/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include "errno-util.h" #include "fd-util.h" #include "fileio.h" #include "missing_fs.h" #include "missing_magic.h" #include "missing_sched.h" #include "namespace-util.h" #include "parse-util.h" #include "process-util.h" #include "stat-util.h" #include "stdio-util.h" #include "user-util.h" const struct namespace_info namespace_info[] = { [NAMESPACE_CGROUP] = { "cgroup", "ns/cgroup", CLONE_NEWCGROUP, }, [NAMESPACE_IPC] = { "ipc", "ns/ipc", CLONE_NEWIPC, }, [NAMESPACE_NET] = { "net", "ns/net", CLONE_NEWNET, }, /* So, the mount namespace flag is called CLONE_NEWNS for historical * reasons. Let's expose it here under a more explanatory name: "mnt". * This is in-line with how the kernel exposes namespaces in /proc/$PID/ns. */ [NAMESPACE_MOUNT] = { "mnt", "ns/mnt", CLONE_NEWNS, }, [NAMESPACE_PID] = { "pid", "ns/pid", CLONE_NEWPID, }, [NAMESPACE_USER] = { "user", "ns/user", CLONE_NEWUSER, }, [NAMESPACE_UTS] = { "uts", "ns/uts", CLONE_NEWUTS, }, [NAMESPACE_TIME] = { "time", "ns/time", CLONE_NEWTIME, }, { /* Allow callers to iterate over the array without using _NAMESPACE_TYPE_MAX. */ }, }; #define pid_namespace_path(pid, type) procfs_file_alloca(pid, namespace_info[type].proc_path) static NamespaceType clone_flag_to_namespace_type(unsigned long clone_flag) { for (NamespaceType t = 0; t < _NAMESPACE_TYPE_MAX; t++) if (((namespace_info[t].clone_flag ^ clone_flag) & (CLONE_NEWCGROUP|CLONE_NEWIPC|CLONE_NEWNET|CLONE_NEWNS|CLONE_NEWPID|CLONE_NEWUSER|CLONE_NEWUTS|CLONE_NEWTIME)) == 0) return t; return _NAMESPACE_TYPE_INVALID; } int namespace_open( pid_t pid, int *ret_pidns_fd, int *ret_mntns_fd, int *ret_netns_fd, int *ret_userns_fd, int *ret_root_fd) { _cleanup_close_ int pidns_fd = -EBADF, mntns_fd = -EBADF, netns_fd = -EBADF, userns_fd = -EBADF, root_fd = -EBADF; assert(pid >= 0); if (ret_pidns_fd) { const char *pidns; pidns = pid_namespace_path(pid, NAMESPACE_PID); pidns_fd = open(pidns, O_RDONLY|O_NOCTTY|O_CLOEXEC); if (pidns_fd < 0) return -errno; } if (ret_mntns_fd) { const char *mntns; mntns = pid_namespace_path(pid, NAMESPACE_MOUNT); mntns_fd = open(mntns, O_RDONLY|O_NOCTTY|O_CLOEXEC); if (mntns_fd < 0) return -errno; } if (ret_netns_fd) { const char *netns; netns = pid_namespace_path(pid, NAMESPACE_NET); netns_fd = open(netns, O_RDONLY|O_NOCTTY|O_CLOEXEC); if (netns_fd < 0) return -errno; } if (ret_userns_fd) { const char *userns; userns = pid_namespace_path(pid, NAMESPACE_USER); userns_fd = open(userns, O_RDONLY|O_NOCTTY|O_CLOEXEC); if (userns_fd < 0 && errno != ENOENT) return -errno; } if (ret_root_fd) { const char *root; root = procfs_file_alloca(pid, "root"); root_fd = open(root, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY); if (root_fd < 0) return -errno; } if (ret_pidns_fd) *ret_pidns_fd = TAKE_FD(pidns_fd); if (ret_mntns_fd) *ret_mntns_fd = TAKE_FD(mntns_fd); if (ret_netns_fd) *ret_netns_fd = TAKE_FD(netns_fd); if (ret_userns_fd) *ret_userns_fd = TAKE_FD(userns_fd); if (ret_root_fd) *ret_root_fd = TAKE_FD(root_fd); return 0; } int namespace_enter(int pidns_fd, int mntns_fd, int netns_fd, int userns_fd, int root_fd) { int r; if (userns_fd >= 0) { /* Can't setns to your own userns, since then you could