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upload-labs靶场通关详解：第10关

news 来源：原创 2025/5/20 6:44:11

一、分析源代码

$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 = trim($_FILES['upload_file']['name']);$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$file_ext = trim($file_ext); //首尾去空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 = '此文件类型不允许上传！';}} else {$msg = UPLOAD_PATH . '文件夹不存在,请手工创建！';}
}

通过6-9关的练习，我们掌握了4种绕过方式，但是这关的代码将4种方式都进行了过滤，那么又该用什么思路呢？

二、解题思路

没有完美的代码，如果找不到代码的缺漏之处，那就尝试找到代码的逻辑错误。这里的代码进行了4种过滤，如果采用多次结合的方法去尝试呢？比如，我在文件后缀名加上点，再加上空格，再加上点。代码在执行时，按照顺序，首先会删除点，再删除空格，这样看起来就似乎没什么问题了。可是文件后缀此时还是存在一个句点没有被删除，那是否就产生了绕过的可能？试一试便知。