.\"-
.\" Copyright (c) 2000, 2001 Robert N. M. Watson
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.\" $FreeBSD$
.\"
.Dd January 28, 2000
.Dt ACL 3
.Os FreeBSD
.Sh NAME
.Nm acl
.Nd introduction to the POSIX.1e ACL security API
.Sh LIBRARY
.Lb libposix1e
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/acl.h>
.Sh DESCRIPTION
.Fx
permits file systems to export Access Control Lists via the VFS, and
provides a library for userland access to and manipulation of these ACLs.
Not all file systems provide support for ACLs, and some may require that
ACL support be explicitely enabled by the administrator.
The library calls 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, Coda, 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; almost
all of these support routines are implemented in
.Fx .
.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
.Fx 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.
.\" .Sh FILES
.Sh SEE ALSO
.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 ,
.Xr posix1e 3
.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 ;
.Fx 5.0
was the first version to include a complete ACL implementation based
on extended attributes.
.Sh AUTHORS
.An Robert N M Watson