1 /*-
2 * Copyright (c) 1999-2006 Robert N. M. Watson
3 * All rights reserved.
4 *
5 * This software was developed by Robert Watson for the TrustedBSD Project.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
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.
15 *
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
26 * SUCH DAMAGE.
27 */
28 /*
29 * Developed by the TrustedBSD Project.
30 *
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
33 * ACLs.
34 */
35
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD: releng/8.0/sys/kern/subr_acl_posix1e.c 192586 2009-05-22 15:56:43Z trasz $");
38
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/mount.h>
42 #include <sys/priv.h>
43 #include <sys/vnode.h>
44 #include <sys/errno.h>
45 #include <sys/stat.h>
46 #include <sys/acl.h>
47
48 /*
49 * Implement a version of vaccess() that understands POSIX.1e ACL semantics;
50 * the access ACL has already been prepared for evaluation by the file system
51 * and is passed via 'uid', 'gid', and 'acl'. Return 0 on success, else an
52 * errno value.
53 */
54 int
55 vaccess_acl_posix1e(enum vtype type, uid_t file_uid, gid_t file_gid,
56 struct acl *acl, accmode_t accmode, struct ucred *cred, int *privused)
57 {
58 struct acl_entry *acl_other, *acl_mask;
59 accmode_t dac_granted;
60 accmode_t priv_granted;
61 accmode_t acl_mask_granted;
62 int group_matched, i;
63
64 /*
65 * Look for a normal, non-privileged way to access the file/directory
66 * as requested. If it exists, go with that. Otherwise, attempt to
67 * use privileges granted via priv_granted. In some cases, which
68 * privileges to use may be ambiguous due to "best match", in which
69 * case fall back on first match for the time being.
70 */
71 if (privused != NULL)
72 *privused = 0;
73
74 /*
75 * Determine privileges now, but don't apply until we've found a DAC
76 * entry that matches but has failed to allow access.
77 *
78 * XXXRW: Ideally, we'd determine the privileges required before
79 * asking for them.
80 */
81 priv_granted = 0;
82
83 if (type == VDIR) {
84 if ((accmode & VEXEC) && !priv_check_cred(cred,
85 PRIV_VFS_LOOKUP, 0))
86 priv_granted |= VEXEC;
87 } else {
88 if ((accmode & VEXEC) && !priv_check_cred(cred,
89 PRIV_VFS_EXEC, 0))
90 priv_granted |= VEXEC;
91 }
92
93 if ((accmode & VREAD) && !priv_check_cred(cred, PRIV_VFS_READ, 0))
94 priv_granted |= VREAD;
95
96 if (((accmode & VWRITE) || (accmode & VAPPEND)) &&
97 !priv_check_cred(cred, PRIV_VFS_WRITE, 0))
98 priv_granted |= (VWRITE | VAPPEND);
99
100 if ((accmode & VADMIN) && !priv_check_cred(cred, PRIV_VFS_ADMIN, 0))
101 priv_granted |= VADMIN;
102
103 /*
104 * The owner matches if the effective uid associated with the
105 * credential matches that of the ACL_USER_OBJ entry. While we're
106 * doing the first scan, also cache the location of the ACL_MASK and
107 * ACL_OTHER entries, preventing some future iterations.
108 */
109 acl_mask = acl_other = NULL;
110 for (i = 0; i < acl->acl_cnt; i++) {
111 switch (acl->acl_entry[i].ae_tag) {
112 case ACL_USER_OBJ:
113 if (file_uid != cred->cr_uid)
114 break;
115 dac_granted = 0;
116 dac_granted |= VADMIN;
117 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
118 dac_granted |= VEXEC;
119 if (acl->acl_entry[i].ae_perm & ACL_READ)
120 dac_granted |= VREAD;
121 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
122 dac_granted |= (VWRITE | VAPPEND);
123 if ((accmode & dac_granted) == accmode)
124 return (0);
125
126 /*
127 * XXXRW: Do privilege lookup here.
