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("$FreeBSD$"); 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 KASSERT((accmode & ~(VEXEC | VWRITE | VREAD | VADMIN | VAPPEND)) == 0, 65 ("invalid bit in accmode")); 66 KASSERT((accmode & VAPPEND) == 0 || (accmode & VWRITE), 67 ("VAPPEND without VWRITE")); 68 69 /* 70 * Look for a normal, non-privileged way to access the file/directory 71 * as requested. If it exists, go with that. Otherwise, attempt to 72 * use privileges granted via priv_granted. In some cases, which 73 * privileges to use may be ambiguous due to "best match", in which 74 * case fall back on first match for the time being. 75 */ 76 if (privused != NULL) 77 *privused = 0; 78 79 /* 80 * Determine privileges now, but don't apply until we've found a DAC 81 * entry that matches but has failed to allow access. 82 * 83 * XXXRW: Ideally, we'd determine the privileges required before 84 * asking for them. 85 */ 86 priv_granted = 0; 87 88 if (type == VDIR) { 89 if ((accmode & VEXEC) && !priv_check_cred(cred, 90 PRIV_VFS_LOOKUP, 0)) 91 priv_granted |= VEXEC; 92 } else { 93 /* 94 * Ensure that at least one execute bit is on. Otherwise, 95 * a privileged user will always succeed, and we don't want 96 * this to happen unless the file really is executable. 97 */ 98 if ((accmode & VEXEC) && (acl_posix1e_acl_to_mode(acl) & 99 (S_IXUSR | S_IXGRP | S_IXOTH)) != 0 && 100 !priv_check_cred(cred, PRIV_VFS_EXEC, 0)) 101 priv_granted |= VEXEC; 102 } 103 104 if ((accmode & VREAD) && !priv_check_cred(cred, PRIV_VFS_READ, 0)) 105 priv_granted |= VREAD; 106 107 if (((accmode & VWRITE) || (accmode & VAPPEND)) && 108 !priv_check_cred(cred, PRIV_VFS_WRITE, 0)) 109 priv_granted |= (VWRITE | VAPPEND); 110 111 if ((accmode & VADMIN) && !priv_check_cred(cred, PRIV_VFS_ADMIN, 0)) 112 priv_granted |= VADMIN; 113 114 /* 115 * The owner matches if the effective uid associated with the 116 * credential matches that of the ACL_USER_OBJ entry. While we're 117 * doing the first scan, also cache the location of the ACL_MASK and 118 * ACL_OTHER entries, preventing some future iterations. 119 */ 120 acl_mask = acl_other = NULL; 121 for (i = 0; i < acl->acl_cnt; i++) { 122 switch (acl->acl_entry[i].ae_tag) { 123 case ACL_USER_OBJ: 124 if (file_uid != cred->cr_uid) 125 break; 126 dac_granted = 0; 127 dac_granted |= VADMIN; 128 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) 129 dac_granted |= VEXEC; 130 if (acl->acl_entry[i].ae_perm & ACL_READ) 131 dac_granted |= VREAD; 132 if (acl->acl_entry[i].ae_perm & ACL_WRITE) 133 dac_granted |= (VWRITE | VAPPEND); 134 if ((accmode & dac_granted) == accmode) 135 return (0); 136 137 /* 138 * XXXRW: Do privilege lookup here. 139 */ 140 if ((accmode & (dac_granted | priv_granted)) == 141 accmode) { 142 if (privused != NULL) 143 *privused = 1; 144 return (0); 145 } 146 goto error; 147 148 case ACL_MASK: 149 acl_mask = &acl->acl_entry[i]; 150 break; 151 152 case ACL_OTHER: 153 acl_other = &acl->acl_entry[i]; 154 break; 155 156 default: 157 break; 158 } 159 } 160 161 /* 162 * An ACL_OTHER entry should always exist in a valid access ACL. If 163 * it doesn't, then generate a serious failure. For now, this means 164 * a debugging message and EPERM, but in the future should probably 165 * be a panic. 