escalate from non-root to root in * your own namespace, so check if namespaces are equal before attempting to enter. */ r = inode_same_at(userns_fd, "", AT_FDCWD, "/proc/self/ns/user", AT_EMPTY_PATH); if (r < 0) return r; if (r) userns_fd = -EBADF; } if (pidns_fd >= 0) if (setns(pidns_fd, CLONE_NEWPID) < 0) return -errno; if (mntns_fd >= 0) if (setns(mntns_fd, CLONE_NEWNS) < 0) return -errno; if (netns_fd >= 0) if (setns(netns_fd, CLONE_NEWNET) < 0) return -errno; if (userns_fd >= 0) if (setns(userns_fd, CLONE_NEWUSER) < 0) return -errno; if (root_fd >= 0) { if (fchdir(root_fd) < 0) return -errno; if (chroot(".") < 0) return -errno; } return reset_uid_gid(); } int fd_is_ns(int fd, unsigned long nsflag) { struct statfs s; int r; /* Checks whether the specified file descriptor refers to a namespace created by specifying nsflag in clone(). * On old kernels there's no nice way to detect that, hence on those we'll return a recognizable error (EUCLEAN), * so that callers can handle this somewhat nicely. * * This function returns > 0 if the fd definitely refers to a network namespace, 0 if it definitely does not * refer to a network namespace, -EUCLEAN if we can't determine, and other negative error codes on error. */ if (fstatfs(fd, &s) < 0) return -errno; if (!is_fs_type(&s, NSFS_MAGIC)) { /* On really old kernels, there was no "nsfs", and network namespace sockets belonged to procfs * instead. Handle that in a somewhat smart way. */ if (is_fs_type(&s, PROC_SUPER_MAGIC)) { struct statfs t; /* OK, so it is procfs. Let's see if our own network namespace is procfs, too. If so, then the * passed fd might refer to a network namespace, but we can't know for sure. In that case, * return a recognizable error. */ if (statfs("/proc/self/ns/net", &t) < 0) return -errno; if (s.f_type == t.f_type) return -EUCLEAN; /* It's possible, we simply don't know */ } return 0; /* No! */ } r = ioctl(fd, NS_GET_NSTYPE); if (r < 0) { if (errno == ENOTTY) /* Old kernels didn't know this ioctl, let's also return a recognizable error in that case */ return -EUCLEAN; return -errno; } return (unsigned long) r == nsflag; } int detach_mount_namespace(void) { /* Detaches the mount namespace, disabling propagation from our namespace to the host. Sets * propagation first to MS_SLAVE for all mounts (disabling propagation), and then back to MS_SHARED * (so that we create a new peer group). */ if (unshare(CLONE_NEWNS) < 0) return log_debug_errno(errno, "Failed to acquire mount namespace: %m"); if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) < 0) return log_debug_errno(errno, "Failed to set mount propagation to MS_SLAVE for all mounts: %m"); if (mount(NULL, "/", NULL, MS_SHARED | MS_REC, NULL) < 0) return log_debug_errno(errno, "Failed to set mount propagation back to MS_SHARED for all mounts: %m"); return 0; } int detach_mount_namespace_harder(uid_t target_uid, gid_t target_gid) { int r; /* Tried detach_mount_namespace() first. If that doesn't work due to permissions, opens up an * unprivileged user namespace with a mapping of the originating UID/GID to the specified target * UID/GID. Then, tries detach_mount_namespace() again. * * Or in other words: tries much harder to get a mount namespace, making