upload-labs
Pass-01 js检查
- 前端上传绕过 / 客户端js检查
源码
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;
}
}
上传php,可是提示说只能上传jip,png,gif
因为是js验证后缀名,因此抓包,改后缀名成php
改包后打开路径/upload/info.php
PS:每过一题最好清空一下上传文件
Pass-02 Content-Type判断
- 服务端对数据包的MIME检查
Content-Type(MediaType),即是Internet Media Type,互联网媒体类型,也叫做MIME类型。在互联网中有成百上千中不同的数据类型,HTTP在传输数据对象时会为他们打上称为MIME的数据格式标签,用于区分数据类型。最初MIME是用于电子邮件系统的,后来HTTP也采用了这一方案。在HTTP协议消息头中,使用Content-Type来表示请求和响应中的媒体类型信息。它用来告诉服务端如何处理请求的数据,以及告诉客户端(一般是浏览器)如何解析响应的数据,比如显示图片,解析并展示html等等。
源码
$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
if (file_exists(UPLOAD_PATH)) {
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 . '/' . $_FILES['upload_file']['name']
if (move_uploaded_file($temp_file, $img_path)) {
$is_upload = true;
} else {
$msg = '上传出错!';
}
} else {
$msg = '文件类型不正确,请重新上传!';
}
} else {
$msg = UPLOAD_PATH.'文件夹不存在,请手工创建!';
}
}
上传一个php文件,抓包看到Content-Type: application/octet-stream
并不满足源码里的判断条件if (($_FILES['upload_file']['type'] == 'image/jpeg') || ($_FILES['upload_file']['type'] == 'image/png') || ($_FILES['upload_file']['type'] == 'image/gif'))
修改Content-Type
访问发现上传成功
Pass-03 黑名单绕过
- 黑名单绕过 / 上传特殊可解析后缀
不能上传php后缀文件
试了一下大小写,报错
修改成特殊可解析后缀(PHP脚本文件有时候以php3、php4、php5、phtml、pht等后缀也可以被解析成功)
源码
$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
if (file_exists(UPLOAD_PATH)) {
$deny_ext = array('.asp','.aspx','.php','.jsp');
$file_name = trim($_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); //收尾去空
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 = '不允许上传.asp,.aspx,.php,.jsp后缀文件!';
}
} else {
$msg = UPLOAD_PATH . '文件夹不存在,请手工创建!';
}
}
Pass-04 .htaccess绕过
.htaccess文件(或者"分布式配置文件"),全称是Hypertext Access(超文本入口)。提供了针对目录改变配置的方法, 即,在一个特定的文档目录中放置一个包含一个或多个指令的文件, 以作用于此目录及其所有子目录。作为用户,所能使用的命令受到限制。管理员可以通过Apache的AllowOverride指令来设置。
源码
$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
if (file_exists(UPLOAD_PATH)) {
$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");
$file_name = trim($_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'];
$img_path = UPLOAD_PATH.'/'.date("YmdHis").rand(1000,9999).$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!';
}
}
orz,那长长的限制名单。。。
但是并没有禁止.htaccess
那就传一个.htaccess上去把所有文件都当成php来解析
上传一个内容为SetHandler application/x-httpd-php
的.htaccess文件
要注意这个文件是只有后缀没有名字的,如果保存不了就抓包把名字拿掉
上传一个后缀为jpg的php文件
Pass-05 大小写绕过
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']);
$file_name = deldot($file_name);//删除文件名末尾的点
$file_ext = strrchr($file_name, '.');
$file_ext = str_ireplace('::$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'];
$img_path = UPLOAD_PATH.'/'.date("YmdHis").rand(1000,9999).$file_ext;
if (move_uploaded_file($temp_file, $img_path)) {
$is_upload = true;
} else {
$msg = '上传出错!';
}
} else {
$msg = '此文件类型不允许上传!';
}
} else {
$msg = UPLOAD_PATH . '文件夹不存在,请手工创建!';
}
}
这次.htaccess也上黑名单了,但是对比一下之前的源码,发现这题的源码把转换为小写的那行代码给拿掉了
传一个.Php
Pass-06 加空格绕过
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 = $_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!';
}
}
这题没有对后缀名进行首尾去空,因此在php后面加个空格即可绕过黑名单
但是直接重命名加空格Windows会自己给你去掉
那么,抓包加空格上传,windows保持文件时自动将空格去除
访问路径,发现上传成功
Pass-07 加.绕过
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 {
$msg = UPLOAD_PATH . '文件夹不存在,请手工创建!';
}
}
少了删除文件名末尾的点的代码
与Pass-06相似,Windows保持文件时会自动将末尾的点去除
上传info.php文件,抓包改为info.php.,访问info.php
Pass-08 加::$DATA绕过
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']);
$file_name = deldot($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
$file_ext = trim($file_ext); //首尾去空
if (!in_array($file_ext, $deny_ext)) {
$temp_file = $_FILES['upload_file']['tmp_name'];
$img_path = UPLOAD_PATH.'/'.date("YmdHis").rand(1000,9999).$file_ext;
if (move_uploaded_file($temp_file, $img_path)) {
$is_upload = true;
} else {
$msg = '上传出错!';
}
} else {
$msg = '此文件类型不允许上传!';
}
} else {
$msg = UPLOAD_PATH . '文件夹不存在,请手工创建!';
}
}
少了$file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA
不知道不去掉这个有会出现什么情况,但是根据前面做题的经验,抓包后在后缀名后面加个::$DATA试试
查了一下
在Windows中,如果文件名+"::$DATA"会把::$DATA之后的数据当成文件流处理,不会检测后缀名.且保持"::$DATA"之前的文件名。
Pass-09 加. .绕过
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']);
$file_name = deldot($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!';
}
}
看了半天没看出啥毛病,就是在拼接文件路径的时候没有用随机文件名了
知道了这个有啥用?
上网去查资料,没点进文章里但是我看到了".+空格+."
???
也就是说,先让它搞掉一个".",接着还会再去空格,最后Windows还会帮忙拿走最后一个点
是在下太菜了,这么简单都不会
Pass-10 双写绕过
上传没啥毛病,但是它好像把我的php给吃掉了,还给我留了个"."
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","jsp","jspa","jspx","jsw","jsv","jspf","jtml","asp","aspx","asa","asax","ascx","ashx","asmx","cer","swf","htaccess");
$file_name = trim($_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;
if (move_uploaded_file($temp_file, $img_path)) {
$is_upload = true;
} else {
$msg = '上传出错!';
}
} else {
$msg = UPLOAD_PATH . '文件夹不存在,请手工创建!';
}
}
黑名单过滤,将黑名单里的后缀名替换为空,用双写绕过
往info.php的后缀名里再塞个php→info.pphphp,那行代码会把在黑名单里的字符串php干掉
之后就变成info.php了
当然插个jsp啥的变成info.phjspp也行
Pass-11 %00绕过
变成白名单了
源码
$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){
$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;
if(move_uploaded_file($temp_file,$img_path)){
$is_upload = true;
} else {
$msg = '上传出错!';
}
} else{
$msg = "只允许上传.jpg|.png|.gif类型文件!";
}
}
白名单判断,还有路径拼接,可以利用00截断来绕过
上传info.jpg,抓包,将save_path修改为save_path=../upload/info.php%00
截断直接体现在了粘贴的时候,粘贴之后/xxxxx.jpg直接不知道半路掉哪去了
这样,上传的文件就拥有一个让它能够被解析的后缀名啦
Pass-12 0x00绕过
源码
$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){
$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;
if(move_uploaded_file($temp_file,$img_path)){
$is_upload = true;
} else {
$msg = "上传失败";
}
} else {
$msg = "只允许上传.jpg|.png|.gif类型文件!";
}
}
找不同找不同
save_path变成了POST请求发出去了
抓包,先修改路径
再进hex把%改了
Pass-13 图片马绕过
题解
function getReailFileType($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 {
$msg = "上传出错!";
}
}
}
通过读文件的前2个字节判断文件类型题目要求上传图片马到服务器
可以写个php文件
GIF89a
<?php
phpinfo();
?>
然后上传的时候抓包改成gif
这里还给了个页面让用文件包含看
或者就是用copy命令做一个
copy 1.png/b + info.php/a info.png
直接传然后文件包含
Pass-14 图片马绕过
源码
function isImage($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 {
$msg = "上传出错!";
}
}
}
用getimagesize()
函数判断文件类型
这好像跟Pass-13也没啥差。。。
Pass-15 图片马绕过
源码
function isImage($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!";
}
}
}
用php_exif模块来判断文件类型
依旧没啥变化的一题
Pass-16 二次渲染绕过
源码
$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!";
}
}
emmm,有些变化了,因为我做不出来இ௰இ
Pass-17 条件竞争
条件竞争
条件竞争漏洞是一种服务器端的漏洞,由于服务器端在处理不同用户的请求时是并发进行的,因此,如果并发处理不当或相关操作逻辑顺序设计的不合理时,将会导致此类问题的发生。比如,很多web程序都会有上传文件的功能,头像和图像等,服务器肯定会检查文件是否满足条件,不满足的要被删除。
那么问题就在于,如果我们采用大量的并发请求,就传递一个生成恶意webshell的图像,访问它就可以生成webshell。在上传完成和安全检查完成并删除它的间隙,攻击者通过不断地发起访问请求的方法访问了该文件,该文件就会被执行,并且在服务器上生成一个恶意shell的文件。
源码
$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, $upload_file)){
if(in_array($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!';
}
}
先把文件上传到服务器,再判断文件在不在白名单里,如果在则重命名,否则删除,因此我们可以上传1.php只需要在它删除之前访问即可,可以利用burp的intruder模块不断上传,然后我们不断的访问刷新该地址即可
传个info.php上去,然后用burpsuite不断上传,并且不断访问
Pass-18 条件竞争
源码
//index.php
$is_upload = false;
$msg = null;
if (isset($_POST['submit']))
{
require_once("./myupload.php");
$imgFileName =time();
$u = new MyUpload($_FILES['upload_file']['name'], $_FILES['upload_file']['tmp_name'], $_FILES['upload_file']['size'],$imgFileName);
$status_code = $u->upload(UPLOAD_PATH);
switch ($status_code) {
case 1:
$is_upload = true;
$img_path = $u->cls_upload_dir . $u->cls_file_rename_to;
break;
case 2:
$msg = '文件已经被上传,但没有重命名。';
break;
case -1:
$msg = '这个文件不能上传到服务器的临时文件存储目录。';
break;
case -2:
$msg = '上传失败,上传目录不可写。';
break;
case -3:
$msg = '上传失败,无法上传该类型文件。';
break;
case -4:
$msg = '上传失败,上传的文件过大。';
break;
case -5:
$msg = '上传失败,服务器已经存在相同名称文件。';
break;
case -6:
$msg = '文件无法上传,文件不能复制到目标目录。';
break;
default:
$msg = '未知错误!';
break;
}
}
//myupload.php
class MyUpload{
......
