2 * @file apply-default-acl.c
4 * @brief The entire implementation.
8 /* On Linux, ftw.h needs this special voodoo to work. */
9 #define _XOPEN_SOURCE 500
13 #include <ftw.h> /* nftw() et al. */
15 #include <libgen.h> /* dirname() */
16 #include <limits.h> /* PATH_MAX */
25 #include <acl/libacl.h> /* acl_get_perm, not portable */
26 #include <sys/types.h>
29 /* Most of the libacl functions return 1 for success, 0 for failure,
36 /* Command-line options */
37 static bool no_exec_mask
= false;
42 * @brief Get the mode bits from the given path.
45 * The path (file or directory) whose mode we want.
47 * @return A mode_t (st_mode) structure containing the mode bits.
48 * See sys/stat.h for details.
50 mode_t
get_mode(const char* path
) {
57 int result
= stat(path
, &s
);
63 /* errno will be set already by stat() */
71 * @brief Determine whether or not the given path is a regular file.
76 * @return true if @c path is a regular file, false otherwise.
78 bool is_regular_file(const char* path
) {
84 int result
= stat(path
, &s
);
86 return S_ISREG(s
.st_mode
);
96 * @brief Determine whether or not the given path is a directory.
101 * @return true if @c path is a directory, false otherwise.
103 bool is_directory(const char* path
) {
109 int result
= stat(path
, &s
);
111 return S_ISDIR(s
.st_mode
);
121 * @brief Update (or create) an entry in an @b minimal ACL.
123 * This function will not work if @c aclp contains extended
124 * entries. This is fine for our purposes, since we call @c wipe_acls
125 * on each path before applying the default to it.
127 * The assumption that there are no extended entries makes things much
128 * simpler. For example, we only have to update the ACL_USER_OBJ,
129 * ACL_GROUP_OBJ, and ACL_OTHER entries -- all others can simply be
130 * created anew. This means we don't have to fool around comparing
131 * named-user/group entries.
134 * A pointer to the acl_t structure whose entry we want to modify.
137 * The new entry. If @c entry contains a user/group/other entry, we
138 * update the existing one. Otherwise we create a new entry.
140 * @return If there is an unexpected library error, ACL_ERROR is
141 * returned. Otherwise, ACL_SUCCESS.
144 int acl_set_entry(acl_t
* aclp
,
148 int gt_result
= acl_get_tag_type(entry
, &entry_tag
);
149 if (gt_result
== ACL_ERROR
) {
150 perror("acl_set_entry (acl_get_tag_type)");
154 acl_permset_t entry_permset
;
155 int ps_result
= acl_get_permset(entry
, &entry_permset
);
156 if (ps_result
== ACL_ERROR
) {
157 perror("acl_set_entry (acl_get_permset)");
161 acl_entry_t existing_entry
;
162 /* Loop through the given ACL looking for matching entries. */
163 int result
= acl_get_entry(*aclp
, ACL_FIRST_ENTRY
, &existing_entry
);
165 while (result
== ACL_SUCCESS
) {
166 acl_tag_t existing_tag
= ACL_UNDEFINED_TAG
;
167 int tag_result
= acl_get_tag_type(existing_entry
, &existing_tag
);
169 if (tag_result
== ACL_ERROR
) {
170 perror("set_acl_tag_permset (acl_get_tag_type)");
174 if (existing_tag
== entry_tag
) {
175 if (entry_tag
== ACL_USER_OBJ
||
176 entry_tag
== ACL_GROUP_OBJ
||
177 entry_tag
== ACL_OTHER
) {
178 /* Only update for these three since all other tags will have
179 been wiped. These three are guaranteed to exist, so if we
180 match one of them, we're allowed to return ACL_SUCCESS
181 below and bypass the rest of the function. */
182 acl_permset_t existing_permset
;
183 int gep_result
= acl_get_permset(existing_entry
, &existing_permset
);
184 if (gep_result
== ACL_ERROR
) {
185 perror("acl_set_entry (acl_get_permset)");
189 int s_result
= acl_set_permset(existing_entry
, entry_permset
);
190 if (s_result
== ACL_ERROR
) {
191 perror("acl_set_entry (acl_set_permset)");
200 result
= acl_get_entry(*aclp
, ACL_NEXT_ENTRY
, &existing_entry
);
