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.Dd September 18, 2009
.Dt VACCESS_ACL_NFS4 9
.Os
.Sh NAME
.Nm vaccess_acl_nfs4
.Nd generate a NFSv4 ACL access control decision using vnode parameters
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.In sys/acl.h
.Ft int
.Fo vaccess_acl_nfs4
.Fa "enum vtype type"
.Fa "uid_t file_uid"
.Fa "gid_t file_gid"
.Fa "struct acl *acl"
.Fa "accmode_t accmode"
.Fa "struct ucred *cred"
.Fa "int *privused"
.Fc
.Sh DESCRIPTION
This call implements the logic for the
.Ux
discretionary file security model
with NFSv4 ACL extensions.
It accepts the vnodes type
.Fa type ,
owning UID
.Fa file_uid ,
owning GID
.Fa file_gid ,
access ACL for the file
.Fa acl ,
desired access mode
.Fa accmode ,
requesting credential
.Fa cred ,
and an optional call-by-reference
.Vt int
pointer returning whether or not
privilege was required for successful evaluation of the call; the
.Fa privused
pointer may be set to
.Dv 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.
.Pp
This call is intended to support implementations of
.Xr VOP_ACCESS 9 ,
which will use their own access methods to retrieve the vnode properties,
and then invoke
.Fn vaccess_acl_nfs4
in order to perform the actual check.
Implementations of
.Xr VOP_ACCESS 9
may choose to implement additional security mechanisms whose results will
be composed with the return value.
.Pp
The algorithm used by
.Fn vaccess_acl_nfs4
is based on the NFSv4 ACL evaluation algorithm, as described in
NFSv4 Minor Version 1, draft-ietf-nfsv4-minorversion1-21.txt.
The algorithm selects a
.Em matching
entry from the access ACL, which may
then be composed with an available ACL mask entry, providing
.Ux
security compatibility.
.Pp
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.
.Sh RETURN VALUES
.Fn vaccess_acl_nfs4
will return 0 on success, or a non-zero error value on failure.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EACCES
Permission denied.
An attempt was made to access a file in a way forbidden by its file access
permissions.
.It Bq Er EPERM
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.
.El
.Sh SEE ALSO
.Xr vaccess 9 ,
.Xr vnode 9 ,
.Xr VOP_ACCESS 9
.Sh AUTHORS
Current implementation of
.Fn vaccess_acl_nfs4
was written by
.An Edward Tomasz Napierala Aq Mt trasz@FreeBSD.org .
.Sh BUGS
This manual page should include a full description of the NFSv4 ACL
evaluation algorithm, or cross reference another page that does.