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文件上传漏洞靶场分析 UPLOAD
Web前端之巅
2022-08-16 21:30:45 2022-08-16
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文件上传漏洞靶场（作者前言）

项目地址：https://github.com/c0ny1/upload-labs

文件上传漏洞

产生原理

PASS 1)

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;
  }
}

源码分析

这是一串JS前端语言编写的文件上传 这边限制上传的文件类型为JPG;PNG;GIF三种 通过file.substring（file.lastIndexof(".")); #获取文件后缀名 并判断文件的后缀名是否等于允许的文件类型 没有对文件名后缀做过滤限制

绕过方法

*JS是前端开发语言 1.更改php文件后缀名，上传图片文件时可以通过Burpsuite 进行拦截请求数据包并更改文件后缀名 2.F12查看前端代码 并复制 程序执行的过滤，按需求对其进行删改操作 3.修改form表单 定义action 进行直接上传的操作

防御方法

验证文件真实性 过滤空格、点、大小写、双写、流文件

PASS 2）

$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！';
  }
}

源码分析

if

(($_FILES['upload_file']['type'] == 'image/jpeg') ||
($_FILES['upload_file']['type'] == 'image/png') ||
($_FILES['upload_file']['type'] == 'image/gif'))
这边仅对上传的文件类型做了过滤 没有对上传的文件后缀做过滤 且请求方式为POST

绕过方法

  1. 上传php文件时使用Burpsuite 更改请求头中的内容类型（content-type:image/jpeg:png:gif） 任意一种允许的文件类型。
  2. 上传转格式的包含php执行程序的图片文件，使用Burpsuite 更改后缀名

防御方法

1.验证图片文件的真实性

2.过滤上传文件的后缀名

PASS 3）

$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！';
  }
}

源码分析

$deny_ext = array('.asp','.aspx','.php','.jsp');

这边使用黑名单防御方法 不允许 后缀为.asp ; .aspx ; .php ; .jsp 的后端语言文件
if(!in_array($file_ext, $deny_ext))
取出用户后缀名，如果不存在限制的后缀名 则执行接下来的操作

绕过方法

  1. 使用php文件时 可以使用其他的php语言支持的后缀名 比如php3 phtml

通过查阅apache配置文件 httpd.conf中的 AddType application/x-httpd-php .php .php3 .phtml

这是phpstudy（PHP 5.2.17） apache配置文件中默认配置支持的文件.php .php3 .phtml

application/x-httpd-php ：指定应用程序php的可用后缀名

原理：Addtype 添加类型 可以手动指定任意后缀名让apache服务解析至PHP文件 认定位php程序并执行
···比如： AddType application/x-httpd-php .abc 这里以.abc为后缀的文件将被认为是php执行文件

  1. 使用.htaccess 分布式配置文件 将上传目录的中的所有文件的执行策略更改为php执行程序

防御方法

  1. 过滤完整的后端执行后缀名
  2. 过滤分布式配置文件.htaccess
  3. 使用白名单防御方法（只允许）

PASS 4）

$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); //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 = '此文件不允许上传!';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夹不存在,请手工创建！';
    }
}

源码分析

$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");
以上源码 没有对.htaccess配置文件进行限制

$file_name = trim($_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
以上源码 trim函数使用两次

绕过方法

  1. 上传.htaccess 分布式配置文件 修改文件执行策略 针对目录改变配置的方法
    SetHandle application/x-httpd-php
    告诉apache 当前目录下的所有后缀名解析为php

<FilesMatch "file_name.png">

SetHandler application/x-httpd-php
告诉apache，只对当前目录下 file_name.png 文件当作php代码执行，其他文件照常不变

  1. 上传文件时使用BP拦截请求消息包 更改后缀名为.php. .绕过

程序执行时从上至下执行首先对文件名进行首尾清除空格

接着删除文件末尾的.
最后删除文件末尾的空格

即file.php. . 上传时

执行deldot($file_name)>
file.php.$nbsp 上传中执行trim($file_ext)>
留下file.php.

防御方法

  1. 过滤htaccess 限制上传此文件
  2. 使用白名单防御方法 只允许想要上传的格式（白名单和黑名单防御方法根据需求定）

PASS 5）

$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！';
  }
}

源码分析

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
以上源码 trim函数使用两次，且没有对后缀名的大小写进行过滤 —— strtolower() 将字符转为小写

绕过方法

  1. 利用win系统的特性因为大小写不敏感 可以使用大小写绕过的方法绕过 即.PHp 这一特性不适用Linux系统
  2. 双写后缀名格式

    上传文件时使用BP拦截请求消息包 更改后缀名为.php. .绕过 即file.php. . 上传时 执行deldot($file_name)> file.php.$nbsp 上传中执行trim($file_ext)> 留下file.php.

