/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include #include #include "alloc-util.h" #include "blockdev-util.h" #include "dirent-util.h" #include "fd-util.h" #include "fileio.h" #include "fs-util.h" #include "locale-util.h" #include "log.h" #include "macro.h" #include "missing_fcntl.h" #include "missing_fs.h" #include "missing_syscall.h" #include "mkdir.h" #include "parse-util.h" #include "path-util.h" #include "process-util.h" #include "random-util.h" #include "stat-util.h" #include "stdio-util.h" #include "string-util.h" #include "strv.h" #include "time-util.h" #include "tmpfile-util.h" #include "user-util.h" #include "util.h" int unlink_noerrno(const char *path) { PROTECT_ERRNO; int r; r = unlink(path); if (r < 0) return -errno; return 0; } int rmdir_parents(const char *path, const char *stop) { size_t l; int r = 0; assert(path); assert(stop); l = strlen(path); /* Skip trailing slashes */ while (l > 0 && path[l-1] == '/') l--; while (l > 0) { char *t; /* Skip last component */ while (l > 0 && path[l-1] != '/') l--; /* Skip trailing slashes */ while (l > 0 && path[l-1] == '/') l--; if (l <= 0) break; t = strndup(path, l); if (!t) return -ENOMEM; if (path_startswith(stop, t)) { free(t); return 0; } r = rmdir(t); free(t); if (r < 0) if (errno != ENOENT) return -errno; } return 0; } int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) { int r; /* Try the ideal approach first */ if (renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE) >= 0) return 0; /* renameat2() exists since Linux 3.15, btrfs and FAT added support for it later. If it is not implemented, * fall back to a different method. */ if (!ERRNO_IS_NOT_SUPPORTED(errno) && errno != EINVAL) return -errno; /* Let's try to use linkat()+unlinkat() as fallback. This doesn't work on directories and on some file systems * that do not support hard links (such as FAT, most prominently), but for files it's pretty close to what we * want — though not atomic (i.e. for a short period both the new and the old filename will exist). */ if (linkat(olddirfd, oldpath, newdirfd, newpath, 0) >= 0) { if (unlinkat(olddirfd, oldpath, 0) < 0) { r = -errno; /* Backup errno before the following unlinkat() alters it */ (void) unlinkat(newdirfd, newpath, 0); return r; } return 0; } if (!ERRNO_IS_NOT_SUPPORTED(errno) && !IN_SET(errno, EINVAL, EPERM)) /* FAT returns EPERM on link()â€Ļ */ return -errno; /* OK, neither RENAME_NOREPLACE nor linkat()+unlinkat() worked. Let's then fall back to the racy TOCTOU * vulnerable accessat(F_OK) check followed by classic, replacing renameat(), we have nothing better. */ if (faccessat(newdirfd, newpath, F_OK, AT_SYMLINK_NOFOLLOW) >= 0) return -EEXIST; if (errno != ENOENT) return -errno; if (renameat(olddirfd, oldpath, newdirfd, newpath) < 0) return -errno; return 0; } int readlinkat_malloc(int fd, const char *p, char **ret) { size_t l = PATH_MAX; assert(p); assert(ret); for (;;) { _cleanup_free_ char *c = NULL; ssize_t n; c = new(char, l+1); if (!c) return -ENOMEM; n = readlinkat(fd, p, c, l); if (n < 0) return -errno; if ((size_t) n < l) { c[n] = 0; *ret = TAKE_PTR(c); return 0; } if (l > (SSIZE_MAX-1)/2) /* readlinkat() returns an ssize_t, and we want an extra byte for a * trailing NUL, hence do an overflow check relative to SSIZE_MAX-1 * here */ return -EFBIG; l *= 2; } } int readlink_malloc(const char *p, char **ret) { return readlinkat_malloc(AT_FDCWD, p, ret); } int readlink_value(const char *p, char **ret) { _cleanup_free_ char *link = NULL; char *value; int r; r = readlink_malloc(p, &link); if (r < 0) return r; value = basename(link); if (!value) return -ENOENT; value = strdup(value); if (!value) return -ENOMEM; *ret = value; return 0; } int readlink_and_make_absolute(const char *p, char **r) { _cleanup_free_ char *target = NULL; char *k; int j; assert(p); assert(r); j = readlink_malloc(p, &target); if (j < 0) return j; k = file_in_same_dir(p, target); if (!k) return -ENOMEM; *r = k; return 0; } int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) { _cleanup_close_ int fd = -1; assert(path); fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW); /* Let's acquire an O_PATH fd, as precaution to change * mode/owner on the same file */ if (fd < 0) return -errno; return fchmod_and_chown(fd, mode, uid, gid); } int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) { bool do_chown, do_chmod; struct stat st; int r; /* Change ownership and access mode of the specified fd. Tries to do so safely, ensuring that at no * point in time the access mode is above the old access mode under the old ownership or the new * access mode under the new ownership. Note: this call tries hard to leave the access mode * unaffected if the uid/gid is changed, i.e. it undoes implicit suid/sgid dropping the kernel does * on chown(). * * This call is happy with O_PATH fds. */ if (fstat(fd, &st) < 0) return -errno; do_chown = (uid != UID_INVALID && st.st_uid != uid) || (gid != GID_INVALID && st.st_gid != gid); do_chmod = !S_ISLNK(st.st_mode) && /* chmod is not defined on symlinks */ ((mode != MODE_INVALID && ((st.st_mode ^ mode) & 07777) != 0) || do_chown); /* If we change ownership, make sure we reset the mode afterwards, since