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If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner] 8 .TH ACL 5 "Feb 8, 2020" 9 .SH NAME 10 acl \- Access Control Lists 11 .SH DESCRIPTION 12 Access control lists (ACLs) are discretionary access control mechanisms that 13 grant and deny access to files and directories. Two different ACL models are 14 supported in this release: POSIX-draft ACLs and NFSv4 ACLs. 15 .sp 16 .LP 17 The older, POSIX-draft model is supported by the UFS file system. This model is 18 based on a withdrawn ACL POSIX specification that was never standardized. It 19 was subsequently withdrawn by the POSIX committee. 20 .sp 21 .LP 22 The other model is based on the standards of the NFSv4 working group and is an 23 approved standard from the Internet Engineering Task Force (IETF). The ZFS file 24 system uses the NFSv4 model, and provides richer semantics and finer grained 25 permission capabilities than the POSIX-draft model. 26 .SS "POSIX-draft ACLs" 27 POSIX-draft ACLs provide an alternative security mechanism to basic UNIX file 28 permissions. Their purpose is to further restrict access 29 to files and directories or to extend permissions to a particular user. ACLs 30 can be used to change the permissions for the standard owner, group and other 31 class bits of a file's mode. ACLs can give additional users and groups access 32 to the file. A directory can also have a special kind of ACL called a 33 \fBdefault\fR ACL, which defines ACL entries to be inherited by descendents of 34 the directory. POSIX-draft ACLs have an ACL entry called \fBmask\fR. The mask 35 defines the maximum permissions that can be granted to additional user and 36 group entries. Whenever a file is created or its mode is changed by 37 \fBchmod\fR(1) or \fBchmod\fR(2), the mask is recomputed. It is recomputed to 38 be the group permission defined in the mode passed to \fBchmod\fR(2). 39 .sp 40 .LP 41 The POSIX-draft ACL model uses the standard \fBrwx\fR model of traditional UNIX 42 permissions. 43 .sp 44 .LP 45 An ACL is represented as follows: 46 .sp 47 .in +2 48 .nf 49 \fIacl_entry\fR[,\fIacl_entry\fR]... 50 .fi 51 .in -2 52 .sp 53 54 .sp 55 .LP 56 Each \fIacl_entry\fR contains one ACL entry. An ACL entry is represented by two 57 or three colon-separated(\fB:\fR) fields. 58 .sp 59 .ne 2 60 .na 61 \fB\fIuser\fR:[\fIuid\fR]:\fIperms\fR\fR 62 .ad 63 .RS 21n 64 If \fIuid\fR blank, it represents the file owner. 65 .RE 66 67 .sp 68 .ne 2 69 .na 70 \fB\fIgroup\fR:[\fIgid\fR]:\fIperms\fR\fR 71 .ad 72 .RS 21n 73 If \fIgid\fR is blank, it represents the owning group. 74 .RE 75 76 .sp 77 .ne 2 78 .na 79 \fB\fIother\fR:\fIperms\fR\fR 80 .ad 81 .RS 21n 82 Represents the file other class. 83 .RE 84 85 .sp 86 .ne 2 87 .na 88 \fB\fImask\fR:\fIperms\fR\fR 89 .ad 90 .RS 21n 91 Defines the \fBMAX\fR permission to hand out. 92 .RE 93 94 .sp 95 .LP 96 For example to give user \fBjoe\fR read and write permissions, the ACL entry is 97 specified as: 98 .sp 99 .in +2 100 .nf 101 user:joe:rw- 102 .fi 103 .in -2 104 .sp 105 106 .SS "NFSv4 ACLs" 107 The NFSv4 ACL model is based loosely on the Windows NT ACL model. NFSv4 ACLs 108 provide a much richer ACL model than POSIX-draft ACLs. 109 .sp 110 .LP 111 The major differences between NFSv4 and POSIX-draft ACLs are as follows: 112 .RS +4 113 .TP 114 .ie t \(bu 115 .el o 116 NFSv4 ACLs provide finer grained permissions than the \fBrwx\fR model. 