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git.ipfire.org Git - thirdparty/systemd.git/blob - src/basic/fs-util.c
b30cec4f925154ae96d7142441b12d1a5887226c
2 This file is part of systemd.
4 Copyright 2010 Lennart Poettering
6 systemd is free software; you can redistribute it and/or modify it
7 under the terms of the GNU Lesser General Public License as published by
8 the Free Software Foundation; either version 2.1 of the License, or
9 (at your option) any later version.
11 systemd is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public License
17 along with systemd; If not, see <http://www.gnu.org/licenses/>.
30 #include "alloc-util.h"
31 #include "dirent-util.h"
39 #include "parse-util.h"
40 #include "path-util.h"
41 #include "stat-util.h"
42 #include "stdio-util.h"
43 #include "string-util.h"
45 #include "time-util.h"
46 #include "user-util.h"
49 int unlink_noerrno ( const char * path
) {
60 int rmdir_parents ( const char * path
, const char * stop
) {
69 /* Skip trailing slashes */
70 while ( l
> 0 && path
[ l
- 1 ] == '/' )
76 /* Skip last component */
77 while ( l
> 0 && path
[ l
- 1 ] != '/' )
80 /* Skip trailing slashes */
81 while ( l
> 0 && path
[ l
- 1 ] == '/' )
91 if ( path_startswith ( stop
, t
)) {
108 int rename_noreplace ( int olddirfd
, const char * oldpath
, int newdirfd
, const char * newpath
) {
112 ret
= renameat2 ( olddirfd
, oldpath
, newdirfd
, newpath
, RENAME_NOREPLACE
);
116 /* renameat2() exists since Linux 3.15, btrfs added support for it later.
117 * If it is not implemented, fallback to another method. */
118 if (! IN_SET ( errno
, EINVAL
, ENOSYS
))
121 /* The link()/unlink() fallback does not work on directories. But
122 * renameat() without RENAME_NOREPLACE gives the same semantics on
123 * directories, except when newpath is an *empty* directory. This is
125 ret
= fstatat ( olddirfd
, oldpath
, & buf
, AT_SYMLINK_NOFOLLOW
);
126 if ( ret
>= 0 && S_ISDIR ( buf
. st_mode
)) {
127 ret
= renameat ( olddirfd
, oldpath
, newdirfd
, newpath
);
128 return ret
>= 0 ? 0 : - errno
;
131 /* If it is not a directory, use the link()/unlink() fallback. */
132 ret
= linkat ( olddirfd
, oldpath
, newdirfd
, newpath
, 0 );
136 ret
= unlinkat ( olddirfd
, oldpath
, 0 );
138 /* backup errno before the following unlinkat() alters it */
140 ( void ) unlinkat ( newdirfd
, newpath
, 0 );
148 int readlinkat_malloc ( int fd
, const char * p
, char ** ret
) {
163 n
= readlinkat ( fd
, p
, c
, l
- 1 );
170 if (( size_t ) n
< l
- 1 ) {
181 int readlink_malloc ( const char * p
, char ** ret
) {
182 return readlinkat_malloc ( AT_FDCWD
, p
, ret
);
185 int readlink_value ( const char * p
, char ** ret
) {
186 _cleanup_free_
char * link
= NULL
;
190 r
= readlink_malloc ( p
, & link
);
194 value
= basename ( link
);
198 value
= strdup ( value
);
207 int readlink_and_make_absolute ( const char * p
, char ** r
) {
208 _cleanup_free_
char * target
= NULL
;
215 j
= readlink_malloc ( p
, & target
);
219 k
= file_in_same_dir ( p
, target
);
227 int readlink_and_canonicalize ( const char * p
, const char * root
, char ** ret
) {
234 r
= readlink_and_make_absolute ( p
, & t
);
238 r
= chase_symlinks ( t
, root
, 0 , & s
);
240 /* If we can't follow up, then let's return the original string, slightly cleaned up. */
241 * ret
= path_kill_slashes ( t
);
250 int readlink_and_make_absolute_root ( const char * root
, const char * path
, char ** ret
) {
251 _cleanup_free_
char * target
= NULL
, * t
= NULL
;
255 full
= prefix_roota ( root
, path
);
256 r
= readlink_malloc ( full
, & target
);
260 t
= file_in_same_dir ( path
, target
);
270 int chmod_and_chown ( const char * path
, mode_t mode
, uid_t uid
, gid_t gid
) {
273 /* Under the assumption that we are running privileged we
274 * first change the access mode and only then hand out
275 * ownership to avoid a window where access is too open. */
277 if ( mode
!= MODE_INVALID
)
278 if ( chmod ( path
, mode
) < 0 )
281 if ( uid
!= UID_INVALID
|| gid
!= GID_INVALID
)
282 if ( chown ( path
, uid
, gid
) < 0 )
288 int fchmod_umask ( int fd
, mode_t m
) {
293 r
= fchmod ( fd
, m
& (~ u
)) < 0 ? - errno
: 0 ;
299 int fd_warn_permissions ( const char * path
, int fd
) {
302 if ( fstat ( fd
, & st
) < 0 )
305 if ( st
. st_mode
& 0111 )
306 log_warning ( "Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway." , path
);
308 if ( st