128 */
129 if ((accmode & (dac_granted | priv_granted)) ==
130 accmode) {
131 if (privused != NULL)
132 *privused = 1;
133 return (0);
134 }
135 goto error;
136
137 case ACL_MASK:
138 acl_mask = &acl->acl_entry[i];
139 break;
140
141 case ACL_OTHER:
142 acl_other = &acl->acl_entry[i];
143 break;
144
145 default:
146 break;
147 }
148 }
149
150 /*
151 * An ACL_OTHER entry should always exist in a valid access ACL. If
152 * it doesn't, then generate a serious failure. For now, this means
153 * a debugging message and EPERM, but in the future should probably
154 * be a panic.
155 */
156 if (acl_other == NULL) {
157 /*
158 * XXX This should never happen
159 */
160 printf("vaccess_acl_posix1e: ACL_OTHER missing\n");
161 return (EPERM);
162 }
163
164 /*
165 * Checks against ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP fields are
166 * masked by an ACL_MASK entry, if any. As such, first identify the
167 * ACL_MASK field, then iterate through identifying potential user
168 * matches, then group matches. If there is no ACL_MASK, assume that
169 * the mask allows all requests to succeed.
170 */
171 if (acl_mask != NULL) {
172 acl_mask_granted = 0;
173 if (acl_mask->ae_perm & ACL_EXECUTE)
174 acl_mask_granted |= VEXEC;
175 if (acl_mask->ae_perm & ACL_READ)
176 acl_mask_granted |= VREAD;
177 if (acl_mask->ae_perm & ACL_WRITE)
178 acl_mask_granted |= (VWRITE | VAPPEND);
179 } else
180 acl_mask_granted = VEXEC | VREAD | VWRITE | VAPPEND;
181
182 /*
183 * Check ACL_USER ACL entries. There will either be one or no
184 * matches; if there is one, we accept or rejected based on the
185 * match; otherwise, we continue on to groups.
186 */
187 for (i = 0; i < acl->acl_cnt; i++) {
188 switch (acl->acl_entry[i].ae_tag) {
189 case ACL_USER:
190 if (acl->acl_entry[i].ae_id != cred->cr_uid)
191 break;
192 dac_granted = 0;
193 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
194 dac_granted |= VEXEC;
195 if (acl->acl_entry[i].ae_perm & ACL_READ)
196 dac_granted |= VREAD;
197 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
198 dac_granted |= (VWRITE | VAPPEND);
199 dac_granted &= acl_mask_granted;
200 if ((accmode & dac_granted) == accmode)
201 return (0);
202 /*
203 * XXXRW: Do privilege lookup here.
204 */
205 if ((accmode & (dac_granted | priv_granted)) !=
206 accmode)
207 goto error;
208
209 if (privused != NULL)
210 *privused = 1;
211 return (0);
212 }
213 }
214
215 /*
216 * Group match is best-match, not first-match, so find a "best"
217 * match. Iterate across, testing each potential group match. Make
218 * sure we keep track of whether we found a match or not, so that we
219 * know if we should try again with any available privilege, or if we
220 * should move on to ACL_OTHER.
221 */
222 group_matched = 0;
223 for (i = 0; i < acl->acl_cnt; i++) {
224 switch (acl->acl_entry[i].ae_tag) {
225 case ACL_GROUP_OBJ:
226 if (!groupmember(file_gid, cred))
227 break;
228 dac_granted = 0;
229 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
230 dac_granted |= VEXEC;
231 if (acl->acl_entry[i].ae_perm & ACL_READ)
232 dac_granted |= VREAD;
233 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
234 dac_granted |= (VWRITE | VAPPEND);
235 dac_granted &= acl_mask_granted;
236
237 if ((accmode & dac_granted) == accmode)
238 return (0);
239
240 group_matched = 1;
241 break;
242
243 case ACL_GROUP:
244 if (!groupmember(acl->acl_entry[i].ae_id, cred))
245 break;
246 dac_granted = 0;
247 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
248 dac_granted |= VEXEC;
249 if (acl->acl_entry[i].ae_perm & ACL_READ)
250 dac_granted |= VREAD;
251 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
252 dac_granted |= (VWRITE | VAPPEND);
253 dac_granted &= acl_mask_granted;
254
255 if ((accmode & dac_granted) == accmode)
256 return (0);
257
258 group_matched = 1;
259 break;
260
261 default:
262 break;
263 }
264 }
265
266 if (group_matched == 1) {
267 /*
268 * There was a match, but it did not grant rights via pure
269 * DAC. Try again, this time with privilege.
