2 * Copyright (c) 1999-2006 Robert N. M. Watson
5 * This software was developed by Robert Watson for the TrustedBSD Project.
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * Developed by the TrustedBSD Project.
31 * ACL support routines specific to POSIX.1e access control lists. These are
32 * utility routines for code common across file systems implementing POSIX.1e
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
39 #include <sys/param.h>
40 #include <sys/kernel.h>
41 #include <sys/module.h>
42 #include <sys/systm.h>
43 #include <sys/mount.h>
45 #include <sys/vnode.h>
46 #include <sys/errno.h>
51 * Implement a version of vaccess() that understands POSIX.1e ACL semantics;
52 * the access ACL has already been prepared for evaluation by the file system
53 * and is passed via 'uid', 'gid', and 'acl'. Return 0 on success, else an
57 vaccess_acl_posix1e(enum vtype type, uid_t file_uid, gid_t file_gid,
58 struct acl *acl, accmode_t accmode, struct ucred *cred, int *privused)
60 struct acl_entry *acl_other, *acl_mask;
61 accmode_t dac_granted;
62 accmode_t priv_granted;
63 accmode_t acl_mask_granted;
66 KASSERT((accmode & ~(VEXEC | VWRITE | VREAD | VADMIN | VAPPEND)) == 0,
67 ("invalid bit in accmode"));
68 KASSERT((accmode & VAPPEND) == 0 || (accmode & VWRITE),
69 ("VAPPEND without VWRITE"));
72 * Look for a normal, non-privileged way to access the file/directory
73 * as requested. If it exists, go with that. Otherwise, attempt to
74 * use privileges granted via priv_granted. In some cases, which
75 * privileges to use may be ambiguous due to "best match", in which
76 * 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,
93 priv_granted |= VEXEC;
96 * Ensure that at least one execute bit is on. Otherwise,
97 * a privileged user will always succeed, and we don't want
98 * this to happen unless the file really is executable.
100 if ((accmode & VEXEC) && (acl_posix1e_acl_to_mode(acl) &
101 (S_IXUSR | S_IXGRP | S_IXOTH)) != 0 &&
102 !priv_check_cred(cred, PRIV_VFS_EXEC, 0))
103 priv_granted |= VEXEC;
106 if ((accmode & VREAD) && !priv_check_cred(cred, PRIV_VFS_READ, 0))
107 priv_granted |= VREAD;
109 if (((accmode & VWRITE) || (accmode & VAPPEND)) &&
110 !priv_check_cred(cred, PRIV_VFS_WRITE, 0))
111 priv_granted |= (VWRITE | VAPPEND);
113 if ((accmode & VADMIN) && !priv_check_cred(cred, PRIV_VFS_ADMIN, 0))
114 priv_granted |= VADMIN;
117 * The owner matches if the effective uid associated with the
118 * credential matches that of the ACL_USER_OBJ entry. While we're
119 * doing the first scan, also cache the location of the ACL_MASK and
120 * ACL_OTHER entries, preventing some future iterations.
122 acl_mask = acl_other = NULL;
123 for (i = 0; i < acl->acl_cnt; i++) {
124 switch (acl->acl_entry[i].ae_tag) {
126 if (file_uid != cred->cr_uid)
129 dac_granted |= VADMIN;
130 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
131 dac_granted |= VEXEC;
132 if (acl->acl_entry[i].ae_perm & ACL_READ)
133 dac_granted |= VREAD;
134 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
135 dac_granted |= (VWRITE | VAPPEND);
136 if ((accmode & dac_granted) == accmode)
140 * XXXRW: Do privilege lookup here.
142 if ((accmode & (dac_granted | priv_granted)) ==
144 if (privused != NULL)
151 acl_mask = &acl->acl_entry[i];
155 acl_other = &acl->acl_entry[i];
164 * An ACL_OTHER entry should always exist in a valid access ACL. If
165 * it doesn't, then generate a serious failure. For now, this means
166 * a debugging message and EPERM, but in the future should probably
169 if (acl_other == NULL) {
171 * XXX This should never happen
173 printf("vaccess_acl_posix1e: ACL_OTHER missing\n");
178 * Checks against ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP fields are
179 * masked by an ACL_MASK entry, if any. As such, first identify the
180 * ACL_MASK field, then iterate through identifying potential user
181 * matches, then group matches. If there is no ACL_MASK, assume that
182 * the mask allows all requests to succeed.