chown() * modifies the access mode too */ if (mode == MODE_INVALID) mode = st.st_mode; /* If we only shall do a chown(), save original mode, since chown() might break it. */ else if ((mode & S_IFMT) != 0 && ((mode ^ st.st_mode) & S_IFMT) != 0) return -EINVAL; /* insist on the right file type if it was specified */ if (do_chown && do_chmod) { mode_t minimal = st.st_mode & mode; /* the subset of the old and the new mask */ if (((minimal ^ st.st_mode) & 07777) != 0) { r = fchmod_opath(fd, minimal & 07777); if (r < 0) return r; } } if (do_chown) if (fchownat(fd, "", uid, gid, AT_EMPTY_PATH) < 0) return -errno; if (do_chmod) { r = fchmod_opath(fd, mode & 07777); if (r < 0) return r; } return do_chown || do_chmod; } int fchmod_umask(int fd, mode_t m) { mode_t u; int r; u = umask(0777); r = fchmod(fd, m & (~u)) < 0 ? -errno : 0; umask(u); return r; } int fchmod_opath(int fd, mode_t m) { char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; /* This function operates also on fd that might have been opened with * O_PATH. Indeed fchmodat() doesn't have the AT_EMPTY_PATH flag like * fchownat() does. */ xsprintf(procfs_path, "/proc/self/fd/%i", fd); if (chmod(procfs_path, m) < 0) { if (errno != ENOENT) return -errno; if (proc_mounted() == 0) return -ENOSYS; /* if we have no /proc/, the concept is not implementable */ return -ENOENT; } return 0; } int futimens_opath(int fd, const struct timespec ts[2]) { char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; /* Similar to fchmod_path() but for futimens() */ xsprintf(procfs_path, "/proc/self/fd/%i", fd); if (utimensat(AT_FDCWD, procfs_path, ts, 0) < 0) { if (errno != ENOENT) return -errno; if (proc_mounted() == 0) return -ENOSYS; /* if we have no /proc/, the concept is not implementable */ return -ENOENT; } return 0; } int stat_warn_permissions(const char *path, const struct stat *st) { assert(path); assert(st); /* Don't complain if we are reading something that is not a file, for example /dev/null */ if (!S_ISREG(st->st_mode)) return 0; if (st->st_mode & 0111) log_warning("Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway.", path); if (st->st_mode & 0002) log_warning("Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway.", path); if (getpid_cached() == 1 && (st->st_mode & 0044) != 0044) log_warning("Configuration file %s is marked world-inaccessible. This has no effect as configuration data is accessible via APIs without restrictions. Proceeding anyway.", path); return 0; } int fd_warn_permissions(const char *path, int fd) { struct stat st; assert(path); assert(fd >= 0); if (fstat(fd, &st) < 0) return -errno; return stat_warn_permissions(path, &st); } int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) { char fdpath[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; _cleanup_close_ int fd = -1; int r, ret = 0; assert(path); /* Note that touch_file() does not follow symlinks: if invoked on an existing symlink, then it is the symlink * itself which is updated, not its target * * Returns the first error we encounter, but tries to apply as much as possible. */ if (parents) (void) mkdir_parents(path, 0755); /* Initially, we try to open the node with O_PATH, so that we get a reference to the node. This is useful in * case the path refers to an existing device or socket node, as we can open it successfully in all cases, and * won't trigger any driver magic or so. */ fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW); if (fd < 0) { if (errno != ENOENT) return -errno; /* if the node doesn't exist yet, we create it, but with O_EXCL, so that we only create a regular file * here, and nothing else */ fd = open(path, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, IN_SET(mode, 0, MODE_INVALID) ? 0644 : mode); if (fd < 0) return -errno; } /* Let's make a path from the fd, and operate on that. With this logic, we can adjust the access mode, * ownership and time of the file node in all cases, even if the fd refers to an O_PATH object — which is * something fchown(), fchmod(), futimensat() don't allow. */ xsprintf(fdpath, "/proc/self/fd/%i", fd); ret = fchmod_and_chown(fd, mode, uid, gid); if (stamp != USEC_INFINITY) { struct timespec ts[2]; timespec_store(&ts[0], stamp); ts[1] = ts[0]; r = utimensat(AT_FDCWD, fdpath, ts, 0); } else r = utimensat(AT_FDCWD, fdpath, NULL, 0); if (r < 0 && ret >= 0) return -errno; return ret; } int touch(const char *path) { return touch_file(path, false, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID); } int symlink_idempotent(const char *from, const char *to, bool make_relative) { _cleanup_free_ char *relpath = NULL; int r; assert(from); assert(to); if (make_relative) { _cleanup_free_ char *parent = NULL; r = path_extract_directory(to, &parent); if (r < 0) return r; r = path_make_relative(parent, from, &relpath); if (r < 0) return r; from = relpath; } if (symlink(from, to) < 0) { _cleanup_free_ char *p = NULL; if (errno != EEXIST) return -errno; r = readlink_malloc(to, &p); if (r == -EINVAL) /* Not a symlink? In that case return the original error we encountered: -EEXIST */ return -EEXIST; if (r < 0) /* Any other error? In that case propagate it as is */ return r; if (!streq(p, from)) /* Not the symlink we