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ACL(5)									ACL(5)

       acl - Access Control Lists

       Access control lists (ACLs) are discretionary access control mechanisms
       that grant and deny access to files and directories. Two different  ACL
       models  are supported in the Solaris release:POSIX-draft ACLs and NFSv4

       The older, POSIX-draft model is supported by the UFS file system.  This
       model  is  based	 on a withdrawn ACL POSIX specification that was never
       standardized. It was subsequently withdrawn by the POSIX committee.

       The other model is based on the standards of the	 NFSv4	working	 group
       and  is	an  approved standard from the Internet Engineering Task Force
       (IETF). The ZFS file system uses the NFSv4 model, and  provides	richer
       semantics  and  finer  grained  permission capabilities than the POSIX-
       draft model.

   POSIX-draft ACLs
       POSIX-draft ACLs provide an alternative	security  mechanism  to	 basic
       UNIX  file permissions in the Solaris release. Their purpose is to fur‐
       ther restrict access to files and directories or to extend  permissions
       to  a  particular  user. ACLs can be used to change the permissions for
       the standard owner, group and other class bits of a file's  mode.  ACLs
       can  give  additional  users and groups access to the file. A directory
       can also have a special kind of ACL called a default ACL, which defines
       ACL  entries  to	 be  inherited by descendents of the directory. POSIX-
       draft ACLs have an ACL entry called mask. The mask defines the  maximum
       permissions  that  can be granted to additional user and group entries.
       Whenever a file is created or  its  mode	 is  changed  by  chmod(1)  or
       chmod(2), the mask is recomputed. It is recomputed to be the group per‐
       mission defined in the mode passed to chmod(2).

       The POSIX-draft ACL model uses the standard rwx	model  of  traditional
       UNIX permissions.

       An ACL is represented as follows:


       Each  acl_entry	contains one ACL entry. An ACL entry is represented by
       two or three colon-separated(:) fields.

			    If uid blank, it represents the file owner.

			    If gid is blank, it represents the owning group.

			    Represents the file other class.

			    Defines the MAX permission to hand out.

       For example to give user joe read and write permissions, the ACL	 entry
       is specified as:


   NFSv4 ACLs
       NFSv4  ACL  model  is  based loosely on the Windows NT ACL model. NFSv4
       ACLs provide a much richer ACL model than POSIX-draft ACLs.

       The major differences between NFSv4 and POSIX-draft ACLs	 are  as  fol‐

	   o	  NFSv4	 ACLs  provide	finer grained permissions than the rwx

	   o	  NFSv4 ACLs allow for both ALLOW and DENY entries.

	   o	  NFSv4 ACLs provide a	rich  set  of  inheritance  semantics.
		  POSIX	 ACLs  also have inheritance, but with the NFSv4 model
		  you can control the following inheritance features:

	       o      Whether inheritance cascades to both files and  directo‐
		      ries or only to files or directories.

	       o      In  the  case  of	 directories, you can indicate whether
		      inheritance is applied to the directory itself, to  just
		      one  level  of subdirectories, or cascades to all subdi‐
		      rectories of the directory.

	   o	  NFSv4 ACLs provide a mechanism for hooking into  a  system's
		  audit trail.	Currently, Solaris does not support this mech‐

	   o	  NFSv4 ACLs enable adminstrators  to  specify	the  order  in
		  which	 ACL  entries  are  checked. With POSIX-draft ACLs the
		  file system reorders ACL entries into a well defined, strict
		  access, checking order.

       POSIX-draft  ACL	 semantics  can	 be achieved with NFSv4 ACLs. However,
       only some NFSv4 ACLs can be translated to equivalent POSIX-draft ACLs.

       Permissions can be specified in three different chmod ACL formats: ver‐
       bose, compact, or positional. The verbose format uses words to indicate
       that the permissions are separated with a forward slash (/)  character.
       Compact	format	uses the permission letters and positional format uses
       the permission letters or the hypen (-) to identify no permissions.

       The permissions for verbose mode and their abbreviated form  in	paren‐
       theses for compact and positional mode are described as follows:

       read_data (r)
			       Permission to read the data of the file

       list_directory (r)
			       Permission to list the contents of a directory.

       write_data (w)
			       Permission  to modify a file's data anywhere in
			       the file's  offset  range.  This	 includes  the
			       ability	to grow the file or write to any arbi‐
			       trary offset.

       add_file (w)
			       Permission to add a new file to a directory.

       append_data (p)
			       The ability to modify the file's data, but only
			       starting	 at EOF. Currently, this permission is
			       not supported.

       add_subdirectory (p)
			       Permission to create a subdirectory to a direc‐

       read_xattr (R)
			       The  ability to read the extended attributes of
			       a  file	or  do	a  lookup  in	the   extended
			       attributes directory.

