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 /* 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 switch(tag) { 413 case ACL_USER_OBJ: 414 acl_entry.ae_id = uid; 415 break; 416 417 case ACL_GROUP_OBJ: 418 acl_entry.ae_id = gid; 419 break; 420 421 case ACL_OTHER: 422 acl_entry.ae_id = ACL_UNDEFINED_ID; 423 break; 424 425 default: 426 acl_entry.ae_id = ACL_UNDEFINED_ID; 427 printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag); 428 } 429 430 return (acl_entry); 431 } 432 433 /* 434 * Utility function to generate a file mode given appropriate ACL entries. 435 */ 436 mode_t 437 acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry, 438 struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry) 439 { 440 mode_t mode; 441 442 mode = 0; 443 if (acl_user_obj_entry->ae_perm & ACL_EXECUTE) 444 mode |= S_IXUSR; 445 if (acl_user_obj_entry->ae_perm & ACL_READ) 446 mode |= S_IRUSR; 447 if (acl_user_obj_entry->ae_perm & ACL_WRITE) 448 mode |= S_IWUSR; 449 if (acl_group_obj_entry->ae_perm & ACL_EXECUTE) 450 mode |= S_IXGRP; 451 if (acl_group_obj_entry->ae_perm & ACL_READ) 452 mode |= S_IRGRP; 453 if (acl_group_obj_entry->ae_perm & ACL_WRITE) 454 mode |= S_IWGRP; 455 if (acl_other_entry->ae_perm & ACL_EXECUTE) 456 mode |= S_IXOTH; 457 if (acl_other_entry->ae_perm & ACL_READ) 458 mode |= S_IROTH; 459 if (acl_other_entry->ae_perm & ACL_WRITE) 460 mode |= S_IWOTH; 461 462 return (mode); 463 } 464 465 /* 466 * Utility function to generate a file mode given a complete POSIX.1e access 467 * ACL. Note that if the ACL is improperly formed, this may result in a 468 * panic. 469 */ 470 mode_t 471 acl_posix1e_acl_to_mode(struct acl *acl) 472 { 473 struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other; 474 int i; 475 476 /* 477 * Find the ACL entries relevant to a POSIX permission mode. 478 */ 479 acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL; 480 for (i = 0; i < acl->acl_cnt; i++) { 481 switch (acl->acl_entry[i].ae_tag) { 482 case ACL_USER_OBJ: 483 acl_user_obj = &acl->acl_entry[i]; 484 break; 485 486 case ACL_GROUP_OBJ: 487 acl_group_obj = &acl->acl_entry[i]; 488 break; 489 490 case ACL_OTHER: 491 acl_other = &acl->acl_entry[i]; 492 break; 493 494 case ACL_MASK: 495 acl_mask = &acl->acl_entry[i]; 496 break; 497 498 case ACL_USER: 499 case ACL_GROUP: 500 break; 501 502 default: 503 panic("acl_posix1e_acl_to_mode: bad ae_tag"); 504 } 505 } 506 507 if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL) 508 panic("acl_posix1e_acl_to_mode: missing base ae_tags"); 509 510 /* 511 * POSIX.1e specifies that if there is an ACL_MASK entry, we replace 512 * the mode "group" bits with its permissions. If there isn't, we 513 * use the ACL_GROUP_OBJ permissions. 514 */ 515 if (acl_mask != NULL) 516 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask, 517 acl_other)); 518 else 519 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj, 520 acl_other)); 521 } 522 523 /* 524 * Perform a syntactic check of the ACL, sufficient to allow an implementing 525 * filesystem to determine if it should accept this and rely on the POSIX.1e 526 * ACL properties. 527 */ 528 int 529 acl_posix1e_check(struct acl *acl) 530 { 531 int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group; 532 int num_acl_mask, num_acl_other, i; 533 534 /* 535 * Verify that the number of entries does not exceed the maximum 536 * defined for acl_t. 537 * 538 * Verify that the correct number of various sorts of ae_tags are 539 * present: 540 * Exactly one ACL_USER_OBJ 541 * Exactly one ACL_GROUP_OBJ 542 * Exactly one ACL_OTHER 543 * If any ACL_USER or ACL_GROUP entries appear, then exactly one 544 * ACL_MASK entry must also appear. 545 * 546 * Verify that all ae_perm entries are in ACL_PERM_BITS. 547 * 548 * Verify all ae_tag entries are understood by this implementation. 549 * 550 * Note: Does not check for uniqueness of qualifier (ae_id) field. 551 */ 552 num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group = 553 num_acl_mask = num_acl_other = 0; 554 if (acl->acl_cnt > ACL_MAX_ENTRIES || acl->acl_cnt < 0) 555 return (EINVAL); 556 for (i = 0; i < acl->acl_cnt; i++) { 557 /* 558 * Check for a valid tag. 559 */ 560 switch(acl->acl_entry[i].ae_tag) { 561 case ACL_USER_OBJ: 562 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ 563 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) 564 return (EINVAL); 565 num_acl_user_obj++; 566 break; 567 case ACL_GROUP_OBJ: 568 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ 569 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) 570 return (EINVAL); 571 num_acl_group_obj++; 572 break; 573 case ACL_USER: 574 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID) 575 return (EINVAL); 576 num_acl_user++; 577 break; 578 case ACL_GROUP: 579 if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID) 580 return (EINVAL); 581 num_acl_group++; 582 break; 583 case ACL_OTHER: 584 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ 585 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) 586 return (EINVAL); 587 num_acl_other++; 588 break; 589 case ACL_MASK: 590 acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ 591 if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) 592 return (EINVAL); 593 num_acl_mask++; 594 break; 595 default: 596 return (EINVAL); 597 } 598 /* 599 * Check for valid perm entries. 600 */ 601 if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) != 602 ACL_PERM_BITS) 603 return (EINVAL); 604 } 605 if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) || 606 (num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1)) 607 return (EINVAL); 608 if (((num_acl_group != 0) || (num_acl_user != 0)) && 609 (num_acl_mask != 1)) 610 return (EINVAL); 611 return (0); 612 } 613 614 /* 615 * Given a requested mode for a new object, and a default ACL, combine the 616 * two to produce a new mode. Be careful not to clear any bits that aren't 617 * intended to be affected by the POSIX.1e ACL. Eventually, this might also 618 * take the cmask as an argument, if we push that down into 619 * per-filesystem-code. 620 */ 621 mode_t 622 acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl) 623 { 624 mode_t mode; 625 626 mode = cmode; 627 /* 628 * The current composition policy is that a permission bit must be 629 * set in *both* the ACL and the requested creation mode for it to 630 * appear in the resulting mode/ACL. First clear any possibly 631 * effected bits, then reconstruct. 632 */ 633 mode &= ACL_PRESERVE_MASK; 634 mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl)); 635 636 return (mode); 637 } 638