friendica-github/include/security.php

<?php

function can_write_wall(&$a,$owner) {

        if((! (local_user())) && (! (remote_user())))
                return false;
		$uid = local_user();

        if(($uid) && ($uid == $owner)) {
                return true;
		}

		if(remote_user()) {
			$r = q("SELECT `contact`.*, `user`.`page-flags` FROM `contact` LEFT JOIN `user` on `user`.`uid` = `contact`.`uid` 
				WHERE `contact`.`uid` = %d AND `contact`.`id` = %d AND `contact`.`blocked` = 0 AND `contact`.`pending` = 0 
				AND `readonly` = 0  AND ( `contact`.`rel` IN ( %d , %d ) OR `user`.`page-flags` = %d ) LIMIT 1",
				intval($owner),
				intval(remote_user()),
				intval(REL_VIP),
				intval(REL_BUD),
				intval(PAGE_COMMUNITY)
			);
		}
		if(count($r))
			return true;

		
        return false;

}