270 */
271 for (i = 0; i < acl->acl_cnt; i++) {
272 switch (acl->acl_entry[i].ae_tag) {
273 case ACL_GROUP_OBJ:
274 if (!groupmember(file_gid, cred))
275 break;
276 dac_granted = 0;
277 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
278 dac_granted |= VEXEC;
279 if (acl->acl_entry[i].ae_perm & ACL_READ)
280 dac_granted |= VREAD;
281 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
282 dac_granted |= (VWRITE | VAPPEND);
283 dac_granted &= acl_mask_granted;
284
285 /*
286 * XXXRW: Do privilege lookup here.
287 */
288 if ((accmode & (dac_granted | priv_granted))
289 != accmode)
290 break;
291
292 if (privused != NULL)
293 *privused = 1;
294 return (0);
295
296 case ACL_GROUP:
297 if (!groupmember(acl->acl_entry[i].ae_id,
298 cred))
299 break;
300 dac_granted = 0;
301 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE)
302 dac_granted |= VEXEC;
303 if (acl->acl_entry[i].ae_perm & ACL_READ)
304 dac_granted |= VREAD;
305 if (acl->acl_entry[i].ae_perm & ACL_WRITE)
306 dac_granted |= (VWRITE | VAPPEND);
307 dac_granted &= acl_mask_granted;
308
309 /*
310 * XXXRW: Do privilege lookup here.
311 */
312 if ((accmode & (dac_granted | priv_granted))
313 != accmode)
314 break;
315
316 if (privused != NULL)
317 *privused = 1;
318 return (0);
319
320 default:
321 break;
322 }
323 }
324 /*
325 * Even with privilege, group membership was not sufficient.
326 * Return failure.
327 */
328 goto error;
329 }
330
331 /*
332 * Fall back on ACL_OTHER. ACL_MASK is not applied to ACL_OTHER.
333 */
334 dac_granted = 0;
335 if (acl_other->ae_perm & ACL_EXECUTE)
336 dac_granted |= VEXEC;
337 if (acl_other->ae_perm & ACL_READ)
338 dac_granted |= VREAD;
339 if (acl_other->ae_perm & ACL_WRITE)
340 dac_granted |= (VWRITE | VAPPEND);
341
342 if ((accmode & dac_granted) == accmode)
343 return (0);
344 /*
345 * XXXRW: Do privilege lookup here.
346 */
347 if ((accmode & (dac_granted | priv_granted)) == accmode) {
348 if (privused != NULL)
349 *privused = 1;
350 return (0);
351 }
352
353 error:
354 return ((accmode & VADMIN) ? EPERM : EACCES);
355 }
356
357 /*
358 * For the purposes of filesystems maintaining the _OBJ entries in an inode
359 * with a mode_t field, this routine converts a mode_t entry to an
360 * acl_perm_t.
