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)
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.
82 * Determine privileges now, but don't apply until we've found a DAC
83 * entry that matches but has failed to allow access.
85 * XXXRW: Ideally, we'd determine the privileges required before
91 if ((accmode & VEXEC) && !priv_check_cred(cred, PRIV_VFS_LOOKUP))
92 priv_granted |= VEXEC;
95 * Ensure that at least one execute bit is on. Otherwise,
96 * a privileged user will always succeed, and we don't want
97 * this to happen unless the file really is executable.
99 if ((accmode & VEXEC) && (acl_posix1e_acl_to_mode(acl) &
100 (S_IXUSR | S_IXGRP | S_IXOTH)) != 0 &&
101 !priv_check_cred(cred, PRIV_VFS_EXEC))
102 priv_granted |= VEXEC;
105 if ((accmode & VREAD) && !priv_check_cred(cred, PRIV_VFS_READ))
106 priv_granted |= VREAD;
108 if (((accmode & VWRITE) || (accmode & VAPPEND)) &&
109 !priv_check_cred(cred, PRIV_VFS_WRITE))
110 priv_granted |= (VWRITE | VAPPEND);
112 if ((accmode & VADMIN) && !priv_check_cred(cred, PRIV_VFS_ADMIN))
113 priv_granted |= VADMIN;
116 * The owner matches if the effective uid associated with the
117 * credential matches that of the ACL_USER_OBJ entry. While we're
118 * doing the first scan, also cache the location of the ACL_MASK and
119 * ACL_OTHER entries, preventing some future iterations.
121 acl_mask = acl_other = NULL;
122 for (i = 0; i < acl->acl_cnt; i++) {
123 switch (acl->acl_entry[i].ae_tag) {
125 if (file_uid != cred->cr_uid)
128 dac_granted |= VADMIN;
129 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
130 dac_granted |= VEXEC;
131 if (acl->acl_entry[i].ae_perm & ACL_READ)
132 dac_granted |= VREAD;
133 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
134 dac_granted |= (VWRITE | VAPPEND);
135 if ((accmode & dac_granted) == accmode)
139 * XXXRW: Do privilege lookup here.
141 if ((accmode & (dac_granted | priv_granted)) ==
148 acl_mask = &acl->acl_entry[i];
152 acl_other = &acl->acl_entry[i];
161 * An ACL_OTHER entry should always exist in a valid access ACL. If
162 * it doesn't, then generate a serious failure. For now, this means
163 * a debugging message and EPERM, but in the future should probably
166 if (acl_other == NULL) {
168 * XXX This should never happen
170 printf("vaccess_acl_posix1e: ACL_OTHER missing\n");
175 * Checks against ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP fields are
176 * masked by an ACL_MASK entry, if any. As such, first identify the
177 * ACL_MASK field, then iterate through identifying potential user
178 * matches, then group matches. If there is no ACL_MASK, assume that
179 * the mask allows all requests to succeed.
181 if (acl_mask != NULL) {
182 acl_mask_granted = 0;
183 if (acl_mask->ae_perm & ACL_EXECUTE)
184 acl_mask_granted |= VEXEC;
185 if (acl_mask->ae_perm & ACL_READ)
186 acl_mask_granted |= VREAD;
187 if (acl_mask->ae_perm & ACL_WRITE)
188 acl_mask_granted |= (VWRITE | VAPPEND);
190 acl_mask_granted = VEXEC | VREAD | VWRITE | VAPPEND;
193 * Check ACL_USER ACL entries. There will either be one or no
194 * matches; if there is one, we accept or rejected based on the
195 * match; otherwise, we continue on to groups.
197 for (i = 0; i < acl->acl_cnt; i++) {
198 switch (acl->acl_entry[i].ae_tag) {
200 if (acl->acl_entry[i].ae_id != cred->cr_uid)
203 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
204 dac_granted |= VEXEC;
205 if (acl->acl_entry[i].ae_perm & ACL_READ)
206 dac_granted |= VREAD;
207 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
208 dac_granted |= (VWRITE | VAPPEND);
209 dac_granted &= acl_mask_granted;
210 if ((accmode & dac_granted) == accmode)
213 * XXXRW: Do privilege lookup here.