166 */ 167 if (acl_other == NULL) { 168 /* 169 * XXX This should never happen 170 */ 171 printf("vaccess_acl_posix1e: ACL_OTHER missing\n"); 172 return (EPERM); 173 } 174 175 /* 176 * Checks against ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP fields are 177 * masked by an ACL_MASK entry, if any. As such, first identify the 178 * ACL_MASK field, then iterate through identifying potential user 179 * matches, then group matches. If there is no ACL_MASK, assume that 180 * the mask allows all requests to succeed. 181 */ 182 if (acl_mask != NULL) { 183 acl_mask_granted = 0; 184 if (acl_mask->ae_perm & ACL_EXECUTE) 185 acl_mask_granted |= VEXEC; 186 if (acl_mask->ae_perm & ACL_READ) 187 acl_mask_granted |= VREAD; 188 if (acl_mask->ae_perm & ACL_WRITE) 189 acl_mask_granted |= (VWRITE | VAPPEND); 190 } else 191 acl_mask_granted = VEXEC | VREAD | VWRITE | VAPPEND; 192 193 /* 194 * Check ACL_USER ACL entries. There will either be one or no 195 * matches; if there is one, we accept or rejected based on the 196 * match; otherwise, we continue on to groups. 197 */ 198 for (i = 0; i < acl->acl_cnt; i++) { 199 switch (acl->acl_entry[i].ae_tag) { 200 case ACL_USER: 201 if (acl->acl_entry[i].ae_id != cred->cr_uid) 202 break; 203 dac_granted = 0; 204 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) 205 dac_granted |= VEXEC; 206 if (acl->acl_entry[i].ae_perm & ACL_READ) 207 dac_granted |= VREAD; 208 if (acl->acl_entry[i].ae_perm & ACL_WRITE) 209 dac_granted |= (VWRITE | VAPPEND); 210 dac_granted &= acl_mask_granted; 211 if ((accmode & dac_granted) == accmode) 212 return (0); 213 /* 214 * XXXRW: Do privilege lookup here. 215 */ 216 if ((accmode & (dac_granted | priv_granted)) != 217 accmode) 218 goto error; 219 220 if (privused != NULL) 221 *privused = 1; 222 return (0); 223 } 224 } 225 226 /* 227 * Group match is best-match, not first-match, so find a "best" 228 * match. Iterate across, testing each potential group match. Make 229 * sure we keep track of whether we found a match or not, so that we 230 * know if we should try again with any available privilege, or if we 231 * should move on to ACL_OTHER. 232 */ 233 group_matched = 0; 234 for (i = 0; i < acl->acl_cnt; i++) { 235 switch (acl->acl_entry[i].ae_tag) { 236 case ACL_GROUP_OBJ: 237 if (!groupmember(file_gid, cred)) 238 break; 239 dac_granted = 0; 240 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) 241 dac_granted |= VEXEC; 242 if (acl->acl_entry[i].ae_perm & ACL_READ) 243 dac_granted |= VREAD; 244 if (acl->acl_entry[i].ae_perm & ACL_WRITE) 245 dac_granted |= (VWRITE | VAPPEND); 246 dac_granted &= acl_mask_granted; 247 248 if ((accmode & dac_granted) == accmode) 249 return (0); 250 251 group_matched = 1; 252 break; 253 254 case ACL_GROUP: 255 if (!groupmember(acl->acl_entry[i].ae_id, cred)) 256 break; 257 dac_granted = 0; 258 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) 259 dac_granted |= VEXEC; 260 if (acl->acl_entry[i].ae_perm & ACL_READ) 261 dac_granted |= VREAD; 262 if (acl->acl_entry[i].ae_perm & ACL_WRITE) 263 dac_granted |= (VWRITE | VAPPEND); 264 dac_granted &= acl_mask_granted; 265 266 if ((accmode & dac_granted) == accmode) 267 return (0); 268 269 group_matched = 1; 270 break; 271 272 default: 273 break; 274 } 275 } 276 277 if (group_matched == 1) { 278 /* 279 * There was a match, but it did not grant rights via pure 280 * DAC. Try again, this time with privilege. 