. st_mode
& 0002 )
309 log_warning ( "Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway." , path
);
311 if ( getpid () == 1 && ( st
. st_mode
& 0044 ) != 0044 )
312 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
);
317 int touch_file ( const char * path
, bool parents
, usec_t stamp
, uid_t uid
, gid_t gid
, mode_t mode
) {
318 _cleanup_close_
int fd
;
324 mkdir_parents ( path
, 0755 );
326 fd
= open ( path
, O_WRONLY
| O_CREAT
| O_CLOEXEC
| O_NOCTTY
,
327 ( mode
== 0 || mode
== MODE_INVALID
) ? 0644 : mode
);
331 if ( mode
!= MODE_INVALID
) {
332 r
= fchmod ( fd
, mode
);
337 if ( uid
!= UID_INVALID
|| gid
!= GID_INVALID
) {
338 r
= fchown ( fd
, uid
, gid
);
343 if ( stamp
!= USEC_INFINITY
) {
344 struct timespec ts
[ 2 ];
346 timespec_store (& ts
[ 0 ], stamp
);
348 r
= futimens ( fd
, ts
);
350 r
= futimens ( fd
, NULL
);
357 int touch ( const char * path
) {
358 return touch_file ( path
, false , USEC_INFINITY
, UID_INVALID
, GID_INVALID
, MODE_INVALID
);
361 int symlink_idempotent ( const char * from
, const char * to
) {
362 _cleanup_free_
char * p
= NULL
;
368 if ( symlink ( from
, to
) < 0 ) {
372 r
= readlink_malloc ( to
, & p
);
383 int symlink_atomic ( const char * from
, const char * to
) {
384 _cleanup_free_
char * t
= NULL
;
390 r
= tempfn_random ( to
, NULL
, & t
);
394 if ( symlink ( from
, t
) < 0 )
397 if ( rename ( t
, to
) < 0 ) {
405 int mknod_atomic ( const char * path
, mode_t mode
, dev_t dev
) {
406 _cleanup_free_
char * t
= NULL
;
411 r
= tempfn_random ( path
, NULL
, & t
);
415 if ( mknod ( t
, mode
, dev
) < 0 )
418 if ( rename ( t
, path
) < 0 ) {
426 int mkfifo_atomic ( const char * path
, mode_t mode
) {
427 _cleanup_free_
char * t
= NULL
;
432 r
= tempfn_random ( path
, NULL
, & t
);
436 if ( mkfifo ( t
, mode
) < 0 )
439 if ( rename ( t
, path
) < 0 ) {
447 int get_files_in_directory ( const char * path
, char *** list
) {
448 _cleanup_closedir_
DIR * d
= NULL
;
449 size_t bufsize
= 0 , n
= 0 ;
450 _cleanup_strv_free_
char ** l
= NULL
;
454 /* Returns all files in a directory in *list, and the number
455 * of files as return value. If list is NULL returns only the
467 if (! de
&& errno
> 0 )
472 dirent_ensure_type ( d
, de
);
474 if (! dirent_is_file ( de
))
478 /* one extra slot is needed for the terminating NULL */
479 if (! GREEDY_REALLOC ( l
, bufsize
, n
+ 2 ))
482 l
[ n
] = strdup ( de
-> d_name
);
493 l
= NULL
; /* avoid freeing */
499 static int getenv_tmp_dir ( const char ** ret_path
) {
505 /* We use the same order of environment variables python uses in tempfile.gettempdir():
506 * https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */
507 FOREACH_STRING ( n
, "TMPDIR" , "TEMP" , "TMP" ) {
510 e
= secure_getenv ( n
);
513 if (! path_is_absolute ( e
)) {
517 if (! path_is_safe ( e
)) {
534 /* Remember first error, to make this more debuggable */
546 static int tmp_dir_internal ( const char * def
, const char ** ret
) {
553 r
= getenv_tmp_dir (& e
);
559 k
= is_dir ( def
, true );
563 return r
< 0 ? r
: k
;
569 int var_tmp_dir ( const char ** ret
) {
571 /* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus
572 * even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is
573 * returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR,
574 * making it a variable that overrides all temporary file storage locations. */
576 return tmp_dir_internal ( "/var/tmp" , ret
);
579 int tmp_dir ( const char ** ret
) {
581 /* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually
582 * backed by an in-memory file system: /tmp. */
584 return tmp_dir_internal ( "/tmp" , ret
);
587 int inotify_add_watch_fd ( int fd
, int what
, uint32_t mask
) {
588 char path
[ strlen ( "/proc/self/fd/" ) + DECIMAL_STR_MAX ( int ) + 1 ];
591 /* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */
592 xsprintf ( path
, "/proc/self/fd/%i" , what
);
594 r
= inotify_add_watch ( fd
, path
, mask
);
601 int chase_symlinks ( const char * path
, const char * original_root
, unsigned flags
, char ** ret
) {
602 _cleanup_free_
char * buffer
= NULL
, * done
= NULL
, * root
= NULL
;
603 _cleanup_close_
int fd
= - 1 ;
604 unsigned max_follow
= 32 ; /* how many symlinks to follow before giving up and returning ELOOP */
611 /* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following
612 * symlinks relative to a root directory, instead of the root of the host.