203 /* This catches both the initial acl_get_entry and the ones at the
205 if (result
== ACL_ERROR
) {
206 perror("acl_set_entry (acl_get_entry)");
210 /* If we've made it this far, we need to add a new entry to the
212 acl_entry_t new_entry
;
214 /* We allocate memory here that we should release! */
215 int c_result
= acl_create_entry(aclp
, &new_entry
);
216 if (c_result
== ACL_ERROR
) {
217 perror("acl_set_entry (acl_create_entry)");
221 int st_result
= acl_set_tag_type(new_entry
, entry_tag
);
222 if (st_result
== ACL_ERROR
) {
223 perror("acl_set_entry (acl_set_tag_type)");
227 int s_result
= acl_set_permset(new_entry
, entry_permset
);
228 if (s_result
== ACL_ERROR
) {
229 perror("acl_set_entry (acl_set_permset)");
233 if (entry_tag
== ACL_USER
|| entry_tag
== ACL_GROUP
) {
234 /* We need to set the qualifier too. */
235 void* entry_qual
= acl_get_qualifier(entry
);
236 if (entry_qual
== (void*)NULL
) {
237 perror("acl_set_entry (acl_get_qualifier)");
241 int sq_result
= acl_set_qualifier(new_entry
, entry_qual
);
242 if (sq_result
== ACL_ERROR
) {
243 perror("acl_set_entry (acl_set_qualifier)");
254 * @brief Determine the number of entries in the given ACL.
257 * A pointer to an acl_t structure.
259 * @return Either the non-negative number of entries in @c acl, or
260 * ACL_ERROR on error.
262 int acl_entry_count(acl_t
* acl
) {
266 int result
= acl_get_entry(*acl
, ACL_FIRST_ENTRY
, &entry
);
268 while (result
== ACL_SUCCESS
) {
270 result
= acl_get_entry(*acl
, ACL_NEXT_ENTRY
, &entry
);
273 if (result
== ACL_ERROR
) {
274 perror("acl_entry_count (acl_get_entry)");
284 * @brief Determine whether or not the given ACL is minimal.
286 * An ACL is minimal if it has fewer than four entries.
289 * A pointer to an acl_t structure.
292 * - ACL_SUCCESS - @c acl is minimal
293 * - ACL_FAILURE - @c acl is not minimal
294 * - ACL_ERROR - Unexpected library error
296 int acl_is_minimal(acl_t
* acl
) {
298 int ec
= acl_entry_count(acl
);
300 if (ec
== ACL_ERROR
) {
301 perror("acl_is_minimal (acl_entry_count)");
316 * @brief Determine whether the given path has an ACL whose mask
323 * - ACL_SUCCESS - @c path has a mask which denies execute.
324 * - ACL_FAILURE - The ACL for @c path does not deny execute,
325 * or @c path has no extended ACL at all.
326 * - ACL_ERROR - Unexpected library error.
328 int acl_execute_masked(const char* path
) {
330 acl_t acl
= acl_get_file(path
, ACL_TYPE_ACCESS
);
332 if (acl
== (acl_t
)NULL
) {
333 perror("acl_execute_masked (acl_get_file)");
337 /* Our return value. */
338 int result
= ACL_FAILURE
;
341 int ge_result
= acl_get_entry(acl
, ACL_FIRST_ENTRY
, &entry
);
343 while (ge_result
== ACL_SUCCESS
) {
344 acl_tag_t tag
= ACL_UNDEFINED_TAG
;
345 int tag_result
= acl_get_tag_type(entry
, &tag
);
347 if (tag_result
== ACL_ERROR
) {
348 perror("acl_execute_masked (acl_get_tag_type)");
353 if (tag
== ACL_MASK
) {
354 /* This is the mask entry, get its permissions, and see if
355 execute is specified. */
356 acl_permset_t permset
;
358 int ps_result
= acl_get_permset(entry
, &permset
);
359 if (ps_result
== ACL_ERROR
) {
360 perror("acl_execute_masked (acl_get_permset)");
365 int gp_result
= acl_get_perm(permset
, ACL_EXECUTE
);
366 if (gp_result
== ACL_ERROR
) {
367 perror("acl_execute_masked (acl_get_perm)");
372 if (gp_result
== ACL_FAILURE
) {
373 /* No execute bit set in the mask; execute not allowed. */
378 ge_result
= acl_get_entry(acl
, ACL_NEXT_ENTRY
, &entry
);
388 * @brief Determine whether @c path is executable (by anyone) or a
391 * This is used as part of the heuristic to determine whether or not
392 * we should mask the execute bit when inheriting an ACL. If @c path
393 * is a directory, the answer is a clear-cut yes. This behavior is
394 * modeled after the capital 'X' perms of setfacl.