want it to be? In that case, propagate the original -EEXIST */ return -EEXIST; } return 0; } int symlink_atomic(const char *from, const char *to) { _cleanup_free_ char *t = NULL; int r; assert(from); assert(to); r = tempfn_random(to, NULL, &t); if (r < 0) return r; if (symlink(from, t) < 0) return -errno; if (rename(t, to) < 0) { unlink_noerrno(t); return -errno; } return 0; } int mknod_atomic(const char *path, mode_t mode, dev_t dev) { _cleanup_free_ char *t = NULL; int r; assert(path); r = tempfn_random(path, NULL, &t); if (r < 0) return r; if (mknod(t, mode, dev) < 0) return -errno; if (rename(t, path) < 0) { unlink_noerrno(t); return -errno; } return 0; } int mkfifo_atomic(const char *path, mode_t mode) { _cleanup_free_ char *t = NULL; int r; assert(path); r = tempfn_random(path, NULL, &t); if (r < 0) return r; if (mkfifo(t, mode) < 0) return -errno; if (rename(t, path) < 0) { unlink_noerrno(t); return -errno; } return 0; } int mkfifoat_atomic(int dirfd, const char *path, mode_t mode) { _cleanup_free_ char *t = NULL; int r; assert(path); if (path_is_absolute(path)) return mkfifo_atomic(path, mode); /* We're only interested in the (random) filename. */ r = tempfn_random_child("", NULL, &t); if (r < 0) return r; if (mkfifoat(dirfd, t, mode) < 0) return -errno; if (renameat(dirfd, t, dirfd, path) < 0) { unlink_noerrno(t); return -errno; } return 0; } int get_files_in_directory(const char *path, char ***list) { _cleanup_closedir_ DIR *d = NULL; struct dirent *de; size_t bufsize = 0, n = 0; _cleanup_strv_free_ char **l = NULL; assert(path); /* Returns all files in a directory in *list, and the number * of files as return value. If list is NULL returns only the * number. */ d = opendir(path); if (!d) return -errno; FOREACH_DIRENT_ALL(de, d, return -errno) { dirent_ensure_type(d, de); if (!dirent_is_file(de)) continue; if (list) { /* one extra slot is needed for the terminating NULL */ if (!GREEDY_REALLOC(l, bufsize, n + 2)) return -ENOMEM; l[n] = strdup(de->d_name); if (!l[n]) return -ENOMEM; l[++n] = NULL; } else n++; } if (list) *list = TAKE_PTR(l); return n; } static int getenv_tmp_dir(const char **ret_path) { const char *n; int r, ret = 0; assert(ret_path); /* We use the same order of environment variables python uses in tempfile.gettempdir(): * https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */ FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") { const char *e; e = secure_getenv(n); if (!e) continue; if (!path_is_absolute(e)) { r = -ENOTDIR; goto next; } if (!path_is_normalized(e)) { r = -EPERM; goto next; } r = is_dir(e, true); if (r < 0) goto next; if (r == 0) { r = -ENOTDIR; goto next; } *ret_path = e; return 1; next: /* Remember first error, to make this more debuggable */ if (ret >= 0) ret = r; } if (ret < 0) return ret; *ret_path = NULL; return ret; } static int tmp_dir_internal(const char *def, const char **ret) { const char *e; int r, k; assert(def); assert(ret); r = getenv_tmp_dir(&e); if (r > 0) { *ret = e; return 0; } k = is_dir(def, true); if (k == 0) k = -ENOTDIR; if (k < 0) return r < 0 ? r : k; *ret = def; return 0; } int var_tmp_dir(const char **ret) { /* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus * even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is * returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR, * making it a variable that overrides all temporary file storage locations. */ return tmp_dir_internal("/var/tmp", ret); } int tmp_dir(const char **ret) { /* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually * backed by an in-memory file system: /tmp. */ return tmp_dir_internal("/tmp", ret); } int unlink_or_warn(const char *filename) { if (unlink(filename) < 0 && errno != ENOENT) /* If the file doesn't exist and the fs simply was read-only (in which * case unlink() returns EROFS even if the file doesn't exist), don't * complain */ if (errno != EROFS || access(filename, F_OK) >= 0) return log_error_errno(errno, "Failed to remove \"%s\": %m", filename); return 0; } int inotify_add_watch_fd(int fd, int what, uint32_t mask) { char path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; int wd; /* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */ xsprintf(path, "/proc/self/fd/%i", what); wd = inotify_add_watch(fd, path, mask); if (wd < 0) return -errno; return wd; } int inotify_add_watch_and_warn(int fd, const char *pathname, uint32_t mask) { int wd; wd = inotify_add_watch(fd, pathname, mask); if (wd < 0) { if (errno == ENOSPC) return log_error_errno(errno, "Failed to add a watch for %s: inotify watch limit reached", pathname); return log_error_errno(errno, "Failed to add a watch for %s: %m", pathname); } return wd; } static bool unsafe_transition(const struct stat *a, const struct stat *b) { /* Returns true if the transition from a to b is safe, i.e. that we never transition from unprivileged to * privileged files or directories. Why bother? So that unprivileged code can't symlink to privileged files * making us believe we read something safe even though it isn't safe in the specific context we open it in. */ if (a->st_uid == 0) /* Transitioning from privileged to unprivileged is always fine */ return false; return a->st_uid != b->st_uid; /* Otherwise we need to stay within the same UID */ } static int log_unsafe_transition(int a, int b, const char *path, unsigned flags) { _cleanup_free_ char *n1 = NULL, *n2 = NULL; if (!FLAGS_SET(flags, CHASE_WARN)) return -ENOLINK; (void) fd_get_path(a, &n1); (void) fd_get_path(b, &n2); return log_warning_errno(SYNTHETIC_ERRNO(ENOLINK), "Detected unsafe path transition %s %s %s during canonicalization of %s.", strna(n1), special_glyph(SPECIAL_GLYPH_ARROW), strna(n2), path); } static int log_autofs_mount_point(int fd, const char *path, unsigned flags) { _cleanup_free_ char *n1 = NULL; if (!FLAGS_SET(flags, CHASE_WARN)) return -EREMOTE; (void) fd_get_path(fd, &n1); return log_warning_errno(SYNTHETIC_ERRNO(EREMOTE), "Detected autofs mount point %s during canonicalization of %s.", strna(n1), path); } int chase_symlinks(const char *path, const char *original_root, unsigned flags, char **ret_path, int *ret_fd) { _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL; _cleanup_close_ int fd = -1; unsigned max_follow = CHASE_SYMLINKS_MAX; /* how many symlinks to follow before giving up and returning ELOOP */ struct stat previous_stat; bool exists = true; char *todo; int r; assert(path); /* Either the file may be missing, or we return an fd to the final object, but both make no sense */ if ((flags & CHASE_NONEXISTENT) && ret_fd) return -EINVAL; if ((flags & CHASE_STEP) && ret_fd) return -EINVAL; if (isempty(path)) return -EINVAL; /* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following * symlinks relative to a root directory, instead of the root of the host. * * Note that "root" primarily matters if we encounter an absolute symlink. It is also used when following * relative symlinks to ensure they cannot be used to "escape" the root directory. The path parameter passed is * assumed to be already prefixed by it, except if the CHASE_PREFIX_ROOT flag is set, in which case it is first * prefixed accordingly. * * Algorithmically this operates on two path buffers: "done" are the components of the path we already * processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to * process. On each iteration, we move one component from "todo" to "done", processing it's special meaning * each time. The "todo" path always starts with at least one slash, the "done" path always ends in no * slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races * to a minimum. * * Suggested usage: whenever you want to canonicalize a path, use this function. Pass the absolute path you got * as-is: fully qualified and relative to your host's root. Optionally, specify the root parameter to tell this * function what to do when encountering a symlink with an absolute path as directory: prefix it by the * specified path. * * There are five ways to invoke this function: * * 1. Without CHASE_STEP or ret_fd: in this case the path is resolved and the normalized path is * returned in `ret_path`. The return value is < 0 on error. If CHASE_NONEXISTENT is also set, 0 * is returned if the file doesn't exist, > 0 otherwise. If CHASE_NONEXISTENT is not set, >= 0 is * returned if the destination was found, -ENOENT if it wasn't. * * 2. With ret_fd: in this case the destination is opened after chasing it as O_PATH and this file * descriptor is returned as return value. This is useful to open files relative to some root * directory. Note that the returned O_PATH file descriptors must be converted into a regular one (using * fd_reopen() or such) before it can be used for reading/writing. ret_fd may not be combined with * CHASE_NONEXISTENT. * * 3. With CHASE_STEP: in this case only a single step of the normalization is executed, i.e. only the first * symlink or ".." component of the path is resolved, and the resulting path is returned. This is useful if * a caller wants to trace the path through the file system verbosely. Returns < 0 on error, > 0 if the * path is fully normalized, and == 0 for each normalization step. This may be combined with * CHASE_NONEXISTENT, in which case 1 is returned when a component is not found. * * 4. With CHASE_SAFE: in this case the path must not contain unsafe transitions, i.e. transitions from * unprivileged to privileged files or directories. In such cases the return value is -ENOLINK. If * CHASE_WARN is also set, a warning describing the unsafe transition is emitted. * * 5. With CHASE_NO_AUTOFS: in this case if an autofs mount point is encountered, path normalization * is aborted and -EREMOTE is returned. If CHASE_WARN is also set, a warning showing the path of * the mount point is emitted. */ /* A root directory of "/" or "" is identical to none */ if (empty_or_root(original_root)) original_root = NULL; if (!original_root && !ret_path && !