117 .RE 118 .RS +4 119 .TP 120 .ie t \(bu 121 .el o 122 NFSv4 ACLs allow for both \fBALLOW\fR and \fBDENY\fR entries. 123 .RE 124 .RS +4 125 .TP 126 .ie t \(bu 127 .el o 128 NFSv4 ACLs provide a rich set of inheritance semantics. POSIX ACLs also have 129 inheritance, but with the NFSv4 model you can control the following inheritance 130 features: 131 .RS +4 132 .TP 133 .ie t \(bu 134 .el o 135 Whether inheritance cascades to both files and directories or only to files or 136 directories. 137 .RE 138 .RS +4 139 .TP 140 .ie t \(bu 141 .el o 142 In the case of directories, you can indicate whether inheritance is applied to 143 the directory itself, to just one level of subdirectories, or cascades to all 144 subdirectories of the directory. 145 .RE 146 .RE 147 .RS +4 148 .TP 149 .ie t \(bu 150 .el o 151 NFSv4 ACLs provide a mechanism for hooking into a system's audit trail. 152 Currently, illumos does not support this mechanism. 153 .RE 154 .RS +4 155 .TP 156 .ie t \(bu 157 .el o 158 NFSv4 ACLs enable administrators to specify the order in which ACL entries are 159 checked. With POSIX-draft ACLs the file system reorders ACL entries into a well 160 defined, strict access, checking order. 161 .RE 162 .sp 163 .LP 164 POSIX-draft ACL semantics can be achieved with NFSv4 ACLs. However, only some 165 NFSv4 ACLs can be translated to equivalent POSIX-draft ACLs. 166 .sp 167 .LP 168 Permissions can be specified in three different \fBchmod\fR ACL formats: 169 verbose, compact, or positional. The verbose format uses words to indicate that 170 the permissions are separated with a forward slash (\fB/\fR) character. Compact 171 format uses the permission letters and positional format uses the permission 172 letters or the hyphen (\fB-\fR) to identify no permissions. 173 .sp 174 .LP 175 The permissions for verbose mode and their abbreviated form in parentheses for 176 compact and positional mode are described as follows: 177 .sp 178 .ne 2 179 .na 180 \fBread_data (\fBr\fR)\fR 181 .ad 182 .RS 24n 183 Permission to read the data of the file 184 .RE 185 186 .sp 187 .ne 2 188 .na 189 \fBlist_directory (\fBr\fR)\fR 190 .ad 191 .RS 24n 192 Permission to list the contents of a directory. 193 .RE 194 195 .sp 196 .ne 2 197 .na 198 \fBwrite_data (\fBw\fR)\fR 199 .ad 200 .RS 24n 201 Permission to modify a file's data anywhere in the file's offset range. This 202 includes the ability to grow the file or write to any arbitrary offset. 203 .RE 204 205 .sp 206 .ne 2 207 .na 208 \fBadd_file (\fBw\fR)\fR 209 .ad 210 .RS 24n 211 Permission to add a new file to a directory. 212 .RE 213 214 .sp 215 .ne 2 216 .na 217 \fBappend_data (\fBp\fR)\fR 218 .ad 219 .RS 24n 220 The ability to modify the file's data, but only starting at EOF. Currently, 221 this permission is not supported. 222 .RE 223 224 .sp 225 .ne 2 226 .na 227 \fBadd_subdirectory (\fBp\fR)\fR 228 .ad 229 .RS 24n 230 Permission to create a subdirectory to a directory. 231 .RE 232 233 .sp 234 .ne 2 235 .na 236 \fBread_xattr (\fBR\fR)\fR 237 .ad 238 .RS 24n 239 The ability to read the extended attributes of a file or do a lookup in the 240 extended attributes directory. 241 .RE 242 243 .sp 244 .ne 2 245 .na 246 \fBwrite_xattr (\fBW\fR)\fR 247 .ad 248 .RS 24n 249 The ability to create extended attributes or write to the extended attributes 250 directory. 