[Webhacking.kr] old-11

old-11

This problem is in webhacking.kr.
URL: https://webhacking.kr/challenge/code-2//

If you enter the URL, you can see the below photo.

 

First, View Source

If you look at the code, you can see this part.

<?php
  $pat="/[1-3][a-f]{5}_.*$_SERVER[REMOTE_ADDR].*\tp\ta\ts\ts/";
  if(preg_match($pat,$_GET['val'])){
    solve(11);
  }
  else echo("<h2>Wrong</h2>");
  echo("<br><br>");
?>

You can know that you can solve the problem if the value of $val sent through "Get Method" is the same as the $pat.
Let's analyze the code.

/[1-3][a-f]{5}_.*$_SERVER[REMOTE_ADDR].*\tp\ta\ts\ts/

[1-3][a-f]{5}: (1~3)(the five characters among (a~f)) 

*$_SERVER[REMOTE_ADDR]: [Your IP Address] (More than 0)

IP link: https://www.findip.kr//

*\tp\ta\ts\ts/: (\t == %09) (More than 0)

Thus, we can manipulate the value of $val like below through this.

$val = 1abcde_[Your IP]%09p%09a%09s%09s   

If you enter the URL like this, you can solve the problem.

https://webhacking.kr/challenge/code-2/?val=1abcde_[Your IP]%09p%09a%09s%09s