diff options
Diffstat (limited to 'src/libsystemd-basic/src/fs-util.c')
-rw-r--r-- | src/libsystemd-basic/src/fs-util.c | 782 |
1 files changed, 782 insertions, 0 deletions
diff --git a/src/libsystemd-basic/src/fs-util.c b/src/libsystemd-basic/src/fs-util.c new file mode 100644 index 0000000000..070be9c568 --- /dev/null +++ b/src/libsystemd-basic/src/fs-util.c @@ -0,0 +1,782 @@ +/*** + This file is part of systemd. + + Copyright 2010 Lennart Poettering + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. +***/ + +#include <dirent.h> +#include <errno.h> +#include <stddef.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/stat.h> +#include <time.h> +#include <unistd.h> + +#include "systemd-basic/alloc-util.h" +#include "systemd-basic/dirent-util.h" +#include "systemd-basic/fd-util.h" +#include "systemd-basic/fileio.h" +#include "systemd-basic/fs-util.h" +#include "systemd-basic/log.h" +#include "systemd-basic/macro.h" +#include "systemd-basic/missing.h" +#include "systemd-basic/mkdir.h" +#include "systemd-basic/parse-util.h" +#include "systemd-basic/path-util.h" +#include "systemd-basic/stat-util.h" +#include "systemd-basic/stdio-util.h" +#include "systemd-basic/string-util.h" +#include "systemd-basic/strv.h" +#include "systemd-basic/time-util.h" +#include "systemd-basic/user-util.h" +#include "systemd-basic/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) { + struct stat buf; + int ret; + + ret = renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE); + if (ret >= 0) + return 0; + + /* renameat2() exists since Linux 3.15, btrfs added support for it later. + * If it is not implemented, fallback to another method. */ + if (!IN_SET(errno, EINVAL, ENOSYS)) + return -errno; + + /* The link()/unlink() fallback does not work on directories. But + * renameat() without RENAME_NOREPLACE gives the same semantics on + * directories, except when newpath is an *empty* directory. This is + * good enough. */ + ret = fstatat(olddirfd, oldpath, &buf, AT_SYMLINK_NOFOLLOW); + if (ret >= 0 && S_ISDIR(buf.st_mode)) { + ret = renameat(olddirfd, oldpath, newdirfd, newpath); + return ret >= 0 ? 0 : -errno; + } + + /* If it is not a directory, use the link()/unlink() fallback. */ + ret = linkat(olddirfd, oldpath, newdirfd, newpath, 0); + if (ret < 0) + return -errno; + + ret = unlinkat(olddirfd, oldpath, 0); + if (ret < 0) { + /* backup errno before the following unlinkat() alters it */ + ret = errno; + (void) unlinkat(newdirfd, newpath, 0); + errno = ret; + return -errno; + } + + return 0; +} + +int readlinkat_malloc(int fd, const char *p, char **ret) { + size_t l = 100; + int r; + + assert(p); + assert(ret); + + for (;;) { + char *c; + ssize_t n; + + c = new(char, l); + if (!c) + return -ENOMEM; + + n = readlinkat(fd, p, c, l-1); + if (n < 0) { + r = -errno; + free(c); + return r; + } + + if ((size_t) n < l-1) { + c[n] = 0; + *ret = c; + return 0; + } + + free(c); + 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 readlink_and_canonicalize(const char *p, char **r) { + char *t, *s; + int j; + + assert(p); + assert(r); + + j = readlink_and_make_absolute(p, &t); + if (j < 0) + return j; + + s = canonicalize_file_name(t); + if (s) { + free(t); + *r = s; + } else + *r = t; + + path_kill_slashes(*r); + + return 0; +} + +int readlink_and_make_absolute_root(const char *root, const char *path, char **ret) { + _cleanup_free_ char *target = NULL, *t = NULL; + const char *full; + int r; + + full = prefix_roota(root, path); + r = readlink_malloc(full, &target); + if (r < 0) + return r; + + t = file_in_same_dir(path, target); + if (!t) + return -ENOMEM; + + *ret = t; + t = NULL; + + return 0; +} + +int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) { + assert(path); + + /* Under the assumption that we are running privileged we + * first change the access mode and only then hand out + * ownership to avoid a window where access is too open. */ + + if (mode != MODE_INVALID) + if (chmod(path, mode) < 0) + return -errno; + + if (uid != UID_INVALID || gid != GID_INVALID) + if (chown(path, uid, gid) < 0) + return -errno; + + return 0; +} + +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 fd_warn_permissions(const char *path, int fd) { + struct stat st; + + if (fstat(fd, &st) < 0) + return -errno; + + 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() == 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 touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) { + _cleanup_close_ int fd; + int r; + + assert(path); + + if (parents) + mkdir_parents(path, 0755); + + fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY, + (mode == 0 || mode == MODE_INVALID) ? 