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, PRIV_VFS_LOOKUP))
94 priv_granted |= VEXEC;
97 * Ensure that at least one execute bit is on. Otherwise,
98 * a privileged user will always succeed, and we don't want
99 * this to happen unless the file really is executable.
101 if ((accmode & VEXEC) && (acl_posix1e_acl_to_mode(acl) &
102 (S_IXUSR | S_IXGRP | S_IXOTH)) != 0 &&
103 !priv_check_cred(cred, PRIV_VFS_EXEC))
104 priv_granted |= VEXEC;
107 if ((accmode & VREAD) && !priv_check_cred(cred, PRIV_VFS_READ))
108 priv_granted |= VREAD;
110 if (((accmode & VWRITE) || (accmode & VAPPEND)) &&
111 !priv_check_cred(cred, PRIV_VFS_WRITE))
112 priv_granted |= (VWRITE | VAPPEND);
114 if ((accmode & VADMIN) && !priv_check_cred(cred, PRIV_VFS_ADMIN))
115 priv_granted |= VADMIN;
118 * The owner matches if the effective uid associated with the
119 * credential matches that of the ACL_USER_OBJ entry. While we're
120 * doing the first scan, also cache the location of the ACL_MASK and
121 * ACL_OTHER entries, preventing some future iterations.
123 acl_mask = acl_other = NULL;
124 for (i = 0; i < acl->acl_cnt; i++) {
125 switch (acl->acl_entry[i].ae_tag) {
127 if (file_uid != cred->cr_uid)
130 dac_granted |= VADMIN;
131 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
132 dac_granted |= VEXEC;
133 if (acl->acl_entry[i].ae_perm & ACL_READ)
134 dac_granted |= VREAD;
135 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
136 dac_granted |= (VWRITE | VAPPEND);
137 if ((accmode & dac_granted) == accmode)
141 * XXXRW: Do privilege lookup here.
143 if ((accmode & (dac_granted | priv_granted)) ==
145 if (privused != NULL)
152 acl_mask = &acl->acl_entry[i];
156 acl_other = &acl->acl_entry[i];
165 * An ACL_OTHER entry should always exist in a valid access ACL. If
166 * it doesn't, then generate a serious failure. For now, this means
167 * a debugging message and EPERM, but in the future should probably
170 if (acl_other == NULL) {
172 * XXX This should never happen
174 printf("vaccess_acl_posix1e: ACL_OTHER missing\n");
179 * Checks against ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP fields are
180 * masked by an ACL_MASK entry, if any. As such, first identify the
181 * ACL_MASK field, then iterate through identifying potential user
182 * matches, then group matches. If there is no ACL_MASK, assume that
183 * the mask allows all requests to succeed.
185 if (acl_mask != NULL) {
186 acl_mask_granted = 0;
187 if (acl_mask->ae_perm & ACL_EXECUTE)
188 acl_mask_granted |= VEXEC;
189 if (acl_mask->ae_perm & ACL_READ)
190 acl_mask_granted |= VREAD;
191 if (acl_mask->ae_perm & ACL_WRITE)
192 acl_mask_granted |= (VWRITE | VAPPEND);
194 acl_mask_granted = VEXEC | VREAD | VWRITE | VAPPEND;
197 * Check ACL_USER ACL entries. There will either be one or no
198 * matches; if there is one, we accept or rejected based on the
199 * match; otherwise, we continue on to groups.
201 for (i = 0; i < acl->acl_cnt; i++) {
202 switch (acl->acl_entry[i].ae_tag) {
204 if (acl->acl_entry[i].ae_id != cred->cr_uid)
207 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
208 dac_granted |= VEXEC;
209 if (acl->acl_entry[i].ae_perm & ACL_READ)
210 dac_granted |= VREAD;
211 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
212 dac_granted |= (VWRITE | VAPPEND);
213 dac_granted &= acl_mask_granted;
214 if ((accmode & dac_granted) == accmode)
217 * XXXRW: Do privilege lookup here.
