Function auth_setdata 

pub unsafe extern "C" fn auth_setdata(
    _as: *mut auth_session_t,
    _ptr: *mut c_void,
    _len: u64,
) -> c_int

Pass data to the BSD Authentication session to be used by a login script

From auth_subr(3):

Makes a copy of `len` bytes of data pointed to by `ptr` for use by `auth_call()`. The data
will be passed on the back channel to the next login script called.