由于您的问题涉及到多个Web入门级CTF题目,这些题目通常涉及到PHP的特性,我将提供一个简单的PHP代码示例来说明如何处理这些问题。
假设我们有一个名为 web123.php
的文件,其中包含以下代码:
<?php
if (isset($_GET['flag'])) {
$flag = $_GET['flag'];
if (strlen($flag) > 30) {
echo 'Too long.';
} else {
file_put_contents('flag.txt', $flag);
echo 'Flag saved.';
}
} else {
highlight_file(__FILE__);
}
?>
这个文件检查是否存在一个名为 flag
的GET参数。如果存在,它将检查该参数的长度是否超过30个字符。如果不是,它将使用 file_put_contents()
函数将该参数写入 flag.txt
文件。
这个过程可能是一系列的Web入门CTF题目的开始,比如 web123
到 web139
,你可能需要通过不同的方法来绕过这些安全检查。
例如,你可以使用URL编码或者双写绕过长度检查:
?flag=hacking<?php%20echo%20'ctfshow';?>
或者
?flag=hackingphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphphph