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vaccess_acl_posix1e - generate a POSIX.1e ACL access control decision
using vnode parameters
vaccess_acl_posix1e(enum vtype type, uid_t file_uid, gid_t file_gid,
struct acl *acl, mode_t acc_mode, 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 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 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 otherwise.
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_posix1e() 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_posix1e() is based on the POSIX.1e ACL
evaluation algorithm. 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
vaccess_acl_posix1e() will return 0 on success, or a non-zero error value
[EACCES] Permission denied. An attempt was made to access a
file in a way forbidden by its file access
[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
vaccess(9), vnode(9), VOP_ACCESS(9)
This manual page and the current implementation of vaccess_acl_posix1e()
were written by Robert Watson.
This manual page should include a full description of the POSIX.1e ACL
evaluation algorithm, or cross reference another page that does.