Experimental building - PHP Dafa

subject ：http://ctf5.shiyanbar.com/DUTCTF/index.php

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View this file ：ctf5.shiyanbar.com/DUTCTF/index.php.txt

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       <?php
       
       
if(eregi("hackerDJ",$_GET[id])) {
       
       
  echo("<p>not allowed!</p>");
       
       
  exit();
       
       
}
       
       

       
       
$_GET[id] = urldecode($_GET[id]);
       
       
if($_GET[id] == "hackerDJ")
       
       
{
       
       
  echo "<p>Access granted!</p>";
       
       
  echo "<p>flag: *****************} </p>";
       
       
}
       
       
?>
      
      
      
      

       
       
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Learned here , Will be submitted first id Find out whether it contains hackerDJ, Exit if included

In addition, we need to be right id Conduct url decode , Judge whether the decoded value is equal to hackerDJ, If it is equivalent, you get flag

Here we need to construct hackerDJ, Let it meet the requirements here at the same time , So it's OK to hackerDJ Conduct url code

The encoded character meets the first condition , Then because of the decoding process , Will automatically encode our characters

Decode to what you need hackerDJ, Finally get what we need to hackerDJ do 2 Second code

First the h Conduct url Code to get %68

Yes %68 Encode again to get %2568

The final splicing url Get the results