0644 : mode); + if (fd < 0) + return -errno; + + if (mode != MODE_INVALID) { + r = fchmod(fd, mode); + if (r < 0) + return -errno; + } + + if (uid != UID_INVALID || gid != GID_INVALID) { + r = fchown(fd, uid, gid); + if (r < 0) + return -errno; + } + + if (stamp != USEC_INFINITY) { + struct timespec ts[2]; + + timespec_store(&ts[0], stamp); + ts[1] = ts[0]; + r = futimens(fd, ts); + } else + r = futimens(fd, NULL); + if (r < 0) + return -errno; + + return 0; +} + +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) { + _cleanup_free_ char *p = NULL; + int r; + + assert(from); + assert(to); + + if (symlink(from, to) < 0) { + if (errno != EEXIST) + return -errno; + + r = readlink_malloc(to, &p); + if (r < 0) + return r; + + if (!streq(p, from)) + return -EINVAL; + } + + 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 get_files_in_directory(const char *path, char ***list) { + _cleanup_closedir_ DIR *d = NULL; + 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; + + for (;;) { + struct dirent *de; + + errno = 0; + de = readdir(d); + if (!de && errno > 0) + return -errno; + if (!de) + break; + + 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 = l; + l = NULL; /* avoid freeing */ + } + + 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_safe(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 inotify_add_watch_fd(int fd, int what, uint32_t mask) { + char path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; + int r; + + /* 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); + + r = inotify_add_watch(fd, path, mask); + if (r < 0) + return -errno; + + return r; +} + +int chase_symlinks(const char *path, const char *_root, char **ret) { + _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL; + _cleanup_close_ int fd = -1; + unsigned max_follow = 32; /* how many symlinks to follow before giving up and returning ELOOP */ + char *todo; + int r; + + assert(path); + + /* 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" matters only if we encounter an absolute symlink, it's unused otherwise. Most importantly + * this means the path parameter passed in is not prefixed by it. + * + * 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 + * at a minimum. */ + + r = path_make_absolute_cwd(path, &buffer); + if (r < 0) + return r; + + if (_root) { + r = path_make_absolute_cwd(_root, &root); + if (r < 0) + return r; + } + + fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH); + if (fd < 0) + return -errno; + + 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 */ + 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; + + /* Just a single slash? Then we reached the end. */ + if (isempty(first) || path_equal(first, "/")) + 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; + int fd_parent = -1; + + if (isempty(done) || path_equal(done, "/")) + return -EINVAL; + + 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)) + return -EINVAL; + + free_and_replace(done, parent); + + fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH); + if (fd_parent < 0) + return -errno; + + safe_close(fd); + 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) + return -errno; + + if (fstat(child, &st) < 0) + return -errno; + + if (S_ISLNK(st.st_mode)) { + _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_NOFOLLOW|O_PATH); + if (fd < 0) + return -errno; + + free_and_replace(buffer, destination); + + todo = buffer; + 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; + } + + } else { + char *joined; + + /* A relative destination. If so, this is what we'll prefix what's left to do with what + * we just read, and start the loop again, but remain in the current directory. */ + + joined = strjoin("/", destination, todo, NULL); + if (!joined) + return -ENOMEM; + + free(buffer); + todo = buffer = joined; + } + + continue; + } + + /* If this is not a symlink, then let's just add the name we read to what we already verified. */ + if (!done) { + done = first; + first = NULL; + } else { + if (!strextend(&done, first, NULL)) + return -ENOMEM; + } + + /* And iterate again, but go one directory further down. */ + safe_close(fd); + fd = child; + child = -1; + } + + if (!done) { + /* Special case, turn the empty string into "/", to indicate the root directory. */ + done = strdup("/"); + if (!done) + return -ENOMEM; + } + + *ret = done; + done = NULL; + + return 0; +} |