215 if ((accmode & (dac_granted | priv_granted)) !=
224 * Group match is best-match, not first-match, so find a "best"
225 * match. Iterate across, testing each potential group match. Make
226 * sure we keep track of whether we found a match or not, so that we
227 * know if we should try again with any available privilege, or if we
228 * should move on to ACL_OTHER.
231 for (i = 0; i < acl->acl_cnt; i++) {
232 switch (acl->acl_entry[i].ae_tag) {
234 if (!groupmember(file_gid, cred))
237 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
238 dac_granted |= VEXEC;
239 if (acl->acl_entry[i].ae_perm & ACL_READ)
240 dac_granted |= VREAD;
241 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
242 dac_granted |= (VWRITE | VAPPEND);
243 dac_granted &= acl_mask_granted;
245 if ((accmode & dac_granted) == accmode)
252 if (!groupmember(acl->acl_entry[i].ae_id, cred))
255 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
256 dac_granted |= VEXEC;
257 if (acl->acl_entry[i].ae_perm & ACL_READ)
258 dac_granted |= VREAD;
259 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
260 dac_granted |= (VWRITE | VAPPEND);
261 dac_granted &= acl_mask_granted;
263 if ((accmode & dac_granted) == accmode)
274 if (group_matched == 1) {
276 * There was a match, but it did not grant rights via pure
277 * DAC. Try again, this time with privilege.
279 for (i = 0; i < acl->acl_cnt; i++) {
280 switch (acl->acl_entry[i].ae_tag) {
282 if (!groupmember(file_gid, cred))
285 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
286 dac_granted |= VEXEC;
287 if (acl->acl_entry[i].ae_perm & ACL_READ)
288 dac_granted |= VREAD;
289 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
290 dac_granted |= (VWRITE | VAPPEND);
291 dac_granted &= acl_mask_granted;
294 * XXXRW: Do privilege lookup here.
296 if ((accmode & (dac_granted | priv_granted))
303 if (!groupmember(acl->acl_entry[i].ae_id,
307 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
308 dac_granted |= VEXEC;
309 if (acl->acl_entry[i].ae_perm & ACL_READ)
310 dac_granted |= VREAD;
311 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
312 dac_granted |= (VWRITE | VAPPEND);
313 dac_granted &= acl_mask_granted;
316 * XXXRW: Do privilege lookup here.
318 if ((accmode & (dac_granted | priv_granted))
329 * Even with privilege, group membership was not sufficient.
336 * Fall back on ACL_OTHER. ACL_MASK is not applied to ACL_OTHER.
339 if (acl_other->ae_perm & ACL_EXECUTE)
340 dac_granted |= VEXEC;
341 if (acl_other->ae_perm & ACL_READ)
342 dac_granted |= VREAD;
343 if (acl_other->ae_perm & ACL_WRITE)
344 dac_granted |= (VWRITE | VAPPEND);
346 if ((accmode & dac_granted) == accmode)
349 * XXXRW: Do privilege lookup here.
351 if ((accmode & (dac_granted | priv_granted)) == accmode) {
356 return ((accmode & VADMIN) ? EPERM : EACCES);
360 * For the purposes of filesystems maintaining the _OBJ entries in an inode
361 * with a mode_t field, this routine converts a mode_t entry to an
365 acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode)
398 printf("acl_posix1e_mode_to_perm: invalid tag (%d)\n", tag);
404 * Given inode information (uid, gid, mode), return an acl entry of the
408 acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode)
410 struct acl_entry acl_entry;
412 acl_entry.ae_tag = tag;
413 acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode);
414 acl_entry.ae_entry_type = 0;
415 acl_entry.ae_flags = 0;
418 acl_entry.ae_id = uid;
422 acl_entry.ae_id = gid;
426 acl_entry.ae_id = ACL_UNDEFINED_ID;
430 acl_entry.ae_id = ACL_UNDEFINED_ID;
431 printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag);
438 * Utility function to generate a file mode given appropriate ACL entries.
