/* SPDX-License-Identifier: LGPL-2.1+ */ #include #include #include #include #include #include #include #include #include "alloc-util.h" #include "base-filesystem.h" #include "dev-setup.h" #include "fd-util.h" #include "fs-util.h" #include "label.h" #include "loop-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 "stat-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, BIND_MOUNT, BIND_MOUNT_RECURSIVE, PRIVATE_TMP, PRIVATE_DEV, BIND_DEV, EMPTY_DIR, SYSFS, PROCFS, READONLY, READWRITE, TMPFS, } MountMode; typedef struct MountEntry { const char *path_const; /* Memory allocated on stack or static */ MountMode mode:5; bool ignore:1; /* Ignore if path does not exist? */ bool has_prefix:1; /* Already is prefixed by the root dir? */ bool read_only:1; /* Shall this mount point be read-only? */ bool applied:1; /* Already applied */ char *path_malloc; /* Use this instead of 'path_const' if we had to allocate memory */ const char *source_const; /* The source path, for bind mounts */ char *source_malloc; const char *options_const;/* Mount options for tmpfs */ char *options_malloc; unsigned long flags; /* Mount flags used by EMPTY_DIR and TMPFS. Do not include MS_RDONLY here, but please use read_only. */ unsigned n_followed; } MountEntry; /* If MountAPIVFS= is used, let's mount /sys and /proc into the it, but only as a fallback if the user hasn't mounted * something there already. These mounts are hence overridden by any other explicitly configured mounts. */ static const MountEntry apivfs_table[] = { { "/proc", PROCFS, false }, { "/dev", BIND_DEV, false }, { "/sys", SYSFS, false }, }; /* ProtectKernelTunables= option and the related filesystem APIs */ static const MountEntry protect_kernel_tunables_table[] = { { "/proc/acpi", READONLY, true }, { "/proc/apm", READONLY, true }, /* Obsolete API, there's no point in permitting access to this, ever */ { "/proc/asound", READONLY, true }, { "/proc/bus", READONLY, true }, { "/proc/fs", READONLY, true }, { "/proc/irq", READONLY, true }, { "/proc/kallsyms", INACCESSIBLE, true }, { "/proc/kcore", INACCESSIBLE, true }, { "/proc/latency_stats", READONLY, true }, { "/proc/mtrr", READONLY, true }, { "/proc/scsi", READONLY, true }, { "/proc/sys", READONLY, false }, { "/proc/sysrq-trigger", READONLY, true }, { "/proc/timer_stats", READONLY, true }, { "/sys", READONLY, false }, { "/sys/fs/bpf", READONLY, true }, { "/sys/fs/cgroup", READWRITE, false }, /* READONLY is set by ProtectControlGroups= option */ { "/sys/fs/selinux", READWRITE, true }, { "/sys/kernel/debug", READONLY, true }, { "/sys/kernel/tracing", READONLY, true }, }; /* ProtectKernelModules= option */ static const MountEntry protect_kernel_modules_table[] = { #if HAVE_SPLIT_USR { "/lib/modules", INACCESSIBLE, true }, #endif { "/usr/lib/modules", INACCESSIBLE, true }, }; /* * ProtectHome=read-only table, protect $HOME and $XDG_RUNTIME_DIR and rest of * system should be protected by ProtectSystem= */ static const MountEntry protect_home_read_only_table[] = { { "/home", READONLY, true }, { "/run/user", READONLY, true }, { "/root", READONLY, true }, }; /* ProtectHome=tmpfs table */ static const MountEntry protect_home_tmpfs_table[] = { { "/home", TMPFS, true, .read_only = true, .options_const = "mode=0755", .flags = MS_NODEV|MS_STRICTATIME }, { "/run/user", TMPFS, true, .read_only = true, .options_const = "mode=0755", .flags = MS_NODEV|MS_STRICTATIME }, { "/root", TMPFS, true, .read_only = true, .options_const = "mode=0700", .flags = MS_NODEV|MS_STRICTATIME }, }; /* ProtectHome=yes table */ static const MountEntry protect_home_yes_table[] = { { "/home", INACCESSIBLE, true }, { "/run/user", INACCESSIBLE, true }, { "/root", INACCESSIBLE, true }, }; /* ProtectSystem=yes table */ static const MountEntry protect_system_yes_table[] = { { "/usr", READONLY, false }, { "/boot", READONLY, true }, { "/efi", READONLY, true }, #if HAVE_SPLIT_USR { "/lib", READONLY, true }, { "/lib64", READONLY, true }, { "/bin", READONLY, true }, # if HAVE_SPLIT_BIN { "/sbin", READONLY, true }, # endif #endif }; /* ProtectSystem=full includes ProtectSystem=yes */ static const MountEntry protect_system_full_table[] = { { "/usr", READONLY, false }, { "/boot", READONLY, true }, { "/efi", READONLY, true }, { "/etc", READONLY, false }, #if HAVE_SPLIT_USR { "/lib", READONLY, true }, { "/lib64", READONLY, true }, { "/bin", READONLY, true }, # if HAVE_SPLIT_BIN { "/sbin", READONLY, true }, # endif #endif }; /* * ProtectSystem=strict table. In this 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). */ static const MountEntry protect_system_strict_table[] = { { "/", READONLY, false }, { "/proc", READWRITE, false }, /* ProtectKernelTunables= */ { "/sys", READWRITE, false }, /* ProtectKernelTunables= */ { "/dev", READWRITE, false }, /* PrivateDevices= */ { "/home", READWRITE, true }, /* ProtectHome= */ { "/run/user", READWRITE, true }, /* ProtectHome= */ { "/root", READWRITE, true }, /* ProtectHome= */ }; static const char *mount_entry_path(const MountEntry *p) { assert(p); /* Returns the path of this bind mount. If the malloc()-allocated ->path_buffer field is set we return that, * otherwise the stack/static ->path field is returned. */ return p->path_malloc ?: p->path_const; } static bool mount_entry_read_only(const MountEntry *p) { assert(p); return p->read_only || IN_SET(p->mode, READONLY, INACCESSIBLE); } static const char *mount_entry_source(const MountEntry *p) { assert(p); return p->source_malloc ?: p->source_const; } static const char *mount_entry_options(const MountEntry *p) { assert(p); return p->options_malloc ?: p->options_const; } static void mount_entry_done(MountEntry *p) { assert(p); p->path_malloc = mfree(p->path_malloc); p->source_malloc = mfree(p->source_malloc); p->options_malloc = mfree(p->options_malloc); } static int append_access_mounts(MountEntry **p, char **strv, MountMode mode, bool forcibly_require_prefix) { char **i; assert(p); /* Adds a list of user-supplied READWRITE/READONLY/INACCESSIBLE entries */ STRV_FOREACH(i, strv) { bool ignore = false, needs_prefix = false; const char *e = *i; /* Look for any prefixes */ if (startswith(e, "-")) { e++; ignore = true; } if (startswith(e, "+")) { e++; needs_prefix = true; } if (!path_is_absolute(e)) { log_debug("Path is not absolute: %s", e); return -EINVAL; } *((*p)++) = (MountEntry) { .path_const = e, .mode = mode, .ignore = ignore, .has_prefix = !needs_prefix && !forcibly_require_prefix, }; } return 0; } static int append_empty_dir_mounts(MountEntry **p, char **strv) { char **i; assert(p); /* Adds tmpfs mounts to provide readable but empty directories. This is primarily used to implement the * "/private/" boundary directories for DynamicUser=1. */ STRV_FOREACH(i, strv) { *((*p)++) = (MountEntry) { .path_const = *i, .mode = EMPTY_DIR, .ignore = false, .read_only = true, .options_const = "mode=755", .flags = MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, }; } return 0; } static int append_bind_mounts(MountEntry **p, const BindMount *binds, size_t n) { size_t i; assert(p); for (i = 0; i < n; i++) { const BindMount *b = binds + i; *((*p)++) = (MountEntry) { .path_const = b->destination, .mode = b->recursive ? BIND_MOUNT_RECURSIVE : BIND_MOUNT, .read_only = b->read_only, .source_const = b->source, .ignore = b->ignore_enoent, }; } return 0; } static int append_tmpfs_mounts(MountEntry **p, const TemporaryFileSystem *tmpfs, size_t n) { size_t i; int r; assert(p); for (i = 0; i < n; i++) { const TemporaryFileSystem *t = tmpfs + i; _cleanup_free_ char *o = NULL, *str = NULL; unsigned long flags; bool ro = false; if (!path_is_absolute(t->path)) { log_debug("Path is not absolute: %s", t->path); return -EINVAL; } str = strjoin("mode=0755,", t->options); if (!str) return -ENOMEM; r = mount_option_mangle(str, MS_NODEV|MS_STRICTATIME, &flags, &o); if (r < 0) return log_debug_errno(r, "Failed to parse mount option '%s': %m", str); ro = flags & MS_RDONLY; if (ro) flags ^= MS_RDONLY; *((*p)++) = (MountEntry) { .path_const = t->path, .mode = TMPFS, .read_only = ro, .options_malloc = TAKE_PTR(o), .flags = flags, }; } return 0; } static int append_static_mounts(MountEntry **p, const MountEntry *mounts, size_t n, bool ignore_protect) { size_t i; assert(p); assert(mounts); /* Adds a list of static pre-defined entries */ for (i = 0; i < n; i++) *((*p)++) = (MountEntry) { .path_const = mount_entry_path(mounts+i), .mode = mounts[i].mode, .ignore = mounts[i].ignore || ignore_protect, }; return 0; } static int append_protect_home(MountEntry **p, ProtectHome protect_home, bool ignore_protect) { assert(p); switch (protect_home) { case PROTECT_HOME_NO: return 0; case PROTECT_HOME_READ_ONLY: return append_static_mounts(p, protect_home_read_only_table, ELEMENTSOF(protect_home_read_only_table), ignore_protect); case PROTECT_HOME_TMPFS: return append_static_mounts(p, protect_home_tmpfs_table, ELEMENTSOF(protect_home_tmpfs_table), ignore_protect); case PROTECT_HOME_YES: return append_static_mounts(p, protect_home_yes_table, ELEMENTSOF(protect_home_yes_table), ignore_protect); default: assert_not_reached("Unexpected ProtectHome= value"); } } static int append_protect_system(MountEntry **p, ProtectSystem protect_system, bool ignore_protect) { assert(p); switch (protect_system) { case PROTECT_SYSTEM_NO: return 0; case PROTECT_SYSTEM_STRICT: return append_static_mounts(p, protect_system_strict_table, ELEMENTSOF(protect_system_strict_table), ignore_protect); case PROTECT_SYSTEM_YES: return append_static_mounts(p, protect_system_yes_table, ELEMENTSOF(protect_system_yes_table), ignore_protect); case PROTECT_SYSTEM_FULL: return