361 */
362 acl_perm_t
363 acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode)
364 {
365 acl_perm_t perm = 0;
366
367 switch(tag) {
368 case ACL_USER_OBJ:
369 if (mode & S_IXUSR)
370 perm |= ACL_EXECUTE;
371 if (mode & S_IRUSR)
372 perm |= ACL_READ;
373 if (mode & S_IWUSR)
374 perm |= ACL_WRITE;
375 return (perm);
376
377 case ACL_GROUP_OBJ:
378 if (mode & S_IXGRP)
379 perm |= ACL_EXECUTE;
380 if (mode & S_IRGRP)
381 perm |= ACL_READ;
382 if (mode & S_IWGRP)
383 perm |= ACL_WRITE;
384 return (perm);
385
386 case ACL_OTHER:
387 if (mode & S_IXOTH)
388 perm |= ACL_EXECUTE;
389 if (mode & S_IROTH)
390 perm |= ACL_READ;
391 if (mode & S_IWOTH)
392 perm |= ACL_WRITE;
393 return (perm);
394
395 default:
396 printf("acl_posix1e_mode_to_perm: invalid tag (%d)\n", tag);
397 return (0);
398 }
399 }
400
401 /*
402 * Given inode information (uid, gid, mode), return an acl entry of the
403 * appropriate type.
404 */
405 struct acl_entry
406 acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode)
407 {
408 struct acl_entry acl_entry;
409
410 acl_entry.ae_tag = tag;
411 acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode);
412 acl_entry.ae_entry_type = 0;
413 acl_entry.ae_flags = 0;
414 switch(tag) {
415 case ACL_USER_OBJ:
416 acl_entry.ae_id = uid;
417 break;
418
419 case ACL_GROUP_OBJ:
420 acl_entry.ae_id = gid;
421 break;
422
423 case ACL_OTHER:
424 acl_entry.ae_id = ACL_UNDEFINED_ID;
425 break;
426
427 default:
428 acl_entry.ae_id = ACL_UNDEFINED_ID;
429 printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag);
430 }
431
432 return (acl_entry);
433 }
434
435 /*
436 * Utility function to generate a file mode given appropriate ACL entries.
437 */
438 mode_t
439 acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry,
440 struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry)
441 {
442 mode_t mode;
443
444 mode = 0;
445 if (acl_user_obj_entry->ae_perm & ACL_EXECUTE)
446 mode |= S_IXUSR;
447 if (acl_user_obj_entry->ae_perm & ACL_READ)
448 mode |= S_IRUSR;
449 if (acl_user_obj_entry->ae_perm & ACL_WRITE)
450 mode |= S_IWUSR;
451 if (acl_group_obj_entry->ae_perm & ACL_EXECUTE)
452 mode |= S_IXGRP;
453 if (acl_group_obj_entry->ae_perm & ACL_READ)
454 mode |= S_IRGRP;
455 if (acl_group_obj_entry->ae_perm & ACL_WRITE)
456 mode |= S_IWGRP;
457 if (acl_other_entry->ae_perm & ACL_EXECUTE)
458 mode |= S_IXOTH;
459 if (acl_other_entry->ae_perm & ACL_READ)
460 mode |= S_IROTH;
461 if (acl_other_entry->ae_perm & ACL_WRITE)
462 mode |= S_IWOTH;
463
464 return (mode);
465 }
466
467 /*
468 * Utility function to generate a file mode given a complete POSIX.1e access
469 * ACL. Note that if the ACL is improperly formed, this may result in a
470 * panic.
471 */
472 mode_t
473 acl_posix1e_acl_to_mode(struct acl *acl)
474 {
475 struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other;
476 int i;
477
478 /*
479 * Find the ACL entries relevant to a POSIX permission mode.
480 */
481 acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL;
482 for (i = 0; i < acl->acl_cnt; i++) {
483 switch (acl->acl_entry[i].ae_tag) {
484 case ACL_USER_OBJ:
485 acl_user_obj = &acl->acl_entry[i];
486 break;
487
488 case ACL_GROUP_OBJ:
489 acl_group_obj = &acl->acl_entry[i];
490 break;
491
492 case ACL_OTHER:
493 acl_other = &acl->acl_entry[i];
494 break;
495
496 case ACL_MASK:
497 acl_mask = &acl->acl_entry[i];
498 break;
499
500 case ACL_USER:
501 case ACL_GROUP:
502 break;
503
504 default:
505 panic("acl_posix1e_acl_to_mode: bad ae_tag");
506 }
507 }
508
509 if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL)
510 panic("acl_posix1e_acl_to_mode: missing base ae_tags");
511
512 /*
513 * POSIX.1e specifies that if there is an ACL_MASK entry, we replace
514 * the mode "group" bits with its permissions. If there isn't, we
515 * use the ACL_GROUP_OBJ permissions.