281 */ 282 for (i = 0; i < acl->acl_cnt; i++) { 283 switch (acl->acl_entry[i].ae_tag) { 284 case ACL_GROUP_OBJ: 285 if (!groupmember(file_gid, cred)) 286 break; 287 dac_granted = 0; 288 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) 289 dac_granted |= VEXEC; 290 if (acl->acl_entry[i].ae_perm & ACL_READ) 291 dac_granted |= VREAD; 292 if (acl->acl_entry[i].ae_perm & ACL_WRITE) 293 dac_granted |= (VWRITE | VAPPEND); 294 dac_granted &= acl_mask_granted; 295 296 /* 297 * XXXRW: Do privilege lookup here. 298 */ 299 if ((accmode & (dac_granted | priv_granted)) 300 != accmode) 301 break; 302 303 if (privused != NULL) 304 *privused = 1; 305 return (0); 306 307 case ACL_GROUP: 308 if (!groupmember(acl->acl_entry[i].ae_id, 309 cred)) 310 break; 311 dac_granted = 0; 312 if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) 313 dac_granted |= VEXEC; 314 if (acl->acl_entry[i].ae_perm & ACL_READ) 315 dac_granted |= VREAD; 316 if (acl->acl_entry[i].ae_perm & ACL_WRITE) 317 dac_granted |= (VWRITE | VAPPEND); 318 dac_granted &= acl_mask_granted; 319 320 /* 321 * XXXRW: Do privilege lookup here. 322 */ 323 if ((accmode & (dac_granted | priv_granted)) 324 != accmode) 325 break; 326 327 if (privused != NULL) 328 *privused = 1; 329 return (0); 330 331 default: 332 break; 333 } 334 } 335 /* 336 * Even with privilege, group membership was not sufficient. 337 * Return failure. 338 */ 339 goto error; 340 } 341 342 /* 343 * Fall back on ACL_OTHER. ACL_MASK is not applied to ACL_OTHER. 344 */ 345 dac_granted = 0; 346 if (acl_other->ae_perm & ACL_EXECUTE) 347 dac_granted |= VEXEC; 348 if (acl_other->ae_perm & ACL_READ) 349 dac_granted |= VREAD; 350 if (acl_other->ae_perm & ACL_WRITE) 351 dac_granted |= (VWRITE | VAPPEND); 352 353 if ((accmode & dac_granted) == accmode) 354 return (0); 355 /* 356 * XXXRW: Do privilege lookup here. 357 */ 358 if ((accmode & (dac_granted | priv_granted)) == accmode) { 359 if (privused != NULL) 360 *privused = 1; 361 return (0); 362 } 363 364 error: 365 return ((accmode & VADMIN) ? EPERM : EACCES); 366 } 367 368 /* 369 * For the purposes of filesystems maintaining the _OBJ entries in an inode 370 * with a mode_t field, this routine converts a mode_t entry to an 371 * acl_perm_t. 372 */ 373 acl_perm_t 374 acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode) 375 { 376 acl_perm_t perm = 0; 377 378 switch(tag) { 379 case ACL_USER_OBJ: 380 if (mode & S_IXUSR) 381 perm |= ACL_EXECUTE; 382 if (mode & S_IRUSR) 383 perm |= ACL_READ; 384 if (mode & S_IWUSR) 385 perm |= ACL_WRITE; 386 return (perm); 387 388 case ACL_GROUP_OBJ: 389 if (mode & S_IXGRP) 390 perm |= ACL_EXECUTE; 391 if (mode & S_IRGRP) 392 perm |= ACL_READ; 393 if (mode & S_IWGRP) 394 perm |= ACL_WRITE; 395 return (perm); 396 397 case ACL_OTHER: 398 if (mode & S_IXOTH) 399 perm |= ACL_EXECUTE; 400 if (mode & S_IROTH) 401 perm |= ACL_READ; 402 if (mode & S_IWOTH) 403 perm |= ACL_WRITE; 404 return (perm); 405 406 default: 407 printf("acl_posix1e_mode_to_perm: invalid tag (%d)\n", tag); 408 return (0); 409 } 410 } 411 412 /* 413 * Given inode information (uid, gid, mode), return an acl entry of the 414 * appropriate type. 415 */ 416 struct acl_entry 417 acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode) 418 { 419 struct