251 .RE 252 253 .sp 254 .ne 2 255 .na 256 \fBexecute (\fBx\fR)\fR 257 .ad 258 .RS 24n 259 Permission to execute a file. 260 .RE 261 262 .sp 263 .ne 2 264 .na 265 \fBread_attributes (\fBa\fR)\fR 266 .ad 267 .RS 24n 268 The ability to read basic attributes (non-ACLs) of a file. Basic attributes are 269 considered to be the stat level attributes. Allowing this access mask bit means 270 that the entity can execute \fBls\fR(1) and \fBstat\fR(2). 271 .RE 272 273 .sp 274 .ne 2 275 .na 276 \fBwrite_attributes (\fBA\fR)\fR 277 .ad 278 .RS 24n 279 Permission to change the times associated with a file or directory to an 280 arbitrary value. 281 .RE 282 283 .sp 284 .ne 2 285 .na 286 \fBdelete (\fBd\fR)\fR 287 .ad 288 .RS 24n 289 Permission to delete the file. 290 .RE 291 292 .sp 293 .ne 2 294 .na 295 \fBdelete_child (\fBD\fR)\fR 296 .ad 297 .RS 24n 298 Permission to delete a file within a directory. 299 .RE 300 301 .sp 302 .ne 2 303 .na 304 \fBread_acl (\fBc\fR)\fR 305 .ad 306 .RS 24n 307 Permission to read the ACL. 308 .RE 309 310 .sp 311 .ne 2 312 .na 313 \fBwrite_acl (\fBC\fR)\fR 314 .ad 315 .RS 24n 316 Permission to write the ACL or the ability to execute \fBchmod\fR(1) or 317 \fBsetfacl\fR(1). 318 .RE 319 320 .sp 321 .ne 2 322 .na 323 \fBwrite_owner (\fBo\fR)\fR 324 .ad 325 .RS 24n 326 Permission to change the owner or the ability to execute \fBchown\fR(1) or 327 \fBchgrp\fR(1). 328 .RE 329 330 .sp 331 .ne 2 332 .na 333 \fBsynchronize (\fBs\fR)\fR 334 .ad 335 .RS 24n 336 Permission to access a file locally at the server with synchronous reads and 337 writes. Currently, this permission is not supported. 338 .RE 339 340 .sp 341 .LP 342 The following inheritance flags are supported by NFSv4 ACLs: 343 .sp 344 .ne 2 345 .na 346 \fBfile_inherit (\fBf\fR)\fR 347 .ad 348 .RS 26n 349 Inherit to all newly created files in a directory. 350 .RE 351 352 .sp 353 .ne 2 354 .na 355 \fBdir_inherit (\fBd\fR)\fR 356 .ad 357 .RS 26n 358 Inherit to all newly created directories in a directory. 359 .RE 360 361 .sp 362 .ne 2 363 .na 364 \fBinherit_only (\fBi\fR)\fR 365 .ad 366 .RS 26n 367 Placed on a directory, but does not apply to the directory itself, only to 368 newly created files and directories. This flag requires file_inherit 369 and/or dir_inherit to indicate what to inherit. 370 .RE 371 372 .sp 373 .ne 2 374 .na 375 \fBno_propagate (\fBn\fR)\fR 376 .ad 377 .RS 26n 378 Placed on directories and indicates that ACL entries should only be inherited 379 one level of the tree. This flag requires file_inherit and/or dir_inherit to 380 indicate what to inherit. 381 .RE 382 383 .sp 384 .ne 2 385 .na 386 \fBsuccessful_access (\fBS\fR)\fR 387 .ad 388 .RS 26n 389 Indicates whether an alarm or audit record should be initiated upon successful 390 accesses. Used with audit/alarm ACE types. 391 .RE 392 393 .sp 394 .ne 2 395 .na 396 \fBfailed_access (\fBF\fR)\fR 397 .ad 398 .RS 26n 399 Indicates whether an alarm or audit record should be initiated when access 400 fails. Used with audit/alarm ACE types. 401 .RE 402 403 .sp 404 .ne 2 405 .na 406 \fBinherited (\fBI\fR)\fR 407 .ad 408 .RS 26n 409 ACE was inherited. 410 .RE 411 412 .sp 413 .ne 2 414 .na 415 \fB\fB-\fR\fR 416 .ad 417 .RS 26n 418 No permission granted. 