我们先看看源码

源码

$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");
        $file_name = trim($_FILES['upload_file']['name']);
        $file_ext = strrchr($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!';
    }
}

看看上面的代码都限制了多少吧,大小写,加空格,加字符串,黑名单,好多限制。。。。。

1.txt.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"

这个时候可以采用一种方法来绕过,因为靶场是搭建在windows上的,所以windows有一个特性,windows系统自动去掉不符合规则符号后面的内容,什么意思呢?举个栗子

比如你新建了一个1.txt文件,然后你将名称改为1.txt.试试,虽然会有下面的警告,但是windows还是会默认去掉后面的.,名字还是变成了1.txt
TIM截图20181108102454.png
这个时候我们就可以利用.来绕过限制了,因为strrchr函数会将上传的文件名后缀处理为.php.,当上传到win机器上时又会将后面的.去掉,然后后缀就又会被还原成.php,这样就可以执行了,下面演示一下

首先上传1.php文件并抓包,在burp修改文件后缀名为.php.
1412252-20181023225201276-323753189.png

测试链接

22.png
PS:此方法只适用于windows主机

Last modification:December 13th, 2018 at 06:15 pm
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