acl_entry acl_entry; 420 421 acl_entry.ae_tag = tag; 422 acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode); 423 acl_entry.ae_entry_type = 0; 424 acl_entry.ae_flags = 0; 425 switch(tag) { 426 case ACL_USER_OBJ: 427 acl_entry.ae_id = uid; 428 break; 429 430 case ACL_GROUP_OBJ: 431 acl_entry.ae_id = gid; 432 break; 433 434 case ACL_OTHER: 435 acl_entry.ae_id = ACL_UNDEFINED_ID; 436 break; 437 438 default: 439 acl_entry.ae_id = ACL_UNDEFINED_ID; 440 printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag); 441 } 442 443 return (acl_entry); 444 } 445 446 /* 447 * Utility function to generate a file mode given appropriate ACL entries. 448 */ 449 mode_t 450 acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry, 451 struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry) 452 { 453 mode_t mode; 454 455 mode = 0; 456 if (acl_user_obj_entry->ae_perm & ACL_EXECUTE) 457 mode |= S_IXUSR; 458 if (acl_user_obj_entry->ae_perm & ACL_READ) 459 mode |= S_IRUSR; 460 if (acl_user_obj_entry->ae_perm & ACL_WRITE) 461 mode |= S_IWUSR; 462 if (acl_group_obj_entry->ae_perm & ACL_EXECUTE) 463 mode |= S_IXGRP; 464 if (acl_group_obj_entry->ae_perm & ACL_READ) 465 mode |= S_IRGRP; 466 if (acl_group_obj_entry->ae_perm & ACL_WRITE) 467 mode |= S_IWGRP; 468 if (acl_other_entry->ae_perm & ACL_EXECUTE) 469 mode |= S_IXOTH; 470 if (acl_other_entry->ae_perm & ACL_READ) 471 mode |= S_IROTH; 472 if (acl_other_entry->ae_perm & ACL_WRITE) 473 mode |= S_IWOTH; 474 475 return (mode); 476 } 477 478 /* 479 * Utility function to generate a file mode given a complete POSIX.1e access 480 * ACL. Note that if the ACL is improperly formed, this may result in a 481 * panic. 482 */ 483 mode_t 484 acl_posix1e_acl_to_mode(struct acl *acl) 485 { 486 struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other; 487 int i; 488 489 /* 490 * Find the ACL entries relevant to a POSIX permission mode. 491 */ 492 acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL; 493 for (i = 0; i < acl->acl_cnt; i++) { 494 switch (acl->acl_entry[i].ae_tag) { 495 case ACL_USER_OBJ: 496 acl_user_obj = &acl->acl_entry[i]; 497 break; 498 499 case ACL_GROUP_OBJ: 500 acl_group_obj = &acl->acl_entry[i]; 501 break; 502 503 case ACL_OTHER: 504 acl_other = &acl->acl_entry[i]; 505 break; 506 507 case ACL_MASK: 508 acl_mask = &acl->acl_entry[i]; 509 break; 510 511 case ACL_USER: 512 case ACL_GROUP: 513 break; 514 515 default: 516 panic("acl_posix1e_acl_to_mode: bad ae_tag"); 517 } 518 } 519 520 if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL) 521 panic("acl_posix1e_acl_to_mode: missing base ae_tags"); 522 523 /* 524 * POSIX.1e specifies that if there is an ACL_MASK entry, we replace 525 * the mode "group" bits with its permissions. If there isn't, we 526 * use the ACL_GROUP_OBJ permissions. 527 */ 528 if (acl_mask != NULL) 529 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask, 530 acl_other)); 531 else 532 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj, 533 acl_other)); 534 } 535 536 /* 537 * Perform a syntactic check of the ACL, sufficient to allow an implementing 538 * filesystem to determine if it should accept this and rely on the POSIX.1e 539 * ACL properties. 