VACCESS_ACL_NFS4(9)       BSD Kernel Developer's Manual      VACCESS_ACL_NFS4(9)

     vaccess_acl_nfs4 — generate a NFSv4 ACL access control decision using vnode

     #include <sys/param.h>
     #include <sys/vnode.h>
     #include <sys/acl.h>

     vaccess_acl_nfs4(enum vtype type, uid_t file_uid, gid_t file_gid,
         struct acl *acl, accmode_t accmode, struct ucred *cred, int *privused);

     This call implements the logic for the UNIX discretionary file security
     model with NFSv4 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 accmode, requesting credential cred, and an optional call-by-
     reference int pointer returning whether or not privilege 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

     This call is intended to support implementations of VOP_ACCESS(9), which
     will use their own access methods to retrieve the vnode properties, and
     then invoke vaccess_acl_nfs4() in order to perform the actual check.
     Implementations of VOP_ACCESS(9) may choose to implement additional
     security mechanisms whose results will be composed with the return value.

     The algorithm used by 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 matching entry 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 credential.  If the rights
     granted by discretionary protections are insufficient, then super-user
     privilege, if available for the credential, will also be considered.

     vaccess_acl_nfs4() will return 0 on success, or a non-zero error value on

     [EACCES]           Permission denied.  An attempt was made to access a file
                        in a way forbidden by its file access permissions.

     [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.

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

     Current implementation of vaccess_acl_nfs4() was written by Edward Tomasz
     Napierala <>.

     This manual page should include a full description of the NFSv4 ACL
     evaluation algorithm, or cross reference another page that does.

BSD                            September 18, 2009                            BSD