2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 1999-2006 Robert N. M. Watson
7 * This software was developed by Robert Watson for the TrustedBSD Project.
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * Developed by the TrustedBSD Project.
33 * ACL support routines specific to POSIX.1e access control lists. These are
34 * utility routines for code common across file systems implementing POSIX.1e
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
41 #include <sys/param.h>
42 #include <sys/kernel.h>
43 #include <sys/module.h>
44 #include <sys/systm.h>
45 #include <sys/mount.h>
47 #include <sys/vnode.h>
48 #include <sys/errno.h>
53 * Implement a version of vaccess() that understands POSIX.1e ACL semantics;
54 * the access ACL has already been prepared for evaluation by the file system
55 * and is passed via 'uid', 'gid', and 'acl'. Return 0 on success, else an
59 vaccess_acl_posix1e(enum vtype type, uid_t file_uid, gid_t file_gid,
60 struct acl *acl, accmode_t accmode, struct ucred *cred, int *privused)
62 struct acl_entry *acl_other, *acl_mask;
63 accmode_t dac_granted;
64 accmode_t priv_granted;
65 accmode_t acl_mask_granted;
68 KASSERT((accmode & ~(VEXEC | VWRITE | VREAD | VADMIN | VAPPEND)) == 0,
69 ("invalid bit in accmode"));
70 KASSERT((accmode & VAPPEND) == 0 || (accmode & VWRITE),
71 ("VAPPEND without VWRITE"));
74 * Look for a normal, non-privileged way to access the file/directory
75 * as requested. If it exists, go with that. Otherwise, attempt to
76 * use privileges granted via priv_granted. In some cases, which
77 * privileges to use may be ambiguous due to "best match", in which
78 * case fall back on first match for the time being.
84 * Determine privileges now, but don't apply until we've found a DAC
85 * entry that matches but has failed to allow access.
87 * XXXRW: Ideally, we'd determine the privileges required before
93 if ((accmode & VEXEC) && !priv_check_cred(cred,
95 priv_granted |= VEXEC;
98 * Ensure that at least one execute bit is on. Otherwise,
99 * a privileged user will always succeed, and we don't want
100 * this to happen unless the file really is executable.
102 if ((accmode & VEXEC) && (acl_posix1e_acl_to_mode(acl) &
103 (S_IXUSR | S_IXGRP | S_IXOTH)) != 0 &&
104 !priv_check_cred(cred, PRIV_VFS_EXEC, 0))
105 priv_granted |= VEXEC;
108 if ((accmode & VREAD) && !priv_check_cred(cred, PRIV_VFS_READ, 0))
109 priv_granted |= VREAD;
111 if (((accmode & VWRITE) || (accmode & VAPPEND)) &&
112 !priv_check_cred(cred, PRIV_VFS_WRITE, 0))
113 priv_granted |= (VWRITE | VAPPEND);
115 if ((accmode & VADMIN) && !priv_check_cred(cred, PRIV_VFS_ADMIN, 0))
116 priv_granted |= VADMIN;
119 * The owner matches if the effective uid associated with the
120 * credential matches that of the ACL_USER_OBJ entry. While we're
121 * doing the first scan, also cache the location of the ACL_MASK and
122 * ACL_OTHER entries, preventing some future iterations.
124 acl_mask = acl_other = NULL;
125 for (i = 0; i < acl->acl_cnt; i++) {
126 switch (acl->acl_entry[i].ae_tag) {
128 if (file_uid != cred->cr_uid)
131 dac_granted |= VADMIN;
132 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
133 dac_granted |= VEXEC;
134 if (acl->acl_entry[i].ae_perm & ACL_READ)
135 dac_granted |= VREAD;
136 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
137 dac_granted |= (VWRITE | VAPPEND);
138 if ((accmode & dac_granted) == accmode)
142 * XXXRW: Do privilege lookup here.
144 if ((accmode & (dac_granted | priv_granted)) ==
146 if (privused != NULL)
153 acl_mask = &acl->acl_entry[i];
157 acl_other = &acl->acl_entry[i];
166 * An ACL_OTHER entry should always exist in a valid access ACL. If
167 * it doesn't, then generate a serious failure. For now, this means
168 * a debugging message and EPERM, but in the future should probably
171 if (acl_other == NULL) {
173 * XXX This should never happen
175 printf("vaccess_acl_posix1e: ACL_OTHER missing\n");
180 * Checks against ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP fields are
181 * masked by an ACL_MASK entry, if any. As such, first identify the
182 * ACL_MASK field, then iterate through identifying potential user
183 * matches, then group matches. If there is no ACL_MASK, assume that
184 * the mask allows all requests to succeed.
