[Network Security] Upload-labs Pass-20 Detailed Analysis of Problem Solving

Readers can refer to and subscribe to the column: Upload-Labs shooting range offensive and defensive combat

Antsword Ant Sword

The use of Ant Sword tool can refer to:

[Network Security] AntSword (ant sword) actual combat problem solving detailed analysis (entry)

[Network Security] DVWA's File Upload—AntSword (Ant Sword) attack posture and detailed analysis of problem solving collection

posture

Backend logic code:

<?php
include '../config.php';
include '../common.php';
include '../head.php';
include '../menu.php';

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    
    
    if (file_exists(UPLOAD_PATH)) {
    
    
        $deny_ext = array("php","php5","php4","php3","php2","html","htm","phtml","pht","jsp","jspa","jspx","jsw","jsv","jspf","jtml","asp","aspx","asa","asax","ascx","ashx","asmx","cer","swf","htaccess");

        /*
        $file_name = trim($_POST['save_name']);
        $file_name = deldot($file_name);//删除文件名末尾的点
        $file_ext = pathinfo($file_name,PATHINFO_EXTENSION);
        $file_ext = strtolower($file_ext); //转换为小写
        $file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA
        $file_ext = trim($file_ext); //首尾去空
        */

        $file_name = $_POST['save_name'];
        $file_ext = pathinfo($file_name,PATHINFO_EXTENSION);

        if(!in_array($file_ext,$deny_ext)) {
    
    
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH . '/' .$file_name;
            if (move_uploaded_file($temp_file, $img_path)) {
    
     
                $is_upload = true;
            }else{
    
    
                $msg = '上传出错！';
            }
        }else{
    
    
            $msg = '禁止保存为该类型文件！';
        }

    } else {
    
    
        $msg = UPLOAD_PATH . '文件夹不存在,请手工创建！';
    }
}
?>

<div id="upload_panel">
    <ol>
        <li>
            <h3>任务</h3>
            <p>上传一个<code>webshell</code>到服务器。</p>
        </li>
        <li>
            <h3>上传区</h3>
            <form enctype="multipart/form-data" method="post">
                <p>请选择要上传的图片：<p>
                <input class="input_file" type="file" name="upload_file"/>
                <p>保存名称:<p>
                <input class="input_text" type="text" name="save_name" value="upload-19.jpg" /><br/>
                <input class="button" type="submit" name="submit" value="上传"/>
            </form>
            <div id="msg">
                <?php 
                    if($msg != null){
    
    
                        echo "提示：".$msg;
                    }
                ?>
            </div>
            <div id="img">
                <?php
                    if($is_upload){
    
    
                        echo '<img src="'.$img_path.'" width="250px" />';
                    }
                ?>
            </div>
        </li>
        <?php 
            if($_GET['action'] == "show_code"){
    
    
                include 'show_code.php';
            }
        ?>
    </ol>
</div>

<?php
include '../footer.php';
?>

Simply put, a blacklist is defined, and then the move_uploaded_file function is used to move the temporary uploaded file to the specified target path

Since the move_uploaded_file function ignores the /. at the end of the file

Therefore, when we upload shell.php/., we can not only bypass the blacklist, but also change to shell.php when moving the path, so as to achieve the purpose of command execution.

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Then upload:

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Capture packets:

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Repackage:

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Packing:

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Exploiting the files provided by the range contains the vulnerability:

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Successfully achieved command execution:

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Summarize

The above is the detailed analysis of [Network Security] upload-labs Pass-20 problem solving, and the detailed analysis of [Network Security] xss-labs Pass-21 problem solving will be shared later.

I am Qiu said , see you next time.