防御方法

  1. 白名单防御方法 只允许上传图片格式的文件（白名单和黑名单防御方法根据需求定）
  2. 限制大小写 转换为小写

PASS 6）

$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！';
  }
}

源码分析

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

这里没有使用trim() 清除字符首尾空格函数 可以利用系统特性后缀名末尾为空格即为空这一文件

绕过方法

  1. 使用BP拦截请求消息 更改后缀名+空格 即.php+%20

防御方法

  1. 白名单防御法 只允许想要上传进入的文件格式
  2. 使用trim函数

PASS 7）

$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！';
    }
}

源码分析

$file_name = trim($_FILES['upload_file']['name']);

$file_ext = trim($file_ext); //首尾去空
# trim() 函数移除字符串两侧的空白字符或其他预定义字符
没有使用deldot函数
# deldot($file_name) 删除文件名末尾的点

绕过方法

  1. 使用Burpsuite 拦截请求数据包 更改后缀名末尾处 添加“.” (这也是利用win系统的命名规则特性 “.”或空格即为空)
  2. 使用Burpsuite 拦截请求数据包 更改后缀名为.php. . （程序执行逻辑时 会执行两次移除字符串两侧的空白字符，但程序只执行一次，执行一次后留下的后缀名即为.php.）

以上两种方法仅适用于windows系统下 Linux系统不支持

防御方法

  1. 只执行一次trim函数 只清除一次空格
  2. 添加deldot函数 删除文件末尾的点
  3. 白名单防御方法

PASS 8）

$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！';
  }
}

源码分析

$file_name = trim($_FILES['upload_file']['name']);

$file_ext = trim($file_ext); //首尾去空
执行了两次首尾去空
没有对流文件::$DATA进行过滤

绕过方法

  1. 为文件后缀名添加::$DATA
  2. 改变后缀名格式 让程序执行逻辑时 对.和空格做一次移除操作 保留下来的即为可用执行文件

防御方法

  1. 只使用一次trim移除函数
  2. 限制过滤流文件::$DATA
  3. 限制上传文件格式（白名单防御方法）

PASS 9）

$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！';
  }
}

源码分析

$file_name = trim($_FILES['upload_file']['name']);

$file_ext = trim($file_ext); //首尾去空
执行了两次首尾去空

绕过方法

  1. 改变后缀名格式 让程序执行逻辑时 对.和空格做一次移除操作 保留下来的即为可用执行文件

  2. 即xx.php. . ---> xx.php.

防御方法

  1. 只使用一次trim移除函数
  2. 限制上传文件格式（白名单防御方法）

PASS 10）

$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！';
  }
}

源码分析

$file_name = str_ireplace($deny_ext,"", $file_name);

这里将上传的文件名中包含不允许的后缀名替换为空 得到$file_name
如果上传的文件名中一旦包含php asp jsp 等字符都会被替换为空达到不能正常执行shell程序的作用

绕过方法

  1. 双写绕过 BP拦截更改后缀名为.pphphp

  2. 即xx.pphpphp --识别到php 替换为空-> xx.php

防御方法

  1. 使用完整的黑名单过滤方法 过滤点、空格、大小写、流文件、htaccess分布式配置文件
  2. 使用白名单防御方法 只允许 想要进入的文件格式

⭐PASS1-10 总结过滤后缀名

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'];//获取文件名
    $file_name = deldot($file_name);//删除文件名末尾的点 【没有利用在后缀名添加.】
    $file_ext = strrchr($file_name, '.');//获取后缀名    
    $file_ext = strtolower($file_ext); //转换为小写    【没有利用 大小写绕过】
    $file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA 【没有利用在后缀名添加::4DATA】
     $file_ext = trim($file_ext); //首尾去空【没有利用在后缀名添加空格】

PASS 11）

$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！";
  }
}

源码分析

$img_path = $_GET['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;

通过get传入的参数 拼接至url中

绕过方法

  1. GET %00截断（通过burpsuite 实现）

image.png

防御方法

1.验证图片文件真实性

2.不使用请求方式接收参数方式 将其拼接至url

PASS 12）

$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！";
  }
}

源码分析

$img_path = $_POST['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;