396 * If @c path is a file, we check the @a effective permissions,
397 * contrary to what setfacl does.
403 * - ACL_SUCCESS - @c path is a directory, or someone has effective
405 * - ACL_FAILURE - @c path is a regular file and nobody can execute it.
406 * - ACL_ERROR - Unexpected library error.
408 int any_can_execute_or_dir(const char* path
) {
410 if (is_directory(path
)) {
411 /* That was easy... */
415 acl_t acl
= acl_get_file(path
, ACL_TYPE_ACCESS
);
417 if (acl
== (acl_t
)NULL
) {
418 perror("any_can_execute_or_dir (acl_get_file)");
422 /* Our return value. */
423 int result
= ACL_FAILURE
;
425 if (acl_is_minimal(&acl
)) {
426 mode_t mode
= get_mode(path
);
427 if (mode
& (S_IXUSR
| S_IXOTH
| S_IXGRP
)) {
428 result
= ACL_SUCCESS
;
432 result
= ACL_FAILURE
;
438 int ge_result
= acl_get_entry(acl
, ACL_FIRST_ENTRY
, &entry
);
440 while (ge_result
== ACL_SUCCESS
) {
441 acl_permset_t permset
;
443 int ps_result
= acl_get_permset(entry
, &permset
);
444 if (ps_result
== ACL_ERROR
) {
445 perror("any_can_execute_or_dir (acl_get_permset)");
450 int gp_result
= acl_get_perm(permset
, ACL_EXECUTE
);
451 if (gp_result
== ACL_ERROR
) {
452 perror("any_can_execute_or_dir (acl_get_perm)");
457 if (gp_result
== ACL_SUCCESS
) {
458 /* Only return one if this execute bit is not masked. */
459 if (acl_execute_masked(path
) != ACL_SUCCESS
) {
460 result
= ACL_SUCCESS
;
465 ge_result
= acl_get_entry(acl
, ACL_NEXT_ENTRY
, &entry
);
468 if (ge_result
== ACL_ERROR
) {
469 perror("any_can_execute_or_dir (acl_get_entry)");
482 * @brief Inherit the default ACL from @c parent to @c path.
484 * The @c parent parameter does not necessarily need to be the parent
485 * of @c path, although that will usually be the case. This overwrites
486 * any existing default ACL on @c path.
489 * The parent directory whose ACL we want to inherit.
492 * The target directory whose ACL we wish to overwrite (or create).
495 * - ACL_SUCCESS - The default ACL was inherited successfully.
496 * - ACL_FAILURE - Either @c parent or @c path is not a directory.
497 * - ACL_ERROR - Unexpected library error.