......
......
var $cls_arr_ext_accepted = array(
".doc", ".xls", ".txt", ".pdf", ".gif", ".jpg", ".zip", ".rar", ".7z",".ppt",
".html", ".xml", ".tiff", ".jpeg", ".png" );
......
......
......
/** upload()
**
** Method to upload the file.
** This is the only method to call outside the class.
** @para String name of directory we upload to
** @returns void
**/
function upload( $dir ){
$ret = $this->isUploadedFile();
if( $ret != 1 ){
return $this->resultUpload( $ret );
}
$ret = $this->setDir( $dir );
if( $ret != 1 ){
return $this->resultUpload( $ret );
}
$ret = $this->checkExtension();
if( $ret != 1 ){
return $this->resultUpload( $ret );
}
$ret = $this->checkSize();
if( $ret != 1 ){
return $this->resultUpload( $ret );
}
// if flag to check if the file exists is set to 1
if( $this->cls_file_exists == 1 ){
$ret = $this->checkFileExists();
if( $ret != 1 ){
return $this->resultUpload( $ret );
}
}
// if we are here, we are ready to move the file to destination
$ret = $this->move();
if( $ret != 1 ){
return $this->resultUpload( $ret );
}
// check if we need to rename the file
if( $this->cls_rename_file == 1 ){
$ret = $this->renameFile();
if( $ret != 1 ){
return $this->resultUpload( $ret );
}
}
// if we are here, everything worked as planned :)
return $this->resultUpload( "SUCCESS" );
}
......
......
......
};
Pass-19 00截断
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","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;
if (move_uploaded_file($temp_file, $img_path)) {
$is_upload = true;
}else{
$msg = '上传出错!';
}
}else{
$msg = '禁止保存为该类型文件!';
}
} else {
$msg = UPLOAD_PATH . '文件夹不存在,请手工创建!';
}
}
0x00截断,同Pass-12
Pass-20
源码
$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{
$msg = "请选择要上传的文件!";
}
判断过程
判断$file是不是一个数组,不是的话就以"."为边界拆成数组拿数组最后一个元素,即"文件后缀"比对白名单
通过比对之后,拿"数组第一个元素"+"."+"数组倒二个元素"这个字符串作为文件名
既然没有过滤掉数组,那其实抓包之后传个数组上去就能把php上传上去了
防御
限制文件上传的类型
- 白名单结合黑名单
- 前端JS结合后端限制
- 扩展名检测,需要防范%截断或者文件名包含空格等特殊字符的绕过方式,最好的方式就是重命名用户上传的文件,杜绝上传时的文件名攻击。
- 对于用户上传的图片,可以考虑对其进行二次渲染或者压缩,当用户上传图片时,要求用户对图片进行截取。
限制上传文件大小
确保上传文件被访问正确返回
- 将文件上传目录设置为静态资源目录,防止被解析为脚本执行。
- 使用代理页面隐藏真实路径,如/attachment/getfile.php?fileid=123
- 使用上诉方式时,确保Content-Type与实际文件类型一致(检测文件时不要只是检测文件后缀,最主要的是在后端检测文件头是什么类型)。
- 如果文件不允许在页面展示,仅允许下载,请设置Content-disposition:attachment
其他方式
- 确保上传的文件放在安全的路径下,必要时可将上传的文件放于web server之外的远程服务器。
- 确保web server版本为最新,防止由于web server老版本漏洞造成的文件意外解析。
- 部分文件上传攻击会配合本地其他漏洞进行,所以也要保证web服务器减少其他可利用漏洞。
?传哪儿去了
在我电脑的typora里....