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35 .Nd introduction to the POSIX.1e/NFSv4 ACL security API
43 permits file systems to export Access Control Lists via the VFS, and
44 provides a library for userland access to and manipulation of these ACLs.
46 supports POSIX.1e and NFSv4 ACLs, but
47 not all file systems provide support for ACLs, and some may require that
48 ACL support be explicitly enabled by the administrator.
49 The library calls include routines to allocate, duplicate, retrieve, set,
50 and validate ACLs associated with file objects.
51 As well as the POSIX.1e routines, there are a number of non-portable
52 extensions defined that allow for ACL semantics alternative to
53 POSIX.1e, such as NFSv4.
54 Where routines are non-standard, they are suffixed with _np to indicate that
55 they are not portable.
57 POSIX.1e describes a set of ACL manipulation routines to manage the
58 contents of ACLs, as well as their relationships with files; almost
59 all of these support routines are implemented in
62 Available functions, sorted by behavior, include:
63 .Bl -tag -width indent
64 .It Fn acl_add_flag_np
65 This function is described in
66 .Xr acl_add_flag_np 3 ,
67 and may be used to add flags to a flagset.
69 This function is described in
71 and may be used to add permissions to a permission set.
73 This function is described in
75 and may be used to calculate and set the permissions associated with
79 .It Fn acl_clear_flags_np
80 This function is described in
81 .Xr acl_clear_flags_np 3 ,
82 and may be used to clear all flags from a flagset.
83 .It Fn acl_clear_perms
84 This function is described in
85 .Xr acl_clear_perms 3 ,
86 and may be used to clear all permissions from a permission set.
88 This function is described in
89 .Xr acl_copy_entry 3 ,
90 and may be used to copy the contents of an ACL entry.
92 .Fn acl_create_entry ,
93 .Fn acl_create_entry_np
95 These functions are described in
96 .Xr acl_create_entry 3 ,
97 and may be used to create an empty entry in an ACL.
99 .Fn acl_delete_def_file ,
100 .Fn acl_delete_def_link_np ,
101 .Fn acl_delete_fd_np ,
102 .Fn acl_delete_file_np ,
103 .Fn acl_delete_link_np
105 These functions are described in
107 and may be used to delete ACLs from file system objects.
109 .Fn acl_delete_entry ,
110 .Fn acl_delete_entry_np ,
112 This functions are described in
113 .Xr acl_delete_entry 3 ,
114 and may be used to delete an entry from an ACL.
115 .It Fn acl_delete_flag_np
116 This function is described in
117 .Xr acl_delete_flag_np 3 ,
118 and may be used to delete flags from a flagset.
119 .It Fn acl_delete_perm
120 This function is described in
121 .Xr acl_delete_perm 3 ,
122 and may be used to delete permissions from a permset.
124 This function is described in
126 and may be used to duplicate an ACL structure.
128 This function is described in
130 and may be used to free userland working ACL storage.
132 This function is described in
133 .Xr acl_from_text 3 ,
134 and may be used to convert a text-form ACL into working ACL state, if
135 the ACL has POSIX.1e or NFSv4 semantics.
136 .It Fn acl_get_brand_np
137 This function is described in
138 .Xr acl_get_brand_np 3
139 and may be used to determine whether the ACL has POSIX.1e or NFSv4 semantics.
141 This function is described in
142 .Xr acl_get_entry 3 ,
143 and may be used to retrieve a designated ACL entry from an ACL.
150 These functions are described in
152 and may be used to retrieve ACLs from file system objects.
153 .It Fn acl_get_entry_type_np
154 This function is described in
155 .Xr acl_get_entry_type_np 3 ,
156 and may be used to retrieve an ACL type from an ACL entry.
157 .It Fn acl_get_flagset_np
158 This function is described in
159 .Xr acl_get_flagset_np 3 ,
160 and may be used to retrieve a flagset from an ACL entry.
161 .It Fn acl_get_permset
162 This function is described in
163 .Xr acl_get_permset 3 ,
164 and may be used to retrieve a permset from an ACL entry.