       write_xattr (W)
			       The  ability  to	 create extended attributes or
			       write to the extended attributes directory.

       execute (x)
			       Permission to execute a file.

       read_attributes (a)
			       The ability to read basic attributes (non-ACLs)
			       of  a  file. Basic attributes are considered to
			       be the stat  level  attributes.	Allowing  this
			       access  mask bit means that the entity can exe‐
			       cute ls(1) and stat(2).

       write_attributes (A)
			       Permission to change the times associated  with
			       a file or directory to an arbitrary value.

       delete (d)
			       Permission to delete the file.

       delete_child (D)
			       Permission to delete a file within a directory.

       read_acl (c)
			       Permission to read the ACL.

       write_acl (C)
			       Permission  to  write the ACL or the ability to
			       execute chmod(1) or setfacl(1).

       write_owner (o)
			       Permission to change the owner or  the  ability
			       to execute chown(1) or chgrp(1).

       synchronize (s)
			       Permission  to  access  a  file	locally at the
			       server with synchronous reads and writes.  Cur‐
			       rently, this permission is not supported.

       The following inheritance flags are supported by NFSv4:

       file_inherit (f)
				 Inherit  to  all  newly  created  files  in a

       dir_inherit (d)
				 Inherit to all newly created directories in a

       inherit_only (i)
				 Placed	 on a directory, but does not apply to
				 the directory itself, only to	newly  created
				 created  files	 and  directories.  This  flag
				 requires file_inherit and or  dir_inherit  to
				 indicate what to inherit.

       no_propagate (n)
				 Placed	 on directories and indicates that ACL
				 entries should only be inherited one level of
				 the tree. This flag requires file_inherit and
				 or dir_inherit to indicate what to inherit.

       successful_access (S))
				 Indicates if an alarm or audit record	should
				 be  initiated	upon successful accesses. Used
				 with audit/alarm ACE types.

       failed_access (F)
				 Indicates if an alarm or audit record	should
				 be  initiated	when  access fails.  Used with
				 audit/alarm ACE types.

       inherited (I)
				 ACE was inherited.

				 No permission granted.

       An NFSv4 ACL is expressed using the following syntax:


	     owner@:<perms>[:inheritance flags]:<allow|deny>
	     group@:<perms>[:inheritance flags]:<allow|deny>
	     everyone@:<perms>[:inheritance flags]:<allow|deny>
	     user:<username>[:inheritance flags]:<allow|deny>
	     group:<groupname>[:inheritance flags]:<allow|deny>

		 File owner

		 Group owner

		 Permissions for a specific user

		 Permissions for a specific group

       Permission and inheritance flags are separated by a / character.

       ACL specification examples:


       Using the compact ACL format, permissions are  specified	 by  using  14
       unique letters to indicate permissions.

       Using  the  positional  ACL  format, permissions are specified as posi‐
       tional arguments similar to the ls -V format.  The  hyphen  (-),	 which
       indicates  that no permission is granted at that position, can be omit‐
       ted and only the required letters have to be specified.

       The letters above are listed in the order they would  be	 specified  in
       positional notation.

       With these letters you can specify permissions in the following equiva‐
       lent ways.


       Or you can remove the - and scrunch it together.


       The inheritance flags can also be specified in a more  compact  manner,
       as follows:


   Shell-level Solaris API
       The  Solaris  command  interface supports the manipulation of ACLs. The
       following Solaris utilities accommodate both ACL models:

		   The chmod utility has been enhanced to allow for  the  set‐
		   ting	 and  deleting	of ACLs. This is achieved by extending
		   the symbolic-mode argument to support ACL manipulation. See
		   chmod(1) for details.

		   When a file is compressed any ACL associated with the orig‐
		   inal file is preserved with the compressed file.

		   By default, cp ignores ACLs, unless the -p option is speci‐
		   fied.  When -p is specified the owner and group id, permis‐
		   sion	 modes,	 modification  and  access  times,  ACLs,  and
		   extended attributes if applicable are preserved.

		   ACLs are preserved when the -P option is specified.

		   Find	 locates  files with ACLs when the -acl flag is speci‐

		   By default ls does not display ACL information. When the -v
		   option is specified, a file's ACL is displayed.

		   When a file is moved, all attributes are carried along with
		   the renamed file.  When a file is moved across a file  sys‐
		   tem	boundary, the ACLs are replicated. If the ACL informa‐
		   tion cannot be replicated, the move fails  and  the	source
		   file is not removed.

		   When a file is packed, any ACL associated with the original
		   file is preserved with the packed file.

		   rcp has been enhanced to support copying. A file's  ACL  is
		   only preserved when the remote host supports ACLs.