516 */
517 if (acl_mask != NULL)
518 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask,
519 acl_other));
520 else
521 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj,
522 acl_other));
523 }
524
525 /*
526 * Perform a syntactic check of the ACL, sufficient to allow an implementing
527 * filesystem to determine if it should accept this and rely on the POSIX.1e
528 * ACL properties.
529 */
530 int
531 acl_posix1e_check(struct acl *acl)
532 {
533 int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group;
534 int num_acl_mask, num_acl_other, i;
535
536 /*
537 * Verify that the number of entries does not exceed the maximum
538 * defined for acl_t.
539 *
540 * Verify that the correct number of various sorts of ae_tags are
541 * present:
542 * Exactly one ACL_USER_OBJ
543 * Exactly one ACL_GROUP_OBJ
544 * Exactly one ACL_OTHER
545 * If any ACL_USER or ACL_GROUP entries appear, then exactly one
546 * ACL_MASK entry must also appear.
547 *
548 * Verify that all ae_perm entries are in ACL_PERM_BITS.
549 *
550 * Verify all ae_tag entries are understood by this implementation.
551 *
552 * Note: Does not check for uniqueness of qualifier (ae_id) field.
553 */
554 num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group =
555 num_acl_mask = num_acl_other = 0;
556 if (acl->acl_cnt > ACL_MAX_ENTRIES || acl->acl_cnt < 0)
557 return (EINVAL);
558 for (i = 0; i < acl->acl_cnt; i++) {
559 /*
560 * Check for a valid tag.
561 */
562 switch(acl->acl_entry[i].ae_tag) {
563 case ACL_USER_OBJ:
564 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
565 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
566 return (EINVAL);
567 num_acl_user_obj++;
568 break;
569 case ACL_GROUP_OBJ:
570 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
571 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
572 return (EINVAL);
573 num_acl_group_obj++;
574 break;
575 case ACL_USER:
576 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
577 return (EINVAL);
578 num_acl_user++;
579 break;
580 case ACL_GROUP:
581 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID)
582 return (EINVAL);
583 num_acl_group++;
584 break;
585 case ACL_OTHER:
586 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
587 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
588 return (EINVAL);
589 num_acl_other++;
590 break;
591 case ACL_MASK:
592 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */
593 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID)
594 return (EINVAL);
595 num_acl_mask++;
596 break;
597 default:
598 return (EINVAL);
599 }
600 /*
601 * Check for valid perm entries.
602 */
603 if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) !=
604 ACL_PERM_BITS)
605 return (EINVAL);
606 }
607 if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) ||
608 (num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1))
609 return (EINVAL);
610 if (((num_acl_group != 0) || (num_acl_user != 0)) &&
611 (num_acl_mask != 1))
612 return (EINVAL);
613 return (0);
614 }
615
616 /*
617 * Given a requested mode for a new object, and a default ACL, combine the
618 * two to produce a new mode. Be careful not to clear any bits that aren't
619 * intended to be affected by the POSIX.1e ACL. Eventually, this might also
620 * take the cmask as an argument, if we push that down into
621 * per-filesystem-code.
622 */
623 mode_t
624 acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl)
625 {
626 mode_t mode;
627
628 mode = cmode;
629 /*
630 * The current composition policy is that a permission bit must be
631 * set in *both* the ACL and the requested creation mode for it to
632 * appear in the resulting mode/ACL. First clear any possibly
633 * effected bits, then reconstruct.
634 */
635 mode &= ACL_PRESERVE_MASK;
636 mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl));
637
638 return (mode);
639 }
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