upload-labs(17-20)

2023-12-19 12:45:33

17 条件竞争上传

黑盒测试

招数都用了,上传失败,看看提示:

源码分析

$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！';
    }
}

白名单上传,获取文件扩展名
先将临时文件上传到路径
判断扩展名是否在白名单,如果不在就删除上传的临时文件
如果在白名单,就重命名上传的临时文件名

看完源码,难道条件竞争上传?

白盒测试

条件竞争怎麽实现呢?

就是不断上传,把后端给累死,后端就会疏忽,然后上传成功

首先BP拦截数据包

然后发去爆破

整个脚本,输出1-99998作为字典

filename = '123.txt'
with open(filename, 'w') as file_object:
    for i in range(1,99999):
        a=str(i)
        file_object.write(a+'\n')

在此处攻击

可以看到上传目录1.php在忽隐忽现

可以连接

但是一直删,导致连接不稳定

字典跑完了,1.php最后又被删光了,连接就又断开了

把一句话改成phpinfo()显示信息也不错

18 竞争上传,apache解析漏洞

代码审计

源码分析

//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" );

......
......
......  

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

myupload.php

<?php

class MyUpload{    

  var $cls_upload_dir = "";         // Directory to upload to.
	var $cls_filename = "";           // Name of the upload file.
	var $cls_tmp_filename = "";       // TMP file Name (tmp name by php).
  var $cls_max_filesize = 33554432; // Max file size.
  var $cls_filesize ="";            // Actual file size.
  var $cls_arr_ext_accepted = array(
      ".doc", ".xls", ".txt", ".pdf", ".gif", ".jpg", ".zip", ".rar", ".7z",".ppt",
      ".html", ".xml", ".tiff", ".jpeg", ".png" );
  var $cls_file_exists = 0;         // Set to 1 to check if file exist before upload.
  var $cls_rename_file = 1;         // Set to 1 to rename file after upload.
  var $cls_file_rename_to = '';     // New name for the file after upload.
  var $cls_verbal = 0;              // Set to 1 to return an a string instead of an error code.

  function MyUpload( $file_name, $tmp_file_name, $file_size, $file_rename_to = '' ){
  
    $this->cls_filename = $file_name;
    $this->cls_tmp_filename = $tmp_file_name;
    $this->cls_filesize = $file_size;
    $this->cls_file_rename_to = $file_rename_to;
  }

  function isUploadedFile(){
    
    if( is_uploaded_file( $this->cls_tmp_filename ) != true ){
      return "IS_UPLOADED_FILE_FAILURE";
    } else {
      return 1;
    }
  }

  function setDir( $dir ){
    
    if( !is_writable( $dir ) ){
      return "DIRECTORY_FAILURE";
    } else { 
      $this->cls_upload_dir = $dir;
      return 1;
    }
  }


  function checkExtension(){
    
    // Check if the extension is valid

    if( !in_array( strtolower( strrchr( $this->cls_filename, "." )), $this->cls_arr_ext_accepted )){
      return "EXTENSION_FAILURE";
    } else {
      return 1;
    }
  }


  function checkSize(){

    if( $this->cls_filesize > $this->cls_max_filesize ){
      return "FILE_SIZE_FAILURE";
    } else {
      return 1;
    }
  }


  function move(){
    
    if( move_uploaded_file( $this->cls_tmp_filename, $this->cls_upload_dir . $this->cls_filename ) == false ){
      return "MOVE_UPLOADED_FILE_FAILURE";
    } else {
      return 1;
    }

  }


  function checkFileExists(){
    
    if( file_exists( $this->cls_upload_dir . $this->cls_filename ) ){
      return "FILE_EXISTS_FAILURE";
    } else {
      return 1;
    }
  }


  function renameFile(){

    // if no new name was provided, we use

    if( $this->cls_file_rename_to == '' ){

      $allchar = "abcdefghijklnmopqrstuvwxyz" ; 
      $this->cls_file_rename_to = "" ; 
      mt_srand (( double) microtime() * 1000000 ); 
      for ( $i = 0; $i<8 ; $i++ ){
        $this->cls_file_rename_to .= substr( $allchar, mt_rand (0,25), 1 ) ; 
      }
    }    
    
    // Remove the extension and put it back on the new file name
		
    $extension = strrchr( $this->cls_filename, "." );
    $this->cls_file_rename_to .= $extension;
    
    if( !rename( $this->cls_upload_dir . $this->cls_filename, $this->cls_upload_dir . $this->cls_file_rename_to )){
      return "RENAME_FAILURE";
    } else {
      return 1;
    }
  }
  