419 .RE 420 421 .sp 422 .LP 423 An NFSv4 ACL is expressed using the following syntax: 424 .sp 425 .in +2 426 .nf 427 \fIacl_entry\fR[,\fIacl_entry\fR]... 428 429 owner@:<perms>[:inheritance flags]:<allow|deny> 430 group@:<perms>[:inheritance flags]:<allow|deny> 431 everyone@:<perms>[:inheritance flags]:<allow|deny> 432 user:<username>:<perms>[:inheritance flags]:<allow|deny> 433 usersid:<sid string>:<perms>[:inheritance flags]:<allow|deny> 434 group:<groupname>:<perms>[:inheritance flags]:<allow|deny> 435 groupsid:<sid string>:<perms>[:inheritance flags]:<allow|deny> 436 sid:<sid string>:<perms>[:inheritance flags]:<allow|deny> 437 .fi 438 .in -2 439 440 .sp 441 .ne 2 442 .na 443 \fBowner@\fR 444 .ad 445 .RS 10n 446 File owner 447 .RE 448 449 .sp 450 .ne 2 451 .na 452 \fBgroup@\fR 453 .ad 454 .RS 10n 455 Group owner 456 .RE 457 458 .sp 459 .ne 2 460 .na 461 \fBuser\fR 462 .ad 463 .RS 10n 464 Permissions for a specific user 465 .RE 466 467 .sp 468 .ne 2 469 .na 470 \fBgroup\fR 471 .ad 472 .RS 10n 473 Permissions for a specific group 474 .RE 475 476 .sp 477 .LP 478 Permission and inheritance flags are separated by a \fB/\fR character. 479 .sp 480 .LP 481 ACL specification examples: 482 .sp 483 .in +2 484 .nf 485 user:fred:read_data/write_data/read_attributes:file_inherit:allow 486 owner@:read_data:allow,group@:read_data:allow,user:tom:read_data:deny 487 .fi 488 .in -2 489 .sp 490 491 .sp 492 .LP 493 Using the compact ACL format, permissions are specified by using 14 unique 494 letters to indicate permissions. 495 .sp 496 .LP 497 Using the positional ACL format, permissions are specified as positional 498 arguments similar to the \fBls -V\fR format. The hyphen (\fB-\fR), which 499 indicates that no permission is granted at that position, can be omitted and 500 only the required letters have to be specified. 501 .sp 502 .LP 503 The letters above are listed in the order they would be specified in positional 504 notation. 505 .sp 506 .LP 507 With these letters you can specify permissions in the following equivalent 508 ways. 509 .sp 510 .in +2 511 .nf 512 user:fred:rw------R------:file_inherit:allow 513 .fi 514 .in -2 515 .sp 516 517 .sp 518 .LP 519 Or you can remove the \fB-\fR and scrunch it together. 520 .sp 521 .in +2 522 .nf 523 user:fred:rwR:file_inherit:allow 524 .fi 525 .in -2 526 .sp 527 528 .sp 529 .LP 530 The inheritance flags can also be specified in a more compact manner, as 531 follows: 532 .sp 533 .in +2 534 .nf 535 user:fred:rwR:f:allow 536 user:fred:rwR:f------:allow 537 .fi 538 .in -2 539 .sp 540 541 .SS "Shell-level API" 542 Several utilities support the manipulation of ACLs. The following 543 utilities accommodate both ACL models: 544 .sp 545 .ne 2 546 .na 547 \fB\fBchmod\fR\fR 548 .ad 549 .RS 12n 550 The \fBchmod\fR utility has been enhanced to allow for the setting and deleting 551 of ACLs. This is achieved by extending the symbolic-mode argument to support 552 ACL manipulation. See \fBchmod\fR(1) for details. 553 .RE 554 555 .sp 556 .ne 2 557 .na 558 \fB\fBcompress\fR\fR 559 .ad 560 .RS 12n 561 When a file is compressed any ACL associated with the original file is 562 preserved with the compressed file. 563 .RE 564 565 .sp 566 .ne 2 567 .na 568 \fB\fBcp\fR\fR 569 .ad 570 .RS 12n 571 By default, \fBcp\fR ignores ACLs, unless the \fB-p\fR option is specified. 