184 if (acl_mask != NULL) {
185 acl_mask_granted = 0;
186 if (acl_mask->ae_perm & ACL_EXECUTE)
187 acl_mask_granted |= VEXEC;
188 if (acl_mask->ae_perm & ACL_READ)
189 acl_mask_granted |= VREAD;
190 if (acl_mask->ae_perm & ACL_WRITE)
191 acl_mask_granted |= (VWRITE | VAPPEND);
193 acl_mask_granted = VEXEC | VREAD | VWRITE | VAPPEND;
196 * Check ACL_USER ACL entries. There will either be one or no
197 * matches; if there is one, we accept or rejected based on the
198 * match; otherwise, we continue on to groups.
200 for (i = 0; i < acl->acl_cnt; i++) {
201 switch (acl->acl_entry[i].ae_tag) {
203 if (acl->acl_entry[i].ae_id != cred->cr_uid)
206 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
207 dac_granted |= VEXEC;
208 if (acl->acl_entry[i].ae_perm & ACL_READ)
209 dac_granted |= VREAD;
210 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
211 dac_granted |= (VWRITE | VAPPEND);
212 dac_granted &= acl_mask_granted;
213 if ((accmode & dac_granted) == accmode)
216 * XXXRW: Do privilege lookup here.
218 if ((accmode & (dac_granted | priv_granted)) !=
222 if (privused != NULL)
229 * Group match is best-match, not first-match, so find a "best"
230 * match. Iterate across, testing each potential group match. Make
231 * sure we keep track of whether we found a match or not, so that we
232 * know if we should try again with any available privilege, or if we
233 * should move on to ACL_OTHER.
236 for (i = 0; i < acl->acl_cnt; i++) {
237 switch (acl->acl_entry[i].ae_tag) {
239 if (!groupmember(file_gid, cred))
242 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
243 dac_granted |= VEXEC;
244 if (acl->acl_entry[i].ae_perm & ACL_READ)
245 dac_granted |= VREAD;
246 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
247 dac_granted |= (VWRITE | VAPPEND);
248 dac_granted &= acl_mask_granted;
250 if ((accmode & dac_granted) == accmode)
257 if (!groupmember(acl->acl_entry[i].ae_id, cred))
260 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
261 dac_granted |= VEXEC;
262 if (acl->acl_entry[i].ae_perm & ACL_READ)
263 dac_granted |= VREAD;
264 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
265 dac_granted |= (VWRITE | VAPPEND);
266 dac_granted &= acl_mask_granted;
268 if ((accmode & dac_granted) == accmode)
279 if (group_matched == 1) {
281 * There was a match, but it did not grant rights via pure
282 * DAC. Try again, this time with privilege.
284 for (i = 0; i < acl->acl_cnt; i++) {
285 switch (acl->acl_entry[i].ae_tag) {
287 if (!groupmember(file_gid, cred))
290 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
291 dac_granted |= VEXEC;
292 if (acl->acl_entry[i].ae_perm & ACL_READ)
293 dac_granted |= VREAD;
294 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
295 dac_granted |= (VWRITE | VAPPEND);
296 dac_granted &= acl_mask_granted;
299 * XXXRW: Do privilege lookup here.
301 if ((accmode & (dac_granted | priv_granted))
305 if (privused != NULL)
310 if (!groupmember(acl->acl_entry[i].ae_id,
314 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
315 dac_granted |= VEXEC;
316 if (acl->acl_entry[i].ae_perm & ACL_READ)
317 dac_granted |= VREAD;
318 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
319 dac_granted |= (VWRITE | VAPPEND);
320 dac_granted &= acl_mask_granted;
323 * XXXRW: Do privilege lookup here.
325 if ((accmode & (dac_granted | priv_granted))
329 if (privused != NULL)
338 * Even with privilege, group membership was not sufficient.
345 * Fall back on ACL_OTHER. ACL_MASK is not applied to ACL_OTHER.
348 if (acl_other->ae_perm & ACL_EXECUTE)
349 dac_granted |= VEXEC;
350 if (acl_other->ae_perm & ACL_READ)
351 dac_granted |= VREAD;
352 if (acl_other->ae_perm & ACL_WRITE)
353 dac_granted |= (VWRITE | VAPPEND);
355 if ((accmode & dac_granted) == accmode)
358 * XXXRW: Do privilege lookup here.
360 if ((accmode & (dac_granted | priv_granted)) == accmode) {
361 if (privused != NULL)
367 return ((accmode & VADMIN) ? EPERM : EACCES);
371 * For the purposes of filesystems maintaining the _OBJ entries in an inode
372 * with a mode_t field, this routine converts a mode_t entry to an
376 acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode)
409 printf("acl_posix1e_mode_to_perm: invalid tag (%d)\n", tag);
415 * Given inode information (uid, gid, mode), return an acl entry of the
419 acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode)
421 struct acl_entry acl_entry;
423 acl_entry.ae_tag = tag;
424 acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode);
425 acl_entry.ae_entry_type = 0;
426 acl_entry.ae_flags = 0;
429 acl_entry.ae_id = uid;
433 acl_entry.ae_id = gid;
437 acl_entry.ae_id = ACL_UNDEFINED_ID;
441 acl_entry.ae_id = ACL_UNDEFINED_ID;
442 printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag);
449 * Utility function to generate a file mode given appropriate ACL entries.
