vaccess_acl_posix1e(9)

NAME

vaccess_acl_posix1e - generate a POSIX.1e ACL access control

decision
using vnode parameters

SYNOPSIS

#include <sys/param.h>
#include <sys/vnode.h>
#include <sys/acl.h>
int
vaccess_acl_posix1e(enum  vtype  type, uid_t file_uid, gid_t
file_gid,
        struct  acl  *acl,  mode_t  acc_mode,  struct  ucred
*cred,
        int *privused);

DESCRIPTION

This call implements the logic for the UNIX discretionary

file security
model with POSIX.1e ACL extensions. It accepts the vnodes

type type,
owning UID file_uid, owning GID file_gid, access ACL for the

file acl,
desired access mode acc_mode, requesting credential cred,

and an optional
call-by-reference int pointer returning whether or not priv

ilege was
required for successful evaluation of the call; the privused

pointer may
be set to NULL by the caller in order not to be informed of

privilege
information, or it may point to an integer that will be set

to 1 if privilege is used, and 0 otherwise.

This call is intended to support implementations of VOP_AC

CESS(9), which
will use their own access methods to retrieve the vnode

properties, and
then invoke vaccess_acl_posix1e() in order to perform the

actual check.
Implementations of VOP_ACCESS(9) may choose to implement ad

ditional security mechanisms whose results will be composed with the re

turn value.

The algorithm used by vaccess_acl_posix1e() is based on the

POSIX.1e ACL
evaluation algorithm. The algorithm selects a matching en

try from the
access ACL, which may then be composed with an available ACL

mask entry,
providing UNIX security compatibility.

Once appropriate protections are selected for the current

credential, the
requested access mode, in combination with the vnode type,

will be compared with the discretionary rights available for the cre

dential. If the
rights granted by discretionary protections are insuffi

cient, then superuser privilege, if available for the credential, will also

be considered.

RETURN VALUES

vaccess_acl_posix1e() will return 0 on success, or a non-ze

ro error value
on failure.

ERRORS

[EACCES] Permission denied. An attempt was made

to access a

file in a way forbidden by its file ac

cess permissions.

[EPERM] Operation not permitted. An attempt was

made to per

form an operation limited to processes

with appropriate privileges or to the owner of a file

or other
resource.

SEE ALSO

vaccess(9), vnode(9), VOP_ACCESS(9)

AUTHORS

This manual page and the current implementation of

vaccess_acl_posix1e()
were written by Robert Watson.

BUGS

This manual page should include a full description of the

POSIX.1e ACL
evaluation algorithm, or cross reference another page that

does.

BSD August 22, 2001

BSD