572 When \fB-p\fR is specified the owner and group id, permission modes, 573 modification and access times, ACLs, and extended attributes if applicable are 574 preserved. 575 .RE 576 577 .sp 578 .ne 2 579 .na 580 \fB\fBcpio\fR\fR 581 .ad 582 .RS 12n 583 ACLs are preserved when the \fB-P\fR option is specified. 584 .RE 585 586 .sp 587 .ne 2 588 .na 589 \fB\fBfind\fR\fR 590 .ad 591 .RS 12n 592 Find locates files with ACLs when the \fB-acl\fR flag is specified. 593 .RE 594 595 .sp 596 .ne 2 597 .na 598 \fB\fBls\fR\fR 599 .ad 600 .RS 12n 601 By default \fBls\fR does not display ACL information. When the \fB-v\fR option 602 is specified, a file's ACL is displayed. 603 .RE 604 605 .sp 606 .ne 2 607 .na 608 \fB\fBmv\fR\fR 609 .ad 610 .RS 12n 611 When a file is moved, all attributes are carried along with the renamed file. 612 When a file is moved across a file system boundary, the ACLs are replicated. If 613 the ACL information cannot be replicated, the move fails and the source file is 614 not removed. 615 .RE 616 617 .sp 618 .ne 2 619 .na 620 \fB\fBpack\fR\fR 621 .ad 622 .RS 12n 623 When a file is packed, any ACL associated with the original file is preserved 624 with the packed file. 625 .RE 626 627 .sp 628 .ne 2 629 .na 630 \fB\fBrcp\fR\fR 631 .ad 632 .RS 12n 633 \fBrcp\fR has been enhanced to support copying. A file's ACL is only preserved 634 when the remote host supports ACLs. 635 .RE 636 637 .sp 638 .ne 2 639 .na 640 \fB\fBtar\fR\fR 641 .ad 642 .RS 12n 643 ACLs are preserved when the \fB-p\fR option is specified. 644 .RE 645 646 .sp 647 .ne 2 648 .na 649 \fB\fBunpack\fR\fR 650 .ad 651 .RS 12n 652 When a file with an ACL is unpacked, the unpacked file retains the ACL 653 information. 654 .RE 655 656 .SS "Application-level API" 657 The primary interfaces required to access file system ACLs at the programmatic 658 level are the \fBacl_get()\fR and \fBacl_set()\fR functions. These functions 659 support both POSIX-draft ACLs and NFSv4 ACLs. 660 .SS "Retrieving a file's ACL" 661 .in +2 662 .nf 663 int acl_get(const char *path, int flag, acl_t **aclp); 664 int facl_get(int fd, int flag, acl_t **aclp); 665 .fi 666 .in -2 667 668 .sp 669 .LP 670 The \fBacl_get\fR(3SEC) and \fBfacl_get\fR(3SEC) functions retrieve an ACL on 671 a file whose name is given by path or referenced by the open file descriptor 672 fd. The flag argument specifies whether a trivial ACL should be retrieved. When 673 the flag argument equals \fBACL_NO_TRIVIAL\fR only ACLs that are not 674 trivial are retrieved. The ACL is returned in the \fBaclp\fR argument. 675 .SS "Freeing ACL structure" 676 .in +2 677 .nf 678 void acl_free(acl_t *aclp); 679 .fi 680 .in -2 681 682 .sp 683 .LP 684 The \fBacl_free()\fR function frees up memory allocated for the argument 685 \fBaclp\fR. 686 .SS "Setting an ACL on a file" 687 .in +2 688 .nf 689 int acl_set(const char *path, acl_t *aclp); 690 int facl_set(int fd, acl_t *aclp); 691 .fi 692 .in -2 693 694 .sp 695 .LP 696 The \fBacl_set\fR(3SEC) and \fBfacl_get\fR(3SEC) functions are used for setting 697 an ACL on a file whose name is given by path or referenced by the open file 698 descriptor \fBfd\fR. The \fBaclp\fR argument specifies the ACL to set. The 699 \fBacl_set\fR(3SEC) function translates a POSIX-draft ACL into a NFSv4 ACL when 700 the target file system supports NFSv4 ACLs. No translation is performed when 701 trying to set an NFSv4 ACL on a POSIX-draft ACL supported file system. 