 3 : 0) + (protect_cgroups != protect_sysctl) + (protect_home != PROTECT_HOME_NO || protect_system == PROTECT_SYSTEM_STRICT ? 3 : 0) + (protect_system == PROTECT_SYSTEM_STRICT ? (2 + !private_dev + !protect_sysctl) : ((protect_system != PROTECT_SYSTEM_NO ? 3 : 0) + (protect_system == PROTECT_SYSTEM_FULL ? 1 : 0))); if (root_directory || n > 0) make_slave = true; if (n > 0) { m = mounts = (BindMount *) alloca0(n * sizeof(BindMount)); r = append_mounts(&m, read_write_paths, READWRITE); if (r < 0) return r; r = append_mounts(&m, read_only_paths, READONLY); if (r < 0) return r; r = append_mounts(&m, inaccessible_paths, INACCESSIBLE); if (r < 0) return r; if (tmp_dir) { m->path = prefix_roota(root_directory, "/tmp"); m->mode = PRIVATE_TMP; m++; } if (var_tmp_dir) { m->path = prefix_roota(root_directory, "/var/tmp"); m->mode = PRIVATE_VAR_TMP; m++; } if (private_dev) { m->path = prefix_roota(root_directory, "/dev"); m->mode = PRIVATE_DEV; m++; } if (protect_sysctl) { m->path = prefix_roota(root_directory, "/proc/sys"); m->mode = READONLY; m++; m->path = prefix_roota(root_directory, "/proc/sysrq-trigger"); m->mode = READONLY; m->ignore = true; /* Not always compiled into the kernel */ m++; m->path = prefix_roota(root_directory, "/sys"); m->mode = READONLY; m++; } if (protect_cgroups != protect_sysctl) { m->path = prefix_roota(root_directory, "/sys/fs/cgroup"); m->mode = protect_cgroups ? READONLY : READWRITE; m++; } if (protect_home != PROTECT_HOME_NO || protect_system == PROTECT_SYSTEM_STRICT) { const char *home_dir, *run_user_dir, *root_dir; /* If protection of $HOME and $XDG_RUNTIME_DIR is requested, then go for it. If we are in * strict system protection mode, then also add entries for these directories, but mark them * writable. This is because we want ProtectHome= and ProtectSystem= to be fully orthogonal. */ home_dir = prefix_roota(root_directory, "/home"); home_dir = strjoina("-", home_dir); run_user_dir = prefix_roota(root_directory, "/run/user"); run_user_dir = strjoina("-", run_user_dir); root_dir = prefix_roota(root_directory, "/root"); root_dir = strjoina("-", root_dir); r = append_mounts(&m, STRV_MAKE(home_dir, run_user_dir, root_dir), protect_home == PROTECT_HOME_READ_ONLY ? READONLY : protect_home == PROTECT_HOME_YES ? INACCESSIBLE : READWRITE); if (r < 0) return r; } if (protect_system == PROTECT_SYSTEM_STRICT) { /* In strict mode, we mount everything read-only, except for /proc, /dev, /sys which are the * kernel API VFS, which are left writable, but PrivateDevices= + ProtectKernelTunables= * protect those, and these options should be fully orthogonal. (And of course /home and * friends are also left writable, as ProtectHome= shall manage those, orthogonally, see * above). */ m->path = prefix_roota(root_directory, "/"); m->mode = READONLY; m++; m->path = prefix_roota(root_directory, "/proc"); m->mode = READWRITE; m++; if (!private_dev) { m->path = prefix_roota(root_directory, "/dev"); m->mode = READWRITE; m++; } if (!protect_sysctl) { m->path = prefix_roota(root_directory, "/sys"); m->mode = READWRITE; m++; } } else if (protect_system != PROTECT_SYSTEM_NO) { const char *usr_dir, *boot_dir, *efi_dir, *etc_dir; /* In any other mode we simply mark the relevant three directories ready-only. */ usr_dir = prefix_roota(root_directory, "/usr"); boot_dir = prefix_roota(root_directory, "/boot"); boot_dir = strjoina("-", boot_dir); efi_dir = prefix_roota(root_directory, "/efi"); efi_dir = strjoina("-", efi_dir); etc_dir = prefix_roota(root_directory, "/etc"); r = append_mounts(&m, protect_system == PROTECT_SYSTEM_FULL ? STRV_MAKE(usr_dir, boot_dir, efi_dir, etc_dir) : STRV_MAKE(usr_dir, boot_dir, efi_dir), READONLY); if (r < 0) return r; } assert(mounts + n == m); /* Resolve symlinks manually first, as mount() will always follow them relative to the host's * root. Moreover we want to suppress duplicates based on the resolved paths. This of course is a bit * racy. */ r = chase_all_symlinks(root_directory, mounts, &n); if (r < 0) goto finish; qsort(mounts, n, sizeof(BindMount), mount_path_compare); drop_duplicates(mounts, &n); drop_outside_root(root_directory, mounts, &n); drop_inaccessible(mounts, &n); drop_nop(mounts, &n); } if (unshare(CLONE_NEWNS) < 0) { r = -errno; goto finish; } if (make_slave) { /* Remount / as SLAVE so that nothing now mounted in the namespace shows up in the parent */ if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0) { r = -errno; goto finish; } } if (root_directory) { /* Turn directory into bind mount, if it isn't one yet */ r = path_is_mount_point(root_directory, AT_SYMLINK_FOLLOW); if (r < 0) goto finish; if (r == 0) { if (mount(root_directory, root_directory, NULL, MS_BIND|MS_REC, NULL) < 0) { r = -errno; goto finish; } } } if (n > 0) { char **blacklist; unsigned j; /* First round, add in all special mounts we need */ for (m = mounts; m < mounts + n; ++m) { r = apply_mount(m, tmp_dir, var_tmp_dir); if (r < 0) goto finish; } /* Create a blacklist we can pass to bind_mount_recursive() */ blacklist = newa(char*, n+1); for (j = 0; j < n; j++) blacklist[j] = (char*) mounts[j].path; blacklist[j] = NULL; /* Second round, flip the ro bits if necessary. */ for (m = mounts; m < mounts + n; ++m) { r = make_read_only(m, blacklist); if (r < 0) goto finish; } } if (root_directory) { /* MS_MOVE does not work on MS_SHARED so the remount MS_SHARED will be done later */ r = mount_move_root(root_directory); if (r < 0) goto finish; } /* Remount / as the desired mode. Not that this will not * reestablish propagation from our side to the host, since * what's disconnected is disconnected. */ if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0) { r = -errno; goto finish; } r = 0; finish: for (m = mounts; m < mounts + n; m++) free(m->chased); return r; } static int setup_one_tmp_dir(const char *id, const char *prefix, char **path) { _cleanup_free_ char *x = NULL; char bid[SD_ID128_STRING_MAX]; sd_id128_t boot_id; int r; assert(id); assert(prefix); assert(path); /* We include the boot id in the directory so that after a * reboot we can easily identify obsolete directories. */ r = sd_id128_get_boot(&boot_id); if (r < 0) return r; x = strjoin(prefix, "/systemd-private-", sd_id128_to_string(boot_id, bid), "-", id, "-XXXXXX", NULL); if (!x) return -ENOMEM; RUN_WITH_UMASK(0077) if (!mkdtemp(x)) return -errno; RUN_WITH_UMASK(0000) { char *y; y = strjoina(x, "/tmp"); if (mkdir(y, 0777 | S_ISVTX) < 0) return -errno; } *path = x; x = NULL; return 0; } int setup_tmp_dirs(const char *id, char **tmp_dir, char **var_tmp_dir) { char *a, *b; int r; assert(id); assert(tmp_dir); assert(var_tmp_dir); r = setup_one_tmp_dir(id, "/tmp", &a); if (r < 0) return r; r = setup_one_tmp_dir(id, "/var/tmp", &b); if (r < 0) { char *t; t = strjoina(a, "/tmp"); rmdir(t); rmdir(a); free(a); return r; } *tmp_dir = a; *var_tmp_dir = b; return 0; } int setup_netns(int netns_storage_socket[2]) { _cleanup_close_ int netns = -1; int r, q; assert(netns_storage_socket); assert(netns_storage_socket[0] >= 0); assert(netns_storage_socket[1] >= 0); /* We use the passed socketpair as a storage buffer for our * namespace reference fd. Whatever process runs this first * shall create a new namespace, all others should just join * it. To serialize that we use a file lock on the socket * pair. * * It's a bit crazy, but hey, works great! */ if (lockf(netns_storage_socket[0], F_LOCK, 0) < 0) return -errno; netns = receive_one_fd(netns_storage_socket[0], MSG_DONTWAIT); if (netns == -EAGAIN) { /* Nothing stored yet, so let's create a new namespace */ if (unshare(CLONE_NEWNET) < 0) { r = -errno; goto fail; } loopback_setup(); netns = open("/proc/self/ns/net", O_RDONLY|O_CLOEXEC|O_NOCTTY); if (netns < 0) { r = -errno; goto fail; } r = 1; } else if (netns < 0) { r = netns; goto fail; } else { /* Yay, found something, so let's join the namespace */ if (setns(netns, CLONE_NEWNET) < 0) { r = -errno; goto fail; } r = 0; } q = send_one_fd(netns_storage_socket[1], netns, MSG_DONTWAIT); if (q < 0) { r = q; goto fail; } fail: (void) lockf(netns_storage_socket[0], F_ULOCK, 0); return r; } static const char *const protect_home_table[_PROTECT_HOME_MAX] = { [PROTECT_HOME_NO] = "no", [PROTECT_HOME_YES] = "yes", [PROTECT_HOME_READ_ONLY] = "read-only", }; DEFINE_STRING_TABLE_LOOKUP(protect_home, ProtectHome); static const char *const protect_system_table[_PROTECT_SYSTEM_MAX] = { [PROTECT_SYSTEM_NO] = "no", [PROTECT_SYSTEM_YES] = "yes", [PROTECT_SYSTEM_FULL] = "full", [PROTECT_SYSTEM_STRICT] = "strict", }; DEFINE_STRING_TABLE_LOOKUP(protect_system, ProtectSystem);