通过POST传入的参数 拼接至url中

绕过方法

  1. POST 00截断（通过burpsuite 实现）

image.png

防御方法

1.验证图片文件真实性

2.不使用请求方式接收参数方式 将其拼接至url

PASS 13）

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！";
    }
  }
}

源码分析

通过观察源码

  1. 可知文件被打开时被验证了文件头2个字节（16位）

  2. 使用 switch……case……语句判断文件头16位编号 以验证图片文件的真实性

  3. 常用文件的文件头如下(16进制)：

jpg文件头：FFD8FFE0或FFD8FFE1或FFD8FFE8

gif文件头：47494638PNG
png文件头：89504E47

绕过方法

使用文件包含漏洞解析制作的图片马中包含的php执行的webshell语句

图片马制作方法：
copy 1.png/b + 2.php/a 3.png
以二进制bin打开1.png（真实图片） 用ascii编码打开2.php（webshell.php）
把两者相加，获得3.png

防御方法

防御其他漏洞

PASS 14）

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！";
        }
    }
}

源码分析

$info = getimagesize($filename); //获取图片的真实大小和信息

image_type_to_extension（$info[2]） //获取文件的文件头

验证文件的真实类型

如果传入的不是图片就会报错

绕过方法

  1. 使用图片马+文件包含漏洞

防御方法

PASS 15）

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！";
    }
  }
}

源码分析

exif_imagetype（） //获取图像信息和图像类型

验证真实文件类型
如果传入的不是真实图片就会报错

绕过方法

  1. 图片马+文件包含漏洞组合拳

防御方法

PASS 16）

$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！";
    }
}

源码分析

imagecreatefromjpeg() 二次渲染图片 将上传的图片渲染生成新的图片 压缩处理渲染处理，导致用户上传的图片马被改变，无法使用

（类似微信朋友圈会对图片进行压缩）
在压缩的时候执行半压缩 只执行了压缩清晰图
微信QQ微博是全压缩

--》low imagecreatefromjpeg

--》high 谷歌的图像压缩算法

绕过方法

  1. 上传图片马
  2. 下载图片马链接

https://wwe.lanzoui.com/iFSwwn53jaf

使用特殊的gif，找到在渲染前后不会改变的文件位置，使用webshell链接

防御方法

PASS 17）

$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！';
  }
}

源码分析

strrpos（）获取字符串最后一个位置

_substr_函数在oracle中使用表示被截取的字符串或字符串表达式

  1. 取出文件得后缀名1.png

$file_ext = substr($file_name,strrpos($file_name,".")+1);

  1. 上传文件 1.png 传到 upload/1.png

$upload_file = UPLOAD_PATH . '/' . $file_name;

  1. if(in_array($file_ext,$ext_arr))

判断后缀名

4.$img_path = UPLOAD_PATH . '/'. rand(10, 99).date("YmdHis").".".$file_ext;
如果是'jpg','png','gif' 文件则上传成功 反之则unlink删除文件

总结上传原理：

条件竞争漏洞
因为PASS17 是先上传再判断，所以加快上传速度和访问速度，进行竞争访问，如果竞争访问速度快过php删除的速度，即可完成漏洞利用

绕过方法

  1. BP爆破 空爆破

image.png

image.png

使用burpsuite爆破模块 高速 上传 webshell.php

使用burpsuite爆破模块 快速 访问 webshell.php

webshell玩法

  1. 执行单一命令 利用漏洞在路径中生成新的webshell
<?php
    file_put_contents('a.php','eval($_REQUEST['kio'])',LOCK_EX);
  ?>
  1. 执行单一命令 利用漏洞在路径中执行命令
<?php system('whoami'); ?>

防御方法

PASS 18）

//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" );
    
  }
  ......
    ......
    ...... 
};

源码分析

对文件先上传再重命名

如果上传速度过快 php可能反应不过来

绕过方法

利用条件竞争漏洞批量上传文件

防御方法

PASS 19）

$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！';
  }
}

源码分析

CVE-2015-2348 00截断

image.png

绕过方法

使用00截断方法

防御方法

PASS 20）

$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！";
}

源码分析

待我得空了回来填空

绕过方法

防御方法

总结防御方法（不考虑文件包含的存在）：

  1. 对象存储服务器

（将用户上传的文件，放置专用的服务器，和网站本身服务器没有任何关系 大厂常用方法）

  1. 检测content-type （如果是上传图片 检测是否为image/png;image/jpg;image/png）
  2. 检测后缀名 (合规的后缀名检测是无法绕过的)
  3. 二次渲染 （对上传的图片进行压缩或处理 合规的渲染可以防御）
  4. 内容检测 （获取文件信息，判断目标不是允许的文件时会直接报错）
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