  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" );
  
  }

  function resultUpload( $flag ){

    switch( $flag ){
      case "IS_UPLOADED_FILE_FAILURE" : if( $this->cls_verbal == 0 ) return -1; else return "The file could not be uploaded to the tmp directory of the web server.";
        break;
      case "DIRECTORY_FAILURE"        : if( $this->cls_verbal == 0 ) return -2; else return "The file could not be uploaded, the directory is not writable.";
        break;
      case "EXTENSION_FAILURE"        : if( $this->cls_verbal == 0 ) return -3; else return "The file could not be uploaded, this type of file is not accepted.";
        break;
      case "FILE_SIZE_FAILURE"        : if( $this->cls_verbal == 0 ) return -4; else return "The file could not be uploaded, this file is too big.";
        break;
      case "FILE_EXISTS_FAILURE"      : if( $this->cls_verbal == 0 ) return -5; else return "The file could not be uploaded, a file with the same name already exists.";
        break;
      case "MOVE_UPLOADED_FILE_FAILURE" : if( $this->cls_verbal == 0 ) return -6; else return "The file could not be uploaded, the file could not be copied to destination directory.";
        break;
      case "RENAME_FAILURE"           : if( $this->cls_verbal == 0 ) return 2; else return "The file was uploaded but could not be renamed.";
        break;
      case "SUCCESS"                  : if( $this->cls_verbal == 0 ) return 1; else return "Upload was successful!";
        break;
      default : echo "OUPS!! We do not know what happen, you should fire the programmer ;)";
        break;
    }
  }

}; // end class
?>

可以看到代码中是先检查扩展,再上传,利用条件竞争上传

然后移动文件,最后改名

白盒测试

改成1.php.rar,利用apache解析漏洞上传

可以看到1.php.rar上传成功,没有改名

但是apache好像能解析rar

改成1.php.7z试试,成功解析

19 截断,windows特性-黑名单

黑盒测试

上传1.php

保存名称改为upload-19.php空格

就上传成功了

访问成功

没明白这道题想要干什么,看看提示,难道它不是想让用这种方法?

源码分析

$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！';
    }
}

1.POST过来的名字作为$file_name

2.用 pathinfo函数获取$file_name的扩展名$file-ext

3.如果扩展名不在黑名单中,就上传文件

简单的说,就是根据提交的savename进行判断,只要savename的扩展名不再黑名单,就行了

因此利用windows系统特性进行绕过

upload-labs pass-5-利用系统特性绕过 - AlucardLink - 博客园 (cnblogs.com)

搜了一下,看到还有人说利用%00截断?

源码中move_uploaded_file($temp_file, $img_path)来上传文件
而 $img_path = UPLOAD_PATH . '/' .$file_name;
利用$file_name,命名成例如1.php%00.jpg,然后上传时就截断了
注意post上传时,需要手动把%00url解码

上传后文件命名为了upload-119.php%EF%BF%BD.jpg,但是由于截断,实际上文件是upload-119.php

进行访问,截断成功

20 代码审计绕过

代码审计

源码分析

$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！";
}

1.Content-Type来判断文件是否在白名单,如果不在,禁止上传

2.如果post过来的save_name为空,就上传的文件名赋值给$file作为文件名,否则save_name赋值给$file

3.如果$file不是数组,就用explode() 函数将.作为分割线,分为数组,并全部转小写

4.将$file数组的最后一个值作为扩展名赋值给$ext

5.如果$ext不在白名单就禁止上传

6.reset()获取$file数组的第一个值,和$file数组的最后一个值用.连接,赋值给$file_name

7.文件上传到UPLOAD_PATH/$file_name

关键部分在于判断$file是不是数组,不是数组就被拆分的七零八落,导致无法绕过

如果是数组,我们自定义数组内容,绕过就轻而易举了

白盒测试

1.修改content-type绕过$_FILE[][type]检测

2.将save_name改为数组,只有0和4

3.save_name[0]为1.php,便于后面拼接

4.save_name[4]为jpg

1.为了过end($file)的白名单检测
2.count计算为2,但是save_name[1]不存在,因此$file[count($file) - 1]为空

5.拼接后为1.php.,由于windows特性,变成了保存后变成了1.php

连接成功

码农公寓

17 条件竞争上传

黑盒测试

源码分析

白盒测试

18 竞争上传,apache解析漏洞

源码分析

白盒测试

19 截断,windows特性-黑名单

黑盒测试

源码分析

20 代码审计绕过

源码分析

白盒测试

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