186 if (acl_mask != NULL) {
187 acl_mask_granted = 0;
188 if (acl_mask->ae_perm & ACL_EXECUTE)
189 acl_mask_granted |= VEXEC;
190 if (acl_mask->ae_perm & ACL_READ)
191 acl_mask_granted |= VREAD;
192 if (acl_mask->ae_perm & ACL_WRITE)
193 acl_mask_granted |= (VWRITE | VAPPEND);
195 acl_mask_granted = VEXEC | VREAD | VWRITE | VAPPEND;
198 * Check ACL_USER ACL entries. There will either be one or no
199 * matches; if there is one, we accept or rejected based on the
200 * match; otherwise, we continue on to groups.
202 for (i = 0; i < acl->acl_cnt; i++) {
203 switch (acl->acl_entry[i].ae_tag) {
205 if (acl->acl_entry[i].ae_id != cred->cr_uid)
208 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
209 dac_granted |= VEXEC;
210 if (acl->acl_entry[i].ae_perm & ACL_READ)
211 dac_granted |= VREAD;
212 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
213 dac_granted |= (VWRITE | VAPPEND);
214 dac_granted &= acl_mask_granted;
215 if ((accmode & dac_granted) == accmode)
218 * XXXRW: Do privilege lookup here.
220 if ((accmode & (dac_granted | priv_granted)) !=
224 if (privused != NULL)
231 * Group match is best-match, not first-match, so find a "best"
232 * match. Iterate across, testing each potential group match. Make
233 * sure we keep track of whether we found a match or not, so that we
234 * know if we should try again with any available privilege, or if we
235 * should move on to ACL_OTHER.
238 for (i = 0; i < acl->acl_cnt; i++) {
239 switch (acl->acl_entry[i].ae_tag) {
241 if (!groupmember(file_gid, cred))
244 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
245 dac_granted |= VEXEC;
246 if (acl->acl_entry[i].ae_perm & ACL_READ)
247 dac_granted |= VREAD;
248 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
249 dac_granted |= (VWRITE | VAPPEND);
250 dac_granted &= acl_mask_granted;
252 if ((accmode & dac_granted) == accmode)
259 if (!groupmember(acl->acl_entry[i].ae_id, cred))
262 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
263 dac_granted |= VEXEC;
264 if (acl->acl_entry[i].ae_perm & ACL_READ)
265 dac_granted |= VREAD;
266 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
267 dac_granted |= (VWRITE | VAPPEND);
268 dac_granted &= acl_mask_granted;
270 if ((accmode & dac_granted) == accmode)
281 if (group_matched == 1) {
283 * There was a match, but it did not grant rights via pure
284 * DAC. Try again, this time with privilege.
286 for (i = 0; i < acl->acl_cnt; i++) {
287 switch (acl->acl_entry[i].ae_tag) {
289 if (!groupmember(file_gid, cred))
292 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
293 dac_granted |= VEXEC;
294 if (acl->acl_entry[i].ae_perm & ACL_READ)
295 dac_granted |= VREAD;
296 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
297 dac_granted |= (VWRITE | VAPPEND);
298 dac_granted &= acl_mask_granted;
301 * XXXRW: Do privilege lookup here.
303 if ((accmode & (dac_granted | priv_granted))
307 if (privused != NULL)
312 if (!groupmember(acl->acl_entry[i].ae_id,
316 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
317 dac_granted |= VEXEC;
318 if (acl->acl_entry[i].ae_perm & ACL_READ)
319 dac_granted |= VREAD;
320 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
321 dac_granted |= (VWRITE | VAPPEND);
322 dac_granted &= acl_mask_granted;
325 * XXXRW: Do privilege lookup here.
327 if ((accmode & (dac_granted | priv_granted))
331 if (privused != NULL)
340 * Even with privilege, group membership was not sufficient.
347 * Fall back on ACL_OTHER. ACL_MASK is not applied to ACL_OTHER.
350 if (acl_other->ae_perm & ACL_EXECUTE)
351 dac_granted |= VEXEC;
352 if (acl_other->ae_perm & ACL_READ)
353 dac_granted |= VREAD;
354 if (acl_other->ae_perm & ACL_WRITE)
355 dac_granted |= (VWRITE | VAPPEND);
357 if ((accmode & dac_granted) == accmode)
360 * XXXRW: Do privilege lookup here.