441 acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry,
442 struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry)
447 if (acl_user_obj_entry->ae_perm & ACL_EXECUTE)
449 if (acl_user_obj_entry->ae_perm & ACL_READ)
451 if (acl_user_obj_entry->ae_perm & ACL_WRITE)
453 if (acl_group_obj_entry->ae_perm & ACL_EXECUTE)
455 if (acl_group_obj_entry->ae_perm & ACL_READ)
457 if (acl_group_obj_entry->ae_perm & ACL_WRITE)
459 if (acl_other_entry->ae_perm & ACL_EXECUTE)
461 if (acl_other_entry->ae_perm & ACL_READ)
463 if (acl_other_entry->ae_perm & ACL_WRITE)
470 * Utility function to generate a file mode given a complete POSIX.1e access
471 * ACL. Note that if the ACL is improperly formed, this may result in a
475 acl_posix1e_acl_to_mode(struct acl *acl)
477 struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other;
481 * Find the ACL entries relevant to a POSIX permission mode.
483 acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL;
484 for (i = 0; i < acl->acl_cnt; i++) {
485 switch (acl->acl_entry[i].ae_tag) {
487 acl_user_obj = &acl->acl_entry[i];
491 acl_group_obj = &acl->acl_entry[i];
495 acl_other = &acl->acl_entry[i];
499 acl_mask = &acl->acl_entry[i];
507 panic("acl_posix1e_acl_to_mode: bad ae_tag");
511 if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL)
512 panic("acl_posix1e_acl_to_mode: missing base ae_tags");
515 * POSIX.1e specifies that if there is an ACL_MASK entry, we replace
516 * the mode "group" bits with its permissions. If there isn't, we
517 * use the ACL_GROUP_OBJ permissions.
519 if (acl_mask != NULL)
520 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask,
523 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj,
528 * Perform a syntactic check of the ACL, sufficient to allow an implementing
529 * filesystem to determine if it should accept this and rely on the POSIX.1e
533 acl_posix1e_check(struct acl *acl)
535 int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group;
536 int num_acl_mask, num_acl_other, i;
539 * Verify that the number of entries does not exceed the maximum
542 * Verify that the correct number of various sorts of ae_tags are
544 * Exactly one ACL_USER_OBJ
545 * Exactly one ACL_GROUP_OBJ
546 * Exactly one ACL_OTHER
547 * If any ACL_USER or ACL_GROUP entries appear, then exactly one
548 * ACL_MASK entry must also appear.
550 * Verify that all ae_perm entries are in ACL_PERM_BITS.
552 * Verify all ae_tag entries are understood by this implementation.
554 * Note: Does not check for uniqueness of qualifier (ae_id) field.
556 num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group =
557 num_acl_mask = num_acl_other = 0;
558 if (acl->acl_cnt > ACL_MAX_ENTRIES)
560 for (i = 0; i < acl->acl_cnt; i++) {
562 * Check for a valid tag.
564 switch(acl->acl_entry[i].ae_tag) {
566 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
567 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
572 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
573 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
578 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
583 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
588 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
589 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
594 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
595 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
603 * Check for valid perm entries.
605 if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) !=
609 if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) ||
610 (num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1))
612 if (((num_acl_group != 0) || (num_acl_user != 0)) &&
619 * Given a requested mode for a new object, and a default ACL, combine the
620 * two to produce a new mode. Be careful not to clear any bits that aren't
621 * intended to be affected by the POSIX.1e ACL. Eventually, this might also
622 * take the cmask as an argument, if we push that down into
623 * per-filesystem-code.
626 acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl)
632 * The current composition policy is that a permission bit must be
633 * set in *both* the ACL and the requested creation mode for it to
634 * appear in the resulting mode/ACL. First clear any possibly
635 * effected bits, then reconstruct.
637 mode &= ACL_PRESERVE_MASK;
638 mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl));
644 acl_posix1e_modload(module_t mod, int what, void *arg)
672 static moduledata_t acl_posix1e_mod = {
678 DECLARE_MODULE(acl_posix1e, acl_posix1e_mod, SI_SUB_VFS, SI_ORDER_FIRST);
679 MODULE_VERSION(acl_posix1e, 1);