Upload-labs_Pass-10_for_Linux

摘要: 我们不要用常见的思维来做,需要有新的突破

这篇文章上次修改于 10 个月前,可能部分内容已经不适用,如有疑问可询问作者。

Upload-labs_Pass-10_for_Linux

我们利用 Windows 的特性来做 Pass-10 的漏洞,那么在 Linux 下怎么做呢?

Pass-10

环境: Dokcer {Debian8 Apache2.4/Nginx1.18+PHP5.4}

题目

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",".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!';
    }
}
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在Windos 下,这里可以轻松使用 xxx.php. . 绕过黑名单,并且利用 Windows 把后缀的点和空格自动去除的特性,轻松 getshell。

Linux 下,尝试用此方法,会出现什么情况呢?

cat 一下

很明显,空格被转义了,虽然可以访问 webshell.php.%20 ,但是并不解析。

那怎么办 呢,那就先从源码入手

寻找函数的漏洞

  • trim函数过滤不全,但是这个并不能利用
  • move_uploaded_file函数漏洞

复现 ,但是很遗憾,没有能突破这个pass。

换个思路,找中间件的漏洞

Apache 2.4.0-2.4.29存在解析漏洞CVE-2017-15715,上传一个后缀末尾包含换行符的文件,来绕过FilesMatch。但绕过FilesMatch不一定能被PHP解析。但是这个题目换行符被过滤了。

那切换一下环境 (Apache2.2+php5.3)

使用Apache的多后缀名解析漏洞绕过

利用成功

除此之外,暂时没有想到其他的突破方式。