(flags & (CHASE_NONEXISTENT|CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_STEP)) && ret_fd) { /* Shortcut the ret_fd case if the caller isn't interested in the actual path and has no root set * and doesn't care about any of the other special features we provide either. */ r = open(path, O_PATH|O_CLOEXEC|((flags & CHASE_NOFOLLOW) ? O_NOFOLLOW : 0)); if (r < 0) return -errno; *ret_fd = r; return 0; } if (original_root) { r = path_make_absolute_cwd(original_root, &root); if (r < 0) return r; /* Simplify the root directory, so that it has no duplicate slashes and nothing at the * end. While we won't resolve the root path we still simplify it. Note that dropping the * trailing slash should not change behaviour, since when opening it we specify O_DIRECTORY * anyway. Moreover at the end of this function after processing everything we'll always turn * the empty string back to "/". */ delete_trailing_chars(root, "/"); path_simplify(root, true); if (flags & CHASE_PREFIX_ROOT) { /* We don't support relative paths in combination with a root directory */ if (!path_is_absolute(path)) return -EINVAL; path = prefix_roota(root, path); } } r = path_make_absolute_cwd(path, &buffer); if (r < 0) return r; fd = open(root ?: "/", O_CLOEXEC|O_DIRECTORY|O_PATH); if (fd < 0) return -errno; if (flags & CHASE_SAFE) { if (fstat(fd, &previous_stat) < 0) return -errno; } if (root) { _cleanup_free_ char *absolute = NULL; const char *e; /* If we are operating on a root directory, let's take the root directory as it is. */ e = path_startswith(buffer, root); if (!e) return log_full_errno(flags & CHASE_WARN ? LOG_WARNING : LOG_DEBUG, SYNTHETIC_ERRNO(ECHRNG), "Specified path '%s' is outside of specified root directory '%s', refusing to resolve.", path, root); done = strdup(root); if (!done) return -ENOMEM; /* Make sure "todo" starts with a slash */ absolute = strjoin("/", e); if (!absolute) return -ENOMEM; free_and_replace(buffer, absolute); } todo = buffer; for (;;) { _cleanup_free_ char *first = NULL; _cleanup_close_ int child = -1; struct stat st; size_t n, m; /* Determine length of first component in the path */ n = strspn(todo, "/"); /* The slashes */ if (n > 1) { /* If we are looking at more than a single slash then skip all but one, so that when * we are done with everything we have a normalized path with only single slashes * separating the path components. */ todo += n - 1; n = 1; } m = n + strcspn(todo + n, "/"); /* The entire length of the component */ /* Extract the first component. */ first = strndup(todo, m); if (!first) return -ENOMEM; todo += m; /* Empty? Then we reached the end. */ if (isempty(first)) break; /* Just a single slash? Then we reached the end. */ if (path_equal(first, "/")) { /* Preserve the trailing slash */ if (flags & CHASE_TRAIL_SLASH) if (!strextend(&done, "/")) return -ENOMEM; break; } /* Just a dot? Then let's eat this up. */ if (path_equal(first, "/.")) continue; /* Two dots? Then chop off the last bit of what we already found out. */ if (path_equal(first, "/..")) { _cleanup_free_ char *parent = NULL; _cleanup_close_ int fd_parent = -1; /* If we already are at the top, then going up will not change anything. This is in-line with * how the kernel handles this. */ if (empty_or_root(done)) continue; parent = dirname_malloc(done); if (!parent) return -ENOMEM; /* Don't allow this to leave the root dir. */ if (root && path_startswith(done, root) && !path_startswith(parent, root)) continue; free_and_replace(done, parent); if (flags & CHASE_STEP) goto chased_one; fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH); if (fd_parent < 0) return -errno; if (flags & CHASE_SAFE) { if (fstat(fd_parent, &st) < 0) return -errno; if (unsafe_transition(&previous_stat, &st)) return log_unsafe_transition(fd, fd_parent, path, flags); previous_stat = st; } safe_close(fd); fd = TAKE_FD(fd_parent); continue; } /* Otherwise let's see what this is. */ child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH); if (child < 0) { if (errno == ENOENT && (flags & CHASE_NONEXISTENT) && (isempty(todo) || path_is_normalized(todo))) { /* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return * what we got so far. But don't allow this if the remaining path contains "../ or "./" * or something else weird. */ /* If done is "/", as first also contains slash at the head, then remove this redundant slash. */ if (streq_ptr(done, "/")) *done = '\0'; if (!strextend(&done, first, todo)) return -ENOMEM; exists = false; break; } return -errno; } if (fstat(child, &st) < 0) return -errno; if ((flags & CHASE_SAFE) && unsafe_transition(&previous_stat, &st)) return log_unsafe_transition(fd, child, path, flags); previous_stat = st; if ((flags & CHASE_NO_AUTOFS) && fd_is_fs_type(child, AUTOFS_SUPER_MAGIC) > 0) return log_autofs_mount_point(child, path, flags); if (S_ISLNK(st.st_mode) && !((flags & CHASE_NOFOLLOW) && isempty(todo))) { char *joined; _cleanup_free_ char *destination = NULL; /* This is a symlink, in this case read the destination. But let's make sure we don't follow * symlinks without bounds. */ if (--max_follow <= 0) return -ELOOP; r = readlinkat_malloc(fd, first + n, &destination); if (r < 0) return r; if (isempty(destination)) return -EINVAL; if (path_is_absolute(destination)) { /* An absolute destination. Start the loop from the beginning, but use the root * directory as base. */ safe_close(fd); fd = open(root ?: "/", O_CLOEXEC|O_DIRECTORY|O_PATH); if (fd < 0) return -errno; if (flags & CHASE_SAFE) { if (fstat(fd, &st) < 0) return -errno; if (unsafe_transition(&previous_stat, &st)) return log_unsafe_transition(child, fd, path, flags); previous_stat = st; } free(done); /* Note