702 .SS "Determining an ACL's trivialness" 703 .in +2 704 .nf 705 int acl_trivial(const char *path); 706 .fi 707 .in -2 708 709 .sp 710 .LP 711 The \fBacl_trivial()\fR function is used to determine whether a file has a 712 trivial ACL. 713 .SS "Removing all ACLs from a file" 714 .in +2 715 .nf 716 int acl_strip(const char *path, uid_t uid, gid_t gid, mode_t mode); 717 .fi 718 .in -2 719 720 .sp 721 .LP 722 The \fBacl_strip()\fR function removes all ACLs from a file and replaces them 723 with a trivial ACL based off of the passed in argument mode. After replacing 724 the ACL the owner and group of the file are set to the values specified in the 725 uid and gid parameters. 726 .SS "Converting ACLs to/from external representation" 727 .in +2 728 .nf 729 int acl_fromtext(const char *path, acl_t **aclp); 730 char *acl_totext(acl_t *aclp, int flags); 731 .fi 732 .in -2 733 734 .sp 735 .LP 736 The \fBacl_totext()\fR function converts an internal ACL representation pointed 737 to by aclp into an external representation. See \fBDESCRIPTION\fR for details 738 about external representation. 739 .sp 740 .LP 741 The \fBacl_fromtext()\fR function converts an external representation into an 742 internal representation. See \fBDESCRIPTION\fR for details about external 743 representation. 744 .SH EXAMPLES 745 The following examples demonstrate how the API can be used to perform basic 746 operations on ACLs. 747 .LP 748 \fBExample 1 \fRRetrieving and Setting an ACL 749 .sp 750 .LP 751 Use the following to retrieve an ACL and set it on another file: 752 753 .sp 754 .in +2 755 .nf 756 error = acl_get("file", ACL_NO_TRIVIAL, &aclp); 757 758 if (error == 0 && aclp != NULL) { 759 .in +8 760 error = acl_set("file2", aclp); 761 acl_free(aclp); 762 .in -8 763 } 764 \&... 765 .fi 766 .in -2 767 768 .LP 769 \fBExample 2 \fRRetrieving and Setting Any ACLs 770 .sp 771 .LP 772 Use the following to retrieve any ACL, including trivial ACLs, and set it on 773 another file: 774 775 .sp 776 .in +2 777 .nf 778 error = acl_get("file3", 0, &aclp); 779 if (error == 0) { 780 .in +8 781 error = acl_set("file4", aclp); 782 acl_free(aclp); 783 .in -8 784 } 785 \&... 786 .fi 787 .in -2 788 789 .LP 790 \fBExample 3 \fRDetermining if a File has a Trivial ACL 791 .sp 792 .LP 793 Use the following to determine if a file has a trivial ACL: 794 795 .sp 796 .in +2 797 .nf 798 char *file = "file5"; 799 istrivial = acl_trivial(file); 800 801 if (istrivial == 0) 802 .in +8 803 printf("file %s has a trivial ACL\en", file); 804 .in -8 805 else 806 .in +8 807 printf("file %s has a NON-trivial ACL\en", file); 808 .in -8 809 \&... 810 .fi 811 .in -2 812 813 .LP 814 \fBExample 4 \fRRemoving all ACLs from a File 815 .sp 816 .LP 817 Use the following to remove all ACLs from a file, and set a new mode, owner, 818 and group: 819 820 .sp 821 .in +2 822 .nf 823 error = acl_strip("file", 10, 100, 0644); 824 \&... 825 .fi 826 .in -2 827 828 .SH SEE ALSO 829 \fBchgrp\fR(1), \fBchmod\fR(1), \fBchown\fR(1), \fBcp\fR(1), \fBcpio\fR(1), 830 \fBfind\fR(1), \fBls\fR(1), \fBmv\fR(1), \fBtar\fR(1), \fBsetfacl\fR(1), 831 \fBchmod\fR(2), \fBacl\fR(2), \fBstat\fR(2), \fBacl_get\fR(3SEC), 832 \fBaclsort\fR(3SEC), \fBacl_fromtext\fR(3SEC), \fBacl_free\fR(3SEC), 833 \fBacl_strip\fR(3SEC), \fBacl_trivial\fR(3SEC)