165 .It Fn acl_get_qualifier
166 This function is described in
167 .Xr acl_get_qualifier 3 ,
168 and may be used to retrieve the qualifier from an ACL entry.
169 .It Fn acl_get_tag_type
170 This function is described in
171 .Xr acl_get_tag_type 3 ,
172 and may be used to retrieve the tag type from an ACL entry.
174 This function is described in
176 and may be used to allocate a fresh (empty) ACL structure.
177 .It Fn acl_is_trivial_np
178 This function is described in
179 .Xr acl_is_trivial_np 3 ,
180 and may be used to find out whether ACL is trivial.
187 These functions are described in
189 and may be used to assign an ACL to a file system object.
190 .It Fn acl_set_entry_type_np
191 This function is described in
192 .Xr acl_set_entry_type_np 3 ,
193 and may be used to set the ACL type of an ACL entry.
194 .It Fn acl_set_flagset_np
195 This function is described in
196 .Xr acl_set_flagset_np 3 ,
197 and may be used to set the flags of an ACL entry from a flagset.
198 .It Fn acl_set_permset
199 This function is described in
200 .Xr acl_set_permset 3 ,
201 and may be used to set the permissions of an ACL entry from a permset.
202 .It Fn acl_set_qualifier
203 This function is described in
204 .Xr acl_set_qualifier 3 ,
205 and may be used to set the qualifier of an ACL.
206 .It Fn acl_set_tag_type
207 This function is described in
208 .Xr acl_set_tag_type 3 ,
209 and may be used to set the tag type of an ACL.
211 This function is described in
213 and may be used to remove extended entries from an ACL.
218 These functions are described in
220 and may be used to generate a text-form of a POSIX.1e or NFSv4 semantics ACL.
223 .Fn acl_valid_fd_np ,
224 .Fn acl_valid_file_np ,
225 .Fn acl_valid_link_np
227 These functions are described in
229 and may be used to validate an ACL as correct POSIX.1e-semantics, or
230 as appropriate for a particular file system object regardless of semantics.
233 Documentation of the internal kernel interfaces backing these calls may
236 The syscalls between the internal interfaces and the public library
237 routines may change over time, and as such are not documented.
238 They are not intended to be called directly without going through the
243 .Xr acl_add_flag_np 3 ,
245 .Xr acl_calc_mask 3 ,
246 .Xr acl_clear_flags_np 3 ,
247 .Xr acl_clear_perms 3 ,
248 .Xr acl_copy_entry 3 ,
249 .Xr acl_create_entry 3 ,
250 .Xr acl_delete_entry 3 ,
251 .Xr acl_delete_flag_np 3 ,
252 .Xr acl_delete_perm 3 ,
255 .Xr acl_from_text 3 ,
257 .Xr acl_get_brand_np 3 ,
258 .Xr acl_get_entry_type_np 3 ,
259 .Xr acl_get_flagset_np 3 ,
260 .Xr acl_get_permset 3 ,
261 .Xr acl_get_qualifier 3 ,
262 .Xr acl_get_tag_type 3 ,
264 .Xr acl_is_trivial_np 3 ,
266 .Xr acl_set_entry_type_np 3 ,
267 .Xr acl_set_flagset_np 3 ,
268 .Xr acl_set_permset 3 ,
269 .Xr acl_set_qualifier 3 ,
270 .Xr acl_set_tag_type 3 ,
277 POSIX.1e assigns security labels to all objects, extending the security
278 functionality described in POSIX.1.
279 These additional labels provide fine-grained discretionary access control,
280 fine-grained capabilities, and labels necessary for mandatory access
282 POSIX.2c describes a set of userland utilities for manipulating these
285 POSIX.1e is described in IEEE POSIX.1e draft 17.
286 Discussion of the draft continues on the cross-platform POSIX.1e
287 implementation mailing list.
288 To join this list, see the
290 POSIX.1e implementation page for more information.
292 POSIX.1e support was introduced in
295 was the first version to include a complete ACL implementation based
296 on extended attributes for the UFS and UFS2 file systems.
297 NFSv4 ACL support was introduced in
304 utilities describe the user tools that permit direct manipulation of complete
307 .An Robert N M Watson