499 int inherit_default_acl(const char* path
, const char* parent
) {
500 /* Inherit the default ACL from parent to path. This overwrites any
501 * existing default ACL. Returns 1 for success, 0 for failure, and
505 /* Our return value. */
506 int result
= ACL_SUCCESS
;
513 if (!is_directory(path
) || !is_directory(parent
)) {
517 acl_t parent_acl
= acl_get_file(parent
, ACL_TYPE_DEFAULT
);
518 if (parent_acl
== (acl_t
)NULL
) {
519 perror("inherit_default_acl (acl_get_file)");
523 acl_t path_acl
= acl_dup(parent_acl
);
525 if (path_acl
== (acl_t
)NULL
) {
526 perror("inherit_default_acl (acl_dup)");
527 acl_free(parent_acl
);
531 int sf_result
= acl_set_file(path
, ACL_TYPE_DEFAULT
, path_acl
);
532 if (sf_result
== -1) {
533 perror("inherit_default_acl (acl_set_file)");
544 int wipe_acls(const char* path
) {
545 /* Remove ACL_USER, ACL_GROUP, and ACL_MASK entries from
546 path. Returns 1 for success, 0 for failure, and -1 on error. */
553 /* Finally, remove individual named/mask entries. */
554 acl_t acl
= acl_get_file(path
, ACL_TYPE_ACCESS
);
555 if (acl
== (acl_t
)NULL
) {
556 perror("wipe_acls (acl_get_file)");
560 /* Our return value. */
561 int result
= ACL_SUCCESS
;
564 int ge_result
= acl_get_entry(acl
, ACL_FIRST_ENTRY
, &entry
);
566 while (ge_result
== ACL_SUCCESS
) {
567 int d_result
= acl_delete_entry(acl
, entry
);
568 if (d_result
== ACL_ERROR
) {
569 perror("wipe_acls (acl_delete_entry)");
574 ge_result
= acl_get_entry(acl
, ACL_NEXT_ENTRY
, &entry
);
577 /* Catches the first acl_get_entry as well as the ones at the end of
579 if (ge_result
== ACL_ERROR
) {
580 perror("wipe_acls (acl_get_entry)");
585 int sf_result
= acl_set_file(path
, ACL_TYPE_ACCESS
, acl
);
586 if (sf_result
== ACL_ERROR
) {
587 perror("wipe_acls (acl_set_file)");
598 int apply_default_acl(const char* path
) {
599 /* Really apply the default ACL by looping through it. Returns one
600 * for success, zero for failure (i.e. no ACL), and -1 on unexpected
608 if (!is_regular_file(path
) && !is_directory(path
)) {
612 /* dirname mangles its argument */
613 char path_copy
[PATH_MAX
];
614 strncpy(path_copy
, path
, PATH_MAX
-1);
615 path_copy
[PATH_MAX
-1] = 0;
617 char* parent
= dirname(path_copy
);
618 if (!is_directory(parent
)) {
619 /* Make sure dirname() did what we think it did. */
623 /* Default to not masking the exec bit; i.e. applying the default
624 ACL literally. If --no-exec-mask was not specified, then we try
625 to "guess" whether or not to mask the exec bit. */
626 bool allow_exec
= true;
629 int ace_result
= any_can_execute_or_dir(path
);
631 if (ace_result
== ACL_ERROR
) {
632 perror("apply_default_acl (any_can_execute_or_dir)");
635 allow_exec
= (bool)ace_result
;
638 acl_t defacl
= acl_get_file(parent
, ACL_TYPE_DEFAULT
);
640 if (defacl
== (acl_t
)NULL
) {
641 perror("apply_default_acl (acl_get_file)");
645 /* Our return value. */
646 int result
= ACL_SUCCESS
;
648 int wipe_result
= wipe_acls(path
);
649 if (wipe_result
== ACL_ERROR
) {
650 perror("apply_default_acl (wipe_acls)");
655 /* Do this after wipe_acls(), otherwise we'll overwrite the wiped
656 ACL with this one. */
657 acl_t acl
= acl_get_file(path
, ACL_TYPE_ACCESS
);
658 if (acl
== (acl_t
)NULL
) {
659 perror("apply_default_acl (acl_get_file)");
663 /* If it's a directory, inherit the parent's default. */
664 int inherit_result
= inherit_default_acl(path
, parent
);
665 if (inherit_result
== ACL_ERROR
) {
666 perror("apply_default_acl (inherit_acls)");
672 int ge_result
= acl_get_entry(defacl
, ACL_FIRST_ENTRY
, &entry
);
674 while (ge_result
== ACL_SUCCESS
) {
675 acl_tag_t tag
= ACL_UNDEFINED_TAG
;
676 int tag_result
= acl_get_tag_type(entry
, &tag
);
678 if (tag_result
== ACL_ERROR
) {