append_static_mounts(p, protect_system_full_table, ELEMENTSOF(protect_system_full_table), ignore_protect); default: assert_not_reached("Unexpected ProtectSystem= value"); } } static int mount_path_compare(const MountEntry *a, const MountEntry *b) { int d; /* If the paths are not equal, then order prefixes first */ d = path_compare(mount_entry_path(a), mount_entry_path(b)); if (d != 0) return d; /* If the paths are equal, check the mode */ return CMP((int) a->mode, (int) b->mode); } static int prefix_where_needed(MountEntry *m, size_t n, const char *root_directory) { size_t i; /* Prefixes all paths in the bind mount table with the root directory if the entry needs that. */ for (i = 0; i < n; i++) { char *s; if (m[i].has_prefix) continue; s = prefix_root(root_directory, mount_entry_path(m+i)); if (!s) return -ENOMEM; free_and_replace(m[i].path_malloc, s); m[i].has_prefix = true; } return 0; } static void drop_duplicates(MountEntry *m, size_t *n) { MountEntry *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. Note that we only drop duplicates that haven't been mounted yet. */ if (previous && path_equal(mount_entry_path(f), mount_entry_path(previous)) && !f->applied && !previous->applied) { log_debug("%s is duplicate.", mount_entry_path(f)); previous->read_only = previous->read_only || mount_entry_read_only(f); /* Propagate the read-only flag to the remaining entry */ mount_entry_done(f); continue; } *t = *f; previous = t; t++; } *n = t - m; } static void drop_inaccessible(MountEntry *m, size_t *n) { MountEntry *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(mount_entry_path(f), clear)) { log_debug("%s is masked by %s.", mount_entry_path(f), clear); mount_entry_done(f); continue; } clear = f->mode == INACCESSIBLE ? mount_entry_path(f) : NULL; *t = *f; t++; } *n = t - m; } static void drop_nop(MountEntry *m, size_t *n) { MountEntry *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)) { MountEntry *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(mount_entry_path(f), mount_entry_path(p))) { 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", mount_entry_path(f), mount_entry_path(p)); mount_entry_done(f); continue; } } *t = *f; t++; } *n = t - m; } static void drop_outside_root(const char *root_directory, MountEntry *m, size_t *n) { MountEntry *f, *t; assert(m); assert(n); /* Nothing to do */ 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(mount_entry_path(f), root_directory)) { log_debug("%s is outside of root directory.", mount_entry_path(f)); mount_entry_done(f); continue; } *t = *f; t++; } *n = t - m; } static int clone_device_node( const char *d, const char *temporary_mount, bool *make_devnode) { _cleanup_free_ char *sl = NULL; const char *dn, *bn, *t; struct stat st; int r; if (stat(d, &st) < 0) { if (errno == ENOENT) { log_debug_errno(errno, "Device node '%s' to clone does not exist, ignoring.", d); return -ENXIO; } return log_debug_errno(errno, "Failed to stat() device node '%s' to clone, ignoring: %m", d); } if (!S_ISBLK(st.st_mode) && !S_ISCHR(st.st_mode)) { log_debug("Device node '%s' to clone is not a device node, ignoring.", d); return -EINVAL; } dn = strjoina(temporary_mount, d); /* First, try to create device node properly */ if (*make_devnode) { 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) goto add_symlink; if (errno != EPERM) return log_debug_errno(errno, "mknod failed for %s: %m", d); /* This didn't work, let's not try this again for the next iterations. */ *make_devnode = false; } /* We're about to fallback to bind-mounting the device * node. So create a dummy bind-mount target. */ mac_selinux_create_file_prepare(d, 0); r = mknod(dn, S_IFREG, 0); mac_selinux_create_file_clear(); if (r < 0 && errno != EEXIST) return log_debug_errno(errno, "mknod() fallback failed for '%s': %m", d); /* Fallback to bind-mounting: * The assumption here is that all used device nodes carry standard * properties. Specifically, the devices nodes we bind-mount should * either be owned by root:root or root:tty (e.g. /dev/tty, /dev/ptmx) * and should not carry ACLs. */ if (mount(d, dn, NULL, MS_BIND, NULL) < 0) return log_debug_errno(errno, "Bind mounting failed for '%s': %m", d); add_symlink: bn = path_startswith(d, "/dev/"); if (!bn) return 0; /* Create symlinks like /dev/char/1:9 → ../urandom */ if (asprintf(&sl, "%s/dev/%s/%u:%u", temporary_mount, S_ISCHR(st.st_mode) ? "char" : "block", major(st.st_rdev), minor(st.st_rdev)) < 0) return log_oom(); (void) mkdir_parents(sl, 0755); t = strjoina("../", bn); if (symlink(t, sl) < 0) log_debug_errno(errno, "Failed to symlink '%s' to '%s', ignoring: %m", t, sl); return 0; } static int mount_private_dev(MountEntry *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; bool can_mknod = true; _cleanup_umask_ mode_t u; int r; assert(m); u = umask(0000); if (!mkdtemp(temporary_mount)) return log_debug_errno(errno, "Failed to create temporary directory '%s': %m", temporary_mount); dev = strjoina(temporary_mount, "/dev"); (void) mkdir(dev, 0755); if (mount("tmpfs", dev, "tmpfs", DEV_MOUNT_OPTIONS, "mode=755") < 0) { r = log_debug_errno(errno, "Failed to mount tmpfs on '%s': %m", dev); goto fail; } devpts = strjoina(temporary_mount, "/dev/pts"); (void) mkdir(devpts, 0755); if (mount("/dev/pts", devpts, NULL, MS_BIND, NULL) < 0) { r = log_debug_errno(errno, "Failed to bind mount /dev/pts on '%s': %m", devpts); goto fail; } /* /dev/ptmx can either be a device node or a symlink to /dev/pts/ptmx. * When /dev/ptmx a device node, /dev/pts/ptmx has 000 permissions making it inaccessible. * Thus, in that case make a clone. * In nspawn and other containers it will be a symlink, in that case make it a symlink. */ r = is_symlink("/dev/ptmx"); if (r < 0) { log_debug_errno(r, "Failed to detect whether /dev/ptmx is a symlink or not: %m"); goto fail; } else if (r > 0) { devptmx = strjoina(temporary_mount, "/dev/ptmx"); if (symlink("pts/ptmx", devptmx) < 0) { r = log_debug_errno(errno, "Failed to create a symlink '%s' to pts/ptmx: %m", devptmx); goto fail; } } else { r = clone_device_node("/dev/ptmx", temporary_mount, &can_mknod); if (r < 0) goto fail; } devshm = strjoina(temporary_mount, "/dev/shm"); (void) mkdir(devshm, 0755); r = mount("/dev/shm", devshm, NULL, MS_BIND, NULL); if (r < 0) { r = log_debug_errno(errno, "Failed to bind mount /dev/shm on '%s': %m", devshm); goto fail; } devmqueue = strjoina(temporary_mount, "/dev/mqueue"); (void) mkdir(devmqueue, 0755); if (mount("/dev/mqueue", devmqueue, NULL, MS_BIND, NULL) < 0) log_debug_errno(errno, "Failed to bind mount /dev/mqueue on '%s', ignoring: %m", devmqueue); devhugepages = strjoina(temporary_mount, "/dev/hugepages"); (void) mkdir(devhugepages, 0755); if (mount("/dev/hugepages", devhugepages, NULL, MS_BIND, NULL) < 0) log_debug_errno(errno, "Failed to bind mount /dev/hugepages on '%s', ignoring: %m", devhugepages); devlog = strjoina(temporary_mount, "/dev/log"); if (symlink("/run/systemd/journal/dev-log", devlog) < 0) log_debug_errno(errno, "Failed to create a symlink '%s' to /run/systemd/journal/dev-log, ignoring: %m", devlog); NULSTR_FOREACH(d, devnodes) { r = clone_device_node(d, temporary_mount, &can_mknod); /* ENXIO means the the *source* is not a device file, skip creation in that case */ if (r < 0 && r != -ENXIO) goto fail; } r = dev_setup(temporary_mount, UID_INVALID, GID_INVALID); if (r < 0) log_debug_errno(r, "Failed to setup basic device tree at '%s', ignoring: %m", temporary_mount); /* 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(mount_entry_path(m), 0755); /* Unmount everything in old /dev */ r = umount_recursive(mount_entry_path(m), 0); if (r < 0) log_debug_errno(r, "Failed to unmount directories below '%s', ignoring: %m", mount_entry_path(m)); if (mount(dev, mount_entry_path(m), NULL, MS_MOVE, NULL) < 0) { r = log_debug_errno(errno, "Failed to move mount point '%s' to '%s': %m", dev, mount_entry_path(m)); 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 mount_bind_dev(const MountEntry *m) { int r; assert(m); /* Implements the little brother of mount_private_dev(): simply bind mounts the host's /dev into the service's * /dev. This is only used when RootDirectory= is set. */ (void) mkdir_p_label(mount_entry_path(m), 0755); r = path_is_mount_point(mount_entry_path(m), NULL, 0); if (r < 0) return log_debug_errno(r, "Unable to determine whether /dev is already mounted: %m"); if (r > 0) /* make this a NOP if /dev is already a mount point */ return 0; if (mount("/dev", mount_entry_path(m), NULL, MS_BIND|MS_REC, NULL) < 0) return log_debug_errno(errno, "Failed to bind mount %s: %m", mount_entry_path(m)); return 1; } static int mount_sysfs(const MountEntry *m) { int r; assert(m); (void) mkdir_p_label(mount_entry_path(m), 0755); r = path_is_mount_point(mount_entry_path(m), NULL, 0); if (r < 0) return log_debug_errno(r, "Unable to determine whether /sys is already mounted: %m"); if (r > 0) /* make this a NOP if /sys is already a mount point */ return 0; /* Bind mount the host's version so that we get all child mounts of it, too. */ if (mount("/sys", mount_entry_path(m), NULL, MS_BIND|MS_REC, NULL) < 0) return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m)); return 1; } static int mount_procfs(const MountEntry *m) { int r; assert(m); (void) mkdir_p_label(mount_entry_path(m), 0755); r = path_is_mount_point(mount_entry_path(m), NULL, 0); if (r < 0) return log_debug_errno(r, "Unable to determine whether /proc is already mounted: %m"); if (r > 0) /* make this a NOP if /proc is already a mount point */ return 0; /* Mount a new instance, so that we get the one that matches our user namespace, if we are running in one */ if (mount("proc", mount_entry_path(m), "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) < 