that we do not revalidate the root, we take it as is. */ if (isempty(root)) done = NULL; else { done = strdup(root); if (!done) return -ENOMEM; } /* Prefix what's left to do with what we just read, and start the loop again, but * remain in the current directory. */ joined = path_join(destination, todo); } else joined = path_join("/", destination, todo); if (!joined) return -ENOMEM; free(buffer); todo = buffer = joined; if (flags & CHASE_STEP) goto chased_one; continue; } /* If this is not a symlink, then let's just add the name we read to what we already verified. */ if (!done) done = TAKE_PTR(first); else { /* If done is "/", as first also contains slash at the head, then remove this redundant slash. */ if (streq(done, "/")) *done = '\0'; if (!strextend(&done, first)) return -ENOMEM; } /* And iterate again, but go one directory further down. */ safe_close(fd); fd = TAKE_FD(child); } if (!done) { /* Special case, turn the empty string into "/", to indicate the root directory. */ done = strdup("/"); if (!done) return -ENOMEM; } if (ret_path) *ret_path = TAKE_PTR(done); if (ret_fd) { /* Return the O_PATH fd we currently are looking to the caller. It can translate it to a * proper fd by opening /proc/self/fd/xyz. */ assert(fd >= 0); *ret_fd = TAKE_FD(fd); } if (flags & CHASE_STEP) return 1; return exists; chased_one: if (ret_path) { char *c; c = strjoin(strempty(done), todo); if (!c) return -ENOMEM; *ret_path = c; } return 0; } int chase_symlinks_and_open( const char *path, const char *root, unsigned chase_flags, int open_flags, char **ret_path) { _cleanup_close_ int path_fd = -1; _cleanup_free_ char *p = NULL; int r; if (chase_flags & CHASE_NONEXISTENT) return -EINVAL; if (empty_or_root(root) && !ret_path && (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE)) == 0) { /* Shortcut this call if none of the special features of this call are requested */ r = open(path, open_flags); if (r < 0) return -errno; return r; } r = chase_symlinks(path, root, chase_flags, ret_path ? &p : NULL, &path_fd); if (r < 0) return r; assert(path_fd >= 0); r = fd_reopen(path_fd, open_flags); if (r < 0) return r; if (ret_path) *ret_path = TAKE_PTR(p); return r; } int chase_symlinks_and_opendir( const char *path, const char *root, unsigned chase_flags, char **ret_path, DIR **ret_dir) { char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; _cleanup_close_ int path_fd = -1; _cleanup_free_ char *p = NULL; DIR *d; int r; if (!ret_dir) return -EINVAL; if (chase_flags & CHASE_NONEXISTENT) return -EINVAL; if (empty_or_root(root) && !ret_path && (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE)) == 0) { /* Shortcut this call if none of the special features of this call are requested */ d = opendir(path); if (!d) return -errno; *ret_dir = d; return 0; } r = chase_symlinks(path, root, chase_flags, ret_path ? &p : NULL, &path_fd); if (r < 0) return r; assert(path_fd >= 0); xsprintf(procfs_path, "/proc/self/fd/%i", path_fd); d = opendir(procfs_path); if (!d) return -errno; if (ret_path) *ret_path = TAKE_PTR(p); *ret_dir = d; return 0; } int chase_symlinks_and_stat( const char *path, const char *root, unsigned chase_flags, char **ret_path, struct stat *ret_stat, int *ret_fd) { _cleanup_close_ int path_fd = -1; _cleanup_free_ char *p = NULL; int r; assert(path); assert(ret_stat); if (chase_flags & CHASE_NONEXISTENT) return -EINVAL; if (empty_or_root(root) && !ret_path && (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE)) == 0) { /* Shortcut this call if none of the special features of this call are requested */ if (stat(path, ret_stat) < 0) return -errno; return 1; } r = chase_symlinks(path, root, chase_flags, ret_path ? &p : NULL, &path_fd); if (r < 0) return r; assert(path_fd >= 0); if (fstat(path_fd, ret_stat) < 0) return -errno; if (ret_path) *ret_path = TAKE_PTR(p); if (ret_fd) *ret_fd = TAKE_FD(path_fd); return 1; } int access_fd(int fd, int mode) { char p[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(fd) + 1]; /* Like access() but operates on an already open fd */ xsprintf(p, "/proc/self/fd/%i", fd); if (access(p, mode) < 0) { if (errno != ENOENT) return -errno; /* ENOENT can mean two things: that the fd does not exist or that /proc is not mounted. Let's * make things debuggable and distinguish the two. */ if (proc_mounted() == 0) return -ENOSYS; /* /proc is not available or not set up properly, we're most likely in some chroot * environment. */ return -EBADF; /* The directory exists, hence it's the fd that doesn't. */ } return 0; } void unlink_tempfilep(char (*p)[]) { /* If the file is created with mkstemp(), it will (almost always) * change the suffix. Treat this as a sign that the file was * successfully created. We ignore both the rare case where the * original suffix is used and unlink failures. */ if (!endswith(*p, ".XXXXXX")) (void) unlink_noerrno(*p); } int unlinkat_deallocate(int fd, const char *name, UnlinkDeallocateFlags flags) { _cleanup_close_ int truncate_fd = -1; struct stat st; off_t l, bs; assert((flags & ~(UNLINK_REMOVEDIR|UNLINK_ERASE)) == 0); /* Operates like unlinkat() but also deallocates the file contents if it is a regular file and there's no other * link to it. This is useful