upload-labs关卡7(基于黑名单的空格绕过)通关思路

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前言

此文章只用于学习和反思巩固文件上传漏洞知识，禁止用于做非法攻击。注意靶场是可以练习的平台，不能随意去尚未授权的网站做渗透测试！！！

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一、回顾上一关知识点

前两关是利用window命名文件的后缀名特性，因为window对大小写不敏感。而且命名后缀名的时候，后缀名加空格或者是后缀名加点都是等效于不加东西的文件。比如1.php+空格也就是1.php

二、靶场第七关通关思路

• 1、看源代码
• 2、空格绕过
• 3、检查文件是否成功上传

1、看源代码

$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",".pHp",".pHp5",".pHp4",".pHp3",".pHp2",".Html",".Htm",".pHtml",".jsp",".jspa",".jspx",".jsw",".jsv",".jspf",".jtml",".jSp",".jSpx",".jSpa",".jSw",".jSv",".jSpf",".jHtml",".asp",".aspx",".asa",".asax",".ascx",".ashx",".asmx",".cer",".aSp",".aSpx",".aSa",".aSax",".aScx",".aShx",".aSmx",".cEr",".sWf",".swf",".htaccess",".ini");
        $file_name = $_FILES['upload_file']['name'];
        $file_name = deldot($file_name);//删除文件名末尾的点
        $file_ext = strrchr($file_name, '.');
        $file_ext = strtolower($file_ext); //转换为小写
        $file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA
        
        if (!in_array($file_ext, $deny_ext)) {
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH.'/'.date("YmdHis").rand(1000,9999).$file_ext;
            if (move_uploaded_file($temp_file,$img_path)) {
                $is_upload = true;
            } else {
                $msg = '上传出错！';
            }
        } else {
            $msg = '此文件不允许上传';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夹不存在,请手工创建！';
    }
}

看到源代码发现有了大小写过滤，上一关方法不管用了。但是发现和上一关不同的是它没有过滤首尾去空。如果我们上传1.php （空格）文件的话，是不是就能绕过黑名单了呢？而且还能被win服务器自动识别为1.php文件

2、空格绕过

这里我上传123.php文件，然后用bp工具在文件后缀名后加上空格后发包。

3、检查文件是否成功上传

发现上传成功，如果是一句话木马就可以连接菜刀了

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总结

这一关和上一关方法类似，也是利用win特性绕过黑名单达到上传php文件