generate a POSIX.1e ACL access control decision using
, uid_t file_uid
struct acl *acl
struct ucred *cred
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
, owning GID
, access ACL for the file
, desired access mode
, requesting credential
, and an optional call-by-reference
pointer returning whether or not
privilege was required for successful evaluation of the call; the
pointer may be set to
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
which will use their own access methods to retrieve the vnode properties, and
() in order
to perform the actual check. Implementations of
may choose to implement additional security mechanisms whose results will be
composed with the return value.
The algorithm used by
is based on the POSIX.1e ACL evaluation algorithm. The algorithm selects a
entry from the access ACL, which may
then be composed with an available ACL mask entry, providing
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 credential. If the rights
granted by discretionary protections are insufficient, then super-user
privilege, if available for the credential, will also be considered.
() will return 0 on
success, or a non-zero error value on failure.
- Permission denied. An attempt was made to access a file in a way forbidden
by its file access permissions.
- Operation not permitted. An attempt was made to perform an operation
limited to processes with appropriate privileges or to the owner of a file
or other resource.
This manual page and the current implementation of
() were written by
This manual page should include a full description of the POSIX.1e ACL
evaluation algorithm, or cross reference another page that does.