452 acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry,
453 struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry)
458 if (acl_user_obj_entry->ae_perm & ACL_EXECUTE)
460 if (acl_user_obj_entry->ae_perm & ACL_READ)
462 if (acl_user_obj_entry->ae_perm & ACL_WRITE)
464 if (acl_group_obj_entry->ae_perm & ACL_EXECUTE)
466 if (acl_group_obj_entry->ae_perm & ACL_READ)
468 if (acl_group_obj_entry->ae_perm & ACL_WRITE)
470 if (acl_other_entry->ae_perm & ACL_EXECUTE)
472 if (acl_other_entry->ae_perm & ACL_READ)
474 if (acl_other_entry->ae_perm & ACL_WRITE)
481 * Utility function to generate a file mode given a complete POSIX.1e access
482 * ACL. Note that if the ACL is improperly formed, this may result in a
486 acl_posix1e_acl_to_mode(struct acl *acl)
488 struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other;
492 * Find the ACL entries relevant to a POSIX permission mode.
494 acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL;
495 for (i = 0; i < acl->acl_cnt; i++) {
496 switch (acl->acl_entry[i].ae_tag) {
498 acl_user_obj = &acl->acl_entry[i];
502 acl_group_obj = &acl->acl_entry[i];
506 acl_other = &acl->acl_entry[i];
510 acl_mask = &acl->acl_entry[i];
518 panic("acl_posix1e_acl_to_mode: bad ae_tag");
522 if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL)
523 panic("acl_posix1e_acl_to_mode: missing base ae_tags");
526 * POSIX.1e specifies that if there is an ACL_MASK entry, we replace
527 * the mode "group" bits with its permissions. If there isn't, we
528 * use the ACL_GROUP_OBJ permissions.
530 if (acl_mask != NULL)
531 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask,
534 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj,
539 * Perform a syntactic check of the ACL, sufficient to allow an implementing
540 * filesystem to determine if it should accept this and rely on the POSIX.1e
544 acl_posix1e_check(struct acl *acl)
546 int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group;
547 int num_acl_mask, num_acl_other, i;
550 * Verify that the number of entries does not exceed the maximum
553 * Verify that the correct number of various sorts of ae_tags are
555 * Exactly one ACL_USER_OBJ
556 * Exactly one ACL_GROUP_OBJ
557 * Exactly one ACL_OTHER
558 * If any ACL_USER or ACL_GROUP entries appear, then exactly one
559 * ACL_MASK entry must also appear.
561 * Verify that all ae_perm entries are in ACL_PERM_BITS.
563 * Verify all ae_tag entries are understood by this implementation.
565 * Note: Does not check for uniqueness of qualifier (ae_id) field.
567 num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group =
568 num_acl_mask = num_acl_other = 0;
569 if (acl->acl_cnt > ACL_MAX_ENTRIES)
571 for (i = 0; i < acl->acl_cnt; i++) {
573 * Check for a valid tag.
575 switch(acl->acl_entry[i].ae_tag) {
577 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
578 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
583 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
584 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
589 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
594 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
599 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
600 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
605 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
606 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
614 * Check for valid perm entries.
616 if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) !=
620 if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) ||
621 (num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1))
623 if (((num_acl_group != 0) || (num_acl_user != 0)) &&
630 * Given a requested mode for a new object, and a default ACL, combine the
631 * two to produce a new mode. Be careful not to clear any bits that aren't
632 * intended to be affected by the POSIX.1e ACL. Eventually, this might also
633 * take the cmask as an argument, if we push that down into
634 * per-filesystem-code.
637 acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl)
643 * The current composition policy is that a permission bit must be
644 * set in *both* the ACL and the requested creation mode for it to
645 * appear in the resulting mode/ACL. First clear any possibly
646 * effected bits, then reconstruct.
648 mode &= ACL_PRESERVE_MASK;
649 mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl));
656 acl_posix1e_modload(module_t mod, int what, void *arg)
684 static moduledata_t acl_posix1e_mod = {
690 DECLARE_MODULE(acl_posix1e, acl_posix1e_mod, SI_SUB_VFS, SI_ORDER_FIRST);
691 MODULE_VERSION(acl_posix1e, 1);