0) return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m)); return 1; } static int mount_tmpfs(const MountEntry *m) { assert(m); /* First, get rid of everything that is below if there is anything. Then, overmount with our new tmpfs */ (void) mkdir_p_label(mount_entry_path(m), 0755); (void) umount_recursive(mount_entry_path(m), 0); if (mount("tmpfs", mount_entry_path(m), "tmpfs", m->flags, mount_entry_options(m)) < 0) return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m)); return 1; } static int follow_symlink( const char *root_directory, MountEntry *m) { _cleanup_free_ char *target = NULL; int r; /* Let's chase symlinks, but only one step at a time. That's because depending where the symlink points we * might need to change the order in which we mount stuff. Hence: let's normalize piecemeal, and do one step at * a time by specifying CHASE_STEP. This function returns 0 if we resolved one step, and > 0 if we reached the * end and already have a fully normalized name. */ r = chase_symlinks(mount_entry_path(m), root_directory, CHASE_STEP|CHASE_NONEXISTENT, &target); if (r < 0) return log_debug_errno(r, "Failed to chase symlinks '%s': %m", mount_entry_path(m)); if (r > 0) /* Reached the end, nothing more to resolve */ return 1; if (m->n_followed >= CHASE_SYMLINKS_MAX) { /* put a boundary on things */ log_debug("Symlink loop on '%s'.", mount_entry_path(m)); return -ELOOP; } log_debug("Followed mount entry path symlink %s → %s.", mount_entry_path(m), target); free_and_replace(m->path_malloc, target); m->has_prefix = true; m->n_followed ++; return 0; } static int apply_mount( const char *root_directory, MountEntry *m) { bool rbind = true, make = false; const char *what; int r; assert(m); log_debug("Applying namespace mount on %s", mount_entry_path(m)); 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(mount_entry_path(m), 0); if (lstat(mount_entry_path(m), &target) < 0) { if (errno == ENOENT && m->ignore) return 0; return log_debug_errno(errno, "Failed to lstat() %s to determine what to mount over it: %m", mount_entry_path(m)); } 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(mount_entry_path(m), root_directory, 0); if (r == -ENOENT && m->ignore) return 0; if (r < 0) return log_debug_errno(r, "Failed to determine whether %s is already a mount point: %m", mount_entry_path(m)); 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 = mount_entry_path(m); break; case BIND_MOUNT: rbind = false; _fallthrough_; case BIND_MOUNT_RECURSIVE: { _cleanup_free_ char *chased = NULL; /* Since mount() will always follow symlinks we chase the symlinks on our own first. Note that bind * mount source paths are always relative to the host root, hence we pass NULL as root directory to * chase_symlinks() here. */ r = chase_symlinks(mount_entry_source(m), NULL, CHASE_TRAIL_SLASH, &chased); if (r == -ENOENT && m->ignore) { log_debug_errno(r, "Path %s does not exist, ignoring.", mount_entry_source(m)); return 0; } if (r < 0) return log_debug_errno(r, "Failed to follow symlinks on %s: %m", mount_entry_source(m)); log_debug("Followed source symlinks %s → %s.", mount_entry_source(m), chased); free_and_replace(m->source_malloc, chased); what = mount_entry_source(m); make = true; break; } case EMPTY_DIR: case TMPFS: return mount_tmpfs(m); case PRIVATE_TMP: what = mount_entry_source(m); make = true; break; case PRIVATE_DEV: return mount_private_dev(m); case BIND_DEV: return mount_bind_dev(m); case SYSFS: return mount_sysfs(m); case PROCFS: return mount_procfs(m); default: assert_not_reached("Unknown mode"); } assert(what); if (mount(what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL) < 0) { bool try_again = false; r = -errno; if (r == -ENOENT && make) { struct stat st; /* Hmm, either the source or the destination are missing. Let's see if we can create the destination, then try again */ if (stat(what, &st) < 0) log_debug_errno(errno, "Mount point source '%s' is not accessible: %m", what); else { int q; (void) mkdir_parents(mount_entry_path(m), 0755); if (S_ISDIR(st.st_mode)) q = mkdir(mount_entry_path(m), 0755) < 0 ? -errno : 0; else q = touch(mount_entry_path(m)); if (q < 0) log_debug_errno(q, "Failed to create destination mount point node '%s': %m", mount_entry_path(m)); else try_again = true; } } if (try_again) { if (mount(what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL) < 0) r = -errno; else r = 0; } if (r < 0) return log_debug_errno(r, "Failed to mount %s to %s: %m", what, mount_entry_path(m)); } log_debug("Successfully mounted %s to %s", what, mount_entry_path(m)); return 0; } /* Change the per-mount readonly flag on an existing mount */ static int remount_bind_readonly(const char *path, unsigned long orig_flags) { int r; r = mount(NULL, path, NULL, MS_REMOUNT | MS_BIND | MS_RDONLY | orig_flags, NULL); return r < 0 ? -errno : 0; } static int make_read_only(const MountEntry *m, char **blacklist, FILE *proc_self_mountinfo) { bool submounts = false; int r = 0; assert(m); assert(proc_self_mountinfo); if (mount_entry_read_only(m)) { if (IN_SET(m->mode, EMPTY_DIR, TMPFS)) { r = remount_bind_readonly(mount_entry_path(m), m->flags); } else { submounts = true; r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), true, blacklist, proc_self_mountinfo); } } else if (m->mode == PRIVATE_DEV) { /* Set /dev readonly, but not submounts like /dev/shm. Also, we only set the per-mount read-only flag. * We can't set it on the superblock, if we are inside a user namespace and running Linux <= 4.17. */ r = remount_bind_readonly(mount_entry_path(m), DEV_MOUNT_OPTIONS); } 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. */ if (r == -ENOENT && m->ignore) r = 0; if (r < 0) return log_debug_errno(r, "Failed to re-mount '%s'%s read-only: %m", mount_entry_path(m), submounts ? " and its submounts" : ""); return 0; } static bool namespace_info_mount_apivfs(const NamespaceInfo *ns_info) { assert(ns_info); /* * ProtectControlGroups= and ProtectKernelTunables= imply MountAPIVFS=, * since to protect the API VFS mounts, they need to be around in the * first place... */ return ns_info->mount_apivfs || ns_info->protect_control_groups || ns_info->protect_kernel_tunables; } static size_t namespace_calculate_mounts( const NamespaceInfo *ns_info, char** read_write_paths, char** read_only_paths, char** inaccessible_paths, char** empty_directories, size_t n_bind_mounts, size_t n_temporary_filesystems, const char* tmp_dir, const char* var_tmp_dir, ProtectHome protect_home, ProtectSystem protect_system) { size_t protect_home_cnt; size_t protect_system_cnt = (protect_system == PROTECT_SYSTEM_STRICT ? ELEMENTSOF(protect_system_strict_table) : ((protect_system == PROTECT_SYSTEM_FULL) ? ELEMENTSOF(protect_system_full_table) : ((protect_system == PROTECT_SYSTEM_YES) ? ELEMENTSOF(protect_system_yes_table) : 0))); protect_home_cnt = (protect_home == PROTECT_HOME_YES ? ELEMENTSOF(protect_home_yes_table) : ((protect_home == PROTECT_HOME_READ_ONLY) ? ELEMENTSOF(protect_home_read_only_table) : ((protect_home == PROTECT_HOME_TMPFS) ? ELEMENTSOF(protect_home_tmpfs_table) : 0))); return !!tmp_dir + !!var_tmp_dir + strv_length(read_write_paths) + strv_length(read_only_paths) + strv_length(inaccessible_paths) + strv_length(empty_directories) + n_bind_mounts + n_temporary_filesystems + ns_info->private_dev + (ns_info->protect_kernel_tunables ? ELEMENTSOF(protect_kernel_tunables_table) : 0) + (ns_info->protect_control_groups ? 1 : 0) + (ns_info->protect_kernel_modules ? ELEMENTSOF(protect_kernel_modules_table) : 0) + protect_home_cnt + protect_system_cnt + (namespace_info_mount_apivfs(ns_info) ? ELEMENTSOF(apivfs_table) : 0); } static void normalize_mounts(const char *root_directory, MountEntry *mounts, size_t *n_mounts) { assert(root_directory); assert(n_mounts); assert(mounts || *n_mounts == 0); typesafe_qsort(mounts, *n_mounts, mount_path_compare); drop_duplicates(mounts, n_mounts); drop_outside_root(root_directory, mounts, n_mounts); drop_inaccessible(mounts, n_mounts); drop_nop(mounts, n_mounts); } int setup_namespace( const char* root_directory, const char* root_image, const NamespaceInfo *ns_info, char** read_write_paths, char** read_only_paths, char** inaccessible_paths, char** empty_directories, const BindMount *bind_mounts, size_t n_bind_mounts, const TemporaryFileSystem *temporary_filesystems, size_t n_temporary_filesystems, const char* tmp_dir, const char* var_tmp_dir, ProtectHome protect_home, ProtectSystem protect_system, unsigned long mount_flags, DissectImageFlags dissect_image_flags) { _cleanup_(loop_device_unrefp) LoopDevice *loop_device = NULL; _cleanup_(decrypted_image_unrefp) DecryptedImage *decrypted_image = NULL; _cleanup_(dissected_image_unrefp) DissectedImage *dissected_image = NULL; _cleanup_free_ void *root_hash = NULL; MountEntry *m, *mounts = NULL; size_t n_mounts, root_hash_size = 0; bool require_prefix = false; const char *root; int r = 0; assert(ns_info); if (mount_flags == 0) mount_flags = MS_SHARED; if (root_image) { dissect_image_flags |= DISSECT_IMAGE_REQUIRE_ROOT; if (protect_system == PROTECT_SYSTEM_STRICT && protect_home != PROTECT_HOME_NO && strv_isempty(read_write_paths)) dissect_image_flags |= DISSECT_IMAGE_READ_ONLY; r = loop_device_make_by_path(root_image, dissect_image_flags & DISSECT_IMAGE_READ_ONLY ? O_RDONLY : O_RDWR, &loop_device); if (r < 0) return log_debug_errno(r, "Failed to create loop device for root image: %m"); r = root_hash_load(root_image, &root_hash, &root_hash_size); if (r < 0) return log_debug_errno(r, "Failed to load root hash: %m"); r = dissect_image(loop_device->fd, root_hash, root_hash_size, dissect_image_flags, &dissected_image); if (r < 0) return log_debug_errno(r, "Failed to dissect image: %m"); r = dissected_image_decrypt(dissected_image, NULL, root_hash, root_hash_size, dissect_image_flags, &decrypted_image); if (r < 0) return log_debug_errno(r, "Failed to decrypt dissected image: %m"); } if (root_directory) root = root_directory; else { /* Always create the mount namespace in a temporary directory, instead of operating * directly in the root. The temporary directory prevents any mounts from being * potentially obscured my other mounts we already applied. * We use the same mount point for all images, which is safe, since they all live * in their own namespaces after all, and hence won't see each other. */ root = "/run/systemd/unit-root"; (void) mkdir_label(root, 0700); require_prefix = true; } n_mounts = namespace_calculate_mounts( ns_info, read_write_paths, read_only_paths, inaccessible_paths, empty_directories, n_bind_mounts, n_temporary_filesystems, tmp_dir, var_tmp_dir, protect_home, protect_system); if (n_mounts > 0) { m = mounts = (MountEntry *) alloca0(n_mounts * sizeof(MountEntry)); r = append_access_mounts(&m, read_write_paths, READWRITE, require_prefix); if (r < 0) goto finish; r = append_access_mounts(&m, read_only_paths, READONLY, require_prefix); if (r < 0) goto finish; r = append_access_mounts(&m, inaccessible_paths, INACCESSIBLE, require_prefix); if (r < 0) goto finish; r = append_empty_dir_mounts(&m, empty_directories); if (r < 0) goto finish; r = append_bind_mounts(&m, bind_mounts, n_bind_mounts); if (r < 0) goto finish; r = append_tmpfs_mounts(&m, temporary_filesystems, n_temporary_filesystems); if (r < 0) goto finish; if (tmp_dir) { *(m++) = (MountEntry) { .path_const = "/tmp", .mode = PRIVATE_TMP, .source_const = tmp_dir, }; } if (var_tmp_dir) { *(m++) = (MountEntry) { .path_const = "/var/tmp", .mode = PRIVATE_TMP, .source_const = var_tmp_dir, }; } if (ns_info->private_dev) { *(m++) = (MountEntry) { .path_const = "/dev", .mode = PRIVATE_DEV, }; } if (ns_info->protect_kernel_tunables) { r = append_static_mounts(&m, protect_kernel_tunables_table, ELEMENTSOF(protect_kernel_tunables_table), ns_info->ignore_protect_paths); if (r < 0) goto finish; } if (ns_info->protect_kernel_modules) { r = append_static_mounts(&m, protect_kernel_modules_table, ELEMENTSOF(protect_kernel_modules_table), ns_info->ignore_protect_paths); if (r < 0) goto finish; } if (ns_info->protect_control_groups) { *(m++) = (MountEntry) { .path_const = "/sys/fs/cgroup", .mode = READONLY, }; } r = append_protect_home(&m, protect_home, ns_info->ignore_protect_paths); if (r < 0) goto finish; r = append_protect_system(&m, protect_system, false); if (r < 0) goto finish; if (namespace_info_mount_apivfs(ns_info)) { r = append_static_mounts(&m, apivfs_table, ELEMENTSOF(apivfs_table), ns_info->ignore_protect_paths); if (r < 0) goto finish; } assert(mounts + n_mounts == m); /* Prepend the root directory where that's necessary */ r = prefix_where_needed(mounts, n_mounts, root); if (r < 0) goto finish; normalize_mounts(root, mounts, &n_mounts); } /* All above is just preparation, figuring out what to do. Let's now actually start doing something. */ if (unshare(CLONE_NEWNS) < 0) { r = log_debug_errno(errno, "Failed to unshare the mount namespace: %m"); if (IN_SET(r, -EACCES, -EPERM, -EOPNOTSUPP, -ENOSYS)) /* If the kernel doesn't support namespaces, or when there's a MAC or seccomp filter in place * that doesn't allow us to create namespaces (or a missing cap), then propagate a recognizable * error back, which the caller can use to detect this case (and only this) and optionally * continue without namespacing applied. */ r = -ENOANO; goto finish; } /* 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 = log_debug_errno(errno, "Failed to remount '/' as SLAVE: %m"); goto finish; } if (root_image) { /* A root image is specified, mount it to the right place */ r = dissected_image_mount(dissected_image, root, UID_INVALID, dissect_image_flags); if (r < 0) { log_debug_errno(r, "Failed to mount root image: %m"); goto finish; } if (decrypted_image) { r = decrypted_image_relinquish(decrypted_image); if (r < 0) { log_debug_errno(r, "Failed to relinquish decrypted image: %m"); goto finish; } } loop_device_relinquish(loop_device); } else if (root_directory) { /* A root directory is specified. Turn its directory into bind mount, if it isn't one yet. */ r = path_is_mount_point(root, NULL, AT_SYMLINK_FOLLOW); if (r < 0) { log_debug_errno(r, "Failed to detect that %s is a mount point or not: %m", root); goto finish; } if (r == 0) { if (mount(root, root, NULL, MS_BIND|MS_REC, NULL) < 0) { r = log_debug_errno(errno, "Failed to bind mount '%s': %m", root); goto finish; } } } else { /* Let's mount the main root directory to the root directory to use */ if (mount("/", root, NULL, MS_BIND|MS_REC, NULL) < 0) { r = log_debug_errno(errno, "Failed to bind mount '/' on '%s': %m", root); goto finish; } } /* Try to set up the new root directory before mounting anything else there. */ if (root_image || root_directory) (void) base_filesystem_create(root, UID_INVALID, GID_INVALID); if (n_mounts > 0) { _cleanup_fclose_ FILE *proc_self_mountinfo = NULL; char **blacklist; size_t j; /* Open /proc/self/mountinfo now as it may become unavailable if we mount anything on top of /proc. * For example, this is the case with the option: 'InaccessiblePaths=/proc' */ proc_self_mountinfo = fopen("/proc/self/mountinfo", "re"); if (!proc_self_mountinfo) { r = log_debug_errno(errno, "Failed to open /proc/self/mountinfo: %m"); goto finish; } /* First round, establish all mounts we need */ for (;;) { bool again = false; for (m = mounts; m < mounts + n_mounts; ++m) { if (m->applied) continue; r = follow_symlink(root, m); if (r < 0) goto finish; if (r == 0) { /* We hit a symlinked mount point. The entry got rewritten and might point to a * very different place now. Let's normalize the changed list, and start from * the beginning. After all to mount the entry at the new location we might * need some other mounts first */ again = true; break; } r = apply_mount(root, m); if (r < 0) goto finish; m->applied = true; } if (!again) break; normalize_mounts(root, mounts, &n_mounts); } /* Create a blacklist we can pass to bind_mount_recursive() */ blacklist = newa(char*, n_mounts+1); for (j = 0; j < n_mounts; j++) blacklist[j] = (char*) mount_entry_path(mounts+j); blacklist[j] = NULL; /* Second round, flip the ro bits if necessary. */ for (m = mounts; m < mounts + n_mounts; ++m) { r = make_read_only(m, blacklist, proc_self_mountinfo); if (r < 0) goto finish; } } /* MS_MOVE does not work on MS_SHARED so the remount MS_SHARED will be done later */ r = mount_move_root(root); if (r < 0) { log_debug_errno(r, "Failed to mount root with MS_MOVE: %m"); goto finish; } /* Remount / as the desired mode. Note 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 = log_debug_errno(errno, "Failed to remount '/' with desired mount flags: %m"); goto finish; } r = 0; finish: for (m = mounts; m < mounts + n_mounts; m++) mount_entry_done(m); return r; } void bind_mount_free_many(BindMount *b, size_t n) { size_t i; assert(b || n == 0); for (i = 0; i < n; i++) { free(b[i].source); free(b[i].destination); } free(b); } int bind_mount_add(BindMount **b, size_t *n, const BindMount *item) { _cleanup_free_ char *s = NULL, *d = NULL; BindMount *c; assert(b); assert(n); assert(item); s = strdup(item->source); if (!s) return -ENOMEM; d = strdup(item->destination); if (!d) return -ENOMEM; c = reallocarray(*b, *n + 1, sizeof(BindMount)); if (!c) return -ENOMEM; *b = c; c[(*n) ++] = (BindMount) { .source = TAKE_PTR(s), .destination = TAKE_PTR(d), .read_only = item->read_only, .recursive = item->recursive, .ignore_enoent = item->ignore_enoent, }; return 0; } void temporary_filesystem_free_many(TemporaryFileSystem *t, size_t n) { size_t i; assert(t || n == 0); for (i = 0; i < n; i++) { free(t[i].path); free(t[i].options); } free(t); } int temporary_filesystem_add( TemporaryFileSystem **t, size_t *n, const char *path, const char *options) { _cleanup_free_ char *p = NULL, *o = NULL; TemporaryFileSystem *c; assert(t); assert(n); assert(path); p = strdup(path); if (!p) return -ENOMEM; if (!isempty(options)) { o = strdup(options); if (!o) return -ENOMEM; } c = reallocarray(*t, *n + 1, sizeof(TemporaryFileSystem)); if (!c) return -ENOMEM; *t = c; c[(*n) ++] = (TemporaryFileSystem) { .path = TAKE_PTR(p), .options = TAKE_PTR(o), }; return 0; } 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"); 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 = TAKE_PTR(x); 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; } bool ns_type_supported(NamespaceType type) { const char *t, *ns_proc; t = namespace_type_to_string(type); if (!t) /* Don't know how to translate this? Then it's not supported */ return false; ns_proc = strjoina("/proc/self/ns/", t); return access(ns_proc, F_OK) == 0; } static const char *const protect_home_table[_PROTECT_HOME_MAX] = { [PROTECT_HOME_NO] = "no", [PROTECT_HOME_YES] = "yes", [PROTECT_HOME_READ_ONLY] = "read-only", [PROTECT_HOME_TMPFS] = "tmpfs", }; DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(protect_home, ProtectHome, PROTECT_HOME_YES); 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_WITH_BOOLEAN(protect_system, ProtectSystem, PROTECT_SYSTEM_YES); static const char* const namespace_type_table[] = { [NAMESPACE_MOUNT] = "mnt", [NAMESPACE_CGROUP] = "cgroup", [NAMESPACE_UTS] = "uts", [NAMESPACE_IPC] = "ipc", [NAMESPACE_USER] = "user", [NAMESPACE_PID] = "pid", [NAMESPACE_NET] = "net", }; DEFINE_STRING_TABLE_LOOKUP(namespace_type, NamespaceType);