219 if ((accmode & (dac_granted | priv_granted)) !=
223 if (privused != NULL)
230 * Group match is best-match, not first-match, so find a "best"
231 * match. Iterate across, testing each potential group match. Make
232 * sure we keep track of whether we found a match or not, so that we
233 * know if we should try again with any available privilege, or if we
234 * should move on to ACL_OTHER.
237 for (i = 0; i < acl->acl_cnt; i++) {
238 switch (acl->acl_entry[i].ae_tag) {
240 if (!groupmember(file_gid, cred))
243 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
244 dac_granted |= VEXEC;
245 if (acl->acl_entry[i].ae_perm & ACL_READ)
246 dac_granted |= VREAD;
247 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
248 dac_granted |= (VWRITE | VAPPEND);
249 dac_granted &= acl_mask_granted;
251 if ((accmode & dac_granted) == accmode)
258 if (!groupmember(acl->acl_entry[i].ae_id, cred))
261 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
262 dac_granted |= VEXEC;
263 if (acl->acl_entry[i].ae_perm & ACL_READ)
264 dac_granted |= VREAD;
265 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
266 dac_granted |= (VWRITE | VAPPEND);
267 dac_granted &= acl_mask_granted;
269 if ((accmode & dac_granted) == accmode)
280 if (group_matched == 1) {
282 * There was a match, but it did not grant rights via pure
283 * DAC. Try again, this time with privilege.
285 for (i = 0; i < acl->acl_cnt; i++) {
286 switch (acl->acl_entry[i].ae_tag) {
288 if (!groupmember(file_gid, cred))
291 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
292 dac_granted |= VEXEC;
293 if (acl->acl_entry[i].ae_perm & ACL_READ)
294 dac_granted |= VREAD;
295 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
296 dac_granted |= (VWRITE | VAPPEND);
297 dac_granted &= acl_mask_granted;
300 * XXXRW: Do privilege lookup here.
302 if ((accmode & (dac_granted | priv_granted))
306 if (privused != NULL)
311 if (!groupmember(acl->acl_entry[i].ae_id,
315 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
316 dac_granted |= VEXEC;
317 if (acl->acl_entry[i].ae_perm & ACL_READ)
318 dac_granted |= VREAD;
319 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
320 dac_granted |= (VWRITE | VAPPEND);
321 dac_granted &= acl_mask_granted;
324 * XXXRW: Do privilege lookup here.
326 if ((accmode & (dac_granted | priv_granted))
330 if (privused != NULL)
339 * Even with privilege, group membership was not sufficient.
346 * Fall back on ACL_OTHER. ACL_MASK is not applied to ACL_OTHER.
349 if (acl_other->ae_perm & ACL_EXECUTE)
350 dac_granted |= VEXEC;
351 if (acl_other->ae_perm & ACL_READ)
352 dac_granted |= VREAD;
353 if (acl_other->ae_perm & ACL_WRITE)
354 dac_granted |= (VWRITE | VAPPEND);
356 if ((accmode & dac_granted) == accmode)
359 * XXXRW: Do privilege lookup here.
361 if ((accmode & (dac_granted | priv_granted)) == accmode) {
362 if (privused != NULL)
368 return ((accmode & VADMIN) ? EPERM : EACCES);
372 * For the purposes of filesystems maintaining the _OBJ entries in an inode
373 * with a mode_t field, this routine converts a mode_t entry to an
377 acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode)
410 printf("acl_posix1e_mode_to_perm: invalid tag (%d)\n", tag);
416 * Given inode information (uid, gid, mode), return an acl entry of the
420 acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode)
422 struct acl_entry acl_entry;
424 acl_entry.ae_tag = tag;
425 acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode);
426 acl_entry.ae_entry_type = 0;
427 acl_entry.ae_flags = 0;
430 acl_entry.ae_id = uid;
434 acl_entry.ae_id = gid;
438 acl_entry.ae_id = ACL_UNDEFINED_ID;
442 acl_entry.ae_id = ACL_UNDEFINED_ID;
443 printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag);
450 * Utility function to generate a file mode given appropriate ACL entries.