614 * Note that "root" primarily matters if we encounter an absolute symlink. It is also used when following
615 * relative symlinks to ensure they cannot be used to "escape" the root directory. The path parameter passed is
616 * assumed to be already prefixed by it, except if the CHASE_PREFIX_ROOT flag is set, in which case it is first
617 * prefixed accordingly.
619 * Algorithmically this operates on two path buffers: "done" are the components of the path we already
620 * processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to
621 * process. On each iteration, we move one component from "todo" to "done", processing it's special meaning
622 * each time. The "todo" path always starts with at least one slash, the "done" path always ends in no
623 * slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races
626 * Suggested usage: whenever you want to canonicalize a path, use this function. Pass the absolute path you got
627 * as-is: fully qualified and relative to your host's root. Optionally, specify the root parameter to tell this
628 * function what to do when encountering a symlink with an absolute path as directory: prefix it by the
631 * Note: there's also chase_symlinks_prefix() (see below), which as first step prefixes the passed path by the
635 r
= path_make_absolute_cwd ( original_root
, & root
);
639 if ( flags
& CHASE_PREFIX_ROOT
)
640 path
= prefix_roota ( root
, path
);
643 r
= path_make_absolute_cwd ( path
, & buffer
);
647 fd
= open ( "/" , O_CLOEXEC
| O_NOFOLLOW
| O_PATH
);
653 _cleanup_free_
char * first
= NULL
;
654 _cleanup_close_
int child
= - 1 ;
658 /* Determine length of first component in the path */
659 n
= strspn ( todo
, "/" ); /* The slashes */
660 m
= n
+ strcspn ( todo
+ n
, "/" ); /* The entire length of the component */
662 /* Extract the first component. */
663 first
= strndup ( todo
, m
);
669 /* Just a single slash? Then we reached the end. */
670 if ( isempty ( first
) || path_equal ( first
, "/" ))
673 /* Just a dot? Then let's eat this up. */
674 if ( path_equal ( first
, "/." ))
677 /* Two dots? Then chop off the last bit of what we already found out. */
678 if ( path_equal ( first
, "/.." )) {
679 _cleanup_free_
char * parent
= NULL
;
682 /* If we already are at the top, then going up will not change anything. This is in-line with
683 * how the kernel handles this. */
684 if ( isempty ( done
) || path_equal ( done
, "/" ))
687 parent
= dirname_malloc ( done
);
691 /* Don't allow this to leave the root dir. */
693 path_startswith ( done
, root
) &&
694 ! path_startswith ( parent
, root
))
697 free_and_replace ( done
, parent
);
699 fd_parent
= openat ( fd
, ".." , O_CLOEXEC
| O_NOFOLLOW
| O_PATH
);
709 /* Otherwise let's see what this is. */
710 child
= openat ( fd
, first
+ n
, O_CLOEXEC
| O_NOFOLLOW
| O_PATH
);
713 if ( errno
== ENOENT
&&
714 ( flags
& CHASE_NONEXISTENT
) &&
715 ( isempty ( todo
) || path_is_safe ( todo
))) {
717 /* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return
718 * what we got so far. But don't allow this if the remaining path contains "../ or "./"
719 * or something else weird. */
721 if (! strextend (& done
, first
, todo
, NULL
))
731 if ( fstat ( child
, & st
) < 0 )
734 if ( S_ISLNK ( st
. st_mode
)) {
735 _cleanup_free_
char * destination
= NULL
;
737 /* This is a symlink, in this case read the destination. But let's make sure we don't follow
738 * symlinks without bounds. */
739 if (-- max_follow
<= 0 )
742 r
= readlinkat_malloc ( fd
, first
+ n
, & destination
);
745 if ( isempty ( destination
))
748 if ( path_is_absolute ( destination
)) {
750 /* An absolute destination. Start the loop from the beginning, but use the root
751 * directory as base. */
754 fd
= open ( root
?: "/" , O_CLOEXEC
| O_NOFOLLOW
| O_PATH
);
758 free_and_replace ( buffer
, destination
);
763 /* Note that we do not revalidate the root, we take it as is. */
775 /* A relative destination. If so, this is what we'll prefix what's left to do with what
776 * we just read, and start the loop again, but remain in the current directory. */
778 joined
= strjoin ( "/" , destination
, todo
);
783 todo
= buffer
= joined
;
789 /* If this is not a symlink, then let's just add the name we read to what we already verified. */
794 if (! strextend (& done
, first
, NULL
))
798 /* And iterate again, but go one directory further down. */
805 /* Special case, turn the empty string into "/", to indicate the root directory. */