to ensure that other processes that might have the file open for reading won't be * able to keep the data pinned on disk forever. This call is particular useful whenever we execute clean-up * jobs ("vacuuming"), where we want to make sure the data is really gone and the disk space released and * returned to the free pool. * * Deallocation is preferably done by FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE (👊) if supported, which means * the file won't change size. That's a good thing since we shouldn't needlessly trigger SIGBUS in other * programs that have mmap()ed the file. (The assumption here is that changing file contents to all zeroes * underneath those programs is the better choice than simply triggering SIGBUS in them which truncation does.) * However if hole punching is not implemented in the kernel or file system we'll fall back to normal file * truncation (đŸ”Ē), as our goal of deallocating the data space trumps our goal of being nice to readers (💐). * * Note that we attempt deallocation, but failure to succeed with that is not considered fatal, as long as the * primary job – to delete the file – is accomplished. */ if (!FLAGS_SET(flags, UNLINK_REMOVEDIR)) { truncate_fd = openat(fd, name, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_NONBLOCK); if (truncate_fd < 0) { /* If this failed because the file doesn't exist propagate the error right-away. Also, * AT_REMOVEDIR wasn't set, and we tried to open the file for writing, which means EISDIR is * returned when this is a directory but we are not supposed to delete those, hence propagate * the error right-away too. */ if (IN_SET(errno, ENOENT, EISDIR)) return -errno; if (errno != ELOOP) /* don't complain if this is a symlink */ log_debug_errno(errno, "Failed to open file '%s' for deallocation, ignoring: %m", name); } } if (unlinkat(fd, name, FLAGS_SET(flags, UNLINK_REMOVEDIR) ? AT_REMOVEDIR : 0) < 0) return -errno; if (truncate_fd < 0) /* Don't have a file handle, can't do more ☚ī¸ */ return 0; if (fstat(truncate_fd, &st) < 0) { log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring: %m", name); return 0; } if (!S_ISREG(st.st_mode)) return 0; if (FLAGS_SET(flags, UNLINK_ERASE) && st.st_size > 0 && st.st_nlink == 0) { uint64_t left = st.st_size; char buffer[64 * 1024]; /* If erasing is requested, let's overwrite the file with random data once before deleting * it. This isn't going to give you shred(1) semantics, but hopefully should be good enough * for stuff backed by tmpfs at least. * * Note that we only erase like this if the link count of the file is zero. If it is higher it * is still linked by someone else and we'll leave it to them to remove it securely * eventually! */ random_bytes(buffer, sizeof(buffer)); while (left > 0) { ssize_t n; n = write(truncate_fd, buffer, MIN(sizeof(buffer), left)); if (n < 0) { log_debug_errno(errno, "Failed to erase data in file '%s', ignoring.", name); break; } assert(left >= (size_t) n); left -= n; } /* Let's refresh metadata */ if (fstat(truncate_fd, &st) < 0) { log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring: %m", name); return 0; } } /* Don't dallocate if there's nothing to deallocate or if the file is linked elsewhere */ if (st.st_blocks == 0 || st.st_nlink > 0) return 0; /* If this is a regular file, it actually took up space on disk and there are no other links it's time to * punch-hole/truncate this to release the disk space. */ bs = MAX(st.st_blksize, 512); l = DIV_ROUND_UP(st.st_size, bs) * bs; /* Round up to next block size */ if (fallocate(truncate_fd, FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE, 0, l) >= 0) return 0; /* Successfully punched a hole! 😊 */ /* Fall back to truncation */ if (ftruncate(truncate_fd, 0) < 0) { log_debug_errno(errno, "Failed to truncate file to 0, ignoring: %m"); return 0; } return 0; } int fsync_directory_of_file(int fd) { _cleanup_free_ char *path = NULL; _cleanup_close_ int dfd = -1; struct stat st; int r; assert(fd >= 0); /* We only reasonably can do this for regular files and directories, hence check for that */ if (fstat(fd, &st) < 0) return -errno; if (S_ISREG(st.st_mode)) { r = fd_get_path(fd, &path); if (r < 0) { log_debug_errno(r, "Failed to query /proc/self/fd/%d%s: %m", fd, r == -ENOSYS ? ", ignoring" : ""); if (r == -ENOSYS) /* If /proc is not available, we're most likely running in some * chroot environment, and syncing the directory is not very * important in that case. Let's just silently do nothing. */ return 0; return r; } if (!path_is_absolute(path)) return -EINVAL; dfd = open_parent(path, O_CLOEXEC|O_NOFOLLOW, 0); if (dfd < 0) return dfd; } else if (S_ISDIR(st.st_mode)) { dfd = openat(fd, "..", O_RDONLY|O_DIRECTORY|O_CLOEXEC, 0); if (dfd < 0) return -errno; } else return -ENOTTY; if (fsync(dfd) < 0) return -errno; return 0; } int fsync_full(int fd) { int r, q; /* Sync both the file and the directory */ r = fsync(fd) < 0 ? -errno : 0; q = fsync_directory_of_file(fd); if (r < 0) /* Return earlier error */ return r; if (q == -ENOTTY) /* Ignore if the 'fd' refers to a block device or so which doesn't really have a * parent dir */ return 0; return q; } int fsync_path_at(int at_fd, const char *path) { _cleanup_close_ int opened_fd = -1; int fd; if (isempty(path)) { if (at_fd == AT_FDCWD) { opened_fd = open(".", O_RDONLY|O_DIRECTORY|O_CLOEXEC); if (opened_fd < 0) return -errno; fd = opened_fd; } else fd = at_fd; } else { opened_fd = openat(at_fd, path, O_RDONLY|O_CLOEXEC|O_NONBLOCK); if (opened_fd < 0) return -errno; fd = opened_fd; } if (fsync(fd) < 0) return -errno; return 0; } int syncfs_path(int atfd, const char *path) { _cleanup_close_ int fd = -1; assert(path); fd = openat(atfd, path, O_CLOEXEC|O_RDONLY|O_NONBLOCK); if (fd < 0) return -errno; if (syncfs(fd) < 0) return -errno; return 0; } int open_parent(const char *path, int flags, mode_t mode) { _cleanup_free_ char *parent = NULL; int fd, r; r = path_extract_directory(path, &parent); if (r < 0) return r; /* Let's insist on O_DIRECTORY since the parent of a file or directory is a directory. Except if we open an * O_TMPFILE file, because in that case we are actually create a regular file below the parent directory. */ if (FLAGS_SET(flags, O_PATH)) flags |= O_DIRECTORY; else if (!FLAGS_SET(flags, O_TMPFILE)) flags |= O_DIRECTORY|O_RDONLY; fd = open(parent, flags, mode); if (fd < 0) return -errno; return fd; } static int blockdev_is_encrypted(const char *sysfs_path, unsigned depth_left) { _cleanup_free_ char *p = NULL, *uuids = NULL; _cleanup_closedir_ DIR *d = NULL; int r, found_encrypted = false; assert(sysfs_path); if (depth_left == 0) return -EINVAL; p = path_join(sysfs_path, "dm/uuid"); if (!p) return -ENOMEM; r = read_one_line_file(p, &uuids); if (r != -ENOENT) { if (r < 0) return r; /* The DM device's uuid attribute is prefixed with "CRYPT-" if this is a dm-crypt device. */ if (startswith(uuids, "CRYPT-")) return true; } /* Not a dm-crypt device itself. But maybe it is on top of one? Follow the links in the "slaves/" * subdir. */ p = mfree(p); p = path_join(sysfs_path, "slaves"); if (!p) return -ENOMEM; d = opendir(p); if (!d) { if (errno == ENOENT) /* Doesn't have underlying devices */ return false; return -errno; } for (;;) { _cleanup_free_ char *q = NULL; struct dirent *de; errno = 0; de = readdir_no_dot(d); if (!de) { if (errno != 0) return -errno; break; /* No more underlying devices */ } q = path_join(p, de->d_name); if (!q) return -ENOMEM; r = blockdev_is_encrypted(q, depth_left - 1); if (r < 0) return r; if (r == 0) /* we found one that is not encrypted? then propagate that immediately */ return false; found_encrypted = true; } return found_encrypted; } int path_is_encrypted(const char *path) { char p[SYS_BLOCK_PATH_MAX(NULL)]; dev_t devt; int r; r = get_block_device(path, &devt); if (r < 0) return r; if (r == 0) /* doesn't have a block device */ return false; xsprintf_sys_block_path(p, NULL, devt); return blockdev_is_encrypted(p, 10 /* safety net: maximum recursion depth */); } int conservative_renameat( int olddirfd, const char *oldpath, int newdirfd, const char *newpath) { _cleanup_close_ int old_fd = -1, new_fd = -1; struct stat old_stat, new_stat; /* Renames the old path to thew new path, much like renameat() — except if both are regular files and * have the exact same contents and basic file attributes already. In that case remove the new file * instead. This call is useful for reducing inotify wakeups on files that are updated but don't * actually change. This function is written in a style that we rather rename too often than suppress * too much. i.e. whenever we are in doubt we rather rename than fail. After all reducing inotify * events is an optimization only, not more. */ old_fd = openat(olddirfd, oldpath, O_CLOEXEC|O_RDONLY|O_NOCTTY|O_NOFOLLOW); if (old_fd < 0) goto do_rename; new_fd = openat(newdirfd, newpath, O_CLOEXEC|O_RDONLY|O_NOCTTY|O_NOFOLLOW); if (new_fd < 0) goto do_rename; if (fstat(old_fd, &old_stat) < 0) goto do_rename; if (!S_ISREG(old_stat.st_mode)) goto do_rename; if (fstat(new_fd, &new_stat) < 0) goto do_rename; if (new_stat.st_ino == old_stat.st_ino && new_stat.st_dev == old_stat.st_dev) goto is_same; if (old_stat.st_mode != new_stat.st_mode || old_stat.st_size != new_stat.st_size || old_stat.st_uid != new_stat.st_uid || old_stat.st_gid != new_stat.st_gid) goto do_rename; for (;;) { uint8_t buf1[16*1024]; uint8_t buf2[sizeof(buf1)]; ssize_t l1, l2; l1 = read(old_fd, buf1, sizeof(buf1)); if (l1 < 0) goto do_rename; if (l1 == sizeof(buf1)) /* Read the full block, hence read a full block in the other file too */ l2 = read(new_fd, buf2, l1); else { assert((size_t) l1 < sizeof(buf1)); /* Short read. This hence was the last block in the first file, and then came * EOF. Read one byte more in the second file, so that we can verify we hit EOF there * too. */ assert((size_t) (l1 + 1) <= sizeof(buf2)); l2 = read(new_fd, buf2, l1 + 1); } if (l2 != l1) goto do_rename; if (memcmp(buf1, buf2, l1) != 0) goto do_rename; if ((size_t) l1 < sizeof(buf1)) /* We hit EOF on the first file, and the second file too, hence exit * now. */ break; } is_same: /* Everything matches? Then don't rename, instead remove the source file, and leave the existing * destination in place */ if (unlinkat(olddirfd, oldpath, 0) < 0) goto do_rename; return 0; do_rename: if (renameat(olddirfd, oldpath, newdirfd, newpath) < 0) return -errno; return 1; }