362 if ((accmode & (dac_granted | priv_granted)) == accmode) {
363 if (privused != NULL)
369 return ((accmode & VADMIN) ? EPERM : EACCES);
373 * For the purposes of filesystems maintaining the _OBJ entries in an inode
374 * with a mode_t field, this routine converts a mode_t entry to an
378 acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode)
411 printf("acl_posix1e_mode_to_perm: invalid tag (%d)\n", tag);
417 * Given inode information (uid, gid, mode), return an acl entry of the
421 acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode)
423 struct acl_entry acl_entry;
425 acl_entry.ae_tag = tag;
426 acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode);
427 acl_entry.ae_entry_type = 0;
428 acl_entry.ae_flags = 0;
431 acl_entry.ae_id = uid;
435 acl_entry.ae_id = gid;
439 acl_entry.ae_id = ACL_UNDEFINED_ID;
443 acl_entry.ae_id = ACL_UNDEFINED_ID;
444 printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag);
451 * Utility function to generate a file mode given appropriate ACL entries.
454 acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry,
455 struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry)
460 if (acl_user_obj_entry->ae_perm & ACL_EXECUTE)
462 if (acl_user_obj_entry->ae_perm & ACL_READ)
464 if (acl_user_obj_entry->ae_perm & ACL_WRITE)
466 if (acl_group_obj_entry->ae_perm & ACL_EXECUTE)
468 if (acl_group_obj_entry->ae_perm & ACL_READ)
470 if (acl_group_obj_entry->ae_perm & ACL_WRITE)
472 if (acl_other_entry->ae_perm & ACL_EXECUTE)
474 if (acl_other_entry->ae_perm & ACL_READ)
476 if (acl_other_entry->ae_perm & ACL_WRITE)
483 * Utility function to generate a file mode given a complete POSIX.1e access
484 * ACL. Note that if the ACL is improperly formed, this may result in a
488 acl_posix1e_acl_to_mode(struct acl *acl)
490 struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other;
494 * Find the ACL entries relevant to a POSIX permission mode.
496 acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL;
497 for (i = 0; i < acl->acl_cnt; i++) {
498 switch (acl->acl_entry[i].ae_tag) {
500 acl_user_obj = &acl->acl_entry[i];
504 acl_group_obj = &acl->acl_entry[i];
508 acl_other = &acl->acl_entry[i];
512 acl_mask = &acl->acl_entry[i];
520 panic("acl_posix1e_acl_to_mode: bad ae_tag");
524 if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL)
525 panic("acl_posix1e_acl_to_mode: missing base ae_tags");
528 * POSIX.1e specifies that if there is an ACL_MASK entry, we replace
529 * the mode "group" bits with its permissions. If there isn't, we
530 * use the ACL_GROUP_OBJ permissions.
532 if (acl_mask != NULL)
533 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask,
536 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj,
541 * Perform a syntactic check of the ACL, sufficient to allow an implementing
542 * filesystem to determine if it should accept this and rely on the POSIX.1e
546 acl_posix1e_check(struct acl *acl)
548 int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group;
549 int num_acl_mask, num_acl_other, i;
552 * Verify that the number of entries does not exceed the maximum
555 * Verify that the correct number of various sorts of ae_tags are
557 * Exactly one ACL_USER_OBJ
558 * Exactly one ACL_GROUP_OBJ
559 * Exactly one ACL_OTHER
560 * If any ACL_USER or ACL_GROUP entries appear, then exactly one
561 * ACL_MASK entry must also appear.
563 * Verify that all ae_perm entries are in ACL_PERM_BITS.
565 * Verify all ae_tag entries are understood by this implementation.
567 * Note: Does not check for uniqueness of qualifier (ae_id) field.
569 num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group =
570 num_acl_mask = num_acl_other = 0;
571 if (acl->acl_cnt > ACL_MAX_ENTRIES)
573 for (i = 0; i < acl->acl_cnt; i++) {
575 * Check for a valid tag.
577 switch(acl->acl_entry[i].ae_tag) {
579 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
580 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
585 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
586 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
591 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
596 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
601 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
602 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
607 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
608 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
616 * Check for valid perm entries.
618 if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) !=
622 if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) ||
623 (num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1))
625 if (((num_acl_group != 0) || (num_acl_user != 0)) &&
632 * Given a requested mode for a new object, and a default ACL, combine the
633 * two to produce a new mode. Be careful not to clear any bits that aren't
634 * intended to be affected by the POSIX.1e ACL. Eventually, this might also
635 * take the cmask as an argument, if we push that down into
636 * per-filesystem-code.
639 acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl)
645 * The current composition policy is that a permission bit must be
646 * set in *both* the ACL and the requested creation mode for it to
647 * appear in the resulting mode/ACL. First clear any possibly
648 * effected bits, then reconstruct.
650 mode &= ACL_PRESERVE_MASK;
651 mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl));
658 acl_posix1e_modload(module_t mod, int what, void *arg)
686 static moduledata_t acl_posix1e_mod = {
692 DECLARE_MODULE(acl_posix1e, acl_posix1e_mod, SI_SUB_VFS, SI_ORDER_FIRST);
693 MODULE_VERSION(acl_posix1e, 1);