679 perror("apply_default_acl (acl_get_tag_type)");
685 /* We've got an entry/tag from the default ACL. Get its permset. */
686 acl_permset_t permset
;
687 int ps_result
= acl_get_permset(entry
, &permset
);
688 if (ps_result
== ACL_ERROR
) {
689 perror("apply_default_acl (acl_get_permset)");
694 /* If this is a default mask, fix it up. */
695 if (tag
== ACL_MASK
||
696 tag
== ACL_USER_OBJ
||
697 tag
== ACL_GROUP_OBJ
||
701 /* The mask doesn't affect acl_user_obj, acl_group_obj (in
702 minimal ACLs) or acl_other entries, so if execute should be
703 masked, we have to do it manually. */
704 int d_result
= acl_delete_perm(permset
, ACL_EXECUTE
);
705 if (d_result
== ACL_ERROR
) {
706 perror("apply_default_acl (acl_delete_perm)");
711 int sp_result
= acl_set_permset(entry
, permset
);
712 if (sp_result
== ACL_ERROR
) {
713 perror("apply_default_acl (acl_set_permset)");
720 /* Finally, add the permset to the access ACL. */
721 int set_result
= acl_set_entry(&acl
, entry
);
722 if (set_result
== ACL_ERROR
) {
723 perror("apply_default_acl (acl_set_entry)");
728 ge_result
= acl_get_entry(defacl
, ACL_NEXT_ENTRY
, &entry
);
731 /* Catches the first acl_get_entry as well as the ones at the end of
733 if (ge_result
== ACL_ERROR
) {
734 perror("apply_default_acl (acl_get_entry)");
739 int sf_result
= acl_set_file(path
, ACL_TYPE_ACCESS
, acl
);
740 if (sf_result
== ACL_ERROR
) {
741 perror("apply_default_acl (acl_set_file)");
752 void usage(char* program_name
) {
754 * Print usage information.
756 printf("Apply any applicable default ACLs to the given files or "
758 printf("Usage: %s [flags] <target1> [<target2> [ <target3>...]]\n\n",
761 printf(" -h, --help Print this help message\n");
762 printf(" -r, --recursive Act on any given directories recursively\n");
763 printf(" -x, --no-exec-mask Apply execute permissions unconditionally\n");
769 int apply_default_acl_nftw(const char *target
,
770 const struct stat
*s
,
773 /* A wrapper around the apply_default_acl() function for use with
774 * nftw(). We need to adjust the return value so that nftw() doesn't
775 * think we've failed.
777 bool reapp_result
= apply_default_acl(target
);
787 bool apply_default_acl_recursive(const char *target
) {
788 /* Attempt to apply default ACLs recursively. If target is a
789 * directory, we recurse through its entries. If not, we just
790 * apply the default ACL to target.
792 * We ignore symlinks for consistency with chmod -r.
795 if (!is_directory(target
)) {
796 return apply_default_acl(target
);
799 int max_levels
= 256;
800 int flags
= FTW_PHYS
; /* Don't follow links. */
802 int nftw_result
= nftw(target
,
803 apply_default_acl_nftw
,
807 if (nftw_result
== 0) {
812 /* nftw will return -1 on error, or if the supplied function
813 * (apply_default_acl_nftw) returns a non-zero result, nftw will
816 if (nftw_result
== -1) {
817 perror("apply_default_acl_recursive (nftw)");
824 int main(int argc
, char* argv
[]) {
826 * Call apply_default_acl on each command-line argument.
833 bool recursive
= false;
834 /* bool no_exec_mask is declared static/global */
836 struct option long_options
[] = {
837 /* These options set a flag. */
838 {"help", no_argument
, NULL
, 'h'},
839 {"recursive", no_argument
, NULL
, 'r'},
840 {"no-exec-mask", no_argument
, NULL
, 'x'},
846 while ((opt
= getopt_long(argc
, argv
, "hrx", long_options
, NULL
)) != -1) {
863 int result
= EXIT_SUCCESS
;
866 for (arg_index
= optind
; arg_index
< argc
; arg_index
++) {
867 const char* target
= argv
[arg_index
];
868 bool reapp_result
= false;
871 reapp_result
= apply_default_acl_recursive(target
);
874 /* It's either normal file, or we're not operating recursively. */
875 reapp_result
= apply_default_acl(target
);
879 result
= EXIT_FAILURE
;