kr_attr_valid
retval = kr_attr_valid(type, in);
retval = kr_attr_valid(type, in);
retval = kr_attr_valid(type, data);
kr_attr_valid(krad_attr type, const krb5_data *data);
insist(kr_attr_valid(KRAD_ATTR_USER_PASSWORD, &in) == 0);
insist(kr_attr_valid(KRAD_ATTR_USER_PASSWORD, &in) != 0);