.\"-
.\" Copyright (c) 2000 Robert N. M. Watson
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.\" $FreeBSD: src/lib/libposix1e/acl.3,v 1.2.2.5 2001/12/20 16:27:06 ru Exp $
.\" $DragonFly: src/lib/libposix1e/acl.3,v 1.6 2006/08/19 01:36:39 swildner Exp $
.\"
.Dd January 28, 2000
.Dt ACL 3
.Os
.Sh NAME
.Nm acl
.Nd introduction to the POSIX.1e ACL security API
.Sh LIBRARY
.Lb libposix1e
.Sh SYNOPSIS
.In sys/types.h
.In sys/acl.h
.Sh DESCRIPTION
As shipped,
.Dx
permits file systems to export
Access Control Lists via the VFS, and provides a library for userland
access to and manipulation of these ACLs, but support for ACLs is not
provided by any file systems shipped in the base operating system.
The library calls shipped with 4.0 include routines to allocate,
duplicate, retrieve, set, and validate ACLs associated with file objects.
As well as the POSIX.1e routines, there are a number of non-portable
extensions defined that allow for alternative ACL semantics than the
POSIX.1e semantics, such as AFS, NTFS, and NWFS semantics.  Where
routines are non-standard, they are suffixed with _np to indicate that
they are not portable.
.Pp
POSIX.1e describes a set of ACL manipulation routines to manage the
contents of ACLs, as well as their relationships with files.  This
manipulation library is not currently implemented in
.Dx ,
although
a third party library was under development at the time this document
was written.  There is a general consensus that the POSIX.1e manipulation
routines are ambiguously defined in the specification, and don't meet the
needs of most applications.  For the time being, applications may
directly manipulate the ACL structures, defined in
.In sys/acl.h ,
although the
recommended usage is to only ever handle text-form ACLs in applications,
generated and maintained using
.Fn acl_from_text
and
.Fn acl_to_text ,
passed directly to and from the management routines.  In this manner,
an application can remain safely unaware of the contents of ACLs.
.Pp
Available functions, sorted by behavior, include:
.Pp
.Fn acl_delete_def_file ,
.Fn acl_delete_file_np ,
.Fn acl_delete_fd_np
.Pp
These functions are described in
.Xr acl_delete 3 ,
and may be used to delete ACLs from file system objects.
.Pp
.Fn acl_free
.Pp
This function is described in
.Xr acl_free 3 ,
and may be used to free userland working ACL storage.
.Pp
.Fn acl_from_text
.Pp
This function is described in
.Xr acl_from_text 3 ,
and may be used to convert a text-form ACL into working ACL state, if
the ACL has POSIX.1e semantics.
.Pp
.Fn acl_get_file ,
.Fn acl_get_fd ,
.Fn acl_get_fd_np
.Pp
These functions are described in
.Xr acl_get 3 ,
and may be used to retrieve ACLs from file system objects.
.Pp
.Fn acl_init
.Pp
This function is described in
.Xr acl_init 3 ,
and may be used to allocate a fresh (empty) ACL structure.
.Pp
.Fn acl_dup
.Pp
This function is described in
.Xr acl_dup 3 ,
and may be used to duplicate an ACL structure.
.Pp
.Fn acl_set_file ,
.Fn acl_set_fd ,
.Fn acl_set_fd_np
.Pp
These functions are described in
.Xr acl_set 3 ,
and may be used to assign an ACL to a file system object.
.Pp
.Fn acl_to_text
.Pp
This function is described in
.Xr acl_to_text 3 ,
and may be used to generate a text-form of a POSIX.1e semantics ACL.
.Pp
.Fn acl_valid ,
.Fn acl_valid_file_np ,
.Fn acl_valid_fd_np
.Pp
Thee functions are described in
.Xr acl_valid 3 ,
and may be used to validate an ACL as correct POSIX.1e-semantics, or
as appropriate for a particular file system object regardless of semantics.
.Pp
Documentation of the internal kernel interfaces backing these calls may
be found in
.Xr acl 9 .
The syscalls between the internal interfaces and the public library
routines may change over time, and as such are not documented.  They are
not intended to be called directly without going through the library.
.Sh IMPLEMENTATION NOTES
.Dx Ns 's
support for POSIX.1e interfaces and features is still under
development at this time.
.Sh ENVIRONMENT
POSIX.1e assigns security labels to all objects, extending the security
functionality described in POSIX.1.  These additional labels provide
fine-grained discretionary access control, fine-grained capabilities,
and labels necessary for mandatory access control.  POSIX.2c describes
a set of userland utilities for manipulating these labels.  These userland
utilities are not bundled with
.Dx
so as to discourage their
use in the short term.
.\" .Sh FILES
.Sh SEE ALSO
.Xr acl 3 ,
.Xr acl_dup 3 ,
.Xr acl_free 3 ,
.Xr acl_from_text 3 ,
.Xr acl_get 3 ,
.Xr acl_set 3 ,
.Xr acl_to_text 3 ,
.Xr acl_valid 3 ,
.Xr acl 9
.Sh STANDARDS
POSIX.1e is described in IEEE POSIX.1e draft 17.  Discussion
of the draft continues on the cross-platform POSIX.1e implementation
mailing list.  To join this list, see the
.Fx
POSIX.1e implementation
page for more information.
.Sh HISTORY
POSIX.1e support was introduced in
.Fx 4.0 ,
and development continues.
.Sh AUTHORS
.An Robert N M Watson
.Sh BUGS
These features are not yet fully implemented.  In particular, the shipped
version of UFS/FFS does not support storage of additional security labels,
and so is unable to (easily) provide support for most of these features.