		   ACLs are preserved when the -p option is specified.

		   When	 a  file  with	an  ACL is unpacked, the unpacked file
		   retains the ACL information.

   Application-level API
       The primary interfaces required to access file system ACLs at the  pro‐
       grammatic  level are the acl_get() and acl_set() functions. These func‐
       tions support both POSIX draft ACLs and NFSv4 ACLs.

   Retrieving a file's ACL
	 int acl_get(const char *path, int flag, acl_t **aclp);
	 int facl_get(int fd, int flag, acl_t **aclp);

       The acl_get(3SEC) and facl_get(3SEC) functions retrieves an  ACL	 on  a
       file  whose  name  is  given  by	 path  or  referenced by the open file
       descriptor fd. The flag argument specifies whether a trivial ACL should
       be  retrieved.  When  the flag argument equals ACL_NO_TRIVIAL then only
       ACLs that are not trivial are retrieved. The ACL	 is  returned  in  the
       aclp argument.

   Freeing ACL structure
	 void acl_free(acl_t *aclp)s;

       The  acl_free()	function  frees	 up  memory allocated for the argument

   Setting an ACL on a file
	 int acl_set(const char *path, acl_t *aclp);
	 int facl_set(int fd, acl_t *aclp);

       The acl_set(3SEC) and facl_get(3SEC) functions are used for setting  an
       ACL  on	a  file	 whose name is given by path or referenced by the open
       file descriptor fd. The aclp argument specifies the  ACL	 to  set.  The
       acl_set(3SEC)  translates  an POSIX-draft ACL into a NFSv4 ACL when the
       target file systems supports NFSv4 ACLs. No  translation	 is  performed
       when  trying  to	 set  an NFSv4 ACL on a POSIX-draft ACL supported file

   Determining an ACL's trivialness
	 int acl_trivial(const char *path);

       The acl_trivial() function is used to determine whether a  file	has  a
       trivial ACL. The trivialness of a file's ACL depends on the type of ACL
       it is.  For POSIX-draft ACLs, it	 implies  the  ACL  has	 greater  than
       MIN_ACL_ENTRIES.	 For NFSv4/ZFS style ACLs, it implies that the ACL has
       entries other than owner@, group@ and everyone@, inheritance flags  are
       set, or the ACL is not ordered in a manner that meets POSIX access con‐
       trol requirements.

   Removing all ACLs from a file
	 int acl_strip(const char *path, uid_t uid, gid_t gid, mode_t mode);

       The acl_strip() function removes all ACLs from a file and replaces them
       with  a	trivial	 ACL  based  off of the passed in argument mode. After
       replacing the ACL the owner and group of the file are set to the values
       specified in the uid and gid parameters.

   Converting ACLs to/from external representation
	 int acl_fromtext(const char *path, acl_t **aclp);
	 char *acl_totext(acl_t *aclp, int flags);

       The acl_text() function converts an internal ACL representation pointed
       to by aclp into an external representation. See DESCRIPTION for details
       about external representation.

       The  acl_fromtext() functions converts and external representation into
       an internal representation. See DESCRIPTION for details about  external

       The  following  examples demonstrate how the API can be used to perform
       basic operations on ACLs.

       Example 1 Retrieving and Setting an ACL

       Use the following to retrieve an ACL and set it on another file:

	 error = acl_get("file", ACL_NO_TRIVIAL, &aclp);

	 if (error == 0 && aclp != NULL) {
	 error = acl_set("file2", aclp)

       Example 2 Retrieving and Setting Any ACLs

       Use the following to retrieve any ACL, including trivial ACLs, and  set
       it on another file:

	 error = acl_get("file3", 0, &aclp);
	 if (error == 0) {
	 error = acl_set("file4", aclp)

       Example 3 Determining if a File has a Trivial ACL

       Use the following to determine if a file has a trivial ACL:

	 istrivial = acl_trivial("file")

	 if (istrivial == 0)
	 printf("file %s has a trivial ACL\n", file);
	 printf("file %s has a NON-trivial ACL\n", file);

       Example 4 Removing all ACLs from a File

       Use  the	 following to remove all ACLs from a file, and set a new mode,
       owner, and group:

	 error = acl_strip("file", 10, 100, 0644);

       chgrp(1), chmod(1), chown(1), cp(1), cpio(1),  find(1),	ls(1),	mv(1),
       tar(1),	   setfacl(1),	   chmod(2),	 acl(2),stat(2),acl_get(3SEC),
       aclsort(3SEC),  acl_fromtext(3SEC),  acl_free(3SEC),   acl_strip(3SEC),

				 Sep 10, 2013				ACL(5)

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