use of unprivileged user * namespaces if need be. * * Note that after this function completed: * * → if we had privs, afterwards uids/gids on files and processes are as before * * → if we had no privs, our own id and all our files will show up owned by target_uid/target_gid, * and everything else owned by nobody. * * Yes, that's quite a difference. */ if (!uid_is_valid(target_uid)) return -EINVAL; if (!gid_is_valid(target_gid)) return -EINVAL; r = detach_mount_namespace(); if (r != -EPERM) return r; if (unshare(CLONE_NEWUSER) < 0) return log_debug_errno(errno, "Failed to acquire user namespace: %m"); r = write_string_filef("/proc/self/uid_map", 0, UID_FMT " " UID_FMT " 1\n", target_uid, getuid()); if (r < 0) return log_debug_errno(r, "Failed to write uid map: %m"); r = write_string_file("/proc/self/setgroups", "deny", 0); if (r < 0) return log_debug_errno(r, "Failed to write setgroups file: %m"); r = write_string_filef("/proc/self/gid_map", 0, GID_FMT " " GID_FMT " 1\n", target_gid, getgid()); if (r < 0) return log_debug_errno(r, "Failed to write gid map: %m"); return detach_mount_namespace(); } int detach_mount_namespace_userns(int userns_fd) { int r; assert(userns_fd >= 0); if (setns(userns_fd, CLONE_NEWUSER) < 0) return log_debug_errno(errno, "Failed to join user namespace: %m"); r = reset_uid_gid(); if (r < 0) return log_debug_errno(r, "Failed to become root in user namespace: %m"); return detach_mount_namespace(); } int userns_acquire_empty(void) { _cleanup_(sigkill_waitp) pid_t pid = 0; _cleanup_close_ int userns_fd = -EBADF; int r; r = safe_fork("(sd-mkuserns)", FORK_CLOSE_ALL_FDS|FORK_DEATHSIG_SIGKILL|FORK_NEW_USERNS, &pid); if (r < 0) return r; if (r == 0) /* Child. We do nothing here, just freeze until somebody kills us. */ freeze(); r = namespace_open(pid, NULL, NULL, NULL, &userns_fd, NULL); if (r < 0) return log_error_errno(r, "Failed to open userns fd: %m"); return TAKE_FD(userns_fd); } int userns_acquire(const char *uid_map, const char *gid_map) { char path[STRLEN("/proc//uid_map") + DECIMAL_STR_MAX(pid_t) + 1]; _cleanup_(sigkill_waitp) pid_t pid = 0; _cleanup_close_ int userns_fd = -EBADF; int r; assert(uid_map); assert(gid_map); /* Forks off a process in a new userns, configures the specified uidmap/gidmap, acquires an fd to it, * and then kills the process again. This way we have a userns fd that is not bound to any * process. We can use that for file system mounts and similar. */ r = safe_fork("(sd-mkuserns)", FORK_CLOSE_ALL_FDS|FORK_DEATHSIG_SIGKILL|FORK_NEW_USERNS, &pid); if (r < 0) return log_debug_errno(r, "Failed to fork process (sd-mkuserns): %m"); if (r == 0) /* Child. We do nothing here, just freeze until somebody kills us. */ freeze(); xsprintf(path, "/proc/" PID_FMT "/uid_map", pid); r = write_string_file(path, uid_map, WRITE_STRING_FILE_DISABLE_BUFFER); if (r < 0) return log_debug_errno(r, "Failed to write UID map: %m"); xsprintf(path, "/proc/" PID_FMT "/gid_map", pid); r = write_string_file(path, gid_map, WRITE_STRING_FILE_DISABLE_BUFFER); if (r < 0) return log_debug_errno(r, "Failed to write GID map: %m"); r = namespace_open(pid, /* ret_pidns_fd = */ NULL, /* ret_mntns_fd = */ NULL, /* ret_netns_fd = */ NULL, &userns_fd, /* ret_root_fd = */ NULL); if (r < 0) return log_debug_errno(r, "Failed to open userns fd: %m"); return TAKE_FD(userns_fd); } int netns_acquire(void) { _cleanup_(sigkill_waitp) pid_t pid = 0; _cleanup_close_ int netns_fd = -EBADF; int r; /* Forks off a process in a new network namespace, acquires a network namespace fd, and then kills * the process again. This way we have a netns fd that is not bound to any process. */ r = safe_fork("(sd-mknetns)", FORK_CLOSE_ALL_FDS|FORK_DEATHSIG_SIGKILL|FORK_NEW_NETNS, &pid); if (r < 0) return log_debug_errno(r, "Failed to fork process (sd-mknetns): %m"); if (r == 0) /* Child. We do nothing here, just freeze until somebody kills us. */ freeze(); r = namespace_open(pid, /* ret_pidns_fd = */ NULL, /* ret_mntns_fd = */ NULL, &netns_fd, /* ret_userns_fd = */ NULL, /* ret_root_fd = */ NULL); if (r < 0) return log_debug_errno(r, "Failed to open netns fd: %m"); return TAKE_FD(netns_fd); } int in_same_namespace(pid_t pid1, pid_t pid2, NamespaceType type) { const char *ns_path; struct stat ns_st1, ns_st2; if (pid1 == 0) pid1 = getpid_cached(); if (pid2 == 0) pid2 = getpid_cached(); if (pid1 == pid2) return 1; ns_path = pid_namespace_path(pid1, type); if (stat(ns_path, &ns_st1) < 0) return -errno; ns_path = pid_namespace_path(pid2, type); if (stat(ns_path, &ns_st2) < 0) return -errno; return stat_inode_same(&ns_st1, &ns_st2); } int parse_userns_uid_range(const char *s, uid_t *ret_uid_shift, uid_t *ret_uid_range) { _cleanup_free_ char *buffer = NULL; const char *range, *shift; int r; uid_t uid_shift, uid_range = 65536; assert(s); range = strchr(s, ':'); if (range) { buffer = strndup(s, range - s); if (!buffer) return log_oom(); shift = buffer; range++; r = safe_atou32(range, &uid_range); if (r < 0) return log_error_errno(r, "Failed to parse UID range \"%s\": %m", range); } else shift = s; r = parse_uid(shift, &uid_shift); if (r < 0) return log_error_errno(r, "Failed to parse UID \"%s\": %m", s); if (!userns_shift_range_valid(uid_shift, uid_range)) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "UID range cannot be empty or go beyond " UID_FMT ".", UID_INVALID); if (ret_uid_shift) *ret_uid_shift = uid_shift; if (ret_uid_range) *ret_uid_range = uid_range; return 0; } int namespace_open_by_type(NamespaceType type) { const char *p; int fd; assert(type >= 0); assert(type < _NAMESPACE_TYPE_MAX); p = pid_namespace_path(0, type); fd = RET_NERRNO(open(p, O_RDONLY|O_NOCTTY|O_CLOEXEC)); if (fd == -ENOENT && proc_mounted() == 0) return -ENOSYS; return fd; } int is_our_namespace(int fd, NamespaceType request_type) { int clone_flag; assert(fd >= 0); clone_flag = ioctl(fd, NS_GET_NSTYPE); if (clone_flag < 0) return -errno; NamespaceType found_type = clone_flag_to_namespace_type(clone_flag); if (found_type < 0) return -EBADF; /* Uh? Unknown namespace type? */ if (request_type >= 0 && request_type != found_type) /* It's a namespace, but not of the right type? */ return -EUCLEAN; struct stat st_fd, st_ours; if (fstat(fd, &st_fd) < 0) return -errno; const char *p = pid_namespace_path(0, found_type); if (stat(p, &st_ours) < 0) { if (errno == ENOENT) return proc_mounted() == 0 ? -ENOSYS : -ENOENT; return -errno; } return stat_inode_same(&st_ours, &st_fd); }