453 acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry,
454 struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry)
459 if (acl_user_obj_entry->ae_perm & ACL_EXECUTE)
461 if (acl_user_obj_entry->ae_perm & ACL_READ)
463 if (acl_user_obj_entry->ae_perm & ACL_WRITE)
465 if (acl_group_obj_entry->ae_perm & ACL_EXECUTE)
467 if (acl_group_obj_entry->ae_perm & ACL_READ)
469 if (acl_group_obj_entry->ae_perm & ACL_WRITE)
471 if (acl_other_entry->ae_perm & ACL_EXECUTE)
473 if (acl_other_entry->ae_perm & ACL_READ)
475 if (acl_other_entry->ae_perm & ACL_WRITE)
482 * Utility function to generate a file mode given a complete POSIX.1e access
483 * ACL. Note that if the ACL is improperly formed, this may result in a
487 acl_posix1e_acl_to_mode(struct acl *acl)
489 struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other;
493 * Find the ACL entries relevant to a POSIX permission mode.
495 acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL;
496 for (i = 0; i < acl->acl_cnt; i++) {
497 switch (acl->acl_entry[i].ae_tag) {
499 acl_user_obj = &acl->acl_entry[i];
503 acl_group_obj = &acl->acl_entry[i];
507 acl_other = &acl->acl_entry[i];
511 acl_mask = &acl->acl_entry[i];
519 panic("acl_posix1e_acl_to_mode: bad ae_tag");
523 if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL)
524 panic("acl_posix1e_acl_to_mode: missing base ae_tags");
527 * POSIX.1e specifies that if there is an ACL_MASK entry, we replace
528 * the mode "group" bits with its permissions. If there isn't, we
529 * use the ACL_GROUP_OBJ permissions.
531 if (acl_mask != NULL)
532 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask,
535 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj,
540 * Perform a syntactic check of the ACL, sufficient to allow an implementing
541 * filesystem to determine if it should accept this and rely on the POSIX.1e
545 acl_posix1e_check(struct acl *acl)
547 int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group;
548 int num_acl_mask, num_acl_other, i;
551 * Verify that the number of entries does not exceed the maximum
554 * Verify that the correct number of various sorts of ae_tags are
556 * Exactly one ACL_USER_OBJ
557 * Exactly one ACL_GROUP_OBJ
558 * Exactly one ACL_OTHER
559 * If any ACL_USER or ACL_GROUP entries appear, then exactly one
560 * ACL_MASK entry must also appear.
562 * Verify that all ae_perm entries are in ACL_PERM_BITS.
564 * Verify all ae_tag entries are understood by this implementation.
566 * Note: Does not check for uniqueness of qualifier (ae_id) field.
568 num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group =
569 num_acl_mask = num_acl_other = 0;
570 if (acl->acl_cnt > ACL_MAX_ENTRIES)
572 for (i = 0; i < acl->acl_cnt; i++) {
574 * Check for a valid tag.
576 switch(acl->acl_entry[i].ae_tag) {
578 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
579 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
584 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
585 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
590 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
595 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
600 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
601 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
606 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
607 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
615 * Check for valid perm entries.
617 if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) !=
621 if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) ||
622 (num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1))
624 if (((num_acl_group != 0) || (num_acl_user != 0)) &&
631 * Given a requested mode for a new object, and a default ACL, combine the
632 * two to produce a new mode. Be careful not to clear any bits that aren't
633 * intended to be affected by the POSIX.1e ACL. Eventually, this might also
634 * take the cmask as an argument, if we push that down into
635 * per-filesystem-code.
638 acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl)
644 * The current composition policy is that a permission bit must be
645 * set in *both* the ACL and the requested creation mode for it to
646 * appear in the resulting mode/ACL. First clear any possibly
647 * effected bits, then reconstruct.
649 mode &= ACL_PRESERVE_MASK;
650 mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl));
657 acl_posix1e_modload(module_t mod, int what, void *arg)
685 static moduledata_t acl_posix1e_mod = {
691 DECLARE_MODULE(acl_posix1e, acl_posix1e_mod, SI_SUB_VFS, SI_ORDER_FIRST);
692 MODULE_VERSION(acl_posix1e, 1);