540 */ 541 int 542 acl_posix1e_check(struct acl *acl) 543 { 544 int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group; 545 int num_acl_mask, num_acl_other, i; 546 547 /* 548 * Verify that the number of entries does not exceed the maximum 549 * defined for acl_t. 550 * 551 * Verify that the correct number of various sorts of ae_tags are 552 * present: 553 * Exactly one ACL_USER_OBJ 554 * Exactly one ACL_GROUP_OBJ 555 * Exactly one ACL_OTHER 556 * If any ACL_USER or ACL_GROUP entries appear, then exactly one 557 * ACL_MASK entry must also appear. 558 * 559 * Verify that all ae_perm entries are in ACL_PERM_BITS. 560 * 561 * Verify all ae_tag entries are understood by this implementation. 562 * 563 * Note: Does not check for uniqueness of qualifier (ae_id) field. 564 */ 565 num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group = 566 num_acl_mask = num_acl_other = 0; 567 if (acl->acl_cnt > ACL_MAX_ENTRIES) 568 return (EINVAL); 569 for (i = 0; i < acl->acl_cnt; i++) { 570 /* 571 * Check for a valid tag. 572 */ 573 switch(acl->acl_entry[i].ae_tag) { 574 case ACL_USER_OBJ: 575 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ 576 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) 577 return (EINVAL); 578 num_acl_user_obj++; 579 break; 580 case ACL_GROUP_OBJ: 581 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ 582 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) 583 return (EINVAL); 584 num_acl_group_obj++; 585 break; 586 case ACL_USER: 587 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID) 588 return (EINVAL); 589 num_acl_user++; 590 break; 591 case ACL_GROUP: 592 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID) 593 return (EINVAL); 594 num_acl_group++; 595 break; 596 case ACL_OTHER: 597 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ 598 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) 599 return (EINVAL); 600 num_acl_other++; 601 break; 602 case ACL_MASK: 603 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ 604 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) 605 return (EINVAL); 606 num_acl_mask++; 607 break; 608 default: 609 return (EINVAL); 610 } 611 /* 612 * Check for valid perm entries. 613 */ 614 if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) != 615 ACL_PERM_BITS) 616 return (EINVAL); 617 } 618 if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) || 619 (num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1)) 620 return (EINVAL); 621 if (((num_acl_group != 0) || (num_acl_user != 0)) && 622 (num_acl_mask != 1)) 623 return (EINVAL); 624 return (0); 625 } 626 627 /* 628 * Given a requested mode for a new object, and a default ACL, combine the 629 * two to produce a new mode. Be careful not to clear any bits that aren't 630 * intended to be affected by the POSIX.1e ACL. Eventually, this might also 631 * take the cmask as an argument, if we push that down into 632 * per-filesystem-code. 633 */ 634 mode_t 635 acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl) 636 { 637 mode_t mode; 638 639 mode = cmode; 640 /* 641 * The current composition policy is that a permission bit must be 642 * set in *both* the ACL and the requested creation mode for it to 643 * appear in the resulting mode/ACL. First clear any possibly 644 * effected bits, then reconstruct. 645 */ 646 mode &= ACL_PRESERVE_MASK; 647 mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl)); 648 649 return (mode); 650 } 651